1 /* -----------------------------------------------------------------------------
2 * $Id: GC.c,v 1.155 2003/05/14 09:13:59 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;
383 /* Keep a count of how many new blocks we allocated during this GC
384 * (used for resizing the allocation area, later).
388 // Initialise to-space in all the generations/steps that we're
391 for (g = 0; g <= N; g++) {
392 generations[g].mut_once_list = END_MUT_LIST;
393 generations[g].mut_list = END_MUT_LIST;
395 for (s = 0; s < generations[g].n_steps; s++) {
397 // generation 0, step 0 doesn't need to-space
398 if (g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1) {
402 stp = &generations[g].steps[s];
403 ASSERT(stp->gen_no == g);
405 // start a new to-space for this step.
408 stp->to_blocks = NULL;
410 // allocate the first to-space block; extra blocks will be
411 // chained on as necessary.
412 bd = gc_alloc_block(stp);
414 stp->scan = bd->start;
417 // initialise the large object queues.
418 stp->new_large_objects = NULL;
419 stp->scavenged_large_objects = NULL;
420 stp->n_scavenged_large_blocks = 0;
422 // mark the large objects as not evacuated yet
423 for (bd = stp->large_objects; bd; bd = bd->link) {
424 bd->flags = BF_LARGE;
427 // for a compacted step, we need to allocate the bitmap
428 if (stp->is_compacted) {
429 nat bitmap_size; // in bytes
430 bdescr *bitmap_bdescr;
433 bitmap_size = stp->n_blocks * BLOCK_SIZE / (sizeof(W_)*BITS_PER_BYTE);
435 if (bitmap_size > 0) {
436 bitmap_bdescr = allocGroup((nat)BLOCK_ROUND_UP(bitmap_size)
438 stp->bitmap = bitmap_bdescr;
439 bitmap = bitmap_bdescr->start;
441 IF_DEBUG(gc, belch("bitmap_size: %d, bitmap: %p",
442 bitmap_size, bitmap););
444 // don't forget to fill it with zeros!
445 memset(bitmap, 0, bitmap_size);
447 // for each block in this step, point to its bitmap from the
449 for (bd=stp->blocks; bd != NULL; bd = bd->link) {
450 bd->u.bitmap = bitmap;
451 bitmap += BLOCK_SIZE_W / (sizeof(W_)*BITS_PER_BYTE);
458 /* make sure the older generations have at least one block to
459 * allocate into (this makes things easier for copy(), see below).
461 for (g = N+1; g < RtsFlags.GcFlags.generations; g++) {
462 for (s = 0; s < generations[g].n_steps; s++) {
463 stp = &generations[g].steps[s];
464 if (stp->hp_bd == NULL) {
465 ASSERT(stp->blocks == NULL);
466 bd = gc_alloc_block(stp);
470 /* Set the scan pointer for older generations: remember we
471 * still have to scavenge objects that have been promoted. */
473 stp->scan_bd = stp->hp_bd;
474 stp->to_blocks = NULL;
475 stp->n_to_blocks = 0;
476 stp->new_large_objects = NULL;
477 stp->scavenged_large_objects = NULL;
478 stp->n_scavenged_large_blocks = 0;
482 /* Allocate a mark stack if we're doing a major collection.
485 mark_stack_bdescr = allocGroup(MARK_STACK_BLOCKS);
486 mark_stack = (StgPtr *)mark_stack_bdescr->start;
487 mark_sp = mark_stack;
488 mark_splim = mark_stack + (MARK_STACK_BLOCKS * BLOCK_SIZE_W);
490 mark_stack_bdescr = NULL;
493 /* -----------------------------------------------------------------------
494 * follow all the roots that we know about:
495 * - mutable lists from each generation > N
496 * we want to *scavenge* these roots, not evacuate them: they're not
497 * going to move in this GC.
498 * Also: do them in reverse generation order. This is because we
499 * often want to promote objects that are pointed to by older
500 * generations early, so we don't have to repeatedly copy them.
501 * Doing the generations in reverse order ensures that we don't end
502 * up in the situation where we want to evac an object to gen 3 and
503 * it has already been evaced to gen 2.
507 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
508 generations[g].saved_mut_list = generations[g].mut_list;
509 generations[g].mut_list = END_MUT_LIST;
512 // Do the mut-once lists first
513 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
514 IF_PAR_DEBUG(verbose,
515 printMutOnceList(&generations[g]));
516 scavenge_mut_once_list(&generations[g]);
518 for (st = generations[g].n_steps-1; st >= 0; st--) {
519 scavenge(&generations[g].steps[st]);
523 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
524 IF_PAR_DEBUG(verbose,
525 printMutableList(&generations[g]));
526 scavenge_mutable_list(&generations[g]);
528 for (st = generations[g].n_steps-1; st >= 0; st--) {
529 scavenge(&generations[g].steps[st]);
534 /* follow roots from the CAF list (used by GHCi)
539 /* follow all the roots that the application knows about.
542 get_roots(mark_root);
545 /* And don't forget to mark the TSO if we got here direct from
547 /* Not needed in a seq version?
549 CurrentTSO = (StgTSO *)MarkRoot((StgClosure *)CurrentTSO);
553 // Mark the entries in the GALA table of the parallel system
554 markLocalGAs(major_gc);
555 // Mark all entries on the list of pending fetches
556 markPendingFetches(major_gc);
559 /* Mark the weak pointer list, and prepare to detect dead weak
562 mark_weak_ptr_list(&weak_ptr_list);
563 old_weak_ptr_list = weak_ptr_list;
564 weak_ptr_list = NULL;
565 weak_stage = WeakPtrs;
567 /* The all_threads list is like the weak_ptr_list.
568 * See traverse_weak_ptr_list() for the details.
570 old_all_threads = all_threads;
571 all_threads = END_TSO_QUEUE;
572 resurrected_threads = END_TSO_QUEUE;
574 /* Mark the stable pointer table.
576 markStablePtrTable(mark_root);
580 /* ToDo: To fix the caf leak, we need to make the commented out
581 * parts of this code do something sensible - as described in
584 extern void markHugsObjects(void);
589 /* -------------------------------------------------------------------------
590 * Repeatedly scavenge all the areas we know about until there's no
591 * more scavenging to be done.
598 // scavenge static objects
599 if (major_gc && static_objects != END_OF_STATIC_LIST) {
600 IF_DEBUG(sanity, checkStaticObjects(static_objects));
604 /* When scavenging the older generations: Objects may have been
605 * evacuated from generations <= N into older generations, and we
606 * need to scavenge these objects. We're going to try to ensure that
607 * any evacuations that occur move the objects into at least the
608 * same generation as the object being scavenged, otherwise we
609 * have to create new entries on the mutable list for the older
613 // scavenge each step in generations 0..maxgen
619 // scavenge objects in compacted generation
620 if (mark_stack_overflowed || oldgen_scan_bd != NULL ||
621 (mark_stack_bdescr != NULL && !mark_stack_empty())) {
622 scavenge_mark_stack();
626 for (gen = RtsFlags.GcFlags.generations; --gen >= 0; ) {
627 for (st = generations[gen].n_steps; --st >= 0; ) {
628 if (gen == 0 && st == 0 && RtsFlags.GcFlags.generations > 1) {
631 stp = &generations[gen].steps[st];
633 if (stp->hp_bd != stp->scan_bd || stp->scan < stp->hp) {
638 if (stp->new_large_objects != NULL) {
647 if (flag) { goto loop; }
649 // must be last... invariant is that everything is fully
650 // scavenged at this point.
651 if (traverse_weak_ptr_list()) { // returns rtsTrue if evaced something
656 /* Update the pointers from the "main thread" list - these are
657 * treated as weak pointers because we want to allow a main thread
658 * to get a BlockedOnDeadMVar exception in the same way as any other
659 * thread. Note that the threads should all have been retained by
660 * GC by virtue of being on the all_threads list, we're just
661 * updating pointers here.
666 for (m = main_threads; m != NULL; m = m->link) {
667 tso = (StgTSO *) isAlive((StgClosure *)m->tso);
669 barf("main thread has been GC'd");
676 // Reconstruct the Global Address tables used in GUM
677 rebuildGAtables(major_gc);
678 IF_DEBUG(sanity, checkLAGAtable(rtsTrue/*check closures, too*/));
681 // Now see which stable names are still alive.
684 // Tidy the end of the to-space chains
685 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
686 for (s = 0; s < generations[g].n_steps; s++) {
687 stp = &generations[g].steps[s];
688 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
689 ASSERT(Bdescr(stp->hp) == stp->hp_bd);
690 stp->hp_bd->free = stp->hp;
696 // We call processHeapClosureForDead() on every closure destroyed during
697 // the current garbage collection, so we invoke LdvCensusForDead().
698 if (RtsFlags.ProfFlags.doHeapProfile == HEAP_BY_LDV
699 || RtsFlags.ProfFlags.bioSelector != NULL)
703 // NO MORE EVACUATION AFTER THIS POINT!
704 // Finally: compaction of the oldest generation.
705 if (major_gc && oldest_gen->steps[0].is_compacted) {
706 // save number of blocks for stats
707 oldgen_saved_blocks = oldest_gen->steps[0].n_blocks;
711 IF_DEBUG(sanity, checkGlobalTSOList(rtsFalse));
713 /* run through all the generations/steps and tidy up
715 copied = new_blocks * BLOCK_SIZE_W;
716 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
719 generations[g].collections++; // for stats
722 for (s = 0; s < generations[g].n_steps; s++) {
724 stp = &generations[g].steps[s];
726 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
727 // stats information: how much we copied
729 copied -= stp->hp_bd->start + BLOCK_SIZE_W -
734 // for generations we collected...
737 // rough calculation of garbage collected, for stats output
738 if (stp->is_compacted) {
739 collected += (oldgen_saved_blocks - stp->n_blocks) * BLOCK_SIZE_W;
741 collected += stp->n_blocks * BLOCK_SIZE_W;
744 /* free old memory and shift to-space into from-space for all
745 * the collected steps (except the allocation area). These
746 * freed blocks will probaby be quickly recycled.
748 if (!(g == 0 && s == 0)) {
749 if (stp->is_compacted) {
750 // for a compacted step, just shift the new to-space
751 // onto the front of the now-compacted existing blocks.
752 for (bd = stp->to_blocks; bd != NULL; bd = bd->link) {
753 bd->flags &= ~BF_EVACUATED; // now from-space
755 // tack the new blocks on the end of the existing blocks
756 if (stp->blocks == NULL) {
757 stp->blocks = stp->to_blocks;
759 for (bd = stp->blocks; bd != NULL; bd = next) {
762 bd->link = stp->to_blocks;
766 // add the new blocks to the block tally
767 stp->n_blocks += stp->n_to_blocks;
769 freeChain(stp->blocks);
770 stp->blocks = stp->to_blocks;
771 stp->n_blocks = stp->n_to_blocks;
772 for (bd = stp->blocks; bd != NULL; bd = bd->link) {
773 bd->flags &= ~BF_EVACUATED; // now from-space
776 stp->to_blocks = NULL;
777 stp->n_to_blocks = 0;
780 /* LARGE OBJECTS. The current live large objects are chained on
781 * scavenged_large, having been moved during garbage
782 * collection from large_objects. Any objects left on
783 * large_objects list are therefore dead, so we free them here.
785 for (bd = stp->large_objects; bd != NULL; bd = next) {
791 // update the count of blocks used by large objects
792 for (bd = stp->scavenged_large_objects; bd != NULL; bd = bd->link) {
793 bd->flags &= ~BF_EVACUATED;
795 stp->large_objects = stp->scavenged_large_objects;
796 stp->n_large_blocks = stp->n_scavenged_large_blocks;
799 // for older generations...
801 /* For older generations, we need to append the
802 * scavenged_large_object list (i.e. large objects that have been
803 * promoted during this GC) to the large_object list for that step.
