1 /* -----------------------------------------------------------------------------
3 * (c) The GHC Team 1998-2003
5 * Generational garbage collector
7 * ---------------------------------------------------------------------------*/
9 #include "PosixSource.h"
15 #include "LdvProfile.h"
19 #include "SchedAPI.h" // for ReverCAFs prototype
21 #include "BlockAlloc.h"
27 #include "ParTicky.h" // ToDo: move into Rts.h
28 #include "GCCompact.h"
30 #if defined(GRAN) || defined(PAR)
31 # include "GranSimRts.h"
32 # include "ParallelRts.h"
36 # include "ParallelDebug.h"
41 #if defined(RTS_GTK_FRONTPANEL)
42 #include "FrontPanel.h"
45 #include "RetainerProfile.h"
49 /* STATIC OBJECT LIST.
52 * We maintain a linked list of static objects that are still live.
53 * The requirements for this list are:
55 * - we need to scan the list while adding to it, in order to
56 * scavenge all the static objects (in the same way that
57 * breadth-first scavenging works for dynamic objects).
59 * - we need to be able to tell whether an object is already on
60 * the list, to break loops.
62 * Each static object has a "static link field", which we use for
63 * linking objects on to the list. We use a stack-type list, consing
64 * objects on the front as they are added (this means that the
65 * scavenge phase is depth-first, not breadth-first, but that
68 * A separate list is kept for objects that have been scavenged
69 * already - this is so that we can zero all the marks afterwards.
71 * An object is on the list if its static link field is non-zero; this
72 * means that we have to mark the end of the list with '1', not NULL.
74 * Extra notes for generational GC:
76 * Each generation has a static object list associated with it. When
77 * collecting generations up to N, we treat the static object lists
78 * from generations > N as roots.
80 * We build up a static object list while collecting generations 0..N,
81 * which is then appended to the static object list of generation N+1.
83 static StgClosure* static_objects; // live static objects
84 StgClosure* scavenged_static_objects; // static objects scavenged so far
86 /* N is the oldest generation being collected, where the generations
87 * are numbered starting at 0. A major GC (indicated by the major_gc
88 * flag) is when we're collecting all generations. We only attempt to
89 * deal with static objects and GC CAFs when doing a major GC.
92 static rtsBool major_gc;
94 /* Youngest generation that objects should be evacuated to in
95 * evacuate(). (Logically an argument to evacuate, but it's static
96 * a lot of the time so we optimise it into a global variable).
102 StgWeak *old_weak_ptr_list; // also pending finaliser list
104 /* Which stage of processing various kinds of weak pointer are we at?
105 * (see traverse_weak_ptr_list() below for discussion).
107 typedef enum { WeakPtrs, WeakThreads, WeakDone } WeakStage;
108 static WeakStage weak_stage;
110 /* List of all threads during GC
112 static StgTSO *old_all_threads;
113 StgTSO *resurrected_threads;
115 /* Flag indicating failure to evacuate an object to the desired
118 static rtsBool failed_to_evac;
120 /* Old to-space (used for two-space collector only)
122 static bdescr *old_to_blocks;
124 /* Data used for allocation area sizing.
126 static lnat new_blocks; // blocks allocated during this GC
127 static lnat g0s0_pcnt_kept = 30; // percentage of g0s0 live at last minor GC
129 /* Used to avoid long recursion due to selector thunks
131 static lnat thunk_selector_depth = 0;
132 #define MAX_THUNK_SELECTOR_DEPTH 8
134 /* -----------------------------------------------------------------------------
135 Static function declarations
136 -------------------------------------------------------------------------- */
138 static bdescr * gc_alloc_block ( step *stp );
139 static void mark_root ( StgClosure **root );
141 // Use a register argument for evacuate, if available.
143 #define REGPARM1 __attribute__((regparm(1)))
148 REGPARM1 static StgClosure * evacuate (StgClosure *q);
150 static void zero_static_object_list ( StgClosure* first_static );
151 static void zero_mutable_list ( StgMutClosure *first );
153 static rtsBool traverse_weak_ptr_list ( void );
154 static void mark_weak_ptr_list ( StgWeak **list );
156 static StgClosure * eval_thunk_selector ( nat field, StgSelector * p );
159 static void scavenge ( step * );
160 static void scavenge_mark_stack ( void );
161 static void scavenge_stack ( StgPtr p, StgPtr stack_end );
162 static rtsBool scavenge_one ( StgPtr p );
163 static void scavenge_large ( step * );
164 static void scavenge_static ( void );
165 static void scavenge_mutable_list ( generation *g );
166 static void scavenge_mut_once_list ( generation *g );
168 static void scavenge_large_bitmap ( StgPtr p,
169 StgLargeBitmap *large_bitmap,
172 #if 0 && defined(DEBUG)
173 static void gcCAFs ( void );
176 /* -----------------------------------------------------------------------------
177 inline functions etc. for dealing with the mark bitmap & stack.
178 -------------------------------------------------------------------------- */
180 #define MARK_STACK_BLOCKS 4
182 static bdescr *mark_stack_bdescr;
183 static StgPtr *mark_stack;
184 static StgPtr *mark_sp;
185 static StgPtr *mark_splim;
187 // Flag and pointers used for falling back to a linear scan when the
188 // mark stack overflows.
189 static rtsBool mark_stack_overflowed;
190 static bdescr *oldgen_scan_bd;
191 static StgPtr oldgen_scan;
193 STATIC_INLINE rtsBool
194 mark_stack_empty(void)
196 return mark_sp == mark_stack;
199 STATIC_INLINE rtsBool
200 mark_stack_full(void)
202 return mark_sp >= mark_splim;
206 reset_mark_stack(void)
208 mark_sp = mark_stack;
212 push_mark_stack(StgPtr p)
223 /* -----------------------------------------------------------------------------
224 Allocate a new to-space block in the given step.
225 -------------------------------------------------------------------------- */
228 gc_alloc_block(step *stp)
230 bdescr *bd = allocBlock();
231 bd->gen_no = stp->gen_no;
235 // blocks in to-space in generations up to and including N
236 // get the BF_EVACUATED flag.
237 if (stp->gen_no <= N) {
238 bd->flags = BF_EVACUATED;
243 // Start a new to-space block, chain it on after the previous one.
244 if (stp->hp_bd == NULL) {
247 stp->hp_bd->free = stp->hp;
248 stp->hp_bd->link = bd;
253 stp->hpLim = stp->hp + BLOCK_SIZE_W;
261 /* -----------------------------------------------------------------------------
264 Rough outline of the algorithm: for garbage collecting generation N
265 (and all younger generations):
267 - follow all pointers in the root set. the root set includes all
268 mutable objects in all generations (mutable_list and mut_once_list).
270 - for each pointer, evacuate the object it points to into either
272 + to-space of the step given by step->to, which is the next
273 highest step in this generation or the first step in the next
274 generation if this is the last step.
276 + to-space of generations[evac_gen]->steps[0], if evac_gen != 0.
277 When we evacuate an object we attempt to evacuate
278 everything it points to into the same generation - this is
279 achieved by setting evac_gen to the desired generation. If
280 we can't do this, then an entry in the mut_once list has to
281 be made for the cross-generation pointer.
283 + if the object is already in a generation > N, then leave
286 - repeatedly scavenge to-space from each step in each generation
287 being collected until no more objects can be evacuated.
289 - free from-space in each step, and set from-space = to-space.
291 Locks held: sched_mutex
293 -------------------------------------------------------------------------- */
296 GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc )
300 lnat live, allocated, collected = 0, copied = 0;
301 lnat oldgen_saved_blocks = 0;
305 CostCentreStack *prev_CCS;
308 #if defined(DEBUG) && defined(GRAN)
309 IF_DEBUG(gc, debugBelch("@@ Starting garbage collection at %ld (%lx)\n",
313 #if defined(RTS_USER_SIGNALS)
318 // tell the stats department that we've started a GC
321 // Init stats and print par specific (timing) info
322 PAR_TICKY_PAR_START();
324 // attribute any costs to CCS_GC
330 /* Approximate how much we allocated.
331 * Todo: only when generating stats?
333 allocated = calcAllocated();
335 /* Figure out which generation to collect
337 if (force_major_gc) {
338 N = RtsFlags.GcFlags.generations - 1;
342 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
343 if (generations[g].steps[0].n_blocks +
344 generations[g].steps[0].n_large_blocks
345 >= generations[g].max_blocks) {
349 major_gc = (N == RtsFlags.GcFlags.generations-1);
352 #ifdef RTS_GTK_FRONTPANEL
353 if (RtsFlags.GcFlags.frontpanel) {
354 updateFrontPanelBeforeGC(N);
358 // check stack sanity *before* GC (ToDo: check all threads)
360 // ToDo!: check sanity IF_DEBUG(sanity, checkTSOsSanity());
362 IF_DEBUG(sanity, checkFreeListSanity());
364 /* Initialise the static object lists
366 static_objects = END_OF_STATIC_LIST;
367 scavenged_static_objects = END_OF_STATIC_LIST;
369 /* zero the mutable list for the oldest generation (see comment by
370 * zero_mutable_list below).
373 zero_mutable_list(generations[RtsFlags.GcFlags.generations-1].mut_once_list);
376 /* Save the old to-space if we're doing a two-space collection
378 if (RtsFlags.GcFlags.generations == 1) {
379 old_to_blocks = g0s0->to_blocks;
380 g0s0->to_blocks = NULL;
381 g0s0->n_to_blocks = 0;
384 /* Keep a count of how many new blocks we allocated during this GC
385 * (used for resizing the allocation area, later).
389 // Initialise to-space in all the generations/steps that we're
392 for (g = 0; g <= N; g++) {
393 generations[g].mut_once_list = END_MUT_LIST;
394 generations[g].mut_list = END_MUT_LIST;
396 for (s = 0; s < generations[g].n_steps; s++) {
398 // generation 0, step 0 doesn't need to-space
399 if (g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1) {
403 stp = &generations[g].steps[s];
404 ASSERT(stp->gen_no == g);
406 // start a new to-space for this step.
409 stp->to_blocks = NULL;
411 // allocate the first to-space block; extra blocks will be
412 // chained on as necessary.
413 bd = gc_alloc_block(stp);
415 stp->scan = bd->start;
418 // initialise the large object queues.
419 stp->new_large_objects = NULL;
420 stp->scavenged_large_objects = NULL;
421 stp->n_scavenged_large_blocks = 0;
423 // mark the large objects as not evacuated yet
424 for (bd = stp->large_objects; bd; bd = bd->link) {
425 bd->flags &= ~BF_EVACUATED;
428 // for a compacted step, we need to allocate the bitmap
429 if (stp->is_compacted) {
430 nat bitmap_size; // in bytes
431 bdescr *bitmap_bdescr;
434 bitmap_size = stp->n_blocks * BLOCK_SIZE / (sizeof(W_)*BITS_PER_BYTE);
436 if (bitmap_size > 0) {
437 bitmap_bdescr = allocGroup((nat)BLOCK_ROUND_UP(bitmap_size)
439 stp->bitmap = bitmap_bdescr;
440 bitmap = bitmap_bdescr->start;
442 IF_DEBUG(gc, debugBelch("bitmap_size: %d, bitmap: %p",
443 bitmap_size, bitmap););
445 // don't forget to fill it with zeros!
446 memset(bitmap, 0, bitmap_size);
448 // For each block in this step, point to its bitmap from the
450 for (bd=stp->blocks; bd != NULL; bd = bd->link) {
451 bd->u.bitmap = bitmap;
452 bitmap += BLOCK_SIZE_W / (sizeof(W_)*BITS_PER_BYTE);
454 // Also at this point we set the BF_COMPACTED flag
455 // for this block. The invariant is that
456 // BF_COMPACTED is always unset, except during GC
457 // when it is set on those blocks which will be
459 bd->flags |= BF_COMPACTED;
466 /* make sure the older generations have at least one block to
467 * allocate into (this makes things easier for copy(), see below).
469 for (g = N+1; g < RtsFlags.GcFlags.generations; g++) {
470 for (s = 0; s < generations[g].n_steps; s++) {
471 stp = &generations[g].steps[s];
472 if (stp->hp_bd == NULL) {
473 ASSERT(stp->blocks == NULL);
474 bd = gc_alloc_block(stp);
478 /* Set the scan pointer for older generations: remember we
479 * still have to scavenge objects that have been promoted. */
481 stp->scan_bd = stp->hp_bd;
482 stp->to_blocks = NULL;
483 stp->n_to_blocks = 0;
484 stp->new_large_objects = NULL;
485 stp->scavenged_large_objects = NULL;
486 stp->n_scavenged_large_blocks = 0;
490 /* Allocate a mark stack if we're doing a major collection.
493 mark_stack_bdescr = allocGroup(MARK_STACK_BLOCKS);
494 mark_stack = (StgPtr *)mark_stack_bdescr->start;
495 mark_sp = mark_stack;
496 mark_splim = mark_stack + (MARK_STACK_BLOCKS * BLOCK_SIZE_W);
498 mark_stack_bdescr = NULL;
501 /* -----------------------------------------------------------------------
502 * follow all the roots that we know about:
503 * - mutable lists from each generation > N
504 * we want to *scavenge* these roots, not evacuate them: they're not
505 * going to move in this GC.
