1 /* -----------------------------------------------------------------------------
2 * $Id: GC.c,v 1.164 2003/11/26 12:14:26 simonmar 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
755 bd->flags |= BF_COMPACTED; // compacted next time
757 // tack the new blocks on the end of the existing blocks
758 if (stp->blocks == NULL) {
759 stp->blocks = stp->to_blocks;
761 for (bd = stp->blocks; bd != NULL; bd = next) {
764 bd->link = stp->to_blocks;
768 // add the new blocks to the block tally
769 stp->n_blocks += stp->n_to_blocks;
771 freeChain(stp->blocks);
772 stp->blocks = stp->to_blocks;
773 stp->n_blocks = stp->n_to_blocks;
774 for (bd = stp->blocks; bd != NULL; bd = bd->link) {
775 bd->flags &= ~BF_EVACUATED; // now from-space
778 stp->to_blocks = NULL;
779 stp->n_to_blocks = 0;
782 /* LARGE OBJECTS. The current live large objects are chained on
783 * scavenged_large, having been moved during garbage
784 * collection from large_objects. Any objects left on
785 * large_objects list are therefore dead, so we free them here.
787 for (bd = stp->large_objects; bd != NULL; bd = next) {
793 // update the count of blocks used by large objects
794 for (bd = stp->scavenged_large_objects; bd != NULL; bd = bd->link) {
795 bd->flags &= ~BF_EVACUATED;
797 stp->large_objects = stp->scavenged_large_objects;
798 stp->n_large_blocks = stp->n_scavenged_large_blocks;
801 // for older generations...
803 /* For older generations, we need to append the
804 * scavenged_large_object list (i.e. large objects that have been
805 * promoted during this GC) to the large_object list for that step.
807 for (bd = stp->scavenged_large_objects; bd; bd = next) {
809 bd->flags &= ~BF_EVACUATED;
810 dbl_link_onto(bd, &stp->large_objects);
813 // add the new blocks we promoted during this GC
814 stp->n_blocks += stp->n_to_blocks;
815 stp->n_to_blocks = 0;
816 stp->n_large_blocks += stp->n_scavenged_large_blocks;
821 /* Reset the sizes of the older generations when we do a major
824 * CURRENT STRATEGY: make all generations except zero the same size.
825 * We have to stay within the maximum heap size, and leave a certain
826 * percentage of the maximum heap size available to allocate into.
828 if (major_gc && RtsFlags.GcFlags.generations > 1) {
829 nat live, size, min_alloc;
830 nat max = RtsFlags.GcFlags.maxHeapSize;
831 nat gens = RtsFlags.GcFlags.generations;
833 // live in the oldest generations
834 live = oldest_gen->steps[0].n_blocks +
835 oldest_gen->steps[0].n_large_blocks;
837 // default max size for all generations except zero
838 size = stg_max(live * RtsFlags.GcFlags.oldGenFactor,
839 RtsFlags.GcFlags.minOldGenSize);
841 // minimum size for generation zero
842 min_alloc = stg_max((RtsFlags.GcFlags.pcFreeHeap * max) / 200,
843 RtsFlags.GcFlags.minAllocAreaSize);
845 // Auto-enable compaction when the residency reaches a
846 // certain percentage of the maximum heap size (default: 30%).
847 if (RtsFlags.GcFlags.generations > 1 &&
848 (RtsFlags.GcFlags.compact ||
850 oldest_gen->steps[0].n_blocks >
851 (RtsFlags.GcFlags.compactThreshold * max) / 100))) {
852 oldest_gen->steps[0].is_compacted = 1;
853 // fprintf(stderr,"compaction: on\n", live);
855 oldest_gen->steps[0].is_compacted = 0;
856 // fprintf(stderr,"compaction: off\n", live);
859 // if we're going to go over the maximum heap size, reduce the
860 // size of the generations accordingly. The calculation is
861 // different if compaction is turned on, because we don't need
862 // to double the space required to collect the old generation.
865 // this test is necessary to ensure that the calculations
866 // below don't have any negative results - we're working
867 // with unsigned values here.
868 if (max < min_alloc) {
872 if (oldest_gen->steps[0].is_compacted) {
873 if ( (size + (size - 1) * (gens - 2) * 2) + min_alloc > max ) {
874 size = (max - min_alloc) / ((gens - 1) * 2 - 1);
877 if ( (size * (gens - 1) * 2) + min_alloc > max ) {
878 size = (max - min_alloc) / ((gens - 1) * 2);
888 fprintf(stderr,"live: %d, min_alloc: %d, size : %d, max = %d\n", live,
889 min_alloc, size, max);
892 for (g = 0; g < gens; g++) {
893 generations[g].max_blocks = size;
897 // Guess the amount of live data for stats.
900 /* Free the small objects allocated via allocate(), since this will
901 * all have been copied into G0S1 now.
903 if (small_alloc_list != NULL) {
904 freeChain(small_alloc_list);
906 small_alloc_list = NULL;
910 alloc_blocks_lim = RtsFlags.GcFlags.minAllocAreaSize;
912 // Start a new pinned_object_block
913 pinned_object_block = NULL;
915 /* Free the mark stack.
917 if (mark_stack_bdescr != NULL) {
918 freeGroup(mark_stack_bdescr);
923 for (g = 0; g <= N; g++) {
924 for (s = 0; s < generations[g].n_steps; s++) {
925 stp = &generations[g].steps[s];
926 if (stp->is_compacted && stp->bitmap != NULL) {
927 freeGroup(stp->bitmap);
932 /* Two-space collector:
933 * Free the old to-space, and estimate the amount of live data.
935 if (RtsFlags.GcFlags.generations == 1) {
938 if (old_to_blocks != NULL) {
939 freeChain(old_to_blocks);
941 for (bd = g0s0->to_blocks; bd != NULL; bd = bd->link) {
942 bd->flags = 0; // now from-space
945 /* For a two-space collector, we need to resize the nursery. */
947 /* set up a new nursery. Allocate a nursery size based on a
948 * function of the amount of live data (by default a factor of 2)
949 * Use the blocks from the old nursery if possible, freeing up any
952 * If we get near the maximum heap size, then adjust our nursery
953 * size accordingly. If the nursery is the same size as the live
954 * data (L), then we need 3L bytes. We can reduce the size of the
955 * nursery to bring the required memory down near 2L bytes.
957 * A normal 2-space collector would need 4L bytes to give the same
958 * performance we get from 3L bytes, reducing to the same
959 * performance at 2L bytes.
961 blocks = g0s0->n_to_blocks;
963 if ( RtsFlags.GcFlags.maxHeapSize != 0 &&
964 blocks * RtsFlags.GcFlags.oldGenFactor * 2 >
965 RtsFlags.GcFlags.maxHeapSize ) {
966 long adjusted_blocks; // signed on purpose
969 adjusted_blocks = (RtsFlags.GcFlags.maxHeapSize - 2 * blocks);
970 IF_DEBUG(gc, belch("@@ Near maximum heap size of 0x%x blocks, blocks = %d, adjusted to %ld", RtsFlags.GcFlags.maxHeapSize, blocks, adjusted_blocks));
971 pc_free = adjusted_blocks * 100 / RtsFlags.GcFlags.maxHeapSize;
972 if (pc_free < RtsFlags.GcFlags.pcFreeHeap) /* might even be < 0 */ {
975 blocks = adjusted_blocks;
978 blocks *= RtsFlags.GcFlags.oldGenFactor;
979 if (blocks < RtsFlags.GcFlags.minAllocAreaSize) {
980 blocks = RtsFlags.GcFlags.minAllocAreaSize;
983 resizeNursery(blocks);
986 /* Generational collector:
987 * If the user has given us a suggested heap size, adjust our
988 * allocation area to make best use of the memory available.
991 if (RtsFlags.GcFlags.heapSizeSuggestion) {
993 nat needed = calcNeeded(); // approx blocks needed at next GC
995 /* Guess how much will be live in generation 0 step 0 next time.
996 * A good approximation is obtained by finding the
997 * percentage of g0s0 that was live at the last minor GC.
1000 g0s0_pcnt_kept = (new_blocks * 100) / g0s0->n_blocks;
1003 /* Estimate a size for the allocation area based on the
1004 * information available. We might end up going slightly under
1005 * or over the suggested heap size, but we should be pretty
1008 * Formula: suggested - needed
1009 * ----------------------------
1010 * 1 + g0s0_pcnt_kept/100
1012 * where 'needed' is the amount of memory needed at the next
1013 * collection for collecting all steps except g0s0.
1016 (((long)RtsFlags.GcFlags.heapSizeSuggestion - (long)needed) * 100) /
1017 (100 + (long)g0s0_pcnt_kept);
1019 if (blocks < (long)RtsFlags.GcFlags.minAllocAreaSize) {
1020 blocks = RtsFlags.GcFlags.minAllocAreaSize;
1023 resizeNursery((nat)blocks);
1026 // we might have added extra large blocks to the nursery, so
1027 // resize back to minAllocAreaSize again.
1028 resizeNursery(RtsFlags.GcFlags.minAllocAreaSize);
1032 // mark the garbage collected CAFs as dead
1033 #if 0 && defined(DEBUG) // doesn't work at the moment
1034 if (major_gc) { gcCAFs(); }
1038 // resetStaticObjectForRetainerProfiling() must be called before
1040 resetStaticObjectForRetainerProfiling();
1043 // zero the scavenged static object list
1045 zero_static_object_list(scavenged_static_objects);
1048 // Reset the nursery
1051 RELEASE_LOCK(&sched_mutex);
1053 // start any pending finalizers
1054 scheduleFinalizers(old_weak_ptr_list);
1056 // send exceptions to any threads which were about to die
1057 resurrectThreads(resurrected_threads);
1059 ACQUIRE_LOCK(&sched_mutex);
1061 // Update the stable pointer hash table.
1062 updateStablePtrTable(major_gc);
1064 // check sanity after GC
1065 IF_DEBUG(sanity, checkSanity());
1067 // extra GC trace info
1068 IF_DEBUG(gc, statDescribeGens());
1071 // symbol-table based profiling
1072 /* heapCensus(to_blocks); */ /* ToDo */
1075 // restore enclosing cost centre
1080 // check for memory leaks if sanity checking is on
1081 IF_DEBUG(sanity, memInventory());
1083 #ifdef RTS_GTK_FRONTPANEL
1084 if (RtsFlags.GcFlags.frontpanel) {
1085 updateFrontPanelAfterGC( N, live );
1089 // ok, GC over: tell the stats department what happened.
1090 stat_endGC(allocated, collected, live, copied, N);
1092 #if defined(RTS_USER_SIGNALS)
1093 // unblock signals again
1094 unblockUserSignals();
1101 /* -----------------------------------------------------------------------------
1104 traverse_weak_ptr_list is called possibly many times during garbage
1105 collection. It returns a flag indicating whether it did any work
1106 (i.e. called evacuate on any live pointers).
