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).
109 StgWeak *old_weak_ptr_list; // also pending finaliser list
111 /* Which stage of processing various kinds of weak pointer are we at?
112 * (see traverse_weak_ptr_list() below for discussion).
114 typedef enum { WeakPtrs, WeakThreads, WeakDone } WeakStage;
115 static WeakStage weak_stage;
117 /* List of all threads during GC
119 static StgTSO *old_all_threads;
120 StgTSO *resurrected_threads;
122 /* Flag indicating failure to evacuate an object to the desired
125 static rtsBool failed_to_evac;
127 /* Saved nursery (used for 2-space collector only)
129 static bdescr *saved_nursery;
130 static nat saved_n_blocks;
132 /* Data used for allocation area sizing.
134 static lnat new_blocks; // blocks allocated during this GC
135 static lnat new_scavd_blocks; // ditto, but depth-first blocks
136 static lnat g0s0_pcnt_kept = 30; // percentage of g0s0 live at last minor GC
138 /* Used to avoid long recursion due to selector thunks
140 static lnat thunk_selector_depth = 0;
141 #define MAX_THUNK_SELECTOR_DEPTH 8
143 /* -----------------------------------------------------------------------------
144 Static function declarations
145 -------------------------------------------------------------------------- */
147 static bdescr * gc_alloc_block ( step *stp );
148 static void mark_root ( StgClosure **root );
150 // Use a register argument for evacuate, if available.
152 #define REGPARM1 __attribute__((regparm(1)))
157 REGPARM1 static StgClosure * evacuate (StgClosure *q);
159 static void zero_static_object_list ( StgClosure* first_static );
161 static rtsBool traverse_weak_ptr_list ( void );
162 static void mark_weak_ptr_list ( StgWeak **list );
164 static StgClosure * eval_thunk_selector ( nat field, StgSelector * p );
167 static void scavenge ( step * );
168 static void scavenge_mark_stack ( void );
169 static void scavenge_stack ( StgPtr p, StgPtr stack_end );
170 static rtsBool scavenge_one ( StgPtr p );
171 static void scavenge_large ( step * );
172 static void scavenge_static ( void );
173 static void scavenge_mutable_list ( generation *g );
175 static void scavenge_large_bitmap ( StgPtr p,
176 StgLargeBitmap *large_bitmap,
179 #if 0 && defined(DEBUG)
180 static void gcCAFs ( void );
183 /* -----------------------------------------------------------------------------
184 inline functions etc. for dealing with the mark bitmap & stack.
185 -------------------------------------------------------------------------- */
187 #define MARK_STACK_BLOCKS 4
189 static bdescr *mark_stack_bdescr;
190 static StgPtr *mark_stack;
191 static StgPtr *mark_sp;
192 static StgPtr *mark_splim;
194 // Flag and pointers used for falling back to a linear scan when the
195 // mark stack overflows.
196 static rtsBool mark_stack_overflowed;
197 static bdescr *oldgen_scan_bd;
198 static StgPtr oldgen_scan;
200 STATIC_INLINE rtsBool
201 mark_stack_empty(void)
203 return mark_sp == mark_stack;
206 STATIC_INLINE rtsBool
207 mark_stack_full(void)
209 return mark_sp >= mark_splim;
213 reset_mark_stack(void)
215 mark_sp = mark_stack;
219 push_mark_stack(StgPtr p)
230 /* -----------------------------------------------------------------------------
231 Allocate a new to-space block in the given step.
232 -------------------------------------------------------------------------- */
235 gc_alloc_block(step *stp)
237 bdescr *bd = allocBlock();
238 bd->gen_no = stp->gen_no;
242 // blocks in to-space in generations up to and including N
243 // get the BF_EVACUATED flag.
244 if (stp->gen_no <= N) {
245 bd->flags = BF_EVACUATED;
250 // Start a new to-space block, chain it on after the previous one.
251 if (stp->hp_bd != NULL) {
252 stp->hp_bd->free = stp->hp;
253 stp->hp_bd->link = bd;
258 stp->hpLim = stp->hp + BLOCK_SIZE_W;
267 gc_alloc_scavd_block(step *stp)
269 bdescr *bd = allocBlock();
270 bd->gen_no = stp->gen_no;
273 // blocks in to-space in generations up to and including N
274 // get the BF_EVACUATED flag.
275 if (stp->gen_no <= N) {
276 bd->flags = BF_EVACUATED;
281 bd->link = stp->blocks;
284 if (stp->scavd_hp != NULL) {
285 Bdescr(stp->scavd_hp)->free = stp->scavd_hp;
287 stp->scavd_hp = bd->start;
288 stp->scavd_hpLim = stp->scavd_hp + BLOCK_SIZE_W;
296 /* -----------------------------------------------------------------------------
299 Rough outline of the algorithm: for garbage collecting generation N
300 (and all younger generations):
302 - follow all pointers in the root set. the root set includes all
303 mutable objects in all generations (mutable_list).
305 - for each pointer, evacuate the object it points to into either
307 + to-space of the step given by step->to, which is the next
308 highest step in this generation or the first step in the next
309 generation if this is the last step.
311 + to-space of generations[evac_gen]->steps[0], if evac_gen != 0.
312 When we evacuate an object we attempt to evacuate
313 everything it points to into the same generation - this is
314 achieved by setting evac_gen to the desired generation. If
315 we can't do this, then an entry in the mut list has to
316 be made for the cross-generation pointer.
318 + if the object is already in a generation > N, then leave
321 - repeatedly scavenge to-space from each step in each generation
322 being collected until no more objects can be evacuated.
324 - free from-space in each step, and set from-space = to-space.
326 Locks held: all capabilities are held throughout GarbageCollect().
328 -------------------------------------------------------------------------- */
331 GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc )
335 lnat live, allocated, collected = 0, copied = 0, scavd_copied = 0;
336 lnat oldgen_saved_blocks = 0;
342 CostCentreStack *prev_CCS;
345 #if defined(DEBUG) && defined(GRAN)
346 IF_DEBUG(gc, debugBelch("@@ Starting garbage collection at %ld (%lx)\n",
350 #if defined(RTS_USER_SIGNALS)
355 // tell the STM to discard any cached closures its hoping to re-use
358 // tell the stats department that we've started a GC
362 // check for memory leaks if DEBUG is on
366 // Init stats and print par specific (timing) info
367 PAR_TICKY_PAR_START();
369 // attribute any costs to CCS_GC
375 /* Approximate how much we allocated.
376 * Todo: only when generating stats?
378 allocated = calcAllocated();
380 /* Figure out which generation to collect
382 if (force_major_gc) {
383 N = RtsFlags.GcFlags.generations - 1;
387 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
388 if (generations[g].steps[0].n_blocks +
389 generations[g].steps[0].n_large_blocks
390 >= generations[g].max_blocks) {
394 major_gc = (N == RtsFlags.GcFlags.generations-1);
397 #ifdef RTS_GTK_FRONTPANEL
398 if (RtsFlags.GcFlags.frontpanel) {
399 updateFrontPanelBeforeGC(N);
403 // check stack sanity *before* GC (ToDo: check all threads)
405 // ToDo!: check sanity IF_DEBUG(sanity, checkTSOsSanity());
407 IF_DEBUG(sanity, checkFreeListSanity());
409 /* Initialise the static object lists
411 static_objects = END_OF_STATIC_LIST;
412 scavenged_static_objects = END_OF_STATIC_LIST;
414 /* Save the nursery if we're doing a two-space collection.
415 * g0s0->blocks will be used for to-space, so we need to get the
416 * nursery out of the way.
418 if (RtsFlags.GcFlags.generations == 1) {
419 saved_nursery = g0s0->blocks;
420 saved_n_blocks = g0s0->n_blocks;
425 /* Keep a count of how many new blocks we allocated during this GC
426 * (used for resizing the allocation area, later).
429 new_scavd_blocks = 0;
431 // Initialise to-space in all the generations/steps that we're
434 for (g = 0; g <= N; g++) {
436 // throw away the mutable list. Invariant: the mutable list
437 // always has at least one block; this means we can avoid a check for
438 // NULL in recordMutable().
440 freeChain(generations[g].mut_list);
441 generations[g].mut_list = allocBlock();
442 for (i = 0; i < n_capabilities; i++) {
443 freeChain(capabilities[i].mut_lists[g]);
444 capabilities[i].mut_lists[g] = allocBlock();
448 for (s = 0; s < generations[g].n_steps; s++) {
450 // generation 0, step 0 doesn't need to-space
451 if (g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1) {
455 stp = &generations[g].steps[s];
456 ASSERT(stp->gen_no == g);
458 // start a new to-space for this step.
459 stp->old_blocks = stp->blocks;
460 stp->n_old_blocks = stp->n_blocks;
462 // allocate the first to-space block; extra blocks will be
463 // chained on as necessary.
465 bd = gc_alloc_block(stp);
468 stp->scan = bd->start;
471 // allocate a block for "already scavenged" objects. This goes
472 // on the front of the stp->blocks list, so it won't be
473 // traversed by the scavenging sweep.
474 gc_alloc_scavd_block(stp);
476 // initialise the large object queues.
477 stp->new_large_objects = NULL;
478 stp->scavenged_large_objects = NULL;
479 stp->n_scavenged_large_blocks = 0;
481 // mark the large objects as not evacuated yet
482 for (bd = stp->large_objects; bd; bd = bd->link) {
483 bd->flags &= ~BF_EVACUATED;
486 // for a compacted step, we need to allocate the bitmap
487 if (stp->is_compacted) {
488 nat bitmap_size; // in bytes
489 bdescr *bitmap_bdescr;
492 bitmap_size = stp->n_old_blocks * BLOCK_SIZE / (sizeof(W_)*BITS_PER_BYTE);
494 if (bitmap_size > 0) {
495 bitmap_bdescr = allocGroup((lnat)BLOCK_ROUND_UP(bitmap_size)
497 stp->bitmap = bitmap_bdescr;
498 bitmap = bitmap_bdescr->start;
500 IF_DEBUG(gc, debugBelch("bitmap_size: %d, bitmap: %p",
501 bitmap_size, bitmap););
503 // don't forget to fill it with zeros!
504 memset(bitmap, 0, bitmap_size);
506 // For each block in this step, point to its bitmap from the
508 for (bd=stp->old_blocks; bd != NULL; bd = bd->link) {
509 bd->u.bitmap = bitmap;
510 bitmap += BLOCK_SIZE_W / (sizeof(W_)*BITS_PER_BYTE);
512 // Also at this point we set the BF_COMPACTED flag
513 // for this block. The invariant is that
514 // BF_COMPACTED is always unset, except during GC
515 // when it is set on those blocks which will be
517 bd->flags |= BF_COMPACTED;
524 /* make sure the older generations have at least one block to
525 * allocate into (this makes things easier for copy(), see below).
527 for (g = N+1; g < RtsFlags.GcFlags.generations; g++) {
528 for (s = 0; s < generations[g].n_steps; s++) {
529 stp = &generations[g].steps[s];
530 if (stp->hp_bd == NULL) {
531 ASSERT(stp->blocks == NULL);
532 bd = gc_alloc_block(stp);
536 if (stp->scavd_hp == NULL) {
537 gc_alloc_scavd_block(stp);
540 /* Set the scan pointer for older generations: remember we
541 * still have to scavenge objects that have been promoted. */
543 stp->scan_bd = stp->hp_bd;
544 stp->new_large_objects = NULL;
545 stp->scavenged_large_objects = NULL;
546 stp->n_scavenged_large_blocks = 0;
549 /* Move the private mutable lists from each capability onto the
550 * main mutable list for the generation.
552 for (i = 0; i < n_capabilities; i++) {
553 for (bd = capabilities[i].mut_lists[g];
554 bd->link != NULL; bd = bd->link) {
557 bd->link = generations[g].mut_list;
558 generations[g].mut_list = capabilities[i].mut_lists[g];
559 capabilities[i].mut_lists[g] = allocBlock();
563 /* Allocate a mark stack if we're doing a major collection.
566 mark_stack_bdescr = allocGroup(MARK_STACK_BLOCKS);
567 mark_stack = (StgPtr *)mark_stack_bdescr->start;
568 mark_sp = mark_stack;
569 mark_splim = mark_stack + (MARK_STACK_BLOCKS * BLOCK_SIZE_W);
571 mark_stack_bdescr = NULL;
574 /* -----------------------------------------------------------------------
575 * follow all the roots that we know about:
576 * - mutable lists from each generation > N
577 * we want to *scavenge* these roots, not evacuate them: they're not
578 * going to move in this GC.
579 * Also: do them in reverse generation order. This is because we
580 * often want to promote objects that are pointed to by older
581 * generations early, so we don't have to repeatedly copy them.
582 * Doing the generations in reverse order ensures that we don't end
583 * up in the situation where we want to evac an object to gen 3 and
584 * it has already been evaced to gen 2.
588 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
589 generations[g].saved_mut_list = generations[g].mut_list;
590 generations[g].mut_list = allocBlock();
591 // mut_list always has at least one block.