506 * Also: do them in reverse generation order. This is because we
507 * often want to promote objects that are pointed to by older
508 * generations early, so we don't have to repeatedly copy them.
509 * Doing the generations in reverse order ensures that we don't end
510 * up in the situation where we want to evac an object to gen 3 and
511 * it has already been evaced to gen 2.
515 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
516 generations[g].saved_mut_list = generations[g].mut_list;
517 generations[g].mut_list = END_MUT_LIST;
520 // Do the mut-once lists first
521 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
522 IF_PAR_DEBUG(verbose,
523 printMutOnceList(&generations[g]));
524 scavenge_mut_once_list(&generations[g]);
526 for (st = generations[g].n_steps-1; st >= 0; st--) {
527 scavenge(&generations[g].steps[st]);
531 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
532 IF_PAR_DEBUG(verbose,
533 printMutableList(&generations[g]));
534 scavenge_mutable_list(&generations[g]);
536 for (st = generations[g].n_steps-1; st >= 0; st--) {
537 scavenge(&generations[g].steps[st]);
542 /* follow roots from the CAF list (used by GHCi)
547 /* follow all the roots that the application knows about.
550 get_roots(mark_root);
553 /* And don't forget to mark the TSO if we got here direct from
555 /* Not needed in a seq version?
557 CurrentTSO = (StgTSO *)MarkRoot((StgClosure *)CurrentTSO);
561 // Mark the entries in the GALA table of the parallel system
562 markLocalGAs(major_gc);
563 // Mark all entries on the list of pending fetches
564 markPendingFetches(major_gc);
567 /* Mark the weak pointer list, and prepare to detect dead weak
570 mark_weak_ptr_list(&weak_ptr_list);
571 old_weak_ptr_list = weak_ptr_list;
572 weak_ptr_list = NULL;
573 weak_stage = WeakPtrs;
575 /* The all_threads list is like the weak_ptr_list.
576 * See traverse_weak_ptr_list() for the details.
578 old_all_threads = all_threads;
579 all_threads = END_TSO_QUEUE;
580 resurrected_threads = END_TSO_QUEUE;
582 /* Mark the stable pointer table.
584 markStablePtrTable(mark_root);
586 /* -------------------------------------------------------------------------
587 * Repeatedly scavenge all the areas we know about until there's no
588 * more scavenging to be done.
595 // scavenge static objects
596 if (major_gc && static_objects != END_OF_STATIC_LIST) {
597 IF_DEBUG(sanity, checkStaticObjects(static_objects));
601 /* When scavenging the older generations: Objects may have been
602 * evacuated from generations <= N into older generations, and we
603 * need to scavenge these objects. We're going to try to ensure that
604 * any evacuations that occur move the objects into at least the
605 * same generation as the object being scavenged, otherwise we
606 * have to create new entries on the mutable list for the older
610 // scavenge each step in generations 0..maxgen
616 // scavenge objects in compacted generation
617 if (mark_stack_overflowed || oldgen_scan_bd != NULL ||
618 (mark_stack_bdescr != NULL && !mark_stack_empty())) {
619 scavenge_mark_stack();
623 for (gen = RtsFlags.GcFlags.generations; --gen >= 0; ) {
624 for (st = generations[gen].n_steps; --st >= 0; ) {
625 if (gen == 0 && st == 0 && RtsFlags.GcFlags.generations > 1) {
628 stp = &generations[gen].steps[st];
630 if (stp->hp_bd != stp->scan_bd || stp->scan < stp->hp) {
635 if (stp->new_large_objects != NULL) {
644 if (flag) { goto loop; }
646 // must be last... invariant is that everything is fully
647 // scavenged at this point.
648 if (traverse_weak_ptr_list()) { // returns rtsTrue if evaced something
653 /* Update the pointers from the "main thread" list - these are
654 * treated as weak pointers because we want to allow a main thread
655 * to get a BlockedOnDeadMVar exception in the same way as any other
656 * thread. Note that the threads should all have been retained by
657 * GC by virtue of being on the all_threads list, we're just
658 * updating pointers here.
663 for (m = main_threads; m != NULL; m = m->link) {
664 tso = (StgTSO *) isAlive((StgClosure *)m->tso);
666 barf("main thread has been GC'd");
673 // Reconstruct the Global Address tables used in GUM
674 rebuildGAtables(major_gc);
675 IF_DEBUG(sanity, checkLAGAtable(rtsTrue/*check closures, too*/));
678 // Now see which stable names are still alive.
681 // Tidy the end of the to-space chains
682 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
683 for (s = 0; s < generations[g].n_steps; s++) {
684 stp = &generations[g].steps[s];
685 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
686 ASSERT(Bdescr(stp->hp) == stp->hp_bd);
687 stp->hp_bd->free = stp->hp;
693 // We call processHeapClosureForDead() on every closure destroyed during
694 // the current garbage collection, so we invoke LdvCensusForDead().
695 if (RtsFlags.ProfFlags.doHeapProfile == HEAP_BY_LDV
696 || RtsFlags.ProfFlags.bioSelector != NULL)
700 // NO MORE EVACUATION AFTER THIS POINT!
701 // Finally: compaction of the oldest generation.
702 if (major_gc && oldest_gen->steps[0].is_compacted) {
703 // save number of blocks for stats
704 oldgen_saved_blocks = oldest_gen->steps[0].n_blocks;
708 IF_DEBUG(sanity, checkGlobalTSOList(rtsFalse));
710 /* run through all the generations/steps and tidy up
712 copied = new_blocks * BLOCK_SIZE_W;
713 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
716 generations[g].collections++; // for stats
719 for (s = 0; s < generations[g].n_steps; s++) {
721 stp = &generations[g].steps[s];
723 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
724 // stats information: how much we copied
726 copied -= stp->hp_bd->start + BLOCK_SIZE_W -
731 // for generations we collected...
734 // rough calculation of garbage collected, for stats output
735 if (stp->is_compacted) {
736 collected += (oldgen_saved_blocks - stp->n_blocks) * BLOCK_SIZE_W;
738 collected += stp->n_blocks * BLOCK_SIZE_W;
741 /* free old memory and shift to-space into from-space for all
742 * the collected steps (except the allocation area). These
743 * freed blocks will probaby be quickly recycled.
745 if (!(g == 0 && s == 0)) {
746 if (stp->is_compacted) {
747 // for a compacted step, just shift the new to-space
748 // onto the front of the now-compacted existing blocks.
749 for (bd = stp->to_blocks; bd != NULL; bd = bd->link) {
750 bd->flags &= ~BF_EVACUATED; // now from-space
752 // tack the new blocks on the end of the existing blocks
753 if (stp->blocks == NULL) {
754 stp->blocks = stp->to_blocks;
756 for (bd = stp->blocks; bd != NULL; bd = next) {
759 bd->link = stp->to_blocks;
761 // NB. this step might not be compacted next
762 // time, so reset the BF_COMPACTED flags.
763 // They are set before GC if we're going to
764 // compact. (search for BF_COMPACTED above).
765 bd->flags &= ~BF_COMPACTED;
768 // add the new blocks to the block tally
769 stp->n_blocks += stp->n_to_blocks;
771 freeChain(stp->blocks);
772 stp->blocks = stp->to_blocks;
773 stp->n_blocks = stp->n_to_blocks;
774 for (bd = stp->blocks; bd != NULL; bd = bd->link) {
775 bd->flags &= ~BF_EVACUATED; // now from-space
778 stp->to_blocks = NULL;
779 stp->n_to_blocks = 0;
782 /* LARGE OBJECTS. The current live large objects are chained on
783 * scavenged_large, having been moved during garbage
784 * collection from large_objects. Any objects left on
785 * large_objects list are therefore dead, so we free them here.
787 for (bd = stp->large_objects; bd != NULL; bd = next) {
793 // update the count of blocks used by large objects
794 for (bd = stp->scavenged_large_objects; bd != NULL; bd = bd->link) {
795 bd->flags &= ~BF_EVACUATED;
797 stp->large_objects = stp->scavenged_large_objects;
798 stp->n_large_blocks = stp->n_scavenged_large_blocks;
801 // for older generations...
803 /* For older generations, we need to append the
804 * scavenged_large_object list (i.e. large objects that have been
805 * promoted during this GC) to the large_object list for that step.
807 for (bd = stp->scavenged_large_objects; bd; bd = next) {
809 bd->flags &= ~BF_EVACUATED;
810 dbl_link_onto(bd, &stp->large_objects);
813 // add the new blocks we promoted during this GC
814 stp->n_blocks += stp->n_to_blocks;
815 stp->n_to_blocks = 0;
816 stp->n_large_blocks += stp->n_scavenged_large_blocks;
821 /* Reset the sizes of the older generations when we do a major
824 * CURRENT STRATEGY: make all generations except zero the same size.
825 * We have to stay within the maximum heap size, and leave a certain
826 * percentage of the maximum heap size available to allocate into.
828 if (major_gc && RtsFlags.GcFlags.generations > 1) {
829 nat live, size, min_alloc;
830 nat max = RtsFlags.GcFlags.maxHeapSize;
831 nat gens = RtsFlags.GcFlags.generations;
833 // live in the oldest generations
834 live = oldest_gen->steps[0].n_blocks +
835 oldest_gen->steps[0].n_large_blocks;
837 // default max size for all generations except zero
838 size = stg_max(live * RtsFlags.GcFlags.oldGenFactor,
839 RtsFlags.GcFlags.minOldGenSize);
841 // minimum size for generation zero
842 min_alloc = stg_max((RtsFlags.GcFlags.pcFreeHeap * max) / 200,
843 RtsFlags.GcFlags.minAllocAreaSize);
845 // Auto-enable compaction when the residency reaches a
846 // certain percentage of the maximum heap size (default: 30%).
847 if (RtsFlags.GcFlags.generations > 1 &&
848 (RtsFlags.GcFlags.compact ||
850 oldest_gen->steps[0].n_blocks >
851 (RtsFlags.GcFlags.compactThreshold * max) / 100))) {
852 oldest_gen->steps[0].is_compacted = 1;
853 // debugBelch("compaction: on\n", live);
855 oldest_gen->steps[0].is_compacted = 0;
856 // debugBelch("compaction: off\n", live);
859 // if we're going to go over the maximum heap size, reduce the
860 // size of the generations accordingly. The calculation is
861 // different if compaction is turned on, because we don't need
862 // to double the space required to collect the old generation.
865 // this test is necessary to ensure that the calculations
866 // below don't have any negative results - we're working
867 // with unsigned values here.
868 if (max < min_alloc) {
872 if (oldest_gen->steps[0].is_compacted) {
873 if ( (size + (size - 1) * (gens - 2) * 2) + min_alloc > max ) {
874 size = (max - min_alloc) / ((gens - 1) * 2 - 1);
877 if ( (size * (gens - 1) * 2) + min_alloc > max ) {
878 size = (max - min_alloc) / ((gens - 1) * 2);
888 debugBelch("live: %d, min_alloc: %d, size : %d, max = %d\n", live,
889 min_alloc, size, max);
892 for (g = 0; g < gens; g++) {
893 generations[g].max_blocks = size;
897 // Guess the amount of live data for stats.
900 /* Free the small objects allocated via allocate(), since this will
901 * all have been copied into G0S1 now.
903 if (small_alloc_list != NULL) {
904 freeChain(small_alloc_list);
906 small_alloc_list = NULL;
910 alloc_blocks_lim = RtsFlags.GcFlags.minAllocAreaSize;
912 // Start a new pinned_object_block
913 pinned_object_block = NULL;
915 /* Free the mark stack.
917 if (mark_stack_bdescr != NULL) {
918 freeGroup(mark_stack_bdescr);
923 for (g = 0; g <= N; g++) {
924 for (s = 0; s < generations[g].n_steps; s++) {
925 stp = &generations[g].steps[s];
926 if (stp->is_compacted && stp->bitmap != NULL) {
927 freeGroup(stp->bitmap);
932 /* Two-space collector:
933 * Free the old to-space, and estimate the amount of live data.
935 if (RtsFlags.GcFlags.generations == 1) {
938 if (old_to_blocks != NULL) {
939 freeChain(old_to_blocks);
941 for (bd = g0s0->to_blocks; bd != NULL; bd = bd->link) {
942 bd->flags = 0; // now from-space
945 /* For a two-space collector, we need to resize the nursery. */
947 /* set up a new nursery. Allocate a nursery size based on a
948 * function of the amount of live data (by default a factor of 2)
949 * Use the blocks from the old nursery if possible, freeing up any
952 * If we get near the maximum heap size, then adjust our nursery
953 * size accordingly. If the nursery is the same size as the live
954 * data (L), then we need 3L bytes. We can reduce the size of the
955 * nursery to bring the required memory down near 2L bytes.
957 * A normal 2-space collector would need 4L bytes to give the same
958 * performance we get from 3L bytes, reducing to the same
959 * performance at 2L bytes.
