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:
2020 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
2021 return copy(q,THUNK_SELECTOR_sizeW(),stp);
2024 p = eval_thunk_selector(info->layout.selector_offset,
2028 return copy(q,THUNK_SELECTOR_sizeW(),stp);
2031 // q is still BLACKHOLE'd.
2032 thunk_selector_depth++;
2034 thunk_selector_depth--;
2036 // Update the THUNK_SELECTOR with an indirection to the
2037 // EVACUATED closure now at p. Why do this rather than
2038 // upd_evacuee(q,p)? Because we have an invariant that an
2039 // EVACUATED closure always points to an object in the
2040 // same or an older generation (required by the short-cut
2041 // test in the EVACUATED case, below).
2042 SET_INFO(q, &stg_IND_info);
2043 ((StgInd *)q)->indirectee = p;
2046 // We store the size of the just evacuated object in the
2047 // LDV word so that the profiler can guess the position of
2048 // the next object later.
2049 SET_EVACUAEE_FOR_LDV(q, THUNK_SELECTOR_sizeW());
2057 // follow chains of indirections, don't evacuate them
2058 q = ((StgInd*)q)->indirectee;
2070 case CATCH_STM_FRAME:
2071 case CATCH_RETRY_FRAME:
2072 case ATOMICALLY_FRAME:
2073 // shouldn't see these
2074 barf("evacuate: stack frame at %p\n", q);
2077 return copy(q,pap_sizeW((StgPAP*)q),stp);
2080 return copy(q,ap_sizeW((StgAP*)q),stp);
2083 return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp);
2086 /* Already evacuated, just return the forwarding address.
2087 * HOWEVER: if the requested destination generation (evac_gen) is
2088 * older than the actual generation (because the object was
2089 * already evacuated to a younger generation) then we have to
2090 * set the failed_to_evac flag to indicate that we couldn't
2091 * manage to promote the object to the desired generation.
2094 * Optimisation: the check is fairly expensive, but we can often
2095 * shortcut it if either the required generation is 0, or the
2096 * current object (the EVACUATED) is in a high enough generation.
2097 * We know that an EVACUATED always points to an object in the
2098 * same or an older generation. stp is the lowest step that the
2099 * current object would be evacuated to, so we only do the full
2100 * check if stp is too low.
2102 if (evac_gen > 0 && stp->gen_no < evac_gen) { // optimisation
2103 StgClosure *p = ((StgEvacuated*)q)->evacuee;
2104 if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < evac_gen) {
2105 failed_to_evac = rtsTrue;
2106 TICK_GC_FAILED_PROMOTION();
2109 return ((StgEvacuated*)q)->evacuee;
2112 // just copy the block
2113 return copy_noscav(q,arr_words_sizeW((StgArrWords *)q),stp);
2115 case MUT_ARR_PTRS_CLEAN:
2116 case MUT_ARR_PTRS_DIRTY:
2117 case MUT_ARR_PTRS_FROZEN:
2118 case MUT_ARR_PTRS_FROZEN0:
2119 // just copy the block
2120 return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
2124 StgTSO *tso = (StgTSO *)q;
2126 /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
2128 if (tso->what_next == ThreadRelocated) {
2129 q = (StgClosure *)tso->link;
2133 /* To evacuate a small TSO, we need to relocate the update frame
2140 new_tso = (StgTSO *)copyPart((StgClosure *)tso,
2142 sizeofW(StgTSO), stp);
2143 move_TSO(tso, new_tso);
2144 for (p = tso->sp, q = new_tso->sp;
2145 p < tso->stack+tso->stack_size;) {
2149 return (StgClosure *)new_tso;
2156 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
2157 to = copy(q,BLACKHOLE_sizeW(),stp);
2158 //ToDo: derive size etc from reverted IP
2159 //to = copy(q,size,stp);
2161 debugBelch("@@ evacuate: RBH %p (%s) to %p (%s)",
2162 q, info_type(q), to, info_type(to)));
2167 ASSERT(sizeofW(StgBlockedFetch) >= MIN_PAYLOD_SIZE);
2168 to = copy(q,sizeofW(StgBlockedFetch),stp);
2170 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
2171 q, info_type(q), to, info_type(to)));
2178 ASSERT(sizeofW(StgBlockedFetch) >= MIN_PAYLOAD_SIZE);
2179 to = copy(q,sizeofW(StgFetchMe),stp);
2181 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
2182 q, info_type(q), to, info_type(to)));
2186 ASSERT(sizeofW(StgBlockedFetch) >= MIN_PAYLOAD_SIZE);
2187 to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
2189 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
2190 q, info_type(q), to, info_type(to)));
2195 return copy(q,sizeofW(StgTRecHeader),stp);
2197 case TVAR_WAIT_QUEUE:
2198 return copy(q,sizeofW(StgTVarWaitQueue),stp);
2201 return copy(q,sizeofW(StgTVar),stp);
2204 return copy(q,sizeofW(StgTRecChunk),stp);
2207 barf("evacuate: strange closure type %d", (int)(info->type));
2213 /* -----------------------------------------------------------------------------
2214 Evaluate a THUNK_SELECTOR if possible.
2216 returns: NULL if we couldn't evaluate this THUNK_SELECTOR, or
2217 a closure pointer if we evaluated it and this is the result. Note
2218 that "evaluating" the THUNK_SELECTOR doesn't necessarily mean
2219 reducing it to HNF, just that we have eliminated the selection.
2220 The result might be another thunk, or even another THUNK_SELECTOR.
2222 If the return value is non-NULL, the original selector thunk has
2223 been BLACKHOLE'd, and should be updated with an indirection or a
2224 forwarding pointer. If the return value is NULL, then the selector
2228 ToDo: the treatment of THUNK_SELECTORS could be improved in the
2229 following way (from a suggestion by Ian Lynagh):
2231 We can have a chain like this:
2235 |-----> sel_0 --> (a,b)
2237 |-----> sel_0 --> ...
2239 and the depth limit means we don't go all the way to the end of the
2240 chain, which results in a space leak. This affects the recursive
2241 call to evacuate() in the THUNK_SELECTOR case in evacuate(): *not*
2242 the recursive call to eval_thunk_selector() in
2243 eval_thunk_selector().
2245 We could eliminate the depth bound in this case, in the following
2248 - traverse the chain once to discover the *value* of the
2249 THUNK_SELECTOR. Mark all THUNK_SELECTORS that we
2250 visit on the way as having been visited already (somehow).
2252 - in a second pass, traverse the chain again updating all
2253 THUNK_SEELCTORS that we find on the way with indirections to
2256 - if we encounter a "marked" THUNK_SELECTOR in a normal
2257 evacuate(), we konw it can't be updated so just evac it.
2259 Program that illustrates the problem:
2262 foo (x:xs) = let (ys, zs) = foo xs
2263 in if x >= 0 then (x:ys, zs) else (ys, x:zs)
2265 main = bar [1..(100000000::Int)]
2266 bar xs = (\(ys, zs) -> print ys >> print zs) (foo xs)
2268 -------------------------------------------------------------------------- */
2270 static inline rtsBool
2271 is_to_space ( StgClosure *p )
2275 bd = Bdescr((StgPtr)p);
2276 if (HEAP_ALLOCED(p) &&
2277 ((bd->flags & BF_EVACUATED)
2278 || ((bd->flags & BF_COMPACTED) &&
2279 is_marked((P_)p,bd)))) {
2287 eval_thunk_selector( nat field, StgSelector * p )
2290 const StgInfoTable *info_ptr;
2291 StgClosure *selectee;
2293 selectee = p->selectee;
2295 // Save the real info pointer (NOTE: not the same as get_itbl()).