594 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
595 IF_PAR_DEBUG(verbose, printMutableList(&generations[g]));
596 scavenge_mutable_list(&generations[g]);
598 for (st = generations[g].n_steps-1; st >= 0; st--) {
599 scavenge(&generations[g].steps[st]);
604 /* follow roots from the CAF list (used by GHCi)
609 /* follow all the roots that the application knows about.
612 get_roots(mark_root);
615 /* And don't forget to mark the TSO if we got here direct from
617 /* Not needed in a seq version?
619 CurrentTSO = (StgTSO *)MarkRoot((StgClosure *)CurrentTSO);
623 // Mark the entries in the GALA table of the parallel system
624 markLocalGAs(major_gc);
625 // Mark all entries on the list of pending fetches
626 markPendingFetches(major_gc);
629 /* Mark the weak pointer list, and prepare to detect dead weak
632 mark_weak_ptr_list(&weak_ptr_list);
633 old_weak_ptr_list = weak_ptr_list;
634 weak_ptr_list = NULL;
635 weak_stage = WeakPtrs;
637 /* The all_threads list is like the weak_ptr_list.
638 * See traverse_weak_ptr_list() for the details.
640 old_all_threads = all_threads;
641 all_threads = END_TSO_QUEUE;
642 resurrected_threads = END_TSO_QUEUE;
644 /* Mark the stable pointer table.
646 markStablePtrTable(mark_root);
648 /* -------------------------------------------------------------------------
649 * Repeatedly scavenge all the areas we know about until there's no
650 * more scavenging to be done.
657 // scavenge static objects
658 if (major_gc && static_objects != END_OF_STATIC_LIST) {
659 IF_DEBUG(sanity, checkStaticObjects(static_objects));
663 /* When scavenging the older generations: Objects may have been
664 * evacuated from generations <= N into older generations, and we
665 * need to scavenge these objects. We're going to try to ensure that
666 * any evacuations that occur move the objects into at least the
667 * same generation as the object being scavenged, otherwise we
668 * have to create new entries on the mutable list for the older
672 // scavenge each step in generations 0..maxgen
678 // scavenge objects in compacted generation
679 if (mark_stack_overflowed || oldgen_scan_bd != NULL ||
680 (mark_stack_bdescr != NULL && !mark_stack_empty())) {
681 scavenge_mark_stack();
685 for (gen = RtsFlags.GcFlags.generations; --gen >= 0; ) {
686 for (st = generations[gen].n_steps; --st >= 0; ) {
687 if (gen == 0 && st == 0 && RtsFlags.GcFlags.generations > 1) {
690 stp = &generations[gen].steps[st];
692 if (stp->hp_bd != stp->scan_bd || stp->scan < stp->hp) {
697 if (stp->new_large_objects != NULL) {
706 if (flag) { goto loop; }
708 // must be last... invariant is that everything is fully
709 // scavenged at this point.
710 if (traverse_weak_ptr_list()) { // returns rtsTrue if evaced something
715 /* Update the pointers from the task list - these are
716 * treated as weak pointers because we want to allow a main thread
717 * to get a BlockedOnDeadMVar exception in the same way as any other
718 * thread. Note that the threads should all have been retained by
719 * GC by virtue of being on the all_threads list, we're just
720 * updating pointers here.
725 for (task = all_tasks; task != NULL; task = task->all_link) {
726 if (!task->stopped && task->tso) {
727 tso = (StgTSO *) isAlive((StgClosure *)task->tso);
729 barf("task %p: main thread %d has been GC'd",
743 // Reconstruct the Global Address tables used in GUM
744 rebuildGAtables(major_gc);
745 IF_DEBUG(sanity, checkLAGAtable(rtsTrue/*check closures, too*/));
748 // Now see which stable names are still alive.
751 // Tidy the end of the to-space chains
752 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
753 for (s = 0; s < generations[g].n_steps; s++) {
754 stp = &generations[g].steps[s];
755 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
756 ASSERT(Bdescr(stp->hp) == stp->hp_bd);
757 stp->hp_bd->free = stp->hp;
758 Bdescr(stp->scavd_hp)->free = stp->scavd_hp;
764 // We call processHeapClosureForDead() on every closure destroyed during
765 // the current garbage collection, so we invoke LdvCensusForDead().
766 if (RtsFlags.ProfFlags.doHeapProfile == HEAP_BY_LDV
767 || RtsFlags.ProfFlags.bioSelector != NULL)
771 // NO MORE EVACUATION AFTER THIS POINT!
772 // Finally: compaction of the oldest generation.
773 if (major_gc && oldest_gen->steps[0].is_compacted) {
774 // save number of blocks for stats
775 oldgen_saved_blocks = oldest_gen->steps[0].n_old_blocks;
779 IF_DEBUG(sanity, checkGlobalTSOList(rtsFalse));
781 /* run through all the generations/steps and tidy up
783 copied = new_blocks * BLOCK_SIZE_W;
784 scavd_copied = new_scavd_blocks * BLOCK_SIZE_W;
785 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
788 generations[g].collections++; // for stats
791 // Count the mutable list as bytes "copied" for the purposes of
792 // stats. Every mutable list is copied during every GC.
794 for (bd = generations[g].mut_list; bd != NULL; bd = bd->link) {
795 copied += (bd->free - bd->start) * sizeof(StgWord);
799 for (s = 0; s < generations[g].n_steps; s++) {
801 stp = &generations[g].steps[s];
803 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
804 // stats information: how much we copied
806 copied -= stp->hp_bd->start + BLOCK_SIZE_W -
808 scavd_copied -= (P_)(BLOCK_ROUND_UP(stp->scavd_hp)) - stp->scavd_hp;
812 // for generations we collected...
815 // rough calculation of garbage collected, for stats output
816 if (stp->is_compacted) {
817 collected += (oldgen_saved_blocks - stp->n_old_blocks) * BLOCK_SIZE_W;
819 if (g == 0 && s == 0) {
820 collected += countNurseryBlocks() * BLOCK_SIZE_W;
821 collected += alloc_blocks;
823 collected += stp->n_old_blocks * BLOCK_SIZE_W;
827 /* free old memory and shift to-space into from-space for all
828 * the collected steps (except the allocation area). These
829 * freed blocks will probaby be quickly recycled.
831 if (!(g == 0 && s == 0)) {
832 if (stp->is_compacted) {
833 // for a compacted step, just shift the new to-space
834 // onto the front of the now-compacted existing blocks.
835 for (bd = stp->blocks; bd != NULL; bd = bd->link) {
836 bd->flags &= ~BF_EVACUATED; // now from-space
838 // tack the new blocks on the end of the existing blocks
839 if (stp->old_blocks != NULL) {
840 for (bd = stp->old_blocks; bd != NULL; bd = next) {
841 // NB. this step might not be compacted next
842 // time, so reset the BF_COMPACTED flags.
843 // They are set before GC if we're going to
844 // compact. (search for BF_COMPACTED above).
845 bd->flags &= ~BF_COMPACTED;
848 bd->link = stp->blocks;
851 stp->blocks = stp->old_blocks;
853 // add the new blocks to the block tally
854 stp->n_blocks += stp->n_old_blocks;
855 ASSERT(countBlocks(stp->blocks) == stp->n_blocks);
857 freeChain(stp->old_blocks);
858 for (bd = stp->blocks; bd != NULL; bd = bd->link) {
859 bd->flags &= ~BF_EVACUATED; // now from-space
862 stp->old_blocks = NULL;
863 stp->n_old_blocks = 0;
866 /* LARGE OBJECTS. The current live large objects are chained on
867 * scavenged_large, having been moved during garbage
868 * collection from large_objects. Any objects left on
869 * large_objects list are therefore dead, so we free them here.
871 for (bd = stp->large_objects; bd != NULL; bd = next) {
877 // update the count of blocks used by large objects
878 for (bd = stp->scavenged_large_objects; bd != NULL; bd = bd->link) {
879 bd->flags &= ~BF_EVACUATED;
881 stp->large_objects = stp->scavenged_large_objects;
882 stp->n_large_blocks = stp->n_scavenged_large_blocks;
885 // for older generations...
887 /* For older generations, we need to append the
888 * scavenged_large_object list (i.e. large objects that have been
889 * promoted during this GC) to the large_object list for that step.
891 for (bd = stp->scavenged_large_objects; bd; bd = next) {
893 bd->flags &= ~BF_EVACUATED;
894 dbl_link_onto(bd, &stp->large_objects);
897 // add the new blocks we promoted during this GC
898 stp->n_large_blocks += stp->n_scavenged_large_blocks;
903 /* Reset the sizes of the older generations when we do a major
906 * CURRENT STRATEGY: make all generations except zero the same size.
907 * We have to stay within the maximum heap size, and leave a certain
908 * percentage of the maximum heap size available to allocate into.
910 if (major_gc && RtsFlags.GcFlags.generations > 1) {
911 nat live, size, min_alloc;
912 nat max = RtsFlags.GcFlags.maxHeapSize;
913 nat gens = RtsFlags.GcFlags.generations;
915 // live in the oldest generations
916 live = oldest_gen->steps[0].n_blocks +
917 oldest_gen->steps[0].n_large_blocks;
919 // default max size for all generations except zero
920 size = stg_max(live * RtsFlags.GcFlags.oldGenFactor,
921 RtsFlags.GcFlags.minOldGenSize);
923 // minimum size for generation zero
924 min_alloc = stg_max((RtsFlags.GcFlags.pcFreeHeap * max) / 200,
925 RtsFlags.GcFlags.minAllocAreaSize);
927 // Auto-enable compaction when the residency reaches a
928 // certain percentage of the maximum heap size (default: 30%).
929 if (RtsFlags.GcFlags.generations > 1 &&
930 (RtsFlags.GcFlags.compact ||
932 oldest_gen->steps[0].n_blocks >
933 (RtsFlags.GcFlags.compactThreshold * max) / 100))) {
934 oldest_gen->steps[0].is_compacted = 1;
935 // debugBelch("compaction: on\n", live);
937 oldest_gen->steps[0].is_compacted = 0;
938 // debugBelch("compaction: off\n", live);
941 // if we're going to go over the maximum heap size, reduce the
942 // size of the generations accordingly. The calculation is
943 // different if compaction is turned on, because we don't need
944 // to double the space required to collect the old generation.
947 // this test is necessary to ensure that the calculations
948 // below don't have any negative results - we're working
949 // with unsigned values here.
950 if (max < min_alloc) {
954 if (oldest_gen->steps[0].is_compacted) {
955 if ( (size + (size - 1) * (gens - 2) * 2) + min_alloc > max ) {
956 size = (max - min_alloc) / ((gens - 1) * 2 - 1);
959 if ( (size * (gens - 1) * 2) + min_alloc > max ) {
960 size = (max - min_alloc) / ((gens - 1) * 2);
970 debugBelch("live: %d, min_alloc: %d, size : %d, max = %d\n", live,
971 min_alloc, size, max);
974 for (g = 0; g < gens; g++) {
975 generations[g].max_blocks = size;
979 // Guess the amount of live data for stats.
982 /* Free the small objects allocated via allocate(), since this will
983 * all have been copied into G0S1 now.
985 if (small_alloc_list != NULL) {
986 freeChain(small_alloc_list);
988 small_alloc_list = NULL;
992 alloc_blocks_lim = RtsFlags.GcFlags.minAllocAreaSize;
994 // Start a new pinned_object_block
995 pinned_object_block = NULL;
997 /* Free the mark stack.
999 if (mark_stack_bdescr != NULL) {
1000 freeGroup(mark_stack_bdescr);
1003 /* Free any bitmaps.
1005 for (g = 0; g <= N; g++) {
1006 for (s = 0; s < generations[g].n_steps; s++) {
1007 stp = &generations[g].steps[s];
1008 if (stp->bitmap != NULL) {
1009 freeGroup(stp->bitmap);
1015 /* Two-space collector:
1016 * Free the old to-space, and estimate the amount of live data.
1018 if (RtsFlags.GcFlags.generations == 1) {
1021 if (g0s0->old_blocks != NULL) {
1022 freeChain(g0s0->old_blocks);
1024 for (bd = g0s0->blocks; bd != NULL; bd = bd->link) {
1025 bd->flags = 0; // now from-space
1027 g0s0->old_blocks = g0s0->blocks;
1028 g0s0->n_old_blocks = g0s0->n_blocks;
1029 g0s0->blocks = saved_nursery;
1030 g0s0->n_blocks = saved_n_blocks;
1032 /* For a two-space collector, we need to resize the nursery. */
1034 /* set up a new nursery. Allocate a nursery size based on a
1035 * function of the amount of live data (by default a factor of 2)
1036 * Use the blocks from the old nursery if possible, freeing up any
1039 * If we get near the maximum heap size, then adjust our nursery
1040 * size accordingly. If the nursery is the same size as the live
1041 * data (L), then we need 3L bytes. We can reduce the size of the
1042 * nursery to bring the required memory down near 2L bytes.
1044 * A normal 2-space collector would need 4L bytes to give the same
1045 * performance we get from 3L bytes, reducing to the same
1046 * performance at 2L bytes.
