1 /* -----------------------------------------------------------------------------
3 * (c) The GHC Team 1998-2003
5 * Generational garbage collector
7 * ---------------------------------------------------------------------------*/
9 #include "PosixSource.h"
14 #include "OSThreads.h"
16 #include "LdvProfile.h"
21 #include "BlockAlloc.h"
27 #include "ParTicky.h" // ToDo: move into Rts.h
28 #include "GCCompact.h"
29 #include "RtsSignals.h"
31 #if defined(GRAN) || defined(PAR)
32 # include "GranSimRts.h"
33 # include "ParallelRts.h"
37 # include "ParallelDebug.h"
42 #if defined(RTS_GTK_FRONTPANEL)
43 #include "FrontPanel.h"
46 #include "RetainerProfile.h"
50 // Turn off inlining when debugging - it obfuscates things
53 # define STATIC_INLINE static
56 /* STATIC OBJECT LIST.
59 * We maintain a linked list of static objects that are still live.
60 * The requirements for this list are:
62 * - we need to scan the list while adding to it, in order to
63 * scavenge all the static objects (in the same way that
64 * breadth-first scavenging works for dynamic objects).
66 * - we need to be able to tell whether an object is already on
67 * the list, to break loops.
69 * Each static object has a "static link field", which we use for
70 * linking objects on to the list. We use a stack-type list, consing
71 * objects on the front as they are added (this means that the
72 * scavenge phase is depth-first, not breadth-first, but that
75 * A separate list is kept for objects that have been scavenged
76 * already - this is so that we can zero all the marks afterwards.
78 * An object is on the list if its static link field is non-zero; this
79 * means that we have to mark the end of the list with '1', not NULL.
81 * Extra notes for generational GC:
83 * Each generation has a static object list associated with it. When
84 * collecting generations up to N, we treat the static object lists
85 * from generations > N as roots.
87 * We build up a static object list while collecting generations 0..N,
88 * which is then appended to the static object list of generation N+1.
90 static StgClosure* static_objects; // live static objects
91 StgClosure* scavenged_static_objects; // static objects scavenged so far
93 /* N is the oldest generation being collected, where the generations
94 * are numbered starting at 0. A major GC (indicated by the major_gc
95 * flag) is when we're collecting all generations. We only attempt to
96 * deal with static objects and GC CAFs when doing a major GC.
99 static rtsBool major_gc;
101 /* Youngest generation that objects should be evacuated to in
102 * evacuate(). (Logically an argument to evacuate, but it's static
103 * a lot of the time so we optimise it into a global variable).
107 /* Whether to do eager promotion or not.
109 static rtsBool eager_promotion;
113 StgWeak *old_weak_ptr_list; // also pending finaliser list
115 /* Which stage of processing various kinds of weak pointer are we at?
116 * (see traverse_weak_ptr_list() below for discussion).
118 typedef enum { WeakPtrs, WeakThreads, WeakDone } WeakStage;
119 static WeakStage weak_stage;
121 /* List of all threads during GC
123 static StgTSO *old_all_threads;
124 StgTSO *resurrected_threads;
126 /* Flag indicating failure to evacuate an object to the desired
129 static rtsBool failed_to_evac;
131 /* Saved nursery (used for 2-space collector only)
133 static bdescr *saved_nursery;
134 static nat saved_n_blocks;
136 /* Data used for allocation area sizing.
138 static lnat new_blocks; // blocks allocated during this GC
139 static lnat new_scavd_blocks; // ditto, but depth-first blocks
140 static lnat g0s0_pcnt_kept = 30; // percentage of g0s0 live at last minor GC
142 /* Used to avoid long recursion due to selector thunks
144 static lnat thunk_selector_depth = 0;
145 #define MAX_THUNK_SELECTOR_DEPTH 8
155 /* -----------------------------------------------------------------------------
156 Static function declarations
157 -------------------------------------------------------------------------- */
159 static bdescr * gc_alloc_block ( step *stp );
160 static void mark_root ( StgClosure **root );
162 // Use a register argument for evacuate, if available.
164 #define REGPARM1 __attribute__((regparm(1)))
169 REGPARM1 static StgClosure * evacuate (StgClosure *q);
171 static void zero_static_object_list ( StgClosure* first_static );
173 static rtsBool traverse_weak_ptr_list ( void );
174 static void mark_weak_ptr_list ( StgWeak **list );
176 static StgClosure * eval_thunk_selector ( nat field, StgSelector * p );
179 static void scavenge ( step * );
180 static void scavenge_mark_stack ( void );
181 static void scavenge_stack ( StgPtr p, StgPtr stack_end );
182 static rtsBool scavenge_one ( StgPtr p );
183 static void scavenge_large ( step * );
184 static void scavenge_static ( void );
185 static void scavenge_mutable_list ( generation *g );
187 static void scavenge_large_bitmap ( StgPtr p,
188 StgLargeBitmap *large_bitmap,
191 #if 0 && defined(DEBUG)
192 static void gcCAFs ( void );
195 /* -----------------------------------------------------------------------------
196 inline functions etc. for dealing with the mark bitmap & stack.
197 -------------------------------------------------------------------------- */
199 #define MARK_STACK_BLOCKS 4
201 static bdescr *mark_stack_bdescr;
202 static StgPtr *mark_stack;
203 static StgPtr *mark_sp;
204 static StgPtr *mark_splim;
206 // Flag and pointers used for falling back to a linear scan when the
207 // mark stack overflows.
208 static rtsBool mark_stack_overflowed;
209 static bdescr *oldgen_scan_bd;
210 static StgPtr oldgen_scan;
212 STATIC_INLINE rtsBool
213 mark_stack_empty(void)
215 return mark_sp == mark_stack;
218 STATIC_INLINE rtsBool
219 mark_stack_full(void)
221 return mark_sp >= mark_splim;
225 reset_mark_stack(void)
227 mark_sp = mark_stack;
231 push_mark_stack(StgPtr p)
242 /* -----------------------------------------------------------------------------
243 Allocate a new to-space block in the given step.
244 -------------------------------------------------------------------------- */
247 gc_alloc_block(step *stp)
249 bdescr *bd = allocBlock();
250 bd->gen_no = stp->gen_no;
254 // blocks in to-space in generations up to and including N
255 // get the BF_EVACUATED flag.
256 if (stp->gen_no <= N) {
257 bd->flags = BF_EVACUATED;
262 // Start a new to-space block, chain it on after the previous one.
263 if (stp->hp_bd != NULL) {
264 stp->hp_bd->free = stp->hp;
265 stp->hp_bd->link = bd;
270 stp->hpLim = stp->hp + BLOCK_SIZE_W;
279 gc_alloc_scavd_block(step *stp)
281 bdescr *bd = allocBlock();
282 bd->gen_no = stp->gen_no;
285 // blocks in to-space in generations up to and including N
286 // get the BF_EVACUATED flag.
287 if (stp->gen_no <= N) {
288 bd->flags = BF_EVACUATED;
293 bd->link = stp->blocks;
296 if (stp->scavd_hp != NULL) {
297 Bdescr(stp->scavd_hp)->free = stp->scavd_hp;
299 stp->scavd_hp = bd->start;
300 stp->scavd_hpLim = stp->scavd_hp + BLOCK_SIZE_W;
308 /* -----------------------------------------------------------------------------
311 Rough outline of the algorithm: for garbage collecting generation N
312 (and all younger generations):
314 - follow all pointers in the root set. the root set includes all
315 mutable objects in all generations (mutable_list).
317 - for each pointer, evacuate the object it points to into either
319 + to-space of the step given by step->to, which is the next
320 highest step in this generation or the first step in the next
321 generation if this is the last step.
323 + to-space of generations[evac_gen]->steps[0], if evac_gen != 0.
324 When we evacuate an object we attempt to evacuate
325 everything it points to into the same generation - this is
326 achieved by setting evac_gen to the desired generation. If
327 we can't do this, then an entry in the mut list has to
328 be made for the cross-generation pointer.
330 + if the object is already in a generation > N, then leave
333 - repeatedly scavenge to-space from each step in each generation
334 being collected until no more objects can be evacuated.
336 - free from-space in each step, and set from-space = to-space.
338 Locks held: all capabilities are held throughout GarbageCollect().
340 -------------------------------------------------------------------------- */
343 GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc )
347 lnat live, allocated, copied = 0, scavd_copied = 0;
348 lnat oldgen_saved_blocks = 0;
354 CostCentreStack *prev_CCS;
357 #if defined(DEBUG) && defined(GRAN)
358 IF_DEBUG(gc, debugBelch("@@ Starting garbage collection at %ld (%lx)\n",
362 #if defined(RTS_USER_SIGNALS)
367 // tell the STM to discard any cached closures its hoping to re-use
370 // tell the stats department that we've started a GC
374 // check for memory leaks if DEBUG is on
384 // Init stats and print par specific (timing) info
385 PAR_TICKY_PAR_START();
387 // attribute any costs to CCS_GC
393 /* Approximate how much we allocated.
394 * Todo: only when generating stats?
396 allocated = calcAllocated();
398 /* Figure out which generation to collect
400 if (force_major_gc) {
401 N = RtsFlags.GcFlags.generations - 1;
405 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
406 if (generations[g].steps[0].n_blocks +
407 generations[g].steps[0].n_large_blocks
408 >= generations[g].max_blocks) {
412 major_gc = (N == RtsFlags.GcFlags.generations-1);
415 #ifdef RTS_GTK_FRONTPANEL
416 if (RtsFlags.GcFlags.frontpanel) {
417 updateFrontPanelBeforeGC(N);
421 // check stack sanity *before* GC (ToDo: check all threads)
423 // ToDo!: check sanity IF_DEBUG(sanity, checkTSOsSanity());
425 IF_DEBUG(sanity, checkFreeListSanity());
427 /* Initialise the static object lists
429 static_objects = END_OF_STATIC_LIST;
430 scavenged_static_objects = END_OF_STATIC_LIST;
432 /* Save the nursery if we're doing a two-space collection.
433 * g0s0->blocks will be used for to-space, so we need to get the
434 * nursery out of the way.
436 if (RtsFlags.GcFlags.generations == 1) {
437 saved_nursery = g0s0->blocks;
438 saved_n_blocks = g0s0->n_blocks;
443 /* Keep a count of how many new blocks we allocated during this GC
444 * (used for resizing the allocation area, later).
447 new_scavd_blocks = 0;
449 // Initialise to-space in all the generations/steps that we're
452 for (g = 0; g <= N; g++) {
454 // throw away the mutable list. Invariant: the mutable list
455 // always has at least one block; this means we can avoid a check for
456 // NULL in recordMutable().
458 freeChain(generations[g].mut_list);
459 generations[g].mut_list = allocBlock();
460 for (i = 0; i < n_capabilities; i++) {
461 freeChain(capabilities[i].mut_lists[g]);
462 capabilities[i].mut_lists[g] = allocBlock();
466 for (s = 0; s < generations[g].n_steps; s++) {
468 // generation 0, step 0 doesn't need to-space
469 if (g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1) {
473 stp = &generations[g].steps[s];
474 ASSERT(stp->gen_no == g);
476 // start a new to-space for this step.
477 stp->old_blocks = stp->blocks;
478 stp->n_old_blocks = stp->n_blocks;
480 // allocate the first to-space block; extra blocks will be
481 // chained on as necessary.
483 bd = gc_alloc_block(stp);
486 stp->scan = bd->start;
489 // allocate a block for "already scavenged" objects. This goes
490 // on the front of the stp->blocks list, so it won't be
491 // traversed by the scavenging sweep.
492 gc_alloc_scavd_block(stp);
494 // initialise the large object queues.
495 stp->new_large_objects = NULL;
496 stp->scavenged_large_objects = NULL;
497 stp->n_scavenged_large_blocks = 0;
499 // mark the large objects as not evacuated yet
500 for (bd = stp->large_objects; bd; bd = bd->link) {
501 bd->flags &= ~BF_EVACUATED;
504 // for a compacted step, we need to allocate the bitmap
505 if (stp->is_compacted) {
506 nat bitmap_size; // in bytes
507 bdescr *bitmap_bdescr;
510 bitmap_size = stp->n_old_blocks * BLOCK_SIZE / (sizeof(W_)*BITS_PER_BYTE);
512 if (bitmap_size > 0) {
513 bitmap_bdescr = allocGroup((lnat)BLOCK_ROUND_UP(bitmap_size)
515 stp->bitmap = bitmap_bdescr;
516 bitmap = bitmap_bdescr->start;
518 IF_DEBUG(gc, debugBelch("bitmap_size: %d, bitmap: %p",
519 bitmap_size, bitmap););
521 // don't forget to fill it with zeros!
522 memset(bitmap, 0, bitmap_size);
524 // For each block in this step, point to its bitmap from the
526 for (bd=stp->old_blocks; bd != NULL; bd = bd->link) {
527 bd->u.bitmap = bitmap;
528 bitmap += BLOCK_SIZE_W / (sizeof(W_)*BITS_PER_BYTE);
530 // Also at this point we set the BF_COMPACTED flag
531 // for this block. The invariant is that
532 // BF_COMPACTED is always unset, except during GC
533 // when it is set on those blocks which will be
535 bd->flags |= BF_COMPACTED;
542 /* make sure the older generations have at least one block to
543 * allocate into (this makes things easier for copy(), see below).
545 for (g = N+1; g < RtsFlags.GcFlags.generations; g++) {
546 for (s = 0; s < generations[g].n_steps; s++) {
547 stp = &generations[g].steps[s];
548 if (stp->hp_bd == NULL) {
549 ASSERT(stp->blocks == NULL);
550 bd = gc_alloc_block(stp);
554 if (stp->scavd_hp == NULL) {
555 gc_alloc_scavd_block(stp);
558 /* Set the scan pointer for older generations: remember we
559 * still have to scavenge objects that have been promoted. */
561 stp->scan_bd = stp->hp_bd;
562 stp->new_large_objects = NULL;
563 stp->scavenged_large_objects = NULL;
564 stp->n_scavenged_large_blocks = 0;
567 /* Move the private mutable lists from each capability onto the
568 * main mutable list for the generation.