1108 Invariant: traverse_weak_ptr_list is called when the heap is in an
1109 idempotent state. That means that there are no pending
1110 evacuate/scavenge operations. This invariant helps the weak
1111 pointer code decide which weak pointers are dead - if there are no
1112 new live weak pointers, then all the currently unreachable ones are
1115 For generational GC: we just don't try to finalize weak pointers in
1116 older generations than the one we're collecting. This could
1117 probably be optimised by keeping per-generation lists of weak
1118 pointers, but for a few weak pointers this scheme will work.
1120 There are three distinct stages to processing weak pointers:
1122 - weak_stage == WeakPtrs
1124 We process all the weak pointers whos keys are alive (evacuate
1125 their values and finalizers), and repeat until we can find no new
1126 live keys. If no live keys are found in this pass, then we
1127 evacuate the finalizers of all the dead weak pointers in order to
1130 - weak_stage == WeakThreads
1132 Now, we discover which *threads* are still alive. Pointers to
1133 threads from the all_threads and main thread lists are the
1134 weakest of all: a pointers from the finalizer of a dead weak
1135 pointer can keep a thread alive. Any threads found to be unreachable
1136 are evacuated and placed on the resurrected_threads list so we
1137 can send them a signal later.
1139 - weak_stage == WeakDone
1141 No more evacuation is done.
1143 -------------------------------------------------------------------------- */
1146 traverse_weak_ptr_list(void)
1148 StgWeak *w, **last_w, *next_w;
1150 rtsBool flag = rtsFalse;
1152 switch (weak_stage) {
1158 /* doesn't matter where we evacuate values/finalizers to, since
1159 * these pointers are treated as roots (iff the keys are alive).
1163 last_w = &old_weak_ptr_list;
1164 for (w = old_weak_ptr_list; w != NULL; w = next_w) {
1166 /* There might be a DEAD_WEAK on the list if finalizeWeak# was
1167 * called on a live weak pointer object. Just remove it.
1169 if (w->header.info == &stg_DEAD_WEAK_info) {
1170 next_w = ((StgDeadWeak *)w)->link;
1175 switch (get_itbl(w)->type) {
1178 next_w = (StgWeak *)((StgEvacuated *)w)->evacuee;
1183 /* Now, check whether the key is reachable.
1185 new = isAlive(w->key);
1188 // evacuate the value and finalizer
1189 w->value = evacuate(w->value);
1190 w->finalizer = evacuate(w->finalizer);
1191 // remove this weak ptr from the old_weak_ptr list
1193 // and put it on the new weak ptr list
1195 w->link = weak_ptr_list;
1198 IF_DEBUG(weak, belch("Weak pointer still alive at %p -> %p",
1203 last_w = &(w->link);
1209 barf("traverse_weak_ptr_list: not WEAK");
1213 /* If we didn't make any changes, then we can go round and kill all
1214 * the dead weak pointers. The old_weak_ptr list is used as a list
1215 * of pending finalizers later on.
1217 if (flag == rtsFalse) {
1218 for (w = old_weak_ptr_list; w; w = w->link) {
1219 w->finalizer = evacuate(w->finalizer);
1222 // Next, move to the WeakThreads stage after fully
1223 // scavenging the finalizers we've just evacuated.
1224 weak_stage = WeakThreads;
1230 /* Now deal with the all_threads list, which behaves somewhat like
1231 * the weak ptr list. If we discover any threads that are about to
1232 * become garbage, we wake them up and administer an exception.
1235 StgTSO *t, *tmp, *next, **prev;
1237 prev = &old_all_threads;
1238 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1240 (StgClosure *)tmp = isAlive((StgClosure *)t);
1246 ASSERT(get_itbl(t)->type == TSO);
1247 switch (t->what_next) {
1248 case ThreadRelocated:
1253 case ThreadComplete:
1254 // finshed or died. The thread might still be alive, but we
1255 // don't keep it on the all_threads list. Don't forget to
1256 // stub out its global_link field.
1257 next = t->global_link;
1258 t->global_link = END_TSO_QUEUE;
1266 // not alive (yet): leave this thread on the
1267 // old_all_threads list.
1268 prev = &(t->global_link);
1269 next = t->global_link;
1272 // alive: move this thread onto the all_threads list.
1273 next = t->global_link;
1274 t->global_link = all_threads;
1281 /* And resurrect any threads which were about to become garbage.
1284 StgTSO *t, *tmp, *next;
1285 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1286 next = t->global_link;
1287 (StgClosure *)tmp = evacuate((StgClosure *)t);
1288 tmp->global_link = resurrected_threads;
1289 resurrected_threads = tmp;
1293 weak_stage = WeakDone; // *now* we're done,
1294 return rtsTrue; // but one more round of scavenging, please
1297 barf("traverse_weak_ptr_list");
1303 /* -----------------------------------------------------------------------------
1304 After GC, the live weak pointer list may have forwarding pointers
1305 on it, because a weak pointer object was evacuated after being
1306 moved to the live weak pointer list. We remove those forwarding
1309 Also, we don't consider weak pointer objects to be reachable, but
1310 we must nevertheless consider them to be "live" and retain them.
1311 Therefore any weak pointer objects which haven't as yet been
1312 evacuated need to be evacuated now.
1313 -------------------------------------------------------------------------- */
1317 mark_weak_ptr_list ( StgWeak **list )
1319 StgWeak *w, **last_w;
1322 for (w = *list; w; w = w->link) {
1323 // w might be WEAK, EVACUATED, or DEAD_WEAK (actually CON_STATIC) here
1324 ASSERT(w->header.info == &stg_DEAD_WEAK_info
1325 || get_itbl(w)->type == WEAK || get_itbl(w)->type == EVACUATED);
1326 (StgClosure *)w = evacuate((StgClosure *)w);
1328 last_w = &(w->link);
1332 /* -----------------------------------------------------------------------------
1333 isAlive determines whether the given closure is still alive (after
1334 a garbage collection) or not. It returns the new address of the
1335 closure if it is alive, or NULL otherwise.
1337 NOTE: Use it before compaction only!
1338 -------------------------------------------------------------------------- */
1342 isAlive(StgClosure *p)
1344 const StgInfoTable *info;
1349 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
1352 // ignore static closures
1354 // ToDo: for static closures, check the static link field.
1355 // Problem here is that we sometimes don't set the link field, eg.
1356 // for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
1358 if (!HEAP_ALLOCED(p)) {
1362 // ignore closures in generations that we're not collecting.
1364 if (bd->gen_no > N) {
1368 // if it's a pointer into to-space, then we're done
1369 if (bd->flags & BF_EVACUATED) {
1373 // large objects use the evacuated flag
1374 if (bd->flags & BF_LARGE) {
1378 // check the mark bit for compacted steps
1379 if ((bd->flags & BF_COMPACTED) && is_marked((P_)p,bd)) {
1383 switch (info->type) {
1388 case IND_OLDGEN: // rely on compatible layout with StgInd
1389 case IND_OLDGEN_PERM:
1390 // follow indirections
1391 p = ((StgInd *)p)->indirectee;
1396 return ((StgEvacuated *)p)->evacuee;
1399 if (((StgTSO *)p)->what_next == ThreadRelocated) {
1400 p = (StgClosure *)((StgTSO *)p)->link;
1413 mark_root(StgClosure **root)
1415 *root = evacuate(*root);
1419 upd_evacuee(StgClosure *p, StgClosure *dest)
1421 // Source object must be in from-space:
1422 ASSERT((Bdescr((P_)p)->flags & BF_EVACUATED) == 0);
1423 // not true: (ToDo: perhaps it should be)
1424 // ASSERT(Bdescr((P_)dest)->flags & BF_EVACUATED);
1425 p->header.info = &stg_EVACUATED_info;
1426 ((StgEvacuated *)p)->evacuee = dest;
1430 STATIC_INLINE StgClosure *
1431 copy(StgClosure *src, nat size, step *stp)
1436 nat size_org = size;
1439 TICK_GC_WORDS_COPIED(size);
1440 /* Find out where we're going, using the handy "to" pointer in
1441 * the step of the source object. If it turns out we need to
1442 * evacuate to an older generation, adjust it here (see comment
1445 if (stp->gen_no < evac_gen) {
1446 #ifdef NO_EAGER_PROMOTION
1447 failed_to_evac = rtsTrue;
1449 stp = &generations[evac_gen].steps[0];
1453 /* chain a new block onto the to-space for the destination step if
1456 if (stp->hp + size >= stp->hpLim) {
1457 gc_alloc_block(stp);
1460 for(to = stp->hp, from = (P_)src; size>0; --size) {
1466 upd_evacuee(src,(StgClosure *)dest);
1468 // We store the size of the just evacuated object in the LDV word so that
1469 // the profiler can guess the position of the next object later.
1470 SET_EVACUAEE_FOR_LDV(src, size_org);
1472 return (StgClosure *)dest;
1475 /* Special version of copy() for when we only want to copy the info
1476 * pointer of an object, but reserve some padding after it. This is
1477 * used to optimise evacuation of BLACKHOLEs.
1482 copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *stp)
1487 nat size_to_copy_org = size_to_copy;
1490 TICK_GC_WORDS_COPIED(size_to_copy);
1491 if (stp->gen_no < evac_gen) {
1492 #ifdef NO_EAGER_PROMOTION
1493 failed_to_evac = rtsTrue;
1495 stp = &generations[evac_gen].steps[0];
1499 if (stp->hp + size_to_reserve >= stp->hpLim) {
1500 gc_alloc_block(stp);
1503 for(to = stp->hp, from = (P_)src; size_to_copy>0; --size_to_copy) {
1508 stp->hp += size_to_reserve;
1509 upd_evacuee(src,(StgClosure *)dest);
1511 // We store the size of the just evacuated object in the LDV word so that
1512 // the profiler can guess the position of the next object later.
1513 // size_to_copy_org is wrong because the closure already occupies size_to_reserve
1515 SET_EVACUAEE_FOR_LDV(src, size_to_reserve);
1517 if (size_to_reserve - size_to_copy_org > 0)
1518 FILL_SLOP(stp->hp - 1, (int)(size_to_reserve - size_to_copy_org));
1520 return (StgClosure *)dest;
1524 /* -----------------------------------------------------------------------------
1525 Evacuate a large object
1527 This just consists of removing the object from the (doubly-linked)
1528 step->large_objects list, and linking it on to the (singly-linked)
1529 step->new_large_objects list, from where it will be scavenged later.
1531 Convention: bd->flags has BF_EVACUATED set for a large object
1532 that has been evacuated, or unset otherwise.