805 for (bd = stp->scavenged_large_objects; bd; bd = next) {
807 bd->flags &= ~BF_EVACUATED;
808 dbl_link_onto(bd, &stp->large_objects);
811 // add the new blocks we promoted during this GC
812 stp->n_blocks += stp->n_to_blocks;
813 stp->n_to_blocks = 0;
814 stp->n_large_blocks += stp->n_scavenged_large_blocks;
819 /* Reset the sizes of the older generations when we do a major
822 * CURRENT STRATEGY: make all generations except zero the same size.
823 * We have to stay within the maximum heap size, and leave a certain
824 * percentage of the maximum heap size available to allocate into.
826 if (major_gc && RtsFlags.GcFlags.generations > 1) {
827 nat live, size, min_alloc;
828 nat max = RtsFlags.GcFlags.maxHeapSize;
829 nat gens = RtsFlags.GcFlags.generations;
831 // live in the oldest generations
832 live = oldest_gen->steps[0].n_blocks +
833 oldest_gen->steps[0].n_large_blocks;
835 // default max size for all generations except zero
836 size = stg_max(live * RtsFlags.GcFlags.oldGenFactor,
837 RtsFlags.GcFlags.minOldGenSize);
839 // minimum size for generation zero
840 min_alloc = stg_max((RtsFlags.GcFlags.pcFreeHeap * max) / 200,
841 RtsFlags.GcFlags.minAllocAreaSize);
843 // Auto-enable compaction when the residency reaches a
844 // certain percentage of the maximum heap size (default: 30%).
845 if (RtsFlags.GcFlags.generations > 1 &&
846 (RtsFlags.GcFlags.compact ||
848 oldest_gen->steps[0].n_blocks >
849 (RtsFlags.GcFlags.compactThreshold * max) / 100))) {
850 oldest_gen->steps[0].is_compacted = 1;
851 // fprintf(stderr,"compaction: on\n", live);
853 oldest_gen->steps[0].is_compacted = 0;
854 // fprintf(stderr,"compaction: off\n", live);
857 // if we're going to go over the maximum heap size, reduce the
858 // size of the generations accordingly. The calculation is
859 // different if compaction is turned on, because we don't need
860 // to double the space required to collect the old generation.
863 // this test is necessary to ensure that the calculations
864 // below don't have any negative results - we're working
865 // with unsigned values here.
866 if (max < min_alloc) {
870 if (oldest_gen->steps[0].is_compacted) {
871 if ( (size + (size - 1) * (gens - 2) * 2) + min_alloc > max ) {
872 size = (max - min_alloc) / ((gens - 1) * 2 - 1);
875 if ( (size * (gens - 1) * 2) + min_alloc > max ) {
876 size = (max - min_alloc) / ((gens - 1) * 2);
886 fprintf(stderr,"live: %d, min_alloc: %d, size : %d, max = %d\n", live,
887 min_alloc, size, max);
890 for (g = 0; g < gens; g++) {
891 generations[g].max_blocks = size;
895 // Guess the amount of live data for stats.
898 /* Free the small objects allocated via allocate(), since this will
899 * all have been copied into G0S1 now.
901 if (small_alloc_list != NULL) {
902 freeChain(small_alloc_list);
904 small_alloc_list = NULL;
908 alloc_blocks_lim = RtsFlags.GcFlags.minAllocAreaSize;
910 // Start a new pinned_object_block
911 pinned_object_block = NULL;
913 /* Free the mark stack.
915 if (mark_stack_bdescr != NULL) {
916 freeGroup(mark_stack_bdescr);
921 for (g = 0; g <= N; g++) {
922 for (s = 0; s < generations[g].n_steps; s++) {
923 stp = &generations[g].steps[s];
924 if (stp->is_compacted && stp->bitmap != NULL) {
925 freeGroup(stp->bitmap);
930 /* Two-space collector:
931 * Free the old to-space, and estimate the amount of live data.
933 if (RtsFlags.GcFlags.generations == 1) {
936 if (old_to_blocks != NULL) {
937 freeChain(old_to_blocks);
939 for (bd = g0s0->to_blocks; bd != NULL; bd = bd->link) {
940 bd->flags = 0; // now from-space
943 /* For a two-space collector, we need to resize the nursery. */
945 /* set up a new nursery. Allocate a nursery size based on a
946 * function of the amount of live data (by default a factor of 2)
947 * Use the blocks from the old nursery if possible, freeing up any
950 * If we get near the maximum heap size, then adjust our nursery
951 * size accordingly. If the nursery is the same size as the live
952 * data (L), then we need 3L bytes. We can reduce the size of the
953 * nursery to bring the required memory down near 2L bytes.
955 * A normal 2-space collector would need 4L bytes to give the same
956 * performance we get from 3L bytes, reducing to the same
957 * performance at 2L bytes.
959 blocks = g0s0->n_to_blocks;
961 if ( RtsFlags.GcFlags.maxHeapSize != 0 &&
962 blocks * RtsFlags.GcFlags.oldGenFactor * 2 >
963 RtsFlags.GcFlags.maxHeapSize ) {
964 long adjusted_blocks; // signed on purpose
967 adjusted_blocks = (RtsFlags.GcFlags.maxHeapSize - 2 * blocks);
968 IF_DEBUG(gc, belch("@@ Near maximum heap size of 0x%x blocks, blocks = %d, adjusted to %ld", RtsFlags.GcFlags.maxHeapSize, blocks, adjusted_blocks));
969 pc_free = adjusted_blocks * 100 / RtsFlags.GcFlags.maxHeapSize;
970 if (pc_free < RtsFlags.GcFlags.pcFreeHeap) /* might even be < 0 */ {
973 blocks = adjusted_blocks;
976 blocks *= RtsFlags.GcFlags.oldGenFactor;
977 if (blocks < RtsFlags.GcFlags.minAllocAreaSize) {
978 blocks = RtsFlags.GcFlags.minAllocAreaSize;
981 resizeNursery(blocks);
984 /* Generational collector:
985 * If the user has given us a suggested heap size, adjust our
986 * allocation area to make best use of the memory available.
989 if (RtsFlags.GcFlags.heapSizeSuggestion) {
991 nat needed = calcNeeded(); // approx blocks needed at next GC
993 /* Guess how much will be live in generation 0 step 0 next time.
994 * A good approximation is obtained by finding the
995 * percentage of g0s0 that was live at the last minor GC.
998 g0s0_pcnt_kept = (new_blocks * 100) / g0s0->n_blocks;
1001 /* Estimate a size for the allocation area based on the
1002 * information available. We might end up going slightly under
1003 * or over the suggested heap size, but we should be pretty
1006 * Formula: suggested - needed
1007 * ----------------------------
1008 * 1 + g0s0_pcnt_kept/100
1010 * where 'needed' is the amount of memory needed at the next
1011 * collection for collecting all steps except g0s0.
1014 (((long)RtsFlags.GcFlags.heapSizeSuggestion - (long)needed) * 100) /
1015 (100 + (long)g0s0_pcnt_kept);
1017 if (blocks < (long)RtsFlags.GcFlags.minAllocAreaSize) {
1018 blocks = RtsFlags.GcFlags.minAllocAreaSize;
1021 resizeNursery((nat)blocks);
1024 // we might have added extra large blocks to the nursery, so
1025 // resize back to minAllocAreaSize again.
1026 resizeNursery(RtsFlags.GcFlags.minAllocAreaSize);
1030 // mark the garbage collected CAFs as dead
1031 #if 0 && defined(DEBUG) // doesn't work at the moment
1032 if (major_gc) { gcCAFs(); }
1036 // resetStaticObjectForRetainerProfiling() must be called before
1038 resetStaticObjectForRetainerProfiling();
1041 // zero the scavenged static object list
1043 zero_static_object_list(scavenged_static_objects);
1046 // Reset the nursery
1049 RELEASE_LOCK(&sched_mutex);
1051 // start any pending finalizers
1052 scheduleFinalizers(old_weak_ptr_list);
1054 // send exceptions to any threads which were about to die
1055 resurrectThreads(resurrected_threads);
1057 ACQUIRE_LOCK(&sched_mutex);
1059 // Update the stable pointer hash table.
1060 updateStablePtrTable(major_gc);
1062 // check sanity after GC
1063 IF_DEBUG(sanity, checkSanity());
1065 // extra GC trace info
1066 IF_DEBUG(gc, statDescribeGens());
1069 // symbol-table based profiling
1070 /* heapCensus(to_blocks); */ /* ToDo */
1073 // restore enclosing cost centre
1078 // check for memory leaks if sanity checking is on
1079 IF_DEBUG(sanity, memInventory());
1081 #ifdef RTS_GTK_FRONTPANEL
1082 if (RtsFlags.GcFlags.frontpanel) {
1083 updateFrontPanelAfterGC( N, live );
1087 // ok, GC over: tell the stats department what happened.
1088 stat_endGC(allocated, collected, live, copied, N);
1090 #if defined(RTS_USER_SIGNALS)
1091 // unblock signals again
1092 unblockUserSignals();
1099 /* -----------------------------------------------------------------------------
1102 traverse_weak_ptr_list is called possibly many times during garbage
1103 collection. It returns a flag indicating whether it did any work
1104 (i.e. called evacuate on any live pointers).
1106 Invariant: traverse_weak_ptr_list is called when the heap is in an
1107 idempotent state. That means that there are no pending
1108 evacuate/scavenge operations. This invariant helps the weak
1109 pointer code decide which weak pointers are dead - if there are no
1110 new live weak pointers, then all the currently unreachable ones are
1113 For generational GC: we just don't try to finalize weak pointers in
1114 older generations than the one we're collecting. This could
1115 probably be optimised by keeping per-generation lists of weak
1116 pointers, but for a few weak pointers this scheme will work.
1118 There are three distinct stages to processing weak pointers:
1120 - weak_stage == WeakPtrs
1122 We process all the weak pointers whos keys are alive (evacuate
1123 their values and finalizers), and repeat until we can find no new
1124 live keys. If no live keys are found in this pass, then we
1125 evacuate the finalizers of all the dead weak pointers in order to
1128 - weak_stage == WeakThreads
1130 Now, we discover which *threads* are still alive. Pointers to
1131 threads from the all_threads and main thread lists are the
1132 weakest of all: a pointers from the finalizer of a dead weak
1133 pointer can keep a thread alive. Any threads found to be unreachable
1134 are evacuated and placed on the resurrected_threads list so we
1135 can send them a signal later.
1137 - weak_stage == WeakDone
1139 No more evacuation is done.
1141 -------------------------------------------------------------------------- */
1144 traverse_weak_ptr_list(void)
1146 StgWeak *w, **last_w, *next_w;
1148 rtsBool flag = rtsFalse;
1150 switch (weak_stage) {
1156 /* doesn't matter where we evacuate values/finalizers to, since
1157 * these pointers are treated as roots (iff the keys are alive).
1161 last_w = &old_weak_ptr_list;
1162 for (w = old_weak_ptr_list; w != NULL; w = next_w) {
1164 /* There might be a DEAD_WEAK on the list if finalizeWeak# was
1165 * called on a live weak pointer object. Just remove it.
1167 if (w->header.info == &stg_DEAD_WEAK_info) {
1168 next_w = ((StgDeadWeak *)w)->link;
1173 switch (get_itbl(w)->type) {
1176 next_w = (StgWeak *)((StgEvacuated *)w)->evacuee;
1181 /* Now, check whether the key is reachable.