570 for (i = 0; i < n_capabilities; i++) {
571 for (bd = capabilities[i].mut_lists[g];
572 bd->link != NULL; bd = bd->link) {
575 bd->link = generations[g].mut_list;
576 generations[g].mut_list = capabilities[i].mut_lists[g];
577 capabilities[i].mut_lists[g] = allocBlock();
581 /* Allocate a mark stack if we're doing a major collection.
584 mark_stack_bdescr = allocGroup(MARK_STACK_BLOCKS);
585 mark_stack = (StgPtr *)mark_stack_bdescr->start;
586 mark_sp = mark_stack;
587 mark_splim = mark_stack + (MARK_STACK_BLOCKS * BLOCK_SIZE_W);
589 mark_stack_bdescr = NULL;
592 eager_promotion = rtsTrue; // for now
594 /* -----------------------------------------------------------------------
595 * follow all the roots that we know about:
596 * - mutable lists from each generation > N
597 * we want to *scavenge* these roots, not evacuate them: they're not
598 * going to move in this GC.
599 * Also: do them in reverse generation order. This is because we
600 * often want to promote objects that are pointed to by older
601 * generations early, so we don't have to repeatedly copy them.
602 * Doing the generations in reverse order ensures that we don't end
603 * up in the situation where we want to evac an object to gen 3 and
604 * it has already been evaced to gen 2.
608 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
609 generations[g].saved_mut_list = generations[g].mut_list;
610 generations[g].mut_list = allocBlock();
611 // mut_list always has at least one block.
614 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
615 IF_PAR_DEBUG(verbose, printMutableList(&generations[g]));
616 scavenge_mutable_list(&generations[g]);
618 for (st = generations[g].n_steps-1; st >= 0; st--) {
619 scavenge(&generations[g].steps[st]);
624 /* follow roots from the CAF list (used by GHCi)
629 /* follow all the roots that the application knows about.
632 get_roots(mark_root);
635 /* And don't forget to mark the TSO if we got here direct from
637 /* Not needed in a seq version?
639 CurrentTSO = (StgTSO *)MarkRoot((StgClosure *)CurrentTSO);
643 // Mark the entries in the GALA table of the parallel system
644 markLocalGAs(major_gc);
645 // Mark all entries on the list of pending fetches
646 markPendingFetches(major_gc);
649 /* Mark the weak pointer list, and prepare to detect dead weak
652 mark_weak_ptr_list(&weak_ptr_list);
653 old_weak_ptr_list = weak_ptr_list;
654 weak_ptr_list = NULL;
655 weak_stage = WeakPtrs;
657 /* The all_threads list is like the weak_ptr_list.
658 * See traverse_weak_ptr_list() for the details.
660 old_all_threads = all_threads;
661 all_threads = END_TSO_QUEUE;
662 resurrected_threads = END_TSO_QUEUE;
664 /* Mark the stable pointer table.
666 markStablePtrTable(mark_root);
668 /* -------------------------------------------------------------------------
669 * Repeatedly scavenge all the areas we know about until there's no
670 * more scavenging to be done.
677 // scavenge static objects
678 if (major_gc && static_objects != END_OF_STATIC_LIST) {
679 IF_DEBUG(sanity, checkStaticObjects(static_objects));
683 /* When scavenging the older generations: Objects may have been
684 * evacuated from generations <= N into older generations, and we
685 * need to scavenge these objects. We're going to try to ensure that
686 * any evacuations that occur move the objects into at least the
687 * same generation as the object being scavenged, otherwise we
688 * have to create new entries on the mutable list for the older
692 // scavenge each step in generations 0..maxgen
698 // scavenge objects in compacted generation
699 if (mark_stack_overflowed || oldgen_scan_bd != NULL ||
700 (mark_stack_bdescr != NULL && !mark_stack_empty())) {
701 scavenge_mark_stack();
705 for (gen = RtsFlags.GcFlags.generations; --gen >= 0; ) {
706 for (st = generations[gen].n_steps; --st >= 0; ) {
707 if (gen == 0 && st == 0 && RtsFlags.GcFlags.generations > 1) {
710 stp = &generations[gen].steps[st];
712 if (stp->hp_bd != stp->scan_bd || stp->scan < stp->hp) {
717 if (stp->new_large_objects != NULL) {
726 if (flag) { goto loop; }
728 // must be last... invariant is that everything is fully
729 // scavenged at this point.
730 if (traverse_weak_ptr_list()) { // returns rtsTrue if evaced something
735 /* Update the pointers from the task list - these are
736 * treated as weak pointers because we want to allow a main thread
737 * to get a BlockedOnDeadMVar exception in the same way as any other
738 * thread. Note that the threads should all have been retained by
739 * GC by virtue of being on the all_threads list, we're just
740 * updating pointers here.
745 for (task = all_tasks; task != NULL; task = task->all_link) {
746 if (!task->stopped && task->tso) {
747 ASSERT(task->tso->bound == task);
748 tso = (StgTSO *) isAlive((StgClosure *)task->tso);
750 barf("task %p: main thread %d has been GC'd",
764 // Reconstruct the Global Address tables used in GUM
765 rebuildGAtables(major_gc);
766 IF_DEBUG(sanity, checkLAGAtable(rtsTrue/*check closures, too*/));
769 // Now see which stable names are still alive.
772 // Tidy the end of the to-space chains
773 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
774 for (s = 0; s < generations[g].n_steps; s++) {
775 stp = &generations[g].steps[s];
776 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
777 ASSERT(Bdescr(stp->hp) == stp->hp_bd);
778 stp->hp_bd->free = stp->hp;
779 Bdescr(stp->scavd_hp)->free = stp->scavd_hp;
785 // We call processHeapClosureForDead() on every closure destroyed during
786 // the current garbage collection, so we invoke LdvCensusForDead().
787 if (RtsFlags.ProfFlags.doHeapProfile == HEAP_BY_LDV
788 || RtsFlags.ProfFlags.bioSelector != NULL)
792 // NO MORE EVACUATION AFTER THIS POINT!
793 // Finally: compaction of the oldest generation.
794 if (major_gc && oldest_gen->steps[0].is_compacted) {
795 // save number of blocks for stats
796 oldgen_saved_blocks = oldest_gen->steps[0].n_old_blocks;
800 IF_DEBUG(sanity, checkGlobalTSOList(rtsFalse));
802 /* run through all the generations/steps and tidy up
804 copied = new_blocks * BLOCK_SIZE_W;
805 scavd_copied = new_scavd_blocks * BLOCK_SIZE_W;
806 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
809 generations[g].collections++; // for stats
812 // Count the mutable list as bytes "copied" for the purposes of
813 // stats. Every mutable list is copied during every GC.
815 nat mut_list_size = 0;
816 for (bd = generations[g].mut_list; bd != NULL; bd = bd->link) {
817 mut_list_size += bd->free - bd->start;
819 copied += mut_list_size;
821 IF_DEBUG(gc, debugBelch("mut_list_size: %d (%d vars, %d arrays, %d others)\n", mut_list_size * sizeof(W_), mutlist_MUTVARS, mutlist_MUTARRS, mutlist_OTHERS));
824 for (s = 0; s < generations[g].n_steps; s++) {
826 stp = &generations[g].steps[s];
828 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
829 // stats information: how much we copied
831 copied -= stp->hp_bd->start + BLOCK_SIZE_W -
833 scavd_copied -= (P_)(BLOCK_ROUND_UP(stp->scavd_hp)) - stp->scavd_hp;
837 // for generations we collected...
840 /* free old memory and shift to-space into from-space for all
841 * the collected steps (except the allocation area). These
842 * freed blocks will probaby be quickly recycled.
844 if (!(g == 0 && s == 0)) {
845 if (stp->is_compacted) {
846 // for a compacted step, just shift the new to-space
847 // onto the front of the now-compacted existing blocks.
848 for (bd = stp->blocks; bd != NULL; bd = bd->link) {
849 bd->flags &= ~BF_EVACUATED; // now from-space
851 // tack the new blocks on the end of the existing blocks
852 if (stp->old_blocks != NULL) {
853 for (bd = stp->old_blocks; bd != NULL; bd = next) {
854 // NB. this step might not be compacted next
855 // time, so reset the BF_COMPACTED flags.
856 // They are set before GC if we're going to
857 // compact. (search for BF_COMPACTED above).
858 bd->flags &= ~BF_COMPACTED;
861 bd->link = stp->blocks;
864 stp->blocks = stp->old_blocks;
866 // add the new blocks to the block tally
867 stp->n_blocks += stp->n_old_blocks;
868 ASSERT(countBlocks(stp->blocks) == stp->n_blocks);
870 freeChain(stp->old_blocks);
871 for (bd = stp->blocks; bd != NULL; bd = bd->link) {
872 bd->flags &= ~BF_EVACUATED; // now from-space
875 stp->old_blocks = NULL;
876 stp->n_old_blocks = 0;
879 /* LARGE OBJECTS. The current live large objects are chained on
880 * scavenged_large, having been moved during garbage
881 * collection from large_objects. Any objects left on
882 * large_objects list are therefore dead, so we free them here.
884 for (bd = stp->large_objects; bd != NULL; bd = next) {
890 // update the count of blocks used by large objects
891 for (bd = stp->scavenged_large_objects; bd != NULL; bd = bd->link) {
892 bd->flags &= ~BF_EVACUATED;
894 stp->large_objects = stp->scavenged_large_objects;
895 stp->n_large_blocks = stp->n_scavenged_large_blocks;
898 // for older generations...
900 /* For older generations, we need to append the
901 * scavenged_large_object list (i.e. large objects that have been
902 * promoted during this GC) to the large_object list for that step.
904 for (bd = stp->scavenged_large_objects; bd; bd = next) {
906 bd->flags &= ~BF_EVACUATED;
907 dbl_link_onto(bd, &stp->large_objects);
910 // add the new blocks we promoted during this GC
911 stp->n_large_blocks += stp->n_scavenged_large_blocks;
916 /* Reset the sizes of the older generations when we do a major
919 * CURRENT STRATEGY: make all generations except zero the same size.
920 * We have to stay within the maximum heap size, and leave a certain
921 * percentage of the maximum heap size available to allocate into.
923 if (major_gc && RtsFlags.GcFlags.generations > 1) {
924 nat live, size, min_alloc;
925 nat max = RtsFlags.GcFlags.maxHeapSize;
926 nat gens = RtsFlags.GcFlags.generations;
928 // live in the oldest generations
929 live = oldest_gen->steps[0].n_blocks +
930 oldest_gen->steps[0].n_large_blocks;
932 // default max size for all generations except zero
933 size = stg_max(live * RtsFlags.GcFlags.oldGenFactor,
934 RtsFlags.GcFlags.minOldGenSize);
936 // minimum size for generation zero
937 min_alloc = stg_max((RtsFlags.GcFlags.pcFreeHeap * max) / 200,
938 RtsFlags.GcFlags.minAllocAreaSize);
940 // Auto-enable compaction when the residency reaches a
941 // certain percentage of the maximum heap size (default: 30%).
942 if (RtsFlags.GcFlags.generations > 1 &&
943 (RtsFlags.GcFlags.compact ||
945 oldest_gen->steps[0].n_blocks >
946 (RtsFlags.GcFlags.compactThreshold * max) / 100))) {
947 oldest_gen->steps[0].is_compacted = 1;
948 // debugBelch("compaction: on\n", live);
950 oldest_gen->steps[0].is_compacted = 0;
951 // debugBelch("compaction: off\n", live);
954 // if we're going to go over the maximum heap size, reduce the
955 // size of the generations accordingly. The calculation is
956 // different if compaction is turned on, because we don't need
957 // to double the space required to collect the old generation.
960 // this test is necessary to ensure that the calculations
961 // below don't have any negative results - we're working
962 // with unsigned values here.
963 if (max < min_alloc) {
967 if (oldest_gen->steps[0].is_compacted) {
968 if ( (size + (size - 1) * (gens - 2) * 2) + min_alloc > max ) {
969 size = (max - min_alloc) / ((gens - 1) * 2 - 1);
972 if ( (size * (gens - 1) * 2) + min_alloc > max ) {
973 size = (max - min_alloc) / ((gens - 1) * 2);
983 debugBelch("live: %d, min_alloc: %d, size : %d, max = %d\n", live,
984 min_alloc, size, max);
987 for (g = 0; g < gens; g++) {
988 generations[g].max_blocks = size;
992 // Guess the amount of live data for stats.
995 /* Free the small objects allocated via allocate(), since this will
996 * all have been copied into G0S1 now.
998 if (small_alloc_list != NULL) {
999 freeChain(small_alloc_list);
1001 small_alloc_list = NULL;
1005 alloc_blocks_lim = RtsFlags.GcFlags.minAllocAreaSize;
1007 // Start a new pinned_object_block
1008 pinned_object_block = NULL;
1010 /* Free the mark stack.
1012 if (mark_stack_bdescr != NULL) {
1013 freeGroup(mark_stack_bdescr);
1016 /* Free any bitmaps.
1018 for (g = 0; g <= N; g++) {
1019 for (s = 0; s < generations[g].n_steps; s++) {
1020 stp = &generations[g].steps[s];
1021 if (stp->bitmap != NULL) {
1022 freeGroup(stp->bitmap);
1028 /* Two-space collector:
1029 * Free the old to-space, and estimate the amount of live data.
1031 if (RtsFlags.GcFlags.generations == 1) {
1034 if (g0s0->old_blocks != NULL) {
1035 freeChain(g0s0->old_blocks);
1037 for (bd = g0s0->blocks; bd != NULL; bd = bd->link) {
1038 bd->flags = 0; // now from-space
1040 g0s0->old_blocks = g0s0->blocks;
1041 g0s0->n_old_blocks = g0s0->n_blocks;
1042 g0s0->blocks = saved_nursery;
1043 g0s0->n_blocks = saved_n_blocks;
1045 /* For a two-space collector, we need to resize the nursery. */
1047 /* set up a new nursery. Allocate a nursery size based on a
1048 * function of the amount of live data (by default a factor of 2)
1049 * Use the blocks from the old nursery if possible, freeing up any
1052 * If we get near the maximum heap size, then adjust our nursery
1053 * size accordingly. If the nursery is the same size as the live
1054 * data (L), then we need 3L bytes. We can reduce the size of the
1055 * nursery to bring the required memory down near 2L bytes.