1533 -------------------------------------------------------------------------- */
1537 evacuate_large(StgPtr p)
1539 bdescr *bd = Bdescr(p);
1542 // object must be at the beginning of the block (or be a ByteArray)
1543 ASSERT(get_itbl((StgClosure *)p)->type == ARR_WORDS ||
1544 (((W_)p & BLOCK_MASK) == 0));
1546 // already evacuated?
1547 if (bd->flags & BF_EVACUATED) {
1548 /* Don't forget to set the failed_to_evac flag if we didn't get
1549 * the desired destination (see comments in evacuate()).
1551 if (bd->gen_no < evac_gen) {
1552 failed_to_evac = rtsTrue;
1553 TICK_GC_FAILED_PROMOTION();
1559 // remove from large_object list
1561 bd->u.back->link = bd->link;
1562 } else { // first object in the list
1563 stp->large_objects = bd->link;
1566 bd->link->u.back = bd->u.back;
1569 /* link it on to the evacuated large object list of the destination step
1572 if (stp->gen_no < evac_gen) {
1573 #ifdef NO_EAGER_PROMOTION
1574 failed_to_evac = rtsTrue;
1576 stp = &generations[evac_gen].steps[0];
1581 bd->gen_no = stp->gen_no;
1582 bd->link = stp->new_large_objects;
1583 stp->new_large_objects = bd;
1584 bd->flags |= BF_EVACUATED;
1587 /* -----------------------------------------------------------------------------
1588 Adding a MUT_CONS to an older generation.
1590 This is necessary from time to time when we end up with an
1591 old-to-new generation pointer in a non-mutable object. We defer
1592 the promotion until the next GC.
1593 -------------------------------------------------------------------------- */
1596 mkMutCons(StgClosure *ptr, generation *gen)
1601 stp = &gen->steps[0];
1603 /* chain a new block onto the to-space for the destination step if
1606 if (stp->hp + sizeofW(StgIndOldGen) >= stp->hpLim) {
1607 gc_alloc_block(stp);
1610 q = (StgMutVar *)stp->hp;
1611 stp->hp += sizeofW(StgMutVar);
1613 SET_HDR(q,&stg_MUT_CONS_info,CCS_GC);
1615 recordOldToNewPtrs((StgMutClosure *)q);
1617 return (StgClosure *)q;
1620 /* -----------------------------------------------------------------------------
1623 This is called (eventually) for every live object in the system.
1625 The caller to evacuate specifies a desired generation in the
1626 evac_gen global variable. The following conditions apply to
1627 evacuating an object which resides in generation M when we're
1628 collecting up to generation N
1632 else evac to step->to
1634 if M < evac_gen evac to evac_gen, step 0
1636 if the object is already evacuated, then we check which generation
1639 if M >= evac_gen do nothing
1640 if M < evac_gen set failed_to_evac flag to indicate that we
1641 didn't manage to evacuate this object into evac_gen.
1646 evacuate() is the single most important function performance-wise
1647 in the GC. Various things have been tried to speed it up, but as
1648 far as I can tell the code generated by gcc 3.2 with -O2 is about
1649 as good as it's going to get. We pass the argument to evacuate()
1650 in a register using the 'regparm' attribute (see the prototype for
1651 evacuate() near the top of this file).
1653 Changing evacuate() to take an (StgClosure **) rather than
1654 returning the new pointer seems attractive, because we can avoid
1655 writing back the pointer when it hasn't changed (eg. for a static
1656 object, or an object in a generation > N). However, I tried it and
1657 it doesn't help. One reason is that the (StgClosure **) pointer
1658 gets spilled to the stack inside evacuate(), resulting in far more
1659 extra reads/writes than we save.
1660 -------------------------------------------------------------------------- */
1663 evacuate(StgClosure *q)
1668 const StgInfoTable *info;
1671 if (HEAP_ALLOCED(q)) {
1674 if (bd->gen_no > N) {
1675 /* Can't evacuate this object, because it's in a generation
1676 * older than the ones we're collecting. Let's hope that it's
1677 * in evac_gen or older, or we will have to arrange to track
1678 * this pointer using the mutable list.
1680 if (bd->gen_no < evac_gen) {
1682 failed_to_evac = rtsTrue;
1683 TICK_GC_FAILED_PROMOTION();
1688 /* evacuate large objects by re-linking them onto a different list.
1690 if (bd->flags & BF_LARGE) {
1692 if (info->type == TSO &&
1693 ((StgTSO *)q)->what_next == ThreadRelocated) {
1694 q = (StgClosure *)((StgTSO *)q)->link;
1697 evacuate_large((P_)q);
1701 /* If the object is in a step that we're compacting, then we
1702 * need to use an alternative evacuate procedure.
1704 if (bd->flags & BF_COMPACTED) {
1705 if (!is_marked((P_)q,bd)) {
1707 if (mark_stack_full()) {
1708 mark_stack_overflowed = rtsTrue;
1711 push_mark_stack((P_)q);
1719 else stp = NULL; // make sure copy() will crash if HEAP_ALLOCED is wrong
1722 // make sure the info pointer is into text space
1723 ASSERT(LOOKS_LIKE_CLOSURE_PTR(q));
1726 switch (info -> type) {
1730 return copy(q,sizeW_fromITBL(info),stp);
1734 StgWord w = (StgWord)q->payload[0];
1735 if (q->header.info == Czh_con_info &&
1736 // unsigned, so always true: (StgChar)w >= MIN_CHARLIKE &&
1737 (StgChar)w <= MAX_CHARLIKE) {
1738 return (StgClosure *)CHARLIKE_CLOSURE((StgChar)w);
1740 if (q->header.info == Izh_con_info &&
1741 (StgInt)w >= MIN_INTLIKE && (StgInt)w <= MAX_INTLIKE) {
1742 return (StgClosure *)INTLIKE_CLOSURE((StgInt)w);
1744 // else, fall through ...
1750 return copy(q,sizeofW(StgHeader)+1,stp);
1752 case THUNK_1_0: // here because of MIN_UPD_SIZE
1757 #ifdef NO_PROMOTE_THUNKS
1758 if (bd->gen_no == 0 &&
1759 bd->step->no != 0 &&
1760 bd->step->no == generations[bd->gen_no].n_steps-1) {
1764 return copy(q,sizeofW(StgHeader)+2,stp);
1772 return copy(q,sizeofW(StgHeader)+2,stp);
1778 case IND_OLDGEN_PERM:
1782 return copy(q,sizeW_fromITBL(info),stp);
1785 return copy(q,bco_sizeW((StgBCO *)q),stp);
1788 case SE_CAF_BLACKHOLE:
1791 return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
1794 to = copy(q,BLACKHOLE_sizeW(),stp);
1797 case THUNK_SELECTOR:
1801 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
1802 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1805 p = eval_thunk_selector(info->layout.selector_offset,
1809 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1811 // q is still BLACKHOLE'd.
1812 thunk_selector_depth++;
1814 thunk_selector_depth--;
1817 // We store the size of the just evacuated object in the
1818 // LDV word so that the profiler can guess the position of
1819 // the next object later.
1820 SET_EVACUAEE_FOR_LDV(q, THUNK_SELECTOR_sizeW());
1828 // follow chains of indirections, don't evacuate them
1829 q = ((StgInd*)q)->indirectee;
1833 if (info->srt_bitmap != 0 && major_gc &&
1834 THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
1835 THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
1836 static_objects = (StgClosure *)q;
1841 if (info->srt_bitmap != 0 && major_gc &&
1842 FUN_STATIC_LINK((StgClosure *)q) == NULL) {
1843 FUN_STATIC_LINK((StgClosure *)q) = static_objects;
1844 static_objects = (StgClosure *)q;
1849 /* If q->saved_info != NULL, then it's a revertible CAF - it'll be
1850 * on the CAF list, so don't do anything with it here (we'll
1851 * scavenge it later).
1854 && ((StgIndStatic *)q)->saved_info == NULL
1855 && IND_STATIC_LINK((StgClosure *)q) == NULL) {
1856 IND_STATIC_LINK((StgClosure *)q) = static_objects;
1857 static_objects = (StgClosure *)q;
1862 if (major_gc && STATIC_LINK(info,(StgClosure *)q) == NULL) {
1863 STATIC_LINK(info,(StgClosure *)q) = static_objects;
1864 static_objects = (StgClosure *)q;
1868 case CONSTR_INTLIKE:
1869 case CONSTR_CHARLIKE:
1870 case CONSTR_NOCAF_STATIC:
1871 /* no need to put these on the static linked list, they don't need
1885 // shouldn't see these
1886 barf("evacuate: stack frame at %p\n", q);
1890 return copy(q,pap_sizeW((StgPAP*)q),stp);
1893 return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp);
1896 /* Already evacuated, just return the forwarding address.
1897 * HOWEVER: if the requested destination generation (evac_gen) is
1898 * older than the actual generation (because the object was
1899 * already evacuated to a younger generation) then we have to
1900 * set the failed_to_evac flag to indicate that we couldn't
1901 * manage to promote the object to the desired generation.
1903 if (evac_gen > 0) { // optimisation
1904 StgClosure *p = ((StgEvacuated*)q)->evacuee;
1905 if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < evac_gen) {
1906 failed_to_evac = rtsTrue;
1907 TICK_GC_FAILED_PROMOTION();
1910 return ((StgEvacuated*)q)->evacuee;
1913 // just copy the block
1914 return copy(q,arr_words_sizeW((StgArrWords *)q),stp);
1917 case MUT_ARR_PTRS_FROZEN:
1918 // just copy the block
1919 return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
1923 StgTSO *tso = (StgTSO *)q;
1925 /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
1927 if (tso->what_next == ThreadRelocated) {
1928 q = (StgClosure *)tso->link;
1932 /* To evacuate a small TSO, we need to relocate the update frame
1939 new_tso = (StgTSO *)copyPart((StgClosure *)tso,
1941 sizeofW(StgTSO), stp);
1942 move_TSO(tso, new_tso);
1943 for (p = tso->sp, q = new_tso->sp;
1944 p < tso->stack+tso->stack_size;) {
1948 return (StgClosure *)new_tso;
1953 case RBH: // cf. BLACKHOLE_BQ
1955 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
1956 to = copy(q,BLACKHOLE_sizeW(),stp);
1957 //ToDo: derive size etc from reverted IP
1958 //to = copy(q,size,stp);
1960 belch("@@ evacuate: RBH %p (%s) to %p (%s)",
1961 q, info_type(q), to, info_type(to)));
1966 ASSERT(sizeofW(StgBlockedFetch) >= MIN_NONUPD_SIZE);
1967 to = copy(q,sizeofW(StgBlockedFetch),stp);
1969 belch("@@ evacuate: %p (%s) to %p (%s)",
1970 q, info_type(q), to, info_type(to)));
1977 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1978 to = copy(q,sizeofW(StgFetchMe),stp);
1980 belch("@@ evacuate: %p (%s) to %p (%s)",
1981 q, info_type(q), to, info_type(to)));
1985 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1986 to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
1988 belch("@@ evacuate: %p (%s) to %p (%s)",
1989 q, info_type(q), to, info_type(to)));
1994 barf("evacuate: strange closure type %d", (int)(info->type));
2000 /* -----------------------------------------------------------------------------
2001 Evaluate a THUNK_SELECTOR if possible.
2003 returns: NULL if we couldn't evaluate this THUNK_SELECTOR, or
2004 a closure pointer if we evaluated it and this is the result. Note
2005 that "evaluating" the THUNK_SELECTOR doesn't necessarily mean
2006 reducing it to HNF, just that we have eliminated the selection.
