1 /* -----------------------------------------------------------------------------
2 * $Id: GC.c,v 1.163 2003/11/12 17:49:07 sof Exp $
4 * (c) The GHC Team 1998-2003
6 * Generational garbage collector
8 * ---------------------------------------------------------------------------*/
10 #include "PosixSource.h"
16 #include "StoragePriv.h"
19 #include "SchedAPI.h" // for ReverCAFs prototype
21 #include "BlockAlloc.h"
26 #include "StablePriv.h"
28 #include "ParTicky.h" // ToDo: move into Rts.h
29 #include "GCCompact.h"
31 #if defined(GRAN) || defined(PAR)
32 # include "GranSimRts.h"
33 # include "ParallelRts.h"
37 # include "ParallelDebug.h"
42 #if defined(RTS_GTK_FRONTPANEL)
43 #include "FrontPanel.h"
46 #include "RetainerProfile.h"
47 #include "LdvProfile.h"
51 /* STATIC OBJECT LIST.
54 * We maintain a linked list of static objects that are still live.
55 * The requirements for this list are:
57 * - we need to scan the list while adding to it, in order to
58 * scavenge all the static objects (in the same way that
59 * breadth-first scavenging works for dynamic objects).
61 * - we need to be able to tell whether an object is already on
62 * the list, to break loops.
64 * Each static object has a "static link field", which we use for
65 * linking objects on to the list. We use a stack-type list, consing
66 * objects on the front as they are added (this means that the
67 * scavenge phase is depth-first, not breadth-first, but that
70 * A separate list is kept for objects that have been scavenged
71 * already - this is so that we can zero all the marks afterwards.
73 * An object is on the list if its static link field is non-zero; this
74 * means that we have to mark the end of the list with '1', not NULL.
76 * Extra notes for generational GC:
78 * Each generation has a static object list associated with it. When
79 * collecting generations up to N, we treat the static object lists
80 * from generations > N as roots.
82 * We build up a static object list while collecting generations 0..N,
83 * which is then appended to the static object list of generation N+1.
85 static StgClosure* static_objects; // live static objects
86 StgClosure* scavenged_static_objects; // static objects scavenged so far
88 /* N is the oldest generation being collected, where the generations
89 * are numbered starting at 0. A major GC (indicated by the major_gc
90 * flag) is when we're collecting all generations. We only attempt to
91 * deal with static objects and GC CAFs when doing a major GC.
94 static rtsBool major_gc;
96 /* Youngest generation that objects should be evacuated to in
97 * evacuate(). (Logically an argument to evacuate, but it's static
98 * a lot of the time so we optimise it into a global variable).
104 StgWeak *old_weak_ptr_list; // also pending finaliser list
106 /* Which stage of processing various kinds of weak pointer are we at?
107 * (see traverse_weak_ptr_list() below for discussion).
109 typedef enum { WeakPtrs, WeakThreads, WeakDone } WeakStage;
110 static WeakStage weak_stage;
112 /* List of all threads during GC
114 static StgTSO *old_all_threads;
115 StgTSO *resurrected_threads;
117 /* Flag indicating failure to evacuate an object to the desired
120 static rtsBool failed_to_evac;
122 /* Old to-space (used for two-space collector only)
124 static bdescr *old_to_blocks;
126 /* Data used for allocation area sizing.
128 static lnat new_blocks; // blocks allocated during this GC
129 static lnat g0s0_pcnt_kept = 30; // percentage of g0s0 live at last minor GC
131 /* Used to avoid long recursion due to selector thunks
133 static lnat thunk_selector_depth = 0;
134 #define MAX_THUNK_SELECTOR_DEPTH 8
136 /* -----------------------------------------------------------------------------
137 Static function declarations
138 -------------------------------------------------------------------------- */
140 static bdescr * gc_alloc_block ( step *stp );
141 static void mark_root ( StgClosure **root );
143 // Use a register argument for evacuate, if available.
145 static StgClosure * evacuate (StgClosure *q) __attribute__((regparm(1)));
147 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, belch("@@ 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, belch("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);
459 /* make sure the older generations have at least one block to
460 * allocate into (this makes things easier for copy(), see below).
462 for (g = N+1; g < RtsFlags.GcFlags.generations; g++) {
463 for (s = 0; s < generations[g].n_steps; s++) {
464 stp = &generations[g].steps[s];
465 if (stp->hp_bd == NULL) {
466 ASSERT(stp->blocks == NULL);
467 bd = gc_alloc_block(stp);
471 /* Set the scan pointer for older generations: remember we
472 * still have to scavenge objects that have been promoted. */
474 stp->scan_bd = stp->hp_bd;
475 stp->to_blocks = NULL;
476 stp->n_to_blocks = 0;
477 stp->new_large_objects = NULL;
478 stp->scavenged_large_objects = NULL;
479 stp->n_scavenged_large_blocks = 0;
483 /* Allocate a mark stack if we're doing a major collection.
486 mark_stack_bdescr = allocGroup(MARK_STACK_BLOCKS);
487 mark_stack = (StgPtr *)mark_stack_bdescr->start;
488 mark_sp = mark_stack;
489 mark_splim = mark_stack + (MARK_STACK_BLOCKS * BLOCK_SIZE_W);
491 mark_stack_bdescr = NULL;
494 /* -----------------------------------------------------------------------
495 * follow all the roots that we know about:
496 * - mutable lists from each generation > N
497 * we want to *scavenge* these roots, not evacuate them: they're not
498 * going to move in this GC.
499 * Also: do them in reverse generation order. This is because we
500 * often want to promote objects that are pointed to by older
501 * generations early, so we don't have to repeatedly copy them.
502 * Doing the generations in reverse order ensures that we don't end
503 * up in the situation where we want to evac an object to gen 3 and
504 * it has already been evaced to gen 2.
508 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
509 generations[g].saved_mut_list = generations[g].mut_list;
510 generations[g].mut_list = END_MUT_LIST;
513 // Do the mut-once lists first
514 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
515 IF_PAR_DEBUG(verbose,
516 printMutOnceList(&generations[g]));
517 scavenge_mut_once_list(&generations[g]);
519 for (st = generations[g].n_steps-1; st >= 0; st--) {
520 scavenge(&generations[g].steps[st]);
524 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
525 IF_PAR_DEBUG(verbose,
526 printMutableList(&generations[g]));
527 scavenge_mutable_list(&generations[g]);
529 for (st = generations[g].n_steps-1; st >= 0; st--) {
530 scavenge(&generations[g].steps[st]);
535 /* follow roots from the CAF list (used by GHCi)
540 /* follow all the roots that the application knows about.
543 get_roots(mark_root);
546 /* And don't forget to mark the TSO if we got here direct from
548 /* Not needed in a seq version?
550 CurrentTSO = (StgTSO *)MarkRoot((StgClosure *)CurrentTSO);
554 // Mark the entries in the GALA table of the parallel system
555 markLocalGAs(major_gc);
556 // Mark all entries on the list of pending fetches
557 markPendingFetches(major_gc);
560 /* Mark the weak pointer list, and prepare to detect dead weak
563 mark_weak_ptr_list(&weak_ptr_list);
564 old_weak_ptr_list = weak_ptr_list;
565 weak_ptr_list = NULL;
566 weak_stage = WeakPtrs;
568 /* The all_threads list is like the weak_ptr_list.
569 * See traverse_weak_ptr_list() for the details.
571 old_all_threads = all_threads;
572 all_threads = END_TSO_QUEUE;
573 resurrected_threads = END_TSO_QUEUE;
575 /* Mark the stable pointer table.
577 markStablePtrTable(mark_root);
581 /* ToDo: To fix the caf leak, we need to make the commented out
582 * parts of this code do something sensible - as described in
585 extern void markHugsObjects(void);
590 /* -------------------------------------------------------------------------
591 * Repeatedly scavenge all the areas we know about until there's no
592 * more scavenging to be done.
599 // scavenge static objects
600 if (major_gc && static_objects != END_OF_STATIC_LIST) {
601 IF_DEBUG(sanity, checkStaticObjects(static_objects));
605 /* When scavenging the older generations: Objects may have been
606 * evacuated from generations <= N into older generations, and we
607 * need to scavenge these objects. We're going to try to ensure that
608 * any evacuations that occur move the objects into at least the
609 * same generation as the object being scavenged, otherwise we
610 * have to create new entries on the mutable list for the older
614 // scavenge each step in generations 0..maxgen
620 // scavenge objects in compacted generation
621 if (mark_stack_overflowed || oldgen_scan_bd != NULL ||
622 (mark_stack_bdescr != NULL && !mark_stack_empty())) {
623 scavenge_mark_stack();
627 for (gen = RtsFlags.GcFlags.generations; --gen >= 0; ) {
628 for (st = generations[gen].n_steps; --st >= 0; ) {
629 if (gen == 0 && st == 0 && RtsFlags.GcFlags.generations > 1) {
632 stp = &generations[gen].steps[st];
634 if (stp->hp_bd != stp->scan_bd || stp->scan < stp->hp) {
639 if (stp->new_large_objects != NULL) {
648 if (flag) { goto loop; }
650 // must be last... invariant is that everything is fully
651 // scavenged at this point.
652 if (traverse_weak_ptr_list()) { // returns rtsTrue if evaced something
657 /* Update the pointers from the "main thread" list - these are
658 * treated as weak pointers because we want to allow a main thread
659 * to get a BlockedOnDeadMVar exception in the same way as any other
660 * thread. Note that the threads should all have been retained by
661 * GC by virtue of being on the all_threads list, we're just
662 * updating pointers here.
667 for (m = main_threads; m != NULL; m = m->link) {
668 tso = (StgTSO *) isAlive((StgClosure *)m->tso);
670 barf("main thread has been GC'd");
677 // Reconstruct the Global Address tables used in GUM
678 rebuildGAtables(major_gc);
679 IF_DEBUG(sanity, checkLAGAtable(rtsTrue/*check closures, too*/));
682 // Now see which stable names are still alive.
685 // Tidy the end of the to-space chains
686 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
687 for (s = 0; s < generations[g].n_steps; s++) {
688 stp = &generations[g].steps[s];
689 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
690 ASSERT(Bdescr(stp->hp) == stp->hp_bd);
691 stp->hp_bd->free = stp->hp;
697 // We call processHeapClosureForDead() on every closure destroyed during
698 // the current garbage collection, so we invoke LdvCensusForDead().
699 if (RtsFlags.ProfFlags.doHeapProfile == HEAP_BY_LDV
700 || RtsFlags.ProfFlags.bioSelector != NULL)
704 // NO MORE EVACUATION AFTER THIS POINT!
705 // Finally: compaction of the oldest generation.
706 if (major_gc && oldest_gen->steps[0].is_compacted) {
707 // save number of blocks for stats
708 oldgen_saved_blocks = oldest_gen->steps[0].n_blocks;
712 IF_DEBUG(sanity, checkGlobalTSOList(rtsFalse));
714 /* run through all the generations/steps and tidy up
716 copied = new_blocks * BLOCK_SIZE_W;
717 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
720 generations[g].collections++; // for stats
723 for (s = 0; s < generations[g].n_steps; s++) {
725 stp = &generations[g].steps[s];
727 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
728 // stats information: how much we copied
730 copied -= stp->hp_bd->start + BLOCK_SIZE_W -
735 // for generations we collected...
738 // rough calculation of garbage collected, for stats output
739 if (stp->is_compacted) {
740 collected += (oldgen_saved_blocks - stp->n_blocks) * BLOCK_SIZE_W;
742 collected += stp->n_blocks * BLOCK_SIZE_W;
745 /* free old memory and shift to-space into from-space for all
746 * the collected steps (except the allocation area). These
747 * freed blocks will probaby be quickly recycled.
749 if (!(g == 0 && s == 0)) {
750 if (stp->is_compacted) {
751 // for a compacted step, just shift the new to-space
752 // onto the front of the now-compacted existing blocks.