1183 new = isAlive(w->key);
1186 // evacuate the value and finalizer
1187 w->value = evacuate(w->value);
1188 w->finalizer = evacuate(w->finalizer);
1189 // remove this weak ptr from the old_weak_ptr list
1191 // and put it on the new weak ptr list
1193 w->link = weak_ptr_list;
1196 IF_DEBUG(weak, belch("Weak pointer still alive at %p -> %p",
1201 last_w = &(w->link);
1207 barf("traverse_weak_ptr_list: not WEAK");
1211 /* If we didn't make any changes, then we can go round and kill all
1212 * the dead weak pointers. The old_weak_ptr list is used as a list
1213 * of pending finalizers later on.
1215 if (flag == rtsFalse) {
1216 for (w = old_weak_ptr_list; w; w = w->link) {
1217 w->finalizer = evacuate(w->finalizer);
1220 // Next, move to the WeakThreads stage after fully
1221 // scavenging the finalizers we've just evacuated.
1222 weak_stage = WeakThreads;
1228 /* Now deal with the all_threads list, which behaves somewhat like
1229 * the weak ptr list. If we discover any threads that are about to
1230 * become garbage, we wake them up and administer an exception.
1233 StgTSO *t, *tmp, *next, **prev;
1235 prev = &old_all_threads;
1236 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1238 (StgClosure *)tmp = isAlive((StgClosure *)t);
1244 ASSERT(get_itbl(t)->type == TSO);
1245 switch (t->what_next) {
1246 case ThreadRelocated:
1251 case ThreadComplete:
1252 // finshed or died. The thread might still be alive, but we
1253 // don't keep it on the all_threads list. Don't forget to
1254 // stub out its global_link field.
1255 next = t->global_link;
1256 t->global_link = END_TSO_QUEUE;
1264 // not alive (yet): leave this thread on the
1265 // old_all_threads list.
1266 prev = &(t->global_link);
1267 next = t->global_link;
1270 // alive: move this thread onto the all_threads list.
1271 next = t->global_link;
1272 t->global_link = all_threads;
1279 /* And resurrect any threads which were about to become garbage.
1282 StgTSO *t, *tmp, *next;
1283 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1284 next = t->global_link;
1285 (StgClosure *)tmp = evacuate((StgClosure *)t);
1286 tmp->global_link = resurrected_threads;
1287 resurrected_threads = tmp;
1291 weak_stage = WeakDone; // *now* we're done,
1292 return rtsTrue; // but one more round of scavenging, please
1295 barf("traverse_weak_ptr_list");
1300 /* -----------------------------------------------------------------------------
1301 After GC, the live weak pointer list may have forwarding pointers
1302 on it, because a weak pointer object was evacuated after being
1303 moved to the live weak pointer list. We remove those forwarding
1306 Also, we don't consider weak pointer objects to be reachable, but
1307 we must nevertheless consider them to be "live" and retain them.
1308 Therefore any weak pointer objects which haven't as yet been
1309 evacuated need to be evacuated now.
1310 -------------------------------------------------------------------------- */
1314 mark_weak_ptr_list ( StgWeak **list )
1316 StgWeak *w, **last_w;
1319 for (w = *list; w; w = w->link) {
1320 // w might be WEAK, EVACUATED, or DEAD_WEAK (actually CON_STATIC) here
1321 ASSERT(w->header.info == &stg_DEAD_WEAK_info
1322 || get_itbl(w)->type == WEAK || get_itbl(w)->type == EVACUATED);
1323 (StgClosure *)w = evacuate((StgClosure *)w);
1325 last_w = &(w->link);
1329 /* -----------------------------------------------------------------------------
1330 isAlive determines whether the given closure is still alive (after
1331 a garbage collection) or not. It returns the new address of the
1332 closure if it is alive, or NULL otherwise.
1334 NOTE: Use it before compaction only!
1335 -------------------------------------------------------------------------- */
1339 isAlive(StgClosure *p)
1341 const StgInfoTable *info;
1346 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
1349 // ignore static closures
1351 // ToDo: for static closures, check the static link field.
1352 // Problem here is that we sometimes don't set the link field, eg.
1353 // for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
1355 if (!HEAP_ALLOCED(p)) {
1359 // ignore closures in generations that we're not collecting.
1361 if (bd->gen_no > N) {
1365 // if it's a pointer into to-space, then we're done
1366 if (bd->flags & BF_EVACUATED) {
1370 // large objects use the evacuated flag
1371 if (bd->flags & BF_LARGE) {
1375 // check the mark bit for compacted steps
1376 if (bd->step->is_compacted && is_marked((P_)p,bd)) {
1380 switch (info->type) {
1385 case IND_OLDGEN: // rely on compatible layout with StgInd
1386 case IND_OLDGEN_PERM:
1387 // follow indirections
1388 p = ((StgInd *)p)->indirectee;
1393 return ((StgEvacuated *)p)->evacuee;
1396 if (((StgTSO *)p)->what_next == ThreadRelocated) {
1397 p = (StgClosure *)((StgTSO *)p)->link;
1410 mark_root(StgClosure **root)
1412 *root = evacuate(*root);
1415 static __inline__ void
1416 upd_evacuee(StgClosure *p, StgClosure *dest)
1418 // Source object must be in from-space:
1419 ASSERT((Bdescr((P_)p)->flags & BF_EVACUATED) == 0);
1420 // not true: (ToDo: perhaps it should be)
1421 // ASSERT(Bdescr((P_)dest)->flags & BF_EVACUATED);
1422 p->header.info = &stg_EVACUATED_info;
1423 ((StgEvacuated *)p)->evacuee = dest;
1427 static __inline__ StgClosure *
1428 copy(StgClosure *src, nat size, step *stp)
1433 nat size_org = size;
1436 TICK_GC_WORDS_COPIED(size);
1437 /* Find out where we're going, using the handy "to" pointer in
1438 * the step of the source object. If it turns out we need to
1439 * evacuate to an older generation, adjust it here (see comment
1442 if (stp->gen_no < evac_gen) {
1443 #ifdef NO_EAGER_PROMOTION
1444 failed_to_evac = rtsTrue;
1446 stp = &generations[evac_gen].steps[0];
1450 /* chain a new block onto the to-space for the destination step if
1453 if (stp->hp + size >= stp->hpLim) {
1454 gc_alloc_block(stp);
1457 for(to = stp->hp, from = (P_)src; size>0; --size) {
1463 upd_evacuee(src,(StgClosure *)dest);
1465 // We store the size of the just evacuated object in the LDV word so that
1466 // the profiler can guess the position of the next object later.
1467 SET_EVACUAEE_FOR_LDV(src, size_org);
1469 return (StgClosure *)dest;
1472 /* Special version of copy() for when we only want to copy the info
1473 * pointer of an object, but reserve some padding after it. This is
1474 * used to optimise evacuation of BLACKHOLEs.
1479 copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *stp)
1484 nat size_to_copy_org = size_to_copy;
1487 TICK_GC_WORDS_COPIED(size_to_copy);
1488 if (stp->gen_no < evac_gen) {
1489 #ifdef NO_EAGER_PROMOTION
1490 failed_to_evac = rtsTrue;
1492 stp = &generations[evac_gen].steps[0];
1496 if (stp->hp + size_to_reserve >= stp->hpLim) {
1497 gc_alloc_block(stp);
1500 for(to = stp->hp, from = (P_)src; size_to_copy>0; --size_to_copy) {
1505 stp->hp += size_to_reserve;
1506 upd_evacuee(src,(StgClosure *)dest);
1508 // We store the size of the just evacuated object in the LDV word so that
1509 // the profiler can guess the position of the next object later.
1510 // size_to_copy_org is wrong because the closure already occupies size_to_reserve
1512 SET_EVACUAEE_FOR_LDV(src, size_to_reserve);
1514 if (size_to_reserve - size_to_copy_org > 0)
1515 FILL_SLOP(stp->hp - 1, (int)(size_to_reserve - size_to_copy_org));
1517 return (StgClosure *)dest;
1521 /* -----------------------------------------------------------------------------
1522 Evacuate a large object
1524 This just consists of removing the object from the (doubly-linked)
1525 step->large_objects list, and linking it on to the (singly-linked)
1526 step->new_large_objects list, from where it will be scavenged later.
1528 Convention: bd->flags has BF_EVACUATED set for a large object
1529 that has been evacuated, or unset otherwise.
1530 -------------------------------------------------------------------------- */
1534 evacuate_large(StgPtr p)
1536 bdescr *bd = Bdescr(p);
1539 // object must be at the beginning of the block (or be a ByteArray)
1540 ASSERT(get_itbl((StgClosure *)p)->type == ARR_WORDS ||
1541 (((W_)p & BLOCK_MASK) == 0));
1543 // already evacuated?
1544 if (bd->flags & BF_EVACUATED) {
1545 /* Don't forget to set the failed_to_evac flag if we didn't get
1546 * the desired destination (see comments in evacuate()).
1548 if (bd->gen_no < evac_gen) {
1549 failed_to_evac = rtsTrue;
1550 TICK_GC_FAILED_PROMOTION();
1556 // remove from large_object list
1558 bd->u.back->link = bd->link;
1559 } else { // first object in the list
1560 stp->large_objects = bd->link;
1563 bd->link->u.back = bd->u.back;
1566 /* link it on to the evacuated large object list of the destination step
1569 if (stp->gen_no < evac_gen) {
1570 #ifdef NO_EAGER_PROMOTION
1571 failed_to_evac = rtsTrue;
1573 stp = &generations[evac_gen].steps[0];
1578 bd->gen_no = stp->gen_no;
1579 bd->link = stp->new_large_objects;
1580 stp->new_large_objects = bd;
1581 bd->flags |= BF_EVACUATED;
1584 /* -----------------------------------------------------------------------------
1585 Adding a MUT_CONS to an older generation.
1587 This is necessary from time to time when we end up with an
1588 old-to-new generation pointer in a non-mutable object. We defer
1589 the promotion until the next GC.
1590 -------------------------------------------------------------------------- */
1593 mkMutCons(StgClosure *ptr, generation *gen)
1598 stp = &gen->steps[0];
1600 /* chain a new block onto the to-space for the destination step if
1603 if (stp->hp + sizeofW(StgIndOldGen) >= stp->hpLim) {
1604 gc_alloc_block(stp);
1607 q = (StgMutVar *)stp->hp;
1608 stp->hp += sizeofW(StgMutVar);
1610 SET_HDR(q,&stg_MUT_CONS_info,CCS_GC);
1612 recordOldToNewPtrs((StgMutClosure *)q);
1614 return (StgClosure *)q;
1617 /* -----------------------------------------------------------------------------
1620 This is called (eventually) for every live object in the system.
1622 The caller to evacuate specifies a desired generation in the
1623 evac_gen global variable. The following conditions apply to
1624 evacuating an object which resides in generation M when we're
1625 collecting up to generation N
1629 else evac to step->to
1631 if M < evac_gen evac to evac_gen, step 0
1633 if the object is already evacuated, then we check which generation
1636 if M >= evac_gen do nothing
1637 if M < evac_gen set failed_to_evac flag to indicate that we
1638 didn't manage to evacuate this object into evac_gen.
1643 evacuate() is the single most important function performance-wise
1644 in the GC. Various things have been tried to speed it up, but as
1645 far as I can tell the code generated by gcc 3.2 with -O2 is about
1646 as good as it's going to get. We pass the argument to evacuate()
1647 in a register using the 'regparm' attribute (see the prototype for
1648 evacuate() near the top of this file).
1650 Changing evacuate() to take an (StgClosure **) rather than
1651 returning the new pointer seems attractive, because we can avoid
1652 writing back the pointer when it hasn't changed (eg. for a static
1653 object, or an object in a generation > N). However, I tried it and
1654 it doesn't help. One reason is that the (StgClosure **) pointer
1655 gets spilled to the stack inside evacuate(), resulting in far more
1656 extra reads/writes than we save.