2007 The result might be another thunk, or even another THUNK_SELECTOR.
2009 If the return value is non-NULL, the original selector thunk has
2010 been BLACKHOLE'd, and should be updated with an indirection or a
2011 forwarding pointer. If the return value is NULL, then the selector
2013 -------------------------------------------------------------------------- */
2016 eval_thunk_selector( nat field, StgSelector * p )
2019 const StgInfoTable *info_ptr;
2020 StgClosure *selectee;
2023 selectee = p->selectee;
2025 // Save the real info pointer (NOTE: not the same as get_itbl()).
2026 info_ptr = p->header.info;
2028 // If the THUNK_SELECTOR is in a generation that we are not
2029 // collecting, then bail out early. We won't be able to save any
2030 // space in any case, and updating with an indirection is trickier
2032 if (Bdescr((StgPtr)p)->gen_no > N) {
2036 // BLACKHOLE the selector thunk, since it is now under evaluation.
2037 // This is important to stop us going into an infinite loop if
2038 // this selector thunk eventually refers to itself.
2039 SET_INFO(p,&stg_BLACKHOLE_info);
2043 // We don't want to end up in to-space, because this causes
2044 // problems when the GC later tries to evacuate the result of
2045 // eval_thunk_selector(). There are various ways this could
2048 // 1. following an IND_STATIC
2050 // 2. when the old generation is compacted, the mark phase updates
2051 // from-space pointers to be to-space pointers, and we can't
2052 // reliably tell which we're following (eg. from an IND_STATIC).
2054 // 3. compacting GC again: if we're looking at a constructor in
2055 // the compacted generation, it might point directly to objects
2056 // in to-space. We must bale out here, otherwise doing the selection
2057 // will result in a to-space pointer being returned.
2059 // (1) is dealt with using a BF_EVACUATED test on the
2060 // selectee. (2) and (3): we can tell if we're looking at an
2061 // object in the compacted generation that might point to
2062 // to-space objects by testing that (a) it is BF_COMPACTED, (b)
2063 // the compacted generation is being collected, and (c) the
2064 // object is marked. Only a marked object may have pointers that
2065 // point to to-space objects, because that happens when
2068 bd = Bdescr((StgPtr)selectee);
2069 if (HEAP_ALLOCED(selectee) &&
2070 ((bd->flags & BF_EVACUATED)
2071 || ((bd->flags & BF_COMPACTED) &&
2073 is_marked((P_)selectee,bd)))) {
2077 info = get_itbl(selectee);
2078 switch (info->type) {
2086 case CONSTR_NOCAF_STATIC:
2087 // check that the size is in range
2088 ASSERT(field < (StgWord32)(info->layout.payload.ptrs +
2089 info->layout.payload.nptrs));
2091 // ToDo: shouldn't we test whether this pointer is in
2093 return selectee->payload[field];
2098 case IND_OLDGEN_PERM:
2100 selectee = ((StgInd *)selectee)->indirectee;
2104 // We don't follow pointers into to-space; the constructor
2105 // has already been evacuated, so we won't save any space
2106 // leaks by evaluating this selector thunk anyhow.
2109 case THUNK_SELECTOR:
2113 // check that we don't recurse too much, re-using the
2114 // depth bound also used in evacuate().
2115 thunk_selector_depth++;
2116 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
2120 val = eval_thunk_selector(info->layout.selector_offset,
2121 (StgSelector *)selectee);
2123 thunk_selector_depth--;
2128 // We evaluated this selector thunk, so update it with
2129 // an indirection. NOTE: we don't use UPD_IND here,
2130 // because we are guaranteed that p is in a generation
2131 // that we are collecting, and we never want to put the
2132 // indirection on a mutable list.
2134 // For the purposes of LDV profiling, we have destroyed
2135 // the original selector thunk.
2136 SET_INFO(p, info_ptr);
2137 LDV_recordDead_FILL_SLOP_DYNAMIC(selectee);
2139 ((StgInd *)selectee)->indirectee = val;
2140 SET_INFO(selectee,&stg_IND_info);
2142 // For the purposes of LDV profiling, we have created an
2144 LDV_recordCreate(selectee);
2161 case SE_CAF_BLACKHOLE:
2174 // not evaluated yet
2178 barf("eval_thunk_selector: strange selectee %d",
2183 // We didn't manage to evaluate this thunk; restore the old info pointer
2184 SET_INFO(p, info_ptr);
2188 /* -----------------------------------------------------------------------------
2189 move_TSO is called to update the TSO structure after it has been
2190 moved from one place to another.
2191 -------------------------------------------------------------------------- */
2194 move_TSO (StgTSO *src, StgTSO *dest)
2198 // relocate the stack pointer...
2199 diff = (StgPtr)dest - (StgPtr)src; // In *words*
2200 dest->sp = (StgPtr)dest->sp + diff;
2203 /* Similar to scavenge_large_bitmap(), but we don't write back the
2204 * pointers we get back from evacuate().
2207 scavenge_large_srt_bitmap( StgLargeSRT *large_srt )
2214 bitmap = large_srt->l.bitmap[b];
2215 size = (nat)large_srt->l.size;
2216 p = (StgClosure **)large_srt->srt;
2217 for (i = 0; i < size; ) {
2218 if ((bitmap & 1) != 0) {
2223 if (i % BITS_IN(W_) == 0) {
2225 bitmap = large_srt->l.bitmap[b];
2227 bitmap = bitmap >> 1;
2232 /* evacuate the SRT. If srt_bitmap is zero, then there isn't an
2233 * srt field in the info table. That's ok, because we'll
2234 * never dereference it.
2237 scavenge_srt (StgClosure **srt, nat srt_bitmap)
2242 bitmap = srt_bitmap;
2245 if (bitmap == (StgHalfWord)(-1)) {
2246 scavenge_large_srt_bitmap( (StgLargeSRT *)srt );
2250 while (bitmap != 0) {
2251 if ((bitmap & 1) != 0) {
2252 #ifdef ENABLE_WIN32_DLL_SUPPORT
2253 // Special-case to handle references to closures hiding out in DLLs, since
2254 // double indirections required to get at those. The code generator knows
2255 // which is which when generating the SRT, so it stores the (indirect)
2256 // reference to the DLL closure in the table by first adding one to it.
2257 // We check for this here, and undo the addition before evacuating it.
2259 // If the SRT entry hasn't got bit 0 set, the SRT entry points to a
2260 // closure that's fixed at link-time, and no extra magic is required.
2261 if ( (unsigned long)(*srt) & 0x1 ) {
2262 evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
2271 bitmap = bitmap >> 1;
2277 scavenge_thunk_srt(const StgInfoTable *info)
2279 StgThunkInfoTable *thunk_info;
2281 thunk_info = itbl_to_thunk_itbl(info);
2282 scavenge_srt((StgClosure **)thunk_info->srt, thunk_info->i.srt_bitmap);
2286 scavenge_fun_srt(const StgInfoTable *info)
2288 StgFunInfoTable *fun_info;
2290 fun_info = itbl_to_fun_itbl(info);
2291 scavenge_srt((StgClosure **)fun_info->srt, fun_info->i.srt_bitmap);
2295 scavenge_ret_srt(const StgInfoTable *info)
2297 StgRetInfoTable *ret_info;
2299 ret_info = itbl_to_ret_itbl(info);
2300 scavenge_srt((StgClosure **)ret_info->srt, ret_info->i.srt_bitmap);
2303 /* -----------------------------------------------------------------------------
2305 -------------------------------------------------------------------------- */
2308 scavengeTSO (StgTSO *tso)
2310 // chase the link field for any TSOs on the same queue
2311 (StgClosure *)tso->link = evacuate((StgClosure *)tso->link);
2312 if ( tso->why_blocked == BlockedOnMVar
2313 || tso->why_blocked == BlockedOnBlackHole
2314 || tso->why_blocked == BlockedOnException
2316 || tso->why_blocked == BlockedOnGA
2317 || tso->why_blocked == BlockedOnGA_NoSend
2320 tso->block_info.closure = evacuate(tso->block_info.closure);
2322 if ( tso->blocked_exceptions != NULL ) {
2323 tso->blocked_exceptions =
2324 (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
2327 // scavenge this thread's stack
2328 scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
2331 /* -----------------------------------------------------------------------------
2332 Blocks of function args occur on the stack (at the top) and
2334 -------------------------------------------------------------------------- */
2336 STATIC_INLINE StgPtr
2337 scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
2344 switch (fun_info->fun_type) {
2346 bitmap = BITMAP_BITS(fun_info->bitmap);
2347 size = BITMAP_SIZE(fun_info->bitmap);
2350 size = ((StgLargeBitmap *)fun_info->bitmap)->size;
2351 scavenge_large_bitmap(p, (StgLargeBitmap *)fun_info->bitmap, size);
2355 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->fun_type]);
2356 size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->fun_type]);
2359 if ((bitmap & 1) == 0) {
2360 (StgClosure *)*p = evacuate((StgClosure *)*p);
2363 bitmap = bitmap >> 1;
2371 STATIC_INLINE StgPtr
2372 scavenge_PAP (StgPAP *pap)
2375 StgWord bitmap, size;
2376 StgFunInfoTable *fun_info;
2378 pap->fun = evacuate(pap->fun);
2379 fun_info = get_fun_itbl(pap->fun);
2380 ASSERT(fun_info->i.type != PAP);
2382 p = (StgPtr)pap->payload;
2385 switch (fun_info->fun_type) {
2387 bitmap = BITMAP_BITS(fun_info->bitmap);
2390 scavenge_large_bitmap(p, (StgLargeBitmap *)fun_info->bitmap, size);
2394 scavenge_large_bitmap((StgPtr)pap->payload, BCO_BITMAP(pap->fun), size);
2398 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->fun_type]);
2402 if ((bitmap & 1) == 0) {
2403 (StgClosure *)*p = evacuate((StgClosure *)*p);
2406 bitmap = bitmap >> 1;
2414 /* -----------------------------------------------------------------------------
2415 Scavenge a given step until there are no more objects in this step
2418 evac_gen is set by the caller to be either zero (for a step in a
2419 generation < N) or G where G is the generation of the step being
2422 We sometimes temporarily change evac_gen back to zero if we're
2423 scavenging a mutable object where early promotion isn't such a good
2425 -------------------------------------------------------------------------- */
2433 nat saved_evac_gen = evac_gen;
2438 failed_to_evac = rtsFalse;
2440 /* scavenge phase - standard breadth-first scavenging of the
2444 while (bd != stp->hp_bd || p < stp->hp) {
2446 // If we're at the end of this block, move on to the next block
2447 if (bd != stp->hp_bd && p == bd->free) {
2453 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2454 info = get_itbl((StgClosure *)p);
2456 ASSERT(thunk_selector_depth == 0);
2459 switch (info->type) {
2462 /* treat MVars specially, because we don't want to evacuate the
2463 * mut_link field in the middle of the closure.