753 for (bd = stp->to_blocks; bd != NULL; bd = bd->link) {
754 bd->flags &= ~BF_EVACUATED; // now from-space
756 // tack the new blocks on the end of the existing blocks
757 if (stp->blocks == NULL) {
758 stp->blocks = stp->to_blocks;
760 for (bd = stp->blocks; bd != NULL; bd = next) {
763 bd->link = stp->to_blocks;
767 // add the new blocks to the block tally
768 stp->n_blocks += stp->n_to_blocks;
770 freeChain(stp->blocks);
771 stp->blocks = stp->to_blocks;
772 stp->n_blocks = stp->n_to_blocks;
773 for (bd = stp->blocks; bd != NULL; bd = bd->link) {
774 bd->flags &= ~BF_EVACUATED; // now from-space
777 stp->to_blocks = NULL;
778 stp->n_to_blocks = 0;
781 /* LARGE OBJECTS. The current live large objects are chained on
782 * scavenged_large, having been moved during garbage
783 * collection from large_objects. Any objects left on
784 * large_objects list are therefore dead, so we free them here.
786 for (bd = stp->large_objects; bd != NULL; bd = next) {
792 // update the count of blocks used by large objects
793 for (bd = stp->scavenged_large_objects; bd != NULL; bd = bd->link) {
794 bd->flags &= ~BF_EVACUATED;
796 stp->large_objects = stp->scavenged_large_objects;
797 stp->n_large_blocks = stp->n_scavenged_large_blocks;
800 // for older generations...
802 /* For older generations, we need to append the
803 * scavenged_large_object list (i.e. large objects that have been
804 * promoted during this GC) to the large_object list for that step.
806 for (bd = stp->scavenged_large_objects; bd; bd = next) {
808 bd->flags &= ~BF_EVACUATED;
809 dbl_link_onto(bd, &stp->large_objects);
812 // add the new blocks we promoted during this GC
813 stp->n_blocks += stp->n_to_blocks;
814 stp->n_to_blocks = 0;
815 stp->n_large_blocks += stp->n_scavenged_large_blocks;
820 /* Reset the sizes of the older generations when we do a major
823 * CURRENT STRATEGY: make all generations except zero the same size.
824 * We have to stay within the maximum heap size, and leave a certain
825 * percentage of the maximum heap size available to allocate into.
827 if (major_gc && RtsFlags.GcFlags.generations > 1) {
828 nat live, size, min_alloc;
829 nat max = RtsFlags.GcFlags.maxHeapSize;
830 nat gens = RtsFlags.GcFlags.generations;
832 // live in the oldest generations
833 live = oldest_gen->steps[0].n_blocks +
834 oldest_gen->steps[0].n_large_blocks;
836 // default max size for all generations except zero
837 size = stg_max(live * RtsFlags.GcFlags.oldGenFactor,
838 RtsFlags.GcFlags.minOldGenSize);
840 // minimum size for generation zero
841 min_alloc = stg_max((RtsFlags.GcFlags.pcFreeHeap * max) / 200,
842 RtsFlags.GcFlags.minAllocAreaSize);
844 // Auto-enable compaction when the residency reaches a
845 // certain percentage of the maximum heap size (default: 30%).
846 if (RtsFlags.GcFlags.generations > 1 &&
847 (RtsFlags.GcFlags.compact ||
849 oldest_gen->steps[0].n_blocks >
850 (RtsFlags.GcFlags.compactThreshold * max) / 100))) {
851 oldest_gen->steps[0].is_compacted = 1;
852 // fprintf(stderr,"compaction: on\n", live);
854 oldest_gen->steps[0].is_compacted = 0;
855 // fprintf(stderr,"compaction: off\n", live);
858 // if we're going to go over the maximum heap size, reduce the
859 // size of the generations accordingly. The calculation is
860 // different if compaction is turned on, because we don't need
861 // to double the space required to collect the old generation.
864 // this test is necessary to ensure that the calculations
865 // below don't have any negative results - we're working
866 // with unsigned values here.
867 if (max < min_alloc) {
871 if (oldest_gen->steps[0].is_compacted) {
872 if ( (size + (size - 1) * (gens - 2) * 2) + min_alloc > max ) {
873 size = (max - min_alloc) / ((gens - 1) * 2 - 1);
876 if ( (size * (gens - 1) * 2) + min_alloc > max ) {
877 size = (max - min_alloc) / ((gens - 1) * 2);
887 fprintf(stderr,"live: %d, min_alloc: %d, size : %d, max = %d\n", live,
888 min_alloc, size, max);
891 for (g = 0; g < gens; g++) {
892 generations[g].max_blocks = size;
896 // Guess the amount of live data for stats.
899 /* Free the small objects allocated via allocate(), since this will
900 * all have been copied into G0S1 now.
902 if (small_alloc_list != NULL) {
903 freeChain(small_alloc_list);
905 small_alloc_list = NULL;
909 alloc_blocks_lim = RtsFlags.GcFlags.minAllocAreaSize;
911 // Start a new pinned_object_block
912 pinned_object_block = NULL;
914 /* Free the mark stack.
916 if (mark_stack_bdescr != NULL) {
917 freeGroup(mark_stack_bdescr);
922 for (g = 0; g <= N; g++) {
923 for (s = 0; s < generations[g].n_steps; s++) {
924 stp = &generations[g].steps[s];
925 if (stp->is_compacted && stp->bitmap != NULL) {
926 freeGroup(stp->bitmap);
931 /* Two-space collector:
932 * Free the old to-space, and estimate the amount of live data.
934 if (RtsFlags.GcFlags.generations == 1) {
937 if (old_to_blocks != NULL) {
938 freeChain(old_to_blocks);
940 for (bd = g0s0->to_blocks; bd != NULL; bd = bd->link) {
941 bd->flags = 0; // now from-space
944 /* For a two-space collector, we need to resize the nursery. */
946 /* set up a new nursery. Allocate a nursery size based on a
947 * function of the amount of live data (by default a factor of 2)
948 * Use the blocks from the old nursery if possible, freeing up any
951 * If we get near the maximum heap size, then adjust our nursery
952 * size accordingly. If the nursery is the same size as the live
953 * data (L), then we need 3L bytes. We can reduce the size of the
954 * nursery to bring the required memory down near 2L bytes.
956 * A normal 2-space collector would need 4L bytes to give the same
957 * performance we get from 3L bytes, reducing to the same
958 * performance at 2L bytes.
960 blocks = g0s0->n_to_blocks;
962 if ( RtsFlags.GcFlags.maxHeapSize != 0 &&
963 blocks * RtsFlags.GcFlags.oldGenFactor * 2 >
964 RtsFlags.GcFlags.maxHeapSize ) {
965 long adjusted_blocks; // signed on purpose
968 adjusted_blocks = (RtsFlags.GcFlags.maxHeapSize - 2 * blocks);
969 IF_DEBUG(gc, belch("@@ Near maximum heap size of 0x%x blocks, blocks = %d, adjusted to %ld", RtsFlags.GcFlags.maxHeapSize, blocks, adjusted_blocks));
970 pc_free = adjusted_blocks * 100 / RtsFlags.GcFlags.maxHeapSize;
971 if (pc_free < RtsFlags.GcFlags.pcFreeHeap) /* might even be < 0 */ {
974 blocks = adjusted_blocks;
977 blocks *= RtsFlags.GcFlags.oldGenFactor;
978 if (blocks < RtsFlags.GcFlags.minAllocAreaSize) {
979 blocks = RtsFlags.GcFlags.minAllocAreaSize;
982 resizeNursery(blocks);
985 /* Generational collector:
986 * If the user has given us a suggested heap size, adjust our
987 * allocation area to make best use of the memory available.
990 if (RtsFlags.GcFlags.heapSizeSuggestion) {
992 nat needed = calcNeeded(); // approx blocks needed at next GC
994 /* Guess how much will be live in generation 0 step 0 next time.
995 * A good approximation is obtained by finding the
996 * percentage of g0s0 that was live at the last minor GC.
999 g0s0_pcnt_kept = (new_blocks * 100) / g0s0->n_blocks;
1002 /* Estimate a size for the allocation area based on the
1003 * information available. We might end up going slightly under
1004 * or over the suggested heap size, but we should be pretty
1007 * Formula: suggested - needed
1008 * ----------------------------
1009 * 1 + g0s0_pcnt_kept/100
1011 * where 'needed' is the amount of memory needed at the next
1012 * collection for collecting all steps except g0s0.
1015 (((long)RtsFlags.GcFlags.heapSizeSuggestion - (long)needed) * 100) /
1016 (100 + (long)g0s0_pcnt_kept);
1018 if (blocks < (long)RtsFlags.GcFlags.minAllocAreaSize) {
1019 blocks = RtsFlags.GcFlags.minAllocAreaSize;
1022 resizeNursery((nat)blocks);
1025 // we might have added extra large blocks to the nursery, so
1026 // resize back to minAllocAreaSize again.
1027 resizeNursery(RtsFlags.GcFlags.minAllocAreaSize);
1031 // mark the garbage collected CAFs as dead
1032 #if 0 && defined(DEBUG) // doesn't work at the moment
1033 if (major_gc) { gcCAFs(); }
1037 // resetStaticObjectForRetainerProfiling() must be called before
1039 resetStaticObjectForRetainerProfiling();
1042 // zero the scavenged static object list
1044 zero_static_object_list(scavenged_static_objects);
1047 // Reset the nursery
1050 RELEASE_LOCK(&sched_mutex);
1052 // start any pending finalizers
1053 scheduleFinalizers(old_weak_ptr_list);
1055 // send exceptions to any threads which were about to die
1056 resurrectThreads(resurrected_threads);
1058 ACQUIRE_LOCK(&sched_mutex);
1060 // Update the stable pointer hash table.
1061 updateStablePtrTable(major_gc);
1063 // check sanity after GC
1064 IF_DEBUG(sanity, checkSanity());
1066 // extra GC trace info
1067 IF_DEBUG(gc, statDescribeGens());
1070 // symbol-table based profiling
1071 /* heapCensus(to_blocks); */ /* ToDo */
1074 // restore enclosing cost centre
1079 // check for memory leaks if sanity checking is on
1080 IF_DEBUG(sanity, memInventory());
1082 #ifdef RTS_GTK_FRONTPANEL
1083 if (RtsFlags.GcFlags.frontpanel) {
1084 updateFrontPanelAfterGC( N, live );
1088 // ok, GC over: tell the stats department what happened.
1089 stat_endGC(allocated, collected, live, copied, N);
1091 #if defined(RTS_USER_SIGNALS)
1092 // unblock signals again
1093 unblockUserSignals();
1100 /* -----------------------------------------------------------------------------
1103 traverse_weak_ptr_list is called possibly many times during garbage
1104 collection. It returns a flag indicating whether it did any work
1105 (i.e. called evacuate on any live pointers).
1107 Invariant: traverse_weak_ptr_list is called when the heap is in an
1108 idempotent state. That means that there are no pending
1109 evacuate/scavenge operations. This invariant helps the weak
1110 pointer code decide which weak pointers are dead - if there are no
1111 new live weak pointers, then all the currently unreachable ones are
1114 For generational GC: we just don't try to finalize weak pointers in
1115 older generations than the one we're collecting. This could
1116 probably be optimised by keeping per-generation lists of weak
1117 pointers, but for a few weak pointers this scheme will work.
1119 There are three distinct stages to processing weak pointers:
1121 - weak_stage == WeakPtrs
1123 We process all the weak pointers whos keys are alive (evacuate
1124 their values and finalizers), and repeat until we can find no new
1125 live keys. If no live keys are found in this pass, then we
1126 evacuate the finalizers of all the dead weak pointers in order to
1129 - weak_stage == WeakThreads
1131 Now, we discover which *threads* are still alive. Pointers to
1132 threads from the all_threads and main thread lists are the
1133 weakest of all: a pointers from the finalizer of a dead weak
1134 pointer can keep a thread alive. Any threads found to be unreachable
1135 are evacuated and placed on the resurrected_threads list so we
1136 can send them a signal later.
1138 - weak_stage == WeakDone
1140 No more evacuation is done.
1142 -------------------------------------------------------------------------- */
1145 traverse_weak_ptr_list(void)
1147 StgWeak *w, **last_w, *next_w;
1149 rtsBool flag = rtsFalse;
1151 switch (weak_stage) {
1157 /* doesn't matter where we evacuate values/finalizers to, since
1158 * these pointers are treated as roots (iff the keys are alive).