1657 -------------------------------------------------------------------------- */
1660 evacuate(StgClosure *q)
1665 const StgInfoTable *info;
1668 if (HEAP_ALLOCED(q)) {
1671 if (bd->gen_no > N) {
1672 /* Can't evacuate this object, because it's in a generation
1673 * older than the ones we're collecting. Let's hope that it's
1674 * in evac_gen or older, or we will have to arrange to track
1675 * this pointer using the mutable list.
1677 if (bd->gen_no < evac_gen) {
1679 failed_to_evac = rtsTrue;
1680 TICK_GC_FAILED_PROMOTION();
1685 /* evacuate large objects by re-linking them onto a different list.
1687 if (bd->flags & BF_LARGE) {
1689 if (info->type == TSO &&
1690 ((StgTSO *)q)->what_next == ThreadRelocated) {
1691 q = (StgClosure *)((StgTSO *)q)->link;
1694 evacuate_large((P_)q);
1698 /* If the object is in a step that we're compacting, then we
1699 * need to use an alternative evacuate procedure.
1701 if (bd->step->is_compacted) {
1702 if (!is_marked((P_)q,bd)) {
1704 if (mark_stack_full()) {
1705 mark_stack_overflowed = rtsTrue;
1708 push_mark_stack((P_)q);
1716 else stp = NULL; // make sure copy() will crash if HEAP_ALLOCED is wrong
1719 // make sure the info pointer is into text space
1720 ASSERT(LOOKS_LIKE_CLOSURE_PTR(q));
1723 switch (info -> type) {
1727 return copy(q,sizeW_fromITBL(info),stp);
1731 StgWord w = (StgWord)q->payload[0];
1732 if (q->header.info == Czh_con_info &&
1733 // unsigned, so always true: (StgChar)w >= MIN_CHARLIKE &&
1734 (StgChar)w <= MAX_CHARLIKE) {
1735 return (StgClosure *)CHARLIKE_CLOSURE((StgChar)w);
1737 if (q->header.info == Izh_con_info &&
1738 (StgInt)w >= MIN_INTLIKE && (StgInt)w <= MAX_INTLIKE) {
1739 return (StgClosure *)INTLIKE_CLOSURE((StgInt)w);
1741 // else, fall through ...
1747 return copy(q,sizeofW(StgHeader)+1,stp);
1749 case THUNK_1_0: // here because of MIN_UPD_SIZE
1754 #ifdef NO_PROMOTE_THUNKS
1755 if (bd->gen_no == 0 &&
1756 bd->step->no != 0 &&
1757 bd->step->no == generations[bd->gen_no].n_steps-1) {
1761 return copy(q,sizeofW(StgHeader)+2,stp);
1769 return copy(q,sizeofW(StgHeader)+2,stp);
1775 case IND_OLDGEN_PERM:
1779 return copy(q,sizeW_fromITBL(info),stp);
1782 return copy(q,bco_sizeW((StgBCO *)q),stp);
1785 case SE_CAF_BLACKHOLE:
1788 return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
1791 to = copy(q,BLACKHOLE_sizeW(),stp);
1794 case THUNK_SELECTOR:
1798 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
1799 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1802 p = eval_thunk_selector(info->layout.selector_offset,
1806 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1808 // q is still BLACKHOLE'd.
1809 thunk_selector_depth++;
1811 thunk_selector_depth--;
1814 // We store the size of the just evacuated object in the
1815 // LDV word so that the profiler can guess the position of
1816 // the next object later.
1817 SET_EVACUAEE_FOR_LDV(q, THUNK_SELECTOR_sizeW());
1825 // follow chains of indirections, don't evacuate them
1826 q = ((StgInd*)q)->indirectee;
1830 if (info->srt_bitmap != 0 && major_gc &&
1831 THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
1832 THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
1833 static_objects = (StgClosure *)q;
1838 if (info->srt_bitmap != 0 && major_gc &&
1839 FUN_STATIC_LINK((StgClosure *)q) == NULL) {
1840 FUN_STATIC_LINK((StgClosure *)q) = static_objects;
1841 static_objects = (StgClosure *)q;
1846 /* If q->saved_info != NULL, then it's a revertible CAF - it'll be
1847 * on the CAF list, so don't do anything with it here (we'll
1848 * scavenge it later).
1851 && ((StgIndStatic *)q)->saved_info == NULL
1852 && IND_STATIC_LINK((StgClosure *)q) == NULL) {
1853 IND_STATIC_LINK((StgClosure *)q) = static_objects;
1854 static_objects = (StgClosure *)q;
1859 if (major_gc && STATIC_LINK(info,(StgClosure *)q) == NULL) {
1860 STATIC_LINK(info,(StgClosure *)q) = static_objects;
1861 static_objects = (StgClosure *)q;
1865 case CONSTR_INTLIKE:
1866 case CONSTR_CHARLIKE:
1867 case CONSTR_NOCAF_STATIC:
1868 /* no need to put these on the static linked list, they don't need
1882 // shouldn't see these
1883 barf("evacuate: stack frame at %p\n", q);
1887 return copy(q,pap_sizeW((StgPAP*)q),stp);
1890 return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp);
1893 /* Already evacuated, just return the forwarding address.
1894 * HOWEVER: if the requested destination generation (evac_gen) is
1895 * older than the actual generation (because the object was
1896 * already evacuated to a younger generation) then we have to
1897 * set the failed_to_evac flag to indicate that we couldn't
1898 * manage to promote the object to the desired generation.
1900 if (evac_gen > 0) { // optimisation
1901 StgClosure *p = ((StgEvacuated*)q)->evacuee;
1902 if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < evac_gen) {
1903 failed_to_evac = rtsTrue;
1904 TICK_GC_FAILED_PROMOTION();
1907 return ((StgEvacuated*)q)->evacuee;
1910 // just copy the block
1911 return copy(q,arr_words_sizeW((StgArrWords *)q),stp);
1914 case MUT_ARR_PTRS_FROZEN:
1915 // just copy the block
1916 return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
1920 StgTSO *tso = (StgTSO *)q;
1922 /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
1924 if (tso->what_next == ThreadRelocated) {
1925 q = (StgClosure *)tso->link;
1929 /* To evacuate a small TSO, we need to relocate the update frame
1933 StgTSO *new_tso = (StgTSO *)copy((StgClosure *)tso,tso_sizeW(tso),stp);
1934 move_TSO(tso, new_tso);
1935 return (StgClosure *)new_tso;
1940 case RBH: // cf. BLACKHOLE_BQ
1942 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
1943 to = copy(q,BLACKHOLE_sizeW(),stp);
1944 //ToDo: derive size etc from reverted IP
1945 //to = copy(q,size,stp);
1947 belch("@@ evacuate: RBH %p (%s) to %p (%s)",
1948 q, info_type(q), to, info_type(to)));
1953 ASSERT(sizeofW(StgBlockedFetch) >= MIN_NONUPD_SIZE);
1954 to = copy(q,sizeofW(StgBlockedFetch),stp);
1956 belch("@@ evacuate: %p (%s) to %p (%s)",
1957 q, info_type(q), to, info_type(to)));
1964 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1965 to = copy(q,sizeofW(StgFetchMe),stp);
1967 belch("@@ evacuate: %p (%s) to %p (%s)",
1968 q, info_type(q), to, info_type(to)));
1972 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1973 to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
1975 belch("@@ evacuate: %p (%s) to %p (%s)",
1976 q, info_type(q), to, info_type(to)));
1981 barf("evacuate: strange closure type %d", (int)(info->type));
1987 /* -----------------------------------------------------------------------------
1988 Evaluate a THUNK_SELECTOR if possible.
1990 returns: NULL if we couldn't evaluate this THUNK_SELECTOR, or
1991 a closure pointer if we evaluated it and this is the result. Note
1992 that "evaluating" the THUNK_SELECTOR doesn't necessarily mean
1993 reducing it to HNF, just that we have eliminated the selection.
1994 The result might be another thunk, or even another THUNK_SELECTOR.
1996 If the return value is non-NULL, the original selector thunk has
1997 been BLACKHOLE'd, and should be updated with an indirection or a
1998 forwarding pointer. If the return value is NULL, then the selector
2000 -------------------------------------------------------------------------- */
2003 eval_thunk_selector( nat field, StgSelector * p )
2006 const StgInfoTable *info_ptr;
2007 StgClosure *selectee;
2009 selectee = p->selectee;
2011 // Save the real info pointer (NOTE: not the same as get_itbl()).
2012 info_ptr = p->header.info;
2014 // If the THUNK_SELECTOR is in a generation that we are not
2015 // collecting, then bail out early. We won't be able to save any
2016 // space in any case, and updating with an indirection is trickier
2018 if (Bdescr((StgPtr)p)->gen_no > N) {
2022 // BLACKHOLE the selector thunk, since it is now under evaluation.
2023 // This is important to stop us going into an infinite loop if
2024 // this selector thunk eventually refers to itself.
2025 SET_INFO(p,&stg_BLACKHOLE_info);
2029 // We don't want to end up in to-space, because this causes
2030 // problems when the GC later tries to evacuate the result of
2031 // eval_thunk_selector(). There are various ways this could
2034 // - following an IND_STATIC
2036 // - when the old generation is compacted, the mark phase updates
2037 // from-space pointers to be to-space pointers, and we can't
2038 // reliably tell which we're following (eg. from an IND_STATIC).
2040 // So we use the block-descriptor test to find out if we're in
2043 if (HEAP_ALLOCED(selectee) &&
2044 Bdescr((StgPtr)selectee)->flags & BF_EVACUATED) {
2048 info = get_itbl(selectee);
2049 switch (info->type) {
2057 case CONSTR_NOCAF_STATIC:
2058 // check that the size is in range
2059 ASSERT(field < (StgWord32)(info->layout.payload.ptrs +
2060 info->layout.payload.nptrs));
2062 // ToDo: shouldn't we test whether this pointer is in
2064 return selectee->payload[field];
2069 case IND_OLDGEN_PERM:
2071 selectee = ((StgInd *)selectee)->indirectee;
2075 // We don't follow pointers into to-space; the constructor
2076 // has already been evacuated, so we won't save any space
2077 // leaks by evaluating this selector thunk anyhow.
2080 case THUNK_SELECTOR:
2084 // check that we don't recurse too much, re-using the
2085 // depth bound also used in evacuate().
2086 thunk_selector_depth++;
2087 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
2091 val = eval_thunk_selector(info->layout.selector_offset,
2092 (StgSelector *)selectee);
2094 thunk_selector_depth--;
2099 // We evaluated this selector thunk, so update it with
2100 // an indirection. NOTE: we don't use UPD_IND here,
2101 // because we are guaranteed that p is in a generation
2102 // that we are collecting, and we never want to put the
2103 // indirection on a mutable list.
2105 // For the purposes of LDV profiling, we have destroyed
2106 // the original selector thunk.
2107 SET_INFO(p, info_ptr);
2108 LDV_recordDead_FILL_SLOP_DYNAMIC(selectee);
2110 ((StgInd *)selectee)->indirectee = val;
2111 SET_INFO(selectee,&stg_IND_info);
2113 // For the purposes of LDV profiling, we have created an
2115 LDV_recordCreate(selectee);
2131 case SE_CAF_BLACKHOLE:
2144 // not evaluated yet
2148 barf("eval_thunk_selector: strange selectee %d",
2153 // We didn't manage to evaluate this thunk; restore the old info pointer
2154 SET_INFO(p, info_ptr);
2158 /* -----------------------------------------------------------------------------
2159 move_TSO is called to update the TSO structure after it has been
2160 moved from one place to another.
2161 -------------------------------------------------------------------------- */
2164 move_TSO (StgTSO *src, StgTSO *dest)
2168 // relocate the stack pointers...
2169 diff = (StgPtr)dest - (StgPtr)src; // In *words*
2170 dest->sp = (StgPtr)dest->sp + diff;
2173 /* Similar to scavenge_large_bitmap(), but we don't write back the
2174 * pointers we get back from evacuate().