1057 * A normal 2-space collector would need 4L bytes to give the same
1058 * performance we get from 3L bytes, reducing to the same
1059 * performance at 2L bytes.
1061 blocks = g0s0->n_old_blocks;
1063 if ( RtsFlags.GcFlags.maxHeapSize != 0 &&
1064 blocks * RtsFlags.GcFlags.oldGenFactor * 2 >
1065 RtsFlags.GcFlags.maxHeapSize ) {
1066 long adjusted_blocks; // signed on purpose
1069 adjusted_blocks = (RtsFlags.GcFlags.maxHeapSize - 2 * blocks);
1070 IF_DEBUG(gc, debugBelch("@@ Near maximum heap size of 0x%x blocks, blocks = %d, adjusted to %ld", RtsFlags.GcFlags.maxHeapSize, blocks, adjusted_blocks));
1071 pc_free = adjusted_blocks * 100 / RtsFlags.GcFlags.maxHeapSize;
1072 if (pc_free < RtsFlags.GcFlags.pcFreeHeap) /* might even be < 0 */ {
1075 blocks = adjusted_blocks;
1078 blocks *= RtsFlags.GcFlags.oldGenFactor;
1079 if (blocks < RtsFlags.GcFlags.minAllocAreaSize) {
1080 blocks = RtsFlags.GcFlags.minAllocAreaSize;
1083 resizeNurseries(blocks);
1086 /* Generational collector:
1087 * If the user has given us a suggested heap size, adjust our
1088 * allocation area to make best use of the memory available.
1091 if (RtsFlags.GcFlags.heapSizeSuggestion) {
1093 nat needed = calcNeeded(); // approx blocks needed at next GC
1095 /* Guess how much will be live in generation 0 step 0 next time.
1096 * A good approximation is obtained by finding the
1097 * percentage of g0s0 that was live at the last minor GC.
1100 g0s0_pcnt_kept = (new_blocks * 100) / countNurseryBlocks();
1103 /* Estimate a size for the allocation area based on the
1104 * information available. We might end up going slightly under
1105 * or over the suggested heap size, but we should be pretty
1108 * Formula: suggested - needed
1109 * ----------------------------
1110 * 1 + g0s0_pcnt_kept/100
1112 * where 'needed' is the amount of memory needed at the next
1113 * collection for collecting all steps except g0s0.
1116 (((long)RtsFlags.GcFlags.heapSizeSuggestion - (long)needed) * 100) /
1117 (100 + (long)g0s0_pcnt_kept);
1119 if (blocks < (long)RtsFlags.GcFlags.minAllocAreaSize) {
1120 blocks = RtsFlags.GcFlags.minAllocAreaSize;
1123 resizeNurseries((nat)blocks);
1126 // we might have added extra large blocks to the nursery, so
1127 // resize back to minAllocAreaSize again.
1128 resizeNurseriesFixed(RtsFlags.GcFlags.minAllocAreaSize);
1132 // mark the garbage collected CAFs as dead
1133 #if 0 && defined(DEBUG) // doesn't work at the moment
1134 if (major_gc) { gcCAFs(); }
1138 // resetStaticObjectForRetainerProfiling() must be called before
1140 resetStaticObjectForRetainerProfiling();
1143 // zero the scavenged static object list
1145 zero_static_object_list(scavenged_static_objects);
1148 // Reset the nursery
1151 // start any pending finalizers
1153 scheduleFinalizers(last_free_capability, old_weak_ptr_list);
1156 // send exceptions to any threads which were about to die
1157 resurrectThreads(resurrected_threads);
1159 // Update the stable pointer hash table.
1160 updateStablePtrTable(major_gc);
1162 // check sanity after GC
1163 IF_DEBUG(sanity, checkSanity());
1165 // extra GC trace info
1166 IF_DEBUG(gc, statDescribeGens());
1169 // symbol-table based profiling
1170 /* heapCensus(to_blocks); */ /* ToDo */
1173 // restore enclosing cost centre
1179 // check for memory leaks if DEBUG is on
1183 #ifdef RTS_GTK_FRONTPANEL
1184 if (RtsFlags.GcFlags.frontpanel) {
1185 updateFrontPanelAfterGC( N, live );
1189 // ok, GC over: tell the stats department what happened.
1190 stat_endGC(allocated, live, copied, scavd_copied, N);
1192 #if defined(RTS_USER_SIGNALS)
1193 // unblock signals again
1194 unblockUserSignals();
1203 /* -----------------------------------------------------------------------------
1206 traverse_weak_ptr_list is called possibly many times during garbage
1207 collection. It returns a flag indicating whether it did any work
1208 (i.e. called evacuate on any live pointers).
1210 Invariant: traverse_weak_ptr_list is called when the heap is in an
1211 idempotent state. That means that there are no pending
1212 evacuate/scavenge operations. This invariant helps the weak
1213 pointer code decide which weak pointers are dead - if there are no
1214 new live weak pointers, then all the currently unreachable ones are
1217 For generational GC: we just don't try to finalize weak pointers in
1218 older generations than the one we're collecting. This could
1219 probably be optimised by keeping per-generation lists of weak
1220 pointers, but for a few weak pointers this scheme will work.
1222 There are three distinct stages to processing weak pointers:
1224 - weak_stage == WeakPtrs
1226 We process all the weak pointers whos keys are alive (evacuate
1227 their values and finalizers), and repeat until we can find no new
1228 live keys. If no live keys are found in this pass, then we
1229 evacuate the finalizers of all the dead weak pointers in order to
1232 - weak_stage == WeakThreads
1234 Now, we discover which *threads* are still alive. Pointers to
1235 threads from the all_threads and main thread lists are the
1236 weakest of all: a pointers from the finalizer of a dead weak
1237 pointer can keep a thread alive. Any threads found to be unreachable
1238 are evacuated and placed on the resurrected_threads list so we
1239 can send them a signal later.
1241 - weak_stage == WeakDone
1243 No more evacuation is done.
1245 -------------------------------------------------------------------------- */
1248 traverse_weak_ptr_list(void)
1250 StgWeak *w, **last_w, *next_w;
1252 rtsBool flag = rtsFalse;
1254 switch (weak_stage) {
1260 /* doesn't matter where we evacuate values/finalizers to, since
1261 * these pointers are treated as roots (iff the keys are alive).
1265 last_w = &old_weak_ptr_list;
1266 for (w = old_weak_ptr_list; w != NULL; w = next_w) {
1268 /* There might be a DEAD_WEAK on the list if finalizeWeak# was
1269 * called on a live weak pointer object. Just remove it.
1271 if (w->header.info == &stg_DEAD_WEAK_info) {
1272 next_w = ((StgDeadWeak *)w)->link;
1277 switch (get_itbl(w)->type) {
1280 next_w = (StgWeak *)((StgEvacuated *)w)->evacuee;
1285 /* Now, check whether the key is reachable.
1287 new = isAlive(w->key);
1290 // evacuate the value and finalizer
1291 w->value = evacuate(w->value);
1292 w->finalizer = evacuate(w->finalizer);
1293 // remove this weak ptr from the old_weak_ptr list
1295 // and put it on the new weak ptr list
1297 w->link = weak_ptr_list;
1300 IF_DEBUG(weak, debugBelch("Weak pointer still alive at %p -> %p",
1305 last_w = &(w->link);
1311 barf("traverse_weak_ptr_list: not WEAK");
1315 /* If we didn't make any changes, then we can go round and kill all
1316 * the dead weak pointers. The old_weak_ptr list is used as a list
1317 * of pending finalizers later on.
1319 if (flag == rtsFalse) {
1320 for (w = old_weak_ptr_list; w; w = w->link) {
1321 w->finalizer = evacuate(w->finalizer);
1324 // Next, move to the WeakThreads stage after fully
1325 // scavenging the finalizers we've just evacuated.
1326 weak_stage = WeakThreads;
1332 /* Now deal with the all_threads list, which behaves somewhat like
1333 * the weak ptr list. If we discover any threads that are about to
1334 * become garbage, we wake them up and administer an exception.
1337 StgTSO *t, *tmp, *next, **prev;
1339 prev = &old_all_threads;
1340 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1342 tmp = (StgTSO *)isAlive((StgClosure *)t);
1348 ASSERT(get_itbl(t)->type == TSO);
1349 switch (t->what_next) {
1350 case ThreadRelocated:
1355 case ThreadComplete:
1356 // finshed or died. The thread might still be alive, but we
1357 // don't keep it on the all_threads list. Don't forget to
1358 // stub out its global_link field.
1359 next = t->global_link;
1360 t->global_link = END_TSO_QUEUE;
1367 // Threads blocked on black holes: if the black hole
1368 // is alive, then the thread is alive too.
1369 if (tmp == NULL && t->why_blocked == BlockedOnBlackHole) {
1370 if (isAlive(t->block_info.closure)) {
1371 t = (StgTSO *)evacuate((StgClosure *)t);
1378 // not alive (yet): leave this thread on the
1379 // old_all_threads list.
1380 prev = &(t->global_link);
1381 next = t->global_link;
1384 // alive: move this thread onto the all_threads list.
1385 next = t->global_link;
1386 t->global_link = all_threads;
1393 /* If we evacuated any threads, we need to go back to the scavenger.
1395 if (flag) return rtsTrue;
1397 /* And resurrect any threads which were about to become garbage.
1400 StgTSO *t, *tmp, *next;
1401 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1402 next = t->global_link;
1403 tmp = (StgTSO *)evacuate((StgClosure *)t);
1404 tmp->global_link = resurrected_threads;
1405 resurrected_threads = tmp;
1409 /* Finally, we can update the blackhole_queue. This queue
1410 * simply strings together TSOs blocked on black holes, it is
1411 * not intended to keep anything alive. Hence, we do not follow
1412 * pointers on the blackhole_queue until now, when we have
1413 * determined which TSOs are otherwise reachable. We know at
1414 * this point that all TSOs have been evacuated, however.
1418 for (pt = &blackhole_queue; *pt != END_TSO_QUEUE; pt = &((*pt)->link)) {
1419 *pt = (StgTSO *)isAlive((StgClosure *)*pt);
1420 ASSERT(*pt != NULL);
1424 weak_stage = WeakDone; // *now* we're done,
1425 return rtsTrue; // but one more round of scavenging, please
1428 barf("traverse_weak_ptr_list");
1434 /* -----------------------------------------------------------------------------
1435 After GC, the live weak pointer list may have forwarding pointers
1436 on it, because a weak pointer object was evacuated after being
1437 moved to the live weak pointer list. We remove those forwarding
1440 Also, we don't consider weak pointer objects to be reachable, but
1441 we must nevertheless consider them to be "live" and retain them.
1442 Therefore any weak pointer objects which haven't as yet been
1443 evacuated need to be evacuated now.
1444 -------------------------------------------------------------------------- */
1448 mark_weak_ptr_list ( StgWeak **list )
1450 StgWeak *w, **last_w;
1453 for (w = *list; w; w = w->link) {
1454 // w might be WEAK, EVACUATED, or DEAD_WEAK (actually CON_STATIC) here
1455 ASSERT(w->header.info == &stg_DEAD_WEAK_info
1456 || get_itbl(w)->type == WEAK || get_itbl(w)->type == EVACUATED);
1457 w = (StgWeak *)evacuate((StgClosure *)w);
1459 last_w = &(w->link);
1463 /* -----------------------------------------------------------------------------
1464 isAlive determines whether the given closure is still alive (after
1465 a garbage collection) or not. It returns the new address of the
1466 closure if it is alive, or NULL otherwise.
1468 NOTE: Use it before compaction only!
1469 -------------------------------------------------------------------------- */
1473 isAlive(StgClosure *p)
1475 const StgInfoTable *info;
1480 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
1483 // ignore static closures
1485 // ToDo: for static closures, check the static link field.
1486 // Problem here is that we sometimes don't set the link field, eg.
1487 // for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
1489 if (!HEAP_ALLOCED(p)) {
1493 // ignore closures in generations that we're not collecting.
1495 if (bd->gen_no > N) {
1499 // if it's a pointer into to-space, then we're done
1500 if (bd->flags & BF_EVACUATED) {
1504 // large objects use the evacuated flag
1505 if (bd->flags & BF_LARGE) {
1509 // check the mark bit for compacted steps
1510 if ((bd->flags & BF_COMPACTED) && is_marked((P_)p,bd)) {
1514 switch (info->type) {
1519 case IND_OLDGEN: // rely on compatible layout with StgInd
1520 case IND_OLDGEN_PERM:
1521 // follow indirections
1522 p = ((StgInd *)p)->indirectee;
1527 return ((StgEvacuated *)p)->evacuee;
1530 if (((StgTSO *)p)->what_next == ThreadRelocated) {
1531 p = (StgClosure *)((StgTSO *)p)->link;
1544 mark_root(StgClosure **root)
1546 *root = evacuate(*root);
1550 upd_evacuee(StgClosure *p, StgClosure *dest)
1552 // not true: (ToDo: perhaps it should be)
1553 // ASSERT(Bdescr((P_)dest)->flags & BF_EVACUATED);
1554 SET_INFO(p, &stg_EVACUATED_info);
1555 ((StgEvacuated *)p)->evacuee = dest;
1559 STATIC_INLINE StgClosure *
1560 copy(StgClosure *src, nat size, step *stp)
1566 nat size_org = size;
1569 TICK_GC_WORDS_COPIED(size);
1570 /* Find out where we're going, using the handy "to" pointer in
1571 * the step of the source object. If it turns out we need to
1572 * evacuate to an older generation, adjust it here (see comment
1575 if (stp->gen_no < evac_gen) {
1576 if (eager_promotion) {
1577 stp = &generations[evac_gen].steps[0];
1579 failed_to_evac = rtsTrue;
1583 /* chain a new block onto the to-space for the destination step if
1586 if (stp->hp + size >= stp->hpLim) {
1587 gc_alloc_block(stp);
1592 stp->hp = to + size;
1593 for (i = 0; i < size; i++) { // unroll for small i
1596 upd_evacuee((StgClosure *)from,(StgClosure *)to);
1599 // We store the size of the just evacuated object in the LDV word so that
1600 // the profiler can guess the position of the next object later.