1162 last_w = &old_weak_ptr_list;
1163 for (w = old_weak_ptr_list; w != NULL; w = next_w) {
1165 /* There might be a DEAD_WEAK on the list if finalizeWeak# was
1166 * called on a live weak pointer object. Just remove it.
1168 if (w->header.info == &stg_DEAD_WEAK_info) {
1169 next_w = ((StgDeadWeak *)w)->link;
1174 switch (get_itbl(w)->type) {
1177 next_w = (StgWeak *)((StgEvacuated *)w)->evacuee;
1182 /* Now, check whether the key is reachable.
1184 new = isAlive(w->key);
1187 // evacuate the value and finalizer
1188 w->value = evacuate(w->value);
1189 w->finalizer = evacuate(w->finalizer);
1190 // remove this weak ptr from the old_weak_ptr list
1192 // and put it on the new weak ptr list
1194 w->link = weak_ptr_list;
1197 IF_DEBUG(weak, belch("Weak pointer still alive at %p -> %p",
1202 last_w = &(w->link);
1208 barf("traverse_weak_ptr_list: not WEAK");
1212 /* If we didn't make any changes, then we can go round and kill all
1213 * the dead weak pointers. The old_weak_ptr list is used as a list
1214 * of pending finalizers later on.
1216 if (flag == rtsFalse) {
1217 for (w = old_weak_ptr_list; w; w = w->link) {
1218 w->finalizer = evacuate(w->finalizer);
1221 // Next, move to the WeakThreads stage after fully
1222 // scavenging the finalizers we've just evacuated.
1223 weak_stage = WeakThreads;
1229 /* Now deal with the all_threads list, which behaves somewhat like
1230 * the weak ptr list. If we discover any threads that are about to
1231 * become garbage, we wake them up and administer an exception.
1234 StgTSO *t, *tmp, *next, **prev;
1236 prev = &old_all_threads;
1237 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1239 (StgClosure *)tmp = isAlive((StgClosure *)t);
1245 ASSERT(get_itbl(t)->type == TSO);
1246 switch (t->what_next) {
1247 case ThreadRelocated:
1252 case ThreadComplete:
1253 // finshed or died. The thread might still be alive, but we
1254 // don't keep it on the all_threads list. Don't forget to
1255 // stub out its global_link field.
1256 next = t->global_link;
1257 t->global_link = END_TSO_QUEUE;
1265 // not alive (yet): leave this thread on the
1266 // old_all_threads list.
1267 prev = &(t->global_link);
1268 next = t->global_link;
1271 // alive: move this thread onto the all_threads list.
1272 next = t->global_link;
1273 t->global_link = all_threads;
1280 /* And resurrect any threads which were about to become garbage.
1283 StgTSO *t, *tmp, *next;
1284 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1285 next = t->global_link;
1286 (StgClosure *)tmp = evacuate((StgClosure *)t);
1287 tmp->global_link = resurrected_threads;
1288 resurrected_threads = tmp;
1292 weak_stage = WeakDone; // *now* we're done,
1293 return rtsTrue; // but one more round of scavenging, please
1296 barf("traverse_weak_ptr_list");
1302 /* -----------------------------------------------------------------------------
1303 After GC, the live weak pointer list may have forwarding pointers
1304 on it, because a weak pointer object was evacuated after being
1305 moved to the live weak pointer list. We remove those forwarding
1308 Also, we don't consider weak pointer objects to be reachable, but
1309 we must nevertheless consider them to be "live" and retain them.
1310 Therefore any weak pointer objects which haven't as yet been
1311 evacuated need to be evacuated now.
1312 -------------------------------------------------------------------------- */
1316 mark_weak_ptr_list ( StgWeak **list )
1318 StgWeak *w, **last_w;
1321 for (w = *list; w; w = w->link) {
1322 // w might be WEAK, EVACUATED, or DEAD_WEAK (actually CON_STATIC) here
1323 ASSERT(w->header.info == &stg_DEAD_WEAK_info
1324 || get_itbl(w)->type == WEAK || get_itbl(w)->type == EVACUATED);
1325 (StgClosure *)w = evacuate((StgClosure *)w);
1327 last_w = &(w->link);
1331 /* -----------------------------------------------------------------------------
1332 isAlive determines whether the given closure is still alive (after
1333 a garbage collection) or not. It returns the new address of the
1334 closure if it is alive, or NULL otherwise.
1336 NOTE: Use it before compaction only!
1337 -------------------------------------------------------------------------- */
1341 isAlive(StgClosure *p)
1343 const StgInfoTable *info;
1348 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
1351 // ignore static closures
1353 // ToDo: for static closures, check the static link field.
1354 // Problem here is that we sometimes don't set the link field, eg.
1355 // for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
1357 if (!HEAP_ALLOCED(p)) {
1361 // ignore closures in generations that we're not collecting.
1363 if (bd->gen_no > N) {
1367 // if it's a pointer into to-space, then we're done
1368 if (bd->flags & BF_EVACUATED) {
1372 // large objects use the evacuated flag
1373 if (bd->flags & BF_LARGE) {
1377 // check the mark bit for compacted steps
1378 if (bd->step->is_compacted && is_marked((P_)p,bd)) {
1382 switch (info->type) {
1387 case IND_OLDGEN: // rely on compatible layout with StgInd
1388 case IND_OLDGEN_PERM:
1389 // follow indirections
1390 p = ((StgInd *)p)->indirectee;
1395 return ((StgEvacuated *)p)->evacuee;
1398 if (((StgTSO *)p)->what_next == ThreadRelocated) {
1399 p = (StgClosure *)((StgTSO *)p)->link;
1412 mark_root(StgClosure **root)
1414 *root = evacuate(*root);
1418 upd_evacuee(StgClosure *p, StgClosure *dest)
1420 // Source object must be in from-space:
1421 ASSERT((Bdescr((P_)p)->flags & BF_EVACUATED) == 0);
1422 // not true: (ToDo: perhaps it should be)
1423 // ASSERT(Bdescr((P_)dest)->flags & BF_EVACUATED);
1424 p->header.info = &stg_EVACUATED_info;
1425 ((StgEvacuated *)p)->evacuee = dest;
1429 STATIC_INLINE StgClosure *
1430 copy(StgClosure *src, nat size, step *stp)
1435 nat size_org = size;
1438 TICK_GC_WORDS_COPIED(size);
1439 /* Find out where we're going, using the handy "to" pointer in
1440 * the step of the source object. If it turns out we need to
1441 * evacuate to an older generation, adjust it here (see comment
1444 if (stp->gen_no < evac_gen) {
1445 #ifdef NO_EAGER_PROMOTION
1446 failed_to_evac = rtsTrue;
1448 stp = &generations[evac_gen].steps[0];
1452 /* chain a new block onto the to-space for the destination step if
1455 if (stp->hp + size >= stp->hpLim) {
1456 gc_alloc_block(stp);
1459 for(to = stp->hp, from = (P_)src; size>0; --size) {
1465 upd_evacuee(src,(StgClosure *)dest);
1467 // We store the size of the just evacuated object in the LDV word so that
1468 // the profiler can guess the position of the next object later.
1469 SET_EVACUAEE_FOR_LDV(src, size_org);
1471 return (StgClosure *)dest;
1474 /* Special version of copy() for when we only want to copy the info
1475 * pointer of an object, but reserve some padding after it. This is
1476 * used to optimise evacuation of BLACKHOLEs.
1481 copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *stp)
1486 nat size_to_copy_org = size_to_copy;
1489 TICK_GC_WORDS_COPIED(size_to_copy);
1490 if (stp->gen_no < evac_gen) {
1491 #ifdef NO_EAGER_PROMOTION
1492 failed_to_evac = rtsTrue;
1494 stp = &generations[evac_gen].steps[0];
1498 if (stp->hp + size_to_reserve >= stp->hpLim) {
1499 gc_alloc_block(stp);
1502 for(to = stp->hp, from = (P_)src; size_to_copy>0; --size_to_copy) {
1507 stp->hp += size_to_reserve;
1508 upd_evacuee(src,(StgClosure *)dest);
1510 // We store the size of the just evacuated object in the LDV word so that
1511 // the profiler can guess the position of the next object later.
1512 // size_to_copy_org is wrong because the closure already occupies size_to_reserve
1514 SET_EVACUAEE_FOR_LDV(src, size_to_reserve);
1516 if (size_to_reserve - size_to_copy_org > 0)
1517 FILL_SLOP(stp->hp - 1, (int)(size_to_reserve - size_to_copy_org));
1519 return (StgClosure *)dest;
1523 /* -----------------------------------------------------------------------------
1524 Evacuate a large object
1526 This just consists of removing the object from the (doubly-linked)
1527 step->large_objects list, and linking it on to the (singly-linked)
1528 step->new_large_objects list, from where it will be scavenged later.
1530 Convention: bd->flags has BF_EVACUATED set for a large object
1531 that has been evacuated, or unset otherwise.
1532 -------------------------------------------------------------------------- */
1536 evacuate_large(StgPtr p)
1538 bdescr *bd = Bdescr(p);
1541 // object must be at the beginning of the block (or be a ByteArray)
1542 ASSERT(get_itbl((StgClosure *)p)->type == ARR_WORDS ||
1543 (((W_)p & BLOCK_MASK) == 0));
1545 // already evacuated?
1546 if (bd->flags & BF_EVACUATED) {
1547 /* Don't forget to set the failed_to_evac flag if we didn't get
1548 * the desired destination (see comments in evacuate()).
1550 if (bd->gen_no < evac_gen) {
1551 failed_to_evac = rtsTrue;
1552 TICK_GC_FAILED_PROMOTION();
1558 // remove from large_object list
1560 bd->u.back->link = bd->link;
1561 } else { // first object in the list
1562 stp->large_objects = bd->link;
1565 bd->link->u.back = bd->u.back;
1568 /* link it on to the evacuated large object list of the destination step
1571 if (stp->gen_no < evac_gen) {
1572 #ifdef NO_EAGER_PROMOTION
1573 failed_to_evac = rtsTrue;
1575 stp = &generations[evac_gen].steps[0];
1580 bd->gen_no = stp->gen_no;
1581 bd->link = stp->new_large_objects;
1582 stp->new_large_objects = bd;
1583 bd->flags |= BF_EVACUATED;
1586 /* -----------------------------------------------------------------------------
1587 Adding a MUT_CONS to an older generation.
1589 This is necessary from time to time when we end up with an
1590 old-to-new generation pointer in a non-mutable object. We defer
1591 the promotion until the next GC.
1592 -------------------------------------------------------------------------- */
1595 mkMutCons(StgClosure *ptr, generation *gen)
1600 stp = &gen->steps[0];
1602 /* chain a new block onto the to-space for the destination step if
1605 if (stp->hp + sizeofW(StgIndOldGen) >= stp->hpLim) {
1606 gc_alloc_block(stp);
1609 q = (StgMutVar *)stp->hp;
1610 stp->hp += sizeofW(StgMutVar);
1612 SET_HDR(q,&stg_MUT_CONS_info,CCS_GC);
1614 recordOldToNewPtrs((StgMutClosure *)q);
1616 return (StgClosure *)q;
1619 /* -----------------------------------------------------------------------------
1622 This is called (eventually) for every live object in the system.
1624 The caller to evacuate specifies a desired generation in the
1625 evac_gen global variable. The following conditions apply to
1626 evacuating an object which resides in generation M when we're
1627 collecting up to generation N
1631 else evac to step->to
1633 if M < evac_gen evac to evac_gen, step 0
1635 if the object is already evacuated, then we check which generation
1638 if M >= evac_gen do nothing
1639 if M < evac_gen set failed_to_evac flag to indicate that we
1640 didn't manage to evacuate this object into evac_gen.
1645 evacuate() is the single most important function performance-wise
1646 in the GC. Various things have been tried to speed it up, but as
1647 far as I can tell the code generated by gcc 3.2 with -O2 is about
1648 as good as it's going to get. We pass the argument to evacuate()
1649 in a register using the 'regparm' attribute (see the prototype for
1650 evacuate() near the top of this file).