2177 scavenge_large_srt_bitmap( StgLargeSRT *large_srt )
2184 bitmap = large_srt->l.bitmap[b];
2185 size = (nat)large_srt->l.size;
2187 for (i = 0; i < size; ) {
2188 if ((bitmap & 1) != 0) {
2193 if (i % BITS_IN(W_) == 0) {
2195 bitmap = large_srt->l.bitmap[b];
2197 bitmap = bitmap >> 1;
2202 /* evacuate the SRT. If srt_bitmap is zero, then there isn't an
2203 * srt field in the info table. That's ok, because we'll
2204 * never dereference it.
2207 scavenge_srt (StgClosure **srt, nat srt_bitmap)
2212 bitmap = srt_bitmap;
2215 if (bitmap == (StgHalfWord)(-1)) {
2216 scavenge_large_srt_bitmap( (StgLargeSRT *)srt );
2220 while (bitmap != 0) {
2221 if ((bitmap & 1) != 0) {
2222 #ifdef ENABLE_WIN32_DLL_SUPPORT
2223 // Special-case to handle references to closures hiding out in DLLs, since
2224 // double indirections required to get at those. The code generator knows
2225 // which is which when generating the SRT, so it stores the (indirect)
2226 // reference to the DLL closure in the table by first adding one to it.
2227 // We check for this here, and undo the addition before evacuating it.
2229 // If the SRT entry hasn't got bit 0 set, the SRT entry points to a
2230 // closure that's fixed at link-time, and no extra magic is required.
2231 if ( (unsigned long)(*srt) & 0x1 ) {
2232 evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
2241 bitmap = bitmap >> 1;
2247 scavenge_thunk_srt(const StgInfoTable *info)
2249 StgThunkInfoTable *thunk_info;
2251 thunk_info = itbl_to_thunk_itbl(info);
2252 scavenge_srt((StgClosure **)thunk_info->srt, thunk_info->i.srt_bitmap);
2256 scavenge_fun_srt(const StgInfoTable *info)
2258 StgFunInfoTable *fun_info;
2260 fun_info = itbl_to_fun_itbl(info);
2261 scavenge_srt((StgClosure **)fun_info->srt, fun_info->i.srt_bitmap);
2265 scavenge_ret_srt(const StgInfoTable *info)
2267 StgRetInfoTable *ret_info;
2269 ret_info = itbl_to_ret_itbl(info);
2270 scavenge_srt((StgClosure **)ret_info->srt, ret_info->i.srt_bitmap);
2273 /* -----------------------------------------------------------------------------
2275 -------------------------------------------------------------------------- */
2278 scavengeTSO (StgTSO *tso)
2280 // chase the link field for any TSOs on the same queue
2281 (StgClosure *)tso->link = evacuate((StgClosure *)tso->link);
2282 if ( tso->why_blocked == BlockedOnMVar
2283 || tso->why_blocked == BlockedOnBlackHole
2284 || tso->why_blocked == BlockedOnException
2286 || tso->why_blocked == BlockedOnGA
2287 || tso->why_blocked == BlockedOnGA_NoSend
2290 tso->block_info.closure = evacuate(tso->block_info.closure);
2292 if ( tso->blocked_exceptions != NULL ) {
2293 tso->blocked_exceptions =
2294 (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
2297 // scavenge this thread's stack
2298 scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
2301 /* -----------------------------------------------------------------------------
2302 Blocks of function args occur on the stack (at the top) and
2304 -------------------------------------------------------------------------- */
2306 static inline StgPtr
2307 scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
2314 switch (fun_info->fun_type) {
2316 bitmap = BITMAP_BITS(fun_info->bitmap);
2317 size = BITMAP_SIZE(fun_info->bitmap);
2320 size = ((StgLargeBitmap *)fun_info->bitmap)->size;
2321 scavenge_large_bitmap(p, (StgLargeBitmap *)fun_info->bitmap, size);
2325 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->fun_type]);
2326 size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->fun_type]);
2329 if ((bitmap & 1) == 0) {
2330 (StgClosure *)*p = evacuate((StgClosure *)*p);
2333 bitmap = bitmap >> 1;
2341 static inline StgPtr
2342 scavenge_PAP (StgPAP *pap)
2345 StgWord bitmap, size;
2346 StgFunInfoTable *fun_info;
2348 pap->fun = evacuate(pap->fun);
2349 fun_info = get_fun_itbl(pap->fun);
2350 ASSERT(fun_info->i.type != PAP);
2352 p = (StgPtr)pap->payload;
2355 switch (fun_info->fun_type) {
2357 bitmap = BITMAP_BITS(fun_info->bitmap);
2360 scavenge_large_bitmap(p, (StgLargeBitmap *)fun_info->bitmap, size);
2364 scavenge_large_bitmap((StgPtr)pap->payload, BCO_BITMAP(pap->fun), size);
2368 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->fun_type]);
2372 if ((bitmap & 1) == 0) {
2373 (StgClosure *)*p = evacuate((StgClosure *)*p);
2376 bitmap = bitmap >> 1;
2384 /* -----------------------------------------------------------------------------
2385 Scavenge a given step until there are no more objects in this step
2388 evac_gen is set by the caller to be either zero (for a step in a
2389 generation < N) or G where G is the generation of the step being
2392 We sometimes temporarily change evac_gen back to zero if we're
2393 scavenging a mutable object where early promotion isn't such a good
2395 -------------------------------------------------------------------------- */
2403 nat saved_evac_gen = evac_gen;
2408 failed_to_evac = rtsFalse;
2410 /* scavenge phase - standard breadth-first scavenging of the
2414 while (bd != stp->hp_bd || p < stp->hp) {
2416 // If we're at the end of this block, move on to the next block
2417 if (bd != stp->hp_bd && p == bd->free) {
2423 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2424 info = get_itbl((StgClosure *)p);
2426 ASSERT(thunk_selector_depth == 0);
2429 switch (info->type) {
2432 /* treat MVars specially, because we don't want to evacuate the
2433 * mut_link field in the middle of the closure.
2436 StgMVar *mvar = ((StgMVar *)p);
2438 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
2439 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
2440 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
2441 evac_gen = saved_evac_gen;
2442 recordMutable((StgMutClosure *)mvar);
2443 failed_to_evac = rtsFalse; // mutable.
2444 p += sizeofW(StgMVar);
2449 scavenge_fun_srt(info);
2450 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2451 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2452 p += sizeofW(StgHeader) + 2;
2456 scavenge_thunk_srt(info);
2458 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2459 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2460 p += sizeofW(StgHeader) + 2;
2464 scavenge_thunk_srt(info);
2465 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2466 p += sizeofW(StgHeader) + 2; // MIN_UPD_SIZE
2470 scavenge_fun_srt(info);
2472 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2473 p += sizeofW(StgHeader) + 1;
2477 scavenge_thunk_srt(info);
2478 p += sizeofW(StgHeader) + 2; // MIN_UPD_SIZE
2482 scavenge_fun_srt(info);
2484 p += sizeofW(StgHeader) + 1;
2488 scavenge_thunk_srt(info);
2489 p += sizeofW(StgHeader) + 2;
2493 scavenge_fun_srt(info);
2495 p += sizeofW(StgHeader) + 2;
2499 scavenge_thunk_srt(info);
2500 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2501 p += sizeofW(StgHeader) + 2;
2505 scavenge_fun_srt(info);
2507 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2508 p += sizeofW(StgHeader) + 2;
2512 scavenge_fun_srt(info);
2516 scavenge_thunk_srt(info);
2527 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2528 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2529 (StgClosure *)*p = evacuate((StgClosure *)*p);
2531 p += info->layout.payload.nptrs;
2536 StgBCO *bco = (StgBCO *)p;
2537 (StgClosure *)bco->instrs = evacuate((StgClosure *)bco->instrs);
2538 (StgClosure *)bco->literals = evacuate((StgClosure *)bco->literals);
2539 (StgClosure *)bco->ptrs = evacuate((StgClosure *)bco->ptrs);
2540 (StgClosure *)bco->itbls = evacuate((StgClosure *)bco->itbls);
2541 p += bco_sizeW(bco);
2546 if (stp->gen->no != 0) {
2549 // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an
2550 // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
2551 LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
2554 // Todo: maybe use SET_HDR() and remove LDV_recordCreate()?
2556 SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
2559 // We pretend that p has just been created.
2560 LDV_recordCreate((StgClosure *)p);
2564 case IND_OLDGEN_PERM:
2565 ((StgIndOldGen *)p)->indirectee =
2566 evacuate(((StgIndOldGen *)p)->indirectee);
2567 if (failed_to_evac) {
2568 failed_to_evac = rtsFalse;
2569 recordOldToNewPtrs((StgMutClosure *)p);
2571 p += sizeofW(StgIndOldGen);
2576 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2577 evac_gen = saved_evac_gen;
2578 recordMutable((StgMutClosure *)p);
2579 failed_to_evac = rtsFalse; // mutable anyhow
2580 p += sizeofW(StgMutVar);
2585 failed_to_evac = rtsFalse; // mutable anyhow
2586 p += sizeofW(StgMutVar);
2590 case SE_CAF_BLACKHOLE:
2593 p += BLACKHOLE_sizeW();
2598 StgBlockingQueue *bh = (StgBlockingQueue *)p;
2599 (StgClosure *)bh->blocking_queue =
2600 evacuate((StgClosure *)bh->blocking_queue);
2601 recordMutable((StgMutClosure *)bh);
2602 failed_to_evac = rtsFalse;
2603 p += BLACKHOLE_sizeW();
2607 case THUNK_SELECTOR:
2609 StgSelector *s = (StgSelector *)p;
2610 s->selectee = evacuate(s->selectee);
2611 p += THUNK_SELECTOR_sizeW();
2615 // A chunk of stack saved in a heap object
2618 StgAP_STACK *ap = (StgAP_STACK *)p;
2620 ap->fun = evacuate(ap->fun);
2621 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2622 p = (StgPtr)ap->payload + ap->size;
2628 p = scavenge_PAP((StgPAP *)p);
2632 // nothing to follow
2633 p += arr_words_sizeW((StgArrWords *)p);
2637 // follow everything
2641 evac_gen = 0; // repeatedly mutable
2642 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2643 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2644 (StgClosure *)*p = evacuate((StgClosure *)*p);
2646 evac_gen = saved_evac_gen;
2647 recordMutable((StgMutClosure *)q);
2648 failed_to_evac = rtsFalse; // mutable anyhow.
2652 case MUT_ARR_PTRS_FROZEN:
2653 // follow everything
2657 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2658 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2659 (StgClosure *)*p = evacuate((StgClosure *)*p);
2661 // it's tempting to recordMutable() if failed_to_evac is
2662 // false, but that breaks some assumptions (eg. every
2663 // closure on the mutable list is supposed to have the MUT
2664 // flag set, and MUT_ARR_PTRS_FROZEN doesn't).
2670 StgTSO *tso = (StgTSO *)p;
2673 evac_gen = saved_evac_gen;
2674 recordMutable((StgMutClosure *)tso);
2675 failed_to_evac = rtsFalse; // mutable anyhow.
2676 p += tso_sizeW(tso);
2681 case RBH: // cf. BLACKHOLE_BQ
2684 nat size, ptrs, nonptrs, vhs;
2686 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2688 StgRBH *rbh = (StgRBH *)p;
2689 (StgClosure *)rbh->blocking_queue =
2690 evacuate((StgClosure *)rbh->blocking_queue);
2691 recordMutable((StgMutClosure *)to);
2692 failed_to_evac = rtsFalse; // mutable anyhow.
2694 belch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2695 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2696 // ToDo: use size of reverted closure here!