961 blocks = g0s0->n_to_blocks;
963 if ( RtsFlags.GcFlags.maxHeapSize != 0 &&
964 blocks * RtsFlags.GcFlags.oldGenFactor * 2 >
965 RtsFlags.GcFlags.maxHeapSize ) {
966 long adjusted_blocks; // signed on purpose
969 adjusted_blocks = (RtsFlags.GcFlags.maxHeapSize - 2 * blocks);
970 IF_DEBUG(gc, debugBelch("@@ Near maximum heap size of 0x%x blocks, blocks = %d, adjusted to %ld", RtsFlags.GcFlags.maxHeapSize, blocks, adjusted_blocks));
971 pc_free = adjusted_blocks * 100 / RtsFlags.GcFlags.maxHeapSize;
972 if (pc_free < RtsFlags.GcFlags.pcFreeHeap) /* might even be < 0 */ {
975 blocks = adjusted_blocks;
978 blocks *= RtsFlags.GcFlags.oldGenFactor;
979 if (blocks < RtsFlags.GcFlags.minAllocAreaSize) {
980 blocks = RtsFlags.GcFlags.minAllocAreaSize;
983 resizeNursery(blocks);
986 /* Generational collector:
987 * If the user has given us a suggested heap size, adjust our
988 * allocation area to make best use of the memory available.
991 if (RtsFlags.GcFlags.heapSizeSuggestion) {
993 nat needed = calcNeeded(); // approx blocks needed at next GC
995 /* Guess how much will be live in generation 0 step 0 next time.
996 * A good approximation is obtained by finding the
997 * percentage of g0s0 that was live at the last minor GC.
1000 g0s0_pcnt_kept = (new_blocks * 100) / g0s0->n_blocks;
1003 /* Estimate a size for the allocation area based on the
1004 * information available. We might end up going slightly under
1005 * or over the suggested heap size, but we should be pretty
1008 * Formula: suggested - needed
1009 * ----------------------------
1010 * 1 + g0s0_pcnt_kept/100
1012 * where 'needed' is the amount of memory needed at the next
1013 * collection for collecting all steps except g0s0.
1016 (((long)RtsFlags.GcFlags.heapSizeSuggestion - (long)needed) * 100) /
1017 (100 + (long)g0s0_pcnt_kept);
1019 if (blocks < (long)RtsFlags.GcFlags.minAllocAreaSize) {
1020 blocks = RtsFlags.GcFlags.minAllocAreaSize;
1023 resizeNursery((nat)blocks);
1026 // we might have added extra large blocks to the nursery, so
1027 // resize back to minAllocAreaSize again.
1028 resizeNursery(RtsFlags.GcFlags.minAllocAreaSize);
1032 // mark the garbage collected CAFs as dead
1033 #if 0 && defined(DEBUG) // doesn't work at the moment
1034 if (major_gc) { gcCAFs(); }
1038 // resetStaticObjectForRetainerProfiling() must be called before
1040 resetStaticObjectForRetainerProfiling();
1043 // zero the scavenged static object list
1045 zero_static_object_list(scavenged_static_objects);
1048 // Reset the nursery
1051 RELEASE_LOCK(&sched_mutex);
1053 // start any pending finalizers
1054 scheduleFinalizers(old_weak_ptr_list);
1056 // send exceptions to any threads which were about to die
1057 resurrectThreads(resurrected_threads);
1059 ACQUIRE_LOCK(&sched_mutex);
1061 // Update the stable pointer hash table.
1062 updateStablePtrTable(major_gc);
1064 // check sanity after GC
1065 IF_DEBUG(sanity, checkSanity());
1067 // extra GC trace info
1068 IF_DEBUG(gc, statDescribeGens());
1071 // symbol-table based profiling
1072 /* heapCensus(to_blocks); */ /* ToDo */
1075 // restore enclosing cost centre
1080 // check for memory leaks if sanity checking is on
1081 IF_DEBUG(sanity, memInventory());
1083 #ifdef RTS_GTK_FRONTPANEL
1084 if (RtsFlags.GcFlags.frontpanel) {
1085 updateFrontPanelAfterGC( N, live );
1089 // ok, GC over: tell the stats department what happened.
1090 stat_endGC(allocated, collected, live, copied, N);
1092 #if defined(RTS_USER_SIGNALS)
1093 // unblock signals again
1094 unblockUserSignals();
1101 /* -----------------------------------------------------------------------------
1104 traverse_weak_ptr_list is called possibly many times during garbage
1105 collection. It returns a flag indicating whether it did any work
1106 (i.e. called evacuate on any live pointers).
1108 Invariant: traverse_weak_ptr_list is called when the heap is in an
1109 idempotent state. That means that there are no pending
1110 evacuate/scavenge operations. This invariant helps the weak
1111 pointer code decide which weak pointers are dead - if there are no
1112 new live weak pointers, then all the currently unreachable ones are
1115 For generational GC: we just don't try to finalize weak pointers in
1116 older generations than the one we're collecting. This could
1117 probably be optimised by keeping per-generation lists of weak
1118 pointers, but for a few weak pointers this scheme will work.
1120 There are three distinct stages to processing weak pointers:
1122 - weak_stage == WeakPtrs
1124 We process all the weak pointers whos keys are alive (evacuate
1125 their values and finalizers), and repeat until we can find no new
1126 live keys. If no live keys are found in this pass, then we
1127 evacuate the finalizers of all the dead weak pointers in order to
1130 - weak_stage == WeakThreads
1132 Now, we discover which *threads* are still alive. Pointers to
1133 threads from the all_threads and main thread lists are the
1134 weakest of all: a pointers from the finalizer of a dead weak
1135 pointer can keep a thread alive. Any threads found to be unreachable
1136 are evacuated and placed on the resurrected_threads list so we
1137 can send them a signal later.
1139 - weak_stage == WeakDone
1141 No more evacuation is done.
1143 -------------------------------------------------------------------------- */
1146 traverse_weak_ptr_list(void)
1148 StgWeak *w, **last_w, *next_w;
1150 rtsBool flag = rtsFalse;
1152 switch (weak_stage) {
1158 /* doesn't matter where we evacuate values/finalizers to, since
1159 * these pointers are treated as roots (iff the keys are alive).
1163 last_w = &old_weak_ptr_list;
1164 for (w = old_weak_ptr_list; w != NULL; w = next_w) {
1166 /* There might be a DEAD_WEAK on the list if finalizeWeak# was
1167 * called on a live weak pointer object. Just remove it.
1169 if (w->header.info == &stg_DEAD_WEAK_info) {
1170 next_w = ((StgDeadWeak *)w)->link;
1175 switch (get_itbl(w)->type) {
1178 next_w = (StgWeak *)((StgEvacuated *)w)->evacuee;
1183 /* Now, check whether the key is reachable.
1185 new = isAlive(w->key);
1188 // evacuate the value and finalizer
1189 w->value = evacuate(w->value);
1190 w->finalizer = evacuate(w->finalizer);
1191 // remove this weak ptr from the old_weak_ptr list
1193 // and put it on the new weak ptr list
1195 w->link = weak_ptr_list;
1198 IF_DEBUG(weak, debugBelch("Weak pointer still alive at %p -> %p",
1203 last_w = &(w->link);
1209 barf("traverse_weak_ptr_list: not WEAK");
1213 /* If we didn't make any changes, then we can go round and kill all
1214 * the dead weak pointers. The old_weak_ptr list is used as a list
1215 * of pending finalizers later on.
1217 if (flag == rtsFalse) {
1218 for (w = old_weak_ptr_list; w; w = w->link) {
1219 w->finalizer = evacuate(w->finalizer);
1222 // Next, move to the WeakThreads stage after fully
1223 // scavenging the finalizers we've just evacuated.
1224 weak_stage = WeakThreads;
1230 /* Now deal with the all_threads list, which behaves somewhat like
1231 * the weak ptr list. If we discover any threads that are about to
1232 * become garbage, we wake them up and administer an exception.
1235 StgTSO *t, *tmp, *next, **prev;
1237 prev = &old_all_threads;
1238 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1240 (StgClosure *)tmp = isAlive((StgClosure *)t);
1246 ASSERT(get_itbl(t)->type == TSO);
1247 switch (t->what_next) {
1248 case ThreadRelocated:
1253 case ThreadComplete:
1254 // finshed or died. The thread might still be alive, but we
1255 // don't keep it on the all_threads list. Don't forget to
1256 // stub out its global_link field.
1257 next = t->global_link;
1258 t->global_link = END_TSO_QUEUE;
1266 // not alive (yet): leave this thread on the
1267 // old_all_threads list.
1268 prev = &(t->global_link);
1269 next = t->global_link;
1272 // alive: move this thread onto the all_threads list.
1273 next = t->global_link;
1274 t->global_link = all_threads;
1281 /* And resurrect any threads which were about to become garbage.
1284 StgTSO *t, *tmp, *next;
1285 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1286 next = t->global_link;
1287 (StgClosure *)tmp = evacuate((StgClosure *)t);
1288 tmp->global_link = resurrected_threads;
1289 resurrected_threads = tmp;
1293 weak_stage = WeakDone; // *now* we're done,
1294 return rtsTrue; // but one more round of scavenging, please
1297 barf("traverse_weak_ptr_list");
1303 /* -----------------------------------------------------------------------------
1304 After GC, the live weak pointer list may have forwarding pointers
1305 on it, because a weak pointer object was evacuated after being
1306 moved to the live weak pointer list. We remove those forwarding
1309 Also, we don't consider weak pointer objects to be reachable, but
1310 we must nevertheless consider them to be "live" and retain them.
1311 Therefore any weak pointer objects which haven't as yet been
1312 evacuated need to be evacuated now.
1313 -------------------------------------------------------------------------- */
1317 mark_weak_ptr_list ( StgWeak **list )
1319 StgWeak *w, **last_w;
1322 for (w = *list; w; w = w->link) {
1323 // w might be WEAK, EVACUATED, or DEAD_WEAK (actually CON_STATIC) here
1324 ASSERT(w->header.info == &stg_DEAD_WEAK_info
1325 || get_itbl(w)->type == WEAK || get_itbl(w)->type == EVACUATED);
1326 (StgClosure *)w = evacuate((StgClosure *)w);
1328 last_w = &(w->link);
1332 /* -----------------------------------------------------------------------------
1333 isAlive determines whether the given closure is still alive (after
1334 a garbage collection) or not. It returns the new address of the
1335 closure if it is alive, or NULL otherwise.
1337 NOTE: Use it before compaction only!
1338 -------------------------------------------------------------------------- */
1342 isAlive(StgClosure *p)
1344 const StgInfoTable *info;
1349 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
1352 // ignore static closures
1354 // ToDo: for static closures, check the static link field.
1355 // Problem here is that we sometimes don't set the link field, eg.
1356 // for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
1358 if (!HEAP_ALLOCED(p)) {
1362 // ignore closures in generations that we're not collecting.
1364 if (bd->gen_no > N) {
1368 // if it's a pointer into to-space, then we're done
1369 if (bd->flags & BF_EVACUATED) {
1373 // large objects use the evacuated flag
1374 if (bd->flags & BF_LARGE) {
1378 // check the mark bit for compacted steps
1379 if ((bd->flags & BF_COMPACTED) && is_marked((P_)p,bd)) {
1383 switch (info->type) {
1388 case IND_OLDGEN: // rely on compatible layout with StgInd
1389 case IND_OLDGEN_PERM:
1390 // follow indirections
1391 p = ((StgInd *)p)->indirectee;
1396 return ((StgEvacuated *)p)->evacuee;
1399 if (((StgTSO *)p)->what_next == ThreadRelocated) {
1400 p = (StgClosure *)((StgTSO *)p)->link;
1413 mark_root(StgClosure **root)
1415 *root = evacuate(*root);
1419 upd_evacuee(StgClosure *p, StgClosure *dest)
1421 // Source object must be in from-space:
1422 ASSERT((Bdescr((P_)p)->flags & BF_EVACUATED) == 0);
1423 // not true: (ToDo: perhaps it should be)
1424 // ASSERT(Bdescr((P_)dest)->flags & BF_EVACUATED);
1425 SET_INFO(p, &stg_EVACUATED_info);
1426 ((StgEvacuated *)p)->evacuee = dest;
1430 STATIC_INLINE StgClosure *
1431 copy(StgClosure *src, nat size, step *stp)
1436 nat size_org = size;
1439 TICK_GC_WORDS_COPIED(size);
1440 /* Find out where we're going, using the handy "to" pointer in
1441 * the step of the source object. If it turns out we need to
1442 * evacuate to an older generation, adjust it here (see comment
1445 if (stp->gen_no < evac_gen) {
1446 #ifdef NO_EAGER_PROMOTION
1447 failed_to_evac = rtsTrue;
1449 stp = &generations[evac_gen].steps[0];
1453 /* chain a new block onto the to-space for the destination step if
1456 if (stp->hp + size >= stp->hpLim) {
1457 gc_alloc_block(stp);
1460 for(to = stp->hp, from = (P_)src; size>0; --size) {
1466 upd_evacuee(src,(StgClosure *)dest);
1468 // We store the size of the just evacuated object in the LDV word so that
1469 // the profiler can guess the position of the next object later.
1470 SET_EVACUAEE_FOR_LDV(src, size_org);
1472 return (StgClosure *)dest;
1475 /* Special version of copy() for when we only want to copy the info
1476 * pointer of an object, but reserve some padding after it. This is
1477 * used to optimise evacuation of BLACKHOLEs.