1601 SET_EVACUAEE_FOR_LDV(from, size_org);
1603 return (StgClosure *)to;
1606 // Same as copy() above, except the object will be allocated in memory
1607 // that will not be scavenged. Used for object that have no pointer
1609 STATIC_INLINE StgClosure *
1610 copy_noscav(StgClosure *src, nat size, step *stp)
1616 nat size_org = size;
1619 TICK_GC_WORDS_COPIED(size);
1620 /* Find out where we're going, using the handy "to" pointer in
1621 * the step of the source object. If it turns out we need to
1622 * evacuate to an older generation, adjust it here (see comment
1625 if (stp->gen_no < evac_gen) {
1626 if (eager_promotion) {
1627 stp = &generations[evac_gen].steps[0];
1629 failed_to_evac = rtsTrue;
1633 /* chain a new block onto the to-space for the destination step if
1636 if (stp->scavd_hp + size >= stp->scavd_hpLim) {
1637 gc_alloc_scavd_block(stp);
1642 stp->scavd_hp = to + size;
1643 for (i = 0; i < size; i++) { // unroll for small i
1646 upd_evacuee((StgClosure *)from,(StgClosure *)to);
1649 // We store the size of the just evacuated object in the LDV word so that
1650 // the profiler can guess the position of the next object later.
1651 SET_EVACUAEE_FOR_LDV(from, size_org);
1653 return (StgClosure *)to;
1656 /* Special version of copy() for when we only want to copy the info
1657 * pointer of an object, but reserve some padding after it. This is
1658 * used to optimise evacuation of BLACKHOLEs.
1663 copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *stp)
1668 nat size_to_copy_org = size_to_copy;
1671 TICK_GC_WORDS_COPIED(size_to_copy);
1672 if (stp->gen_no < evac_gen) {
1673 if (eager_promotion) {
1674 stp = &generations[evac_gen].steps[0];
1676 failed_to_evac = rtsTrue;
1680 if (stp->hp + size_to_reserve >= stp->hpLim) {
1681 gc_alloc_block(stp);
1684 for(to = stp->hp, from = (P_)src; size_to_copy>0; --size_to_copy) {
1689 stp->hp += size_to_reserve;
1690 upd_evacuee(src,(StgClosure *)dest);
1692 // We store the size of the just evacuated object in the LDV word so that
1693 // the profiler can guess the position of the next object later.
1694 // size_to_copy_org is wrong because the closure already occupies size_to_reserve
1696 SET_EVACUAEE_FOR_LDV(src, size_to_reserve);
1698 if (size_to_reserve - size_to_copy_org > 0)
1699 LDV_FILL_SLOP(stp->hp - 1, (int)(size_to_reserve - size_to_copy_org));
1701 return (StgClosure *)dest;
1705 /* -----------------------------------------------------------------------------
1706 Evacuate a large object
1708 This just consists of removing the object from the (doubly-linked)
1709 step->large_objects list, and linking it on to the (singly-linked)
1710 step->new_large_objects list, from where it will be scavenged later.
1712 Convention: bd->flags has BF_EVACUATED set for a large object
1713 that has been evacuated, or unset otherwise.
1714 -------------------------------------------------------------------------- */
1718 evacuate_large(StgPtr p)
1720 bdescr *bd = Bdescr(p);
1723 // object must be at the beginning of the block (or be a ByteArray)
1724 ASSERT(get_itbl((StgClosure *)p)->type == ARR_WORDS ||
1725 (((W_)p & BLOCK_MASK) == 0));
1727 // already evacuated?
1728 if (bd->flags & BF_EVACUATED) {
1729 /* Don't forget to set the failed_to_evac flag if we didn't get
1730 * the desired destination (see comments in evacuate()).
1732 if (bd->gen_no < evac_gen) {
1733 failed_to_evac = rtsTrue;
1734 TICK_GC_FAILED_PROMOTION();
1740 // remove from large_object list
1742 bd->u.back->link = bd->link;
1743 } else { // first object in the list
1744 stp->large_objects = bd->link;
1747 bd->link->u.back = bd->u.back;
1750 /* link it on to the evacuated large object list of the destination step
1753 if (stp->gen_no < evac_gen) {
1754 if (eager_promotion) {
1755 stp = &generations[evac_gen].steps[0];
1757 failed_to_evac = rtsTrue;
1762 bd->gen_no = stp->gen_no;
1763 bd->link = stp->new_large_objects;
1764 stp->new_large_objects = bd;
1765 bd->flags |= BF_EVACUATED;
1768 /* -----------------------------------------------------------------------------
1771 This is called (eventually) for every live object in the system.
1773 The caller to evacuate specifies a desired generation in the
1774 evac_gen global variable. The following conditions apply to
1775 evacuating an object which resides in generation M when we're
1776 collecting up to generation N
1780 else evac to step->to
1782 if M < evac_gen evac to evac_gen, step 0
1784 if the object is already evacuated, then we check which generation
1787 if M >= evac_gen do nothing
1788 if M < evac_gen set failed_to_evac flag to indicate that we
1789 didn't manage to evacuate this object into evac_gen.
1794 evacuate() is the single most important function performance-wise
1795 in the GC. Various things have been tried to speed it up, but as
1796 far as I can tell the code generated by gcc 3.2 with -O2 is about
1797 as good as it's going to get. We pass the argument to evacuate()
1798 in a register using the 'regparm' attribute (see the prototype for
1799 evacuate() near the top of this file).
1801 Changing evacuate() to take an (StgClosure **) rather than
1802 returning the new pointer seems attractive, because we can avoid
1803 writing back the pointer when it hasn't changed (eg. for a static
1804 object, or an object in a generation > N). However, I tried it and
1805 it doesn't help. One reason is that the (StgClosure **) pointer
1806 gets spilled to the stack inside evacuate(), resulting in far more
1807 extra reads/writes than we save.
1808 -------------------------------------------------------------------------- */
1810 REGPARM1 static StgClosure *
1811 evacuate(StgClosure *q)
1818 const StgInfoTable *info;
1821 ASSERT(LOOKS_LIKE_CLOSURE_PTR(q));
1823 if (!HEAP_ALLOCED(q)) {
1825 if (!major_gc) return q;
1828 switch (info->type) {
1831 if (info->srt_bitmap != 0 &&
1832 *THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
1833 *THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
1834 static_objects = (StgClosure *)q;
1839 if (info->srt_bitmap != 0 &&
1840 *FUN_STATIC_LINK((StgClosure *)q) == NULL) {
1841 *FUN_STATIC_LINK((StgClosure *)q) = static_objects;
1842 static_objects = (StgClosure *)q;
1847 /* If q->saved_info != NULL, then it's a revertible CAF - it'll be
1848 * on the CAF list, so don't do anything with it here (we'll
1849 * scavenge it later).
1851 if (((StgIndStatic *)q)->saved_info == NULL
1852 && *IND_STATIC_LINK((StgClosure *)q) == NULL) {
1853 *IND_STATIC_LINK((StgClosure *)q) = static_objects;
1854 static_objects = (StgClosure *)q;
1859 if (*STATIC_LINK(info,(StgClosure *)q) == NULL) {
1860 *STATIC_LINK(info,(StgClosure *)q) = static_objects;
1861 static_objects = (StgClosure *)q;
1865 case CONSTR_INTLIKE:
1866 case CONSTR_CHARLIKE:
1867 case CONSTR_NOCAF_STATIC:
1868 /* no need to put these on the static linked list, they don't need
1874 barf("evacuate(static): strange closure type %d", (int)(info->type));
1880 if (bd->gen_no > N) {
1881 /* Can't evacuate this object, because it's in a generation
1882 * older than the ones we're collecting. Let's hope that it's
1883 * in evac_gen or older, or we will have to arrange to track
1884 * this pointer using the mutable list.
1886 if (bd->gen_no < evac_gen) {
1888 failed_to_evac = rtsTrue;
1889 TICK_GC_FAILED_PROMOTION();
1894 if ((bd->flags & (BF_LARGE | BF_COMPACTED | BF_EVACUATED)) != 0) {
1896 /* pointer into to-space: just return it. This normally
1897 * shouldn't happen, but alllowing it makes certain things
1898 * slightly easier (eg. the mutable list can contain the same
1899 * object twice, for example).
1901 if (bd->flags & BF_EVACUATED) {
1902 if (bd->gen_no < evac_gen) {
1903 failed_to_evac = rtsTrue;
1904 TICK_GC_FAILED_PROMOTION();
1909 /* evacuate large objects by re-linking them onto a different list.
1911 if (bd->flags & BF_LARGE) {
1913 if (info->type == TSO &&
1914 ((StgTSO *)q)->what_next == ThreadRelocated) {
1915 q = (StgClosure *)((StgTSO *)q)->link;
1918 evacuate_large((P_)q);
1922 /* If the object is in a step that we're compacting, then we
1923 * need to use an alternative evacuate procedure.
1925 if (bd->flags & BF_COMPACTED) {
1926 if (!is_marked((P_)q,bd)) {
1928 if (mark_stack_full()) {
1929 mark_stack_overflowed = rtsTrue;
1932 push_mark_stack((P_)q);
1942 switch (info->type) {
1947 return copy(q,sizeW_fromITBL(info),stp);
1951 StgWord w = (StgWord)q->payload[0];
1952 if (q->header.info == Czh_con_info &&
1953 // unsigned, so always true: (StgChar)w >= MIN_CHARLIKE &&
1954 (StgChar)w <= MAX_CHARLIKE) {
1955 return (StgClosure *)CHARLIKE_CLOSURE((StgChar)w);
1957 if (q->header.info == Izh_con_info &&
1958 (StgInt)w >= MIN_INTLIKE && (StgInt)w <= MAX_INTLIKE) {
1959 return (StgClosure *)INTLIKE_CLOSURE((StgInt)w);
1962 return copy_noscav(q,sizeofW(StgHeader)+1,stp);
1968 return copy(q,sizeofW(StgHeader)+1,stp);
1972 return copy(q,sizeofW(StgThunk)+1,stp);
1977 #ifdef NO_PROMOTE_THUNKS
1978 if (bd->gen_no == 0 &&
1979 bd->step->no != 0 &&
1980 bd->step->no == generations[bd->gen_no].n_steps-1) {
1984 return copy(q,sizeofW(StgThunk)+2,stp);
1991 return copy(q,sizeofW(StgHeader)+2,stp);
1994 return copy_noscav(q,sizeofW(StgHeader)+2,stp);
1997 return copy(q,thunk_sizeW_fromITBL(info),stp);
2002 case IND_OLDGEN_PERM:
2005 return copy(q,sizeW_fromITBL(info),stp);
2008 return copy(q,bco_sizeW((StgBCO *)q),stp);
2011 case SE_CAF_BLACKHOLE:
2014 return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
2016 case THUNK_SELECTOR:
2019 const StgInfoTable *info_ptr;
2021 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
2022 return copy(q,THUNK_SELECTOR_sizeW(),stp);
2025 // stashed away for LDV profiling, see below
2026 info_ptr = q->header.info;
2028 p = eval_thunk_selector(info->layout.selector_offset,
2032 return copy(q,THUNK_SELECTOR_sizeW(),stp);
2035 // q is still BLACKHOLE'd.
2036 thunk_selector_depth++;
2038 thunk_selector_depth--;
2041 // For the purposes of LDV profiling, we have destroyed
2042 // the original selector thunk.
2043 SET_INFO(q, info_ptr);
2044 LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(q);
2047 // Update the THUNK_SELECTOR with an indirection to the
2048 // EVACUATED closure now at p. Why do this rather than
2049 // upd_evacuee(q,p)? Because we have an invariant that an
2050 // EVACUATED closure always points to an object in the
2051 // same or an older generation (required by the short-cut
2052 // test in the EVACUATED case, below).
2053 SET_INFO(q, &stg_IND_info);
2054 ((StgInd *)q)->indirectee = p;
2056 // For the purposes of LDV profiling, we have created an
2058 LDV_RECORD_CREATE(q);
2066 // follow chains of indirections, don't evacuate them
2067 q = ((StgInd*)q)->indirectee;
2079 case CATCH_STM_FRAME:
2080 case CATCH_RETRY_FRAME:
2081 case ATOMICALLY_FRAME:
2082 // shouldn't see these
2083 barf("evacuate: stack frame at %p\n", q);
2086 return copy(q,pap_sizeW((StgPAP*)q),stp);
2089 return copy(q,ap_sizeW((StgAP*)q),stp);
2092 return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp);
2095 /* Already evacuated, just return the forwarding address.
2096 * HOWEVER: if the requested destination generation (evac_gen) is
2097 * older than the actual generation (because the object was
2098 * already evacuated to a younger generation) then we have to
2099 * set the failed_to_evac flag to indicate that we couldn't
2100 * manage to promote the object to the desired generation.
2103 * Optimisation: the check is fairly expensive, but we can often
2104 * shortcut it if either the required generation is 0, or the
2105 * current object (the EVACUATED) is in a high enough generation.
2106 * We know that an EVACUATED always points to an object in the
2107 * same or an older generation. stp is the lowest step that the
2108 * current object would be evacuated to, so we only do the full
2109 * check if stp is too low.