2296 info_ptr = p->header.info;
2298 // If the THUNK_SELECTOR is in a generation that we are not
2299 // collecting, then bail out early. We won't be able to save any
2300 // space in any case, and updating with an indirection is trickier
2302 if (Bdescr((StgPtr)p)->gen_no > N) {
2306 // BLACKHOLE the selector thunk, since it is now under evaluation.
2307 // This is important to stop us going into an infinite loop if
2308 // this selector thunk eventually refers to itself.
2309 SET_INFO(p,&stg_BLACKHOLE_info);
2313 // We don't want to end up in to-space, because this causes
2314 // problems when the GC later tries to evacuate the result of
2315 // eval_thunk_selector(). There are various ways this could
2318 // 1. following an IND_STATIC
2320 // 2. when the old generation is compacted, the mark phase updates
2321 // from-space pointers to be to-space pointers, and we can't
2322 // reliably tell which we're following (eg. from an IND_STATIC).
2324 // 3. compacting GC again: if we're looking at a constructor in
2325 // the compacted generation, it might point directly to objects
2326 // in to-space. We must bale out here, otherwise doing the selection
2327 // will result in a to-space pointer being returned.
2329 // (1) is dealt with using a BF_EVACUATED test on the
2330 // selectee. (2) and (3): we can tell if we're looking at an
2331 // object in the compacted generation that might point to
2332 // to-space objects by testing that (a) it is BF_COMPACTED, (b)
2333 // the compacted generation is being collected, and (c) the
2334 // object is marked. Only a marked object may have pointers that
2335 // point to to-space objects, because that happens when
2338 // The to-space test is now embodied in the in_to_space() inline
2339 // function, as it is re-used below.
2341 if (is_to_space(selectee)) {
2345 info = get_itbl(selectee);
2346 switch (info->type) {
2354 case CONSTR_NOCAF_STATIC:
2355 // check that the size is in range
2356 ASSERT(field < (StgWord32)(info->layout.payload.ptrs +
2357 info->layout.payload.nptrs));
2359 // Select the right field from the constructor, and check
2360 // that the result isn't in to-space. It might be in
2361 // to-space if, for example, this constructor contains
2362 // pointers to younger-gen objects (and is on the mut-once
2367 q = selectee->payload[field];
2368 if (is_to_space(q)) {
2378 case IND_OLDGEN_PERM:
2380 selectee = ((StgInd *)selectee)->indirectee;
2384 // We don't follow pointers into to-space; the constructor
2385 // has already been evacuated, so we won't save any space
2386 // leaks by evaluating this selector thunk anyhow.
2389 case THUNK_SELECTOR:
2393 // check that we don't recurse too much, re-using the
2394 // depth bound also used in evacuate().
2395 if (thunk_selector_depth >= MAX_THUNK_SELECTOR_DEPTH) {
2398 thunk_selector_depth++;
2400 val = eval_thunk_selector(info->layout.selector_offset,
2401 (StgSelector *)selectee);
2403 thunk_selector_depth--;
2408 // We evaluated this selector thunk, so update it with
2409 // an indirection. NOTE: we don't use UPD_IND here,
2410 // because we are guaranteed that p is in a generation
2411 // that we are collecting, and we never want to put the
2412 // indirection on a mutable list.
2414 // For the purposes of LDV profiling, we have destroyed
2415 // the original selector thunk.
2416 SET_INFO(p, info_ptr);
2417 LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(selectee);
2419 ((StgInd *)selectee)->indirectee = val;
2420 SET_INFO(selectee,&stg_IND_info);
2422 // For the purposes of LDV profiling, we have created an
2424 LDV_RECORD_CREATE(selectee);
2441 case SE_CAF_BLACKHOLE:
2453 // not evaluated yet
2457 barf("eval_thunk_selector: strange selectee %d",
2462 // We didn't manage to evaluate this thunk; restore the old info pointer
2463 SET_INFO(p, info_ptr);
2467 /* -----------------------------------------------------------------------------
2468 move_TSO is called to update the TSO structure after it has been
2469 moved from one place to another.
2470 -------------------------------------------------------------------------- */
2473 move_TSO (StgTSO *src, StgTSO *dest)
2477 // relocate the stack pointer...
2478 diff = (StgPtr)dest - (StgPtr)src; // In *words*
2479 dest->sp = (StgPtr)dest->sp + diff;
2482 /* Similar to scavenge_large_bitmap(), but we don't write back the
2483 * pointers we get back from evacuate().
2486 scavenge_large_srt_bitmap( StgLargeSRT *large_srt )
2493 bitmap = large_srt->l.bitmap[b];
2494 size = (nat)large_srt->l.size;
2495 p = (StgClosure **)large_srt->srt;
2496 for (i = 0; i < size; ) {
2497 if ((bitmap & 1) != 0) {
2502 if (i % BITS_IN(W_) == 0) {
2504 bitmap = large_srt->l.bitmap[b];
2506 bitmap = bitmap >> 1;
2511 /* evacuate the SRT. If srt_bitmap is zero, then there isn't an
2512 * srt field in the info table. That's ok, because we'll
2513 * never dereference it.
2516 scavenge_srt (StgClosure **srt, nat srt_bitmap)
2521 bitmap = srt_bitmap;
2524 if (bitmap == (StgHalfWord)(-1)) {
2525 scavenge_large_srt_bitmap( (StgLargeSRT *)srt );
2529 while (bitmap != 0) {
2530 if ((bitmap & 1) != 0) {
2531 #ifdef ENABLE_WIN32_DLL_SUPPORT
2532 // Special-case to handle references to closures hiding out in DLLs, since
2533 // double indirections required to get at those. The code generator knows
2534 // which is which when generating the SRT, so it stores the (indirect)
2535 // reference to the DLL closure in the table by first adding one to it.
2536 // We check for this here, and undo the addition before evacuating it.
2538 // If the SRT entry hasn't got bit 0 set, the SRT entry points to a
2539 // closure that's fixed at link-time, and no extra magic is required.
2540 if ( (unsigned long)(*srt) & 0x1 ) {
2541 evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
2550 bitmap = bitmap >> 1;
2556 scavenge_thunk_srt(const StgInfoTable *info)
2558 StgThunkInfoTable *thunk_info;
2560 if (!major_gc) return;
2562 thunk_info = itbl_to_thunk_itbl(info);
2563 scavenge_srt((StgClosure **)GET_SRT(thunk_info), thunk_info->i.srt_bitmap);
2567 scavenge_fun_srt(const StgInfoTable *info)
2569 StgFunInfoTable *fun_info;
2571 if (!major_gc) return;
2573 fun_info = itbl_to_fun_itbl(info);
2574 scavenge_srt((StgClosure **)GET_FUN_SRT(fun_info), fun_info->i.srt_bitmap);
2577 /* -----------------------------------------------------------------------------
2579 -------------------------------------------------------------------------- */
2582 scavengeTSO (StgTSO *tso)
2584 if ( tso->why_blocked == BlockedOnMVar
2585 || tso->why_blocked == BlockedOnBlackHole
2586 || tso->why_blocked == BlockedOnException
2588 || tso->why_blocked == BlockedOnGA
2589 || tso->why_blocked == BlockedOnGA_NoSend
2592 tso->block_info.closure = evacuate(tso->block_info.closure);
2594 if ( tso->blocked_exceptions != NULL ) {
2595 tso->blocked_exceptions =
2596 (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
2599 // We don't always chase the link field: TSOs on the blackhole
2600 // queue are not automatically alive, so the link field is a
2601 // "weak" pointer in that case.
