1 /* -----------------------------------------------------------------------------
2 * $Id: GC.c,v 1.150 2003/03/24 15:33:25 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 );
142 static StgClosure * evacuate ( StgClosure *q );
143 static void zero_static_object_list ( StgClosure* first_static );
144 static void zero_mutable_list ( StgMutClosure *first );
146 static rtsBool traverse_weak_ptr_list ( void );
147 static void mark_weak_ptr_list ( StgWeak **list );
149 static StgClosure * eval_thunk_selector ( nat field, StgSelector * p );
152 static void scavenge ( step * );
153 static void scavenge_mark_stack ( void );
154 static void scavenge_stack ( StgPtr p, StgPtr stack_end );
155 static rtsBool scavenge_one ( StgPtr p );
156 static void scavenge_large ( step * );
157 static void scavenge_static ( void );
158 static void scavenge_mutable_list ( generation *g );
159 static void scavenge_mut_once_list ( generation *g );
161 static void scavenge_large_bitmap ( StgPtr p,
162 StgLargeBitmap *large_bitmap,
165 #if 0 && defined(DEBUG)
166 static void gcCAFs ( void );
169 /* -----------------------------------------------------------------------------
170 inline functions etc. for dealing with the mark bitmap & stack.
171 -------------------------------------------------------------------------- */
173 #define MARK_STACK_BLOCKS 4
175 static bdescr *mark_stack_bdescr;
176 static StgPtr *mark_stack;
177 static StgPtr *mark_sp;
178 static StgPtr *mark_splim;
180 // Flag and pointers used for falling back to a linear scan when the
181 // mark stack overflows.
182 static rtsBool mark_stack_overflowed;
183 static bdescr *oldgen_scan_bd;
184 static StgPtr oldgen_scan;
186 static inline rtsBool
187 mark_stack_empty(void)
189 return mark_sp == mark_stack;
192 static inline rtsBool
193 mark_stack_full(void)
195 return mark_sp >= mark_splim;
199 reset_mark_stack(void)
201 mark_sp = mark_stack;
205 push_mark_stack(StgPtr p)
216 /* -----------------------------------------------------------------------------
217 Allocate a new to-space block in the given step.
218 -------------------------------------------------------------------------- */
221 gc_alloc_block(step *stp)
223 bdescr *bd = allocBlock();
224 bd->gen_no = stp->gen_no;
228 // blocks in to-space in generations up to and including N
229 // get the BF_EVACUATED flag.
230 if (stp->gen_no <= N) {
231 bd->flags = BF_EVACUATED;
236 // Start a new to-space block, chain it on after the previous one.
237 if (stp->hp_bd == NULL) {
240 stp->hp_bd->free = stp->hp;
241 stp->hp_bd->link = bd;
246 stp->hpLim = stp->hp + BLOCK_SIZE_W;
254 /* -----------------------------------------------------------------------------
257 Rough outline of the algorithm: for garbage collecting generation N
258 (and all younger generations):
260 - follow all pointers in the root set. the root set includes all
261 mutable objects in all generations (mutable_list and mut_once_list).
263 - for each pointer, evacuate the object it points to into either
265 + to-space of the step given by step->to, which is the next
266 highest step in this generation or the first step in the next
267 generation if this is the last step.
269 + to-space of generations[evac_gen]->steps[0], if evac_gen != 0.
270 When we evacuate an object we attempt to evacuate
271 everything it points to into the same generation - this is
272 achieved by setting evac_gen to the desired generation. If
273 we can't do this, then an entry in the mut_once list has to
274 be made for the cross-generation pointer.
276 + if the object is already in a generation > N, then leave
279 - repeatedly scavenge to-space from each step in each generation
280 being collected until no more objects can be evacuated.
282 - free from-space in each step, and set from-space = to-space.
284 Locks held: sched_mutex
286 -------------------------------------------------------------------------- */
289 GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc )
293 lnat live, allocated, collected = 0, copied = 0;
294 lnat oldgen_saved_blocks = 0;
298 CostCentreStack *prev_CCS;
301 #if defined(DEBUG) && defined(GRAN)
302 IF_DEBUG(gc, belch("@@ Starting garbage collection at %ld (%lx)\n",
306 #ifndef mingw32_TARGET_OS
311 // tell the stats department that we've started a GC
314 // Init stats and print par specific (timing) info
315 PAR_TICKY_PAR_START();
317 // attribute any costs to CCS_GC
323 /* Approximate how much we allocated.