1048 blocks = g0s0->n_old_blocks;
1050 if ( RtsFlags.GcFlags.maxHeapSize != 0 &&
1051 blocks * RtsFlags.GcFlags.oldGenFactor * 2 >
1052 RtsFlags.GcFlags.maxHeapSize ) {
1053 long adjusted_blocks; // signed on purpose
1056 adjusted_blocks = (RtsFlags.GcFlags.maxHeapSize - 2 * blocks);
1057 IF_DEBUG(gc, debugBelch("@@ Near maximum heap size of 0x%x blocks, blocks = %d, adjusted to %ld", RtsFlags.GcFlags.maxHeapSize, blocks, adjusted_blocks));
1058 pc_free = adjusted_blocks * 100 / RtsFlags.GcFlags.maxHeapSize;
1059 if (pc_free < RtsFlags.GcFlags.pcFreeHeap) /* might even be < 0 */ {
1062 blocks = adjusted_blocks;
1065 blocks *= RtsFlags.GcFlags.oldGenFactor;
1066 if (blocks < RtsFlags.GcFlags.minAllocAreaSize) {
1067 blocks = RtsFlags.GcFlags.minAllocAreaSize;
1070 resizeNurseries(blocks);
1073 /* Generational collector:
1074 * If the user has given us a suggested heap size, adjust our
1075 * allocation area to make best use of the memory available.
1078 if (RtsFlags.GcFlags.heapSizeSuggestion) {
1080 nat needed = calcNeeded(); // approx blocks needed at next GC
1082 /* Guess how much will be live in generation 0 step 0 next time.
1083 * A good approximation is obtained by finding the
1084 * percentage of g0s0 that was live at the last minor GC.
1087 g0s0_pcnt_kept = (new_blocks * 100) / countNurseryBlocks();
1090 /* Estimate a size for the allocation area based on the
1091 * information available. We might end up going slightly under
1092 * or over the suggested heap size, but we should be pretty
1095 * Formula: suggested - needed
1096 * ----------------------------
1097 * 1 + g0s0_pcnt_kept/100
1099 * where 'needed' is the amount of memory needed at the next
1100 * collection for collecting all steps except g0s0.
1103 (((long)RtsFlags.GcFlags.heapSizeSuggestion - (long)needed) * 100) /
1104 (100 + (long)g0s0_pcnt_kept);
1106 if (blocks < (long)RtsFlags.GcFlags.minAllocAreaSize) {
1107 blocks = RtsFlags.GcFlags.minAllocAreaSize;
1110 resizeNurseries((nat)blocks);
1113 // we might have added extra large blocks to the nursery, so
1114 // resize back to minAllocAreaSize again.
1115 resizeNurseriesFixed(RtsFlags.GcFlags.minAllocAreaSize);
1119 // mark the garbage collected CAFs as dead
1120 #if 0 && defined(DEBUG) // doesn't work at the moment
1121 if (major_gc) { gcCAFs(); }
1125 // resetStaticObjectForRetainerProfiling() must be called before
1127 resetStaticObjectForRetainerProfiling();
1130 // zero the scavenged static object list
1132 zero_static_object_list(scavenged_static_objects);
1135 // Reset the nursery
1138 // start any pending finalizers
1139 scheduleFinalizers(last_free_capability, old_weak_ptr_list);
1141 // send exceptions to any threads which were about to die
1142 resurrectThreads(resurrected_threads);
1144 // Update the stable pointer hash table.
1145 updateStablePtrTable(major_gc);
1147 // check sanity after GC
1148 IF_DEBUG(sanity, checkSanity());
1150 // extra GC trace info
1151 IF_DEBUG(gc, statDescribeGens());
1154 // symbol-table based profiling
1155 /* heapCensus(to_blocks); */ /* ToDo */
1158 // restore enclosing cost centre
1164 // check for memory leaks if DEBUG is on
1168 #ifdef RTS_GTK_FRONTPANEL
1169 if (RtsFlags.GcFlags.frontpanel) {
1170 updateFrontPanelAfterGC( N, live );
1174 // ok, GC over: tell the stats department what happened.
1175 stat_endGC(allocated, collected, live, copied, scavd_copied, N);
1177 #if defined(RTS_USER_SIGNALS)
1178 // unblock signals again
1179 unblockUserSignals();
1188 /* -----------------------------------------------------------------------------
1191 traverse_weak_ptr_list is called possibly many times during garbage
1192 collection. It returns a flag indicating whether it did any work
1193 (i.e. called evacuate on any live pointers).
1195 Invariant: traverse_weak_ptr_list is called when the heap is in an
1196 idempotent state. That means that there are no pending
1197 evacuate/scavenge operations. This invariant helps the weak
1198 pointer code decide which weak pointers are dead - if there are no
1199 new live weak pointers, then all the currently unreachable ones are
1202 For generational GC: we just don't try to finalize weak pointers in
1203 older generations than the one we're collecting. This could
1204 probably be optimised by keeping per-generation lists of weak
1205 pointers, but for a few weak pointers this scheme will work.
1207 There are three distinct stages to processing weak pointers:
1209 - weak_stage == WeakPtrs
1211 We process all the weak pointers whos keys are alive (evacuate
1212 their values and finalizers), and repeat until we can find no new
1213 live keys. If no live keys are found in this pass, then we
1214 evacuate the finalizers of all the dead weak pointers in order to
1217 - weak_stage == WeakThreads
1219 Now, we discover which *threads* are still alive. Pointers to
1220 threads from the all_threads and main thread lists are the
1221 weakest of all: a pointers from the finalizer of a dead weak
1222 pointer can keep a thread alive. Any threads found to be unreachable
1223 are evacuated and placed on the resurrected_threads list so we
1224 can send them a signal later.
1226 - weak_stage == WeakDone
1228 No more evacuation is done.
1230 -------------------------------------------------------------------------- */
1233 traverse_weak_ptr_list(void)
1235 StgWeak *w, **last_w, *next_w;
1237 rtsBool flag = rtsFalse;
1239 switch (weak_stage) {
1245 /* doesn't matter where we evacuate values/finalizers to, since
1246 * these pointers are treated as roots (iff the keys are alive).
1250 last_w = &old_weak_ptr_list;
1251 for (w = old_weak_ptr_list; w != NULL; w = next_w) {
1253 /* There might be a DEAD_WEAK on the list if finalizeWeak# was
1254 * called on a live weak pointer object. Just remove it.
1256 if (w->header.info == &stg_DEAD_WEAK_info) {
1257 next_w = ((StgDeadWeak *)w)->link;
1262 switch (get_itbl(w)->type) {
1265 next_w = (StgWeak *)((StgEvacuated *)w)->evacuee;
1270 /* Now, check whether the key is reachable.
1272 new = isAlive(w->key);
1275 // evacuate the value and finalizer
1276 w->value = evacuate(w->value);
1277 w->finalizer = evacuate(w->finalizer);
1278 // remove this weak ptr from the old_weak_ptr list
1280 // and put it on the new weak ptr list
1282 w->link = weak_ptr_list;
1285 IF_DEBUG(weak, debugBelch("Weak pointer still alive at %p -> %p",
1290 last_w = &(w->link);
1296 barf("traverse_weak_ptr_list: not WEAK");
1300 /* If we didn't make any changes, then we can go round and kill all
1301 * the dead weak pointers. The old_weak_ptr list is used as a list
1302 * of pending finalizers later on.
1304 if (flag == rtsFalse) {
1305 for (w = old_weak_ptr_list; w; w = w->link) {
1306 w->finalizer = evacuate(w->finalizer);
1309 // Next, move to the WeakThreads stage after fully
1310 // scavenging the finalizers we've just evacuated.
1311 weak_stage = WeakThreads;
1317 /* Now deal with the all_threads list, which behaves somewhat like
1318 * the weak ptr list. If we discover any threads that are about to
1319 * become garbage, we wake them up and administer an exception.
1322 StgTSO *t, *tmp, *next, **prev;
1324 prev = &old_all_threads;
1325 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1327 tmp = (StgTSO *)isAlive((StgClosure *)t);
1333 ASSERT(get_itbl(t)->type == TSO);
1334 switch (t->what_next) {
1335 case ThreadRelocated:
1340 case ThreadComplete:
1341 // finshed or died. The thread might still be alive, but we
1342 // don't keep it on the all_threads list. Don't forget to
1343 // stub out its global_link field.
1344 next = t->global_link;
1345 t->global_link = END_TSO_QUEUE;
1352 // Threads blocked on black holes: if the black hole
1353 // is alive, then the thread is alive too.
1354 if (tmp == NULL && t->why_blocked == BlockedOnBlackHole) {
1355 if (isAlive(t->block_info.closure)) {
1356 t = (StgTSO *)evacuate((StgClosure *)t);
1363 // not alive (yet): leave this thread on the
1364 // old_all_threads list.
1365 prev = &(t->global_link);
1366 next = t->global_link;
1369 // alive: move this thread onto the all_threads list.
1370 next = t->global_link;
1371 t->global_link = all_threads;
1378 /* If we evacuated any threads, we need to go back to the scavenger.
1380 if (flag) return rtsTrue;
1382 /* And resurrect any threads which were about to become garbage.
1385 StgTSO *t, *tmp, *next;
1386 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1387 next = t->global_link;
1388 tmp = (StgTSO *)evacuate((StgClosure *)t);
1389 tmp->global_link = resurrected_threads;
1390 resurrected_threads = tmp;
1394 /* Finally, we can update the blackhole_queue. This queue
1395 * simply strings together TSOs blocked on black holes, it is
1396 * not intended to keep anything alive. Hence, we do not follow
1397 * pointers on the blackhole_queue until now, when we have
1398 * determined which TSOs are otherwise reachable. We know at
1399 * this point that all TSOs have been evacuated, however.
1403 for (pt = &blackhole_queue; *pt != END_TSO_QUEUE; pt = &((*pt)->link)) {
1404 *pt = (StgTSO *)isAlive((StgClosure *)*pt);
1405 ASSERT(*pt != NULL);
1409 weak_stage = WeakDone; // *now* we're done,
1410 return rtsTrue; // but one more round of scavenging, please
1413 barf("traverse_weak_ptr_list");
1419 /* -----------------------------------------------------------------------------
1420 After GC, the live weak pointer list may have forwarding pointers
1421 on it, because a weak pointer object was evacuated after being
1422 moved to the live weak pointer list. We remove those forwarding
1425 Also, we don't consider weak pointer objects to be reachable, but
1426 we must nevertheless consider them to be "live" and retain them.
1427 Therefore any weak pointer objects which haven't as yet been
1428 evacuated need to be evacuated now.
1429 -------------------------------------------------------------------------- */
1433 mark_weak_ptr_list ( StgWeak **list )
1435 StgWeak *w, **last_w;
1438 for (w = *list; w; w = w->link) {
1439 // w might be WEAK, EVACUATED, or DEAD_WEAK (actually CON_STATIC) here
1440 ASSERT(w->header.info == &stg_DEAD_WEAK_info
1441 || get_itbl(w)->type == WEAK || get_itbl(w)->type == EVACUATED);
1442 w = (StgWeak *)evacuate((StgClosure *)w);
1444 last_w = &(w->link);
1448 /* -----------------------------------------------------------------------------
1449 isAlive determines whether the given closure is still alive (after
1450 a garbage collection) or not. It returns the new address of the
1451 closure if it is alive, or NULL otherwise.
1453 NOTE: Use it before compaction only!
1454 -------------------------------------------------------------------------- */
1458 isAlive(StgClosure *p)
1460 const StgInfoTable *info;
1465 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
1468 // ignore static closures
1470 // ToDo: for static closures, check the static link field.
1471 // Problem here is that we sometimes don't set the link field, eg.
1472 // for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
1474 if (!HEAP_ALLOCED(p)) {
1478 // ignore closures in generations that we're not collecting.
1480 if (bd->gen_no > N) {
1484 // if it's a pointer into to-space, then we're done
1485 if (bd->flags & BF_EVACUATED) {
1489 // large objects use the evacuated flag
1490 if (bd->flags & BF_LARGE) {
1494 // check the mark bit for compacted steps
1495 if ((bd->flags & BF_COMPACTED) && is_marked((P_)p,bd)) {
1499 switch (info->type) {
1504 case IND_OLDGEN: // rely on compatible layout with StgInd
1505 case IND_OLDGEN_PERM:
1506 // follow indirections
1507 p = ((StgInd *)p)->indirectee;
1512 return ((StgEvacuated *)p)->evacuee;
1515 if (((StgTSO *)p)->what_next == ThreadRelocated) {
1516 p = (StgClosure *)((StgTSO *)p)->link;
1529 mark_root(StgClosure **root)
1531 *root = evacuate(*root);
1535 upd_evacuee(StgClosure *p, StgClosure *dest)
1537 // not true: (ToDo: perhaps it should be)
1538 // ASSERT(Bdescr((P_)dest)->flags & BF_EVACUATED);
1539 SET_INFO(p, &stg_EVACUATED_info);
1540 ((StgEvacuated *)p)->evacuee = dest;
1544 STATIC_INLINE StgClosure *
1545 copy(StgClosure *src, nat size, step *stp)
1551 nat size_org = size;
1554 TICK_GC_WORDS_COPIED(size);
1555 /* Find out where we're going, using the handy "to" pointer in
1556 * the step of the source object. If it turns out we need to
1557 * evacuate to an older generation, adjust it here (see comment
1560 if (stp->gen_no < evac_gen) {
1561 #ifdef NO_EAGER_PROMOTION
1562 failed_to_evac = rtsTrue;
1564 stp = &generations[evac_gen].steps[0];
1568 /* chain a new block onto the to-space for the destination step if
1571 if (stp->hp + size >= stp->hpLim) {
1572 gc_alloc_block(stp);
1577 stp->hp = to + size;
1578 for (i = 0; i < size; i++) { // unroll for small i
1581 upd_evacuee((StgClosure *)from,(StgClosure *)to);
1584 // We store the size of the just evacuated object in the LDV word so that
1585 // the profiler can guess the position of the next object later.