1652 Changing evacuate() to take an (StgClosure **) rather than
1653 returning the new pointer seems attractive, because we can avoid
1654 writing back the pointer when it hasn't changed (eg. for a static
1655 object, or an object in a generation > N). However, I tried it and
1656 it doesn't help. One reason is that the (StgClosure **) pointer
1657 gets spilled to the stack inside evacuate(), resulting in far more
1658 extra reads/writes than we save.
1659 -------------------------------------------------------------------------- */
1662 evacuate(StgClosure *q)
1667 const StgInfoTable *info;
1670 if (HEAP_ALLOCED(q)) {
1673 if (bd->gen_no > N) {
1674 /* Can't evacuate this object, because it's in a generation
1675 * older than the ones we're collecting. Let's hope that it's
1676 * in evac_gen or older, or we will have to arrange to track
1677 * this pointer using the mutable list.
1679 if (bd->gen_no < evac_gen) {
1681 failed_to_evac = rtsTrue;
1682 TICK_GC_FAILED_PROMOTION();
1687 /* evacuate large objects by re-linking them onto a different list.
1689 if (bd->flags & BF_LARGE) {
1691 if (info->type == TSO &&
1692 ((StgTSO *)q)->what_next == ThreadRelocated) {
1693 q = (StgClosure *)((StgTSO *)q)->link;
1696 evacuate_large((P_)q);
1700 /* If the object is in a step that we're compacting, then we
1701 * need to use an alternative evacuate procedure.
1703 if (bd->step->is_compacted) {
1704 if (!is_marked((P_)q,bd)) {
1706 if (mark_stack_full()) {
1707 mark_stack_overflowed = rtsTrue;
1710 push_mark_stack((P_)q);
1718 else stp = NULL; // make sure copy() will crash if HEAP_ALLOCED is wrong
1721 // make sure the info pointer is into text space
1722 ASSERT(LOOKS_LIKE_CLOSURE_PTR(q));
1725 switch (info -> type) {
1729 return copy(q,sizeW_fromITBL(info),stp);
1733 StgWord w = (StgWord)q->payload[0];
1734 if (q->header.info == Czh_con_info &&
1735 // unsigned, so always true: (StgChar)w >= MIN_CHARLIKE &&
1736 (StgChar)w <= MAX_CHARLIKE) {
1737 return (StgClosure *)CHARLIKE_CLOSURE((StgChar)w);
1739 if (q->header.info == Izh_con_info &&
1740 (StgInt)w >= MIN_INTLIKE && (StgInt)w <= MAX_INTLIKE) {
1741 return (StgClosure *)INTLIKE_CLOSURE((StgInt)w);
1743 // else, fall through ...
1749 return copy(q,sizeofW(StgHeader)+1,stp);
1751 case THUNK_1_0: // here because of MIN_UPD_SIZE
1756 #ifdef NO_PROMOTE_THUNKS
1757 if (bd->gen_no == 0 &&
1758 bd->step->no != 0 &&
1759 bd->step->no == generations[bd->gen_no].n_steps-1) {
1763 return copy(q,sizeofW(StgHeader)+2,stp);
1771 return copy(q,sizeofW(StgHeader)+2,stp);
1777 case IND_OLDGEN_PERM:
1781 return copy(q,sizeW_fromITBL(info),stp);
1784 return copy(q,bco_sizeW((StgBCO *)q),stp);
1787 case SE_CAF_BLACKHOLE:
1790 return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
1793 to = copy(q,BLACKHOLE_sizeW(),stp);
1796 case THUNK_SELECTOR:
1800 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
1801 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1804 p = eval_thunk_selector(info->layout.selector_offset,
1808 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1810 // q is still BLACKHOLE'd.
1811 thunk_selector_depth++;
1813 thunk_selector_depth--;
1816 // We store the size of the just evacuated object in the
1817 // LDV word so that the profiler can guess the position of
1818 // the next object later.
1819 SET_EVACUAEE_FOR_LDV(q, THUNK_SELECTOR_sizeW());
1827 // follow chains of indirections, don't evacuate them
1828 q = ((StgInd*)q)->indirectee;
1832 if (info->srt_bitmap != 0 && major_gc &&
1833 THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
1834 THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
1835 static_objects = (StgClosure *)q;
1840 if (info->srt_bitmap != 0 && major_gc &&
1841 FUN_STATIC_LINK((StgClosure *)q) == NULL) {
1842 FUN_STATIC_LINK((StgClosure *)q) = static_objects;
1843 static_objects = (StgClosure *)q;
1848 /* If q->saved_info != NULL, then it's a revertible CAF - it'll be
1849 * on the CAF list, so don't do anything with it here (we'll
1850 * scavenge it later).
1853 && ((StgIndStatic *)q)->saved_info == NULL
1854 && IND_STATIC_LINK((StgClosure *)q) == NULL) {
1855 IND_STATIC_LINK((StgClosure *)q) = static_objects;
1856 static_objects = (StgClosure *)q;
1861 if (major_gc && STATIC_LINK(info,(StgClosure *)q) == NULL) {
1862 STATIC_LINK(info,(StgClosure *)q) = static_objects;
1863 static_objects = (StgClosure *)q;
1867 case CONSTR_INTLIKE:
1868 case CONSTR_CHARLIKE:
1869 case CONSTR_NOCAF_STATIC:
1870 /* no need to put these on the static linked list, they don't need
1884 // shouldn't see these
1885 barf("evacuate: stack frame at %p\n", q);
1889 return copy(q,pap_sizeW((StgPAP*)q),stp);
1892 return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp);
1895 /* Already evacuated, just return the forwarding address.
1896 * HOWEVER: if the requested destination generation (evac_gen) is
1897 * older than the actual generation (because the object was
1898 * already evacuated to a younger generation) then we have to
1899 * set the failed_to_evac flag to indicate that we couldn't
1900 * manage to promote the object to the desired generation.
1902 if (evac_gen > 0) { // optimisation
1903 StgClosure *p = ((StgEvacuated*)q)->evacuee;
1904 if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < evac_gen) {
1905 failed_to_evac = rtsTrue;
1906 TICK_GC_FAILED_PROMOTION();
1909 return ((StgEvacuated*)q)->evacuee;
1912 // just copy the block
1913 return copy(q,arr_words_sizeW((StgArrWords *)q),stp);
1916 case MUT_ARR_PTRS_FROZEN:
1917 // just copy the block
1918 return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
1922 StgTSO *tso = (StgTSO *)q;
1924 /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
1926 if (tso->what_next == ThreadRelocated) {
1927 q = (StgClosure *)tso->link;
1931 /* To evacuate a small TSO, we need to relocate the update frame
1938 new_tso = (StgTSO *)copyPart((StgClosure *)tso,
1940 sizeofW(StgTSO), stp);
1941 move_TSO(tso, new_tso);
1942 for (p = tso->sp, q = new_tso->sp;
1943 p < tso->stack+tso->stack_size;) {
1947 return (StgClosure *)new_tso;
1952 case RBH: // cf. BLACKHOLE_BQ
1954 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
1955 to = copy(q,BLACKHOLE_sizeW(),stp);
1956 //ToDo: derive size etc from reverted IP
1957 //to = copy(q,size,stp);
1959 belch("@@ evacuate: RBH %p (%s) to %p (%s)",
1960 q, info_type(q), to, info_type(to)));
1965 ASSERT(sizeofW(StgBlockedFetch) >= MIN_NONUPD_SIZE);
1966 to = copy(q,sizeofW(StgBlockedFetch),stp);
1968 belch("@@ evacuate: %p (%s) to %p (%s)",
1969 q, info_type(q), to, info_type(to)));
1976 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1977 to = copy(q,sizeofW(StgFetchMe),stp);
1979 belch("@@ evacuate: %p (%s) to %p (%s)",
1980 q, info_type(q), to, info_type(to)));
1984 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1985 to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
1987 belch("@@ evacuate: %p (%s) to %p (%s)",
1988 q, info_type(q), to, info_type(to)));
1993 barf("evacuate: strange closure type %d", (int)(info->type));
1999 /* -----------------------------------------------------------------------------
2000 Evaluate a THUNK_SELECTOR if possible.
2002 returns: NULL if we couldn't evaluate this THUNK_SELECTOR, or
2003 a closure pointer if we evaluated it and this is the result. Note
2004 that "evaluating" the THUNK_SELECTOR doesn't necessarily mean
2005 reducing it to HNF, just that we have eliminated the selection.
2006 The result might be another thunk, or even another THUNK_SELECTOR.
2008 If the return value is non-NULL, the original selector thunk has
2009 been BLACKHOLE'd, and should be updated with an indirection or a
2010 forwarding pointer. If the return value is NULL, then the selector
2012 -------------------------------------------------------------------------- */
2015 eval_thunk_selector( nat field, StgSelector * p )
2018 const StgInfoTable *info_ptr;
2019 StgClosure *selectee;
2021 selectee = p->selectee;
2023 // Save the real info pointer (NOTE: not the same as get_itbl()).
2024 info_ptr = p->header.info;
2026 // If the THUNK_SELECTOR is in a generation that we are not
2027 // collecting, then bail out early. We won't be able to save any
2028 // space in any case, and updating with an indirection is trickier
2030 if (Bdescr((StgPtr)p)->gen_no > N) {
2034 // BLACKHOLE the selector thunk, since it is now under evaluation.
2035 // This is important to stop us going into an infinite loop if
2036 // this selector thunk eventually refers to itself.
2037 SET_INFO(p,&stg_BLACKHOLE_info);
2041 // We don't want to end up in to-space, because this causes
2042 // problems when the GC later tries to evacuate the result of
2043 // eval_thunk_selector(). There are various ways this could
2046 // - following an IND_STATIC
2048 // - when the old generation is compacted, the mark phase updates
2049 // from-space pointers to be to-space pointers, and we can't
2050 // reliably tell which we're following (eg. from an IND_STATIC).
2052 // So we use the block-descriptor test to find out if we're in
2055 if (HEAP_ALLOCED(selectee) &&
2056 Bdescr((StgPtr)selectee)->flags & BF_EVACUATED) {
2060 info = get_itbl(selectee);
2061 switch (info->type) {
2069 case CONSTR_NOCAF_STATIC:
2070 // check that the size is in range
2071 ASSERT(field < (StgWord32)(info->layout.payload.ptrs +
2072 info->layout.payload.nptrs));
2074 // ToDo: shouldn't we test whether this pointer is in
2076 return selectee->payload[field];
2081 case IND_OLDGEN_PERM:
2083 selectee = ((StgInd *)selectee)->indirectee;
2087 // We don't follow pointers into to-space; the constructor
2088 // has already been evacuated, so we won't save any space
2089 // leaks by evaluating this selector thunk anyhow.
2092 case THUNK_SELECTOR:
2096 // check that we don't recurse too much, re-using the
2097 // depth bound also used in evacuate().
2098 thunk_selector_depth++;
2099 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
2103 val = eval_thunk_selector(info->layout.selector_offset,
2104 (StgSelector *)selectee);
2106 thunk_selector_depth--;
2111 // We evaluated this selector thunk, so update it with
2112 // an indirection. NOTE: we don't use UPD_IND here,
2113 // because we are guaranteed that p is in a generation
2114 // that we are collecting, and we never want to put the
2115 // indirection on a mutable list.
2117 // For the purposes of LDV profiling, we have destroyed
2118 // the original selector thunk.
2119 SET_INFO(p, info_ptr);
2120 LDV_recordDead_FILL_SLOP_DYNAMIC(selectee);
2122 ((StgInd *)selectee)->indirectee = val;
2123 SET_INFO(selectee,&stg_IND_info);
2125 // For the purposes of LDV profiling, we have created an
2127 LDV_recordCreate(selectee);
2144 case SE_CAF_BLACKHOLE:
2157 // not evaluated yet
2161 barf("eval_thunk_selector: strange selectee %d",
2166 // We didn't manage to evaluate this thunk; restore the old info pointer
2167 SET_INFO(p, info_ptr);
2171 /* -----------------------------------------------------------------------------
2172 move_TSO is called to update the TSO structure after it has been
2173 moved from one place to another.