324 * Todo: only when generating stats?
326 allocated = calcAllocated();
328 /* Figure out which generation to collect
330 if (force_major_gc) {
331 N = RtsFlags.GcFlags.generations - 1;
335 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
336 if (generations[g].steps[0].n_blocks +
337 generations[g].steps[0].n_large_blocks
338 >= generations[g].max_blocks) {
342 major_gc = (N == RtsFlags.GcFlags.generations-1);
345 #ifdef RTS_GTK_FRONTPANEL
346 if (RtsFlags.GcFlags.frontpanel) {
347 updateFrontPanelBeforeGC(N);
351 // check stack sanity *before* GC (ToDo: check all threads)
353 // ToDo!: check sanity IF_DEBUG(sanity, checkTSOsSanity());
355 IF_DEBUG(sanity, checkFreeListSanity());
357 /* Initialise the static object lists
359 static_objects = END_OF_STATIC_LIST;
360 scavenged_static_objects = END_OF_STATIC_LIST;
362 /* zero the mutable list for the oldest generation (see comment by
363 * zero_mutable_list below).
366 zero_mutable_list(generations[RtsFlags.GcFlags.generations-1].mut_once_list);
369 /* Save the old to-space if we're doing a two-space collection
371 if (RtsFlags.GcFlags.generations == 1) {
372 old_to_blocks = g0s0->to_blocks;
373 g0s0->to_blocks = NULL;
376 /* Keep a count of how many new blocks we allocated during this GC
377 * (used for resizing the allocation area, later).
381 // Initialise to-space in all the generations/steps that we're
384 for (g = 0; g <= N; g++) {
385 generations[g].mut_once_list = END_MUT_LIST;
386 generations[g].mut_list = END_MUT_LIST;
388 for (s = 0; s < generations[g].n_steps; s++) {
390 // generation 0, step 0 doesn't need to-space
391 if (g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1) {
395 stp = &generations[g].steps[s];
396 ASSERT(stp->gen_no == g);
398 // start a new to-space for this step.
401 stp->to_blocks = NULL;
403 // allocate the first to-space block; extra blocks will be
404 // chained on as necessary.
405 bd = gc_alloc_block(stp);
407 stp->scan = bd->start;
410 // initialise the large object queues.
411 stp->new_large_objects = NULL;
412 stp->scavenged_large_objects = NULL;
413 stp->n_scavenged_large_blocks = 0;
415 // mark the large objects as not evacuated yet
416 for (bd = stp->large_objects; bd; bd = bd->link) {
417 bd->flags = BF_LARGE;
420 // for a compacted step, we need to allocate the bitmap
421 if (stp->is_compacted) {
422 nat bitmap_size; // in bytes
423 bdescr *bitmap_bdescr;
426 bitmap_size = stp->n_blocks * BLOCK_SIZE / (sizeof(W_)*BITS_PER_BYTE);
428 if (bitmap_size > 0) {
429 bitmap_bdescr = allocGroup((nat)BLOCK_ROUND_UP(bitmap_size)
431 stp->bitmap = bitmap_bdescr;
432 bitmap = bitmap_bdescr->start;
434 IF_DEBUG(gc, belch("bitmap_size: %d, bitmap: %p",
435 bitmap_size, bitmap););
437 // don't forget to fill it with zeros!
438 memset(bitmap, 0, bitmap_size);
440 // for each block in this step, point to its bitmap from the
442 for (bd=stp->blocks; bd != NULL; bd = bd->link) {
443 bd->u.bitmap = bitmap;
444 bitmap += BLOCK_SIZE_W / (sizeof(W_)*BITS_PER_BYTE);
451 /* make sure the older generations have at least one block to
452 * allocate into (this makes things easier for copy(), see below).