1482 copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *stp)
1487 nat size_to_copy_org = size_to_copy;
1490 TICK_GC_WORDS_COPIED(size_to_copy);
1491 if (stp->gen_no < evac_gen) {
1492 #ifdef NO_EAGER_PROMOTION
1493 failed_to_evac = rtsTrue;
1495 stp = &generations[evac_gen].steps[0];
1499 if (stp->hp + size_to_reserve >= stp->hpLim) {
1500 gc_alloc_block(stp);
1503 for(to = stp->hp, from = (P_)src; size_to_copy>0; --size_to_copy) {
1508 stp->hp += size_to_reserve;
1509 upd_evacuee(src,(StgClosure *)dest);
1511 // We store the size of the just evacuated object in the LDV word so that
1512 // the profiler can guess the position of the next object later.
1513 // size_to_copy_org is wrong because the closure already occupies size_to_reserve
1515 SET_EVACUAEE_FOR_LDV(src, size_to_reserve);
1517 if (size_to_reserve - size_to_copy_org > 0)
1518 FILL_SLOP(stp->hp - 1, (int)(size_to_reserve - size_to_copy_org));
1520 return (StgClosure *)dest;
1524 /* -----------------------------------------------------------------------------
1525 Evacuate a large object
1527 This just consists of removing the object from the (doubly-linked)
1528 step->large_objects list, and linking it on to the (singly-linked)
1529 step->new_large_objects list, from where it will be scavenged later.
1531 Convention: bd->flags has BF_EVACUATED set for a large object
1532 that has been evacuated, or unset otherwise.
1533 -------------------------------------------------------------------------- */
1537 evacuate_large(StgPtr p)
1539 bdescr *bd = Bdescr(p);
1542 // object must be at the beginning of the block (or be a ByteArray)
1543 ASSERT(get_itbl((StgClosure *)p)->type == ARR_WORDS ||
1544 (((W_)p & BLOCK_MASK) == 0));
1546 // already evacuated?
1547 if (bd->flags & BF_EVACUATED) {
1548 /* Don't forget to set the failed_to_evac flag if we didn't get
1549 * the desired destination (see comments in evacuate()).
1551 if (bd->gen_no < evac_gen) {
1552 failed_to_evac = rtsTrue;
1553 TICK_GC_FAILED_PROMOTION();
1559 // remove from large_object list
1561 bd->u.back->link = bd->link;
1562 } else { // first object in the list
1563 stp->large_objects = bd->link;
1566 bd->link->u.back = bd->u.back;
1569 /* link it on to the evacuated large object list of the destination step
1572 if (stp->gen_no < evac_gen) {
1573 #ifdef NO_EAGER_PROMOTION
1574 failed_to_evac = rtsTrue;
1576 stp = &generations[evac_gen].steps[0];
1581 bd->gen_no = stp->gen_no;
1582 bd->link = stp->new_large_objects;
1583 stp->new_large_objects = bd;
1584 bd->flags |= BF_EVACUATED;
1587 /* -----------------------------------------------------------------------------
1588 Adding a MUT_CONS to an older generation.
1590 This is necessary from time to time when we end up with an
1591 old-to-new generation pointer in a non-mutable object. We defer
1592 the promotion until the next GC.
1593 -------------------------------------------------------------------------- */
1596 mkMutCons(StgClosure *ptr, generation *gen)
1601 stp = &gen->steps[0];
1603 /* chain a new block onto the to-space for the destination step if
1606 if (stp->hp + sizeofW(StgIndOldGen) >= stp->hpLim) {
1607 gc_alloc_block(stp);
1610 q = (StgMutVar *)stp->hp;
1611 stp->hp += sizeofW(StgMutVar);
1613 SET_HDR(q,&stg_MUT_CONS_info,CCS_GC);
1615 recordOldToNewPtrs((StgMutClosure *)q);
1617 return (StgClosure *)q;
1620 /* -----------------------------------------------------------------------------
1623 This is called (eventually) for every live object in the system.
1625 The caller to evacuate specifies a desired generation in the
1626 evac_gen global variable. The following conditions apply to
1627 evacuating an object which resides in generation M when we're
1628 collecting up to generation N
1632 else evac to step->to
1634 if M < evac_gen evac to evac_gen, step 0
1636 if the object is already evacuated, then we check which generation
1639 if M >= evac_gen do nothing
1640 if M < evac_gen set failed_to_evac flag to indicate that we
1641 didn't manage to evacuate this object into evac_gen.
1646 evacuate() is the single most important function performance-wise
1647 in the GC. Various things have been tried to speed it up, but as
1648 far as I can tell the code generated by gcc 3.2 with -O2 is about
1649 as good as it's going to get. We pass the argument to evacuate()
1650 in a register using the 'regparm' attribute (see the prototype for
1651 evacuate() near the top of this file).
1653 Changing evacuate() to take an (StgClosure **) rather than
1654 returning the new pointer seems attractive, because we can avoid
1655 writing back the pointer when it hasn't changed (eg. for a static
1656 object, or an object in a generation > N). However, I tried it and
1657 it doesn't help. One reason is that the (StgClosure **) pointer
1658 gets spilled to the stack inside evacuate(), resulting in far more
1659 extra reads/writes than we save.
1660 -------------------------------------------------------------------------- */
1662 REGPARM1 static StgClosure *
1663 evacuate(StgClosure *q)
1668 const StgInfoTable *info;
1671 if (HEAP_ALLOCED(q)) {
1674 if (bd->gen_no > N) {
1675 /* Can't evacuate this object, because it's in a generation
1676 * older than the ones we're collecting. Let's hope that it's
1677 * in evac_gen or older, or we will have to arrange to track
1678 * this pointer using the mutable list.
1680 if (bd->gen_no < evac_gen) {
1682 failed_to_evac = rtsTrue;
1683 TICK_GC_FAILED_PROMOTION();
1688 /* evacuate large objects by re-linking them onto a different list.
1690 if (bd->flags & BF_LARGE) {
1692 if (info->type == TSO &&
1693 ((StgTSO *)q)->what_next == ThreadRelocated) {
1694 q = (StgClosure *)((StgTSO *)q)->link;
1697 evacuate_large((P_)q);
1701 /* If the object is in a step that we're compacting, then we
1702 * need to use an alternative evacuate procedure.
1704 if (bd->flags & BF_COMPACTED) {
1705 if (!is_marked((P_)q,bd)) {
1707 if (mark_stack_full()) {
1708 mark_stack_overflowed = rtsTrue;
1711 push_mark_stack((P_)q);
1719 else stp = NULL; // make sure copy() will crash if HEAP_ALLOCED is wrong
1722 // make sure the info pointer is into text space
1723 ASSERT(LOOKS_LIKE_CLOSURE_PTR(q));
1726 switch (info -> type) {
1730 return copy(q,sizeW_fromITBL(info),stp);
1734 StgWord w = (StgWord)q->payload[0];
1735 if (q->header.info == Czh_con_info &&
1736 // unsigned, so always true: (StgChar)w >= MIN_CHARLIKE &&
1737 (StgChar)w <= MAX_CHARLIKE) {
1738 return (StgClosure *)CHARLIKE_CLOSURE((StgChar)w);
1740 if (q->header.info == Izh_con_info &&
1741 (StgInt)w >= MIN_INTLIKE && (StgInt)w <= MAX_INTLIKE) {
1742 return (StgClosure *)INTLIKE_CLOSURE((StgInt)w);
1744 // else, fall through ...
1750 return copy(q,sizeofW(StgHeader)+1,stp);
1752 case THUNK_1_0: // here because of MIN_UPD_SIZE
1757 #ifdef NO_PROMOTE_THUNKS
1758 if (bd->gen_no == 0 &&
1759 bd->step->no != 0 &&
1760 bd->step->no == generations[bd->gen_no].n_steps-1) {
1764 return copy(q,sizeofW(StgHeader)+2,stp);
1772 return copy(q,sizeofW(StgHeader)+2,stp);
1778 case IND_OLDGEN_PERM:
1782 return copy(q,sizeW_fromITBL(info),stp);
1785 return copy(q,bco_sizeW((StgBCO *)q),stp);
1788 case SE_CAF_BLACKHOLE:
1791 return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
1794 to = copy(q,BLACKHOLE_sizeW(),stp);
1797 case THUNK_SELECTOR:
1801 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
1802 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1805 p = eval_thunk_selector(info->layout.selector_offset,
1809 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1811 // q is still BLACKHOLE'd.
1812 thunk_selector_depth++;
1814 thunk_selector_depth--;
1817 // We store the size of the just evacuated object in the
1818 // LDV word so that the profiler can guess the position of
1819 // the next object later.
1820 SET_EVACUAEE_FOR_LDV(q, THUNK_SELECTOR_sizeW());
1828 // follow chains of indirections, don't evacuate them
1829 q = ((StgInd*)q)->indirectee;
1833 if (info->srt_bitmap != 0 && major_gc &&
1834 THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
1835 THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
1836 static_objects = (StgClosure *)q;
1841 if (info->srt_bitmap != 0 && major_gc &&
1842 FUN_STATIC_LINK((StgClosure *)q) == NULL) {
1843 FUN_STATIC_LINK((StgClosure *)q) = static_objects;
1844 static_objects = (StgClosure *)q;
1849 /* If q->saved_info != NULL, then it's a revertible CAF - it'll be
1850 * on the CAF list, so don't do anything with it here (we'll
1851 * scavenge it later).
1854 && ((StgIndStatic *)q)->saved_info == NULL
1855 && IND_STATIC_LINK((StgClosure *)q) == NULL) {
1856 IND_STATIC_LINK((StgClosure *)q) = static_objects;
1857 static_objects = (StgClosure *)q;
1862 if (major_gc && STATIC_LINK(info,(StgClosure *)q) == NULL) {
1863 STATIC_LINK(info,(StgClosure *)q) = static_objects;
1864 static_objects = (StgClosure *)q;
1868 case CONSTR_INTLIKE:
1869 case CONSTR_CHARLIKE:
1870 case CONSTR_NOCAF_STATIC:
1871 /* no need to put these on the static linked list, they don't need
1885 // shouldn't see these
1886 barf("evacuate: stack frame at %p\n", q);
1890 return copy(q,pap_sizeW((StgPAP*)q),stp);
1893 return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp);
1896 /* Already evacuated, just return the forwarding address.
1897 * HOWEVER: if the requested destination generation (evac_gen) is
1898 * older than the actual generation (because the object was
1899 * already evacuated to a younger generation) then we have to
1900 * set the failed_to_evac flag to indicate that we couldn't
1901 * manage to promote the object to the desired generation.
1903 if (evac_gen > 0) { // optimisation
1904 StgClosure *p = ((StgEvacuated*)q)->evacuee;
1905 if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < evac_gen) {
1906 failed_to_evac = rtsTrue;
1907 TICK_GC_FAILED_PROMOTION();
1910 return ((StgEvacuated*)q)->evacuee;
1913 // just copy the block
1914 return copy(q,arr_words_sizeW((StgArrWords *)q),stp);
1917 case MUT_ARR_PTRS_FROZEN:
1918 // just copy the block
1919 return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
1923 StgTSO *tso = (StgTSO *)q;
1925 /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
1927 if (tso->what_next == ThreadRelocated) {
1928 q = (StgClosure *)tso->link;
1932 /* To evacuate a small TSO, we need to relocate the update frame
1939 new_tso = (StgTSO *)copyPart((StgClosure *)tso,
1941 sizeofW(StgTSO), stp);
1942 move_TSO(tso, new_tso);
1943 for (p = tso->sp, q = new_tso->sp;
1944 p < tso->stack+tso->stack_size;) {
1948 return (StgClosure *)new_tso;
1953 case RBH: // cf. BLACKHOLE_BQ
1955 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
1956 to = copy(q,BLACKHOLE_sizeW(),stp);
1957 //ToDo: derive size etc from reverted IP
1958 //to = copy(q,size,stp);
1960 debugBelch("@@ evacuate: RBH %p (%s) to %p (%s)",
1961 q, info_type(q), to, info_type(to)));
1966 ASSERT(sizeofW(StgBlockedFetch) >= MIN_NONUPD_SIZE);
1967 to = copy(q,sizeofW(StgBlockedFetch),stp);
1969 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
1970 q, info_type(q), to, info_type(to)));
1977 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1978 to = copy(q,sizeofW(StgFetchMe),stp);
1980 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
1981 q, info_type(q), to, info_type(to)));
1985 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1986 to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
1988 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
1989 q, info_type(q), to, info_type(to)));
1994 barf("evacuate: strange closure type %d", (int)(info->type));
2000 /* -----------------------------------------------------------------------------
2001 Evaluate a THUNK_SELECTOR if possible.
2003 returns: NULL if we couldn't evaluate this THUNK_SELECTOR, or
2004 a closure pointer if we evaluated it and this is the result. Note
2005 that "evaluating" the THUNK_SELECTOR doesn't necessarily mean
2006 reducing it to HNF, just that we have eliminated the selection.