2111 if (evac_gen > 0 && stp->gen_no < evac_gen) { // optimisation
2112 StgClosure *p = ((StgEvacuated*)q)->evacuee;
2113 if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < evac_gen) {
2114 failed_to_evac = rtsTrue;
2115 TICK_GC_FAILED_PROMOTION();
2118 return ((StgEvacuated*)q)->evacuee;
2121 // just copy the block
2122 return copy_noscav(q,arr_words_sizeW((StgArrWords *)q),stp);
2124 case MUT_ARR_PTRS_CLEAN:
2125 case MUT_ARR_PTRS_DIRTY:
2126 case MUT_ARR_PTRS_FROZEN:
2127 case MUT_ARR_PTRS_FROZEN0:
2128 // just copy the block
2129 return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
2133 StgTSO *tso = (StgTSO *)q;
2135 /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
2137 if (tso->what_next == ThreadRelocated) {
2138 q = (StgClosure *)tso->link;
2142 /* To evacuate a small TSO, we need to relocate the update frame
2149 new_tso = (StgTSO *)copyPart((StgClosure *)tso,
2151 sizeofW(StgTSO), stp);
2152 move_TSO(tso, new_tso);
2153 for (p = tso->sp, q = new_tso->sp;
2154 p < tso->stack+tso->stack_size;) {
2158 return (StgClosure *)new_tso;
2165 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
2166 to = copy(q,BLACKHOLE_sizeW(),stp);
2167 //ToDo: derive size etc from reverted IP
2168 //to = copy(q,size,stp);
2170 debugBelch("@@ evacuate: RBH %p (%s) to %p (%s)",
2171 q, info_type(q), to, info_type(to)));
2176 ASSERT(sizeofW(StgBlockedFetch) >= MIN_PAYLOD_SIZE);
2177 to = copy(q,sizeofW(StgBlockedFetch),stp);
2179 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
2180 q, info_type(q), to, info_type(to)));
2187 ASSERT(sizeofW(StgBlockedFetch) >= MIN_PAYLOAD_SIZE);
2188 to = copy(q,sizeofW(StgFetchMe),stp);
2190 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
2191 q, info_type(q), to, info_type(to)));
2195 ASSERT(sizeofW(StgBlockedFetch) >= MIN_PAYLOAD_SIZE);
2196 to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
2198 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
2199 q, info_type(q), to, info_type(to)));
2204 return copy(q,sizeofW(StgTRecHeader),stp);
2206 case TVAR_WAIT_QUEUE:
2207 return copy(q,sizeofW(StgTVarWaitQueue),stp);
2210 return copy(q,sizeofW(StgTVar),stp);
2213 return copy(q,sizeofW(StgTRecChunk),stp);
2216 barf("evacuate: strange closure type %d", (int)(info->type));
2222 /* -----------------------------------------------------------------------------
2223 Evaluate a THUNK_SELECTOR if possible.
2225 returns: NULL if we couldn't evaluate this THUNK_SELECTOR, or
2226 a closure pointer if we evaluated it and this is the result. Note
2227 that "evaluating" the THUNK_SELECTOR doesn't necessarily mean
2228 reducing it to HNF, just that we have eliminated the selection.
2229 The result might be another thunk, or even another THUNK_SELECTOR.
2231 If the return value is non-NULL, the original selector thunk has
2232 been BLACKHOLE'd, and should be updated with an indirection or a
2233 forwarding pointer. If the return value is NULL, then the selector
2237 ToDo: the treatment of THUNK_SELECTORS could be improved in the
2238 following way (from a suggestion by Ian Lynagh):
2240 We can have a chain like this:
2244 |-----> sel_0 --> (a,b)
2246 |-----> sel_0 --> ...
2248 and the depth limit means we don't go all the way to the end of the
2249 chain, which results in a space leak. This affects the recursive
2250 call to evacuate() in the THUNK_SELECTOR case in evacuate(): *not*
2251 the recursive call to eval_thunk_selector() in
2252 eval_thunk_selector().
2254 We could eliminate the depth bound in this case, in the following
2257 - traverse the chain once to discover the *value* of the
2258 THUNK_SELECTOR. Mark all THUNK_SELECTORS that we
2259 visit on the way as having been visited already (somehow).
2261 - in a second pass, traverse the chain again updating all
2262 THUNK_SEELCTORS that we find on the way with indirections to
2265 - if we encounter a "marked" THUNK_SELECTOR in a normal
2266 evacuate(), we konw it can't be updated so just evac it.
2268 Program that illustrates the problem:
2271 foo (x:xs) = let (ys, zs) = foo xs
2272 in if x >= 0 then (x:ys, zs) else (ys, x:zs)
2274 main = bar [1..(100000000::Int)]
2275 bar xs = (\(ys, zs) -> print ys >> print zs) (foo xs)
2277 -------------------------------------------------------------------------- */
2279 static inline rtsBool
2280 is_to_space ( StgClosure *p )
2284 bd = Bdescr((StgPtr)p);
2285 if (HEAP_ALLOCED(p) &&
2286 ((bd->flags & BF_EVACUATED)
2287 || ((bd->flags & BF_COMPACTED) &&
2288 is_marked((P_)p,bd)))) {
2296 eval_thunk_selector( nat field, StgSelector * p )
2299 const StgInfoTable *info_ptr;
2300 StgClosure *selectee;
2302 selectee = p->selectee;
2304 // Save the real info pointer (NOTE: not the same as get_itbl()).
2305 info_ptr = p->header.info;
2307 // If the THUNK_SELECTOR is in a generation that we are not
2308 // collecting, then bail out early. We won't be able to save any
2309 // space in any case, and updating with an indirection is trickier
2311 if (Bdescr((StgPtr)p)->gen_no > N) {
2315 // BLACKHOLE the selector thunk, since it is now under evaluation.
2316 // This is important to stop us going into an infinite loop if
2317 // this selector thunk eventually refers to itself.
2318 SET_INFO(p,&stg_BLACKHOLE_info);
2322 // We don't want to end up in to-space, because this causes
2323 // problems when the GC later tries to evacuate the result of
2324 // eval_thunk_selector(). There are various ways this could
2327 // 1. following an IND_STATIC
2329 // 2. when the old generation is compacted, the mark phase updates
2330 // from-space pointers to be to-space pointers, and we can't
2331 // reliably tell which we're following (eg. from an IND_STATIC).
2333 // 3. compacting GC again: if we're looking at a constructor in
2334 // the compacted generation, it might point directly to objects
2335 // in to-space. We must bale out here, otherwise doing the selection
2336 // will result in a to-space pointer being returned.
2338 // (1) is dealt with using a BF_EVACUATED test on the
2339 // selectee. (2) and (3): we can tell if we're looking at an
2340 // object in the compacted generation that might point to
2341 // to-space objects by testing that (a) it is BF_COMPACTED, (b)
2342 // the compacted generation is being collected, and (c) the
2343 // object is marked. Only a marked object may have pointers that
2344 // point to to-space objects, because that happens when
2347 // The to-space test is now embodied in the in_to_space() inline
2348 // function, as it is re-used below.
2350 if (is_to_space(selectee)) {
2354 info = get_itbl(selectee);
2355 switch (info->type) {
2363 case CONSTR_NOCAF_STATIC:
2364 // check that the size is in range
2365 ASSERT(field < (StgWord32)(info->layout.payload.ptrs +
2366 info->layout.payload.nptrs));
2368 // Select the right field from the constructor, and check
2369 // that the result isn't in to-space. It might be in
2370 // to-space if, for example, this constructor contains
2371 // pointers to younger-gen objects (and is on the mut-once
2376 q = selectee->payload[field];
2377 if (is_to_space(q)) {
2387 case IND_OLDGEN_PERM:
2389 selectee = ((StgInd *)selectee)->indirectee;
2393 // We don't follow pointers into to-space; the constructor
2394 // has already been evacuated, so we won't save any space
2395 // leaks by evaluating this selector thunk anyhow.
2398 case THUNK_SELECTOR:
2402 // check that we don't recurse too much, re-using the
2403 // depth bound also used in evacuate().
2404 if (thunk_selector_depth >= MAX_THUNK_SELECTOR_DEPTH) {
2407 thunk_selector_depth++;
2409 val = eval_thunk_selector(info->layout.selector_offset,
2410 (StgSelector *)selectee);
2412 thunk_selector_depth--;
2417 // We evaluated this selector thunk, so update it with
2418 // an indirection. NOTE: we don't use UPD_IND here,
2419 // because we are guaranteed that p is in a generation
2420 // that we are collecting, and we never want to put the
2421 // indirection on a mutable list.
2423 // For the purposes of LDV profiling, we have destroyed
2424 // the original selector thunk.
2425 SET_INFO(p, info_ptr);
2426 LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(selectee);
2428 ((StgInd *)selectee)->indirectee = val;
2429 SET_INFO(selectee,&stg_IND_info);
2431 // For the purposes of LDV profiling, we have created an
2433 LDV_RECORD_CREATE(selectee);
2450 case SE_CAF_BLACKHOLE:
2462 // not evaluated yet
2466 barf("eval_thunk_selector: strange selectee %d",
2471 // We didn't manage to evaluate this thunk; restore the old info pointer
2472 SET_INFO(p, info_ptr);
2476 /* -----------------------------------------------------------------------------
2477 move_TSO is called to update the TSO structure after it has been
2478 moved from one place to another.
2479 -------------------------------------------------------------------------- */
2482 move_TSO (StgTSO *src, StgTSO *dest)
2486 // relocate the stack pointer...
2487 diff = (StgPtr)dest - (StgPtr)src; // In *words*
2488 dest->sp = (StgPtr)dest->sp + diff;
2491 /* Similar to scavenge_large_bitmap(), but we don't write back the
2492 * pointers we get back from evacuate().
2495 scavenge_large_srt_bitmap( StgLargeSRT *large_srt )
2502 bitmap = large_srt->l.bitmap[b];
2503 size = (nat)large_srt->l.size;
2504 p = (StgClosure **)large_srt->srt;
2505 for (i = 0; i < size; ) {
2506 if ((bitmap & 1) != 0) {
2511 if (i % BITS_IN(W_) == 0) {
2513 bitmap = large_srt->l.bitmap[b];
2515 bitmap = bitmap >> 1;
2520 /* evacuate the SRT. If srt_bitmap is zero, then there isn't an
2521 * srt field in the info table. That's ok, because we'll
2522 * never dereference it.
2525 scavenge_srt (StgClosure **srt, nat srt_bitmap)
2530 bitmap = srt_bitmap;
2533 if (bitmap == (StgHalfWord)(-1)) {
2534 scavenge_large_srt_bitmap( (StgLargeSRT *)srt );
2538 while (bitmap != 0) {
2539 if ((bitmap & 1) != 0) {
2540 #ifdef ENABLE_WIN32_DLL_SUPPORT
2541 // Special-case to handle references to closures hiding out in DLLs, since
2542 // double indirections required to get at those. The code generator knows
2543 // which is which when generating the SRT, so it stores the (indirect)
2544 // reference to the DLL closure in the table by first adding one to it.
2545 // We check for this here, and undo the addition before evacuating it.
2547 // If the SRT entry hasn't got bit 0 set, the SRT entry points to a
2548 // closure that's fixed at link-time, and no extra magic is required.
2549 if ( (unsigned long)(*srt) & 0x1 ) {
2550 evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
2559 bitmap = bitmap >> 1;
2565 scavenge_thunk_srt(const StgInfoTable *info)
2567 StgThunkInfoTable *thunk_info;
2569 if (!major_gc) return;
2571 thunk_info = itbl_to_thunk_itbl(info);
2572 scavenge_srt((StgClosure **)GET_SRT(thunk_info), thunk_info->i.srt_bitmap);
2576 scavenge_fun_srt(const StgInfoTable *info)
2578 StgFunInfoTable *fun_info;
2580 if (!major_gc) return;
2582 fun_info = itbl_to_fun_itbl(info);
2583 scavenge_srt((StgClosure **)GET_FUN_SRT(fun_info), fun_info->i.srt_bitmap);
2586 /* -----------------------------------------------------------------------------
2588 -------------------------------------------------------------------------- */
2591 scavengeTSO (StgTSO *tso)
2593 if ( tso->why_blocked == BlockedOnMVar
2594 || tso->why_blocked == BlockedOnBlackHole
2595 || tso->why_blocked == BlockedOnException
2597 || tso->why_blocked == BlockedOnGA
2598 || tso->why_blocked == BlockedOnGA_NoSend
2601 tso->block_info.closure = evacuate(tso->block_info.closure);
2603 if ( tso->blocked_exceptions != NULL ) {
2604 tso->blocked_exceptions =
2605 (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
2608 // We don't always chase the link field: TSOs on the blackhole
2609 // queue are not automatically alive, so the link field is a
2610 // "weak" pointer in that case.
2611 if (tso->why_blocked != BlockedOnBlackHole) {
2612 tso->link = (StgTSO *)evacuate((StgClosure *)tso->link);
2615 // scavange current transaction record
2616 tso->trec = (StgTRecHeader *)evacuate((StgClosure *)tso->trec);
2618 // scavenge this thread's stack
2619 scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
2622 /* -----------------------------------------------------------------------------
2623 Blocks of function args occur on the stack (at the top) and
2625 -------------------------------------------------------------------------- */
2627 STATIC_INLINE StgPtr
2628 scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
2635 switch (fun_info->f.fun_type) {
2637 bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
2638 size = BITMAP_SIZE(fun_info->f.b.bitmap);
2641 size = GET_FUN_LARGE_BITMAP(fun_info)->size;
2642 scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
2646 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2647 size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->f.fun_type]);
2650 if ((bitmap & 1) == 0) {
2651 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2654 bitmap = bitmap >> 1;
2662 STATIC_INLINE StgPtr
2663 scavenge_PAP_payload (StgClosure *fun, StgClosure **payload, StgWord size)
2667 StgFunInfoTable *fun_info;
2669 fun_info = get_fun_itbl(fun);
2670 ASSERT(fun_info->i.type != PAP);
2671 p = (StgPtr)payload;
2673 switch (fun_info->f.fun_type) {
2675 bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
2678 scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
2682 scavenge_large_bitmap((StgPtr)payload, BCO_BITMAP(fun), size);
2686 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2689 if ((bitmap & 1) == 0) {
2690 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2693 bitmap = bitmap >> 1;
2701 STATIC_INLINE StgPtr
2702 scavenge_PAP (StgPAP *pap)
2704 pap->fun = evacuate(pap->fun);
2705 return scavenge_PAP_payload (pap->fun, pap->payload, pap->n_args);
2708 STATIC_INLINE StgPtr
2709 scavenge_AP (StgAP *ap)
2711 ap->fun = evacuate(ap->fun);
2712 return scavenge_PAP_payload (ap->fun, ap->payload, ap->n_args);
2715 /* -----------------------------------------------------------------------------
2716 Scavenge a given step until there are no more objects in this step
2719 evac_gen is set by the caller to be either zero (for a step in a
2720 generation < N) or G where G is the generation of the step being
2723 We sometimes temporarily change evac_gen back to zero if we're
2724 scavenging a mutable object where early promotion isn't such a good
2726 -------------------------------------------------------------------------- */
2734 nat saved_evac_gen = evac_gen;
2739 failed_to_evac = rtsFalse;
2741 /* scavenge phase - standard breadth-first scavenging of the
2745 while (bd != stp->hp_bd || p < stp->hp) {
2747 // If we're at the end of this block, move on to the next block
2748 if (bd != stp->hp_bd && p == bd->free) {
2754 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2755 info = get_itbl((StgClosure *)p);
2757 ASSERT(thunk_selector_depth == 0);
2760 switch (info->type) {
2764 StgMVar *mvar = ((StgMVar *)p);
2766 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
2767 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
2768 mvar->value = evacuate((StgClosure *)mvar->value);
2769 evac_gen = saved_evac_gen;
2770 failed_to_evac = rtsTrue; // mutable.