454 for (g = N+1; g < RtsFlags.GcFlags.generations; g++) {
455 for (s = 0; s < generations[g].n_steps; s++) {
456 stp = &generations[g].steps[s];
457 if (stp->hp_bd == NULL) {
458 ASSERT(stp->blocks == NULL);
459 bd = gc_alloc_block(stp);
463 /* Set the scan pointer for older generations: remember we
464 * still have to scavenge objects that have been promoted. */
466 stp->scan_bd = stp->hp_bd;
467 stp->to_blocks = NULL;
468 stp->n_to_blocks = 0;
469 stp->new_large_objects = NULL;
470 stp->scavenged_large_objects = NULL;
471 stp->n_scavenged_large_blocks = 0;
475 /* Allocate a mark stack if we're doing a major collection.
478 mark_stack_bdescr = allocGroup(MARK_STACK_BLOCKS);
479 mark_stack = (StgPtr *)mark_stack_bdescr->start;
480 mark_sp = mark_stack;
481 mark_splim = mark_stack + (MARK_STACK_BLOCKS * BLOCK_SIZE_W);
483 mark_stack_bdescr = NULL;
486 /* -----------------------------------------------------------------------
487 * follow all the roots that we know about:
488 * - mutable lists from each generation > N
489 * we want to *scavenge* these roots, not evacuate them: they're not
490 * going to move in this GC.
491 * Also: do them in reverse generation order. This is because we
492 * often want to promote objects that are pointed to by older
493 * generations early, so we don't have to repeatedly copy them.
494 * Doing the generations in reverse order ensures that we don't end
495 * up in the situation where we want to evac an object to gen 3 and
496 * it has already been evaced to gen 2.
500 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
501 generations[g].saved_mut_list = generations[g].mut_list;
502 generations[g].mut_list = END_MUT_LIST;
505 // Do the mut-once lists first
506 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
507 IF_PAR_DEBUG(verbose,
508 printMutOnceList(&generations[g]));
509 scavenge_mut_once_list(&generations[g]);
511 for (st = generations[g].n_steps-1; st >= 0; st--) {
512 scavenge(&generations[g].steps[st]);
516 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
517 IF_PAR_DEBUG(verbose,
518 printMutableList(&generations[g]));
519 scavenge_mutable_list(&generations[g]);
521 for (st = generations[g].n_steps-1; st >= 0; st--) {
522 scavenge(&generations[g].steps[st]);
527 /* follow roots from the CAF list (used by GHCi)
532 /* follow all the roots that the application knows about.
535 get_roots(mark_root);
538 /* And don't forget to mark the TSO if we got here direct from
540 /* Not needed in a seq version?
542 CurrentTSO = (StgTSO *)MarkRoot((StgClosure *)CurrentTSO);
546 // Mark the entries in the GALA table of the parallel system
547 markLocalGAs(major_gc);
548 // Mark all entries on the list of pending fetches
549 markPendingFetches(major_gc);
552 /* Mark the weak pointer list, and prepare to detect dead weak
555 mark_weak_ptr_list(&weak_ptr_list);
556 old_weak_ptr_list = weak_ptr_list;
557 weak_ptr_list = NULL;
558 weak_stage = WeakPtrs;
560 /* The all_threads list is like the weak_ptr_list.
561 * See traverse_weak_ptr_list() for the details.
563 old_all_threads = all_threads;
564 all_threads = END_TSO_QUEUE;
565 resurrected_threads = END_TSO_QUEUE;
567 /* Mark the stable pointer table.
569 markStablePtrTable(mark_root);
573 /* ToDo: To fix the caf leak, we need to make the commented out
574 * parts of this code do something sensible - as described in
577 extern void markHugsObjects(void);
582 /* -------------------------------------------------------------------------
583 * Repeatedly scavenge all the areas we know about until there's no
584 * more scavenging to be done.
591 // scavenge static objects
592 if (major_gc && static_objects != END_OF_STATIC_LIST) {
593 IF_DEBUG(sanity, checkStaticObjects(static_objects));
597 /* When scavenging the older generations: Objects may have been
598 * evacuated from generations <= N into older generations, and we
599 * need to scavenge these objects. We're going to try to ensure that
600 * any evacuations that occur move the objects into at least the
601 * same generation as the object being scavenged, otherwise we
602 * have to create new entries on the mutable list for the older
606 // scavenge each step in generations 0..maxgen
612 // scavenge objects in compacted generation
613 if (mark_stack_overflowed || oldgen_scan_bd != NULL ||
614 (mark_stack_bdescr != NULL && !mark_stack_empty())) {
615 scavenge_mark_stack();
619 for (gen = RtsFlags.GcFlags.generations; --gen >= 0; ) {
620 for (st = generations[gen].n_steps; --st >= 0; ) {
621 if (gen == 0 && st == 0 && RtsFlags.GcFlags.generations > 1) {
624 stp = &generations[gen].steps[st];
626 if (stp->hp_bd != stp->scan_bd || stp->scan < stp->hp) {
631 if (stp->new_large_objects != NULL) {
640 if (flag) { goto loop; }
642 // must be last... invariant is that everything is fully
643 // scavenged at this point.