2174 -------------------------------------------------------------------------- */
2177 move_TSO (StgTSO *src, StgTSO *dest)
2181 // relocate the stack pointer...
2182 diff = (StgPtr)dest - (StgPtr)src; // In *words*
2183 dest->sp = (StgPtr)dest->sp + diff;
2186 /* Similar to scavenge_large_bitmap(), but we don't write back the
2187 * pointers we get back from evacuate().
2190 scavenge_large_srt_bitmap( StgLargeSRT *large_srt )
2197 bitmap = large_srt->l.bitmap[b];
2198 size = (nat)large_srt->l.size;
2199 p = (StgClosure **)large_srt->srt;
2200 for (i = 0; i < size; ) {
2201 if ((bitmap & 1) != 0) {
2206 if (i % BITS_IN(W_) == 0) {
2208 bitmap = large_srt->l.bitmap[b];
2210 bitmap = bitmap >> 1;
2215 /* evacuate the SRT. If srt_bitmap is zero, then there isn't an
2216 * srt field in the info table. That's ok, because we'll
2217 * never dereference it.
2220 scavenge_srt (StgClosure **srt, nat srt_bitmap)
2225 bitmap = srt_bitmap;
2228 if (bitmap == (StgHalfWord)(-1)) {
2229 scavenge_large_srt_bitmap( (StgLargeSRT *)srt );
2233 while (bitmap != 0) {
2234 if ((bitmap & 1) != 0) {
2235 #ifdef ENABLE_WIN32_DLL_SUPPORT
2236 // Special-case to handle references to closures hiding out in DLLs, since
2237 // double indirections required to get at those. The code generator knows
2238 // which is which when generating the SRT, so it stores the (indirect)
2239 // reference to the DLL closure in the table by first adding one to it.
2240 // We check for this here, and undo the addition before evacuating it.
2242 // If the SRT entry hasn't got bit 0 set, the SRT entry points to a
2243 // closure that's fixed at link-time, and no extra magic is required.
2244 if ( (unsigned long)(*srt) & 0x1 ) {
2245 evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
2254 bitmap = bitmap >> 1;
2260 scavenge_thunk_srt(const StgInfoTable *info)
2262 StgThunkInfoTable *thunk_info;
2264 thunk_info = itbl_to_thunk_itbl(info);
2265 scavenge_srt((StgClosure **)thunk_info->srt, thunk_info->i.srt_bitmap);
2269 scavenge_fun_srt(const StgInfoTable *info)
2271 StgFunInfoTable *fun_info;
2273 fun_info = itbl_to_fun_itbl(info);
2274 scavenge_srt((StgClosure **)fun_info->srt, fun_info->i.srt_bitmap);
2278 scavenge_ret_srt(const StgInfoTable *info)
2280 StgRetInfoTable *ret_info;
2282 ret_info = itbl_to_ret_itbl(info);
2283 scavenge_srt((StgClosure **)ret_info->srt, ret_info->i.srt_bitmap);
2286 /* -----------------------------------------------------------------------------
2288 -------------------------------------------------------------------------- */
2291 scavengeTSO (StgTSO *tso)
2293 // chase the link field for any TSOs on the same queue
2294 (StgClosure *)tso->link = evacuate((StgClosure *)tso->link);
2295 if ( tso->why_blocked == BlockedOnMVar
2296 || tso->why_blocked == BlockedOnBlackHole
2297 || tso->why_blocked == BlockedOnException
2299 || tso->why_blocked == BlockedOnGA
2300 || tso->why_blocked == BlockedOnGA_NoSend
2303 tso->block_info.closure = evacuate(tso->block_info.closure);
2305 if ( tso->blocked_exceptions != NULL ) {
2306 tso->blocked_exceptions =
2307 (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
2310 // scavenge this thread's stack
2311 scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
2314 /* -----------------------------------------------------------------------------
2315 Blocks of function args occur on the stack (at the top) and
2317 -------------------------------------------------------------------------- */
2319 STATIC_INLINE StgPtr
2320 scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
2327 switch (fun_info->fun_type) {
2329 bitmap = BITMAP_BITS(fun_info->bitmap);
2330 size = BITMAP_SIZE(fun_info->bitmap);
2333 size = ((StgLargeBitmap *)fun_info->bitmap)->size;
2334 scavenge_large_bitmap(p, (StgLargeBitmap *)fun_info->bitmap, size);
2338 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->fun_type]);
2339 size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->fun_type]);
2342 if ((bitmap & 1) == 0) {
2343 (StgClosure *)*p = evacuate((StgClosure *)*p);
2346 bitmap = bitmap >> 1;
2354 STATIC_INLINE StgPtr
2355 scavenge_PAP (StgPAP *pap)
2358 StgWord bitmap, size;
2359 StgFunInfoTable *fun_info;
2361 pap->fun = evacuate(pap->fun);
2362 fun_info = get_fun_itbl(pap->fun);
2363 ASSERT(fun_info->i.type != PAP);
2365 p = (StgPtr)pap->payload;
2368 switch (fun_info->fun_type) {
2370 bitmap = BITMAP_BITS(fun_info->bitmap);
2373 scavenge_large_bitmap(p, (StgLargeBitmap *)fun_info->bitmap, size);
2377 scavenge_large_bitmap((StgPtr)pap->payload, BCO_BITMAP(pap->fun), size);
2381 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->fun_type]);
2385 if ((bitmap & 1) == 0) {
2386 (StgClosure *)*p = evacuate((StgClosure *)*p);
2389 bitmap = bitmap >> 1;
2397 /* -----------------------------------------------------------------------------
2398 Scavenge a given step until there are no more objects in this step
2401 evac_gen is set by the caller to be either zero (for a step in a
2402 generation < N) or G where G is the generation of the step being
2405 We sometimes temporarily change evac_gen back to zero if we're
2406 scavenging a mutable object where early promotion isn't such a good
2408 -------------------------------------------------------------------------- */
2416 nat saved_evac_gen = evac_gen;
2421 failed_to_evac = rtsFalse;
2423 /* scavenge phase - standard breadth-first scavenging of the
2427 while (bd != stp->hp_bd || p < stp->hp) {
2429 // If we're at the end of this block, move on to the next block
2430 if (bd != stp->hp_bd && p == bd->free) {
2436 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2437 info = get_itbl((StgClosure *)p);
2439 ASSERT(thunk_selector_depth == 0);
2442 switch (info->type) {
2445 /* treat MVars specially, because we don't want to evacuate the
2446 * mut_link field in the middle of the closure.
2449 StgMVar *mvar = ((StgMVar *)p);
2451 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
2452 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
2453 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
2454 evac_gen = saved_evac_gen;
2455 recordMutable((StgMutClosure *)mvar);
2456 failed_to_evac = rtsFalse; // mutable.
2457 p += sizeofW(StgMVar);
2462 scavenge_fun_srt(info);
2463 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2464 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2465 p += sizeofW(StgHeader) + 2;
2469 scavenge_thunk_srt(info);
2471 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2472 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2473 p += sizeofW(StgHeader) + 2;
2477 scavenge_thunk_srt(info);
2478 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2479 p += sizeofW(StgHeader) + 2; // MIN_UPD_SIZE
2483 scavenge_fun_srt(info);
2485 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2486 p += sizeofW(StgHeader) + 1;
2490 scavenge_thunk_srt(info);
2491 p += sizeofW(StgHeader) + 2; // MIN_UPD_SIZE
2495 scavenge_fun_srt(info);
2497 p += sizeofW(StgHeader) + 1;
2501 scavenge_thunk_srt(info);
2502 p += sizeofW(StgHeader) + 2;
2506 scavenge_fun_srt(info);
2508 p += sizeofW(StgHeader) + 2;
2512 scavenge_thunk_srt(info);
2513 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2514 p += sizeofW(StgHeader) + 2;
2518 scavenge_fun_srt(info);
2520 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2521 p += sizeofW(StgHeader) + 2;
2525 scavenge_fun_srt(info);
2529 scavenge_thunk_srt(info);
2540 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2541 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2542 (StgClosure *)*p = evacuate((StgClosure *)*p);
2544 p += info->layout.payload.nptrs;
2549 StgBCO *bco = (StgBCO *)p;
2550 (StgClosure *)bco->instrs = evacuate((StgClosure *)bco->instrs);
2551 (StgClosure *)bco->literals = evacuate((StgClosure *)bco->literals);
2552 (StgClosure *)bco->ptrs = evacuate((StgClosure *)bco->ptrs);
2553 (StgClosure *)bco->itbls = evacuate((StgClosure *)bco->itbls);
2554 p += bco_sizeW(bco);
2559 if (stp->gen->no != 0) {
2562 // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an
2563 // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
2564 LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
2567 // Todo: maybe use SET_HDR() and remove LDV_recordCreate()?
2569 SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
2572 // We pretend that p has just been created.
2573 LDV_recordCreate((StgClosure *)p);
2577 case IND_OLDGEN_PERM:
2578 ((StgIndOldGen *)p)->indirectee =
2579 evacuate(((StgIndOldGen *)p)->indirectee);
2580 if (failed_to_evac) {
2581 failed_to_evac = rtsFalse;
2582 recordOldToNewPtrs((StgMutClosure *)p);
2584 p += sizeofW(StgIndOldGen);
2589 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2590 evac_gen = saved_evac_gen;
2591 recordMutable((StgMutClosure *)p);
2592 failed_to_evac = rtsFalse; // mutable anyhow
2593 p += sizeofW(StgMutVar);
2598 failed_to_evac = rtsFalse; // mutable anyhow
2599 p += sizeofW(StgMutVar);
2603 case SE_CAF_BLACKHOLE:
2606 p += BLACKHOLE_sizeW();
2611 StgBlockingQueue *bh = (StgBlockingQueue *)p;
2612 (StgClosure *)bh->blocking_queue =
2613 evacuate((StgClosure *)bh->blocking_queue);
2614 recordMutable((StgMutClosure *)bh);
2615 failed_to_evac = rtsFalse;
2616 p += BLACKHOLE_sizeW();
2620 case THUNK_SELECTOR:
2622 StgSelector *s = (StgSelector *)p;
2623 s->selectee = evacuate(s->selectee);
2624 p += THUNK_SELECTOR_sizeW();
2628 // A chunk of stack saved in a heap object
2631 StgAP_STACK *ap = (StgAP_STACK *)p;
2633 ap->fun = evacuate(ap->fun);
2634 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2635 p = (StgPtr)ap->payload + ap->size;
2641 p = scavenge_PAP((StgPAP *)p);
2645 // nothing to follow
2646 p += arr_words_sizeW((StgArrWords *)p);
2650 // follow everything
2654 evac_gen = 0; // repeatedly mutable
2655 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2656 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2657 (StgClosure *)*p = evacuate((StgClosure *)*p);
2659 evac_gen = saved_evac_gen;
2660 recordMutable((StgMutClosure *)q);
2661 failed_to_evac = rtsFalse; // mutable anyhow.
2665 case MUT_ARR_PTRS_FROZEN:
2666 // follow everything
2670 // Set the mut_link field to NULL, so that we will put this
2671 // array back on the mutable list if it is subsequently thawed
2673 ((StgMutArrPtrs*)p)->mut_link = NULL;
2675 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2676 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2677 (StgClosure *)*p = evacuate((StgClosure *)*p);
2679 // it's tempting to recordMutable() if failed_to_evac is
2680 // false, but that breaks some assumptions (eg. every
2681 // closure on the mutable list is supposed to have the MUT
2682 // flag set, and MUT_ARR_PTRS_FROZEN doesn't).
2688 StgTSO *tso = (StgTSO *)p;
2691 evac_gen = saved_evac_gen;
2692 recordMutable((StgMutClosure *)tso);
2693 failed_to_evac = rtsFalse; // mutable anyhow.
2694 p += tso_sizeW(tso);
2699 case RBH: // cf. BLACKHOLE_BQ
2702 nat size, ptrs, nonptrs, vhs;
2704 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2706 StgRBH *rbh = (StgRBH *)p;
2707 (StgClosure *)rbh->blocking_queue =
2708 evacuate((StgClosure *)rbh->blocking_queue);
2709 recordMutable((StgMutClosure *)to);
2710 failed_to_evac = rtsFalse; // mutable anyhow.