2602 if (tso->why_blocked != BlockedOnBlackHole) {
2603 tso->link = (StgTSO *)evacuate((StgClosure *)tso->link);
2606 // scavange current transaction record
2607 tso->trec = (StgTRecHeader *)evacuate((StgClosure *)tso->trec);
2609 // scavenge this thread's stack
2610 scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
2613 /* -----------------------------------------------------------------------------
2614 Blocks of function args occur on the stack (at the top) and
2616 -------------------------------------------------------------------------- */
2618 STATIC_INLINE StgPtr
2619 scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
2626 switch (fun_info->f.fun_type) {
2628 bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
2629 size = BITMAP_SIZE(fun_info->f.b.bitmap);
2632 size = GET_FUN_LARGE_BITMAP(fun_info)->size;
2633 scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
2637 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2638 size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->f.fun_type]);
2641 if ((bitmap & 1) == 0) {
2642 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2645 bitmap = bitmap >> 1;
2653 STATIC_INLINE StgPtr
2654 scavenge_PAP_payload (StgClosure *fun, StgClosure **payload, StgWord size)
2658 StgFunInfoTable *fun_info;
2660 fun_info = get_fun_itbl(fun);
2661 ASSERT(fun_info->i.type != PAP);
2662 p = (StgPtr)payload;
2664 switch (fun_info->f.fun_type) {
2666 bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
2669 scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
2673 scavenge_large_bitmap((StgPtr)payload, BCO_BITMAP(fun), size);
2677 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2680 if ((bitmap & 1) == 0) {
2681 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2684 bitmap = bitmap >> 1;
2692 STATIC_INLINE StgPtr
2693 scavenge_PAP (StgPAP *pap)
2695 pap->fun = evacuate(pap->fun);
2696 return scavenge_PAP_payload (pap->fun, pap->payload, pap->n_args);
2699 STATIC_INLINE StgPtr
2700 scavenge_AP (StgAP *ap)
2702 ap->fun = evacuate(ap->fun);
2703 return scavenge_PAP_payload (ap->fun, ap->payload, ap->n_args);
2706 /* -----------------------------------------------------------------------------
2707 Scavenge a given step until there are no more objects in this step
2710 evac_gen is set by the caller to be either zero (for a step in a
2711 generation < N) or G where G is the generation of the step being
2714 We sometimes temporarily change evac_gen back to zero if we're
2715 scavenging a mutable object where early promotion isn't such a good
2717 -------------------------------------------------------------------------- */
2725 nat saved_evac_gen = evac_gen;
2730 failed_to_evac = rtsFalse;
2732 /* scavenge phase - standard breadth-first scavenging of the
2736 while (bd != stp->hp_bd || p < stp->hp) {
2738 // If we're at the end of this block, move on to the next block
2739 if (bd != stp->hp_bd && p == bd->free) {
2745 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2746 info = get_itbl((StgClosure *)p);
2748 ASSERT(thunk_selector_depth == 0);
2751 switch (info->type) {
2755 StgMVar *mvar = ((StgMVar *)p);
2757 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
2758 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
2759 mvar->value = evacuate((StgClosure *)mvar->value);
2760 evac_gen = saved_evac_gen;
2761 failed_to_evac = rtsTrue; // mutable.
2762 p += sizeofW(StgMVar);
2767 scavenge_fun_srt(info);
2768 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2769 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2770 p += sizeofW(StgHeader) + 2;
2774 scavenge_thunk_srt(info);
2775 ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
2776 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2777 p += sizeofW(StgThunk) + 2;
2781 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2782 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2783 p += sizeofW(StgHeader) + 2;
2787 scavenge_thunk_srt(info);
2788 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2789 p += sizeofW(StgThunk) + 1;
2793 scavenge_fun_srt(info);
2795 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2796 p += sizeofW(StgHeader) + 1;
2800 scavenge_thunk_srt(info);
2801 p += sizeofW(StgThunk) + 1;
2805 scavenge_fun_srt(info);
2807 p += sizeofW(StgHeader) + 1;
2811 scavenge_thunk_srt(info);
2812 p += sizeofW(StgThunk) + 2;
2816 scavenge_fun_srt(info);
2818 p += sizeofW(StgHeader) + 2;
2822 scavenge_thunk_srt(info);
2823 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2824 p += sizeofW(StgThunk) + 2;
2828 scavenge_fun_srt(info);
2830 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2831 p += sizeofW(StgHeader) + 2;
2835 scavenge_fun_srt(info);
2842 scavenge_thunk_srt(info);
2843 end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
2844 for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
2845 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2847 p += info->layout.payload.nptrs;
2858 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2859 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2860 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2862 p += info->layout.payload.nptrs;
2867 StgBCO *bco = (StgBCO *)p;
2868 bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
2869 bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
2870 bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
2871 bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
2872 p += bco_sizeW(bco);
2877 if (stp->gen->no != 0) {
2880 // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an
2881 // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
2882 LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
2885 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
2887 SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
2889 // We pretend that p has just been created.
2890 LDV_RECORD_CREATE((StgClosure *)p);
2893 case IND_OLDGEN_PERM:
2894 ((StgInd *)p)->indirectee = evacuate(((StgInd *)p)->indirectee);
2895 p += sizeofW(StgInd);
2899 case MUT_VAR_DIRTY: {
2900 rtsBool saved_eager_promotion = eager_promotion;
2902 eager_promotion = rtsFalse;
2903 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2904 eager_promotion = saved_eager_promotion;
2906 if (failed_to_evac) {
2907 ((StgClosure *)q)->header.info = &stg_MUT_VAR_DIRTY_info;
2909 ((StgClosure *)q)->header.info = &stg_MUT_VAR_CLEAN_info;
2911 p += sizeofW(StgMutVar);
2916 case SE_CAF_BLACKHOLE:
2919 p += BLACKHOLE_sizeW();
2922 case THUNK_SELECTOR:
2924 StgSelector *s = (StgSelector *)p;
2925 s->selectee = evacuate(s->selectee);
2926 p += THUNK_SELECTOR_sizeW();
2930 // A chunk of stack saved in a heap object
2933 StgAP_STACK *ap = (StgAP_STACK *)p;
2935 ap->fun = evacuate(ap->fun);
2936 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2937 p = (StgPtr)ap->payload + ap->size;
2942 p = scavenge_PAP((StgPAP *)p);
2946 p = scavenge_AP((StgAP *)p);
2950 // nothing to follow
2951 p += arr_words_sizeW((StgArrWords *)p);
2954 case MUT_ARR_PTRS_CLEAN:
2955 case MUT_ARR_PTRS_DIRTY:
2956 // follow everything
2959 rtsBool saved_eager;
2961 // We don't eagerly promote objects pointed to by a mutable
2962 // array, but if we find the array only points to objects in
2963 // the same or an older generation, we mark it "clean" and
2964 // avoid traversing it during minor GCs.
2965 saved_eager = eager_promotion;
2966 eager_promotion = rtsFalse;
2967 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2968 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2969 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2971 eager_promotion = saved_eager;
2973 if (failed_to_evac) {
2974 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
2976 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
2979 failed_to_evac = rtsTrue; // always put it on the mutable list.
2983 case MUT_ARR_PTRS_FROZEN:
2984 case MUT_ARR_PTRS_FROZEN0:
2985 // follow everything
2989 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2990 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2991 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2994 // If we're going to put this object on the mutable list, then
2995 // set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that.