644 if (traverse_weak_ptr_list()) { // returns rtsTrue if evaced something
649 /* Update the pointers from the "main thread" list - these are
650 * treated as weak pointers because we want to allow a main thread
651 * to get a BlockedOnDeadMVar exception in the same way as any other
652 * thread. Note that the threads should all have been retained by
653 * GC by virtue of being on the all_threads list, we're just
654 * updating pointers here.
659 for (m = main_threads; m != NULL; m = m->link) {
660 tso = (StgTSO *) isAlive((StgClosure *)m->tso);
662 barf("main thread has been GC'd");
669 // Reconstruct the Global Address tables used in GUM
670 rebuildGAtables(major_gc);
671 IF_DEBUG(sanity, checkLAGAtable(rtsTrue/*check closures, too*/));
674 // Now see which stable names are still alive.
677 // Tidy the end of the to-space chains
678 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
679 for (s = 0; s < generations[g].n_steps; s++) {
680 stp = &generations[g].steps[s];
681 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
682 ASSERT(Bdescr(stp->hp) == stp->hp_bd);
683 stp->hp_bd->free = stp->hp;
689 // We call processHeapClosureForDead() on every closure destroyed during
690 // the current garbage collection, so we invoke LdvCensusForDead().
691 if (RtsFlags.ProfFlags.doHeapProfile == HEAP_BY_LDV
692 || RtsFlags.ProfFlags.bioSelector != NULL)
696 // NO MORE EVACUATION AFTER THIS POINT!
697 // Finally: compaction of the oldest generation.
698 if (major_gc && oldest_gen->steps[0].is_compacted) {
699 // save number of blocks for stats
700 oldgen_saved_blocks = oldest_gen->steps[0].n_blocks;
704 IF_DEBUG(sanity, checkGlobalTSOList(rtsFalse));
706 /* run through all the generations/steps and tidy up
708 copied = new_blocks * BLOCK_SIZE_W;
709 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
712 generations[g].collections++; // for stats
715 for (s = 0; s < generations[g].n_steps; s++) {
717 stp = &generations[g].steps[s];
719 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
720 // stats information: how much we copied
722 copied -= stp->hp_bd->start + BLOCK_SIZE_W -
727 // for generations we collected...
730 // rough calculation of garbage collected, for stats output
731 if (stp->is_compacted) {
732 collected += (oldgen_saved_blocks - stp->n_blocks) * BLOCK_SIZE_W;
734 collected += stp->n_blocks * BLOCK_SIZE_W;
737 /* free old memory and shift to-space into from-space for all
738 * the collected steps (except the allocation area). These
739 * freed blocks will probaby be quickly recycled.
741 if (!(g == 0 && s == 0)) {
742 if (stp->is_compacted) {
743 // for a compacted step, just shift the new to-space
744 // onto the front of the now-compacted existing blocks.
745 for (bd = stp->to_blocks; bd != NULL; bd = bd->link) {
746 bd->flags &= ~BF_EVACUATED; // now from-space
748 // tack the new blocks on the end of the existing blocks
749 if (stp->blocks == NULL) {
750 stp->blocks = stp->to_blocks;
752 for (bd = stp->blocks; bd != NULL; bd = next) {
755 bd->link = stp->to_blocks;
759 // add the new blocks to the block tally
760 stp->n_blocks += stp->n_to_blocks;
762 freeChain(stp->blocks);
763 stp->blocks = stp->to_blocks;
764 stp->n_blocks = stp->n_to_blocks;
765 for (bd = stp->blocks; bd != NULL; bd = bd->link) {
766 bd->flags &= ~BF_EVACUATED; // now from-space
769 stp->to_blocks = NULL;
770 stp->n_to_blocks = 0;
773 /* LARGE OBJECTS. The current live large objects are chained on
774 * scavenged_large, having been moved during garbage
775 * collection from large_objects. Any objects left on
776 * large_objects list are therefore dead, so we free them here.