2712 belch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2713 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2714 // ToDo: use size of reverted closure here!
2715 p += BLACKHOLE_sizeW();
2721 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2722 // follow the pointer to the node which is being demanded
2723 (StgClosure *)bf->node =
2724 evacuate((StgClosure *)bf->node);
2725 // follow the link to the rest of the blocking queue
2726 (StgClosure *)bf->link =
2727 evacuate((StgClosure *)bf->link);
2728 if (failed_to_evac) {
2729 failed_to_evac = rtsFalse;
2730 recordMutable((StgMutClosure *)bf);
2733 belch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
2734 bf, info_type((StgClosure *)bf),
2735 bf->node, info_type(bf->node)));
2736 p += sizeofW(StgBlockedFetch);
2744 p += sizeofW(StgFetchMe);
2745 break; // nothing to do in this case
2747 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
2749 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
2750 (StgClosure *)fmbq->blocking_queue =
2751 evacuate((StgClosure *)fmbq->blocking_queue);
2752 if (failed_to_evac) {
2753 failed_to_evac = rtsFalse;
2754 recordMutable((StgMutClosure *)fmbq);
2757 belch("@@ scavenge: %p (%s) exciting, isn't it",
2758 p, info_type((StgClosure *)p)));
2759 p += sizeofW(StgFetchMeBlockingQueue);
2765 barf("scavenge: unimplemented/strange closure type %d @ %p",
2769 /* If we didn't manage to promote all the objects pointed to by
2770 * the current object, then we have to designate this object as
2771 * mutable (because it contains old-to-new generation pointers).
2773 if (failed_to_evac) {
2774 failed_to_evac = rtsFalse;
2775 mkMutCons((StgClosure *)q, &generations[evac_gen]);
2783 /* -----------------------------------------------------------------------------
2784 Scavenge everything on the mark stack.
2786 This is slightly different from scavenge():
2787 - we don't walk linearly through the objects, so the scavenger
2788 doesn't need to advance the pointer on to the next object.
2789 -------------------------------------------------------------------------- */
2792 scavenge_mark_stack(void)
2798 evac_gen = oldest_gen->no;
2799 saved_evac_gen = evac_gen;
2802 while (!mark_stack_empty()) {
2803 p = pop_mark_stack();
2805 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2806 info = get_itbl((StgClosure *)p);
2809 switch (info->type) {
2812 /* treat MVars specially, because we don't want to evacuate the
2813 * mut_link field in the middle of the closure.
2816 StgMVar *mvar = ((StgMVar *)p);
2818 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
2819 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
2820 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
2821 evac_gen = saved_evac_gen;
2822 failed_to_evac = rtsFalse; // mutable.
2827 scavenge_fun_srt(info);
2828 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2829 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2833 scavenge_thunk_srt(info);
2835 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2836 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2841 scavenge_fun_srt(info);
2842 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2847 scavenge_thunk_srt(info);
2850 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2855 scavenge_fun_srt(info);
2860 scavenge_thunk_srt(info);
2868 scavenge_fun_srt(info);
2872 scavenge_thunk_srt(info);
2883 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2884 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2885 (StgClosure *)*p = evacuate((StgClosure *)*p);
2891 StgBCO *bco = (StgBCO *)p;
2892 (StgClosure *)bco->instrs = evacuate((StgClosure *)bco->instrs);
2893 (StgClosure *)bco->literals = evacuate((StgClosure *)bco->literals);
2894 (StgClosure *)bco->ptrs = evacuate((StgClosure *)bco->ptrs);
2895 (StgClosure *)bco->itbls = evacuate((StgClosure *)bco->itbls);
2900 // don't need to do anything here: the only possible case
2901 // is that we're in a 1-space compacting collector, with
2902 // no "old" generation.
2906 case IND_OLDGEN_PERM:
2907 ((StgIndOldGen *)p)->indirectee =
2908 evacuate(((StgIndOldGen *)p)->indirectee);
2909 if (failed_to_evac) {
2910 recordOldToNewPtrs((StgMutClosure *)p);
2912 failed_to_evac = rtsFalse;
2917 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2918 evac_gen = saved_evac_gen;
2919 failed_to_evac = rtsFalse;
2924 failed_to_evac = rtsFalse;
2928 case SE_CAF_BLACKHOLE:
2936 StgBlockingQueue *bh = (StgBlockingQueue *)p;
2937 (StgClosure *)bh->blocking_queue =
2938 evacuate((StgClosure *)bh->blocking_queue);
2939 failed_to_evac = rtsFalse;
2943 case THUNK_SELECTOR:
2945 StgSelector *s = (StgSelector *)p;
2946 s->selectee = evacuate(s->selectee);
2950 // A chunk of stack saved in a heap object
2953 StgAP_STACK *ap = (StgAP_STACK *)p;
2955 ap->fun = evacuate(ap->fun);
2956 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2962 scavenge_PAP((StgPAP *)p);
2966 // follow everything
2970 evac_gen = 0; // repeatedly mutable
2971 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2972 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2973 (StgClosure *)*p = evacuate((StgClosure *)*p);
2975 evac_gen = saved_evac_gen;
2976 failed_to_evac = rtsFalse; // mutable anyhow.
2980 case MUT_ARR_PTRS_FROZEN:
2981 // follow everything
2985 // Set the mut_link field to NULL, so that we will put this
2986 // array on the mutable list if it is subsequently thawed
2988 ((StgMutArrPtrs*)p)->mut_link = NULL;
2990 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2991 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2992 (StgClosure *)*p = evacuate((StgClosure *)*p);
2999 StgTSO *tso = (StgTSO *)p;
3002 evac_gen = saved_evac_gen;
3003 failed_to_evac = rtsFalse;
3008 case RBH: // cf. BLACKHOLE_BQ
3011 nat size, ptrs, nonptrs, vhs;
3013 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3015 StgRBH *rbh = (StgRBH *)p;
3016 (StgClosure *)rbh->blocking_queue =
3017 evacuate((StgClosure *)rbh->blocking_queue);
3018 recordMutable((StgMutClosure *)rbh);
3019 failed_to_evac = rtsFalse; // mutable anyhow.
3021 belch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3022 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3028 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3029 // follow the pointer to the node which is being demanded
3030 (StgClosure *)bf->node =
3031 evacuate((StgClosure *)bf->node);
3032 // follow the link to the rest of the blocking queue
3033 (StgClosure *)bf->link =
3034 evacuate((StgClosure *)bf->link);
3035 if (failed_to_evac) {
3036 failed_to_evac = rtsFalse;
3037 recordMutable((StgMutClosure *)bf);
3040 belch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3041 bf, info_type((StgClosure *)bf),
3042 bf->node, info_type(bf->node)));
3050 break; // nothing to do in this case
3052 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
3054 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3055 (StgClosure *)fmbq->blocking_queue =
3056 evacuate((StgClosure *)fmbq->blocking_queue);
3057 if (failed_to_evac) {
3058 failed_to_evac = rtsFalse;
3059 recordMutable((StgMutClosure *)fmbq);
3062 belch("@@ scavenge: %p (%s) exciting, isn't it",
3063 p, info_type((StgClosure *)p)));
3069 barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p",
3073 if (failed_to_evac) {
3074 failed_to_evac = rtsFalse;
3075 mkMutCons((StgClosure *)q, &generations[evac_gen]);
3078 // mark the next bit to indicate "scavenged"
3079 mark(q+1, Bdescr(q));
3081 } // while (!mark_stack_empty())
3083 // start a new linear scan if the mark stack overflowed at some point
3084 if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
3085 IF_DEBUG(gc, belch("scavenge_mark_stack: starting linear scan"));
3086 mark_stack_overflowed = rtsFalse;
3087 oldgen_scan_bd = oldest_gen->steps[0].blocks;
3088 oldgen_scan = oldgen_scan_bd->start;
3091 if (oldgen_scan_bd) {
3092 // push a new thing on the mark stack
3094 // find a closure that is marked but not scavenged, and start
3096 while (oldgen_scan < oldgen_scan_bd->free
3097 && !is_marked(oldgen_scan,oldgen_scan_bd)) {
3101 if (oldgen_scan < oldgen_scan_bd->free) {
3103 // already scavenged?
3104 if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
3105 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3108 push_mark_stack(oldgen_scan);
3109 // ToDo: bump the linear scan by the actual size of the object
3110 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3114 oldgen_scan_bd = oldgen_scan_bd->link;
3115 if (oldgen_scan_bd != NULL) {
3116 oldgen_scan = oldgen_scan_bd->start;
3122 /* -----------------------------------------------------------------------------
3123 Scavenge one object.
3125 This is used for objects that are temporarily marked as mutable
3126 because they contain old-to-new generation pointers. Only certain
3127 objects can have this property.
3128 -------------------------------------------------------------------------- */
3131 scavenge_one(StgPtr p)
3133 const StgInfoTable *info;
3134 nat saved_evac_gen = evac_gen;
3137 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3138 info = get_itbl((StgClosure *)p);
3140 switch (info->type) {
3143 case FUN_1_0: // hardly worth specialising these guys
3163 case IND_OLDGEN_PERM:
3167 end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3168 for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
3169 (StgClosure *)*q = evacuate((StgClosure *)*q);
3175 case SE_CAF_BLACKHOLE:
3180 case THUNK_SELECTOR:
3182 StgSelector *s = (StgSelector *)p;
3183 s->selectee = evacuate(s->selectee);
3188 // nothing to follow
3193 // follow everything
3196 evac_gen = 0; // repeatedly mutable
3197 recordMutable((StgMutClosure *)p);
3198 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3199 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3200 (StgClosure *)*p = evacuate((StgClosure *)*p);
3202 evac_gen = saved_evac_gen;
3203 failed_to_evac = rtsFalse;
3207 case MUT_ARR_PTRS_FROZEN:
3209 // follow everything
3212 // Set the mut_link field to NULL, so that we will put this
3213 // array on the mutable list if it is subsequently thawed
3215 ((StgMutArrPtrs*)p)->mut_link = NULL;
3217 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3218 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3219 (StgClosure *)*p = evacuate((StgClosure *)*p);
3226 StgTSO *tso = (StgTSO *)p;
3228 evac_gen = 0; // repeatedly mutable
3230 recordMutable((StgMutClosure *)tso);
3231 evac_gen = saved_evac_gen;
3232 failed_to_evac = rtsFalse;
3238 StgAP_STACK *ap = (StgAP_STACK *)p;
3240 ap->fun = evacuate(ap->fun);
3241 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3242 p = (StgPtr)ap->payload + ap->size;
3248 p = scavenge_PAP((StgPAP *)p);
3252 // This might happen if for instance a MUT_CONS was pointing to a
3253 // THUNK which has since been updated. The IND_OLDGEN will
3254 // be on the mutable list anyway, so we don't need to do anything
3259 barf("scavenge_one: strange object %d", (int)(info->type));
3262 no_luck = failed_to_evac;
3263 failed_to_evac = rtsFalse;
3267 /* -----------------------------------------------------------------------------
3268 Scavenging mutable lists.
3270 We treat the mutable list of each generation > N (i.e. all the
3271 generations older than the one being collected) as roots. We also
3272 remove non-mutable objects from the mutable list at this point.
3273 -------------------------------------------------------------------------- */
3276 scavenge_mut_once_list(generation *gen)
3278 const StgInfoTable *info;
3279 StgMutClosure *p, *next, *new_list;
3281 p = gen->mut_once_list;
3282 new_list = END_MUT_LIST;
3286 failed_to_evac = rtsFalse;
3288 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
3290 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3293 if (info->type==RBH)
3294 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3296 switch(info->type) {
3299 case IND_OLDGEN_PERM:
3301 /* Try to pull the indirectee into this generation, so we can
3302 * remove the indirection from the mutable list.