2007 The result might be another thunk, or even another THUNK_SELECTOR.
2009 If the return value is non-NULL, the original selector thunk has
2010 been BLACKHOLE'd, and should be updated with an indirection or a
2011 forwarding pointer. If the return value is NULL, then the selector
2013 -------------------------------------------------------------------------- */
2015 static inline rtsBool
2016 is_to_space ( StgClosure *p )
2020 bd = Bdescr((StgPtr)p);
2021 if (HEAP_ALLOCED(p) &&
2022 ((bd->flags & BF_EVACUATED)
2023 || ((bd->flags & BF_COMPACTED) &&
2024 is_marked((P_)p,bd)))) {
2032 eval_thunk_selector( nat field, StgSelector * p )
2035 const StgInfoTable *info_ptr;
2036 StgClosure *selectee;
2038 selectee = p->selectee;
2040 // Save the real info pointer (NOTE: not the same as get_itbl()).
2041 info_ptr = p->header.info;
2043 // If the THUNK_SELECTOR is in a generation that we are not
2044 // collecting, then bail out early. We won't be able to save any
2045 // space in any case, and updating with an indirection is trickier
2047 if (Bdescr((StgPtr)p)->gen_no > N) {
2051 // BLACKHOLE the selector thunk, since it is now under evaluation.
2052 // This is important to stop us going into an infinite loop if
2053 // this selector thunk eventually refers to itself.
2054 SET_INFO(p,&stg_BLACKHOLE_info);
2058 // We don't want to end up in to-space, because this causes
2059 // problems when the GC later tries to evacuate the result of
2060 // eval_thunk_selector(). There are various ways this could
2063 // 1. following an IND_STATIC
2065 // 2. when the old generation is compacted, the mark phase updates
2066 // from-space pointers to be to-space pointers, and we can't
2067 // reliably tell which we're following (eg. from an IND_STATIC).
2069 // 3. compacting GC again: if we're looking at a constructor in
2070 // the compacted generation, it might point directly to objects
2071 // in to-space. We must bale out here, otherwise doing the selection
2072 // will result in a to-space pointer being returned.
2074 // (1) is dealt with using a BF_EVACUATED test on the
2075 // selectee. (2) and (3): we can tell if we're looking at an
2076 // object in the compacted generation that might point to
2077 // to-space objects by testing that (a) it is BF_COMPACTED, (b)
2078 // the compacted generation is being collected, and (c) the
2079 // object is marked. Only a marked object may have pointers that
2080 // point to to-space objects, because that happens when
2083 // The to-space test is now embodied in the in_to_space() inline
2084 // function, as it is re-used below.
2086 if (is_to_space(selectee)) {
2090 info = get_itbl(selectee);
2091 switch (info->type) {
2099 case CONSTR_NOCAF_STATIC:
2100 // check that the size is in range
2101 ASSERT(field < (StgWord32)(info->layout.payload.ptrs +
2102 info->layout.payload.nptrs));
2104 // Select the right field from the constructor, and check
2105 // that the result isn't in to-space. It might be in
2106 // to-space if, for example, this constructor contains
2107 // pointers to younger-gen objects (and is on the mut-once
2112 q = selectee->payload[field];
2113 if (is_to_space(q)) {
2123 case IND_OLDGEN_PERM:
2125 selectee = ((StgInd *)selectee)->indirectee;
2129 // We don't follow pointers into to-space; the constructor
2130 // has already been evacuated, so we won't save any space
2131 // leaks by evaluating this selector thunk anyhow.
2134 case THUNK_SELECTOR:
2138 // check that we don't recurse too much, re-using the
2139 // depth bound also used in evacuate().
2140 thunk_selector_depth++;
2141 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
2145 val = eval_thunk_selector(info->layout.selector_offset,
2146 (StgSelector *)selectee);
2148 thunk_selector_depth--;
2153 // We evaluated this selector thunk, so update it with
2154 // an indirection. NOTE: we don't use UPD_IND here,
2155 // because we are guaranteed that p is in a generation
2156 // that we are collecting, and we never want to put the
2157 // indirection on a mutable list.
2159 // For the purposes of LDV profiling, we have destroyed
2160 // the original selector thunk.
2161 SET_INFO(p, info_ptr);
2162 LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(selectee);
2164 ((StgInd *)selectee)->indirectee = val;
2165 SET_INFO(selectee,&stg_IND_info);
2167 // For the purposes of LDV profiling, we have created an
2169 LDV_RECORD_CREATE(selectee);
2186 case SE_CAF_BLACKHOLE:
2199 // not evaluated yet
2203 barf("eval_thunk_selector: strange selectee %d",
2208 // We didn't manage to evaluate this thunk; restore the old info pointer
2209 SET_INFO(p, info_ptr);
2213 /* -----------------------------------------------------------------------------
2214 move_TSO is called to update the TSO structure after it has been
2215 moved from one place to another.
2216 -------------------------------------------------------------------------- */
2219 move_TSO (StgTSO *src, StgTSO *dest)
2223 // relocate the stack pointer...
2224 diff = (StgPtr)dest - (StgPtr)src; // In *words*
2225 dest->sp = (StgPtr)dest->sp + diff;
2228 /* Similar to scavenge_large_bitmap(), but we don't write back the
2229 * pointers we get back from evacuate().
2232 scavenge_large_srt_bitmap( StgLargeSRT *large_srt )
2239 bitmap = large_srt->l.bitmap[b];
2240 size = (nat)large_srt->l.size;
2241 p = (StgClosure **)large_srt->srt;
2242 for (i = 0; i < size; ) {
2243 if ((bitmap & 1) != 0) {
2248 if (i % BITS_IN(W_) == 0) {
2250 bitmap = large_srt->l.bitmap[b];
2252 bitmap = bitmap >> 1;
2257 /* evacuate the SRT. If srt_bitmap is zero, then there isn't an
2258 * srt field in the info table. That's ok, because we'll
2259 * never dereference it.
2262 scavenge_srt (StgClosure **srt, nat srt_bitmap)
2267 bitmap = srt_bitmap;
2270 if (bitmap == (StgHalfWord)(-1)) {
2271 scavenge_large_srt_bitmap( (StgLargeSRT *)srt );
2275 while (bitmap != 0) {
2276 if ((bitmap & 1) != 0) {
2277 #ifdef ENABLE_WIN32_DLL_SUPPORT
2278 // Special-case to handle references to closures hiding out in DLLs, since
2279 // double indirections required to get at those. The code generator knows
2280 // which is which when generating the SRT, so it stores the (indirect)
2281 // reference to the DLL closure in the table by first adding one to it.
2282 // We check for this here, and undo the addition before evacuating it.
2284 // If the SRT entry hasn't got bit 0 set, the SRT entry points to a
2285 // closure that's fixed at link-time, and no extra magic is required.
2286 if ( (unsigned long)(*srt) & 0x1 ) {
2287 evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
2296 bitmap = bitmap >> 1;
2302 scavenge_thunk_srt(const StgInfoTable *info)
2304 StgThunkInfoTable *thunk_info;
2306 thunk_info = itbl_to_thunk_itbl(info);
2307 scavenge_srt((StgClosure **)thunk_info->srt, thunk_info->i.srt_bitmap);
2311 scavenge_fun_srt(const StgInfoTable *info)
2313 StgFunInfoTable *fun_info;
2315 fun_info = itbl_to_fun_itbl(info);
2316 scavenge_srt((StgClosure **)fun_info->f.srt, fun_info->i.srt_bitmap);
2320 scavenge_ret_srt(const StgInfoTable *info)
2322 StgRetInfoTable *ret_info;
2324 ret_info = itbl_to_ret_itbl(info);
2325 scavenge_srt((StgClosure **)ret_info->srt, ret_info->i.srt_bitmap);
2328 /* -----------------------------------------------------------------------------
2330 -------------------------------------------------------------------------- */
2333 scavengeTSO (StgTSO *tso)
2335 // chase the link field for any TSOs on the same queue
2336 (StgClosure *)tso->link = evacuate((StgClosure *)tso->link);
2337 if ( tso->why_blocked == BlockedOnMVar
2338 || tso->why_blocked == BlockedOnBlackHole
2339 || tso->why_blocked == BlockedOnException
2341 || tso->why_blocked == BlockedOnGA
2342 || tso->why_blocked == BlockedOnGA_NoSend
2345 tso->block_info.closure = evacuate(tso->block_info.closure);
2347 if ( tso->blocked_exceptions != NULL ) {
2348 tso->blocked_exceptions =
2349 (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
2352 // scavenge this thread's stack
2353 scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
2356 /* -----------------------------------------------------------------------------
2357 Blocks of function args occur on the stack (at the top) and
2359 -------------------------------------------------------------------------- */
2361 STATIC_INLINE StgPtr
2362 scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
2369 switch (fun_info->f.fun_type) {
2371 bitmap = BITMAP_BITS(fun_info->f.bitmap);
2372 size = BITMAP_SIZE(fun_info->f.bitmap);
2375 size = ((StgLargeBitmap *)fun_info->f.bitmap)->size;
2376 scavenge_large_bitmap(p, (StgLargeBitmap *)fun_info->f.bitmap, size);
2380 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2381 size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->f.fun_type]);
2384 if ((bitmap & 1) == 0) {
2385 (StgClosure *)*p = evacuate((StgClosure *)*p);
2388 bitmap = bitmap >> 1;
2396 STATIC_INLINE StgPtr
2397 scavenge_PAP (StgPAP *pap)
2400 StgWord bitmap, size;
2401 StgFunInfoTable *fun_info;
2403 pap->fun = evacuate(pap->fun);
2404 fun_info = get_fun_itbl(pap->fun);
2405 ASSERT(fun_info->i.type != PAP);
2407 p = (StgPtr)pap->payload;
2410 switch (fun_info->f.fun_type) {
2412 bitmap = BITMAP_BITS(fun_info->f.bitmap);
2415 scavenge_large_bitmap(p, (StgLargeBitmap *)fun_info->f.bitmap, size);
2419 scavenge_large_bitmap((StgPtr)pap->payload, BCO_BITMAP(pap->fun), size);
2423 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2427 if ((bitmap & 1) == 0) {
2428 (StgClosure *)*p = evacuate((StgClosure *)*p);
2431 bitmap = bitmap >> 1;
2439 /* -----------------------------------------------------------------------------
2440 Scavenge a given step until there are no more objects in this step
2443 evac_gen is set by the caller to be either zero (for a step in a
2444 generation < N) or G where G is the generation of the step being
2447 We sometimes temporarily change evac_gen back to zero if we're
2448 scavenging a mutable object where early promotion isn't such a good
2450 -------------------------------------------------------------------------- */
2458 nat saved_evac_gen = evac_gen;
2463 failed_to_evac = rtsFalse;
2465 /* scavenge phase - standard breadth-first scavenging of the
2469 while (bd != stp->hp_bd || p < stp->hp) {
2471 // If we're at the end of this block, move on to the next block
2472 if (bd != stp->hp_bd && p == bd->free) {
2478 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2479 info = get_itbl((StgClosure *)p);
2481 ASSERT(thunk_selector_depth == 0);
2484 switch (info->type) {
2487 /* treat MVars specially, because we don't want to evacuate the
2488 * mut_link field in the middle of the closure.
2491 StgMVar *mvar = ((StgMVar *)p);
2493 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
2494 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
2495 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
2496 evac_gen = saved_evac_gen;
2497 recordMutable((StgMutClosure *)mvar);
2498 failed_to_evac = rtsFalse; // mutable.
2499 p += sizeofW(StgMVar);
2504 scavenge_fun_srt(info);
2505 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2506 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2507 p += sizeofW(StgHeader) + 2;
2511 scavenge_thunk_srt(info);
2513 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2514 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2515 p += sizeofW(StgHeader) + 2;
2519 scavenge_thunk_srt(info);
2520 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2521 p += sizeofW(StgHeader) + 2; // MIN_UPD_SIZE
2525 scavenge_fun_srt(info);
2527 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2528 p += sizeofW(StgHeader) + 1;
2532 scavenge_thunk_srt(info);
2533 p += sizeofW(StgHeader) + 2; // MIN_UPD_SIZE
2537 scavenge_fun_srt(info);
2539 p += sizeofW(StgHeader) + 1;
2543 scavenge_thunk_srt(info);
2544 p += sizeofW(StgHeader) + 2;
2548 scavenge_fun_srt(info);
2550 p += sizeofW(StgHeader) + 2;
2554 scavenge_thunk_srt(info);
2555 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2556 p += sizeofW(StgHeader) + 2;
2560 scavenge_fun_srt(info);
2562 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2563 p += sizeofW(StgHeader) + 2;
2567 scavenge_fun_srt(info);
2571 scavenge_thunk_srt(info);
2582 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2583 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2584 (StgClosure *)*p = evacuate((StgClosure *)*p);
2586 p += info->layout.payload.nptrs;
2591 StgBCO *bco = (StgBCO *)p;
2592 (StgClosure *)bco->instrs = evacuate((StgClosure *)bco->instrs);
2593 (StgClosure *)bco->literals = evacuate((StgClosure *)bco->literals);
2594 (StgClosure *)bco->ptrs = evacuate((StgClosure *)bco->ptrs);
2595 (StgClosure *)bco->itbls = evacuate((StgClosure *)bco->itbls);
2596 p += bco_sizeW(bco);
2601 if (stp->gen->no != 0) {
2604 // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an
2605 // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
2606 LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
2609 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
2611 SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
2613 // We pretend that p has just been created.