2996 if (failed_to_evac) {
2997 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info;
2999 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info;
3006 StgTSO *tso = (StgTSO *)p;
3007 rtsBool saved_eager = eager_promotion;
3009 eager_promotion = rtsFalse;
3011 eager_promotion = saved_eager;
3013 if (failed_to_evac) {
3014 tso->flags |= TSO_DIRTY;
3016 tso->flags &= ~TSO_DIRTY;
3019 failed_to_evac = rtsTrue; // always on the mutable list
3020 p += tso_sizeW(tso);
3028 nat size, ptrs, nonptrs, vhs;
3030 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3032 StgRBH *rbh = (StgRBH *)p;
3033 (StgClosure *)rbh->blocking_queue =
3034 evacuate((StgClosure *)rbh->blocking_queue);
3035 failed_to_evac = rtsTrue; // mutable anyhow.
3037 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3038 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3039 // ToDo: use size of reverted closure here!
3040 p += BLACKHOLE_sizeW();
3046 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3047 // follow the pointer to the node which is being demanded
3048 (StgClosure *)bf->node =
3049 evacuate((StgClosure *)bf->node);
3050 // follow the link to the rest of the blocking queue
3051 (StgClosure *)bf->link =
3052 evacuate((StgClosure *)bf->link);
3054 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3055 bf, info_type((StgClosure *)bf),
3056 bf->node, info_type(bf->node)));
3057 p += sizeofW(StgBlockedFetch);
3065 p += sizeofW(StgFetchMe);
3066 break; // nothing to do in this case
3070 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3071 (StgClosure *)fmbq->blocking_queue =
3072 evacuate((StgClosure *)fmbq->blocking_queue);
3074 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3075 p, info_type((StgClosure *)p)));
3076 p += sizeofW(StgFetchMeBlockingQueue);
3081 case TVAR_WAIT_QUEUE:
3083 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3085 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3086 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3087 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3088 evac_gen = saved_evac_gen;
3089 failed_to_evac = rtsTrue; // mutable
3090 p += sizeofW(StgTVarWaitQueue);
3096 StgTVar *tvar = ((StgTVar *) p);
3098 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3099 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3100 evac_gen = saved_evac_gen;
3101 failed_to_evac = rtsTrue; // mutable
3102 p += sizeofW(StgTVar);
3108 StgTRecHeader *trec = ((StgTRecHeader *) p);
3110 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3111 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3112 evac_gen = saved_evac_gen;
3113 failed_to_evac = rtsTrue; // mutable
3114 p += sizeofW(StgTRecHeader);
3121 StgTRecChunk *tc = ((StgTRecChunk *) p);
3122 TRecEntry *e = &(tc -> entries[0]);
3124 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3125 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3126 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3127 e->expected_value = evacuate((StgClosure*)e->expected_value);
3128 e->new_value = evacuate((StgClosure*)e->new_value);
3130 evac_gen = saved_evac_gen;
3131 failed_to_evac = rtsTrue; // mutable
3132 p += sizeofW(StgTRecChunk);
3137 barf("scavenge: unimplemented/strange closure type %d @ %p",
3142 * We need to record the current object on the mutable list if
3143 * (a) It is actually mutable, or
3144 * (b) It contains pointers to a younger generation.
3145 * Case (b) arises if we didn't manage to promote everything that
3146 * the current object points to into the current generation.
3148 if (failed_to_evac) {
3149 failed_to_evac = rtsFalse;
3150 if (stp->gen_no > 0) {
3151 recordMutableGen((StgClosure *)q, stp->gen);
3160 /* -----------------------------------------------------------------------------
3161 Scavenge everything on the mark stack.
3163 This is slightly different from scavenge():
3164 - we don't walk linearly through the objects, so the scavenger
3165 doesn't need to advance the pointer on to the next object.
3166 -------------------------------------------------------------------------- */
3169 scavenge_mark_stack(void)
3175 evac_gen = oldest_gen->no;
3176 saved_evac_gen = evac_gen;
3179 while (!mark_stack_empty()) {
3180 p = pop_mark_stack();
3182 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3183 info = get_itbl((StgClosure *)p);
3186 switch (info->type) {
3190 StgMVar *mvar = ((StgMVar *)p);
3192 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
3193 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
3194 mvar->value = evacuate((StgClosure *)mvar->value);
3195 evac_gen = saved_evac_gen;
3196 failed_to_evac = rtsTrue; // mutable.
3201 scavenge_fun_srt(info);
3202 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
3203 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3207 scavenge_thunk_srt(info);
3208 ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
3209 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
3213 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
3214 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3219 scavenge_fun_srt(info);
3220 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3225 scavenge_thunk_srt(info);
3226 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
3231 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3236 scavenge_fun_srt(info);
3241 scavenge_thunk_srt(info);
3249 scavenge_fun_srt(info);
3256 scavenge_thunk_srt(info);
3257 end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
3258 for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
3259 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3271 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3272 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
3273 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3279 StgBCO *bco = (StgBCO *)p;
3280 bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
3281 bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
3282 bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
3283 bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
3288 // don't need to do anything here: the only possible case
3289 // is that we're in a 1-space compacting collector, with
3290 // no "old" generation.
3294 case IND_OLDGEN_PERM:
3295 ((StgInd *)p)->indirectee =
3296 evacuate(((StgInd *)p)->indirectee);
3300 case MUT_VAR_DIRTY: {
3301 rtsBool saved_eager_promotion = eager_promotion;
3303 eager_promotion = rtsFalse;
3304 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3305 eager_promotion = saved_eager_promotion;
3307 if (failed_to_evac) {
3308 ((StgClosure *)q)->header.info = &stg_MUT_VAR_DIRTY_info;
3310 ((StgClosure *)q)->header.info = &stg_MUT_VAR_CLEAN_info;
3316 case SE_CAF_BLACKHOLE:
3322 case THUNK_SELECTOR:
3324 StgSelector *s = (StgSelector *)p;
3325 s->selectee = evacuate(s->selectee);
3329 // A chunk of stack saved in a heap object
3332 StgAP_STACK *ap = (StgAP_STACK *)p;
3334 ap->fun = evacuate(ap->fun);
3335 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3340 scavenge_PAP((StgPAP *)p);
3344 scavenge_AP((StgAP *)p);
3347 case MUT_ARR_PTRS_CLEAN:
3348 case MUT_ARR_PTRS_DIRTY:
3349 // follow everything
3352 rtsBool saved_eager;
3354 // We don't eagerly promote objects pointed to by a mutable
3355 // array, but if we find the array only points to objects in
3356 // the same or an older generation, we mark it "clean" and
3357 // avoid traversing it during minor GCs.
3358 saved_eager = eager_promotion;
3359 eager_promotion = rtsFalse;
3360 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3361 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3362 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3364 eager_promotion = saved_eager;
3366 if (failed_to_evac) {
3367 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
3369 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
3372 failed_to_evac = rtsTrue; // mutable anyhow.
3376 case MUT_ARR_PTRS_FROZEN:
3377 case MUT_ARR_PTRS_FROZEN0:
3378 // follow everything
3382 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3383 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3384 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3387 // If we're going to put this object on the mutable list, then
3388 // set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that.
3389 if (failed_to_evac) {
3390 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info;
3392 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info;
3399 StgTSO *tso = (StgTSO *)p;
3400 rtsBool saved_eager = eager_promotion;
3402 eager_promotion = rtsFalse;
3404 eager_promotion = saved_eager;
3406 if (failed_to_evac) {
3407 tso->flags |= TSO_DIRTY;
3409 tso->flags &= ~TSO_DIRTY;
3412 failed_to_evac = rtsTrue; // always on the mutable list
3420 nat size, ptrs, nonptrs, vhs;
3422 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3424 StgRBH *rbh = (StgRBH *)p;
3425 bh->blocking_queue =
3426 (StgTSO *)evacuate((StgClosure *)bh->blocking_queue);
3427 failed_to_evac = rtsTrue; // mutable anyhow.