2771 p += sizeofW(StgMVar);
2776 scavenge_fun_srt(info);
2777 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2778 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2779 p += sizeofW(StgHeader) + 2;
2783 scavenge_thunk_srt(info);
2784 ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
2785 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2786 p += sizeofW(StgThunk) + 2;
2790 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2791 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2792 p += sizeofW(StgHeader) + 2;
2796 scavenge_thunk_srt(info);
2797 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2798 p += sizeofW(StgThunk) + 1;
2802 scavenge_fun_srt(info);
2804 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2805 p += sizeofW(StgHeader) + 1;
2809 scavenge_thunk_srt(info);
2810 p += sizeofW(StgThunk) + 1;
2814 scavenge_fun_srt(info);
2816 p += sizeofW(StgHeader) + 1;
2820 scavenge_thunk_srt(info);
2821 p += sizeofW(StgThunk) + 2;
2825 scavenge_fun_srt(info);
2827 p += sizeofW(StgHeader) + 2;
2831 scavenge_thunk_srt(info);
2832 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2833 p += sizeofW(StgThunk) + 2;
2837 scavenge_fun_srt(info);
2839 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2840 p += sizeofW(StgHeader) + 2;
2844 scavenge_fun_srt(info);
2851 scavenge_thunk_srt(info);
2852 end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
2853 for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
2854 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2856 p += info->layout.payload.nptrs;
2867 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2868 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2869 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2871 p += info->layout.payload.nptrs;
2876 StgBCO *bco = (StgBCO *)p;
2877 bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
2878 bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
2879 bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
2880 bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
2881 p += bco_sizeW(bco);
2886 if (stp->gen->no != 0) {
2889 // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an
2890 // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
2891 LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
2894 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
2896 SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
2898 // We pretend that p has just been created.
2899 LDV_RECORD_CREATE((StgClosure *)p);
2902 case IND_OLDGEN_PERM:
2903 ((StgInd *)p)->indirectee = evacuate(((StgInd *)p)->indirectee);
2904 p += sizeofW(StgInd);
2908 case MUT_VAR_DIRTY: {
2909 rtsBool saved_eager_promotion = eager_promotion;
2911 eager_promotion = rtsFalse;
2912 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2913 eager_promotion = saved_eager_promotion;
2915 if (failed_to_evac) {
2916 ((StgClosure *)q)->header.info = &stg_MUT_VAR_DIRTY_info;
2918 ((StgClosure *)q)->header.info = &stg_MUT_VAR_CLEAN_info;
2920 p += sizeofW(StgMutVar);
2925 case SE_CAF_BLACKHOLE:
2928 p += BLACKHOLE_sizeW();
2931 case THUNK_SELECTOR:
2933 StgSelector *s = (StgSelector *)p;
2934 s->selectee = evacuate(s->selectee);
2935 p += THUNK_SELECTOR_sizeW();
2939 // A chunk of stack saved in a heap object
2942 StgAP_STACK *ap = (StgAP_STACK *)p;
2944 ap->fun = evacuate(ap->fun);
2945 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2946 p = (StgPtr)ap->payload + ap->size;
2951 p = scavenge_PAP((StgPAP *)p);
2955 p = scavenge_AP((StgAP *)p);
2959 // nothing to follow
2960 p += arr_words_sizeW((StgArrWords *)p);
2963 case MUT_ARR_PTRS_CLEAN:
2964 case MUT_ARR_PTRS_DIRTY:
2965 // follow everything
2968 rtsBool saved_eager;
2970 // We don't eagerly promote objects pointed to by a mutable
2971 // array, but if we find the array only points to objects in
2972 // the same or an older generation, we mark it "clean" and
2973 // avoid traversing it during minor GCs.
2974 saved_eager = eager_promotion;
2975 eager_promotion = rtsFalse;
2976 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2977 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2978 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2980 eager_promotion = saved_eager;
2982 if (failed_to_evac) {
2983 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
2985 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
2988 failed_to_evac = rtsTrue; // always put it on the mutable list.
2992 case MUT_ARR_PTRS_FROZEN:
2993 case MUT_ARR_PTRS_FROZEN0:
2994 // follow everything
2998 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2999 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3000 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3003 // If we're going to put this object on the mutable list, then
3004 // set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that.
3005 if (failed_to_evac) {
3006 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info;
3008 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info;
3015 StgTSO *tso = (StgTSO *)p;
3016 rtsBool saved_eager = eager_promotion;
3018 eager_promotion = rtsFalse;
3020 eager_promotion = saved_eager;
3022 if (failed_to_evac) {
3023 tso->flags |= TSO_DIRTY;
3025 tso->flags &= ~TSO_DIRTY;
3028 failed_to_evac = rtsTrue; // always on the mutable list
3029 p += tso_sizeW(tso);
3037 nat size, ptrs, nonptrs, vhs;
3039 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3041 StgRBH *rbh = (StgRBH *)p;
3042 (StgClosure *)rbh->blocking_queue =
3043 evacuate((StgClosure *)rbh->blocking_queue);
3044 failed_to_evac = rtsTrue; // mutable anyhow.
3046 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3047 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3048 // ToDo: use size of reverted closure here!
3049 p += BLACKHOLE_sizeW();
3055 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3056 // follow the pointer to the node which is being demanded
3057 (StgClosure *)bf->node =
3058 evacuate((StgClosure *)bf->node);
3059 // follow the link to the rest of the blocking queue
3060 (StgClosure *)bf->link =
3061 evacuate((StgClosure *)bf->link);
3063 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3064 bf, info_type((StgClosure *)bf),
3065 bf->node, info_type(bf->node)));
3066 p += sizeofW(StgBlockedFetch);
3074 p += sizeofW(StgFetchMe);
3075 break; // nothing to do in this case
3079 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3080 (StgClosure *)fmbq->blocking_queue =
3081 evacuate((StgClosure *)fmbq->blocking_queue);
3083 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3084 p, info_type((StgClosure *)p)));
3085 p += sizeofW(StgFetchMeBlockingQueue);
3090 case TVAR_WAIT_QUEUE:
3092 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3094 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3095 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3096 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3097 evac_gen = saved_evac_gen;
3098 failed_to_evac = rtsTrue; // mutable
3099 p += sizeofW(StgTVarWaitQueue);
3105 StgTVar *tvar = ((StgTVar *) p);
3107 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3108 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3109 evac_gen = saved_evac_gen;
3110 failed_to_evac = rtsTrue; // mutable
3111 p += sizeofW(StgTVar);
3117 StgTRecHeader *trec = ((StgTRecHeader *) p);
3119 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3120 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3121 evac_gen = saved_evac_gen;
3122 failed_to_evac = rtsTrue; // mutable
3123 p += sizeofW(StgTRecHeader);
3130 StgTRecChunk *tc = ((StgTRecChunk *) p);
3131 TRecEntry *e = &(tc -> entries[0]);
3133 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3134 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3135 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3136 e->expected_value = evacuate((StgClosure*)e->expected_value);
3137 e->new_value = evacuate((StgClosure*)e->new_value);
3139 evac_gen = saved_evac_gen;
3140 failed_to_evac = rtsTrue; // mutable
3141 p += sizeofW(StgTRecChunk);
3146 barf("scavenge: unimplemented/strange closure type %d @ %p",
3151 * We need to record the current object on the mutable list if
3152 * (a) It is actually mutable, or
3153 * (b) It contains pointers to a younger generation.
3154 * Case (b) arises if we didn't manage to promote everything that
3155 * the current object points to into the current generation.
3157 if (failed_to_evac) {
3158 failed_to_evac = rtsFalse;
3159 if (stp->gen_no > 0) {
3160 recordMutableGen((StgClosure *)q, stp->gen);
3169 /* -----------------------------------------------------------------------------
3170 Scavenge everything on the mark stack.
3172 This is slightly different from scavenge():
3173 - we don't walk linearly through the objects, so the scavenger
3174 doesn't need to advance the pointer on to the next object.
3175 -------------------------------------------------------------------------- */
3178 scavenge_mark_stack(void)
3184 evac_gen = oldest_gen->no;
3185 saved_evac_gen = evac_gen;
3188 while (!mark_stack_empty()) {
3189 p = pop_mark_stack();
3191 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3192 info = get_itbl((StgClosure *)p);
3195 switch (info->type) {
3199 StgMVar *mvar = ((StgMVar *)p);
3201 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
3202 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
3203 mvar->value = evacuate((StgClosure *)mvar->value);
3204 evac_gen = saved_evac_gen;
3205 failed_to_evac = rtsTrue; // mutable.
3210 scavenge_fun_srt(info);
3211 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
3212 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3216 scavenge_thunk_srt(info);
3217 ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
3218 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
3222 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
3223 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3228 scavenge_fun_srt(info);
3229 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3234 scavenge_thunk_srt(info);
3235 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
3240 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3245 scavenge_fun_srt(info);
3250 scavenge_thunk_srt(info);
3258 scavenge_fun_srt(info);
3265 scavenge_thunk_srt(info);
3266 end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
3267 for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
3268 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3280 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3281 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
3282 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3288 StgBCO *bco = (StgBCO *)p;
3289 bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
3290 bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
3291 bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
3292 bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
3297 // don't need to do anything here: the only possible case
3298 // is that we're in a 1-space compacting collector, with
3299 // no "old" generation.
3303 case IND_OLDGEN_PERM:
3304 ((StgInd *)p)->indirectee =
3305 evacuate(((StgInd *)p)->indirectee);
3309 case MUT_VAR_DIRTY: {
3310 rtsBool saved_eager_promotion = eager_promotion;
3312 eager_promotion = rtsFalse;
3313 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3314 eager_promotion = saved_eager_promotion;
3316 if (failed_to_evac) {
3317 ((StgClosure *)q)->header.info = &stg_MUT_VAR_DIRTY_info;
3319 ((StgClosure *)q)->header.info = &stg_MUT_VAR_CLEAN_info;
3325 case SE_CAF_BLACKHOLE:
3331 case THUNK_SELECTOR:
3333 StgSelector *s = (StgSelector *)p;
3334 s->selectee = evacuate(s->selectee);
3338 // A chunk of stack saved in a heap object
3341 StgAP_STACK *ap = (StgAP_STACK *)p;
3343 ap->fun = evacuate(ap->fun);
3344 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3349 scavenge_PAP((StgPAP *)p);
3353 scavenge_AP((StgAP *)p);
3356 case MUT_ARR_PTRS_CLEAN:
3357 case MUT_ARR_PTRS_DIRTY:
3358 // follow everything
3361 rtsBool saved_eager;
3363 // We don't eagerly promote objects pointed to by a mutable
3364 // array, but if we find the array only points to objects in
3365 // the same or an older generation, we mark it "clean" and
3366 // avoid traversing it during minor GCs.
3367 saved_eager = eager_promotion;
3368 eager_promotion = rtsFalse;
3369 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3370 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3371 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3373 eager_promotion = saved_eager;
3375 if (failed_to_evac) {
3376 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
3378 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
3381 failed_to_evac = rtsTrue; // mutable anyhow.
3385 case MUT_ARR_PTRS_FROZEN:
3386 case MUT_ARR_PTRS_FROZEN0:
3387 // follow everything
3391 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3392 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3393 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3396 // If we're going to put this object on the mutable list, then
3397 // set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that.
3398 if (failed_to_evac) {
3399 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info;
3401 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info;
3408 StgTSO *tso = (StgTSO *)p;
3409 rtsBool saved_eager = eager_promotion;
3411 eager_promotion = rtsFalse;
3413 eager_promotion = saved_eager;
3415 if (failed_to_evac) {
3416 tso->flags |= TSO_DIRTY;
3418 tso->flags &= ~TSO_DIRTY;
3421 failed_to_evac = rtsTrue; // always on the mutable list
3429 nat size, ptrs, nonptrs, vhs;
3431 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3433 StgRBH *rbh = (StgRBH *)p;
3434 bh->blocking_queue =
3435 (StgTSO *)evacuate((StgClosure *)bh->blocking_queue);
3436 failed_to_evac = rtsTrue; // mutable anyhow.
3438 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3439 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3445 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3446 // follow the pointer to the node which is being demanded
3447 (StgClosure *)bf->node =
3448 evacuate((StgClosure *)bf->node);
3449 // follow the link to the rest of the blocking queue
3450 (StgClosure *)bf->link =
3451 evacuate((StgClosure *)bf->link);
3453 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3454 bf, info_type((StgClosure *)bf),
3455 bf->node, info_type(bf->node)));
3463 break; // nothing to do in this case
3467 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3468 (StgClosure *)fmbq->blocking_queue =
3469 evacuate((StgClosure *)fmbq->blocking_queue);
3471 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3472 p, info_type((StgClosure *)p)));
3477 case TVAR_WAIT_QUEUE:
3479 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3481 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3482 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3483 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3484 evac_gen = saved_evac_gen;
3485 failed_to_evac = rtsTrue; // mutable
3491 StgTVar *tvar = ((StgTVar *) p);
3493 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3494 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3495 evac_gen = saved_evac_gen;
3496 failed_to_evac = rtsTrue; // mutable
3503 StgTRecChunk *tc = ((StgTRecChunk *) p);
3504 TRecEntry *e = &(tc -> entries[0]);
3506 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3507 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3508 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3509 e->expected_value = evacuate((StgClosure*)e->expected_value);
3510 e->new_value = evacuate((StgClosure*)e->new_value);
3512 evac_gen = saved_evac_gen;
3513 failed_to_evac = rtsTrue; // mutable
3519 StgTRecHeader *trec = ((StgTRecHeader *) p);
3521 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3522 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3523 evac_gen = saved_evac_gen;
3524 failed_to_evac = rtsTrue; // mutable
3529 barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p",
3533 if (failed_to_evac) {
3534 failed_to_evac = rtsFalse;
3536 recordMutableGen((StgClosure *)q, &generations[evac_gen]);
3540 // mark the next bit to indicate "scavenged"
3541 mark(q+1, Bdescr(q));
3543 } // while (!mark_stack_empty())
3545 // start a new linear scan if the mark stack overflowed at some point
3546 if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
3547 IF_DEBUG(gc, debugBelch("scavenge_mark_stack: starting linear scan"));
3548 mark_stack_overflowed = rtsFalse;
3549 oldgen_scan_bd = oldest_gen->steps[0].old_blocks;
3550 oldgen_scan = oldgen_scan_bd->start;
3553 if (oldgen_scan_bd) {
3554 // push a new thing on the mark stack
3556 // find a closure that is marked but not scavenged, and start
3558 while (oldgen_scan < oldgen_scan_bd->free
3559 && !is_marked(oldgen_scan,oldgen_scan_bd)) {
3563 if (oldgen_scan < oldgen_scan_bd->free) {
3565 // already scavenged?