1586 SET_EVACUAEE_FOR_LDV(from, size_org);
1588 return (StgClosure *)to;
1591 // Same as copy() above, except the object will be allocated in memory
1592 // that will not be scavenged. Used for object that have no pointer
1594 STATIC_INLINE StgClosure *
1595 copy_noscav(StgClosure *src, nat size, step *stp)
1601 nat size_org = size;
1604 TICK_GC_WORDS_COPIED(size);
1605 /* Find out where we're going, using the handy "to" pointer in
1606 * the step of the source object. If it turns out we need to
1607 * evacuate to an older generation, adjust it here (see comment
1610 if (stp->gen_no < evac_gen) {
1611 #ifdef NO_EAGER_PROMOTION
1612 failed_to_evac = rtsTrue;
1614 stp = &generations[evac_gen].steps[0];
1618 /* chain a new block onto the to-space for the destination step if
1621 if (stp->scavd_hp + size >= stp->scavd_hpLim) {
1622 gc_alloc_scavd_block(stp);
1627 stp->scavd_hp = to + size;
1628 for (i = 0; i < size; i++) { // unroll for small i
1631 upd_evacuee((StgClosure *)from,(StgClosure *)to);
1634 // We store the size of the just evacuated object in the LDV word so that
1635 // the profiler can guess the position of the next object later.
1636 SET_EVACUAEE_FOR_LDV(from, size_org);
1638 return (StgClosure *)to;
1641 /* Special version of copy() for when we only want to copy the info
1642 * pointer of an object, but reserve some padding after it. This is
1643 * used to optimise evacuation of BLACKHOLEs.
1648 copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *stp)
1653 nat size_to_copy_org = size_to_copy;
1656 TICK_GC_WORDS_COPIED(size_to_copy);
1657 if (stp->gen_no < evac_gen) {
1658 #ifdef NO_EAGER_PROMOTION
1659 failed_to_evac = rtsTrue;
1661 stp = &generations[evac_gen].steps[0];
1665 if (stp->hp + size_to_reserve >= stp->hpLim) {
1666 gc_alloc_block(stp);
1669 for(to = stp->hp, from = (P_)src; size_to_copy>0; --size_to_copy) {
1674 stp->hp += size_to_reserve;
1675 upd_evacuee(src,(StgClosure *)dest);
1677 // We store the size of the just evacuated object in the LDV word so that
1678 // the profiler can guess the position of the next object later.
1679 // size_to_copy_org is wrong because the closure already occupies size_to_reserve
1681 SET_EVACUAEE_FOR_LDV(src, size_to_reserve);
1683 if (size_to_reserve - size_to_copy_org > 0)
1684 FILL_SLOP(stp->hp - 1, (int)(size_to_reserve - size_to_copy_org));
1686 return (StgClosure *)dest;
1690 /* -----------------------------------------------------------------------------
1691 Evacuate a large object
1693 This just consists of removing the object from the (doubly-linked)
1694 step->large_objects list, and linking it on to the (singly-linked)
1695 step->new_large_objects list, from where it will be scavenged later.
1697 Convention: bd->flags has BF_EVACUATED set for a large object
1698 that has been evacuated, or unset otherwise.
1699 -------------------------------------------------------------------------- */
1703 evacuate_large(StgPtr p)
1705 bdescr *bd = Bdescr(p);
1708 // object must be at the beginning of the block (or be a ByteArray)
1709 ASSERT(get_itbl((StgClosure *)p)->type == ARR_WORDS ||
1710 (((W_)p & BLOCK_MASK) == 0));
1712 // already evacuated?
1713 if (bd->flags & BF_EVACUATED) {
1714 /* Don't forget to set the failed_to_evac flag if we didn't get
1715 * the desired destination (see comments in evacuate()).
1717 if (bd->gen_no < evac_gen) {
1718 failed_to_evac = rtsTrue;
1719 TICK_GC_FAILED_PROMOTION();
1725 // remove from large_object list
1727 bd->u.back->link = bd->link;
1728 } else { // first object in the list
1729 stp->large_objects = bd->link;
1732 bd->link->u.back = bd->u.back;
1735 /* link it on to the evacuated large object list of the destination step
1738 if (stp->gen_no < evac_gen) {
1739 #ifdef NO_EAGER_PROMOTION
1740 failed_to_evac = rtsTrue;
1742 stp = &generations[evac_gen].steps[0];
1747 bd->gen_no = stp->gen_no;
1748 bd->link = stp->new_large_objects;
1749 stp->new_large_objects = bd;
1750 bd->flags |= BF_EVACUATED;
1753 /* -----------------------------------------------------------------------------
1756 This is called (eventually) for every live object in the system.
1758 The caller to evacuate specifies a desired generation in the
1759 evac_gen global variable. The following conditions apply to
1760 evacuating an object which resides in generation M when we're
1761 collecting up to generation N
1765 else evac to step->to
1767 if M < evac_gen evac to evac_gen, step 0
1769 if the object is already evacuated, then we check which generation
1772 if M >= evac_gen do nothing
1773 if M < evac_gen set failed_to_evac flag to indicate that we
1774 didn't manage to evacuate this object into evac_gen.
1779 evacuate() is the single most important function performance-wise
1780 in the GC. Various things have been tried to speed it up, but as
1781 far as I can tell the code generated by gcc 3.2 with -O2 is about
1782 as good as it's going to get. We pass the argument to evacuate()
1783 in a register using the 'regparm' attribute (see the prototype for
1784 evacuate() near the top of this file).
1786 Changing evacuate() to take an (StgClosure **) rather than
1787 returning the new pointer seems attractive, because we can avoid
1788 writing back the pointer when it hasn't changed (eg. for a static
1789 object, or an object in a generation > N). However, I tried it and
1790 it doesn't help. One reason is that the (StgClosure **) pointer
1791 gets spilled to the stack inside evacuate(), resulting in far more
1792 extra reads/writes than we save.
1793 -------------------------------------------------------------------------- */
1795 REGPARM1 static StgClosure *
1796 evacuate(StgClosure *q)
1803 const StgInfoTable *info;
1806 ASSERT(LOOKS_LIKE_CLOSURE_PTR(q));
1808 if (!HEAP_ALLOCED(q)) {
1810 if (!major_gc) return q;
1813 switch (info->type) {
1816 if (info->srt_bitmap != 0 &&
1817 *THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
1818 *THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
1819 static_objects = (StgClosure *)q;
1824 if (info->srt_bitmap != 0 &&
1825 *FUN_STATIC_LINK((StgClosure *)q) == NULL) {
1826 *FUN_STATIC_LINK((StgClosure *)q) = static_objects;
1827 static_objects = (StgClosure *)q;
1832 /* If q->saved_info != NULL, then it's a revertible CAF - it'll be
1833 * on the CAF list, so don't do anything with it here (we'll
1834 * scavenge it later).
1836 if (((StgIndStatic *)q)->saved_info == NULL
1837 && *IND_STATIC_LINK((StgClosure *)q) == NULL) {
1838 *IND_STATIC_LINK((StgClosure *)q) = static_objects;
1839 static_objects = (StgClosure *)q;
1844 if (*STATIC_LINK(info,(StgClosure *)q) == NULL) {
1845 *STATIC_LINK(info,(StgClosure *)q) = static_objects;
1846 static_objects = (StgClosure *)q;
1850 case CONSTR_INTLIKE:
1851 case CONSTR_CHARLIKE:
1852 case CONSTR_NOCAF_STATIC:
1853 /* no need to put these on the static linked list, they don't need
1859 barf("evacuate(static): strange closure type %d", (int)(info->type));
1865 if (bd->gen_no > N) {
1866 /* Can't evacuate this object, because it's in a generation
1867 * older than the ones we're collecting. Let's hope that it's
1868 * in evac_gen or older, or we will have to arrange to track
1869 * this pointer using the mutable list.
1871 if (bd->gen_no < evac_gen) {
1873 failed_to_evac = rtsTrue;
1874 TICK_GC_FAILED_PROMOTION();
1879 if ((bd->flags & (BF_LARGE | BF_COMPACTED | BF_EVACUATED)) != 0) {
1881 /* pointer into to-space: just return it. This normally
1882 * shouldn't happen, but alllowing it makes certain things
1883 * slightly easier (eg. the mutable list can contain the same
1884 * object twice, for example).
1886 if (bd->flags & BF_EVACUATED) {
1887 if (bd->gen_no < evac_gen) {
1888 failed_to_evac = rtsTrue;
1889 TICK_GC_FAILED_PROMOTION();
1894 /* evacuate large objects by re-linking them onto a different list.
1896 if (bd->flags & BF_LARGE) {
1898 if (info->type == TSO &&
1899 ((StgTSO *)q)->what_next == ThreadRelocated) {
1900 q = (StgClosure *)((StgTSO *)q)->link;
1903 evacuate_large((P_)q);
1907 /* If the object is in a step that we're compacting, then we
1908 * need to use an alternative evacuate procedure.
1910 if (bd->flags & BF_COMPACTED) {
1911 if (!is_marked((P_)q,bd)) {
1913 if (mark_stack_full()) {
1914 mark_stack_overflowed = rtsTrue;
1917 push_mark_stack((P_)q);
1927 switch (info->type) {
1931 return copy(q,sizeW_fromITBL(info),stp);
1935 StgWord w = (StgWord)q->payload[0];
1936 if (q->header.info == Czh_con_info &&
1937 // unsigned, so always true: (StgChar)w >= MIN_CHARLIKE &&
1938 (StgChar)w <= MAX_CHARLIKE) {
1939 return (StgClosure *)CHARLIKE_CLOSURE((StgChar)w);
1941 if (q->header.info == Izh_con_info &&
1942 (StgInt)w >= MIN_INTLIKE && (StgInt)w <= MAX_INTLIKE) {
1943 return (StgClosure *)INTLIKE_CLOSURE((StgInt)w);
1946 return copy_noscav(q,sizeofW(StgHeader)+1,stp);
1952 return copy(q,sizeofW(StgHeader)+1,stp);
1956 return copy(q,sizeofW(StgThunk)+1,stp);
1961 #ifdef NO_PROMOTE_THUNKS
1962 if (bd->gen_no == 0 &&
1963 bd->step->no != 0 &&
1964 bd->step->no == generations[bd->gen_no].n_steps-1) {
1968 return copy(q,sizeofW(StgThunk)+2,stp);
1975 return copy(q,sizeofW(StgHeader)+2,stp);
1978 return copy_noscav(q,sizeofW(StgHeader)+2,stp);
1981 return copy(q,thunk_sizeW_fromITBL(info),stp);
1986 case IND_OLDGEN_PERM:
1989 return copy(q,sizeW_fromITBL(info),stp);
1992 return copy(q,bco_sizeW((StgBCO *)q),stp);
1995 case SE_CAF_BLACKHOLE:
1998 return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
2000 case THUNK_SELECTOR:
2004 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
2005 return copy(q,THUNK_SELECTOR_sizeW(),stp);
2008 p = eval_thunk_selector(info->layout.selector_offset,
2012 return copy(q,THUNK_SELECTOR_sizeW(),stp);
2015 // q is still BLACKHOLE'd.
2016 thunk_selector_depth++;
2018 thunk_selector_depth--;
2020 // Update the THUNK_SELECTOR with an indirection to the
2021 // EVACUATED closure now at p. Why do this rather than
2022 // upd_evacuee(q,p)? Because we have an invariant that an
2023 // EVACUATED closure always points to an object in the
2024 // same or an older generation (required by the short-cut
2025 // test in the EVACUATED case, below).
2026 SET_INFO(q, &stg_IND_info);
2027 ((StgInd *)q)->indirectee = p;
2030 // We store the size of the just evacuated object in the
2031 // LDV word so that the profiler can guess the position of
2032 // the next object later.
2033 SET_EVACUAEE_FOR_LDV(q, THUNK_SELECTOR_sizeW());
2041 // follow chains of indirections, don't evacuate them
2042 q = ((StgInd*)q)->indirectee;
2054 case CATCH_STM_FRAME:
2055 case CATCH_RETRY_FRAME:
2056 case ATOMICALLY_FRAME:
2057 // shouldn't see these
2058 barf("evacuate: stack frame at %p\n", q);
2061 return copy(q,pap_sizeW((StgPAP*)q),stp);
2064 return copy(q,ap_sizeW((StgAP*)q),stp);
2067 return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp);
2070 /* Already evacuated, just return the forwarding address.