2466 StgMVar *mvar = ((StgMVar *)p);
2468 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
2469 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
2470 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
2471 evac_gen = saved_evac_gen;
2472 recordMutable((StgMutClosure *)mvar);
2473 failed_to_evac = rtsFalse; // mutable.
2474 p += sizeofW(StgMVar);
2479 scavenge_fun_srt(info);
2480 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2481 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2482 p += sizeofW(StgHeader) + 2;
2486 scavenge_thunk_srt(info);
2488 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2489 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2490 p += sizeofW(StgHeader) + 2;
2494 scavenge_thunk_srt(info);
2495 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2496 p += sizeofW(StgHeader) + 2; // MIN_UPD_SIZE
2500 scavenge_fun_srt(info);
2502 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2503 p += sizeofW(StgHeader) + 1;
2507 scavenge_thunk_srt(info);
2508 p += sizeofW(StgHeader) + 2; // MIN_UPD_SIZE
2512 scavenge_fun_srt(info);
2514 p += sizeofW(StgHeader) + 1;
2518 scavenge_thunk_srt(info);
2519 p += sizeofW(StgHeader) + 2;
2523 scavenge_fun_srt(info);
2525 p += sizeofW(StgHeader) + 2;
2529 scavenge_thunk_srt(info);
2530 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2531 p += sizeofW(StgHeader) + 2;
2535 scavenge_fun_srt(info);
2537 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2538 p += sizeofW(StgHeader) + 2;
2542 scavenge_fun_srt(info);
2546 scavenge_thunk_srt(info);
2557 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2558 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2559 (StgClosure *)*p = evacuate((StgClosure *)*p);
2561 p += info->layout.payload.nptrs;
2566 StgBCO *bco = (StgBCO *)p;
2567 (StgClosure *)bco->instrs = evacuate((StgClosure *)bco->instrs);
2568 (StgClosure *)bco->literals = evacuate((StgClosure *)bco->literals);
2569 (StgClosure *)bco->ptrs = evacuate((StgClosure *)bco->ptrs);
2570 (StgClosure *)bco->itbls = evacuate((StgClosure *)bco->itbls);
2571 p += bco_sizeW(bco);
2576 if (stp->gen->no != 0) {
2579 // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an
2580 // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
2581 LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
2584 // Todo: maybe use SET_HDR() and remove LDV_recordCreate()?
2586 SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
2589 // We pretend that p has just been created.
2590 LDV_recordCreate((StgClosure *)p);
2594 case IND_OLDGEN_PERM:
2595 ((StgIndOldGen *)p)->indirectee =
2596 evacuate(((StgIndOldGen *)p)->indirectee);
2597 if (failed_to_evac) {
2598 failed_to_evac = rtsFalse;
2599 recordOldToNewPtrs((StgMutClosure *)p);
2601 p += sizeofW(StgIndOldGen);
2606 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2607 evac_gen = saved_evac_gen;
2608 recordMutable((StgMutClosure *)p);
2609 failed_to_evac = rtsFalse; // mutable anyhow
2610 p += sizeofW(StgMutVar);
2615 failed_to_evac = rtsFalse; // mutable anyhow
2616 p += sizeofW(StgMutVar);
2620 case SE_CAF_BLACKHOLE:
2623 p += BLACKHOLE_sizeW();
2628 StgBlockingQueue *bh = (StgBlockingQueue *)p;
2629 (StgClosure *)bh->blocking_queue =
2630 evacuate((StgClosure *)bh->blocking_queue);
2631 recordMutable((StgMutClosure *)bh);
2632 failed_to_evac = rtsFalse;
2633 p += BLACKHOLE_sizeW();
2637 case THUNK_SELECTOR:
2639 StgSelector *s = (StgSelector *)p;
2640 s->selectee = evacuate(s->selectee);
2641 p += THUNK_SELECTOR_sizeW();
2645 // A chunk of stack saved in a heap object
2648 StgAP_STACK *ap = (StgAP_STACK *)p;
2650 ap->fun = evacuate(ap->fun);
2651 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2652 p = (StgPtr)ap->payload + ap->size;
2658 p = scavenge_PAP((StgPAP *)p);
2662 // nothing to follow
2663 p += arr_words_sizeW((StgArrWords *)p);
2667 // follow everything
2671 evac_gen = 0; // repeatedly mutable
2672 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2673 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2674 (StgClosure *)*p = evacuate((StgClosure *)*p);
2676 evac_gen = saved_evac_gen;
2677 recordMutable((StgMutClosure *)q);
2678 failed_to_evac = rtsFalse; // mutable anyhow.
2682 case MUT_ARR_PTRS_FROZEN:
2683 // follow everything
2687 // Set the mut_link field to NULL, so that we will put this
2688 // array back on the mutable list if it is subsequently thawed
2690 ((StgMutArrPtrs*)p)->mut_link = NULL;
2692 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2693 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2694 (StgClosure *)*p = evacuate((StgClosure *)*p);
2696 // it's tempting to recordMutable() if failed_to_evac is
2697 // false, but that breaks some assumptions (eg. every
2698 // closure on the mutable list is supposed to have the MUT
2699 // flag set, and MUT_ARR_PTRS_FROZEN doesn't).
2705 StgTSO *tso = (StgTSO *)p;
2708 evac_gen = saved_evac_gen;
2709 recordMutable((StgMutClosure *)tso);
2710 failed_to_evac = rtsFalse; // mutable anyhow.
2711 p += tso_sizeW(tso);
2716 case RBH: // cf. BLACKHOLE_BQ
2719 nat size, ptrs, nonptrs, vhs;
2721 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2723 StgRBH *rbh = (StgRBH *)p;
2724 (StgClosure *)rbh->blocking_queue =
2725 evacuate((StgClosure *)rbh->blocking_queue);
2726 recordMutable((StgMutClosure *)to);
2727 failed_to_evac = rtsFalse; // mutable anyhow.
2729 belch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2730 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2731 // ToDo: use size of reverted closure here!
2732 p += BLACKHOLE_sizeW();
2738 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2739 // follow the pointer to the node which is being demanded
2740 (StgClosure *)bf->node =
2741 evacuate((StgClosure *)bf->node);
2742 // follow the link to the rest of the blocking queue
2743 (StgClosure *)bf->link =
2744 evacuate((StgClosure *)bf->link);
2745 if (failed_to_evac) {
2746 failed_to_evac = rtsFalse;
2747 recordMutable((StgMutClosure *)bf);
2750 belch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
2751 bf, info_type((StgClosure *)bf),
2752 bf->node, info_type(bf->node)));
2753 p += sizeofW(StgBlockedFetch);
2761 p += sizeofW(StgFetchMe);
2762 break; // nothing to do in this case
2764 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
2766 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
2767 (StgClosure *)fmbq->blocking_queue =
2768 evacuate((StgClosure *)fmbq->blocking_queue);
2769 if (failed_to_evac) {
2770 failed_to_evac = rtsFalse;
2771 recordMutable((StgMutClosure *)fmbq);
2774 belch("@@ scavenge: %p (%s) exciting, isn't it",
2775 p, info_type((StgClosure *)p)));
2776 p += sizeofW(StgFetchMeBlockingQueue);
2782 barf("scavenge: unimplemented/strange closure type %d @ %p",
2786 /* If we didn't manage to promote all the objects pointed to by
2787 * the current object, then we have to designate this object as
2788 * mutable (because it contains old-to-new generation pointers).
2790 if (failed_to_evac) {
2791 failed_to_evac = rtsFalse;
2792 mkMutCons((StgClosure *)q, &generations[evac_gen]);
2800 /* -----------------------------------------------------------------------------
2801 Scavenge everything on the mark stack.
2803 This is slightly different from scavenge():
2804 - we don't walk linearly through the objects, so the scavenger
2805 doesn't need to advance the pointer on to the next object.
2806 -------------------------------------------------------------------------- */
2809 scavenge_mark_stack(void)
2815 evac_gen = oldest_gen->no;
2816 saved_evac_gen = evac_gen;
2819 while (!mark_stack_empty()) {
2820 p = pop_mark_stack();
2822 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2823 info = get_itbl((StgClosure *)p);
2826 switch (info->type) {
2829 /* treat MVars specially, because we don't want to evacuate the
2830 * mut_link field in the middle of the closure.
2833 StgMVar *mvar = ((StgMVar *)p);
2835 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
2836 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
2837 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
2838 evac_gen = saved_evac_gen;
2839 failed_to_evac = rtsFalse; // mutable.
2844 scavenge_fun_srt(info);
2845 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2846 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2850 scavenge_thunk_srt(info);
2852 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2853 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2858 scavenge_fun_srt(info);
2859 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2864 scavenge_thunk_srt(info);
2867 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2872 scavenge_fun_srt(info);
2877 scavenge_thunk_srt(info);
2885 scavenge_fun_srt(info);
2889 scavenge_thunk_srt(info);
2900 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2901 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2902 (StgClosure *)*p = evacuate((StgClosure *)*p);
2908 StgBCO *bco = (StgBCO *)p;
2909 (StgClosure *)bco->instrs = evacuate((StgClosure *)bco->instrs);
2910 (StgClosure *)bco->literals = evacuate((StgClosure *)bco->literals);
2911 (StgClosure *)bco->ptrs = evacuate((StgClosure *)bco->ptrs);
2912 (StgClosure *)bco->itbls = evacuate((StgClosure *)bco->itbls);
2917 // don't need to do anything here: the only possible case
2918 // is that we're in a 1-space compacting collector, with
2919 // no "old" generation.