3566 if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
3567 oldgen_scan += sizeofW(StgHeader) + MIN_PAYLOAD_SIZE;
3570 push_mark_stack(oldgen_scan);
3571 // ToDo: bump the linear scan by the actual size of the object
3572 oldgen_scan += sizeofW(StgHeader) + MIN_PAYLOAD_SIZE;
3576 oldgen_scan_bd = oldgen_scan_bd->link;
3577 if (oldgen_scan_bd != NULL) {
3578 oldgen_scan = oldgen_scan_bd->start;
3584 /* -----------------------------------------------------------------------------
3585 Scavenge one object.
3587 This is used for objects that are temporarily marked as mutable
3588 because they contain old-to-new generation pointers. Only certain
3589 objects can have this property.
3590 -------------------------------------------------------------------------- */
3593 scavenge_one(StgPtr p)
3595 const StgInfoTable *info;
3596 nat saved_evac_gen = evac_gen;
3599 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3600 info = get_itbl((StgClosure *)p);
3602 switch (info->type) {
3606 StgMVar *mvar = ((StgMVar *)p);
3608 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
3609 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
3610 mvar->value = evacuate((StgClosure *)mvar->value);
3611 evac_gen = saved_evac_gen;
3612 failed_to_evac = rtsTrue; // mutable.
3625 end = (StgPtr)((StgThunk *)p)->payload + info->layout.payload.ptrs;
3626 for (q = (StgPtr)((StgThunk *)p)->payload; q < end; q++) {
3627 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3633 case FUN_1_0: // hardly worth specialising these guys
3649 end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3650 for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
3651 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3657 case MUT_VAR_DIRTY: {
3659 rtsBool saved_eager_promotion = eager_promotion;
3661 eager_promotion = rtsFalse;
3662 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3663 eager_promotion = saved_eager_promotion;
3665 if (failed_to_evac) {
3666 ((StgClosure *)q)->header.info = &stg_MUT_VAR_DIRTY_info;
3668 ((StgClosure *)q)->header.info = &stg_MUT_VAR_CLEAN_info;
3674 case SE_CAF_BLACKHOLE:
3679 case THUNK_SELECTOR:
3681 StgSelector *s = (StgSelector *)p;
3682 s->selectee = evacuate(s->selectee);
3688 StgAP_STACK *ap = (StgAP_STACK *)p;
3690 ap->fun = evacuate(ap->fun);
3691 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3692 p = (StgPtr)ap->payload + ap->size;
3697 p = scavenge_PAP((StgPAP *)p);
3701 p = scavenge_AP((StgAP *)p);
3705 // nothing to follow
3708 case MUT_ARR_PTRS_CLEAN:
3709 case MUT_ARR_PTRS_DIRTY:
3712 rtsBool saved_eager;
3714 // We don't eagerly promote objects pointed to by a mutable
3715 // array, but if we find the array only points to objects in
3716 // the same or an older generation, we mark it "clean" and
3717 // avoid traversing it during minor GCs.
3718 saved_eager = eager_promotion;
3719 eager_promotion = rtsFalse;
3721 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3722 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3723 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3725 eager_promotion = saved_eager;
3727 if (failed_to_evac) {
3728 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
3730 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
3733 failed_to_evac = rtsTrue;
3737 case MUT_ARR_PTRS_FROZEN:
3738 case MUT_ARR_PTRS_FROZEN0:
3740 // follow everything
3743 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3744 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3745 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3748 // If we're going to put this object on the mutable list, then
3749 // set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that.
3750 if (failed_to_evac) {
3751 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info;
3753 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info;
3760 StgTSO *tso = (StgTSO *)p;
3761 rtsBool saved_eager = eager_promotion;
3763 eager_promotion = rtsFalse;
3765 eager_promotion = saved_eager;
3767 if (failed_to_evac) {
3768 tso->flags |= TSO_DIRTY;
3770 tso->flags &= ~TSO_DIRTY;
3773 failed_to_evac = rtsTrue; // always on the mutable list
3781 nat size, ptrs, nonptrs, vhs;
3783 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3785 StgRBH *rbh = (StgRBH *)p;
3786 (StgClosure *)rbh->blocking_queue =
3787 evacuate((StgClosure *)rbh->blocking_queue);
3788 failed_to_evac = rtsTrue; // mutable anyhow.
3790 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3791 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3792 // ToDo: use size of reverted closure here!
3798 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3799 // follow the pointer to the node which is being demanded
3800 (StgClosure *)bf->node =
3801 evacuate((StgClosure *)bf->node);
3802 // follow the link to the rest of the blocking queue
3803 (StgClosure *)bf->link =
3804 evacuate((StgClosure *)bf->link);
3806 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3807 bf, info_type((StgClosure *)bf),
3808 bf->node, info_type(bf->node)));
3816 break; // nothing to do in this case
3820 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3821 (StgClosure *)fmbq->blocking_queue =
3822 evacuate((StgClosure *)fmbq->blocking_queue);
3824 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3825 p, info_type((StgClosure *)p)));
3830 case TVAR_WAIT_QUEUE:
3832 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3834 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3835 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3836 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3837 evac_gen = saved_evac_gen;
3838 failed_to_evac = rtsTrue; // mutable
3844 StgTVar *tvar = ((StgTVar *) p);
3846 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3847 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3848 evac_gen = saved_evac_gen;
3849 failed_to_evac = rtsTrue; // mutable
3855 StgTRecHeader *trec = ((StgTRecHeader *) p);
3857 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3858 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3859 evac_gen = saved_evac_gen;
3860 failed_to_evac = rtsTrue; // mutable
3867 StgTRecChunk *tc = ((StgTRecChunk *) p);
3868 TRecEntry *e = &(tc -> entries[0]);
3870 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3871 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3872 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3873 e->expected_value = evacuate((StgClosure*)e->expected_value);
3874 e->new_value = evacuate((StgClosure*)e->new_value);
3876 evac_gen = saved_evac_gen;
3877 failed_to_evac = rtsTrue; // mutable
3882 case IND_OLDGEN_PERM:
3885 /* Careful here: a THUNK can be on the mutable list because
3886 * it contains pointers to young gen objects. If such a thunk
3887 * is updated, the IND_OLDGEN will be added to the mutable
3888 * list again, and we'll scavenge it twice. evacuate()
3889 * doesn't check whether the object has already been
3890 * evacuated, so we perform that check here.
3892 StgClosure *q = ((StgInd *)p)->indirectee;
3893 if (HEAP_ALLOCED(q) && Bdescr((StgPtr)q)->flags & BF_EVACUATED) {
3896 ((StgInd *)p)->indirectee = evacuate(q);
3899 #if 0 && defined(DEBUG)
3900 if (RtsFlags.DebugFlags.gc)
3901 /* Debugging code to print out the size of the thing we just
3905 StgPtr start = gen->steps[0].scan;
3906 bdescr *start_bd = gen->steps[0].scan_bd;
3908 scavenge(&gen->steps[0]);
3909 if (start_bd != gen->steps[0].scan_bd) {
3910 size += (P_)BLOCK_ROUND_UP(start) - start;
3911 start_bd = start_bd->link;
3912 while (start_bd != gen->steps[0].scan_bd) {
3913 size += BLOCK_SIZE_W;
3914 start_bd = start_bd->link;
3916 size += gen->steps[0].scan -
3917 (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
3919 size = gen->steps[0].scan - start;
3921 debugBelch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
3927 barf("scavenge_one: strange object %d", (int)(info->type));
3930 no_luck = failed_to_evac;
3931 failed_to_evac = rtsFalse;
3935 /* -----------------------------------------------------------------------------
3936 Scavenging mutable lists.
3938 We treat the mutable list of each generation > N (i.e. all the
3939 generations older than the one being collected) as roots. We also
3940 remove non-mutable objects from the mutable list at this point.
3941 -------------------------------------------------------------------------- */
3944 scavenge_mutable_list(generation *gen)
3949 bd = gen->saved_mut_list;
3952 for (; bd != NULL; bd = bd->link) {
3953 for (q = bd->start; q < bd->free; q++) {
3955 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3958 switch (get_itbl((StgClosure *)p)->type) {
3960 barf("MUT_VAR_CLEAN on mutable list");
3962 mutlist_MUTVARS++; break;
3963 case MUT_ARR_PTRS_CLEAN:
3964 case MUT_ARR_PTRS_DIRTY:
3965 case MUT_ARR_PTRS_FROZEN:
3966 case MUT_ARR_PTRS_FROZEN0:
3967 mutlist_MUTARRS++; break;
3969 mutlist_OTHERS++; break;
3973 // Check whether this object is "clean", that is it
3974 // definitely doesn't point into a young generation.
3975 // Clean objects don't need to be scavenged. Some clean
3976 // objects (MUT_VAR_CLEAN) are not kept on the mutable
3977 // list at all; others, such as MUT_ARR_PTRS_CLEAN and
3978 // TSO, are always on the mutable list.
3980 switch (get_itbl((StgClosure *)p)->type) {
3981 case MUT_ARR_PTRS_CLEAN:
3982 recordMutableGen((StgClosure *)p,gen);
3985 StgTSO *tso = (StgTSO *)p;
3986 if ((tso->flags & TSO_DIRTY) == 0) {
3987 // A clean TSO: we don't have to traverse its
3988 // stack. However, we *do* follow the link field:
3989 // we don't want to have to mark a TSO dirty just
3990 // because we put it on a different queue.
3991 if (tso->why_blocked != BlockedOnBlackHole) {
3992 tso->link = (StgTSO *)evacuate((StgClosure *)tso->link);
3994 recordMutableGen((StgClosure *)p,gen);
4002 if (scavenge_one(p)) {
4003 // didn't manage to promote everything, so put the
4004 // object back on the list.
4005 recordMutableGen((StgClosure *)p,gen);
4010 // free the old mut_list
4011 freeChain(gen->saved_mut_list);
4012 gen->saved_mut_list = NULL;
4017 scavenge_static(void)
4019 StgClosure* p = static_objects;
4020 const StgInfoTable *info;
4022 /* Always evacuate straight to the oldest generation for static
4024 evac_gen = oldest_gen->no;
4026 /* keep going until we've scavenged all the objects on the linked
4028 while (p != END_OF_STATIC_LIST) {
4030 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
4033 if (info->type==RBH)
4034 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
4036 // make sure the info pointer is into text space
4038 /* Take this object *off* the static_objects list,
4039 * and put it on the scavenged_static_objects list.
4041 static_objects = *STATIC_LINK(info,p);
4042 *STATIC_LINK(info,p) = scavenged_static_objects;
4043 scavenged_static_objects = p;
4045 switch (info -> type) {
4049 StgInd *ind = (StgInd *)p;
4050 ind->indirectee = evacuate(ind->indirectee);
4052 /* might fail to evacuate it, in which case we have to pop it
4053 * back on the mutable list of the oldest generation. We
4054 * leave it *on* the scavenged_static_objects list, though,
4055 * in case we visit this object again.
4057 if (failed_to_evac) {
4058 failed_to_evac = rtsFalse;
4059 recordMutableGen((StgClosure *)p,oldest_gen);
4065 scavenge_thunk_srt(info);
4069 scavenge_fun_srt(info);
4076 next = (P_)p->payload + info->layout.payload.ptrs;
4077 // evacuate the pointers
4078 for (q = (P_)p->payload; q < next; q++) {
4079 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
4085 barf("scavenge_static: strange closure %d", (int)(info->type));
4088 ASSERT(failed_to_evac == rtsFalse);
4090 /* get the next static object from the list. Remember, there might
4091 * be more stuff on this list now that we've done some evacuating!
4092 * (static_objects is a global)
4098 /* -----------------------------------------------------------------------------
4099 scavenge a chunk of memory described by a bitmap
4100 -------------------------------------------------------------------------- */
4103 scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
4109 bitmap = large_bitmap->bitmap[b];
4110 for (i = 0; i < size; ) {
4111 if ((bitmap & 1) == 0) {
4112 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
4116 if (i % BITS_IN(W_) == 0) {
4118 bitmap = large_bitmap->bitmap[b];
4120 bitmap = bitmap >> 1;
4125 STATIC_INLINE StgPtr
4126 scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap)
4129 if ((bitmap & 1) == 0) {
4130 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
4133 bitmap = bitmap >> 1;
4139 /* -----------------------------------------------------------------------------
4140 scavenge_stack walks over a section of stack and evacuates all the
4141 objects pointed to by it. We can use the same code for walking
4142 AP_STACK_UPDs, since these are just sections of copied stack.
4143 -------------------------------------------------------------------------- */
4147 scavenge_stack(StgPtr p, StgPtr stack_end)
4149 const StgRetInfoTable* info;
4153 //IF_DEBUG(sanity, debugBelch(" scavenging stack between %p and %p", p, stack_end));
4156 * Each time around this loop, we are looking at a chunk of stack
4157 * that starts with an activation record.