2071 * HOWEVER: if the requested destination generation (evac_gen) is
2072 * older than the actual generation (because the object was
2073 * already evacuated to a younger generation) then we have to
2074 * set the failed_to_evac flag to indicate that we couldn't
2075 * manage to promote the object to the desired generation.
2078 * Optimisation: the check is fairly expensive, but we can often
2079 * shortcut it if either the required generation is 0, or the
2080 * current object (the EVACUATED) is in a high enough generation.
2081 * We know that an EVACUATED always points to an object in the
2082 * same or an older generation. stp is the lowest step that the
2083 * current object would be evacuated to, so we only do the full
2084 * check if stp is too low.
2086 if (evac_gen > 0 && stp->gen_no < evac_gen) { // optimisation
2087 StgClosure *p = ((StgEvacuated*)q)->evacuee;
2088 if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < evac_gen) {
2089 failed_to_evac = rtsTrue;
2090 TICK_GC_FAILED_PROMOTION();
2093 return ((StgEvacuated*)q)->evacuee;
2096 // just copy the block
2097 return copy_noscav(q,arr_words_sizeW((StgArrWords *)q),stp);
2100 case MUT_ARR_PTRS_FROZEN:
2101 case MUT_ARR_PTRS_FROZEN0:
2102 // just copy the block
2103 return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
2107 StgTSO *tso = (StgTSO *)q;
2109 /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
2111 if (tso->what_next == ThreadRelocated) {
2112 q = (StgClosure *)tso->link;
2116 /* To evacuate a small TSO, we need to relocate the update frame
2123 new_tso = (StgTSO *)copyPart((StgClosure *)tso,
2125 sizeofW(StgTSO), stp);
2126 move_TSO(tso, new_tso);
2127 for (p = tso->sp, q = new_tso->sp;
2128 p < tso->stack+tso->stack_size;) {
2132 return (StgClosure *)new_tso;
2139 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
2140 to = copy(q,BLACKHOLE_sizeW(),stp);
2141 //ToDo: derive size etc from reverted IP
2142 //to = copy(q,size,stp);
2144 debugBelch("@@ evacuate: RBH %p (%s) to %p (%s)",
2145 q, info_type(q), to, info_type(to)));
2150 ASSERT(sizeofW(StgBlockedFetch) >= MIN_NONUPD_SIZE);
2151 to = copy(q,sizeofW(StgBlockedFetch),stp);
2153 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
2154 q, info_type(q), to, info_type(to)));
2161 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
2162 to = copy(q,sizeofW(StgFetchMe),stp);
2164 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
2165 q, info_type(q), to, info_type(to)));
2169 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
2170 to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
2172 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
2173 q, info_type(q), to, info_type(to)));
2178 return copy(q,sizeofW(StgTRecHeader),stp);
2180 case TVAR_WAIT_QUEUE:
2181 return copy(q,sizeofW(StgTVarWaitQueue),stp);
2184 return copy(q,sizeofW(StgTVar),stp);
2187 return copy(q,sizeofW(StgTRecChunk),stp);
2190 barf("evacuate: strange closure type %d", (int)(info->type));
2196 /* -----------------------------------------------------------------------------
2197 Evaluate a THUNK_SELECTOR if possible.
2199 returns: NULL if we couldn't evaluate this THUNK_SELECTOR, or
2200 a closure pointer if we evaluated it and this is the result. Note
2201 that "evaluating" the THUNK_SELECTOR doesn't necessarily mean
2202 reducing it to HNF, just that we have eliminated the selection.
2203 The result might be another thunk, or even another THUNK_SELECTOR.
2205 If the return value is non-NULL, the original selector thunk has
2206 been BLACKHOLE'd, and should be updated with an indirection or a
2207 forwarding pointer. If the return value is NULL, then the selector
2211 ToDo: the treatment of THUNK_SELECTORS could be improved in the
2212 following way (from a suggestion by Ian Lynagh):
2214 We can have a chain like this:
2218 |-----> sel_0 --> (a,b)
2220 |-----> sel_0 --> ...
2222 and the depth limit means we don't go all the way to the end of the
2223 chain, which results in a space leak. This affects the recursive
2224 call to evacuate() in the THUNK_SELECTOR case in evacuate(): *not*
2225 the recursive call to eval_thunk_selector() in
2226 eval_thunk_selector().
2228 We could eliminate the depth bound in this case, in the following
2231 - traverse the chain once to discover the *value* of the
2232 THUNK_SELECTOR. Mark all THUNK_SELECTORS that we
2233 visit on the way as having been visited already (somehow).
2235 - in a second pass, traverse the chain again updating all
2236 THUNK_SEELCTORS that we find on the way with indirections to
2239 - if we encounter a "marked" THUNK_SELECTOR in a normal
2240 evacuate(), we konw it can't be updated so just evac it.
2242 Program that illustrates the problem:
2245 foo (x:xs) = let (ys, zs) = foo xs
2246 in if x >= 0 then (x:ys, zs) else (ys, x:zs)
2248 main = bar [1..(100000000::Int)]
2249 bar xs = (\(ys, zs) -> print ys >> print zs) (foo xs)
2251 -------------------------------------------------------------------------- */
2253 static inline rtsBool
2254 is_to_space ( StgClosure *p )
2258 bd = Bdescr((StgPtr)p);
2259 if (HEAP_ALLOCED(p) &&
2260 ((bd->flags & BF_EVACUATED)
2261 || ((bd->flags & BF_COMPACTED) &&
2262 is_marked((P_)p,bd)))) {
2270 eval_thunk_selector( nat field, StgSelector * p )
2273 const StgInfoTable *info_ptr;
2274 StgClosure *selectee;
2276 selectee = p->selectee;
2278 // Save the real info pointer (NOTE: not the same as get_itbl()).
2279 info_ptr = p->header.info;
2281 // If the THUNK_SELECTOR is in a generation that we are not
2282 // collecting, then bail out early. We won't be able to save any
2283 // space in any case, and updating with an indirection is trickier
2285 if (Bdescr((StgPtr)p)->gen_no > N) {
2289 // BLACKHOLE the selector thunk, since it is now under evaluation.
2290 // This is important to stop us going into an infinite loop if
2291 // this selector thunk eventually refers to itself.
2292 SET_INFO(p,&stg_BLACKHOLE_info);
2296 // We don't want to end up in to-space, because this causes
2297 // problems when the GC later tries to evacuate the result of
2298 // eval_thunk_selector(). There are various ways this could
2301 // 1. following an IND_STATIC
2303 // 2. when the old generation is compacted, the mark phase updates
2304 // from-space pointers to be to-space pointers, and we can't
2305 // reliably tell which we're following (eg. from an IND_STATIC).
2307 // 3. compacting GC again: if we're looking at a constructor in
2308 // the compacted generation, it might point directly to objects
2309 // in to-space. We must bale out here, otherwise doing the selection
2310 // will result in a to-space pointer being returned.
2312 // (1) is dealt with using a BF_EVACUATED test on the
2313 // selectee. (2) and (3): we can tell if we're looking at an
2314 // object in the compacted generation that might point to
2315 // to-space objects by testing that (a) it is BF_COMPACTED, (b)
2316 // the compacted generation is being collected, and (c) the
2317 // object is marked. Only a marked object may have pointers that
2318 // point to to-space objects, because that happens when
2321 // The to-space test is now embodied in the in_to_space() inline
2322 // function, as it is re-used below.
2324 if (is_to_space(selectee)) {
2328 info = get_itbl(selectee);
2329 switch (info->type) {
2337 case CONSTR_NOCAF_STATIC:
2338 // check that the size is in range
2339 ASSERT(field < (StgWord32)(info->layout.payload.ptrs +
2340 info->layout.payload.nptrs));
2342 // Select the right field from the constructor, and check
2343 // that the result isn't in to-space. It might be in
2344 // to-space if, for example, this constructor contains
2345 // pointers to younger-gen objects (and is on the mut-once
2350 q = selectee->payload[field];
2351 if (is_to_space(q)) {
2361 case IND_OLDGEN_PERM:
2363 selectee = ((StgInd *)selectee)->indirectee;
2367 // We don't follow pointers into to-space; the constructor
2368 // has already been evacuated, so we won't save any space
2369 // leaks by evaluating this selector thunk anyhow.
2372 case THUNK_SELECTOR:
2376 // check that we don't recurse too much, re-using the
2377 // depth bound also used in evacuate().
2378 if (thunk_selector_depth >= MAX_THUNK_SELECTOR_DEPTH) {
2381 thunk_selector_depth++;
2383 val = eval_thunk_selector(info->layout.selector_offset,
2384 (StgSelector *)selectee);
2386 thunk_selector_depth--;
2391 // We evaluated this selector thunk, so update it with
2392 // an indirection. NOTE: we don't use UPD_IND here,
2393 // because we are guaranteed that p is in a generation
2394 // that we are collecting, and we never want to put the
2395 // indirection on a mutable list.
2397 // For the purposes of LDV profiling, we have destroyed
2398 // the original selector thunk.
2399 SET_INFO(p, info_ptr);
2400 LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(selectee);
2402 ((StgInd *)selectee)->indirectee = val;
2403 SET_INFO(selectee,&stg_IND_info);
2405 // For the purposes of LDV profiling, we have created an
2407 LDV_RECORD_CREATE(selectee);
2424 case SE_CAF_BLACKHOLE:
2436 // not evaluated yet
2440 barf("eval_thunk_selector: strange selectee %d",
2445 // We didn't manage to evaluate this thunk; restore the old info pointer
2446 SET_INFO(p, info_ptr);
2450 /* -----------------------------------------------------------------------------
2451 move_TSO is called to update the TSO structure after it has been
2452 moved from one place to another.
2453 -------------------------------------------------------------------------- */
2456 move_TSO (StgTSO *src, StgTSO *dest)
2460 // relocate the stack pointer...
2461 diff = (StgPtr)dest - (StgPtr)src; // In *words*
2462 dest->sp = (StgPtr)dest->sp + diff;
2465 /* Similar to scavenge_large_bitmap(), but we don't write back the
2466 * pointers we get back from evacuate().
2469 scavenge_large_srt_bitmap( StgLargeSRT *large_srt )
2476 bitmap = large_srt->l.bitmap[b];
2477 size = (nat)large_srt->l.size;
2478 p = (StgClosure **)large_srt->srt;
2479 for (i = 0; i < size; ) {
2480 if ((bitmap & 1) != 0) {
2485 if (i % BITS_IN(W_) == 0) {
2487 bitmap = large_srt->l.bitmap[b];
2489 bitmap = bitmap >> 1;
2494 /* evacuate the SRT. If srt_bitmap is zero, then there isn't an
2495 * srt field in the info table. That's ok, because we'll
2496 * never dereference it.
2499 scavenge_srt (StgClosure **srt, nat srt_bitmap)
2504 bitmap = srt_bitmap;
2507 if (bitmap == (StgHalfWord)(-1)) {
2508 scavenge_large_srt_bitmap( (StgLargeSRT *)srt );
2512 while (bitmap != 0) {
2513 if ((bitmap & 1) != 0) {
2514 #ifdef ENABLE_WIN32_DLL_SUPPORT
2515 // Special-case to handle references to closures hiding out in DLLs, since
2516 // double indirections required to get at those. The code generator knows
2517 // which is which when generating the SRT, so it stores the (indirect)
2518 // reference to the DLL closure in the table by first adding one to it.
2519 // We check for this here, and undo the addition before evacuating it.
2521 // If the SRT entry hasn't got bit 0 set, the SRT entry points to a
2522 // closure that's fixed at link-time, and no extra magic is required.
2523 if ( (unsigned long)(*srt) & 0x1 ) {
2524 evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
2533 bitmap = bitmap >> 1;
2539 scavenge_thunk_srt(const StgInfoTable *info)
2541 StgThunkInfoTable *thunk_info;
2543 if (!major_gc) return;
2545 thunk_info = itbl_to_thunk_itbl(info);
2546 scavenge_srt((StgClosure **)GET_SRT(thunk_info), thunk_info->i.srt_bitmap);
2550 scavenge_fun_srt(const StgInfoTable *info)
2552 StgFunInfoTable *fun_info;
2554 if (!major_gc) return;
2556 fun_info = itbl_to_fun_itbl(info);
2557 scavenge_srt((StgClosure **)GET_FUN_SRT(fun_info), fun_info->i.srt_bitmap);
2560 /* -----------------------------------------------------------------------------
2562 -------------------------------------------------------------------------- */
2565 scavengeTSO (StgTSO *tso)
2567 if ( tso->why_blocked == BlockedOnMVar
2568 || tso->why_blocked == BlockedOnBlackHole
2569 || tso->why_blocked == BlockedOnException
2571 || tso->why_blocked == BlockedOnGA
2572 || tso->why_blocked == BlockedOnGA_NoSend
2575 tso->block_info.closure = evacuate(tso->block_info.closure);
2577 if ( tso->blocked_exceptions != NULL ) {
2578 tso->blocked_exceptions =
2579 (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
2582 // We don't always chase the link field: TSOs on the blackhole
2583 // queue are not automatically alive, so the link field is a
2584 // "weak" pointer in that case.