2697 p += BLACKHOLE_sizeW();
2703 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2704 // follow the pointer to the node which is being demanded
2705 (StgClosure *)bf->node =
2706 evacuate((StgClosure *)bf->node);
2707 // follow the link to the rest of the blocking queue
2708 (StgClosure *)bf->link =
2709 evacuate((StgClosure *)bf->link);
2710 if (failed_to_evac) {
2711 failed_to_evac = rtsFalse;
2712 recordMutable((StgMutClosure *)bf);
2715 belch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
2716 bf, info_type((StgClosure *)bf),
2717 bf->node, info_type(bf->node)));
2718 p += sizeofW(StgBlockedFetch);
2726 p += sizeofW(StgFetchMe);
2727 break; // nothing to do in this case
2729 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
2731 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
2732 (StgClosure *)fmbq->blocking_queue =
2733 evacuate((StgClosure *)fmbq->blocking_queue);
2734 if (failed_to_evac) {
2735 failed_to_evac = rtsFalse;
2736 recordMutable((StgMutClosure *)fmbq);
2739 belch("@@ scavenge: %p (%s) exciting, isn't it",
2740 p, info_type((StgClosure *)p)));
2741 p += sizeofW(StgFetchMeBlockingQueue);
2747 barf("scavenge: unimplemented/strange closure type %d @ %p",
2751 /* If we didn't manage to promote all the objects pointed to by
2752 * the current object, then we have to designate this object as
2753 * mutable (because it contains old-to-new generation pointers).
2755 if (failed_to_evac) {
2756 failed_to_evac = rtsFalse;
2757 mkMutCons((StgClosure *)q, &generations[evac_gen]);
2765 /* -----------------------------------------------------------------------------
2766 Scavenge everything on the mark stack.
2768 This is slightly different from scavenge():
2769 - we don't walk linearly through the objects, so the scavenger
2770 doesn't need to advance the pointer on to the next object.
2771 -------------------------------------------------------------------------- */
2774 scavenge_mark_stack(void)
2780 evac_gen = oldest_gen->no;
2781 saved_evac_gen = evac_gen;
2784 while (!mark_stack_empty()) {
2785 p = pop_mark_stack();
2787 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2788 info = get_itbl((StgClosure *)p);
2791 switch (info->type) {
2794 /* treat MVars specially, because we don't want to evacuate the
2795 * mut_link field in the middle of the closure.
2798 StgMVar *mvar = ((StgMVar *)p);
2800 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
2801 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
2802 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
2803 evac_gen = saved_evac_gen;
2804 failed_to_evac = rtsFalse; // mutable.
2809 scavenge_fun_srt(info);
2810 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2811 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2815 scavenge_thunk_srt(info);
2817 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2818 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2823 scavenge_fun_srt(info);
2824 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2829 scavenge_thunk_srt(info);
2832 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2837 scavenge_fun_srt(info);
2842 scavenge_thunk_srt(info);
2850 scavenge_fun_srt(info);
2854 scavenge_thunk_srt(info);
2865 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2866 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2867 (StgClosure *)*p = evacuate((StgClosure *)*p);
2873 StgBCO *bco = (StgBCO *)p;
2874 (StgClosure *)bco->instrs = evacuate((StgClosure *)bco->instrs);
2875 (StgClosure *)bco->literals = evacuate((StgClosure *)bco->literals);
2876 (StgClosure *)bco->ptrs = evacuate((StgClosure *)bco->ptrs);
2877 (StgClosure *)bco->itbls = evacuate((StgClosure *)bco->itbls);
2882 // don't need to do anything here: the only possible case
2883 // is that we're in a 1-space compacting collector, with
2884 // no "old" generation.
2888 case IND_OLDGEN_PERM:
2889 ((StgIndOldGen *)p)->indirectee =
2890 evacuate(((StgIndOldGen *)p)->indirectee);
2891 if (failed_to_evac) {
2892 recordOldToNewPtrs((StgMutClosure *)p);
2894 failed_to_evac = rtsFalse;
2899 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2900 evac_gen = saved_evac_gen;
2901 failed_to_evac = rtsFalse;
2906 failed_to_evac = rtsFalse;
2910 case SE_CAF_BLACKHOLE:
2918 StgBlockingQueue *bh = (StgBlockingQueue *)p;
2919 (StgClosure *)bh->blocking_queue =
2920 evacuate((StgClosure *)bh->blocking_queue);
2921 failed_to_evac = rtsFalse;
2925 case THUNK_SELECTOR:
2927 StgSelector *s = (StgSelector *)p;
2928 s->selectee = evacuate(s->selectee);
2932 // A chunk of stack saved in a heap object
2935 StgAP_STACK *ap = (StgAP_STACK *)p;
2937 ap->fun = evacuate(ap->fun);
2938 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2944 scavenge_PAP((StgPAP *)p);
2948 // follow everything
2952 evac_gen = 0; // repeatedly mutable
2953 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2954 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2955 (StgClosure *)*p = evacuate((StgClosure *)*p);
2957 evac_gen = saved_evac_gen;
2958 failed_to_evac = rtsFalse; // mutable anyhow.
2962 case MUT_ARR_PTRS_FROZEN:
2963 // follow everything
2967 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2968 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2969 (StgClosure *)*p = evacuate((StgClosure *)*p);
2976 StgTSO *tso = (StgTSO *)p;
2979 evac_gen = saved_evac_gen;
2980 failed_to_evac = rtsFalse;
2985 case RBH: // cf. BLACKHOLE_BQ
2988 nat size, ptrs, nonptrs, vhs;
2990 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2992 StgRBH *rbh = (StgRBH *)p;
2993 (StgClosure *)rbh->blocking_queue =
2994 evacuate((StgClosure *)rbh->blocking_queue);
2995 recordMutable((StgMutClosure *)rbh);
2996 failed_to_evac = rtsFalse; // mutable anyhow.
2998 belch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2999 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3005 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3006 // follow the pointer to the node which is being demanded
3007 (StgClosure *)bf->node =
3008 evacuate((StgClosure *)bf->node);
3009 // follow the link to the rest of the blocking queue
3010 (StgClosure *)bf->link =
3011 evacuate((StgClosure *)bf->link);
3012 if (failed_to_evac) {
3013 failed_to_evac = rtsFalse;
3014 recordMutable((StgMutClosure *)bf);
3017 belch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3018 bf, info_type((StgClosure *)bf),
3019 bf->node, info_type(bf->node)));
3027 break; // nothing to do in this case
3029 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
3031 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3032 (StgClosure *)fmbq->blocking_queue =
3033 evacuate((StgClosure *)fmbq->blocking_queue);
3034 if (failed_to_evac) {
3035 failed_to_evac = rtsFalse;
3036 recordMutable((StgMutClosure *)fmbq);
3039 belch("@@ scavenge: %p (%s) exciting, isn't it",
3040 p, info_type((StgClosure *)p)));
3046 barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p",
3050 if (failed_to_evac) {
3051 failed_to_evac = rtsFalse;
3052 mkMutCons((StgClosure *)q, &generations[evac_gen]);
3055 // mark the next bit to indicate "scavenged"
3056 mark(q+1, Bdescr(q));
3058 } // while (!mark_stack_empty())
3060 // start a new linear scan if the mark stack overflowed at some point
3061 if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
3062 IF_DEBUG(gc, belch("scavenge_mark_stack: starting linear scan"));
3063 mark_stack_overflowed = rtsFalse;
3064 oldgen_scan_bd = oldest_gen->steps[0].blocks;
3065 oldgen_scan = oldgen_scan_bd->start;
3068 if (oldgen_scan_bd) {
3069 // push a new thing on the mark stack
3071 // find a closure that is marked but not scavenged, and start
3073 while (oldgen_scan < oldgen_scan_bd->free
3074 && !is_marked(oldgen_scan,oldgen_scan_bd)) {
3078 if (oldgen_scan < oldgen_scan_bd->free) {
3080 // already scavenged?
3081 if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
3082 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3085 push_mark_stack(oldgen_scan);
3086 // ToDo: bump the linear scan by the actual size of the object
3087 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3091 oldgen_scan_bd = oldgen_scan_bd->link;
3092 if (oldgen_scan_bd != NULL) {
3093 oldgen_scan = oldgen_scan_bd->start;
3099 /* -----------------------------------------------------------------------------
3100 Scavenge one object.
3102 This is used for objects that are temporarily marked as mutable
3103 because they contain old-to-new generation pointers. Only certain
3104 objects can have this property.
3105 -------------------------------------------------------------------------- */
3108 scavenge_one(StgPtr p)
3110 const StgInfoTable *info;
3111 nat saved_evac_gen = evac_gen;
3114 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3115 info = get_itbl((StgClosure *)p);
3117 switch (info->type) {
3120 case FUN_1_0: // hardly worth specialising these guys
3140 case IND_OLDGEN_PERM:
3144 end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3145 for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
3146 (StgClosure *)*q = evacuate((StgClosure *)*q);
3152 case SE_CAF_BLACKHOLE:
3157 case THUNK_SELECTOR:
3159 StgSelector *s = (StgSelector *)p;
3160 s->selectee = evacuate(s->selectee);
3165 // nothing to follow
3170 // follow everything
3173 evac_gen = 0; // repeatedly mutable
3174 recordMutable((StgMutClosure *)p);
3175 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3176 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3177 (StgClosure *)*p = evacuate((StgClosure *)*p);
3179 evac_gen = saved_evac_gen;
3180 failed_to_evac = rtsFalse;
3184 case MUT_ARR_PTRS_FROZEN:
3186 // follow everything
3189 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3190 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3191 (StgClosure *)*p = evacuate((StgClosure *)*p);
3198 StgTSO *tso = (StgTSO *)p;
3200 evac_gen = 0; // repeatedly mutable
3202 recordMutable((StgMutClosure *)tso);
3203 evac_gen = saved_evac_gen;
3204 failed_to_evac = rtsFalse;
3210 StgAP_STACK *ap = (StgAP_STACK *)p;
3212 ap->fun = evacuate(ap->fun);
3213 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3214 p = (StgPtr)ap->payload + ap->size;
3220 p = scavenge_PAP((StgPAP *)p);
3224 // This might happen if for instance a MUT_CONS was pointing to a
3225 // THUNK which has since been updated. The IND_OLDGEN will
3226 // be on the mutable list anyway, so we don't need to do anything
3231 barf("scavenge_one: strange object %d", (int)(info->type));
3234 no_luck = failed_to_evac;
3235 failed_to_evac = rtsFalse;
3239 /* -----------------------------------------------------------------------------
3240 Scavenging mutable lists.
3242 We treat the mutable list of each generation > N (i.e. all the
3243 generations older than the one being collected) as roots. We also
3244 remove non-mutable objects from the mutable list at this point.
3245 -------------------------------------------------------------------------- */
3248 scavenge_mut_once_list(generation *gen)
3250 const StgInfoTable *info;
3251 StgMutClosure *p, *next, *new_list;
3253 p = gen->mut_once_list;
3254 new_list = END_MUT_LIST;
3258 failed_to_evac = rtsFalse;
3260 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
3262 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3265 if (info->type==RBH)
3266 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3268 switch(info->type) {
3271 case IND_OLDGEN_PERM:
3273 /* Try to pull the indirectee into this generation, so we can
3274 * remove the indirection from the mutable list.