4160 while (p < stack_end) {
4161 info = get_ret_itbl((StgClosure *)p);
4163 switch (info->i.type) {
4166 // In SMP, we can get update frames that point to indirections
4167 // when two threads evaluate the same thunk. We do attempt to
4168 // discover this situation in threadPaused(), but it's
4169 // possible that the following sequence occurs:
4178 // Now T is an indirection, and the update frame is already
4179 // marked on A's stack, so we won't traverse it again in
4180 // threadPaused(). We could traverse the whole stack again
4181 // before GC, but that seems like overkill.
4183 // Scavenging this update frame as normal would be disastrous;
4184 // the updatee would end up pointing to the value. So we turn
4185 // the indirection into an IND_PERM, so that evacuate will
4186 // copy the indirection into the old generation instead of
4188 if (get_itbl(((StgUpdateFrame *)p)->updatee)->type == IND) {
4189 ((StgUpdateFrame *)p)->updatee->header.info =
4190 (StgInfoTable *)&stg_IND_PERM_info;
4192 ((StgUpdateFrame *)p)->updatee
4193 = evacuate(((StgUpdateFrame *)p)->updatee);
4194 p += sizeofW(StgUpdateFrame);
4197 // small bitmap (< 32 entries, or 64 on a 64-bit machine)
4198 case CATCH_STM_FRAME:
4199 case CATCH_RETRY_FRAME:
4200 case ATOMICALLY_FRAME:
4205 bitmap = BITMAP_BITS(info->i.layout.bitmap);
4206 size = BITMAP_SIZE(info->i.layout.bitmap);
4207 // NOTE: the payload starts immediately after the info-ptr, we
4208 // don't have an StgHeader in the same sense as a heap closure.
4210 p = scavenge_small_bitmap(p, size, bitmap);
4214 scavenge_srt((StgClosure **)GET_SRT(info), info->i.srt_bitmap);
4222 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
4225 size = BCO_BITMAP_SIZE(bco);
4226 scavenge_large_bitmap(p, BCO_BITMAP(bco), size);
4231 // large bitmap (> 32 entries, or > 64 on a 64-bit machine)
4237 size = GET_LARGE_BITMAP(&info->i)->size;
4239 scavenge_large_bitmap(p, GET_LARGE_BITMAP(&info->i), size);
4241 // and don't forget to follow the SRT
4245 // Dynamic bitmap: the mask is stored on the stack, and
4246 // there are a number of non-pointers followed by a number
4247 // of pointers above the bitmapped area. (see StgMacros.h,
4252 dyn = ((StgRetDyn *)p)->liveness;
4254 // traverse the bitmap first
4255 bitmap = RET_DYN_LIVENESS(dyn);
4256 p = (P_)&((StgRetDyn *)p)->payload[0];
4257 size = RET_DYN_BITMAP_SIZE;
4258 p = scavenge_small_bitmap(p, size, bitmap);
4260 // skip over the non-ptr words
4261 p += RET_DYN_NONPTRS(dyn) + RET_DYN_NONPTR_REGS_SIZE;
4263 // follow the ptr words
4264 for (size = RET_DYN_PTRS(dyn); size > 0; size--) {
4265 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
4273 StgRetFun *ret_fun = (StgRetFun *)p;
4274 StgFunInfoTable *fun_info;
4276 ret_fun->fun = evacuate(ret_fun->fun);
4277 fun_info = get_fun_itbl(ret_fun->fun);
4278 p = scavenge_arg_block(fun_info, ret_fun->payload);
4283 barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->i.type));
4288 /*-----------------------------------------------------------------------------
4289 scavenge the large object list.
4291 evac_gen set by caller; similar games played with evac_gen as with
4292 scavenge() - see comment at the top of scavenge(). Most large
4293 objects are (repeatedly) mutable, so most of the time evac_gen will
4295 --------------------------------------------------------------------------- */
4298 scavenge_large(step *stp)
4303 bd = stp->new_large_objects;
4305 for (; bd != NULL; bd = stp->new_large_objects) {
4307 /* take this object *off* the large objects list and put it on
4308 * the scavenged large objects list. This is so that we can
4309 * treat new_large_objects as a stack and push new objects on
4310 * the front when evacuating.
4312 stp->new_large_objects = bd->link;
4313 dbl_link_onto(bd, &stp->scavenged_large_objects);
4315 // update the block count in this step.
4316 stp->n_scavenged_large_blocks += bd->blocks;
4319 if (scavenge_one(p)) {
4320 if (stp->gen_no > 0) {
4321 recordMutableGen((StgClosure *)p, stp->gen);
4327 /* -----------------------------------------------------------------------------
4328 Initialising the static object & mutable lists
4329 -------------------------------------------------------------------------- */
4332 zero_static_object_list(StgClosure* first_static)
4336 const StgInfoTable *info;
4338 for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
4340 link = *STATIC_LINK(info, p);
4341 *STATIC_LINK(info,p) = NULL;
4345 /* -----------------------------------------------------------------------------
4347 -------------------------------------------------------------------------- */
4354 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
4355 c = (StgIndStatic *)c->static_link)
4357 SET_INFO(c, c->saved_info);
4358 c->saved_info = NULL;
4359 // could, but not necessary: c->static_link = NULL;
4361 revertible_caf_list = NULL;
4365 markCAFs( evac_fn evac )
4369 for (c = (StgIndStatic *)caf_list; c != NULL;
4370 c = (StgIndStatic *)c->static_link)
4372 evac(&c->indirectee);
4374 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
4375 c = (StgIndStatic *)c->static_link)
4377 evac(&c->indirectee);
4381 /* -----------------------------------------------------------------------------
4382 Sanity code for CAF garbage collection.
4384 With DEBUG turned on, we manage a CAF list in addition to the SRT
4385 mechanism. After GC, we run down the CAF list and blackhole any
4386 CAFs which have been garbage collected. This means we get an error
4387 whenever the program tries to enter a garbage collected CAF.
4389 Any garbage collected CAFs are taken off the CAF list at the same
4391 -------------------------------------------------------------------------- */
4393 #if 0 && defined(DEBUG)
4400 const StgInfoTable *info;
4411 ASSERT(info->type == IND_STATIC);
4413 if (STATIC_LINK(info,p) == NULL) {
4414 IF_DEBUG(gccafs, debugBelch("CAF gc'd at 0x%04lx", (long)p));
4416 SET_INFO(p,&stg_BLACKHOLE_info);
4417 p = STATIC_LINK2(info,p);
4421 pp = &STATIC_LINK2(info,p);
4428 // debugBelch("%d CAFs live", i);
4433 /* -----------------------------------------------------------------------------
4436 * Code largely pinched from old RTS, then hacked to bits. We also do
4437 * lazy black holing here.
4439 * -------------------------------------------------------------------------- */
4441 struct stack_gap { StgWord gap_size; struct stack_gap *next_gap; };
4444 stackSqueeze(StgTSO *tso, StgPtr bottom)
4447 rtsBool prev_was_update_frame;
4448 StgClosure *updatee = NULL;
4449 StgRetInfoTable *info;
4450 StgWord current_gap_size;
4451 struct stack_gap *gap;
4454 // Traverse the stack upwards, replacing adjacent update frames
4455 // with a single update frame and a "stack gap". A stack gap
4456 // contains two values: the size of the gap, and the distance
4457 // to the next gap (or the stack top).
4461 ASSERT(frame < bottom);
4463 prev_was_update_frame = rtsFalse;
4464 current_gap_size = 0;
4465 gap = (struct stack_gap *) (tso->sp - sizeofW(StgUpdateFrame));
4467 while (frame < bottom) {
4469 info = get_ret_itbl((StgClosure *)frame);
4470 switch (info->i.type) {
4474 StgUpdateFrame *upd = (StgUpdateFrame *)frame;
4476 if (prev_was_update_frame) {
4478 TICK_UPD_SQUEEZED();
4479 /* wasn't there something about update squeezing and ticky to be
4480 * sorted out? oh yes: we aren't counting each enter properly
4481 * in this case. See the log somewhere. KSW 1999-04-21
4483 * Check two things: that the two update frames don't point to
4484 * the same object, and that the updatee_bypass isn't already an
4485 * indirection. Both of these cases only happen when we're in a
4486 * block hole-style loop (and there are multiple update frames
4487 * on the stack pointing to the same closure), but they can both
4488 * screw us up if we don't check.
4490 if (upd->updatee != updatee && !closure_IND(upd->updatee)) {
4491 UPD_IND_NOLOCK(upd->updatee, updatee);
4494 // now mark this update frame as a stack gap. The gap
4495 // marker resides in the bottom-most update frame of
4496 // the series of adjacent frames, and covers all the
4497 // frames in this series.
4498 current_gap_size += sizeofW(StgUpdateFrame);
4499 ((struct stack_gap *)frame)->gap_size = current_gap_size;
4500 ((struct stack_gap *)frame)->next_gap = gap;
4502 frame += sizeofW(StgUpdateFrame);
4506 // single update frame, or the topmost update frame in a series
4508 prev_was_update_frame = rtsTrue;
4509 updatee = upd->updatee;
4510 frame += sizeofW(StgUpdateFrame);
4516 prev_was_update_frame = rtsFalse;
4518 // we're not in a gap... check whether this is the end of a gap
4519 // (an update frame can't be the end of a gap).
4520 if (current_gap_size != 0) {
4521 gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
4523 current_gap_size = 0;
4525 frame += stack_frame_sizeW((StgClosure *)frame);
4530 if (current_gap_size != 0) {
4531 gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
4534 // Now we have a stack with gaps in it, and we have to walk down
4535 // shoving the stack up to fill in the gaps. A diagram might
4539 // | ********* | <- sp
4543 // | stack_gap | <- gap | chunk_size
4545 // | ......... | <- gap_end v
4551 // 'sp' points the the current top-of-stack
4552 // 'gap' points to the stack_gap structure inside the gap
4553 // ***** indicates real stack data
4554 // ..... indicates gap
4555 // <empty> indicates unused
4559 void *gap_start, *next_gap_start, *gap_end;
4562 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4563 sp = next_gap_start;
4565 while ((StgPtr)gap > tso->sp) {
4567 // we're working in *bytes* now...
4568 gap_start = next_gap_start;
4569 gap_end = (void*) ((unsigned char*)gap_start - gap->gap_size * sizeof(W_));
4571 gap = gap->next_gap;
4572 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4574 chunk_size = (unsigned char*)gap_end - (unsigned char*)next_gap_start;
4576 memmove(sp, next_gap_start, chunk_size);
4579 tso->sp = (StgPtr)sp;
4583 /* -----------------------------------------------------------------------------
4586 * We have to prepare for GC - this means doing lazy black holing
4587 * here. We also take the opportunity to do stack squeezing if it's
4589 * -------------------------------------------------------------------------- */
4591 threadPaused(Capability *cap, StgTSO *tso)
4594 StgRetInfoTable *info;
4597 nat words_to_squeeze = 0;
4599 nat weight_pending = 0;
4600 rtsBool prev_was_update_frame;
4602 stack_end = &tso->stack[tso->stack_size];
4604 frame = (StgClosure *)tso->sp;
4607 // If we've already marked this frame, then stop here.
4608 if (frame->header.info == (StgInfoTable *)&stg_marked_upd_frame_info) {
4612 info = get_ret_itbl(frame);
4614 switch (info->i.type) {
4618 SET_INFO(frame, (StgInfoTable *)&stg_marked_upd_frame_info);
4620 bh = ((StgUpdateFrame *)frame)->updatee;
4622 if (closure_IND(bh) || bh->header.info == &stg_BLACKHOLE_info) {
4623 IF_DEBUG(squeeze, debugBelch("suspending duplicate work: %ld words of stack\n", (StgPtr)frame - tso->sp));
4625 // If this closure is already an indirection, then
4626 // suspend the computation up to this point:
4627 suspendComputation(cap,tso,(StgPtr)frame);
4629 // Now drop the update frame, and arrange to return
4630 // the value to the frame underneath:
4631 tso->sp = (StgPtr)frame + sizeofW(StgUpdateFrame) - 2;
4632 tso->sp[1] = (StgWord)bh;
4633 tso->sp[0] = (W_)&stg_enter_info;
4635 // And continue with threadPaused; there might be
4636 // yet more computation to suspend.
4637 threadPaused(cap,tso);
4641 if (bh->header.info != &stg_CAF_BLACKHOLE_info) {
4642 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4643 debugBelch("Unexpected lazy BHing required at 0x%04lx\n",(long)bh);
4645 // zero out the slop so that the sanity checker can tell
4646 // where the next closure is.
4647 DEBUG_FILL_SLOP(bh);
4650 // We pretend that bh is now dead.
4651 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4653 SET_INFO(bh,&stg_BLACKHOLE_info);
4655 // We pretend that bh has just been created.
4656 LDV_RECORD_CREATE(bh);
4659 frame = (StgClosure *) ((StgUpdateFrame *)frame + 1);
4660 if (prev_was_update_frame) {
4661 words_to_squeeze += sizeofW(StgUpdateFrame);
4662 weight += weight_pending;
4665 prev_was_update_frame = rtsTrue;
4671 // normal stack frames; do nothing except advance the pointer
4674 nat frame_size = stack_frame_sizeW(frame);
4675 weight_pending += frame_size;
4676 frame = (StgClosure *)((StgPtr)frame + frame_size);
4677 prev_was_update_frame = rtsFalse;
4684 debugBelch("words_to_squeeze: %d, weight: %d, squeeze: %s\n",
4685 words_to_squeeze, weight,
4686 weight < words_to_squeeze ? "YES" : "NO"));
4688 // Should we squeeze or not? Arbitrary heuristic: we squeeze if
4689 // the number of words we have to shift down is less than the
4690 // number of stack words we squeeze away by doing so.
4691 if (1 /*RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue &&
4692 weight < words_to_squeeze*/) {
4693 stackSqueeze(tso, (StgPtr)frame);
4697 /* -----------------------------------------------------------------------------
4699 * -------------------------------------------------------------------------- */
4703 printMutableList(generation *gen)
4708 debugBelch("@@ Mutable list %p: ", gen->mut_list);
4710 for (bd = gen->mut_list; bd != NULL; bd = bd->link) {
4711 for (p = bd->start; p < bd->free; p++) {
4712 debugBelch("%p (%s), ", (void *)*p, info_type((StgClosure *)*p));