778 for (bd = stp->large_objects; bd != NULL; bd = next) {
784 // update the count of blocks used by large objects
785 for (bd = stp->scavenged_large_objects; bd != NULL; bd = bd->link) {
786 bd->flags &= ~BF_EVACUATED;
788 stp->large_objects = stp->scavenged_large_objects;
789 stp->n_large_blocks = stp->n_scavenged_large_blocks;
792 // for older generations...
794 /* For older generations, we need to append the
795 * scavenged_large_object list (i.e. large objects that have been
796 * promoted during this GC) to the large_object list for that step.
798 for (bd = stp->scavenged_large_objects; bd; bd = next) {
800 bd->flags &= ~BF_EVACUATED;
801 dbl_link_onto(bd, &stp->large_objects);
804 // add the new blocks we promoted during this GC
805 stp->n_blocks += stp->n_to_blocks;
806 stp->n_to_blocks = 0;
807 stp->n_large_blocks += stp->n_scavenged_large_blocks;
812 /* Reset the sizes of the older generations when we do a major
815 * CURRENT STRATEGY: make all generations except zero the same size.
816 * We have to stay within the maximum heap size, and leave a certain
817 * percentage of the maximum heap size available to allocate into.
819 if (major_gc && RtsFlags.GcFlags.generations > 1) {
820 nat live, size, min_alloc;
821 nat max = RtsFlags.GcFlags.maxHeapSize;
822 nat gens = RtsFlags.GcFlags.generations;
824 // live in the oldest generations
825 live = oldest_gen->steps[0].n_blocks +
826 oldest_gen->steps[0].n_large_blocks;
828 // default max size for all generations except zero
829 size = stg_max(live * RtsFlags.GcFlags.oldGenFactor,
830 RtsFlags.GcFlags.minOldGenSize);
832 // minimum size for generation zero
833 min_alloc = stg_max((RtsFlags.GcFlags.pcFreeHeap * max) / 200,
834 RtsFlags.GcFlags.minAllocAreaSize);
836 // Auto-enable compaction when the residency reaches a
837 // certain percentage of the maximum heap size (default: 30%).
838 if (RtsFlags.GcFlags.generations > 1 &&
839 (RtsFlags.GcFlags.compact ||
841 oldest_gen->steps[0].n_blocks >
842 (RtsFlags.GcFlags.compactThreshold * max) / 100))) {
843 oldest_gen->steps[0].is_compacted = 1;
844 // fprintf(stderr,"compaction: on\n", live);
846 oldest_gen->steps[0].is_compacted = 0;
847 // fprintf(stderr,"compaction: off\n", live);
850 // if we're going to go over the maximum heap size, reduce the
851 // size of the generations accordingly. The calculation is
852 // different if compaction is turned on, because we don't need
853 // to double the space required to collect the old generation.
856 // this test is necessary to ensure that the calculations
857 // below don't have any negative results - we're working
858 // with unsigned values here.
859 if (max < min_alloc) {
863 if (oldest_gen->steps[0].is_compacted) {
864 if ( (size + (size - 1) * (gens - 2) * 2) + min_alloc > max ) {
865 size = (max - min_alloc) / ((gens - 1) * 2 - 1);
868 if ( (size * (gens - 1) * 2) + min_alloc > max ) {
869 size = (max - min_alloc) / ((gens - 1) * 2);
879 fprintf(stderr,"live: %d, min_alloc: %d, size : %d, max = %d\n", live,
880 min_alloc, size, max);
883 for (g = 0; g < gens; g++) {
884 generations[g].max_blocks = size;
888 // Guess the amount of live data for stats.
891 /* Free the small objects allocated via allocate(), since this will
892 * all have been copied into G0S1 now.
894 if (small_alloc_list != NULL) {
895 freeChain(small_alloc_list);
897 small_alloc_list = NULL;
901 alloc_blocks_lim = RtsFlags.GcFlags.minAllocAreaSize;
903 // Start a new pinned_object_block
904 pinned_object_block = NULL;
906 /* Free the mark stack.