2585 if (tso->why_blocked != BlockedOnBlackHole) {
2586 tso->link = (StgTSO *)evacuate((StgClosure *)tso->link);
2589 // scavange current transaction record
2590 tso->trec = (StgTRecHeader *)evacuate((StgClosure *)tso->trec);
2592 // scavenge this thread's stack
2593 scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
2596 /* -----------------------------------------------------------------------------
2597 Blocks of function args occur on the stack (at the top) and
2599 -------------------------------------------------------------------------- */
2601 STATIC_INLINE StgPtr
2602 scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
2609 switch (fun_info->f.fun_type) {
2611 bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
2612 size = BITMAP_SIZE(fun_info->f.b.bitmap);
2615 size = GET_FUN_LARGE_BITMAP(fun_info)->size;
2616 scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
2620 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2621 size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->f.fun_type]);
2624 if ((bitmap & 1) == 0) {
2625 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2628 bitmap = bitmap >> 1;
2636 STATIC_INLINE StgPtr
2637 scavenge_PAP_payload (StgClosure *fun, StgClosure **payload, StgWord size)
2641 StgFunInfoTable *fun_info;
2643 fun_info = get_fun_itbl(fun);
2644 ASSERT(fun_info->i.type != PAP);
2645 p = (StgPtr)payload;
2647 switch (fun_info->f.fun_type) {
2649 bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
2652 scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
2656 scavenge_large_bitmap((StgPtr)payload, BCO_BITMAP(fun), size);
2660 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2663 if ((bitmap & 1) == 0) {
2664 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2667 bitmap = bitmap >> 1;
2675 STATIC_INLINE StgPtr
2676 scavenge_PAP (StgPAP *pap)
2678 pap->fun = evacuate(pap->fun);
2679 return scavenge_PAP_payload (pap->fun, pap->payload, pap->n_args);
2682 STATIC_INLINE StgPtr
2683 scavenge_AP (StgAP *ap)
2685 ap->fun = evacuate(ap->fun);
2686 return scavenge_PAP_payload (ap->fun, ap->payload, ap->n_args);
2689 /* -----------------------------------------------------------------------------
2690 Scavenge a given step until there are no more objects in this step
2693 evac_gen is set by the caller to be either zero (for a step in a
2694 generation < N) or G where G is the generation of the step being
2697 We sometimes temporarily change evac_gen back to zero if we're
2698 scavenging a mutable object where early promotion isn't such a good
2700 -------------------------------------------------------------------------- */
2708 nat saved_evac_gen = evac_gen;
2713 failed_to_evac = rtsFalse;
2715 /* scavenge phase - standard breadth-first scavenging of the
2719 while (bd != stp->hp_bd || p < stp->hp) {
2721 // If we're at the end of this block, move on to the next block
2722 if (bd != stp->hp_bd && p == bd->free) {
2728 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2729 info = get_itbl((StgClosure *)p);
2731 ASSERT(thunk_selector_depth == 0);
2734 switch (info->type) {
2738 StgMVar *mvar = ((StgMVar *)p);
2740 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
2741 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
2742 mvar->value = evacuate((StgClosure *)mvar->value);
2743 evac_gen = saved_evac_gen;
2744 failed_to_evac = rtsTrue; // mutable.
2745 p += sizeofW(StgMVar);
2750 scavenge_fun_srt(info);
2751 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2752 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2753 p += sizeofW(StgHeader) + 2;
2757 scavenge_thunk_srt(info);
2758 ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
2759 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2760 p += sizeofW(StgThunk) + 2;
2764 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2765 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2766 p += sizeofW(StgHeader) + 2;
2770 scavenge_thunk_srt(info);
2771 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2772 p += sizeofW(StgThunk) + 1;
2776 scavenge_fun_srt(info);
2778 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2779 p += sizeofW(StgHeader) + 1;
2783 scavenge_thunk_srt(info);
2784 p += sizeofW(StgThunk) + 1;
2788 scavenge_fun_srt(info);
2790 p += sizeofW(StgHeader) + 1;
2794 scavenge_thunk_srt(info);
2795 p += sizeofW(StgThunk) + 2;
2799 scavenge_fun_srt(info);
2801 p += sizeofW(StgHeader) + 2;
2805 scavenge_thunk_srt(info);
2806 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2807 p += sizeofW(StgThunk) + 2;
2811 scavenge_fun_srt(info);
2813 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2814 p += sizeofW(StgHeader) + 2;
2818 scavenge_fun_srt(info);
2825 scavenge_thunk_srt(info);
2826 end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
2827 for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
2828 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2830 p += info->layout.payload.nptrs;
2841 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2842 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2843 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2845 p += info->layout.payload.nptrs;
2850 StgBCO *bco = (StgBCO *)p;
2851 bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
2852 bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
2853 bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
2854 bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
2855 p += bco_sizeW(bco);
2860 if (stp->gen->no != 0) {
2863 // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an
2864 // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
2865 LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
2868 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
2870 SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
2872 // We pretend that p has just been created.
2873 LDV_RECORD_CREATE((StgClosure *)p);
2876 case IND_OLDGEN_PERM:
2877 ((StgInd *)p)->indirectee = evacuate(((StgInd *)p)->indirectee);
2878 p += sizeofW(StgInd);
2883 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2884 evac_gen = saved_evac_gen;
2885 failed_to_evac = rtsTrue; // mutable anyhow
2886 p += sizeofW(StgMutVar);
2890 case SE_CAF_BLACKHOLE:
2893 p += BLACKHOLE_sizeW();
2896 case THUNK_SELECTOR:
2898 StgSelector *s = (StgSelector *)p;
2899 s->selectee = evacuate(s->selectee);
2900 p += THUNK_SELECTOR_sizeW();
2904 // A chunk of stack saved in a heap object
2907 StgAP_STACK *ap = (StgAP_STACK *)p;
2909 ap->fun = evacuate(ap->fun);
2910 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2911 p = (StgPtr)ap->payload + ap->size;
2916 p = scavenge_PAP((StgPAP *)p);
2920 p = scavenge_AP((StgAP *)p);
2924 // nothing to follow
2925 p += arr_words_sizeW((StgArrWords *)p);
2929 // follow everything
2933 evac_gen = 0; // repeatedly mutable
2934 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2935 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2936 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2938 evac_gen = saved_evac_gen;
2939 failed_to_evac = rtsTrue; // mutable anyhow.
2943 case MUT_ARR_PTRS_FROZEN:
2944 case MUT_ARR_PTRS_FROZEN0:
2945 // follow everything
2949 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2950 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2951 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2953 // it's tempting to recordMutable() if failed_to_evac is
2954 // false, but that breaks some assumptions (eg. every
2955 // closure on the mutable list is supposed to have the MUT
2956 // flag set, and MUT_ARR_PTRS_FROZEN doesn't).
2962 StgTSO *tso = (StgTSO *)p;
2965 evac_gen = saved_evac_gen;
2966 failed_to_evac = rtsTrue; // mutable anyhow.
2967 p += tso_sizeW(tso);
2975 nat size, ptrs, nonptrs, vhs;
2977 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2979 StgRBH *rbh = (StgRBH *)p;
2980 (StgClosure *)rbh->blocking_queue =
2981 evacuate((StgClosure *)rbh->blocking_queue);
2982 failed_to_evac = rtsTrue; // mutable anyhow.
2984 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2985 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2986 // ToDo: use size of reverted closure here!
2987 p += BLACKHOLE_sizeW();
2993 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2994 // follow the pointer to the node which is being demanded
2995 (StgClosure *)bf->node =
2996 evacuate((StgClosure *)bf->node);
2997 // follow the link to the rest of the blocking queue
2998 (StgClosure *)bf->link =
2999 evacuate((StgClosure *)bf->link);
3001 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3002 bf, info_type((StgClosure *)bf),
3003 bf->node, info_type(bf->node)));
3004 p += sizeofW(StgBlockedFetch);
3012 p += sizeofW(StgFetchMe);
3013 break; // nothing to do in this case
3017 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3018 (StgClosure *)fmbq->blocking_queue =
3019 evacuate((StgClosure *)fmbq->blocking_queue);
3021 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3022 p, info_type((StgClosure *)p)));
3023 p += sizeofW(StgFetchMeBlockingQueue);
3028 case TVAR_WAIT_QUEUE:
3030 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3032 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3033 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3034 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3035 evac_gen = saved_evac_gen;
3036 failed_to_evac = rtsTrue; // mutable
3037 p += sizeofW(StgTVarWaitQueue);
3043 StgTVar *tvar = ((StgTVar *) p);
3045 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3046 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3048 tvar->last_update_by = (StgTRecHeader *)evacuate((StgClosure*)tvar->last_update_by);
3050 evac_gen = saved_evac_gen;
3051 failed_to_evac = rtsTrue; // mutable
3052 p += sizeofW(StgTVar);
3058 StgTRecHeader *trec = ((StgTRecHeader *) p);
3060 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3061 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3062 evac_gen = saved_evac_gen;
3063 failed_to_evac = rtsTrue; // mutable
3064 p += sizeofW(StgTRecHeader);
3071 StgTRecChunk *tc = ((StgTRecChunk *) p);
3072 TRecEntry *e = &(tc -> entries[0]);
3074 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3075 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3076 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3077 e->expected_value = evacuate((StgClosure*)e->expected_value);
3078 e->new_value = evacuate((StgClosure*)e->new_value);
3080 evac_gen = saved_evac_gen;
3081 failed_to_evac = rtsTrue; // mutable
3082 p += sizeofW(StgTRecChunk);
3087 barf("scavenge: unimplemented/strange closure type %d @ %p",
3092 * We need to record the current object on the mutable list if
3093 * (a) It is actually mutable, or
3094 * (b) It contains pointers to a younger generation.
3095 * Case (b) arises if we didn't manage to promote everything that
3096 * the current object points to into the current generation.
3098 if (failed_to_evac) {
3099 failed_to_evac = rtsFalse;
3100 if (stp->gen_no > 0) {
3101 recordMutableGen((StgClosure *)q, stp->gen);
3110 /* -----------------------------------------------------------------------------
3111 Scavenge everything on the mark stack.
3113 This is slightly different from scavenge():
3114 - we don't walk linearly through the objects, so the scavenger
3115 doesn't need to advance the pointer on to the next object.
3116 -------------------------------------------------------------------------- */
3119 scavenge_mark_stack(void)
3125 evac_gen = oldest_gen->no;
3126 saved_evac_gen = evac_gen;
3129 while (!mark_stack_empty()) {
3130 p = pop_mark_stack();
3132 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3133 info = get_itbl((StgClosure *)p);
3136 switch (info->type) {
3140 StgMVar *mvar = ((StgMVar *)p);
3142 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
3143 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
3144 mvar->value = evacuate((StgClosure *)mvar->value);
3145 evac_gen = saved_evac_gen;
3146 failed_to_evac = rtsTrue; // mutable.
3151 scavenge_fun_srt(info);
3152 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
3153 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3157 scavenge_thunk_srt(info);
3158 ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
3159 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
3163 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
3164 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3169 scavenge_fun_srt(info);
3170 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3175 scavenge_thunk_srt(info);
3176 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
3181 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3186 scavenge_fun_srt(info);
3191 scavenge_thunk_srt(info);
3199 scavenge_fun_srt(info);
3206 scavenge_thunk_srt(info);
3207 end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
3208 for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
3209 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3221 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3222 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
3223 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3229 StgBCO *bco = (StgBCO *)p;
3230 bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
3231 bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
3232 bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
3233 bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
3238 // don't need to do anything here: the only possible case
3239 // is that we're in a 1-space compacting collector, with
3240 // no "old" generation.
3244 case IND_OLDGEN_PERM:
3245 ((StgInd *)p)->indirectee =
3246 evacuate(((StgInd *)p)->indirectee);
3251 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3252 evac_gen = saved_evac_gen;
3253 failed_to_evac = rtsTrue;
3257 case SE_CAF_BLACKHOLE:
3263 case THUNK_SELECTOR:
3265 StgSelector *s = (StgSelector *)p;
3266 s->selectee = evacuate(s->selectee);
3270 // A chunk of stack saved in a heap object
3273 StgAP_STACK *ap = (StgAP_STACK *)p;
3275 ap->fun = evacuate(ap->fun);
3276 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3281 scavenge_PAP((StgPAP *)p);
3285 scavenge_AP((StgAP *)p);
3289 // follow everything
3293 evac_gen = 0; // repeatedly mutable
3294 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3295 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3296 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3298 evac_gen = saved_evac_gen;
3299 failed_to_evac = rtsTrue; // mutable anyhow.
3303 case MUT_ARR_PTRS_FROZEN:
3304 case MUT_ARR_PTRS_FROZEN0:
3305 // follow everything
3309 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3310 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3311 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3318 StgTSO *tso = (StgTSO *)p;
3321 evac_gen = saved_evac_gen;
3322 failed_to_evac = rtsTrue;
3330 nat size, ptrs, nonptrs, vhs;
3332 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3334 StgRBH *rbh = (StgRBH *)p;
3335 bh->blocking_queue =
3336 (StgTSO *)evacuate((StgClosure *)bh->blocking_queue);
3337 failed_to_evac = rtsTrue; // mutable anyhow.