2923 case IND_OLDGEN_PERM:
2924 ((StgIndOldGen *)p)->indirectee =
2925 evacuate(((StgIndOldGen *)p)->indirectee);
2926 if (failed_to_evac) {
2927 recordOldToNewPtrs((StgMutClosure *)p);
2929 failed_to_evac = rtsFalse;
2934 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2935 evac_gen = saved_evac_gen;
2936 failed_to_evac = rtsFalse;
2941 failed_to_evac = rtsFalse;
2945 case SE_CAF_BLACKHOLE:
2953 StgBlockingQueue *bh = (StgBlockingQueue *)p;
2954 (StgClosure *)bh->blocking_queue =
2955 evacuate((StgClosure *)bh->blocking_queue);
2956 failed_to_evac = rtsFalse;
2960 case THUNK_SELECTOR:
2962 StgSelector *s = (StgSelector *)p;
2963 s->selectee = evacuate(s->selectee);
2967 // A chunk of stack saved in a heap object
2970 StgAP_STACK *ap = (StgAP_STACK *)p;
2972 ap->fun = evacuate(ap->fun);
2973 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2979 scavenge_PAP((StgPAP *)p);
2983 // follow everything
2987 evac_gen = 0; // repeatedly mutable
2988 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2989 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2990 (StgClosure *)*p = evacuate((StgClosure *)*p);
2992 evac_gen = saved_evac_gen;
2993 failed_to_evac = rtsFalse; // mutable anyhow.
2997 case MUT_ARR_PTRS_FROZEN:
2998 // follow everything
3002 // Set the mut_link field to NULL, so that we will put this
3003 // array on the mutable list if it is subsequently thawed
3005 ((StgMutArrPtrs*)p)->mut_link = NULL;
3007 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3008 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3009 (StgClosure *)*p = evacuate((StgClosure *)*p);
3016 StgTSO *tso = (StgTSO *)p;
3019 evac_gen = saved_evac_gen;
3020 failed_to_evac = rtsFalse;
3025 case RBH: // cf. BLACKHOLE_BQ
3028 nat size, ptrs, nonptrs, vhs;
3030 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3032 StgRBH *rbh = (StgRBH *)p;
3033 (StgClosure *)rbh->blocking_queue =
3034 evacuate((StgClosure *)rbh->blocking_queue);
3035 recordMutable((StgMutClosure *)rbh);
3036 failed_to_evac = rtsFalse; // mutable anyhow.
3038 belch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3039 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3045 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3046 // follow the pointer to the node which is being demanded
3047 (StgClosure *)bf->node =
3048 evacuate((StgClosure *)bf->node);
3049 // follow the link to the rest of the blocking queue
3050 (StgClosure *)bf->link =
3051 evacuate((StgClosure *)bf->link);
3052 if (failed_to_evac) {
3053 failed_to_evac = rtsFalse;
3054 recordMutable((StgMutClosure *)bf);
3057 belch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3058 bf, info_type((StgClosure *)bf),
3059 bf->node, info_type(bf->node)));
3067 break; // nothing to do in this case
3069 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
3071 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3072 (StgClosure *)fmbq->blocking_queue =
3073 evacuate((StgClosure *)fmbq->blocking_queue);
3074 if (failed_to_evac) {
3075 failed_to_evac = rtsFalse;
3076 recordMutable((StgMutClosure *)fmbq);
3079 belch("@@ scavenge: %p (%s) exciting, isn't it",
3080 p, info_type((StgClosure *)p)));
3086 barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p",
3090 if (failed_to_evac) {
3091 failed_to_evac = rtsFalse;
3092 mkMutCons((StgClosure *)q, &generations[evac_gen]);
3095 // mark the next bit to indicate "scavenged"
3096 mark(q+1, Bdescr(q));
3098 } // while (!mark_stack_empty())
3100 // start a new linear scan if the mark stack overflowed at some point
3101 if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
3102 IF_DEBUG(gc, belch("scavenge_mark_stack: starting linear scan"));
3103 mark_stack_overflowed = rtsFalse;
3104 oldgen_scan_bd = oldest_gen->steps[0].blocks;
3105 oldgen_scan = oldgen_scan_bd->start;
3108 if (oldgen_scan_bd) {
3109 // push a new thing on the mark stack
3111 // find a closure that is marked but not scavenged, and start
3113 while (oldgen_scan < oldgen_scan_bd->free
3114 && !is_marked(oldgen_scan,oldgen_scan_bd)) {
3118 if (oldgen_scan < oldgen_scan_bd->free) {
3120 // already scavenged?
3121 if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
3122 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3125 push_mark_stack(oldgen_scan);
3126 // ToDo: bump the linear scan by the actual size of the object
3127 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3131 oldgen_scan_bd = oldgen_scan_bd->link;
3132 if (oldgen_scan_bd != NULL) {
3133 oldgen_scan = oldgen_scan_bd->start;
3139 /* -----------------------------------------------------------------------------
3140 Scavenge one object.
3142 This is used for objects that are temporarily marked as mutable
3143 because they contain old-to-new generation pointers. Only certain
3144 objects can have this property.
3145 -------------------------------------------------------------------------- */
3148 scavenge_one(StgPtr p)
3150 const StgInfoTable *info;
3151 nat saved_evac_gen = evac_gen;
3154 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3155 info = get_itbl((StgClosure *)p);
3157 switch (info->type) {
3160 case FUN_1_0: // hardly worth specialising these guys
3180 case IND_OLDGEN_PERM:
3184 end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3185 for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
3186 (StgClosure *)*q = evacuate((StgClosure *)*q);
3192 case SE_CAF_BLACKHOLE:
3197 case THUNK_SELECTOR:
3199 StgSelector *s = (StgSelector *)p;
3200 s->selectee = evacuate(s->selectee);
3205 // nothing to follow
3210 // follow everything
3213 evac_gen = 0; // repeatedly mutable
3214 recordMutable((StgMutClosure *)p);
3215 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3216 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3217 (StgClosure *)*p = evacuate((StgClosure *)*p);
3219 evac_gen = saved_evac_gen;
3220 failed_to_evac = rtsFalse;
3224 case MUT_ARR_PTRS_FROZEN:
3226 // follow everything
3229 // Set the mut_link field to NULL, so that we will put this
3230 // array on the mutable list if it is subsequently thawed
3232 ((StgMutArrPtrs*)p)->mut_link = NULL;
3234 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3235 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3236 (StgClosure *)*p = evacuate((StgClosure *)*p);
3243 StgTSO *tso = (StgTSO *)p;
3245 evac_gen = 0; // repeatedly mutable
3247 recordMutable((StgMutClosure *)tso);
3248 evac_gen = saved_evac_gen;
3249 failed_to_evac = rtsFalse;
3255 StgAP_STACK *ap = (StgAP_STACK *)p;
3257 ap->fun = evacuate(ap->fun);
3258 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3259 p = (StgPtr)ap->payload + ap->size;
3265 p = scavenge_PAP((StgPAP *)p);
3269 // This might happen if for instance a MUT_CONS was pointing to a
3270 // THUNK which has since been updated. The IND_OLDGEN will
3271 // be on the mutable list anyway, so we don't need to do anything
3276 barf("scavenge_one: strange object %d", (int)(info->type));
3279 no_luck = failed_to_evac;
3280 failed_to_evac = rtsFalse;
3284 /* -----------------------------------------------------------------------------
3285 Scavenging mutable lists.
3287 We treat the mutable list of each generation > N (i.e. all the
3288 generations older than the one being collected) as roots. We also
3289 remove non-mutable objects from the mutable list at this point.
3290 -------------------------------------------------------------------------- */
3293 scavenge_mut_once_list(generation *gen)
3295 const StgInfoTable *info;
3296 StgMutClosure *p, *next, *new_list;
3298 p = gen->mut_once_list;
3299 new_list = END_MUT_LIST;
3303 failed_to_evac = rtsFalse;
3305 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
3307 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3310 if (info->type==RBH)
3311 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3313 switch(info->type) {
3316 case IND_OLDGEN_PERM:
3318 /* Try to pull the indirectee into this generation, so we can
3319 * remove the indirection from the mutable list.
3321 ((StgIndOldGen *)p)->indirectee =
3322 evacuate(((StgIndOldGen *)p)->indirectee);
3324 #if 0 && defined(DEBUG)
3325 if (RtsFlags.DebugFlags.gc)
3326 /* Debugging code to print out the size of the thing we just
3330 StgPtr start = gen->steps[0].scan;
3331 bdescr *start_bd = gen->steps[0].scan_bd;
3333 scavenge(&gen->steps[0]);
3334 if (start_bd != gen->steps[0].scan_bd) {
3335 size += (P_)BLOCK_ROUND_UP(start) - start;
3336 start_bd = start_bd->link;
3337 while (start_bd != gen->steps[0].scan_bd) {
3338 size += BLOCK_SIZE_W;
3339 start_bd = start_bd->link;
3341 size += gen->steps[0].scan -
3342 (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
3344 size = gen->steps[0].scan - start;
3346 belch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
3350 /* failed_to_evac might happen if we've got more than two
3351 * generations, we're collecting only generation 0, the
3352 * indirection resides in generation 2 and the indirectee is
3355 if (failed_to_evac) {
3356 failed_to_evac = rtsFalse;
3357 p->mut_link = new_list;
3360 /* the mut_link field of an IND_STATIC is overloaded as the
3361 * static link field too (it just so happens that we don't need
3362 * both at the same time), so we need to NULL it out when
3363 * removing this object from the mutable list because the static
3364 * link fields are all assumed to be NULL before doing a major
3372 /* MUT_CONS is a kind of MUT_VAR, except it that we try to remove
3373 * it from the mutable list if possible by promoting whatever it
3376 if (scavenge_one((StgPtr)((StgMutVar *)p)->var)) {
3377 /* didn't manage to promote everything, so put the
3378 * MUT_CONS back on the list.
3380 p->mut_link = new_list;
3386 // shouldn't have anything else on the mutables list
3387 barf("scavenge_mut_once_list: strange object? %d", (int)(info->type));
3391 gen->mut_once_list = new_list;
3396 scavenge_mutable_list(generation *gen)
3398 const StgInfoTable *info;
3399 StgMutClosure *p, *next;
3401 p = gen->saved_mut_list;
3405 failed_to_evac = rtsFalse;
3407 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
3409 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3412 if (info->type==RBH)
3413 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3415 switch(info->type) {
3418 // follow everything
3419 p->mut_link = gen->mut_list;
3424 end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3425 for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
3426 (StgClosure *)*q = evacuate((StgClosure *)*q);
3431 // Happens if a MUT_ARR_PTRS in the old generation is frozen
3432 case MUT_ARR_PTRS_FROZEN:
3437 end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3438 for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
3439 (StgClosure *)*q = evacuate((StgClosure *)*q);
3442 // Set the mut_link field to NULL, so that we will put this
3443 // array back on the mutable list if it is subsequently thawed
3446 if (failed_to_evac) {
3447 failed_to_evac = rtsFalse;
3448 mkMutCons((StgClosure *)p, gen);
3454 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3455 p->mut_link = gen->mut_list;
3461 StgMVar *mvar = (StgMVar *)p;
3462 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
3463 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
3464 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
3465 p->mut_link = gen->mut_list;
3472 StgTSO *tso = (StgTSO *)p;
3476 /* Don't take this TSO off the mutable list - it might still
3477 * point to some younger objects (because we set evac_gen to 0
3480 tso->mut_link = gen->mut_list;
3481 gen->mut_list = (StgMutClosure *)tso;
3487 StgBlockingQueue *bh = (StgBlockingQueue *)p;
3488 (StgClosure *)bh->blocking_queue =
3489 evacuate((StgClosure *)bh->blocking_queue);
3490 p->mut_link = gen->mut_list;
3495 /* Happens if a BLACKHOLE_BQ in the old generation is updated:
3498 case IND_OLDGEN_PERM:
3499 /* Try to pull the indirectee into this generation, so we can
3500 * remove the indirection from the mutable list.