908 if (mark_stack_bdescr != NULL) {
909 freeGroup(mark_stack_bdescr);
914 for (g = 0; g <= N; g++) {
915 for (s = 0; s < generations[g].n_steps; s++) {
916 stp = &generations[g].steps[s];
917 if (stp->is_compacted && stp->bitmap != NULL) {
918 freeGroup(stp->bitmap);
923 /* Two-space collector:
924 * Free the old to-space, and estimate the amount of live data.
926 if (RtsFlags.GcFlags.generations == 1) {
929 if (old_to_blocks != NULL) {
930 freeChain(old_to_blocks);
932 for (bd = g0s0->to_blocks; bd != NULL; bd = bd->link) {
933 bd->flags = 0; // now from-space
936 /* For a two-space collector, we need to resize the nursery. */
938 /* set up a new nursery. Allocate a nursery size based on a
939 * function of the amount of live data (by default a factor of 2)
940 * Use the blocks from the old nursery if possible, freeing up any
943 * If we get near the maximum heap size, then adjust our nursery
944 * size accordingly. If the nursery is the same size as the live
945 * data (L), then we need 3L bytes. We can reduce the size of the
946 * nursery to bring the required memory down near 2L bytes.
948 * A normal 2-space collector would need 4L bytes to give the same
949 * performance we get from 3L bytes, reducing to the same
950 * performance at 2L bytes.
952 blocks = g0s0->n_to_blocks;
954 if ( RtsFlags.GcFlags.maxHeapSize != 0 &&
955 blocks * RtsFlags.GcFlags.oldGenFactor * 2 >
956 RtsFlags.GcFlags.maxHeapSize ) {
957 long adjusted_blocks; // signed on purpose
960 adjusted_blocks = (RtsFlags.GcFlags.maxHeapSize - 2 * blocks);
961 IF_DEBUG(gc, belch("@@ Near maximum heap size of 0x%x blocks, blocks = %d, adjusted to %ld", RtsFlags.GcFlags.maxHeapSize, blocks, adjusted_blocks));
962 pc_free = adjusted_blocks * 100 / RtsFlags.GcFlags.maxHeapSize;
963 if (pc_free < RtsFlags.GcFlags.pcFreeHeap) /* might even be < 0 */ {
966 blocks = adjusted_blocks;
969 blocks *= RtsFlags.GcFlags.oldGenFactor;
970 if (blocks < RtsFlags.GcFlags.minAllocAreaSize) {
971 blocks = RtsFlags.GcFlags.minAllocAreaSize;
974 resizeNursery(blocks);
977 /* Generational collector:
978 * If the user has given us a suggested heap size, adjust our
979 * allocation area to make best use of the memory available.
982 if (RtsFlags.GcFlags.heapSizeSuggestion) {
984 nat needed = calcNeeded(); // approx blocks needed at next GC
986 /* Guess how much will be live in generation 0 step 0 next time.
987 * A good approximation is obtained by finding the
988 * percentage of g0s0 that was live at the last minor GC.
991 g0s0_pcnt_kept = (new_blocks * 100) / g0s0->n_blocks;
994 /* Estimate a size for the allocation area based on the
995 * information available. We might end up going slightly under
996 * or over the suggested heap size, but we should be pretty
999 * Formula: suggested - needed
1000 * ----------------------------
1001 * 1 + g0s0_pcnt_kept/100
1003 * where 'needed' is the amount of memory needed at the next
1004 * collection for collecting all steps except g0s0.
1007 (((long)RtsFlags.GcFlags.heapSizeSuggestion - (long)needed) * 100) /
1008 (100 + (long)g0s0_pcnt_kept);
1010 if (blocks < (long)RtsFlags.GcFlags.minAllocAreaSize) {
1011 blocks = RtsFlags.GcFlags.minAllocAreaSize;
1014 resizeNursery((nat)blocks);
1017 // we might have added extra large blocks to the nursery, so
1018 // resize back to minAllocAreaSize again.