3339 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3340 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3346 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3347 // follow the pointer to the node which is being demanded
3348 (StgClosure *)bf->node =
3349 evacuate((StgClosure *)bf->node);
3350 // follow the link to the rest of the blocking queue
3351 (StgClosure *)bf->link =
3352 evacuate((StgClosure *)bf->link);
3354 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3355 bf, info_type((StgClosure *)bf),
3356 bf->node, info_type(bf->node)));
3364 break; // nothing to do in this case
3368 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3369 (StgClosure *)fmbq->blocking_queue =
3370 evacuate((StgClosure *)fmbq->blocking_queue);
3372 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3373 p, info_type((StgClosure *)p)));
3378 case TVAR_WAIT_QUEUE:
3380 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3382 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3383 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3384 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3385 evac_gen = saved_evac_gen;
3386 failed_to_evac = rtsTrue; // mutable
3392 StgTVar *tvar = ((StgTVar *) p);
3394 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3395 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3397 tvar->last_update_by = (StgTRecHeader *)evacuate((StgClosure*)tvar->last_update_by);
3399 evac_gen = saved_evac_gen;
3400 failed_to_evac = rtsTrue; // mutable
3407 StgTRecChunk *tc = ((StgTRecChunk *) p);
3408 TRecEntry *e = &(tc -> entries[0]);
3410 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3411 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3412 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3413 e->expected_value = evacuate((StgClosure*)e->expected_value);
3414 e->new_value = evacuate((StgClosure*)e->new_value);
3416 evac_gen = saved_evac_gen;
3417 failed_to_evac = rtsTrue; // mutable
3423 StgTRecHeader *trec = ((StgTRecHeader *) p);
3425 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3426 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3427 evac_gen = saved_evac_gen;
3428 failed_to_evac = rtsTrue; // mutable
3433 barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p",
3437 if (failed_to_evac) {
3438 failed_to_evac = rtsFalse;
3440 recordMutableGen((StgClosure *)q, &generations[evac_gen]);
3444 // mark the next bit to indicate "scavenged"
3445 mark(q+1, Bdescr(q));
3447 } // while (!mark_stack_empty())
3449 // start a new linear scan if the mark stack overflowed at some point
3450 if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
3451 IF_DEBUG(gc, debugBelch("scavenge_mark_stack: starting linear scan"));
3452 mark_stack_overflowed = rtsFalse;
3453 oldgen_scan_bd = oldest_gen->steps[0].old_blocks;
3454 oldgen_scan = oldgen_scan_bd->start;
3457 if (oldgen_scan_bd) {
3458 // push a new thing on the mark stack
3460 // find a closure that is marked but not scavenged, and start
3462 while (oldgen_scan < oldgen_scan_bd->free
3463 && !is_marked(oldgen_scan,oldgen_scan_bd)) {
3467 if (oldgen_scan < oldgen_scan_bd->free) {
3469 // already scavenged?
3470 if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
3471 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3474 push_mark_stack(oldgen_scan);
3475 // ToDo: bump the linear scan by the actual size of the object
3476 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3480 oldgen_scan_bd = oldgen_scan_bd->link;
3481 if (oldgen_scan_bd != NULL) {
3482 oldgen_scan = oldgen_scan_bd->start;
3488 /* -----------------------------------------------------------------------------
3489 Scavenge one object.
3491 This is used for objects that are temporarily marked as mutable
3492 because they contain old-to-new generation pointers. Only certain
3493 objects can have this property.
3494 -------------------------------------------------------------------------- */
3497 scavenge_one(StgPtr p)
3499 const StgInfoTable *info;
3500 nat saved_evac_gen = evac_gen;
3503 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3504 info = get_itbl((StgClosure *)p);
3506 switch (info->type) {
3510 StgMVar *mvar = ((StgMVar *)p);
3512 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
3513 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
3514 mvar->value = evacuate((StgClosure *)mvar->value);
3515 evac_gen = saved_evac_gen;
3516 failed_to_evac = rtsTrue; // mutable.
3529 end = (StgPtr)((StgThunk *)p)->payload + info->layout.payload.ptrs;
3530 for (q = (StgPtr)((StgThunk *)p)->payload; q < end; q++) {
3531 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3537 case FUN_1_0: // hardly worth specialising these guys
3553 end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3554 for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
3555 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3562 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3563 evac_gen = saved_evac_gen;
3564 failed_to_evac = rtsTrue; // mutable anyhow
3568 case SE_CAF_BLACKHOLE:
3573 case THUNK_SELECTOR:
3575 StgSelector *s = (StgSelector *)p;
3576 s->selectee = evacuate(s->selectee);
3582 StgAP_STACK *ap = (StgAP_STACK *)p;
3584 ap->fun = evacuate(ap->fun);
3585 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3586 p = (StgPtr)ap->payload + ap->size;
3591 p = scavenge_PAP((StgPAP *)p);
3595 p = scavenge_AP((StgAP *)p);
3599 // nothing to follow
3604 // follow everything
3607 evac_gen = 0; // repeatedly mutable
3608 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3609 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3610 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3612 evac_gen = saved_evac_gen;
3613 failed_to_evac = rtsTrue;
3617 case MUT_ARR_PTRS_FROZEN:
3618 case MUT_ARR_PTRS_FROZEN0:
3620 // follow everything
3623 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3624 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3625 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3632 StgTSO *tso = (StgTSO *)p;
3634 evac_gen = 0; // repeatedly mutable
3636 evac_gen = saved_evac_gen;
3637 failed_to_evac = rtsTrue;
3645 nat size, ptrs, nonptrs, vhs;
3647 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3649 StgRBH *rbh = (StgRBH *)p;
3650 (StgClosure *)rbh->blocking_queue =
3651 evacuate((StgClosure *)rbh->blocking_queue);
3652 failed_to_evac = rtsTrue; // mutable anyhow.
3654 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3655 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3656 // ToDo: use size of reverted closure here!
3662 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3663 // follow the pointer to the node which is being demanded
3664 (StgClosure *)bf->node =
3665 evacuate((StgClosure *)bf->node);
3666 // follow the link to the rest of the blocking queue
3667 (StgClosure *)bf->link =
3668 evacuate((StgClosure *)bf->link);
3670 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3671 bf, info_type((StgClosure *)bf),
3672 bf->node, info_type(bf->node)));
3680 break; // nothing to do in this case
3684 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3685 (StgClosure *)fmbq->blocking_queue =
3686 evacuate((StgClosure *)fmbq->blocking_queue);
3688 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3689 p, info_type((StgClosure *)p)));
3694 case TVAR_WAIT_QUEUE:
3696 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3698 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3699 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3700 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3701 evac_gen = saved_evac_gen;
3702 failed_to_evac = rtsTrue; // mutable
3708 StgTVar *tvar = ((StgTVar *) p);
3710 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3711 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3713 tvar->last_update_by = (StgTRecHeader *)evacuate((StgClosure*)tvar->last_update_by);
3715 evac_gen = saved_evac_gen;
3716 failed_to_evac = rtsTrue; // mutable
3722 StgTRecHeader *trec = ((StgTRecHeader *) p);
3724 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3725 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3726 evac_gen = saved_evac_gen;
3727 failed_to_evac = rtsTrue; // mutable
3734 StgTRecChunk *tc = ((StgTRecChunk *) p);
3735 TRecEntry *e = &(tc -> entries[0]);
3737 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3738 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3739 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3740 e->expected_value = evacuate((StgClosure*)e->expected_value);
3741 e->new_value = evacuate((StgClosure*)e->new_value);
3743 evac_gen = saved_evac_gen;
3744 failed_to_evac = rtsTrue; // mutable
3749 case IND_OLDGEN_PERM:
3752 /* Careful here: a THUNK can be on the mutable list because
3753 * it contains pointers to young gen objects. If such a thunk
3754 * is updated, the IND_OLDGEN will be added to the mutable
3755 * list again, and we'll scavenge it twice. evacuate()
3756 * doesn't check whether the object has already been
3757 * evacuated, so we perform that check here.
3759 StgClosure *q = ((StgInd *)p)->indirectee;
3760 if (HEAP_ALLOCED(q) && Bdescr((StgPtr)q)->flags & BF_EVACUATED) {
3763 ((StgInd *)p)->indirectee = evacuate(q);
3766 #if 0 && defined(DEBUG)
3767 if (RtsFlags.DebugFlags.gc)
3768 /* Debugging code to print out the size of the thing we just
3772 StgPtr start = gen->steps[0].scan;
3773 bdescr *start_bd = gen->steps[0].scan_bd;
3775 scavenge(&gen->steps[0]);
3776 if (start_bd != gen->steps[0].scan_bd) {
3777 size += (P_)BLOCK_ROUND_UP(start) - start;
3778 start_bd = start_bd->link;
3779 while (start_bd != gen->steps[0].scan_bd) {
3780 size += BLOCK_SIZE_W;
3781 start_bd = start_bd->link;
3783 size += gen->steps[0].scan -
3784 (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
3786 size = gen->steps[0].scan - start;
3788 debugBelch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
3794 barf("scavenge_one: strange object %d", (int)(info->type));
3797 no_luck = failed_to_evac;
3798 failed_to_evac = rtsFalse;
3802 /* -----------------------------------------------------------------------------
3803 Scavenging mutable lists.
3805 We treat the mutable list of each generation > N (i.e. all the
3806 generations older than the one being collected) as roots. We also
3807 remove non-mutable objects from the mutable list at this point.
3808 -------------------------------------------------------------------------- */
3811 scavenge_mutable_list(generation *gen)
3816 bd = gen->saved_mut_list;
3819 for (; bd != NULL; bd = bd->link) {
3820 for (q = bd->start; q < bd->free; q++) {
3822 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3823 if (scavenge_one(p)) {
3824 /* didn't manage to promote everything, so put the
3825 * object back on the list.
3827 recordMutableGen((StgClosure *)p,gen);
3832 // free the old mut_list
3833 freeChain(gen->saved_mut_list);
3834 gen->saved_mut_list = NULL;
3839 scavenge_static(void)
3841 StgClosure* p = static_objects;
3842 const StgInfoTable *info;
3844 /* Always evacuate straight to the oldest generation for static
3846 evac_gen = oldest_gen->no;
3848 /* keep going until we've scavenged all the objects on the linked
3850 while (p != END_OF_STATIC_LIST) {
3852 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3855 if (info->type==RBH)
3856 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3858 // make sure the info pointer is into text space
3860 /* Take this object *off* the static_objects list,
3861 * and put it on the scavenged_static_objects list.
3863 static_objects = *STATIC_LINK(info,p);
3864 *STATIC_LINK(info,p) = scavenged_static_objects;
3865 scavenged_static_objects = p;
3867 switch (info -> type) {
3871 StgInd *ind = (StgInd *)p;
3872 ind->indirectee = evacuate(ind->indirectee);
3874 /* might fail to evacuate it, in which case we have to pop it
3875 * back on the mutable list of the oldest generation. We
3876 * leave it *on* the scavenged_static_objects list, though,
3877 * in case we visit this object again.
3879 if (failed_to_evac) {
3880 failed_to_evac = rtsFalse;
3881 recordMutableGen((StgClosure *)p,oldest_gen);
3887 scavenge_thunk_srt(info);
3891 scavenge_fun_srt(info);
3898 next = (P_)p->payload + info->layout.payload.ptrs;
3899 // evacuate the pointers
3900 for (q = (P_)p->payload; q < next; q++) {
3901 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3907 barf("scavenge_static: strange closure %d", (int)(info->type));
3910 ASSERT(failed_to_evac == rtsFalse);
3912 /* get the next static object from the list. Remember, there might
3913 * be more stuff on this list now that we've done some evacuating!
3914 * (static_objects is a global)
3920 /* -----------------------------------------------------------------------------
3921 scavenge a chunk of memory described by a bitmap
3922 -------------------------------------------------------------------------- */
3925 scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
3931 bitmap = large_bitmap->bitmap[b];
3932 for (i = 0; i < size; ) {
3933 if ((bitmap & 1) == 0) {
3934 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3938 if (i % BITS_IN(W_) == 0) {
3940 bitmap = large_bitmap->bitmap[b];
3942 bitmap = bitmap >> 1;
3947 STATIC_INLINE StgPtr
3948 scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap)
3951 if ((bitmap & 1) == 0) {
3952 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3955 bitmap = bitmap >> 1;
3961 /* -----------------------------------------------------------------------------
3962 scavenge_stack walks over a section of stack and evacuates all the
3963 objects pointed to by it. We can use the same code for walking
3964 AP_STACK_UPDs, since these are just sections of copied stack.
3965 -------------------------------------------------------------------------- */
3969 scavenge_stack(StgPtr p, StgPtr stack_end)
3971 const StgRetInfoTable* info;
3975 //IF_DEBUG(sanity, debugBelch(" scavenging stack between %p and %p", p, stack_end));
3978 * Each time around this loop, we are looking at a chunk of stack
3979 * that starts with an activation record.