3304 ((StgIndOldGen *)p)->indirectee =
3305 evacuate(((StgIndOldGen *)p)->indirectee);
3307 #if 0 && defined(DEBUG)
3308 if (RtsFlags.DebugFlags.gc)
3309 /* Debugging code to print out the size of the thing we just
3313 StgPtr start = gen->steps[0].scan;
3314 bdescr *start_bd = gen->steps[0].scan_bd;
3316 scavenge(&gen->steps[0]);
3317 if (start_bd != gen->steps[0].scan_bd) {
3318 size += (P_)BLOCK_ROUND_UP(start) - start;
3319 start_bd = start_bd->link;
3320 while (start_bd != gen->steps[0].scan_bd) {
3321 size += BLOCK_SIZE_W;
3322 start_bd = start_bd->link;
3324 size += gen->steps[0].scan -
3325 (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
3327 size = gen->steps[0].scan - start;
3329 belch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
3333 /* failed_to_evac might happen if we've got more than two
3334 * generations, we're collecting only generation 0, the
3335 * indirection resides in generation 2 and the indirectee is
3338 if (failed_to_evac) {
3339 failed_to_evac = rtsFalse;
3340 p->mut_link = new_list;
3343 /* the mut_link field of an IND_STATIC is overloaded as the
3344 * static link field too (it just so happens that we don't need
3345 * both at the same time), so we need to NULL it out when
3346 * removing this object from the mutable list because the static
3347 * link fields are all assumed to be NULL before doing a major
3355 /* MUT_CONS is a kind of MUT_VAR, except it that we try to remove
3356 * it from the mutable list if possible by promoting whatever it
3359 if (scavenge_one((StgPtr)((StgMutVar *)p)->var)) {
3360 /* didn't manage to promote everything, so put the
3361 * MUT_CONS back on the list.
3363 p->mut_link = new_list;
3369 // shouldn't have anything else on the mutables list
3370 barf("scavenge_mut_once_list: strange object? %d", (int)(info->type));
3374 gen->mut_once_list = new_list;
3379 scavenge_mutable_list(generation *gen)
3381 const StgInfoTable *info;
3382 StgMutClosure *p, *next;
3384 p = gen->saved_mut_list;
3388 failed_to_evac = rtsFalse;
3390 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
3392 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3395 if (info->type==RBH)
3396 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3398 switch(info->type) {
3401 // follow everything
3402 p->mut_link = gen->mut_list;
3407 end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3408 for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
3409 (StgClosure *)*q = evacuate((StgClosure *)*q);
3414 // Happens if a MUT_ARR_PTRS in the old generation is frozen
3415 case MUT_ARR_PTRS_FROZEN:
3420 end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3421 for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
3422 (StgClosure *)*q = evacuate((StgClosure *)*q);
3425 // Set the mut_link field to NULL, so that we will put this
3426 // array back on the mutable list if it is subsequently thawed
3429 if (failed_to_evac) {
3430 failed_to_evac = rtsFalse;
3431 mkMutCons((StgClosure *)p, gen);
3437 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3438 p->mut_link = gen->mut_list;
3444 StgMVar *mvar = (StgMVar *)p;
3445 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
3446 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
3447 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
3448 p->mut_link = gen->mut_list;
3455 StgTSO *tso = (StgTSO *)p;
3459 /* Don't take this TSO off the mutable list - it might still
3460 * point to some younger objects (because we set evac_gen to 0
3463 tso->mut_link = gen->mut_list;
3464 gen->mut_list = (StgMutClosure *)tso;
3470 StgBlockingQueue *bh = (StgBlockingQueue *)p;
3471 (StgClosure *)bh->blocking_queue =
3472 evacuate((StgClosure *)bh->blocking_queue);
3473 p->mut_link = gen->mut_list;
3478 /* Happens if a BLACKHOLE_BQ in the old generation is updated:
3481 case IND_OLDGEN_PERM:
3482 /* Try to pull the indirectee into this generation, so we can
3483 * remove the indirection from the mutable list.
3486 ((StgIndOldGen *)p)->indirectee =
3487 evacuate(((StgIndOldGen *)p)->indirectee);
3490 if (failed_to_evac) {
3491 failed_to_evac = rtsFalse;
3492 p->mut_link = gen->mut_once_list;
3493 gen->mut_once_list = p;
3500 // HWL: check whether all of these are necessary
3502 case RBH: // cf. BLACKHOLE_BQ
3504 // nat size, ptrs, nonptrs, vhs;
3506 // StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3507 StgRBH *rbh = (StgRBH *)p;
3508 (StgClosure *)rbh->blocking_queue =
3509 evacuate((StgClosure *)rbh->blocking_queue);
3510 if (failed_to_evac) {
3511 failed_to_evac = rtsFalse;
3512 recordMutable((StgMutClosure *)rbh);
3514 // ToDo: use size of reverted closure here!
3515 p += BLACKHOLE_sizeW();
3521 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3522 // follow the pointer to the node which is being demanded
3523 (StgClosure *)bf->node =
3524 evacuate((StgClosure *)bf->node);
3525 // follow the link to the rest of the blocking queue
3526 (StgClosure *)bf->link =
3527 evacuate((StgClosure *)bf->link);
3528 if (failed_to_evac) {
3529 failed_to_evac = rtsFalse;
3530 recordMutable((StgMutClosure *)bf);
3532 p += sizeofW(StgBlockedFetch);
3538 barf("scavenge_mutable_list: REMOTE_REF %d", (int)(info->type));
3541 p += sizeofW(StgFetchMe);
3542 break; // nothing to do in this case
3544 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
3546 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3547 (StgClosure *)fmbq->blocking_queue =
3548 evacuate((StgClosure *)fmbq->blocking_queue);
3549 if (failed_to_evac) {
3550 failed_to_evac = rtsFalse;
3551 recordMutable((StgMutClosure *)fmbq);
3553 p += sizeofW(StgFetchMeBlockingQueue);
3559 // shouldn't have anything else on the mutables list
3560 barf("scavenge_mutable_list: strange object? %d", (int)(info->type));
3567 scavenge_static(void)
3569 StgClosure* p = static_objects;
3570 const StgInfoTable *info;
3572 /* Always evacuate straight to the oldest generation for static
3574 evac_gen = oldest_gen->no;
3576 /* keep going until we've scavenged all the objects on the linked
3578 while (p != END_OF_STATIC_LIST) {
3580 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3583 if (info->type==RBH)
3584 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3586 // make sure the info pointer is into text space
3588 /* Take this object *off* the static_objects list,
3589 * and put it on the scavenged_static_objects list.
3591 static_objects = STATIC_LINK(info,p);
3592 STATIC_LINK(info,p) = scavenged_static_objects;
3593 scavenged_static_objects = p;
3595 switch (info -> type) {
3599 StgInd *ind = (StgInd *)p;
3600 ind->indirectee = evacuate(ind->indirectee);
3602 /* might fail to evacuate it, in which case we have to pop it
3603 * back on the mutable list (and take it off the
3604 * scavenged_static list because the static link and mut link
3605 * pointers are one and the same).
3607 if (failed_to_evac) {
3608 failed_to_evac = rtsFalse;
3609 scavenged_static_objects = IND_STATIC_LINK(p);
3610 ((StgMutClosure *)ind)->mut_link = oldest_gen->mut_once_list;
3611 oldest_gen->mut_once_list = (StgMutClosure *)ind;
3617 scavenge_thunk_srt(info);
3621 scavenge_fun_srt(info);
3628 next = (P_)p->payload + info->layout.payload.ptrs;
3629 // evacuate the pointers
3630 for (q = (P_)p->payload; q < next; q++) {
3631 (StgClosure *)*q = evacuate((StgClosure *)*q);
3637 barf("scavenge_static: strange closure %d", (int)(info->type));
3640 ASSERT(failed_to_evac == rtsFalse);
3642 /* get the next static object from the list. Remember, there might
3643 * be more stuff on this list now that we've done some evacuating!
3644 * (static_objects is a global)
3650 /* -----------------------------------------------------------------------------
3651 scavenge a chunk of memory described by a bitmap
3652 -------------------------------------------------------------------------- */
3655 scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
3661 bitmap = large_bitmap->bitmap[b];
3662 for (i = 0; i < size; ) {
3663 if ((bitmap & 1) == 0) {
3664 (StgClosure *)*p = evacuate((StgClosure *)*p);
3668 if (i % BITS_IN(W_) == 0) {
3670 bitmap = large_bitmap->bitmap[b];
3672 bitmap = bitmap >> 1;
3677 STATIC_INLINE StgPtr
3678 scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap)
3681 if ((bitmap & 1) == 0) {
3682 (StgClosure *)*p = evacuate((StgClosure *)*p);
3685 bitmap = bitmap >> 1;
3691 /* -----------------------------------------------------------------------------
3692 scavenge_stack walks over a section of stack and evacuates all the
3693 objects pointed to by it. We can use the same code for walking
3694 AP_STACK_UPDs, since these are just sections of copied stack.
3695 -------------------------------------------------------------------------- */
3699 scavenge_stack(StgPtr p, StgPtr stack_end)
3701 const StgRetInfoTable* info;
3705 //IF_DEBUG(sanity, belch(" scavenging stack between %p and %p", p, stack_end));
3708 * Each time around this loop, we are looking at a chunk of stack
3709 * that starts with an activation record.
3712 while (p < stack_end) {
3713 info = get_ret_itbl((StgClosure *)p);
3715 switch (info->i.type) {
3718 ((StgUpdateFrame *)p)->updatee
3719 = evacuate(((StgUpdateFrame *)p)->updatee);
3720 p += sizeofW(StgUpdateFrame);
3723 // small bitmap (< 32 entries, or 64 on a 64-bit machine)
3728 bitmap = BITMAP_BITS(info->i.layout.bitmap);
3729 size = BITMAP_SIZE(info->i.layout.bitmap);
3730 // NOTE: the payload starts immediately after the info-ptr, we
3731 // don't have an StgHeader in the same sense as a heap closure.
3733 p = scavenge_small_bitmap(p, size, bitmap);
3736 scavenge_srt((StgClosure **)info->srt, info->i.srt_bitmap);
3744 (StgClosure *)*p = evacuate((StgClosure *)*p);
3747 size = BCO_BITMAP_SIZE(bco);
3748 scavenge_large_bitmap(p, BCO_BITMAP(bco), size);
3753 // large bitmap (> 32 entries, or > 64 on a 64-bit machine)
3759 size = info->i.layout.large_bitmap->size;
3761 scavenge_large_bitmap(p, info->i.layout.large_bitmap, size);
3763 // and don't forget to follow the SRT
3767 // Dynamic bitmap: the mask is stored on the stack, and
3768 // there are a number of non-pointers followed by a number
3769 // of pointers above the bitmapped area. (see StgMacros.h,
3774 dyn = ((StgRetDyn *)p)->liveness;
3776 // traverse the bitmap first
3777 bitmap = GET_LIVENESS(dyn);
3778 p = (P_)&((StgRetDyn *)p)->payload[0];
3779 size = RET_DYN_BITMAP_SIZE;
3780 p = scavenge_small_bitmap(p, size, bitmap);
3782 // skip over the non-ptr words
3783 p += GET_NONPTRS(dyn) + RET_DYN_NONPTR_REGS_SIZE;
3785 // follow the ptr words
3786 for (size = GET_PTRS(dyn); size > 0; size--) {
3787 (StgClosure *)*p = evacuate((StgClosure *)*p);
3795 StgRetFun *ret_fun = (StgRetFun *)p;
3796 StgFunInfoTable *fun_info;
3798 ret_fun->fun = evacuate(ret_fun->fun);
3799 fun_info = get_fun_itbl(ret_fun->fun);
3800 p = scavenge_arg_block(fun_info, ret_fun->payload);
3805 barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->i.type));
3810 /*-----------------------------------------------------------------------------
3811 scavenge the large object list.
3813 evac_gen set by caller; similar games played with evac_gen as with
3814 scavenge() - see comment at the top of scavenge(). Most large
3815 objects are (repeatedly) mutable, so most of the time evac_gen will
3817 --------------------------------------------------------------------------- */
3820 scavenge_large(step *stp)
3825 bd = stp->new_large_objects;
3827 for (; bd != NULL; bd = stp->new_large_objects) {
3829 /* take this object *off* the large objects list and put it on
3830 * the scavenged large objects list. This is so that we can
3831 * treat new_large_objects as a stack and push new objects on
3832 * the front when evacuating.