3276 ((StgIndOldGen *)p)->indirectee =
3277 evacuate(((StgIndOldGen *)p)->indirectee);
3279 #if 0 && defined(DEBUG)
3280 if (RtsFlags.DebugFlags.gc)
3281 /* Debugging code to print out the size of the thing we just
3285 StgPtr start = gen->steps[0].scan;
3286 bdescr *start_bd = gen->steps[0].scan_bd;
3288 scavenge(&gen->steps[0]);
3289 if (start_bd != gen->steps[0].scan_bd) {
3290 size += (P_)BLOCK_ROUND_UP(start) - start;
3291 start_bd = start_bd->link;
3292 while (start_bd != gen->steps[0].scan_bd) {
3293 size += BLOCK_SIZE_W;
3294 start_bd = start_bd->link;
3296 size += gen->steps[0].scan -
3297 (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
3299 size = gen->steps[0].scan - start;
3301 belch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
3305 /* failed_to_evac might happen if we've got more than two
3306 * generations, we're collecting only generation 0, the
3307 * indirection resides in generation 2 and the indirectee is
3310 if (failed_to_evac) {
3311 failed_to_evac = rtsFalse;
3312 p->mut_link = new_list;
3315 /* the mut_link field of an IND_STATIC is overloaded as the
3316 * static link field too (it just so happens that we don't need
3317 * both at the same time), so we need to NULL it out when
3318 * removing this object from the mutable list because the static
3319 * link fields are all assumed to be NULL before doing a major
3327 /* MUT_CONS is a kind of MUT_VAR, except it that we try to remove
3328 * it from the mutable list if possible by promoting whatever it
3331 if (scavenge_one((StgPtr)((StgMutVar *)p)->var)) {
3332 /* didn't manage to promote everything, so put the
3333 * MUT_CONS back on the list.
3335 p->mut_link = new_list;
3341 // shouldn't have anything else on the mutables list
3342 barf("scavenge_mut_once_list: strange object? %d", (int)(info->type));
3346 gen->mut_once_list = new_list;
3351 scavenge_mutable_list(generation *gen)
3353 const StgInfoTable *info;
3354 StgMutClosure *p, *next;
3356 p = gen->saved_mut_list;
3360 failed_to_evac = rtsFalse;
3362 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
3364 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3367 if (info->type==RBH)
3368 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3370 switch(info->type) {
3373 // follow everything
3374 p->mut_link = gen->mut_list;
3379 end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3380 for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
3381 (StgClosure *)*q = evacuate((StgClosure *)*q);
3386 // Happens if a MUT_ARR_PTRS in the old generation is frozen
3387 case MUT_ARR_PTRS_FROZEN:
3392 end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3393 for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
3394 (StgClosure *)*q = evacuate((StgClosure *)*q);
3398 if (failed_to_evac) {
3399 failed_to_evac = rtsFalse;
3400 mkMutCons((StgClosure *)p, gen);
3406 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3407 p->mut_link = gen->mut_list;
3413 StgMVar *mvar = (StgMVar *)p;
3414 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
3415 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
3416 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
3417 p->mut_link = gen->mut_list;
3424 StgTSO *tso = (StgTSO *)p;
3428 /* Don't take this TSO off the mutable list - it might still
3429 * point to some younger objects (because we set evac_gen to 0
3432 tso->mut_link = gen->mut_list;
3433 gen->mut_list = (StgMutClosure *)tso;
3439 StgBlockingQueue *bh = (StgBlockingQueue *)p;
3440 (StgClosure *)bh->blocking_queue =
3441 evacuate((StgClosure *)bh->blocking_queue);
3442 p->mut_link = gen->mut_list;
3447 /* Happens if a BLACKHOLE_BQ in the old generation is updated:
3450 case IND_OLDGEN_PERM:
3451 /* Try to pull the indirectee into this generation, so we can
3452 * remove the indirection from the mutable list.
3455 ((StgIndOldGen *)p)->indirectee =
3456 evacuate(((StgIndOldGen *)p)->indirectee);
3459 if (failed_to_evac) {
3460 failed_to_evac = rtsFalse;
3461 p->mut_link = gen->mut_once_list;
3462 gen->mut_once_list = p;
3469 // HWL: check whether all of these are necessary
3471 case RBH: // cf. BLACKHOLE_BQ
3473 // nat size, ptrs, nonptrs, vhs;
3475 // StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3476 StgRBH *rbh = (StgRBH *)p;
3477 (StgClosure *)rbh->blocking_queue =
3478 evacuate((StgClosure *)rbh->blocking_queue);
3479 if (failed_to_evac) {
3480 failed_to_evac = rtsFalse;
3481 recordMutable((StgMutClosure *)rbh);
3483 // ToDo: use size of reverted closure here!
3484 p += BLACKHOLE_sizeW();
3490 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3491 // follow the pointer to the node which is being demanded
3492 (StgClosure *)bf->node =
3493 evacuate((StgClosure *)bf->node);
3494 // follow the link to the rest of the blocking queue
3495 (StgClosure *)bf->link =
3496 evacuate((StgClosure *)bf->link);
3497 if (failed_to_evac) {
3498 failed_to_evac = rtsFalse;
3499 recordMutable((StgMutClosure *)bf);
3501 p += sizeofW(StgBlockedFetch);
3507 barf("scavenge_mutable_list: REMOTE_REF %d", (int)(info->type));
3510 p += sizeofW(StgFetchMe);
3511 break; // nothing to do in this case
3513 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
3515 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3516 (StgClosure *)fmbq->blocking_queue =
3517 evacuate((StgClosure *)fmbq->blocking_queue);
3518 if (failed_to_evac) {
3519 failed_to_evac = rtsFalse;
3520 recordMutable((StgMutClosure *)fmbq);
3522 p += sizeofW(StgFetchMeBlockingQueue);
3528 // shouldn't have anything else on the mutables list
3529 barf("scavenge_mutable_list: strange object? %d", (int)(info->type));
3536 scavenge_static(void)
3538 StgClosure* p = static_objects;
3539 const StgInfoTable *info;
3541 /* Always evacuate straight to the oldest generation for static
3543 evac_gen = oldest_gen->no;
3545 /* keep going until we've scavenged all the objects on the linked
3547 while (p != END_OF_STATIC_LIST) {
3549 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3552 if (info->type==RBH)
3553 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3555 // make sure the info pointer is into text space
3557 /* Take this object *off* the static_objects list,
3558 * and put it on the scavenged_static_objects list.
3560 static_objects = STATIC_LINK(info,p);
3561 STATIC_LINK(info,p) = scavenged_static_objects;
3562 scavenged_static_objects = p;
3564 switch (info -> type) {
3568 StgInd *ind = (StgInd *)p;
3569 ind->indirectee = evacuate(ind->indirectee);
3571 /* might fail to evacuate it, in which case we have to pop it
3572 * back on the mutable list (and take it off the
3573 * scavenged_static list because the static link and mut link
3574 * pointers are one and the same).
3576 if (failed_to_evac) {
3577 failed_to_evac = rtsFalse;
3578 scavenged_static_objects = IND_STATIC_LINK(p);
3579 ((StgMutClosure *)ind)->mut_link = oldest_gen->mut_once_list;
3580 oldest_gen->mut_once_list = (StgMutClosure *)ind;
3586 scavenge_thunk_srt(info);
3590 scavenge_fun_srt(info);
3597 next = (P_)p->payload + info->layout.payload.ptrs;
3598 // evacuate the pointers
3599 for (q = (P_)p->payload; q < next; q++) {
3600 (StgClosure *)*q = evacuate((StgClosure *)*q);
3606 barf("scavenge_static: strange closure %d", (int)(info->type));
3609 ASSERT(failed_to_evac == rtsFalse);
3611 /* get the next static object from the list. Remember, there might
3612 * be more stuff on this list now that we've done some evacuating!
3613 * (static_objects is a global)
3619 /* -----------------------------------------------------------------------------
3620 scavenge a chunk of memory described by a bitmap
3621 -------------------------------------------------------------------------- */
3624 scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
3630 bitmap = large_bitmap->bitmap[b];
3631 for (i = 0; i < size; ) {
3632 if ((bitmap & 1) == 0) {
3633 (StgClosure *)*p = evacuate((StgClosure *)*p);
3637 if (i % BITS_IN(W_) == 0) {
3639 bitmap = large_bitmap->bitmap[b];
3641 bitmap = bitmap >> 1;
3646 static inline StgPtr
3647 scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap)
3650 if ((bitmap & 1) == 0) {
3651 (StgClosure *)*p = evacuate((StgClosure *)*p);
3654 bitmap = bitmap >> 1;
3660 /* -----------------------------------------------------------------------------
3661 scavenge_stack walks over a section of stack and evacuates all the
3662 objects pointed to by it. We can use the same code for walking
3663 AP_STACK_UPDs, since these are just sections of copied stack.
3664 -------------------------------------------------------------------------- */
3668 scavenge_stack(StgPtr p, StgPtr stack_end)
3670 const StgRetInfoTable* info;
3674 //IF_DEBUG(sanity, belch(" scavenging stack between %p and %p", p, stack_end));
3677 * Each time around this loop, we are looking at a chunk of stack
3678 * that starts with an activation record.
3681 while (p < stack_end) {
3682 info = get_ret_itbl((StgClosure *)p);
3684 switch (info->i.type) {
3687 ((StgUpdateFrame *)p)->updatee
3688 = evacuate(((StgUpdateFrame *)p)->updatee);
3689 p += sizeofW(StgUpdateFrame);
3692 // small bitmap (< 32 entries, or 64 on a 64-bit machine)
3697 bitmap = BITMAP_BITS(info->i.layout.bitmap);
3698 size = BITMAP_SIZE(info->i.layout.bitmap);
3699 // NOTE: the payload starts immediately after the info-ptr, we
3700 // don't have an StgHeader in the same sense as a heap closure.
3702 p = scavenge_small_bitmap(p, size, bitmap);
3705 scavenge_srt((StgClosure **)info->srt, info->i.srt_bitmap);
3713 (StgClosure *)*p = evacuate((StgClosure *)*p);
3716 size = BCO_BITMAP_SIZE(bco);
3717 scavenge_large_bitmap(p, BCO_BITMAP(bco), size);
3722 // large bitmap (> 32 entries, or > 64 on a 64-bit machine)
3728 size = info->i.layout.large_bitmap->size;
3730 scavenge_large_bitmap(p, info->i.layout.large_bitmap, size);
3732 // and don't forget to follow the SRT
3736 // Dynamic bitmap: the mask is stored on the stack, and
3737 // there are a number of non-pointers followed by a number
3738 // of pointers above the bitmapped area. (see StgMacros.h,
3743 dyn = ((StgRetDyn *)p)->liveness;
3745 // traverse the bitmap first
3746 bitmap = GET_LIVENESS(dyn);
3747 p = (P_)&((StgRetDyn *)p)->payload[0];
3748 size = RET_DYN_BITMAP_SIZE;
3749 p = scavenge_small_bitmap(p, size, bitmap);
3751 // skip over the non-ptr words
3752 p += GET_NONPTRS(dyn) + RET_DYN_NONPTR_REGS_SIZE;
3754 // follow the ptr words
3755 for (size = GET_PTRS(dyn); size > 0; size--) {
3756 (StgClosure *)*p = evacuate((StgClosure *)*p);
3764 StgRetFun *ret_fun = (StgRetFun *)p;
3765 StgFunInfoTable *fun_info;
3767 ret_fun->fun = evacuate(ret_fun->fun);
3768 fun_info = get_fun_itbl(ret_fun->fun);
3769 p = scavenge_arg_block(fun_info, ret_fun->payload);
3774 barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->i.type));
3779 /*-----------------------------------------------------------------------------
3780 scavenge the large object list.
3782 evac_gen set by caller; similar games played with evac_gen as with
3783 scavenge() - see comment at the top of scavenge(). Most large
3784 objects are (repeatedly) mutable, so most of the time evac_gen will
3786 --------------------------------------------------------------------------- */
3789 scavenge_large(step *stp)
3794 bd = stp->new_large_objects;
3796 for (; bd != NULL; bd = stp->new_large_objects) {
3798 /* take this object *off* the large objects list and put it on
3799 * the scavenged large objects list. This is so that we can
3800 * treat new_large_objects as a stack and push new objects on
3801 * the front when evacuating.
3803 stp->new_large_objects = bd->link;
3804 dbl_link_onto(bd, &stp->scavenged_large_objects);
3806 // update the block count in this step.