3982 while (p < stack_end) {
3983 info = get_ret_itbl((StgClosure *)p);
3985 switch (info->i.type) {
3988 ((StgUpdateFrame *)p)->updatee
3989 = evacuate(((StgUpdateFrame *)p)->updatee);
3990 p += sizeofW(StgUpdateFrame);
3993 // small bitmap (< 32 entries, or 64 on a 64-bit machine)
3994 case CATCH_STM_FRAME:
3995 case CATCH_RETRY_FRAME:
3996 case ATOMICALLY_FRAME:
4001 bitmap = BITMAP_BITS(info->i.layout.bitmap);
4002 size = BITMAP_SIZE(info->i.layout.bitmap);
4003 // NOTE: the payload starts immediately after the info-ptr, we
4004 // don't have an StgHeader in the same sense as a heap closure.
4006 p = scavenge_small_bitmap(p, size, bitmap);
4010 scavenge_srt((StgClosure **)GET_SRT(info), info->i.srt_bitmap);
4018 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
4021 size = BCO_BITMAP_SIZE(bco);
4022 scavenge_large_bitmap(p, BCO_BITMAP(bco), size);
4027 // large bitmap (> 32 entries, or > 64 on a 64-bit machine)
4033 size = GET_LARGE_BITMAP(&info->i)->size;
4035 scavenge_large_bitmap(p, GET_LARGE_BITMAP(&info->i), size);
4037 // and don't forget to follow the SRT
4041 // Dynamic bitmap: the mask is stored on the stack, and
4042 // there are a number of non-pointers followed by a number
4043 // of pointers above the bitmapped area. (see StgMacros.h,
4048 dyn = ((StgRetDyn *)p)->liveness;
4050 // traverse the bitmap first
4051 bitmap = RET_DYN_LIVENESS(dyn);
4052 p = (P_)&((StgRetDyn *)p)->payload[0];
4053 size = RET_DYN_BITMAP_SIZE;
4054 p = scavenge_small_bitmap(p, size, bitmap);
4056 // skip over the non-ptr words
4057 p += RET_DYN_NONPTRS(dyn) + RET_DYN_NONPTR_REGS_SIZE;
4059 // follow the ptr words
4060 for (size = RET_DYN_PTRS(dyn); size > 0; size--) {
4061 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
4069 StgRetFun *ret_fun = (StgRetFun *)p;
4070 StgFunInfoTable *fun_info;
4072 ret_fun->fun = evacuate(ret_fun->fun);
4073 fun_info = get_fun_itbl(ret_fun->fun);
4074 p = scavenge_arg_block(fun_info, ret_fun->payload);
4079 barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->i.type));
4084 /*-----------------------------------------------------------------------------
4085 scavenge the large object list.
4087 evac_gen set by caller; similar games played with evac_gen as with
4088 scavenge() - see comment at the top of scavenge(). Most large
4089 objects are (repeatedly) mutable, so most of the time evac_gen will
4091 --------------------------------------------------------------------------- */
4094 scavenge_large(step *stp)
4099 bd = stp->new_large_objects;
4101 for (; bd != NULL; bd = stp->new_large_objects) {
4103 /* take this object *off* the large objects list and put it on
4104 * the scavenged large objects list. This is so that we can
4105 * treat new_large_objects as a stack and push new objects on
4106 * the front when evacuating.
4108 stp->new_large_objects = bd->link;
4109 dbl_link_onto(bd, &stp->scavenged_large_objects);
4111 // update the block count in this step.
4112 stp->n_scavenged_large_blocks += bd->blocks;
4115 if (scavenge_one(p)) {
4116 if (stp->gen_no > 0) {
4117 recordMutableGen((StgClosure *)p, stp->gen);
4123 /* -----------------------------------------------------------------------------
4124 Initialising the static object & mutable lists
4125 -------------------------------------------------------------------------- */
4128 zero_static_object_list(StgClosure* first_static)
4132 const StgInfoTable *info;
4134 for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
4136 link = *STATIC_LINK(info, p);
4137 *STATIC_LINK(info,p) = NULL;
4141 /* -----------------------------------------------------------------------------
4143 -------------------------------------------------------------------------- */
4150 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
4151 c = (StgIndStatic *)c->static_link)
4153 SET_INFO(c, c->saved_info);
4154 c->saved_info = NULL;
4155 // could, but not necessary: c->static_link = NULL;
4157 revertible_caf_list = NULL;
4161 markCAFs( evac_fn evac )
4165 for (c = (StgIndStatic *)caf_list; c != NULL;
4166 c = (StgIndStatic *)c->static_link)
4168 evac(&c->indirectee);
4170 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
4171 c = (StgIndStatic *)c->static_link)
4173 evac(&c->indirectee);
4177 /* -----------------------------------------------------------------------------
4178 Sanity code for CAF garbage collection.
4180 With DEBUG turned on, we manage a CAF list in addition to the SRT
4181 mechanism. After GC, we run down the CAF list and blackhole any
4182 CAFs which have been garbage collected. This means we get an error
4183 whenever the program tries to enter a garbage collected CAF.
4185 Any garbage collected CAFs are taken off the CAF list at the same
4187 -------------------------------------------------------------------------- */
4189 #if 0 && defined(DEBUG)
4196 const StgInfoTable *info;
4207 ASSERT(info->type == IND_STATIC);
4209 if (STATIC_LINK(info,p) == NULL) {
4210 IF_DEBUG(gccafs, debugBelch("CAF gc'd at 0x%04lx", (long)p));
4212 SET_INFO(p,&stg_BLACKHOLE_info);
4213 p = STATIC_LINK2(info,p);
4217 pp = &STATIC_LINK2(info,p);
4224 // debugBelch("%d CAFs live", i);
4229 /* -----------------------------------------------------------------------------
4232 Whenever a thread returns to the scheduler after possibly doing
4233 some work, we have to run down the stack and black-hole all the
4234 closures referred to by update frames.
4235 -------------------------------------------------------------------------- */
4238 threadLazyBlackHole(StgTSO *tso)
4241 StgRetInfoTable *info;
4245 stack_end = &tso->stack[tso->stack_size];
4247 frame = (StgClosure *)tso->sp;
4250 info = get_ret_itbl(frame);
4252 switch (info->i.type) {
4255 bh = ((StgUpdateFrame *)frame)->updatee;
4257 /* if the thunk is already blackholed, it means we've also
4258 * already blackholed the rest of the thunks on this stack,
4259 * so we can stop early.
4261 * The blackhole made for a CAF is a CAF_BLACKHOLE, so they
4262 * don't interfere with this optimisation.
4264 if (bh->header.info == &stg_BLACKHOLE_info) {
4268 if (bh->header.info != &stg_CAF_BLACKHOLE_info) {
4269 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4270 debugBelch("Unexpected lazy BHing required at 0x%04lx\n",(long)bh);
4274 // We pretend that bh is now dead.
4275 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4277 SET_INFO(bh,&stg_BLACKHOLE_info);
4279 // We pretend that bh has just been created.
4280 LDV_RECORD_CREATE(bh);
4283 frame = (StgClosure *) ((StgUpdateFrame *)frame + 1);
4289 // normal stack frames; do nothing except advance the pointer
4291 frame = (StgClosure *)((StgPtr)frame + stack_frame_sizeW(frame));
4297 /* -----------------------------------------------------------------------------
4300 * Code largely pinched from old RTS, then hacked to bits. We also do
4301 * lazy black holing here.
4303 * -------------------------------------------------------------------------- */
4305 struct stack_gap { StgWord gap_size; struct stack_gap *next_gap; };
4308 threadSqueezeStack(StgTSO *tso)
4311 rtsBool prev_was_update_frame;
4312 StgClosure *updatee = NULL;
4314 StgRetInfoTable *info;
4315 StgWord current_gap_size;
4316 struct stack_gap *gap;
4319 // Traverse the stack upwards, replacing adjacent update frames
4320 // with a single update frame and a "stack gap". A stack gap
4321 // contains two values: the size of the gap, and the distance
4322 // to the next gap (or the stack top).
4324 bottom = &(tso->stack[tso->stack_size]);
4328 ASSERT(frame < bottom);
4330 prev_was_update_frame = rtsFalse;
4331 current_gap_size = 0;
4332 gap = (struct stack_gap *) (tso->sp - sizeofW(StgUpdateFrame));
4334 while (frame < bottom) {
4336 info = get_ret_itbl((StgClosure *)frame);
4337 switch (info->i.type) {
4341 StgUpdateFrame *upd = (StgUpdateFrame *)frame;
4343 if (upd->updatee->header.info == &stg_BLACKHOLE_info) {
4345 // found a BLACKHOLE'd update frame; we've been here
4346 // before, in a previous GC, so just break out.
4348 // Mark the end of the gap, if we're in one.
4349 if (current_gap_size != 0) {
4350 gap = (struct stack_gap *)(frame-sizeofW(StgUpdateFrame));
4353 frame += sizeofW(StgUpdateFrame);
4354 goto done_traversing;
4357 if (prev_was_update_frame) {
4359 TICK_UPD_SQUEEZED();
4360 /* wasn't there something about update squeezing and ticky to be
4361 * sorted out? oh yes: we aren't counting each enter properly
4362 * in this case. See the log somewhere. KSW 1999-04-21
4364 * Check two things: that the two update frames don't point to
4365 * the same object, and that the updatee_bypass isn't already an
4366 * indirection. Both of these cases only happen when we're in a
4367 * block hole-style loop (and there are multiple update frames
4368 * on the stack pointing to the same closure), but they can both
4369 * screw us up if we don't check.
4371 if (upd->updatee != updatee && !closure_IND(upd->updatee)) {
4372 UPD_IND_NOLOCK(upd->updatee, updatee);
4375 // now mark this update frame as a stack gap. The gap
4376 // marker resides in the bottom-most update frame of
4377 // the series of adjacent frames, and covers all the
4378 // frames in this series.
4379 current_gap_size += sizeofW(StgUpdateFrame);
4380 ((struct stack_gap *)frame)->gap_size = current_gap_size;
4381 ((struct stack_gap *)frame)->next_gap = gap;
4383 frame += sizeofW(StgUpdateFrame);
4387 // single update frame, or the topmost update frame in a series
4389 StgClosure *bh = upd->updatee;
4391 // Do lazy black-holing
4392 if (bh->header.info != &stg_BLACKHOLE_info &&
4393 bh->header.info != &stg_CAF_BLACKHOLE_info) {
4394 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4395 debugBelch("Unexpected lazy BHing required at 0x%04lx",(long)bh);
4398 // zero out the slop so that the sanity checker can tell
4399 // where the next closure is.
4400 DEBUG_FILL_SLOP(bh);
4403 // We pretend that bh is now dead.
4404 // ToDo: is the slop filling the same as DEBUG_FILL_SLOP?
4405 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4407 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
4408 SET_INFO(bh,&stg_BLACKHOLE_info);
4410 // We pretend that bh has just been created.
4411 LDV_RECORD_CREATE(bh);
4414 prev_was_update_frame = rtsTrue;
4415 updatee = upd->updatee;
4416 frame += sizeofW(StgUpdateFrame);
4422 prev_was_update_frame = rtsFalse;
4424 // we're not in a gap... check whether this is the end of a gap
4425 // (an update frame can't be the end of a gap).
4426 if (current_gap_size != 0) {
4427 gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
4429 current_gap_size = 0;
4431 frame += stack_frame_sizeW((StgClosure *)frame);
4438 // Now we have a stack with gaps in it, and we have to walk down
4439 // shoving the stack up to fill in the gaps. A diagram might
4443 // | ********* | <- sp
4447 // | stack_gap | <- gap | chunk_size
4449 // | ......... | <- gap_end v
4455 // 'sp' points the the current top-of-stack
4456 // 'gap' points to the stack_gap structure inside the gap
4457 // ***** indicates real stack data
4458 // ..... indicates gap
4459 // <empty> indicates unused
4463 void *gap_start, *next_gap_start, *gap_end;
4466 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4467 sp = next_gap_start;
4469 while ((StgPtr)gap > tso->sp) {
4471 // we're working in *bytes* now...
4472 gap_start = next_gap_start;
4473 gap_end = (void*) ((unsigned char*)gap_start - gap->gap_size * sizeof(W_));
4475 gap = gap->next_gap;
4476 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4478 chunk_size = (unsigned char*)gap_end - (unsigned char*)next_gap_start;
4480 memmove(sp, next_gap_start, chunk_size);
4483 tso->sp = (StgPtr)sp;
4487 /* -----------------------------------------------------------------------------
4490 * We have to prepare for GC - this means doing lazy black holing
4491 * here. We also take the opportunity to do stack squeezing if it's
4493 * -------------------------------------------------------------------------- */
4495 threadPaused(StgTSO *tso)
4497 if ( RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue )
4498 threadSqueezeStack(tso); // does black holing too
4500 threadLazyBlackHole(tso);
4503 /* -----------------------------------------------------------------------------
4505 * -------------------------------------------------------------------------- */
4509 printMutableList(generation *gen)
4514 debugBelch("@@ Mutable list %p: ", gen->mut_list);
4516 for (bd = gen->mut_list; bd != NULL; bd = bd->link) {
4517 for (p = bd->start; p < bd->free; p++) {
4518 debugBelch("%p (%s), ", (void *)*p, info_type((StgClosure *)*p));