3429 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3430 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3436 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3437 // follow the pointer to the node which is being demanded
3438 (StgClosure *)bf->node =
3439 evacuate((StgClosure *)bf->node);
3440 // follow the link to the rest of the blocking queue
3441 (StgClosure *)bf->link =
3442 evacuate((StgClosure *)bf->link);
3444 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3445 bf, info_type((StgClosure *)bf),
3446 bf->node, info_type(bf->node)));
3454 break; // nothing to do in this case
3458 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3459 (StgClosure *)fmbq->blocking_queue =
3460 evacuate((StgClosure *)fmbq->blocking_queue);
3462 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3463 p, info_type((StgClosure *)p)));
3468 case TVAR_WAIT_QUEUE:
3470 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3472 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3473 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3474 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3475 evac_gen = saved_evac_gen;
3476 failed_to_evac = rtsTrue; // mutable
3482 StgTVar *tvar = ((StgTVar *) p);
3484 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3485 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3486 evac_gen = saved_evac_gen;
3487 failed_to_evac = rtsTrue; // mutable
3494 StgTRecChunk *tc = ((StgTRecChunk *) p);
3495 TRecEntry *e = &(tc -> entries[0]);
3497 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3498 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3499 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3500 e->expected_value = evacuate((StgClosure*)e->expected_value);
3501 e->new_value = evacuate((StgClosure*)e->new_value);
3503 evac_gen = saved_evac_gen;
3504 failed_to_evac = rtsTrue; // mutable
3510 StgTRecHeader *trec = ((StgTRecHeader *) p);
3512 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3513 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3514 evac_gen = saved_evac_gen;
3515 failed_to_evac = rtsTrue; // mutable
3520 barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p",
3524 if (failed_to_evac) {
3525 failed_to_evac = rtsFalse;
3527 recordMutableGen((StgClosure *)q, &generations[evac_gen]);
3531 // mark the next bit to indicate "scavenged"
3532 mark(q+1, Bdescr(q));
3534 } // while (!mark_stack_empty())
3536 // start a new linear scan if the mark stack overflowed at some point
3537 if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
3538 IF_DEBUG(gc, debugBelch("scavenge_mark_stack: starting linear scan"));
3539 mark_stack_overflowed = rtsFalse;
3540 oldgen_scan_bd = oldest_gen->steps[0].old_blocks;
3541 oldgen_scan = oldgen_scan_bd->start;
3544 if (oldgen_scan_bd) {
3545 // push a new thing on the mark stack
3547 // find a closure that is marked but not scavenged, and start
3549 while (oldgen_scan < oldgen_scan_bd->free
3550 && !is_marked(oldgen_scan,oldgen_scan_bd)) {
3554 if (oldgen_scan < oldgen_scan_bd->free) {
3556 // already scavenged?
3557 if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
3558 oldgen_scan += sizeofW(StgHeader) + MIN_PAYLOAD_SIZE;
3561 push_mark_stack(oldgen_scan);
3562 // ToDo: bump the linear scan by the actual size of the object
3563 oldgen_scan += sizeofW(StgHeader) + MIN_PAYLOAD_SIZE;
3567 oldgen_scan_bd = oldgen_scan_bd->link;
3568 if (oldgen_scan_bd != NULL) {
3569 oldgen_scan = oldgen_scan_bd->start;
3575 /* -----------------------------------------------------------------------------
3576 Scavenge one object.
3578 This is used for objects that are temporarily marked as mutable
3579 because they contain old-to-new generation pointers. Only certain
3580 objects can have this property.
3581 -------------------------------------------------------------------------- */
3584 scavenge_one(StgPtr p)
3586 const StgInfoTable *info;
3587 nat saved_evac_gen = evac_gen;
3590 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3591 info = get_itbl((StgClosure *)p);
3593 switch (info->type) {
3597 StgMVar *mvar = ((StgMVar *)p);
3599 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
3600 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
3601 mvar->value = evacuate((StgClosure *)mvar->value);
3602 evac_gen = saved_evac_gen;
3603 failed_to_evac = rtsTrue; // mutable.
3616 end = (StgPtr)((StgThunk *)p)->payload + info->layout.payload.ptrs;
3617 for (q = (StgPtr)((StgThunk *)p)->payload; q < end; q++) {
3618 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3624 case FUN_1_0: // hardly worth specialising these guys
3640 end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3641 for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
3642 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3648 case MUT_VAR_DIRTY: {
3650 rtsBool saved_eager_promotion = eager_promotion;
3652 eager_promotion = rtsFalse;
3653 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3654 eager_promotion = saved_eager_promotion;
3656 if (failed_to_evac) {
3657 ((StgClosure *)q)->header.info = &stg_MUT_VAR_DIRTY_info;
3659 ((StgClosure *)q)->header.info = &stg_MUT_VAR_CLEAN_info;
3665 case SE_CAF_BLACKHOLE:
3670 case THUNK_SELECTOR:
3672 StgSelector *s = (StgSelector *)p;
3673 s->selectee = evacuate(s->selectee);
3679 StgAP_STACK *ap = (StgAP_STACK *)p;
3681 ap->fun = evacuate(ap->fun);
3682 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3683 p = (StgPtr)ap->payload + ap->size;
3688 p = scavenge_PAP((StgPAP *)p);
3692 p = scavenge_AP((StgAP *)p);
3696 // nothing to follow
3699 case MUT_ARR_PTRS_CLEAN:
3700 case MUT_ARR_PTRS_DIRTY:
3703 rtsBool saved_eager;
3705 // We don't eagerly promote objects pointed to by a mutable
3706 // array, but if we find the array only points to objects in
3707 // the same or an older generation, we mark it "clean" and
3708 // avoid traversing it during minor GCs.
3709 saved_eager = eager_promotion;
3710 eager_promotion = rtsFalse;
3712 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3713 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3714 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3716 eager_promotion = saved_eager;
3718 if (failed_to_evac) {
3719 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
3721 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
3724 failed_to_evac = rtsTrue;
3728 case MUT_ARR_PTRS_FROZEN:
3729 case MUT_ARR_PTRS_FROZEN0:
3731 // follow everything
3734 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3735 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3736 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3739 // If we're going to put this object on the mutable list, then
3740 // set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that.
3741 if (failed_to_evac) {
3742 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info;
3744 ((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info;
3751 StgTSO *tso = (StgTSO *)p;
3752 rtsBool saved_eager = eager_promotion;
3754 eager_promotion = rtsFalse;
3756 eager_promotion = saved_eager;
3758 if (failed_to_evac) {
3759 tso->flags |= TSO_DIRTY;
3761 tso->flags &= ~TSO_DIRTY;
3764 failed_to_evac = rtsTrue; // always on the mutable list
3772 nat size, ptrs, nonptrs, vhs;
3774 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3776 StgRBH *rbh = (StgRBH *)p;
3777 (StgClosure *)rbh->blocking_queue =
3778 evacuate((StgClosure *)rbh->blocking_queue);
3779 failed_to_evac = rtsTrue; // mutable anyhow.
3781 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3782 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3783 // ToDo: use size of reverted closure here!