2614 LDV_RECORD_CREATE((StgClosure *)p);
2617 case IND_OLDGEN_PERM:
2618 ((StgIndOldGen *)p)->indirectee =
2619 evacuate(((StgIndOldGen *)p)->indirectee);
2620 if (failed_to_evac) {
2621 failed_to_evac = rtsFalse;
2622 recordOldToNewPtrs((StgMutClosure *)p);
2624 p += sizeofW(StgIndOldGen);
2629 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2630 evac_gen = saved_evac_gen;
2631 recordMutable((StgMutClosure *)p);
2632 failed_to_evac = rtsFalse; // mutable anyhow
2633 p += sizeofW(StgMutVar);
2638 failed_to_evac = rtsFalse; // mutable anyhow
2639 p += sizeofW(StgMutVar);
2643 case SE_CAF_BLACKHOLE:
2646 p += BLACKHOLE_sizeW();
2651 StgBlockingQueue *bh = (StgBlockingQueue *)p;
2652 (StgClosure *)bh->blocking_queue =
2653 evacuate((StgClosure *)bh->blocking_queue);
2654 recordMutable((StgMutClosure *)bh);
2655 failed_to_evac = rtsFalse;
2656 p += BLACKHOLE_sizeW();
2660 case THUNK_SELECTOR:
2662 StgSelector *s = (StgSelector *)p;
2663 s->selectee = evacuate(s->selectee);
2664 p += THUNK_SELECTOR_sizeW();
2668 // A chunk of stack saved in a heap object
2671 StgAP_STACK *ap = (StgAP_STACK *)p;
2673 ap->fun = evacuate(ap->fun);
2674 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2675 p = (StgPtr)ap->payload + ap->size;
2681 p = scavenge_PAP((StgPAP *)p);
2685 // nothing to follow
2686 p += arr_words_sizeW((StgArrWords *)p);
2690 // follow everything
2694 evac_gen = 0; // repeatedly mutable
2695 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2696 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2697 (StgClosure *)*p = evacuate((StgClosure *)*p);
2699 evac_gen = saved_evac_gen;
2700 recordMutable((StgMutClosure *)q);
2701 failed_to_evac = rtsFalse; // mutable anyhow.
2705 case MUT_ARR_PTRS_FROZEN:
2706 // follow everything
2710 // Set the mut_link field to NULL, so that we will put this
2711 // array back on the mutable list if it is subsequently thawed
2713 ((StgMutArrPtrs*)p)->mut_link = NULL;
2715 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2716 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2717 (StgClosure *)*p = evacuate((StgClosure *)*p);
2719 // it's tempting to recordMutable() if failed_to_evac is
2720 // false, but that breaks some assumptions (eg. every
2721 // closure on the mutable list is supposed to have the MUT
2722 // flag set, and MUT_ARR_PTRS_FROZEN doesn't).
2728 StgTSO *tso = (StgTSO *)p;
2731 evac_gen = saved_evac_gen;
2732 recordMutable((StgMutClosure *)tso);
2733 failed_to_evac = rtsFalse; // mutable anyhow.
2734 p += tso_sizeW(tso);
2739 case RBH: // cf. BLACKHOLE_BQ
2742 nat size, ptrs, nonptrs, vhs;
2744 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2746 StgRBH *rbh = (StgRBH *)p;
2747 (StgClosure *)rbh->blocking_queue =
2748 evacuate((StgClosure *)rbh->blocking_queue);
2749 recordMutable((StgMutClosure *)to);
2750 failed_to_evac = rtsFalse; // mutable anyhow.
2752 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2753 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2754 // ToDo: use size of reverted closure here!
2755 p += BLACKHOLE_sizeW();
2761 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2762 // follow the pointer to the node which is being demanded
2763 (StgClosure *)bf->node =
2764 evacuate((StgClosure *)bf->node);
2765 // follow the link to the rest of the blocking queue
2766 (StgClosure *)bf->link =
2767 evacuate((StgClosure *)bf->link);
2768 if (failed_to_evac) {
2769 failed_to_evac = rtsFalse;
2770 recordMutable((StgMutClosure *)bf);
2773 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
2774 bf, info_type((StgClosure *)bf),
2775 bf->node, info_type(bf->node)));
2776 p += sizeofW(StgBlockedFetch);
2784 p += sizeofW(StgFetchMe);
2785 break; // nothing to do in this case
2787 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
2789 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
2790 (StgClosure *)fmbq->blocking_queue =
2791 evacuate((StgClosure *)fmbq->blocking_queue);
2792 if (failed_to_evac) {
2793 failed_to_evac = rtsFalse;
2794 recordMutable((StgMutClosure *)fmbq);
2797 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
2798 p, info_type((StgClosure *)p)));
2799 p += sizeofW(StgFetchMeBlockingQueue);
2805 barf("scavenge: unimplemented/strange closure type %d @ %p",
2809 /* If we didn't manage to promote all the objects pointed to by
2810 * the current object, then we have to designate this object as
2811 * mutable (because it contains old-to-new generation pointers).
2813 if (failed_to_evac) {
2814 failed_to_evac = rtsFalse;
2815 mkMutCons((StgClosure *)q, &generations[evac_gen]);
2823 /* -----------------------------------------------------------------------------
2824 Scavenge everything on the mark stack.
2826 This is slightly different from scavenge():
2827 - we don't walk linearly through the objects, so the scavenger
2828 doesn't need to advance the pointer on to the next object.
2829 -------------------------------------------------------------------------- */
2832 scavenge_mark_stack(void)
2838 evac_gen = oldest_gen->no;
2839 saved_evac_gen = evac_gen;
2842 while (!mark_stack_empty()) {
2843 p = pop_mark_stack();
2845 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2846 info = get_itbl((StgClosure *)p);
2849 switch (info->type) {
2852 /* treat MVars specially, because we don't want to evacuate the
2853 * mut_link field in the middle of the closure.
2856 StgMVar *mvar = ((StgMVar *)p);
2858 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
2859 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
2860 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
2861 evac_gen = saved_evac_gen;
2862 failed_to_evac = rtsFalse; // mutable.
2867 scavenge_fun_srt(info);
2868 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2869 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2873 scavenge_thunk_srt(info);
2875 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2876 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2881 scavenge_fun_srt(info);
2882 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2887 scavenge_thunk_srt(info);
2890 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2895 scavenge_fun_srt(info);
2900 scavenge_thunk_srt(info);
2908 scavenge_fun_srt(info);
2912 scavenge_thunk_srt(info);
2923 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2924 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2925 (StgClosure *)*p = evacuate((StgClosure *)*p);
2931 StgBCO *bco = (StgBCO *)p;
2932 (StgClosure *)bco->instrs = evacuate((StgClosure *)bco->instrs);
2933 (StgClosure *)bco->literals = evacuate((StgClosure *)bco->literals);
2934 (StgClosure *)bco->ptrs = evacuate((StgClosure *)bco->ptrs);
2935 (StgClosure *)bco->itbls = evacuate((StgClosure *)bco->itbls);
2940 // don't need to do anything here: the only possible case
2941 // is that we're in a 1-space compacting collector, with
2942 // no "old" generation.
2946 case IND_OLDGEN_PERM:
2947 ((StgIndOldGen *)p)->indirectee =
2948 evacuate(((StgIndOldGen *)p)->indirectee);
2949 if (failed_to_evac) {
2950 recordOldToNewPtrs((StgMutClosure *)p);
2952 failed_to_evac = rtsFalse;
2957 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2958 evac_gen = saved_evac_gen;
2959 failed_to_evac = rtsFalse;
2964 failed_to_evac = rtsFalse;
2968 case SE_CAF_BLACKHOLE:
2976 StgBlockingQueue *bh = (StgBlockingQueue *)p;
2977 (StgClosure *)bh->blocking_queue =
2978 evacuate((StgClosure *)bh->blocking_queue);
2979 failed_to_evac = rtsFalse;
2983 case THUNK_SELECTOR:
2985 StgSelector *s = (StgSelector *)p;
2986 s->selectee = evacuate(s->selectee);
2990 // A chunk of stack saved in a heap object
2993 StgAP_STACK *ap = (StgAP_STACK *)p;
2995 ap->fun = evacuate(ap->fun);
2996 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3002 scavenge_PAP((StgPAP *)p);
3006 // follow everything
3010 evac_gen = 0; // repeatedly mutable
3011 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3012 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3013 (StgClosure *)*p = evacuate((StgClosure *)*p);
3015 evac_gen = saved_evac_gen;
3016 failed_to_evac = rtsFalse; // mutable anyhow.
3020 case MUT_ARR_PTRS_FROZEN:
3021 // follow everything
3025 // Set the mut_link field to NULL, so that we will put this
3026 // array on the mutable list if it is subsequently thawed
3028 ((StgMutArrPtrs*)p)->mut_link = NULL;
3030 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3031 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3032 (StgClosure *)*p = evacuate((StgClosure *)*p);
3039 StgTSO *tso = (StgTSO *)p;
3042 evac_gen = saved_evac_gen;
3043 failed_to_evac = rtsFalse;
3048 case RBH: // cf. BLACKHOLE_BQ
3051 nat size, ptrs, nonptrs, vhs;
3053 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3055 StgRBH *rbh = (StgRBH *)p;
3056 (StgClosure *)rbh->blocking_queue =
3057 evacuate((StgClosure *)rbh->blocking_queue);
3058 recordMutable((StgMutClosure *)rbh);
3059 failed_to_evac = rtsFalse; // mutable anyhow.
3061 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3062 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3068 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3069 // follow the pointer to the node which is being demanded
3070 (StgClosure *)bf->node =
3071 evacuate((StgClosure *)bf->node);
3072 // follow the link to the rest of the blocking queue
3073 (StgClosure *)bf->link =
3074 evacuate((StgClosure *)bf->link);
3075 if (failed_to_evac) {
3076 failed_to_evac = rtsFalse;
3077 recordMutable((StgMutClosure *)bf);
3080 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3081 bf, info_type((StgClosure *)bf),
3082 bf->node, info_type(bf->node)));
3090 break; // nothing to do in this case
3092 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
3094 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3095 (StgClosure *)fmbq->blocking_queue =
3096 evacuate((StgClosure *)fmbq->blocking_queue);
3097 if (failed_to_evac) {
3098 failed_to_evac = rtsFalse;
3099 recordMutable((StgMutClosure *)fmbq);
3102 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3103 p, info_type((StgClosure *)p)));
3109 barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p",
3113 if (failed_to_evac) {
3114 failed_to_evac = rtsFalse;
3115 mkMutCons((StgClosure *)q, &generations[evac_gen]);
3118 // mark the next bit to indicate "scavenged"
3119 mark(q+1, Bdescr(q));
3121 } // while (!mark_stack_empty())
3123 // start a new linear scan if the mark stack overflowed at some point
3124 if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
3125 IF_DEBUG(gc, debugBelch("scavenge_mark_stack: starting linear scan"));
3126 mark_stack_overflowed = rtsFalse;
3127 oldgen_scan_bd = oldest_gen->steps[0].blocks;
3128 oldgen_scan = oldgen_scan_bd->start;
3131 if (oldgen_scan_bd) {
3132 // push a new thing on the mark stack
3134 // find a closure that is marked but not scavenged, and start
3136 while (oldgen_scan < oldgen_scan_bd->free
3137 && !is_marked(oldgen_scan,oldgen_scan_bd)) {
3141 if (oldgen_scan < oldgen_scan_bd->free) {
3143 // already scavenged?
3144 if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
3145 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3148 push_mark_stack(oldgen_scan);
3149 // ToDo: bump the linear scan by the actual size of the object
3150 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3154 oldgen_scan_bd = oldgen_scan_bd->link;
3155 if (oldgen_scan_bd != NULL) {
3156 oldgen_scan = oldgen_scan_bd->start;
3162 /* -----------------------------------------------------------------------------
3163 Scavenge one object.
3165 This is used for objects that are temporarily marked as mutable
3166 because they contain old-to-new generation pointers. Only certain
3167 objects can have this property.