1019 resizeNursery(RtsFlags.GcFlags.minAllocAreaSize);
1023 // mark the garbage collected CAFs as dead
1024 #if 0 && defined(DEBUG) // doesn't work at the moment
1025 if (major_gc) { gcCAFs(); }
1029 // resetStaticObjectForRetainerProfiling() must be called before
1031 resetStaticObjectForRetainerProfiling();
1034 // zero the scavenged static object list
1036 zero_static_object_list(scavenged_static_objects);
1039 // Reset the nursery
1042 RELEASE_LOCK(&sched_mutex);
1044 // start any pending finalizers
1045 scheduleFinalizers(old_weak_ptr_list);
1047 // send exceptions to any threads which were about to die
1048 resurrectThreads(resurrected_threads);
1050 ACQUIRE_LOCK(&sched_mutex);
1052 // Update the stable pointer hash table.
1053 updateStablePtrTable(major_gc);
1055 // check sanity after GC
1056 IF_DEBUG(sanity, checkSanity());
1058 // extra GC trace info
1059 IF_DEBUG(gc, statDescribeGens());
1062 // symbol-table based profiling
1063 /* heapCensus(to_blocks); */ /* ToDo */
1066 // restore enclosing cost centre
1071 // check for memory leaks if sanity checking is on
1072 IF_DEBUG(sanity, memInventory());
1074 #ifdef RTS_GTK_FRONTPANEL
1075 if (RtsFlags.GcFlags.frontpanel) {
1076 updateFrontPanelAfterGC( N, live );
1080 // ok, GC over: tell the stats department what happened.
1081 stat_endGC(allocated, collected, live, copied, N);
1083 #ifndef mingw32_TARGET_OS
1084 // unblock signals again
1085 unblockUserSignals();
1092 /* -----------------------------------------------------------------------------
1095 traverse_weak_ptr_list is called possibly many times during garbage
1096 collection. It returns a flag indicating whether it did any work
1097 (i.e. called evacuate on any live pointers).
1099 Invariant: traverse_weak_ptr_list is called when the heap is in an
1100 idempotent state. That means that there are no pending
1101 evacuate/scavenge operations. This invariant helps the weak
1102 pointer code decide which weak pointers are dead - if there are no
1103 new live weak pointers, then all the currently unreachable ones are
1106 For generational GC: we just don't try to finalize weak pointers in
1107 older generations than the one we're collecting. This could
1108 probably be optimised by keeping per-generation lists of weak
1109 pointers, but for a few weak pointers this scheme will work.
1111 There are three distinct stages to processing weak pointers:
1113 - weak_stage == WeakPtrs
1115 We process all the weak pointers whos keys are alive (evacuate
1116 their values and finalizers), and repeat until we can find no new
1117 live keys. If no live keys are found in this pass, then we
1118 evacuate the finalizers of all the dead weak pointers in order to
1121 - weak_stage == WeakThreads
1123 Now, we discover which *threads* are still alive. Pointers to
1124 threads from the all_threads and main thread lists are the
1125 weakest of all: a pointers from the finalizer of a dead weak
1126 pointer can keep a thread alive. Any threads found to be unreachable
1127 are evacuated and placed on the resurrected_threads list so we
1128 can send them a signal later.
1130 - weak_stage == WeakDone
1132 No more evacuation is done.
1134 -------------------------------------------------------------------------- */
1137 traverse_weak_ptr_list(void)
1139 StgWeak *w, **last_w, *next_w;
1141 rtsBool flag = rtsFalse;
1143 switch (weak_stage) {
1149 /* doesn't matter where we evacuate values/finalizers to, since
1150 * these pointers are treated as roots (iff the keys are alive).
1154 last_w = &old_weak_ptr_list;
1155 for (w = old_weak_ptr_list; w != NULL; w = next_w) {
1157 /* There might be a DEAD_WEAK on the list if finalizeWeak# was
1158 * called on a live weak pointer object. Just remove it.
1160 if (w->header.info == &stg_DEAD_WEAK_info) {
1161 next_w = ((StgDeadWeak *)w)->link;
1166 switch (get_itbl(w)->type) {
1169 next_w = (StgWeak *)((StgEvacuated *)w)->evacuee;
1174 /* Now, check whether the key is reachable.