3789 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3790 // follow the pointer to the node which is being demanded
3791 (StgClosure *)bf->node =
3792 evacuate((StgClosure *)bf->node);
3793 // follow the link to the rest of the blocking queue
3794 (StgClosure *)bf->link =
3795 evacuate((StgClosure *)bf->link);
3797 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3798 bf, info_type((StgClosure *)bf),
3799 bf->node, info_type(bf->node)));
3807 break; // nothing to do in this case
3811 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3812 (StgClosure *)fmbq->blocking_queue =
3813 evacuate((StgClosure *)fmbq->blocking_queue);
3815 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3816 p, info_type((StgClosure *)p)));
3821 case TVAR_WAIT_QUEUE:
3823 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3825 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3826 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3827 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3828 evac_gen = saved_evac_gen;
3829 failed_to_evac = rtsTrue; // mutable
3835 StgTVar *tvar = ((StgTVar *) p);
3837 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3838 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3839 evac_gen = saved_evac_gen;
3840 failed_to_evac = rtsTrue; // mutable
3846 StgTRecHeader *trec = ((StgTRecHeader *) p);
3848 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3849 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3850 evac_gen = saved_evac_gen;
3851 failed_to_evac = rtsTrue; // mutable
3858 StgTRecChunk *tc = ((StgTRecChunk *) p);
3859 TRecEntry *e = &(tc -> entries[0]);
3861 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3862 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3863 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3864 e->expected_value = evacuate((StgClosure*)e->expected_value);
3865 e->new_value = evacuate((StgClosure*)e->new_value);
3867 evac_gen = saved_evac_gen;
3868 failed_to_evac = rtsTrue; // mutable
3873 case IND_OLDGEN_PERM:
3876 /* Careful here: a THUNK can be on the mutable list because
3877 * it contains pointers to young gen objects. If such a thunk
3878 * is updated, the IND_OLDGEN will be added to the mutable
3879 * list again, and we'll scavenge it twice. evacuate()
3880 * doesn't check whether the object has already been
3881 * evacuated, so we perform that check here.
3883 StgClosure *q = ((StgInd *)p)->indirectee;
3884 if (HEAP_ALLOCED(q) && Bdescr((StgPtr)q)->flags & BF_EVACUATED) {
3887 ((StgInd *)p)->indirectee = evacuate(q);
3890 #if 0 && defined(DEBUG)
3891 if (RtsFlags.DebugFlags.gc)
3892 /* Debugging code to print out the size of the thing we just
3896 StgPtr start = gen->steps[0].scan;
3897 bdescr *start_bd = gen->steps[0].scan_bd;
3899 scavenge(&gen->steps[0]);
3900 if (start_bd != gen->steps[0].scan_bd) {
3901 size += (P_)BLOCK_ROUND_UP(start) - start;
3902 start_bd = start_bd->link;
3903 while (start_bd != gen->steps[0].scan_bd) {
3904 size += BLOCK_SIZE_W;
3905 start_bd = start_bd->link;
3907 size += gen->steps[0].scan -
3908 (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
3910 size = gen->steps[0].scan - start;
3912 debugBelch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
3918 barf("scavenge_one: strange object %d", (int)(info->type));
3921 no_luck = failed_to_evac;
3922 failed_to_evac = rtsFalse;
3926 /* -----------------------------------------------------------------------------
3927 Scavenging mutable lists.
3929 We treat the mutable list of each generation > N (i.e. all the
3930 generations older than the one being collected) as roots. We also
3931 remove non-mutable objects from the mutable list at this point.
3932 -------------------------------------------------------------------------- */
3935 scavenge_mutable_list(generation *gen)
3940 bd = gen->saved_mut_list;
3943 for (; bd != NULL; bd = bd->link) {
3944 for (q = bd->start; q < bd->free; q++) {
3946 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3949 switch (get_itbl((StgClosure *)p)->type) {
3951 barf("MUT_VAR_CLEAN on mutable list");
3953 mutlist_MUTVARS++; break;
3954 case MUT_ARR_PTRS_CLEAN:
3955 case MUT_ARR_PTRS_DIRTY:
3956 case MUT_ARR_PTRS_FROZEN:
3957 case MUT_ARR_PTRS_FROZEN0:
3958 mutlist_MUTARRS++; break;
3960 mutlist_OTHERS++; break;
3964 // Check whether this object is "clean", that is it
3965 // definitely doesn't point into a young generation.
3966 // Clean objects don't need to be scavenged. Some clean
3967 // objects (MUT_VAR_CLEAN) are not kept on the mutable
3968 // list at all; others, such as MUT_ARR_PTRS_CLEAN and
3969 // TSO, are always on the mutable list.
3971 switch (get_itbl((StgClosure *)p)->type) {
3972 case MUT_ARR_PTRS_CLEAN:
3973 recordMutableGen((StgClosure *)p,gen);
3976 StgTSO *tso = (StgTSO *)p;
3977 if ((tso->flags & TSO_DIRTY) == 0) {
3978 // A clean TSO: we don't have to traverse its
3979 // stack. However, we *do* follow the link field:
3980 // we don't want to have to mark a TSO dirty just
3981 // because we put it on a different queue.
3982 if (tso->why_blocked != BlockedOnBlackHole) {
3983 tso->link = (StgTSO *)evacuate((StgClosure *)tso->link);
3985 recordMutableGen((StgClosure *)p,gen);
3993 if (scavenge_one(p)) {
3994 // didn't manage to promote everything, so put the
3995 // object back on the list.
3996 recordMutableGen((StgClosure *)p,gen);
4001 // free the old mut_list
4002 freeChain(gen->saved_mut_list);
4003 gen->saved_mut_list = NULL;
4008 scavenge_static(void)
4010 StgClosure* p = static_objects;
4011 const StgInfoTable *info;
4013 /* Always evacuate straight to the oldest generation for static
4015 evac_gen = oldest_gen->no;
4017 /* keep going until we've scavenged all the objects on the linked
4019 while (p != END_OF_STATIC_LIST) {
4021 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
4024 if (info->type==RBH)
4025 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
4027 // make sure the info pointer is into text space
4029 /* Take this object *off* the static_objects list,
4030 * and put it on the scavenged_static_objects list.
4032 static_objects = *STATIC_LINK(info,p);
4033 *STATIC_LINK(info,p) = scavenged_static_objects;
4034 scavenged_static_objects = p;
4036 switch (info -> type) {
4040 StgInd *ind = (StgInd *)p;
4041 ind->indirectee = evacuate(ind->indirectee);
4043 /* might fail to evacuate it, in which case we have to pop it
4044 * back on the mutable list of the oldest generation. We
4045 * leave it *on* the scavenged_static_objects list, though,
4046 * in case we visit this object again.
4048 if (failed_to_evac) {
4049 failed_to_evac = rtsFalse;
4050 recordMutableGen((StgClosure *)p,oldest_gen);
4056 scavenge_thunk_srt(info);
4060 scavenge_fun_srt(info);
4067 next = (P_)p->payload + info->layout.payload.ptrs;
4068 // evacuate the pointers
4069 for (q = (P_)p->payload; q < next; q++) {
4070 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
4076 barf("scavenge_static: strange closure %d", (int)(info->type));
4079 ASSERT(failed_to_evac == rtsFalse);
4081 /* get the next static object from the list. Remember, there might
4082 * be more stuff on this list now that we've done some evacuating!