3168 -------------------------------------------------------------------------- */
3171 scavenge_one(StgPtr p)
3173 const StgInfoTable *info;
3174 nat saved_evac_gen = evac_gen;
3177 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3178 info = get_itbl((StgClosure *)p);
3180 switch (info->type) {
3183 case FUN_1_0: // hardly worth specialising these guys
3203 case IND_OLDGEN_PERM:
3207 end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3208 for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
3209 (StgClosure *)*q = evacuate((StgClosure *)*q);
3215 case SE_CAF_BLACKHOLE:
3220 case THUNK_SELECTOR:
3222 StgSelector *s = (StgSelector *)p;
3223 s->selectee = evacuate(s->selectee);
3228 // nothing to follow
3233 // follow everything
3236 evac_gen = 0; // repeatedly mutable
3237 recordMutable((StgMutClosure *)p);
3238 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3239 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3240 (StgClosure *)*p = evacuate((StgClosure *)*p);
3242 evac_gen = saved_evac_gen;
3243 failed_to_evac = rtsFalse;
3247 case MUT_ARR_PTRS_FROZEN:
3249 // follow everything
3252 // Set the mut_link field to NULL, so that we will put this
3253 // array on the mutable list if it is subsequently thawed
3255 ((StgMutArrPtrs*)p)->mut_link = NULL;
3257 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3258 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3259 (StgClosure *)*p = evacuate((StgClosure *)*p);
3266 StgTSO *tso = (StgTSO *)p;
3268 evac_gen = 0; // repeatedly mutable
3270 recordMutable((StgMutClosure *)tso);
3271 evac_gen = saved_evac_gen;
3272 failed_to_evac = rtsFalse;
3278 StgAP_STACK *ap = (StgAP_STACK *)p;
3280 ap->fun = evacuate(ap->fun);
3281 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3282 p = (StgPtr)ap->payload + ap->size;
3288 p = scavenge_PAP((StgPAP *)p);
3292 // This might happen if for instance a MUT_CONS was pointing to a
3293 // THUNK which has since been updated. The IND_OLDGEN will
3294 // be on the mutable list anyway, so we don't need to do anything
3299 barf("scavenge_one: strange object %d", (int)(info->type));
3302 no_luck = failed_to_evac;
3303 failed_to_evac = rtsFalse;
3307 /* -----------------------------------------------------------------------------
3308 Scavenging mutable lists.
3310 We treat the mutable list of each generation > N (i.e. all the
3311 generations older than the one being collected) as roots. We also
3312 remove non-mutable objects from the mutable list at this point.
3313 -------------------------------------------------------------------------- */
3316 scavenge_mut_once_list(generation *gen)
3318 const StgInfoTable *info;
3319 StgMutClosure *p, *next, *new_list;
3321 p = gen->mut_once_list;
3322 new_list = END_MUT_LIST;
3326 failed_to_evac = rtsFalse;
3328 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
3330 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3333 if (info->type==RBH)
3334 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3336 switch(info->type) {
3339 case IND_OLDGEN_PERM:
3341 /* Try to pull the indirectee into this generation, so we can
3342 * remove the indirection from the mutable list.
3344 ((StgIndOldGen *)p)->indirectee =
3345 evacuate(((StgIndOldGen *)p)->indirectee);
3347 #if 0 && defined(DEBUG)
3348 if (RtsFlags.DebugFlags.gc)
3349 /* Debugging code to print out the size of the thing we just
3353 StgPtr start = gen->steps[0].scan;
3354 bdescr *start_bd = gen->steps[0].scan_bd;
3356 scavenge(&gen->steps[0]);
3357 if (start_bd != gen->steps[0].scan_bd) {
3358 size += (P_)BLOCK_ROUND_UP(start) - start;
3359 start_bd = start_bd->link;
3360 while (start_bd != gen->steps[0].scan_bd) {
3361 size += BLOCK_SIZE_W;
3362 start_bd = start_bd->link;
3364 size += gen->steps[0].scan -
3365 (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
3367 size = gen->steps[0].scan - start;
3369 debugBelch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
3373 /* failed_to_evac might happen if we've got more than two
3374 * generations, we're collecting only generation 0, the
3375 * indirection resides in generation 2 and the indirectee is
3378 if (failed_to_evac) {
3379 failed_to_evac = rtsFalse;
3380 p->mut_link = new_list;
3383 /* the mut_link field of an IND_STATIC is overloaded as the
3384 * static link field too (it just so happens that we don't need
3385 * both at the same time), so we need to NULL it out when
3386 * removing this object from the mutable list because the static
3387 * link fields are all assumed to be NULL before doing a major
3395 /* MUT_CONS is a kind of MUT_VAR, except it that we try to remove
3396 * it from the mutable list if possible by promoting whatever it
3399 if (scavenge_one((StgPtr)((StgMutVar *)p)->var)) {
3400 /* didn't manage to promote everything, so put the
3401 * MUT_CONS back on the list.
3403 p->mut_link = new_list;
3409 // shouldn't have anything else on the mutables list
3410 barf("scavenge_mut_once_list: strange object? %d", (int)(info->type));
3414 gen->mut_once_list = new_list;
3419 scavenge_mutable_list(generation *gen)
3421 const StgInfoTable *info;
3422 StgMutClosure *p, *next;
3424 p = gen->saved_mut_list;
3428 failed_to_evac = rtsFalse;
3430 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
3432 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3435 if (info->type==RBH)
3436 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3438 switch(info->type) {
3441 // follow everything
3442 p->mut_link = gen->mut_list;
3447 end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3448 for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
3449 (StgClosure *)*q = evacuate((StgClosure *)*q);
3454 // Happens if a MUT_ARR_PTRS in the old generation is frozen
3455 case MUT_ARR_PTRS_FROZEN:
3460 end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3461 for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
3462 (StgClosure *)*q = evacuate((StgClosure *)*q);
3465 // Set the mut_link field to NULL, so that we will put this
3466 // array back on the mutable list if it is subsequently thawed
3469 if (failed_to_evac) {
3470 failed_to_evac = rtsFalse;
3471 mkMutCons((StgClosure *)p, gen);
3477 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3478 p->mut_link = gen->mut_list;
3484 StgMVar *mvar = (StgMVar *)p;
3485 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
3486 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
3487 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
3488 p->mut_link = gen->mut_list;
3495 StgTSO *tso = (StgTSO *)p;
3499 /* Don't take this TSO off the mutable list - it might still
3500 * point to some younger objects (because we set evac_gen to 0
3503 tso->mut_link = gen->mut_list;
3504 gen->mut_list = (StgMutClosure *)tso;
3510 StgBlockingQueue *bh = (StgBlockingQueue *)p;
3511 (StgClosure *)bh->blocking_queue =
3512 evacuate((StgClosure *)bh->blocking_queue);
3513 p->mut_link = gen->mut_list;
3518 /* Happens if a BLACKHOLE_BQ in the old generation is updated:
3521 case IND_OLDGEN_PERM:
3522 /* Try to pull the indirectee into this generation, so we can
3523 * remove the indirection from the mutable list.
3526 ((StgIndOldGen *)p)->indirectee =
3527 evacuate(((StgIndOldGen *)p)->indirectee);
3530 if (failed_to_evac) {
3531 failed_to_evac = rtsFalse;
3532 p->mut_link = gen->mut_once_list;
3533 gen->mut_once_list = p;
3540 // HWL: check whether all of these are necessary
3542 case RBH: // cf. BLACKHOLE_BQ
3544 // nat size, ptrs, nonptrs, vhs;
3546 // StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3547 StgRBH *rbh = (StgRBH *)p;
3548 (StgClosure *)rbh->blocking_queue =
3549 evacuate((StgClosure *)rbh->blocking_queue);
3550 if (failed_to_evac) {
3551 failed_to_evac = rtsFalse;
3552 recordMutable((StgMutClosure *)rbh);
3554 // ToDo: use size of reverted closure here!
3555 p += BLACKHOLE_sizeW();
3561 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3562 // follow the pointer to the node which is being demanded
3563 (StgClosure *)bf->node =
3564 evacuate((StgClosure *)bf->node);
3565 // follow the link to the rest of the blocking queue
3566 (StgClosure *)bf->link =
3567 evacuate((StgClosure *)bf->link);
3568 if (failed_to_evac) {
3569 failed_to_evac = rtsFalse;
3570 recordMutable((StgMutClosure *)bf);
3572 p += sizeofW(StgBlockedFetch);
3578 barf("scavenge_mutable_list: REMOTE_REF %d", (int)(info->type));
3581 p += sizeofW(StgFetchMe);
3582 break; // nothing to do in this case
3584 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
3586 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3587 (StgClosure *)fmbq->blocking_queue =
3588 evacuate((StgClosure *)fmbq->blocking_queue);
3589 if (failed_to_evac) {
3590 failed_to_evac = rtsFalse;
3591 recordMutable((StgMutClosure *)fmbq);
3593 p += sizeofW(StgFetchMeBlockingQueue);
3599 // shouldn't have anything else on the mutables list
3600 barf("scavenge_mutable_list: strange object? %d", (int)(info->type));
3607 scavenge_static(void)
3609 StgClosure* p = static_objects;
3610 const StgInfoTable *info;
3612 /* Always evacuate straight to the oldest generation for static
3614 evac_gen = oldest_gen->no;
3616 /* keep going until we've scavenged all the objects on the linked
3618 while (p != END_OF_STATIC_LIST) {
3620 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3623 if (info->type==RBH)
3624 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3626 // make sure the info pointer is into text space
3628 /* Take this object *off* the static_objects list,
3629 * and put it on the scavenged_static_objects list.
3631 static_objects = STATIC_LINK(info,p);
3632 STATIC_LINK(info,p) = scavenged_static_objects;
3633 scavenged_static_objects = p;
3635 switch (info -> type) {
3639 StgInd *ind = (StgInd *)p;
3640 ind->indirectee = evacuate(ind->indirectee);
3642 /* might fail to evacuate it, in which case we have to pop it
3643 * back on the mutable list (and take it off the
3644 * scavenged_static list because the static link and mut link
3645 * pointers are one and the same).
3647 if (failed_to_evac) {
3648 failed_to_evac = rtsFalse;
3649 scavenged_static_objects = IND_STATIC_LINK(p);
3650 ((StgMutClosure *)ind)->mut_link = oldest_gen->mut_once_list;
3651 oldest_gen->mut_once_list = (StgMutClosure *)ind;
3657 scavenge_thunk_srt(info);
3661 scavenge_fun_srt(info);
3668 next = (P_)p->payload + info->layout.payload.ptrs;
3669 // evacuate the pointers
3670 for (q = (P_)p->payload; q < next; q++) {
3671 (StgClosure *)*q = evacuate((StgClosure *)*q);
3677 barf("scavenge_static: strange closure %d", (int)(info->type));
3680 ASSERT(failed_to_evac == rtsFalse);
3682 /* get the next static object from the list. Remember, there might
3683 * be more stuff on this list now that we've done some evacuating!
3684 * (static_objects is a global)
3690 /* -----------------------------------------------------------------------------
3691 scavenge a chunk of memory described by a bitmap
3692 -------------------------------------------------------------------------- */
3695 scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
3701 bitmap = large_bitmap->bitmap[b];
3702 for (i = 0; i < size; ) {
3703 if ((bitmap & 1) == 0) {
3704 (StgClosure *)*p = evacuate((StgClosure *)*p);
3708 if (i % BITS_IN(W_) == 0) {
3710 bitmap = large_bitmap->bitmap[b];
3712 bitmap = bitmap >> 1;
3717 STATIC_INLINE StgPtr
3718 scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap)
3721 if ((bitmap & 1) == 0) {
3722 (StgClosure *)*p = evacuate((StgClosure *)*p);
3725 bitmap = bitmap >> 1;
3731 /* -----------------------------------------------------------------------------
3732 scavenge_stack walks over a section of stack and evacuates all the
3733 objects pointed to by it. We can use the same code for walking
3734 AP_STACK_UPDs, since these are just sections of copied stack.
3735 -------------------------------------------------------------------------- */
3739 scavenge_stack(StgPtr p, StgPtr stack_end)
3741 const StgRetInfoTable* info;
3745 //IF_DEBUG(sanity, debugBelch(" scavenging stack between %p and %p", p, stack_end));
3748 * Each time around this loop, we are looking at a chunk of stack
3749 * that starts with an activation record.
3752 while (p < stack_end) {
3753 info = get_ret_itbl((StgClosure *)p);
3755 switch (info->i.type) {
3758 ((StgUpdateFrame *)p)->updatee
3759 = evacuate(((StgUpdateFrame *)p)->updatee);
3760 p += sizeofW(StgUpdateFrame);
3763 // small bitmap (< 32 entries, or 64 on a 64-bit machine)
3768 bitmap = BITMAP_BITS(info->i.layout.bitmap);
3769 size = BITMAP_SIZE(info->i.layout.bitmap);
3770 // NOTE: the payload starts immediately after the info-ptr, we
3771 // don't have an StgHeader in the same sense as a heap closure.
3773 p = scavenge_small_bitmap(p, size, bitmap);
3776 scavenge_srt((StgClosure **)info->srt, info->i.srt_bitmap);
3784 (StgClosure *)*p = evacuate((StgClosure *)*p);
3787 size = BCO_BITMAP_SIZE(bco);
3788 scavenge_large_bitmap(p, BCO_BITMAP(bco), size);
3793 // large bitmap (> 32 entries, or > 64 on a 64-bit machine)
3799 size = info->i.layout.large_bitmap->size;
3801 scavenge_large_bitmap(p, info->i.layout.large_bitmap, size);
3803 // and don't forget to follow the SRT
3807 // Dynamic bitmap: the mask is stored on the stack, and
3808 // there are a number of non-pointers followed by a number
3809 // of pointers above the bitmapped area. (see StgMacros.h,
3814 dyn = ((StgRetDyn *)p)->liveness;
3816 // traverse the bitmap first
3817 bitmap = RET_DYN_LIVENESS(dyn);
3818 p = (P_)&((StgRetDyn *)p)->payload[0];
3819 size = RET_DYN_BITMAP_SIZE;
3820 p = scavenge_small_bitmap(p, size, bitmap);
3822 // skip over the non-ptr words
3823 p += RET_DYN_NONPTRS(dyn) + RET_DYN_NONPTR_REGS_SIZE;
3825 // follow the ptr words
3826 for (size = RET_DYN_PTRS(dyn); size > 0; size--) {
3827 (StgClosure *)*p = evacuate((StgClosure *)*p);
3835 StgRetFun *ret_fun = (StgRetFun *)p;
3836 StgFunInfoTable *fun_info;
3838 ret_fun->fun = evacuate(ret_fun->fun);
3839 fun_info = get_fun_itbl(ret_fun->fun);
3840 p = scavenge_arg_block(fun_info, ret_fun->payload);
3845 barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->i.type));
3850 /*-----------------------------------------------------------------------------
3851 scavenge the large object list.