3503 ((StgIndOldGen *)p)->indirectee =
3504 evacuate(((StgIndOldGen *)p)->indirectee);
3507 if (failed_to_evac) {
3508 failed_to_evac = rtsFalse;
3509 p->mut_link = gen->mut_once_list;
3510 gen->mut_once_list = p;
3517 // HWL: check whether all of these are necessary
3519 case RBH: // cf. BLACKHOLE_BQ
3521 // nat size, ptrs, nonptrs, vhs;
3523 // StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3524 StgRBH *rbh = (StgRBH *)p;
3525 (StgClosure *)rbh->blocking_queue =
3526 evacuate((StgClosure *)rbh->blocking_queue);
3527 if (failed_to_evac) {
3528 failed_to_evac = rtsFalse;
3529 recordMutable((StgMutClosure *)rbh);
3531 // ToDo: use size of reverted closure here!
3532 p += BLACKHOLE_sizeW();
3538 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3539 // follow the pointer to the node which is being demanded
3540 (StgClosure *)bf->node =
3541 evacuate((StgClosure *)bf->node);
3542 // follow the link to the rest of the blocking queue
3543 (StgClosure *)bf->link =
3544 evacuate((StgClosure *)bf->link);
3545 if (failed_to_evac) {
3546 failed_to_evac = rtsFalse;
3547 recordMutable((StgMutClosure *)bf);
3549 p += sizeofW(StgBlockedFetch);
3555 barf("scavenge_mutable_list: REMOTE_REF %d", (int)(info->type));
3558 p += sizeofW(StgFetchMe);
3559 break; // nothing to do in this case
3561 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
3563 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3564 (StgClosure *)fmbq->blocking_queue =
3565 evacuate((StgClosure *)fmbq->blocking_queue);
3566 if (failed_to_evac) {
3567 failed_to_evac = rtsFalse;
3568 recordMutable((StgMutClosure *)fmbq);
3570 p += sizeofW(StgFetchMeBlockingQueue);
3576 // shouldn't have anything else on the mutables list
3577 barf("scavenge_mutable_list: strange object? %d", (int)(info->type));
3584 scavenge_static(void)
3586 StgClosure* p = static_objects;
3587 const StgInfoTable *info;
3589 /* Always evacuate straight to the oldest generation for static
3591 evac_gen = oldest_gen->no;
3593 /* keep going until we've scavenged all the objects on the linked
3595 while (p != END_OF_STATIC_LIST) {
3597 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3600 if (info->type==RBH)
3601 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3603 // make sure the info pointer is into text space
3605 /* Take this object *off* the static_objects list,
3606 * and put it on the scavenged_static_objects list.
3608 static_objects = STATIC_LINK(info,p);
3609 STATIC_LINK(info,p) = scavenged_static_objects;
3610 scavenged_static_objects = p;
3612 switch (info -> type) {
3616 StgInd *ind = (StgInd *)p;
3617 ind->indirectee = evacuate(ind->indirectee);
3619 /* might fail to evacuate it, in which case we have to pop it
3620 * back on the mutable list (and take it off the
3621 * scavenged_static list because the static link and mut link
3622 * pointers are one and the same).
3624 if (failed_to_evac) {
3625 failed_to_evac = rtsFalse;
3626 scavenged_static_objects = IND_STATIC_LINK(p);
3627 ((StgMutClosure *)ind)->mut_link = oldest_gen->mut_once_list;
3628 oldest_gen->mut_once_list = (StgMutClosure *)ind;
3634 scavenge_thunk_srt(info);
3638 scavenge_fun_srt(info);
3645 next = (P_)p->payload + info->layout.payload.ptrs;
3646 // evacuate the pointers
3647 for (q = (P_)p->payload; q < next; q++) {
3648 (StgClosure *)*q = evacuate((StgClosure *)*q);
3654 barf("scavenge_static: strange closure %d", (int)(info->type));
3657 ASSERT(failed_to_evac == rtsFalse);
3659 /* get the next static object from the list. Remember, there might
3660 * be more stuff on this list now that we've done some evacuating!
3661 * (static_objects is a global)
3667 /* -----------------------------------------------------------------------------
3668 scavenge a chunk of memory described by a bitmap
3669 -------------------------------------------------------------------------- */
3672 scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
3678 bitmap = large_bitmap->bitmap[b];
3679 for (i = 0; i < size; ) {
3680 if ((bitmap & 1) == 0) {
3681 (StgClosure *)*p = evacuate((StgClosure *)*p);
3685 if (i % BITS_IN(W_) == 0) {
3687 bitmap = large_bitmap->bitmap[b];
3689 bitmap = bitmap >> 1;
3694 STATIC_INLINE StgPtr
3695 scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap)
3698 if ((bitmap & 1) == 0) {
3699 (StgClosure *)*p = evacuate((StgClosure *)*p);
3702 bitmap = bitmap >> 1;
3708 /* -----------------------------------------------------------------------------
3709 scavenge_stack walks over a section of stack and evacuates all the
3710 objects pointed to by it. We can use the same code for walking
3711 AP_STACK_UPDs, since these are just sections of copied stack.
3712 -------------------------------------------------------------------------- */
3716 scavenge_stack(StgPtr p, StgPtr stack_end)
3718 const StgRetInfoTable* info;
3722 //IF_DEBUG(sanity, belch(" scavenging stack between %p and %p", p, stack_end));
3725 * Each time around this loop, we are looking at a chunk of stack
3726 * that starts with an activation record.
3729 while (p < stack_end) {
3730 info = get_ret_itbl((StgClosure *)p);
3732 switch (info->i.type) {
3735 ((StgUpdateFrame *)p)->updatee
3736 = evacuate(((StgUpdateFrame *)p)->updatee);
3737 p += sizeofW(StgUpdateFrame);
3740 // small bitmap (< 32 entries, or 64 on a 64-bit machine)
3745 bitmap = BITMAP_BITS(info->i.layout.bitmap);
3746 size = BITMAP_SIZE(info->i.layout.bitmap);
3747 // NOTE: the payload starts immediately after the info-ptr, we
3748 // don't have an StgHeader in the same sense as a heap closure.
3750 p = scavenge_small_bitmap(p, size, bitmap);
3753 scavenge_srt((StgClosure **)info->srt, info->i.srt_bitmap);
3761 (StgClosure *)*p = evacuate((StgClosure *)*p);
3764 size = BCO_BITMAP_SIZE(bco);
3765 scavenge_large_bitmap(p, BCO_BITMAP(bco), size);
3770 // large bitmap (> 32 entries, or > 64 on a 64-bit machine)
3776 size = info->i.layout.large_bitmap->size;
3778 scavenge_large_bitmap(p, info->i.layout.large_bitmap, size);
3780 // and don't forget to follow the SRT
3784 // Dynamic bitmap: the mask is stored on the stack, and
3785 // there are a number of non-pointers followed by a number
3786 // of pointers above the bitmapped area. (see StgMacros.h,
3791 dyn = ((StgRetDyn *)p)->liveness;
3793 // traverse the bitmap first
3794 bitmap = GET_LIVENESS(dyn);
3795 p = (P_)&((StgRetDyn *)p)->payload[0];
3796 size = RET_DYN_BITMAP_SIZE;
3797 p = scavenge_small_bitmap(p, size, bitmap);
3799 // skip over the non-ptr words
3800 p += GET_NONPTRS(dyn) + RET_DYN_NONPTR_REGS_SIZE;
3802 // follow the ptr words
3803 for (size = GET_PTRS(dyn); size > 0; size--) {
3804 (StgClosure *)*p = evacuate((StgClosure *)*p);
3812 StgRetFun *ret_fun = (StgRetFun *)p;
3813 StgFunInfoTable *fun_info;
3815 ret_fun->fun = evacuate(ret_fun->fun);
3816 fun_info = get_fun_itbl(ret_fun->fun);
3817 p = scavenge_arg_block(fun_info, ret_fun->payload);
3822 barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->i.type));
3827 /*-----------------------------------------------------------------------------
3828 scavenge the large object list.
3830 evac_gen set by caller; similar games played with evac_gen as with
3831 scavenge() - see comment at the top of scavenge(). Most large
3832 objects are (repeatedly) mutable, so most of the time evac_gen will
3834 --------------------------------------------------------------------------- */
3837 scavenge_large(step *stp)
3842 bd = stp->new_large_objects;
3844 for (; bd != NULL; bd = stp->new_large_objects) {
3846 /* take this object *off* the large objects list and put it on
3847 * the scavenged large objects list. This is so that we can
3848 * treat new_large_objects as a stack and push new objects on
3849 * the front when evacuating.
3851 stp->new_large_objects = bd->link;
3852 dbl_link_onto(bd, &stp->scavenged_large_objects);
3854 // update the block count in this step.
3855 stp->n_scavenged_large_blocks += bd->blocks;
3858 if (scavenge_one(p)) {
3859 mkMutCons((StgClosure *)p, stp->gen);
3864 /* -----------------------------------------------------------------------------
3865 Initialising the static object & mutable lists
3866 -------------------------------------------------------------------------- */
3869 zero_static_object_list(StgClosure* first_static)
3873 const StgInfoTable *info;
3875 for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
3877 link = STATIC_LINK(info, p);
3878 STATIC_LINK(info,p) = NULL;
3882 /* This function is only needed because we share the mutable link
3883 * field with the static link field in an IND_STATIC, so we have to
3884 * zero the mut_link field before doing a major GC, which needs the
3885 * static link field.