4083 * (static_objects is a global)
4089 /* -----------------------------------------------------------------------------
4090 scavenge a chunk of memory described by a bitmap
4091 -------------------------------------------------------------------------- */
4094 scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
4100 bitmap = large_bitmap->bitmap[b];
4101 for (i = 0; i < size; ) {
4102 if ((bitmap & 1) == 0) {
4103 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
4107 if (i % BITS_IN(W_) == 0) {
4109 bitmap = large_bitmap->bitmap[b];
4111 bitmap = bitmap >> 1;
4116 STATIC_INLINE StgPtr
4117 scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap)
4120 if ((bitmap & 1) == 0) {
4121 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
4124 bitmap = bitmap >> 1;
4130 /* -----------------------------------------------------------------------------
4131 scavenge_stack walks over a section of stack and evacuates all the
4132 objects pointed to by it. We can use the same code for walking
4133 AP_STACK_UPDs, since these are just sections of copied stack.
4134 -------------------------------------------------------------------------- */
4138 scavenge_stack(StgPtr p, StgPtr stack_end)
4140 const StgRetInfoTable* info;
4144 //IF_DEBUG(sanity, debugBelch(" scavenging stack between %p and %p", p, stack_end));
4147 * Each time around this loop, we are looking at a chunk of stack
4148 * that starts with an activation record.
4151 while (p < stack_end) {
4152 info = get_ret_itbl((StgClosure *)p);
4154 switch (info->i.type) {
4157 // In SMP, we can get update frames that point to indirections
4158 // when two threads evaluate the same thunk. We do attempt to
4159 // discover this situation in threadPaused(), but it's
4160 // possible that the following sequence occurs:
4169 // Now T is an indirection, and the update frame is already
4170 // marked on A's stack, so we won't traverse it again in
4171 // threadPaused(). We could traverse the whole stack again
4172 // before GC, but that seems like overkill.
4174 // Scavenging this update frame as normal would be disastrous;
4175 // the updatee would end up pointing to the value. So we turn
4176 // the indirection into an IND_PERM, so that evacuate will
4177 // copy the indirection into the old generation instead of
4179 if (get_itbl(((StgUpdateFrame *)p)->updatee)->type == IND) {
4180 ((StgUpdateFrame *)p)->updatee->header.info =
4181 (StgInfoTable *)&stg_IND_PERM_info;
4183 ((StgUpdateFrame *)p)->updatee
4184 = evacuate(((StgUpdateFrame *)p)->updatee);
4185 p += sizeofW(StgUpdateFrame);
4188 // small bitmap (< 32 entries, or 64 on a 64-bit machine)
4189 case CATCH_STM_FRAME:
4190 case CATCH_RETRY_FRAME:
4191 case ATOMICALLY_FRAME:
4196 bitmap = BITMAP_BITS(info->i.layout.bitmap);
4197 size = BITMAP_SIZE(info->i.layout.bitmap);
4198 // NOTE: the payload starts immediately after the info-ptr, we
4199 // don't have an StgHeader in the same sense as a heap closure.
4201 p = scavenge_small_bitmap(p, size, bitmap);
4205 scavenge_srt((StgClosure **)GET_SRT(info), info->i.srt_bitmap);
4213 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
4216 size = BCO_BITMAP_SIZE(bco);
4217 scavenge_large_bitmap(p, BCO_BITMAP(bco), size);
4222 // large bitmap (> 32 entries, or > 64 on a 64-bit machine)
4228 size = GET_LARGE_BITMAP(&info->i)->size;
4230 scavenge_large_bitmap(p, GET_LARGE_BITMAP(&info->i), size);
4232 // and don't forget to follow the SRT
4236 // Dynamic bitmap: the mask is stored on the stack, and
4237 // there are a number of non-pointers followed by a number
4238 // of pointers above the bitmapped area. (see StgMacros.h,
4243 dyn = ((StgRetDyn *)p)->liveness;
4245 // traverse the bitmap first
4246 bitmap = RET_DYN_LIVENESS(dyn);
4247 p = (P_)&((StgRetDyn *)p)->payload[0];
4248 size = RET_DYN_BITMAP_SIZE;
4249 p = scavenge_small_bitmap(p, size, bitmap);
4251 // skip over the non-ptr words
4252 p += RET_DYN_NONPTRS(dyn) + RET_DYN_NONPTR_REGS_SIZE;
4254 // follow the ptr words
4255 for (size = RET_DYN_PTRS(dyn); size > 0; size--) {
4256 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
4264 StgRetFun *ret_fun = (StgRetFun *)p;
4265 StgFunInfoTable *fun_info;
4267 ret_fun->fun = evacuate(ret_fun->fun);
4268 fun_info = get_fun_itbl(ret_fun->fun);
4269 p = scavenge_arg_block(fun_info, ret_fun->payload);
4274 barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->i.type));
4279 /*-----------------------------------------------------------------------------
4280 scavenge the large object list.
4282 evac_gen set by caller; similar games played with evac_gen as with
4283 scavenge() - see comment at the top of scavenge(). Most large
4284 objects are (repeatedly) mutable, so most of the time evac_gen will
4286 --------------------------------------------------------------------------- */
4289 scavenge_large(step *stp)
4294 bd = stp->new_large_objects;
4296 for (; bd != NULL; bd = stp->new_large_objects) {
4298 /* take this object *off* the large objects list and put it on
4299 * the scavenged large objects list. This is so that we can
4300 * treat new_large_objects as a stack and push new objects on
4301 * the front when evacuating.
4303 stp->new_large_objects = bd->link;
4304 dbl_link_onto(bd, &stp->scavenged_large_objects);
4306 // update the block count in this step.
4307 stp->n_scavenged_large_blocks += bd->blocks;
4310 if (scavenge_one(p)) {
4311 if (stp->gen_no > 0) {
4312 recordMutableGen((StgClosure *)p, stp->gen);
4318 /* -----------------------------------------------------------------------------
4319 Initialising the static object & mutable lists
4320 -------------------------------------------------------------------------- */
4323 zero_static_object_list(StgClosure* first_static)
4327 const StgInfoTable *info;
4329 for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
4331 link = *STATIC_LINK(info, p);
4332 *STATIC_LINK(info,p) = NULL;
4336 /* -----------------------------------------------------------------------------
4338 -------------------------------------------------------------------------- */
4345 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
4346 c = (StgIndStatic *)c->static_link)
4348 SET_INFO(c, c->saved_info);
4349 c->saved_info = NULL;
4350 // could, but not necessary: c->static_link = NULL;
4352 revertible_caf_list = NULL;
4356 markCAFs( evac_fn evac )
4360 for (c = (StgIndStatic *)caf_list; c != NULL;
4361 c = (StgIndStatic *)c->static_link)
4363 evac(&c->indirectee);
4365 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
4366 c = (StgIndStatic *)c->static_link)
4368 evac(&c->indirectee);
4372 /* -----------------------------------------------------------------------------
4373 Sanity code for CAF garbage collection.
4375 With DEBUG turned on, we manage a CAF list in addition to the SRT
4376 mechanism. After GC, we run down the CAF list and blackhole any
4377 CAFs which have been garbage collected. This means we get an error
4378 whenever the program tries to enter a garbage collected CAF.
4380 Any garbage collected CAFs are taken off the CAF list at the same
4382 -------------------------------------------------------------------------- */
4384 #if 0 && defined(DEBUG)
4391 const StgInfoTable *info;
4402 ASSERT(info->type == IND_STATIC);
4404 if (STATIC_LINK(info,p) == NULL) {
4405 IF_DEBUG(gccafs, debugBelch("CAF gc'd at 0x%04lx", (long)p));
4407 SET_INFO(p,&stg_BLACKHOLE_info);
4408 p = STATIC_LINK2(info,p);
4412 pp = &STATIC_LINK2(info,p);
4419 // debugBelch("%d CAFs live", i);
4424 /* -----------------------------------------------------------------------------
4427 * Code largely pinched from old RTS, then hacked to bits. We also do
4428 * lazy black holing here.