3834 stp->new_large_objects = bd->link;
3835 dbl_link_onto(bd, &stp->scavenged_large_objects);
3837 // update the block count in this step.
3838 stp->n_scavenged_large_blocks += bd->blocks;
3841 if (scavenge_one(p)) {
3842 mkMutCons((StgClosure *)p, stp->gen);
3847 /* -----------------------------------------------------------------------------
3848 Initialising the static object & mutable lists
3849 -------------------------------------------------------------------------- */
3852 zero_static_object_list(StgClosure* first_static)
3856 const StgInfoTable *info;
3858 for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
3860 link = STATIC_LINK(info, p);
3861 STATIC_LINK(info,p) = NULL;
3865 /* This function is only needed because we share the mutable link
3866 * field with the static link field in an IND_STATIC, so we have to
3867 * zero the mut_link field before doing a major GC, which needs the
3868 * static link field.
3870 * It doesn't do any harm to zero all the mutable link fields on the
3875 zero_mutable_list( StgMutClosure *first )
3877 StgMutClosure *next, *c;
3879 for (c = first; c != END_MUT_LIST; c = next) {
3885 /* -----------------------------------------------------------------------------
3887 -------------------------------------------------------------------------- */
3894 for (c = (StgIndStatic *)caf_list; c != NULL;
3895 c = (StgIndStatic *)c->static_link)
3897 c->header.info = c->saved_info;
3898 c->saved_info = NULL;
3899 // could, but not necessary: c->static_link = NULL;
3905 markCAFs( evac_fn evac )
3909 for (c = (StgIndStatic *)caf_list; c != NULL;
3910 c = (StgIndStatic *)c->static_link)
3912 evac(&c->indirectee);
3916 /* -----------------------------------------------------------------------------
3917 Sanity code for CAF garbage collection.
3919 With DEBUG turned on, we manage a CAF list in addition to the SRT
3920 mechanism. After GC, we run down the CAF list and blackhole any
3921 CAFs which have been garbage collected. This means we get an error
3922 whenever the program tries to enter a garbage collected CAF.
3924 Any garbage collected CAFs are taken off the CAF list at the same
3926 -------------------------------------------------------------------------- */
3928 #if 0 && defined(DEBUG)
3935 const StgInfoTable *info;
3946 ASSERT(info->type == IND_STATIC);
3948 if (STATIC_LINK(info,p) == NULL) {
3949 IF_DEBUG(gccafs, belch("CAF gc'd at 0x%04lx", (long)p));
3951 SET_INFO(p,&stg_BLACKHOLE_info);
3952 p = STATIC_LINK2(info,p);
3956 pp = &STATIC_LINK2(info,p);
3963 // belch("%d CAFs live", i);
3968 /* -----------------------------------------------------------------------------
3971 Whenever a thread returns to the scheduler after possibly doing
3972 some work, we have to run down the stack and black-hole all the
3973 closures referred to by update frames.
3974 -------------------------------------------------------------------------- */
3977 threadLazyBlackHole(StgTSO *tso)
3980 StgRetInfoTable *info;
3981 StgBlockingQueue *bh;
3984 stack_end = &tso->stack[tso->stack_size];
3986 frame = (StgClosure *)tso->sp;
3989 info = get_ret_itbl(frame);
3991 switch (info->i.type) {
3994 bh = (StgBlockingQueue *)((StgUpdateFrame *)frame)->updatee;
3996 /* if the thunk is already blackholed, it means we've also
3997 * already blackholed the rest of the thunks on this stack,
3998 * so we can stop early.
4000 * The blackhole made for a CAF is a CAF_BLACKHOLE, so they
4001 * don't interfere with this optimisation.
4003 if (bh->header.info == &stg_BLACKHOLE_info) {
4007 if (bh->header.info != &stg_BLACKHOLE_BQ_info &&
4008 bh->header.info != &stg_CAF_BLACKHOLE_info) {
4009 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4010 belch("Unexpected lazy BHing required at 0x%04x",(int)bh);
4014 // We pretend that bh is now dead.
4015 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4017 SET_INFO(bh,&stg_BLACKHOLE_info);
4020 // We pretend that bh has just been created.
4021 LDV_recordCreate(bh);
4025 frame = (StgClosure *) ((StgUpdateFrame *)frame + 1);
4031 // normal stack frames; do nothing except advance the pointer
4033 (StgPtr)frame += stack_frame_sizeW(frame);
4039 /* -----------------------------------------------------------------------------
4042 * Code largely pinched from old RTS, then hacked to bits. We also do
4043 * lazy black holing here.
4045 * -------------------------------------------------------------------------- */
4047 struct stack_gap { StgWord gap_size; struct stack_gap *next_gap; };
4050 threadSqueezeStack(StgTSO *tso)
4053 rtsBool prev_was_update_frame;
4054 StgClosure *updatee = NULL;
4056 StgRetInfoTable *info;
4057 StgWord current_gap_size;
4058 struct stack_gap *gap;
4061 // Traverse the stack upwards, replacing adjacent update frames
4062 // with a single update frame and a "stack gap". A stack gap
4063 // contains two values: the size of the gap, and the distance
4064 // to the next gap (or the stack top).
4066 bottom = &(tso->stack[tso->stack_size]);
4070 ASSERT(frame < bottom);
4072 prev_was_update_frame = rtsFalse;
4073 current_gap_size = 0;
4074 gap = (struct stack_gap *) (tso->sp - sizeofW(StgUpdateFrame));
4076 while (frame < bottom) {
4078 info = get_ret_itbl((StgClosure *)frame);
4079 switch (info->i.type) {
4083 StgUpdateFrame *upd = (StgUpdateFrame *)frame;
4085 if (upd->updatee->header.info == &stg_BLACKHOLE_info) {
4087 // found a BLACKHOLE'd update frame; we've been here
4088 // before, in a previous GC, so just break out.
4090 // Mark the end of the gap, if we're in one.
4091 if (current_gap_size != 0) {
4092 gap = (struct stack_gap *)(frame-sizeofW(StgUpdateFrame));
4095 frame += sizeofW(StgUpdateFrame);
4096 goto done_traversing;
4099 if (prev_was_update_frame) {
4101 TICK_UPD_SQUEEZED();
4102 /* wasn't there something about update squeezing and ticky to be
4103 * sorted out? oh yes: we aren't counting each enter properly
4104 * in this case. See the log somewhere. KSW 1999-04-21
4106 * Check two things: that the two update frames don't point to
4107 * the same object, and that the updatee_bypass isn't already an
4108 * indirection. Both of these cases only happen when we're in a
4109 * block hole-style loop (and there are multiple update frames
4110 * on the stack pointing to the same closure), but they can both
4111 * screw us up if we don't check.
4113 if (upd->updatee != updatee && !closure_IND(upd->updatee)) {
4114 // this wakes the threads up
4115 UPD_IND_NOLOCK(upd->updatee, updatee);
4118 // now mark this update frame as a stack gap. The gap
4119 // marker resides in the bottom-most update frame of
4120 // the series of adjacent frames, and covers all the
4121 // frames in this series.
4122 current_gap_size += sizeofW(StgUpdateFrame);
4123 ((struct stack_gap *)frame)->gap_size = current_gap_size;
4124 ((struct stack_gap *)frame)->next_gap = gap;
4126 frame += sizeofW(StgUpdateFrame);
4130 // single update frame, or the topmost update frame in a series
4132 StgBlockingQueue *bh = (StgBlockingQueue *)upd->updatee;
4134 // Do lazy black-holing
4135 if (bh->header.info != &stg_BLACKHOLE_info &&
4136 bh->header.info != &stg_BLACKHOLE_BQ_info &&
4137 bh->header.info != &stg_CAF_BLACKHOLE_info) {
4138 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4139 belch("Unexpected lazy BHing required at 0x%04x",(int)bh);
4142 /* zero out the slop so that the sanity checker can tell
4143 * where the next closure is.
4146 StgInfoTable *bh_info = get_itbl(bh);
4147 nat np = bh_info->layout.payload.ptrs,
4148 nw = bh_info->layout.payload.nptrs, i;
4149 /* don't zero out slop for a THUNK_SELECTOR,
4150 * because its layout info is used for a
4151 * different purpose, and it's exactly the
4152 * same size as a BLACKHOLE in any case.
4154 if (bh_info->type != THUNK_SELECTOR) {
4155 for (i = np; i < np + nw; i++) {
4156 ((StgClosure *)bh)->payload[i] = 0;
4162 // We pretend that bh is now dead.
4163 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4165 // Todo: maybe use SET_HDR() and remove LDV_recordCreate()?
4166 SET_INFO(bh,&stg_BLACKHOLE_info);
4168 // We pretend that bh has just been created.
4169 LDV_recordCreate(bh);
4173 prev_was_update_frame = rtsTrue;
4174 updatee = upd->updatee;
4175 frame += sizeofW(StgUpdateFrame);
4181 prev_was_update_frame = rtsFalse;
4183 // we're not in a gap... check whether this is the end of a gap
4184 // (an update frame can't be the end of a gap).
4185 if (current_gap_size != 0) {
4186 gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
4188 current_gap_size = 0;
4190 frame += stack_frame_sizeW((StgClosure *)frame);
4197 // Now we have a stack with gaps in it, and we have to walk down
4198 // shoving the stack up to fill in the gaps. A diagram might
4202 // | ********* | <- sp
4206 // | stack_gap | <- gap | chunk_size
4208 // | ......... | <- gap_end v
4214 // 'sp' points the the current top-of-stack
4215 // 'gap' points to the stack_gap structure inside the gap
4216 // ***** indicates real stack data
4217 // ..... indicates gap
4218 // <empty> indicates unused
4222 void *gap_start, *next_gap_start, *gap_end;
4225 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4226 sp = next_gap_start;
4228 while ((StgPtr)gap > tso->sp) {
4230 // we're working in *bytes* now...
4231 gap_start = next_gap_start;
4232 gap_end = (void*) ((unsigned char*)gap_start - gap->gap_size * sizeof(W_));
4234 gap = gap->next_gap;
4235 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4237 chunk_size = (unsigned char*)gap_end - (unsigned char*)next_gap_start;
4238 (unsigned char*)sp -= chunk_size;
4239 memmove(sp, next_gap_start, chunk_size);
4242 tso->sp = (StgPtr)sp;
4246 /* -----------------------------------------------------------------------------
4249 * We have to prepare for GC - this means doing lazy black holing
4250 * here. We also take the opportunity to do stack squeezing if it's
4252 * -------------------------------------------------------------------------- */
4254 threadPaused(StgTSO *tso)
4256 if ( RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue )
4257 threadSqueezeStack(tso); // does black holing too
4259 threadLazyBlackHole(tso);
4262 /* -----------------------------------------------------------------------------
4264 * -------------------------------------------------------------------------- */
4268 printMutOnceList(generation *gen)
4270 StgMutClosure *p, *next;
4272 p = gen->mut_once_list;
4275 fprintf(stderr, "@@ Mut once list %p: ", gen->mut_once_list);
4276 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
4277 fprintf(stderr, "%p (%s), ",
4278 p, info_type((StgClosure *)p));
4280 fputc('\n', stderr);
4284 printMutableList(generation *gen)
4286 StgMutClosure *p, *next;
4291 fprintf(stderr, "@@ Mutable list %p: ", gen->mut_list);
4292 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
4293 fprintf(stderr, "%p (%s), ",
4294 p, info_type((StgClosure *)p));
4296 fputc('\n', stderr);
4299 STATIC_INLINE rtsBool
4300 maybeLarge(StgClosure *closure)
4302 StgInfoTable *info = get_itbl(closure);
4304 /* closure types that may be found on the new_large_objects list;
4305 see scavenge_large */
4306 return (info->type == MUT_ARR_PTRS ||
4307 info->type == MUT_ARR_PTRS_FROZEN ||
4308 info->type == TSO ||
4309 info->type == ARR_WORDS);