3807 stp->n_scavenged_large_blocks += bd->blocks;
3810 if (scavenge_one(p)) {
3811 mkMutCons((StgClosure *)p, stp->gen);
3816 /* -----------------------------------------------------------------------------
3817 Initialising the static object & mutable lists
3818 -------------------------------------------------------------------------- */
3821 zero_static_object_list(StgClosure* first_static)
3825 const StgInfoTable *info;
3827 for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
3829 link = STATIC_LINK(info, p);
3830 STATIC_LINK(info,p) = NULL;
3834 /* This function is only needed because we share the mutable link
3835 * field with the static link field in an IND_STATIC, so we have to
3836 * zero the mut_link field before doing a major GC, which needs the
3837 * static link field.
3839 * It doesn't do any harm to zero all the mutable link fields on the
3844 zero_mutable_list( StgMutClosure *first )
3846 StgMutClosure *next, *c;
3848 for (c = first; c != END_MUT_LIST; c = next) {
3854 /* -----------------------------------------------------------------------------
3856 -------------------------------------------------------------------------- */
3863 for (c = (StgIndStatic *)caf_list; c != NULL;
3864 c = (StgIndStatic *)c->static_link)
3866 c->header.info = c->saved_info;
3867 c->saved_info = NULL;
3868 // could, but not necessary: c->static_link = NULL;
3874 markCAFs( evac_fn evac )
3878 for (c = (StgIndStatic *)caf_list; c != NULL;
3879 c = (StgIndStatic *)c->static_link)
3881 evac(&c->indirectee);
3885 /* -----------------------------------------------------------------------------
3886 Sanity code for CAF garbage collection.
3888 With DEBUG turned on, we manage a CAF list in addition to the SRT
3889 mechanism. After GC, we run down the CAF list and blackhole any
3890 CAFs which have been garbage collected. This means we get an error
3891 whenever the program tries to enter a garbage collected CAF.
3893 Any garbage collected CAFs are taken off the CAF list at the same
3895 -------------------------------------------------------------------------- */
3897 #if 0 && defined(DEBUG)
3904 const StgInfoTable *info;
3915 ASSERT(info->type == IND_STATIC);
3917 if (STATIC_LINK(info,p) == NULL) {
3918 IF_DEBUG(gccafs, belch("CAF gc'd at 0x%04lx", (long)p));
3920 SET_INFO(p,&stg_BLACKHOLE_info);
3921 p = STATIC_LINK2(info,p);
3925 pp = &STATIC_LINK2(info,p);
3932 // belch("%d CAFs live", i);
3937 /* -----------------------------------------------------------------------------
3940 Whenever a thread returns to the scheduler after possibly doing
3941 some work, we have to run down the stack and black-hole all the
3942 closures referred to by update frames.
3943 -------------------------------------------------------------------------- */
3946 threadLazyBlackHole(StgTSO *tso)
3949 StgRetInfoTable *info;
3950 StgBlockingQueue *bh;
3953 stack_end = &tso->stack[tso->stack_size];
3955 frame = (StgClosure *)tso->sp;
3958 info = get_ret_itbl(frame);
3960 switch (info->i.type) {
3963 bh = (StgBlockingQueue *)((StgUpdateFrame *)frame)->updatee;
3965 /* if the thunk is already blackholed, it means we've also
3966 * already blackholed the rest of the thunks on this stack,
3967 * so we can stop early.
3969 * The blackhole made for a CAF is a CAF_BLACKHOLE, so they
3970 * don't interfere with this optimisation.
3972 if (bh->header.info == &stg_BLACKHOLE_info) {
3976 if (bh->header.info != &stg_BLACKHOLE_BQ_info &&
3977 bh->header.info != &stg_CAF_BLACKHOLE_info) {
3978 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
3979 belch("Unexpected lazy BHing required at 0x%04x",(int)bh);
3983 // We pretend that bh is now dead.
3984 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
3986 SET_INFO(bh,&stg_BLACKHOLE_info);
3989 // We pretend that bh has just been created.
3990 LDV_recordCreate(bh);
3994 frame = (StgClosure *) ((StgUpdateFrame *)frame + 1);
4000 // normal stack frames; do nothing except advance the pointer
4002 (StgPtr)frame += stack_frame_sizeW(frame);
4008 /* -----------------------------------------------------------------------------
4011 * Code largely pinched from old RTS, then hacked to bits. We also do
4012 * lazy black holing here.
4014 * -------------------------------------------------------------------------- */
4016 struct stack_gap { StgWord gap_size; struct stack_gap *next_gap; };
4019 threadSqueezeStack(StgTSO *tso)
4022 rtsBool prev_was_update_frame;
4023 StgClosure *updatee = NULL;
4025 StgRetInfoTable *info;
4026 StgWord current_gap_size;
4027 struct stack_gap *gap;
4030 // Traverse the stack upwards, replacing adjacent update frames
4031 // with a single update frame and a "stack gap". A stack gap
4032 // contains two values: the size of the gap, and the distance
4033 // to the next gap (or the stack top).
4035 bottom = &(tso->stack[tso->stack_size]);
4039 ASSERT(frame < bottom);
4041 prev_was_update_frame = rtsFalse;
4042 current_gap_size = 0;
4043 gap = (struct stack_gap *) (tso->sp - sizeofW(StgUpdateFrame));
4045 while (frame < bottom) {
4047 info = get_ret_itbl((StgClosure *)frame);
4048 switch (info->i.type) {
4052 StgUpdateFrame *upd = (StgUpdateFrame *)frame;
4054 if (upd->updatee->header.info == &stg_BLACKHOLE_info) {
4056 // found a BLACKHOLE'd update frame; we've been here
4057 // before, in a previous GC, so just break out.
4059 // Mark the end of the gap, if we're in one.
4060 if (current_gap_size != 0) {
4061 gap = (struct stack_gap *)(frame-sizeofW(StgUpdateFrame));
4064 frame += sizeofW(StgUpdateFrame);
4065 goto done_traversing;
4068 if (prev_was_update_frame) {
4070 TICK_UPD_SQUEEZED();
4071 /* wasn't there something about update squeezing and ticky to be
4072 * sorted out? oh yes: we aren't counting each enter properly
4073 * in this case. See the log somewhere. KSW 1999-04-21
4075 * Check two things: that the two update frames don't point to
4076 * the same object, and that the updatee_bypass isn't already an
4077 * indirection. Both of these cases only happen when we're in a
4078 * block hole-style loop (and there are multiple update frames
4079 * on the stack pointing to the same closure), but they can both
4080 * screw us up if we don't check.
4082 if (upd->updatee != updatee && !closure_IND(upd->updatee)) {
4083 // this wakes the threads up
4084 UPD_IND_NOLOCK(upd->updatee, updatee);
4087 // now mark this update frame as a stack gap. The gap
4088 // marker resides in the bottom-most update frame of
4089 // the series of adjacent frames, and covers all the
4090 // frames in this series.
4091 current_gap_size += sizeofW(StgUpdateFrame);
4092 ((struct stack_gap *)frame)->gap_size = current_gap_size;
4093 ((struct stack_gap *)frame)->next_gap = gap;
4095 frame += sizeofW(StgUpdateFrame);
4099 // single update frame, or the topmost update frame in a series
4101 StgBlockingQueue *bh = (StgBlockingQueue *)upd->updatee;
4103 // Do lazy black-holing
4104 if (bh->header.info != &stg_BLACKHOLE_info &&
4105 bh->header.info != &stg_BLACKHOLE_BQ_info &&
4106 bh->header.info != &stg_CAF_BLACKHOLE_info) {
4107 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4108 belch("Unexpected lazy BHing required at 0x%04x",(int)bh);
4111 /* zero out the slop so that the sanity checker can tell
4112 * where the next closure is.
4115 StgInfoTable *bh_info = get_itbl(bh);
4116 nat np = bh_info->layout.payload.ptrs,
4117 nw = bh_info->layout.payload.nptrs, i;
4118 /* don't zero out slop for a THUNK_SELECTOR,
4119 * because its layout info is used for a
4120 * different purpose, and it's exactly the
4121 * same size as a BLACKHOLE in any case.
4123 if (bh_info->type != THUNK_SELECTOR) {
4124 for (i = np; i < np + nw; i++) {
4125 ((StgClosure *)bh)->payload[i] = 0;
4131 // We pretend that bh is now dead.
4132 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4134 // Todo: maybe use SET_HDR() and remove LDV_recordCreate()?
4135 SET_INFO(bh,&stg_BLACKHOLE_info);
4137 // We pretend that bh has just been created.
4138 LDV_recordCreate(bh);
4142 prev_was_update_frame = rtsTrue;
4143 updatee = upd->updatee;
4144 frame += sizeofW(StgUpdateFrame);
4150 prev_was_update_frame = rtsFalse;
4152 // we're not in a gap... check whether this is the end of a gap
4153 // (an update frame can't be the end of a gap).
4154 if (current_gap_size != 0) {
4155 gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
4157 current_gap_size = 0;
4159 frame += stack_frame_sizeW((StgClosure *)frame);
4166 // Now we have a stack with gaps in it, and we have to walk down
4167 // shoving the stack up to fill in the gaps. A diagram might
4171 // | ********* | <- sp
4175 // | stack_gap | <- gap | chunk_size
4177 // | ......... | <- gap_end v
4183 // 'sp' points the the current top-of-stack
4184 // 'gap' points to the stack_gap structure inside the gap
4185 // ***** indicates real stack data
4186 // ..... indicates gap
4187 // <empty> indicates unused
4191 void *gap_start, *next_gap_start, *gap_end;
4194 next_gap_start = (void *)gap + sizeof(StgUpdateFrame);
4195 sp = next_gap_start;
4197 while ((StgPtr)gap > tso->sp) {
4199 // we're working in *bytes* now...
4200 gap_start = next_gap_start;
4201 gap_end = gap_start - gap->gap_size * sizeof(W_);
4203 gap = gap->next_gap;
4204 next_gap_start = (void *)gap + sizeof(StgUpdateFrame);
4206 chunk_size = gap_end - next_gap_start;
4208 memmove(sp, next_gap_start, chunk_size);
4211 tso->sp = (StgPtr)sp;
4215 /* -----------------------------------------------------------------------------
4218 * We have to prepare for GC - this means doing lazy black holing
4219 * here. We also take the opportunity to do stack squeezing if it's
4221 * -------------------------------------------------------------------------- */
4223 threadPaused(StgTSO *tso)
4225 if ( RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue )
4226 threadSqueezeStack(tso); // does black holing too
4228 threadLazyBlackHole(tso);
4231 /* -----------------------------------------------------------------------------
4233 * -------------------------------------------------------------------------- */
4237 printMutOnceList(generation *gen)
4239 StgMutClosure *p, *next;
4241 p = gen->mut_once_list;
4244 fprintf(stderr, "@@ Mut once list %p: ", gen->mut_once_list);
4245 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
4246 fprintf(stderr, "%p (%s), ",
4247 p, info_type((StgClosure *)p));
4249 fputc('\n', stderr);
4253 printMutableList(generation *gen)
4255 StgMutClosure *p, *next;
4260 fprintf(stderr, "@@ Mutable list %p: ", gen->mut_list);
4261 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
4262 fprintf(stderr, "%p (%s), ",
4263 p, info_type((StgClosure *)p));
4265 fputc('\n', stderr);
4268 static inline rtsBool
4269 maybeLarge(StgClosure *closure)
4271 StgInfoTable *info = get_itbl(closure);
4273 /* closure types that may be found on the new_large_objects list;
4274 see scavenge_large */
4275 return (info->type == MUT_ARR_PTRS ||
4276 info->type == MUT_ARR_PTRS_FROZEN ||
4277 info->type == TSO ||
4278 info->type == ARR_WORDS);