4430 * -------------------------------------------------------------------------- */
4432 struct stack_gap { StgWord gap_size; struct stack_gap *next_gap; };
4435 stackSqueeze(StgTSO *tso, StgPtr bottom)
4438 rtsBool prev_was_update_frame;
4439 StgClosure *updatee = NULL;
4440 StgRetInfoTable *info;
4441 StgWord current_gap_size;
4442 struct stack_gap *gap;
4445 // Traverse the stack upwards, replacing adjacent update frames
4446 // with a single update frame and a "stack gap". A stack gap
4447 // contains two values: the size of the gap, and the distance
4448 // to the next gap (or the stack top).
4452 ASSERT(frame < bottom);
4454 prev_was_update_frame = rtsFalse;
4455 current_gap_size = 0;
4456 gap = (struct stack_gap *) (tso->sp - sizeofW(StgUpdateFrame));
4458 while (frame < bottom) {
4460 info = get_ret_itbl((StgClosure *)frame);
4461 switch (info->i.type) {
4465 StgUpdateFrame *upd = (StgUpdateFrame *)frame;
4467 if (prev_was_update_frame) {
4469 TICK_UPD_SQUEEZED();
4470 /* wasn't there something about update squeezing and ticky to be
4471 * sorted out? oh yes: we aren't counting each enter properly
4472 * in this case. See the log somewhere. KSW 1999-04-21
4474 * Check two things: that the two update frames don't point to
4475 * the same object, and that the updatee_bypass isn't already an
4476 * indirection. Both of these cases only happen when we're in a
4477 * block hole-style loop (and there are multiple update frames
4478 * on the stack pointing to the same closure), but they can both
4479 * screw us up if we don't check.
4481 if (upd->updatee != updatee && !closure_IND(upd->updatee)) {
4482 UPD_IND_NOLOCK(upd->updatee, updatee);
4485 // now mark this update frame as a stack gap. The gap
4486 // marker resides in the bottom-most update frame of
4487 // the series of adjacent frames, and covers all the
4488 // frames in this series.
4489 current_gap_size += sizeofW(StgUpdateFrame);
4490 ((struct stack_gap *)frame)->gap_size = current_gap_size;
4491 ((struct stack_gap *)frame)->next_gap = gap;
4493 frame += sizeofW(StgUpdateFrame);
4497 // single update frame, or the topmost update frame in a series
4499 prev_was_update_frame = rtsTrue;
4500 updatee = upd->updatee;
4501 frame += sizeofW(StgUpdateFrame);
4507 prev_was_update_frame = rtsFalse;
4509 // we're not in a gap... check whether this is the end of a gap
4510 // (an update frame can't be the end of a gap).
4511 if (current_gap_size != 0) {
4512 gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
4514 current_gap_size = 0;
4516 frame += stack_frame_sizeW((StgClosure *)frame);
4521 if (current_gap_size != 0) {
4522 gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
4525 // Now we have a stack with gaps in it, and we have to walk down
4526 // shoving the stack up to fill in the gaps. A diagram might
4530 // | ********* | <- sp
4534 // | stack_gap | <- gap | chunk_size
4536 // | ......... | <- gap_end v
4542 // 'sp' points the the current top-of-stack
4543 // 'gap' points to the stack_gap structure inside the gap
4544 // ***** indicates real stack data
4545 // ..... indicates gap
4546 // <empty> indicates unused
4550 void *gap_start, *next_gap_start, *gap_end;
4553 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4554 sp = next_gap_start;
4556 while ((StgPtr)gap > tso->sp) {
4558 // we're working in *bytes* now...
4559 gap_start = next_gap_start;
4560 gap_end = (void*) ((unsigned char*)gap_start - gap->gap_size * sizeof(W_));
4562 gap = gap->next_gap;
4563 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4565 chunk_size = (unsigned char*)gap_end - (unsigned char*)next_gap_start;
4567 memmove(sp, next_gap_start, chunk_size);
4570 tso->sp = (StgPtr)sp;
4574 /* -----------------------------------------------------------------------------
4577 * We have to prepare for GC - this means doing lazy black holing
4578 * here. We also take the opportunity to do stack squeezing if it's
4580 * -------------------------------------------------------------------------- */
4582 threadPaused(Capability *cap, StgTSO *tso)
4585 StgRetInfoTable *info;
4588 nat words_to_squeeze = 0;
4590 nat weight_pending = 0;
4591 rtsBool prev_was_update_frame;
4593 stack_end = &tso->stack[tso->stack_size];
4595 frame = (StgClosure *)tso->sp;
4598 // If we've already marked this frame, then stop here.
4599 if (frame->header.info == (StgInfoTable *)&stg_marked_upd_frame_info) {
4603 info = get_ret_itbl(frame);
4605 switch (info->i.type) {
4609 SET_INFO(frame, (StgInfoTable *)&stg_marked_upd_frame_info);
4611 bh = ((StgUpdateFrame *)frame)->updatee;
4613 if (closure_IND(bh) || bh->header.info == &stg_BLACKHOLE_info) {
4614 IF_DEBUG(squeeze, debugBelch("suspending duplicate work: %ld words of stack\n", (StgPtr)frame - tso->sp));
4616 // If this closure is already an indirection, then
4617 // suspend the computation up to this point:
4618 suspendComputation(cap,tso,(StgPtr)frame);
4620 // Now drop the update frame, and arrange to return
4621 // the value to the frame underneath:
4622 tso->sp = (StgPtr)frame + sizeofW(StgUpdateFrame) - 2;
4623 tso->sp[1] = (StgWord)bh;
4624 tso->sp[0] = (W_)&stg_enter_info;
4626 // And continue with threadPaused; there might be
4627 // yet more computation to suspend.
4628 threadPaused(cap,tso);
4632 if (bh->header.info != &stg_CAF_BLACKHOLE_info) {
4633 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4634 debugBelch("Unexpected lazy BHing required at 0x%04lx\n",(long)bh);
4636 // zero out the slop so that the sanity checker can tell
4637 // where the next closure is.
4638 DEBUG_FILL_SLOP(bh);
4641 // We pretend that bh is now dead.
4642 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4644 SET_INFO(bh,&stg_BLACKHOLE_info);
4646 // We pretend that bh has just been created.
4647 LDV_RECORD_CREATE(bh);
4650 frame = (StgClosure *) ((StgUpdateFrame *)frame + 1);
4651 if (prev_was_update_frame) {
4652 words_to_squeeze += sizeofW(StgUpdateFrame);
4653 weight += weight_pending;
4656 prev_was_update_frame = rtsTrue;
4662 // normal stack frames; do nothing except advance the pointer
4665 nat frame_size = stack_frame_sizeW(frame);
4666 weight_pending += frame_size;
4667 frame = (StgClosure *)((StgPtr)frame + frame_size);
4668 prev_was_update_frame = rtsFalse;
4675 debugBelch("words_to_squeeze: %d, weight: %d, squeeze: %s\n",
4676 words_to_squeeze, weight,
4677 weight < words_to_squeeze ? "YES" : "NO"));
4679 // Should we squeeze or not? Arbitrary heuristic: we squeeze if
4680 // the number of words we have to shift down is less than the
4681 // number of stack words we squeeze away by doing so.
4682 if (1 /*RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue &&
4683 weight < words_to_squeeze*/) {
4684 stackSqueeze(tso, (StgPtr)frame);
4688 /* -----------------------------------------------------------------------------
4690 * -------------------------------------------------------------------------- */
4694 printMutableList(generation *gen)
4699 debugBelch("@@ Mutable list %p: ", gen->mut_list);
4701 for (bd = gen->mut_list; bd != NULL; bd = bd->link) {
4702 for (p = bd->start; p < bd->free; p++) {
4703 debugBelch("%p (%s), ", (void *)*p, info_type((StgClosure *)*p));