3853 evac_gen set by caller; similar games played with evac_gen as with
3854 scavenge() - see comment at the top of scavenge(). Most large
3855 objects are (repeatedly) mutable, so most of the time evac_gen will
3857 --------------------------------------------------------------------------- */
3860 scavenge_large(step *stp)
3865 bd = stp->new_large_objects;
3867 for (; bd != NULL; bd = stp->new_large_objects) {
3869 /* take this object *off* the large objects list and put it on
3870 * the scavenged large objects list. This is so that we can
3871 * treat new_large_objects as a stack and push new objects on
3872 * the front when evacuating.
3874 stp->new_large_objects = bd->link;
3875 dbl_link_onto(bd, &stp->scavenged_large_objects);
3877 // update the block count in this step.
3878 stp->n_scavenged_large_blocks += bd->blocks;
3881 if (scavenge_one(p)) {
3882 mkMutCons((StgClosure *)p, stp->gen);
3887 /* -----------------------------------------------------------------------------
3888 Initialising the static object & mutable lists
3889 -------------------------------------------------------------------------- */
3892 zero_static_object_list(StgClosure* first_static)
3896 const StgInfoTable *info;
3898 for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
3900 link = STATIC_LINK(info, p);
3901 STATIC_LINK(info,p) = NULL;
3905 /* This function is only needed because we share the mutable link
3906 * field with the static link field in an IND_STATIC, so we have to
3907 * zero the mut_link field before doing a major GC, which needs the
3908 * static link field.
3910 * It doesn't do any harm to zero all the mutable link fields on the
3915 zero_mutable_list( StgMutClosure *first )
3917 StgMutClosure *next, *c;
3919 for (c = first; c != END_MUT_LIST; c = next) {
3925 /* -----------------------------------------------------------------------------
3927 -------------------------------------------------------------------------- */
3934 for (c = (StgIndStatic *)caf_list; c != NULL;
3935 c = (StgIndStatic *)c->static_link)
3937 SET_INFO(c, c->saved_info);
3938 c->saved_info = NULL;
3939 // could, but not necessary: c->static_link = NULL;
3945 markCAFs( evac_fn evac )
3949 for (c = (StgIndStatic *)caf_list; c != NULL;
3950 c = (StgIndStatic *)c->static_link)
3952 evac(&c->indirectee);
3956 /* -----------------------------------------------------------------------------
3957 Sanity code for CAF garbage collection.
3959 With DEBUG turned on, we manage a CAF list in addition to the SRT
3960 mechanism. After GC, we run down the CAF list and blackhole any
3961 CAFs which have been garbage collected. This means we get an error
3962 whenever the program tries to enter a garbage collected CAF.
3964 Any garbage collected CAFs are taken off the CAF list at the same
3966 -------------------------------------------------------------------------- */
3968 #if 0 && defined(DEBUG)
3975 const StgInfoTable *info;
3986 ASSERT(info->type == IND_STATIC);
3988 if (STATIC_LINK(info,p) == NULL) {
3989 IF_DEBUG(gccafs, debugBelch("CAF gc'd at 0x%04lx", (long)p));
3991 SET_INFO(p,&stg_BLACKHOLE_info);
3992 p = STATIC_LINK2(info,p);
3996 pp = &STATIC_LINK2(info,p);
4003 // debugBelch("%d CAFs live", i);
4008 /* -----------------------------------------------------------------------------
4011 Whenever a thread returns to the scheduler after possibly doing
4012 some work, we have to run down the stack and black-hole all the
4013 closures referred to by update frames.
4014 -------------------------------------------------------------------------- */
4017 threadLazyBlackHole(StgTSO *tso)
4020 StgRetInfoTable *info;
4021 StgBlockingQueue *bh;
4024 stack_end = &tso->stack[tso->stack_size];
4026 frame = (StgClosure *)tso->sp;
4029 info = get_ret_itbl(frame);
4031 switch (info->i.type) {
4034 bh = (StgBlockingQueue *)((StgUpdateFrame *)frame)->updatee;
4036 /* if the thunk is already blackholed, it means we've also
4037 * already blackholed the rest of the thunks on this stack,
4038 * so we can stop early.
4040 * The blackhole made for a CAF is a CAF_BLACKHOLE, so they
4041 * don't interfere with this optimisation.
4043 if (bh->header.info == &stg_BLACKHOLE_info) {
4047 if (bh->header.info != &stg_BLACKHOLE_BQ_info &&
4048 bh->header.info != &stg_CAF_BLACKHOLE_info) {
4049 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4050 debugBelch("Unexpected lazy BHing required at 0x%04x",(int)bh);
4054 // We pretend that bh is now dead.
4055 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4057 SET_INFO(bh,&stg_BLACKHOLE_info);
4059 // We pretend that bh has just been created.
4060 LDV_RECORD_CREATE(bh);
4063 frame = (StgClosure *) ((StgUpdateFrame *)frame + 1);
4069 // normal stack frames; do nothing except advance the pointer
4071 (StgPtr)frame += stack_frame_sizeW(frame);
4077 /* -----------------------------------------------------------------------------
4080 * Code largely pinched from old RTS, then hacked to bits. We also do
4081 * lazy black holing here.
4083 * -------------------------------------------------------------------------- */
4085 struct stack_gap { StgWord gap_size; struct stack_gap *next_gap; };
4088 threadSqueezeStack(StgTSO *tso)
4091 rtsBool prev_was_update_frame;
4092 StgClosure *updatee = NULL;
4094 StgRetInfoTable *info;
4095 StgWord current_gap_size;
4096 struct stack_gap *gap;
4099 // Traverse the stack upwards, replacing adjacent update frames
4100 // with a single update frame and a "stack gap". A stack gap
4101 // contains two values: the size of the gap, and the distance
4102 // to the next gap (or the stack top).
4104 bottom = &(tso->stack[tso->stack_size]);
4108 ASSERT(frame < bottom);
4110 prev_was_update_frame = rtsFalse;
4111 current_gap_size = 0;
4112 gap = (struct stack_gap *) (tso->sp - sizeofW(StgUpdateFrame));
4114 while (frame < bottom) {
4116 info = get_ret_itbl((StgClosure *)frame);
4117 switch (info->i.type) {
4121 StgUpdateFrame *upd = (StgUpdateFrame *)frame;
4123 if (upd->updatee->header.info == &stg_BLACKHOLE_info) {
4125 // found a BLACKHOLE'd update frame; we've been here
4126 // before, in a previous GC, so just break out.
4128 // Mark the end of the gap, if we're in one.
4129 if (current_gap_size != 0) {
4130 gap = (struct stack_gap *)(frame-sizeofW(StgUpdateFrame));
4133 frame += sizeofW(StgUpdateFrame);
4134 goto done_traversing;
4137 if (prev_was_update_frame) {
4139 TICK_UPD_SQUEEZED();
4140 /* wasn't there something about update squeezing and ticky to be
4141 * sorted out? oh yes: we aren't counting each enter properly
4142 * in this case. See the log somewhere. KSW 1999-04-21
4144 * Check two things: that the two update frames don't point to
4145 * the same object, and that the updatee_bypass isn't already an
4146 * indirection. Both of these cases only happen when we're in a
4147 * block hole-style loop (and there are multiple update frames
4148 * on the stack pointing to the same closure), but they can both
4149 * screw us up if we don't check.
4151 if (upd->updatee != updatee && !closure_IND(upd->updatee)) {
4152 // this wakes the threads up
4153 UPD_IND_NOLOCK(upd->updatee, updatee);
4156 // now mark this update frame as a stack gap. The gap
4157 // marker resides in the bottom-most update frame of
4158 // the series of adjacent frames, and covers all the
4159 // frames in this series.
4160 current_gap_size += sizeofW(StgUpdateFrame);
4161 ((struct stack_gap *)frame)->gap_size = current_gap_size;
4162 ((struct stack_gap *)frame)->next_gap = gap;
4164 frame += sizeofW(StgUpdateFrame);
4168 // single update frame, or the topmost update frame in a series
4170 StgBlockingQueue *bh = (StgBlockingQueue *)upd->updatee;
4172 // Do lazy black-holing
4173 if (bh->header.info != &stg_BLACKHOLE_info &&
4174 bh->header.info != &stg_BLACKHOLE_BQ_info &&
4175 bh->header.info != &stg_CAF_BLACKHOLE_info) {
4176 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4177 debugBelch("Unexpected lazy BHing required at 0x%04x",(int)bh);
4180 /* zero out the slop so that the sanity checker can tell
4181 * where the next closure is.
4184 StgInfoTable *bh_info = get_itbl(bh);
4185 nat np = bh_info->layout.payload.ptrs,
4186 nw = bh_info->layout.payload.nptrs, i;
4187 /* don't zero out slop for a THUNK_SELECTOR,
4188 * because its layout info is used for a
4189 * different purpose, and it's exactly the
4190 * same size as a BLACKHOLE in any case.
4192 if (bh_info->type != THUNK_SELECTOR) {
4193 for (i = np; i < np + nw; i++) {
4194 ((StgClosure *)bh)->payload[i] = 0;
4200 // We pretend that bh is now dead.
4201 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4203 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
4204 SET_INFO(bh,&stg_BLACKHOLE_info);
4206 // We pretend that bh has just been created.
4207 LDV_RECORD_CREATE(bh);
4210 prev_was_update_frame = rtsTrue;
4211 updatee = upd->updatee;
4212 frame += sizeofW(StgUpdateFrame);
4218 prev_was_update_frame = rtsFalse;
4220 // we're not in a gap... check whether this is the end of a gap
4221 // (an update frame can't be the end of a gap).
4222 if (current_gap_size != 0) {
4223 gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
4225 current_gap_size = 0;
4227 frame += stack_frame_sizeW((StgClosure *)frame);
4234 // Now we have a stack with gaps in it, and we have to walk down
4235 // shoving the stack up to fill in the gaps. A diagram might
4239 // | ********* | <- sp
4243 // | stack_gap | <- gap | chunk_size
4245 // | ......... | <- gap_end v
4251 // 'sp' points the the current top-of-stack
4252 // 'gap' points to the stack_gap structure inside the gap
4253 // ***** indicates real stack data
4254 // ..... indicates gap
4255 // <empty> indicates unused
4259 void *gap_start, *next_gap_start, *gap_end;
4262 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4263 sp = next_gap_start;
4265 while ((StgPtr)gap > tso->sp) {
4267 // we're working in *bytes* now...
4268 gap_start = next_gap_start;
4269 gap_end = (void*) ((unsigned char*)gap_start - gap->gap_size * sizeof(W_));
4271 gap = gap->next_gap;
4272 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4274 chunk_size = (unsigned char*)gap_end - (unsigned char*)next_gap_start;
4275 (unsigned char*)sp -= chunk_size;
4276 memmove(sp, next_gap_start, chunk_size);
4279 tso->sp = (StgPtr)sp;
4283 /* -----------------------------------------------------------------------------
4286 * We have to prepare for GC - this means doing lazy black holing
4287 * here. We also take the opportunity to do stack squeezing if it's
4289 * -------------------------------------------------------------------------- */
4291 threadPaused(StgTSO *tso)
4293 if ( RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue )
4294 threadSqueezeStack(tso); // does black holing too
4296 threadLazyBlackHole(tso);
4299 /* -----------------------------------------------------------------------------
4301 * -------------------------------------------------------------------------- */
4305 printMutOnceList(generation *gen)
4307 StgMutClosure *p, *next;
4309 p = gen->mut_once_list;
4312 debugBelch("@@ Mut once list %p: ", gen->mut_once_list);
4313 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
4314 debugBelch("%p (%s), ",
4315 p, info_type((StgClosure *)p));
4321 printMutableList(generation *gen)
4323 StgMutClosure *p, *next;
4328 debugBelch("@@ Mutable list %p: ", gen->mut_list);
4329 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
4330 debugBelch("%p (%s), ",
4331 p, info_type((StgClosure *)p));
4336 STATIC_INLINE rtsBool
4337 maybeLarge(StgClosure *closure)
4339 StgInfoTable *info = get_itbl(closure);
4341 /* closure types that may be found on the new_large_objects list;
4342 see scavenge_large */
4343 return (info->type == MUT_ARR_PTRS ||
4344 info->type == MUT_ARR_PTRS_FROZEN ||
4345 info->type == TSO ||
4346 info->type == ARR_WORDS);