3887 * It doesn't do any harm to zero all the mutable link fields on the
3892 zero_mutable_list( StgMutClosure *first )
3894 StgMutClosure *next, *c;
3896 for (c = first; c != END_MUT_LIST; c = next) {
3902 /* -----------------------------------------------------------------------------
3904 -------------------------------------------------------------------------- */
3911 for (c = (StgIndStatic *)caf_list; c != NULL;
3912 c = (StgIndStatic *)c->static_link)
3914 c->header.info = c->saved_info;
3915 c->saved_info = NULL;
3916 // could, but not necessary: c->static_link = NULL;
3922 markCAFs( evac_fn evac )
3926 for (c = (StgIndStatic *)caf_list; c != NULL;
3927 c = (StgIndStatic *)c->static_link)
3929 evac(&c->indirectee);
3933 /* -----------------------------------------------------------------------------
3934 Sanity code for CAF garbage collection.
3936 With DEBUG turned on, we manage a CAF list in addition to the SRT
3937 mechanism. After GC, we run down the CAF list and blackhole any
3938 CAFs which have been garbage collected. This means we get an error
3939 whenever the program tries to enter a garbage collected CAF.
3941 Any garbage collected CAFs are taken off the CAF list at the same
3943 -------------------------------------------------------------------------- */
3945 #if 0 && defined(DEBUG)
3952 const StgInfoTable *info;
3963 ASSERT(info->type == IND_STATIC);
3965 if (STATIC_LINK(info,p) == NULL) {
3966 IF_DEBUG(gccafs, belch("CAF gc'd at 0x%04lx", (long)p));
3968 SET_INFO(p,&stg_BLACKHOLE_info);
3969 p = STATIC_LINK2(info,p);
3973 pp = &STATIC_LINK2(info,p);
3980 // belch("%d CAFs live", i);
3985 /* -----------------------------------------------------------------------------
3988 Whenever a thread returns to the scheduler after possibly doing
3989 some work, we have to run down the stack and black-hole all the
3990 closures referred to by update frames.
3991 -------------------------------------------------------------------------- */
3994 threadLazyBlackHole(StgTSO *tso)
3997 StgRetInfoTable *info;
3998 StgBlockingQueue *bh;
4001 stack_end = &tso->stack[tso->stack_size];
4003 frame = (StgClosure *)tso->sp;
4006 info = get_ret_itbl(frame);
4008 switch (info->i.type) {
4011 bh = (StgBlockingQueue *)((StgUpdateFrame *)frame)->updatee;
4013 /* if the thunk is already blackholed, it means we've also
4014 * already blackholed the rest of the thunks on this stack,
4015 * so we can stop early.
4017 * The blackhole made for a CAF is a CAF_BLACKHOLE, so they
4018 * don't interfere with this optimisation.
4020 if (bh->header.info == &stg_BLACKHOLE_info) {
4024 if (bh->header.info != &stg_BLACKHOLE_BQ_info &&
4025 bh->header.info != &stg_CAF_BLACKHOLE_info) {
4026 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4027 belch("Unexpected lazy BHing required at 0x%04x",(int)bh);
4031 // We pretend that bh is now dead.
4032 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4034 SET_INFO(bh,&stg_BLACKHOLE_info);
4037 // We pretend that bh has just been created.
4038 LDV_recordCreate(bh);
4042 frame = (StgClosure *) ((StgUpdateFrame *)frame + 1);
4048 // normal stack frames; do nothing except advance the pointer
4050 (StgPtr)frame += stack_frame_sizeW(frame);
4056 /* -----------------------------------------------------------------------------
4059 * Code largely pinched from old RTS, then hacked to bits. We also do
4060 * lazy black holing here.
4062 * -------------------------------------------------------------------------- */
4064 struct stack_gap { StgWord gap_size; struct stack_gap *next_gap; };
4067 threadSqueezeStack(StgTSO *tso)
4070 rtsBool prev_was_update_frame;
4071 StgClosure *updatee = NULL;
4073 StgRetInfoTable *info;
4074 StgWord current_gap_size;
4075 struct stack_gap *gap;
4078 // Traverse the stack upwards, replacing adjacent update frames
4079 // with a single update frame and a "stack gap". A stack gap
4080 // contains two values: the size of the gap, and the distance
4081 // to the next gap (or the stack top).
4083 bottom = &(tso->stack[tso->stack_size]);
4087 ASSERT(frame < bottom);
4089 prev_was_update_frame = rtsFalse;
4090 current_gap_size = 0;
4091 gap = (struct stack_gap *) (tso->sp - sizeofW(StgUpdateFrame));
4093 while (frame < bottom) {
4095 info = get_ret_itbl((StgClosure *)frame);
4096 switch (info->i.type) {
4100 StgUpdateFrame *upd = (StgUpdateFrame *)frame;
4102 if (upd->updatee->header.info == &stg_BLACKHOLE_info) {
4104 // found a BLACKHOLE'd update frame; we've been here
4105 // before, in a previous GC, so just break out.
4107 // Mark the end of the gap, if we're in one.
4108 if (current_gap_size != 0) {
4109 gap = (struct stack_gap *)(frame-sizeofW(StgUpdateFrame));
4112 frame += sizeofW(StgUpdateFrame);
4113 goto done_traversing;
4116 if (prev_was_update_frame) {
4118 TICK_UPD_SQUEEZED();
4119 /* wasn't there something about update squeezing and ticky to be
4120 * sorted out? oh yes: we aren't counting each enter properly
4121 * in this case. See the log somewhere. KSW 1999-04-21
4123 * Check two things: that the two update frames don't point to
4124 * the same object, and that the updatee_bypass isn't already an
4125 * indirection. Both of these cases only happen when we're in a
4126 * block hole-style loop (and there are multiple update frames
4127 * on the stack pointing to the same closure), but they can both
4128 * screw us up if we don't check.
4130 if (upd->updatee != updatee && !closure_IND(upd->updatee)) {
4131 // this wakes the threads up
4132 UPD_IND_NOLOCK(upd->updatee, updatee);
4135 // now mark this update frame as a stack gap. The gap
4136 // marker resides in the bottom-most update frame of
4137 // the series of adjacent frames, and covers all the
4138 // frames in this series.
4139 current_gap_size += sizeofW(StgUpdateFrame);
4140 ((struct stack_gap *)frame)->gap_size = current_gap_size;
4141 ((struct stack_gap *)frame)->next_gap = gap;
4143 frame += sizeofW(StgUpdateFrame);
4147 // single update frame, or the topmost update frame in a series
4149 StgBlockingQueue *bh = (StgBlockingQueue *)upd->updatee;
4151 // Do lazy black-holing
4152 if (bh->header.info != &stg_BLACKHOLE_info &&
4153 bh->header.info != &stg_BLACKHOLE_BQ_info &&
4154 bh->header.info != &stg_CAF_BLACKHOLE_info) {
4155 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4156 belch("Unexpected lazy BHing required at 0x%04x",(int)bh);
4159 /* zero out the slop so that the sanity checker can tell
4160 * where the next closure is.
4163 StgInfoTable *bh_info = get_itbl(bh);
4164 nat np = bh_info->layout.payload.ptrs,
4165 nw = bh_info->layout.payload.nptrs, i;
4166 /* don't zero out slop for a THUNK_SELECTOR,
4167 * because its layout info is used for a
4168 * different purpose, and it's exactly the
4169 * same size as a BLACKHOLE in any case.
4171 if (bh_info->type != THUNK_SELECTOR) {
4172 for (i = np; i < np + nw; i++) {
4173 ((StgClosure *)bh)->payload[i] = 0;
4179 // We pretend that bh is now dead.
4180 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4182 // Todo: maybe use SET_HDR() and remove LDV_recordCreate()?
4183 SET_INFO(bh,&stg_BLACKHOLE_info);
4185 // We pretend that bh has just been created.
4186 LDV_recordCreate(bh);
4190 prev_was_update_frame = rtsTrue;
4191 updatee = upd->updatee;
4192 frame += sizeofW(StgUpdateFrame);
4198 prev_was_update_frame = rtsFalse;
4200 // we're not in a gap... check whether this is the end of a gap
4201 // (an update frame can't be the end of a gap).
4202 if (current_gap_size != 0) {
4203 gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
4205 current_gap_size = 0;
4207 frame += stack_frame_sizeW((StgClosure *)frame);
4214 // Now we have a stack with gaps in it, and we have to walk down
4215 // shoving the stack up to fill in the gaps. A diagram might
4219 // | ********* | <- sp
4223 // | stack_gap | <- gap | chunk_size
4225 // | ......... | <- gap_end v
4231 // 'sp' points the the current top-of-stack
4232 // 'gap' points to the stack_gap structure inside the gap
4233 // ***** indicates real stack data
4234 // ..... indicates gap
4235 // <empty> indicates unused
4239 void *gap_start, *next_gap_start, *gap_end;
4242 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4243 sp = next_gap_start;
4245 while ((StgPtr)gap > tso->sp) {
4247 // we're working in *bytes* now...
4248 gap_start = next_gap_start;
4249 gap_end = (void*) ((unsigned char*)gap_start - gap->gap_size * sizeof(W_));
4251 gap = gap->next_gap;
4252 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4254 chunk_size = (unsigned char*)gap_end - (unsigned char*)next_gap_start;
4255 (unsigned char*)sp -= chunk_size;
4256 memmove(sp, next_gap_start, chunk_size);
4259 tso->sp = (StgPtr)sp;
4263 /* -----------------------------------------------------------------------------
4266 * We have to prepare for GC - this means doing lazy black holing
4267 * here. We also take the opportunity to do stack squeezing if it's
4269 * -------------------------------------------------------------------------- */
4271 threadPaused(StgTSO *tso)
4273 if ( RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue )
4274 threadSqueezeStack(tso); // does black holing too
4276 threadLazyBlackHole(tso);
4279 /* -----------------------------------------------------------------------------
4281 * -------------------------------------------------------------------------- */
4285 printMutOnceList(generation *gen)
4287 StgMutClosure *p, *next;
4289 p = gen->mut_once_list;
4292 fprintf(stderr, "@@ Mut once list %p: ", gen->mut_once_list);
4293 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
4294 fprintf(stderr, "%p (%s), ",
4295 p, info_type((StgClosure *)p));
4297 fputc('\n', stderr);
4301 printMutableList(generation *gen)
4303 StgMutClosure *p, *next;
4308 fprintf(stderr, "@@ Mutable list %p: ", gen->mut_list);
4309 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
4310 fprintf(stderr, "%p (%s), ",
4311 p, info_type((StgClosure *)p));
4313 fputc('\n', stderr);
4316 STATIC_INLINE rtsBool
4317 maybeLarge(StgClosure *closure)
4319 StgInfoTable *info = get_itbl(closure);
4321 /* closure types that may be found on the new_large_objects list;
4322 see scavenge_large */
4323 return (info->type == MUT_ARR_PTRS ||
4324 info->type == MUT_ARR_PTRS_FROZEN ||
4325 info->type == TSO ||
4326 info->type == ARR_WORDS);