1176 new = isAlive(w->key);
1179 // evacuate the value and finalizer
1180 w->value = evacuate(w->value);
1181 w->finalizer = evacuate(w->finalizer);
1182 // remove this weak ptr from the old_weak_ptr list
1184 // and put it on the new weak ptr list
1186 w->link = weak_ptr_list;
1189 IF_DEBUG(weak, belch("Weak pointer still alive at %p -> %p",
1194 last_w = &(w->link);
1200 barf("traverse_weak_ptr_list: not WEAK");
1204 /* If we didn't make any changes, then we can go round and kill all
1205 * the dead weak pointers. The old_weak_ptr list is used as a list
1206 * of pending finalizers later on.
1208 if (flag == rtsFalse) {
1209 for (w = old_weak_ptr_list; w; w = w->link) {
1210 w->finalizer = evacuate(w->finalizer);
1213 // Next, move to the WeakThreads stage after fully
1214 // scavenging the finalizers we've just evacuated.
1215 weak_stage = WeakThreads;
1221 /* Now deal with the all_threads list, which behaves somewhat like
1222 * the weak ptr list. If we discover any threads that are about to
1223 * become garbage, we wake them up and administer an exception.
1226 StgTSO *t, *tmp, *next, **prev;
1228 prev = &old_all_threads;
1229 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1231 (StgClosure *)tmp = isAlive((StgClosure *)t);
1237 ASSERT(get_itbl(t)->type == TSO);
1238 switch (t->what_next) {
1239 case ThreadRelocated:
1244 case ThreadComplete:
1245 // finshed or died. The thread might still be alive, but we
1246 // don't keep it on the all_threads list. Don't forget to
1247 // stub out its global_link field.
1248 next = t->global_link;
1249 t->global_link = END_TSO_QUEUE;
1257 // not alive (yet): leave this thread on the
1258 // old_all_threads list.
1259 prev = &(t->global_link);
1260 next = t->global_link;
1263 // alive: move this thread onto the all_threads list.
1264 next = t->global_link;
1265 t->global_link = all_threads;
1272 /* And resurrect any threads which were about to become garbage.
1275 StgTSO *t, *tmp, *next;
1276 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1277 next = t->global_link;
1278 (StgClosure *)tmp = evacuate((StgClosure *)t);
1279 tmp->global_link = resurrected_threads;
1280 resurrected_threads = tmp;
1284 weak_stage = WeakDone; // *now* we're done,
1285 return rtsTrue; // but one more round of scavenging, please
1288 barf("traverse_weak_ptr_list");
1293 /* -----------------------------------------------------------------------------
1294 After GC, the live weak pointer list may have forwarding pointers
1295 on it, because a weak pointer object was evacuated after being
1296 moved to the live weak pointer list. We remove those forwarding
1299 Also, we don't consider weak pointer objects to be reachable, but
1300 we must nevertheless consider them to be "live" and retain them.
1301 Therefore any weak pointer objects which haven't as yet been
1302 evacuated need to be evacuated now.
1303 -------------------------------------------------------------------------- */
1307 mark_weak_ptr_list ( StgWeak **list )
1309 StgWeak *w, **last_w;
1312 for (w = *list; w; w = w->link) {
1313 // w might be WEAK, EVACUATED, or DEAD_WEAK (actually CON_STATIC) here
1314 ASSERT(w->header.info == &stg_DEAD_WEAK_info
1315 || get_itbl(w)->type == WEAK || get_itbl(w)->type == EVACUATED);
1316 (StgClosure *)w = evacuate((StgClosure *)w);
1318 last_w = &(w->link);
1322 /* -----------------------------------------------------------------------------
1323 isAlive determines whether the given closure is still alive (after
1324 a garbage collection) or not. It returns the new address of the
1325 closure if it is alive, or NULL otherwise.
1327 NOTE: Use it before compaction only!
1328 -------------------------------------------------------------------------- */
1332 isAlive(StgClosure *p)
1334 const StgInfoTable *info;
1339 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
1342 // ignore static closures
1344 // ToDo: for static closures, check the static link field.
1345 // Problem here is that we sometimes don't set the link field, eg.
1346 // for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
1348 if (!HEAP_ALLOCED(p)) {
1352 // ignore closures in generations that we're not collecting.
1354 if (bd->gen_no > N) {
1358 // if it's a pointer into to-space, then we're done
1359 if (bd->flags & BF_EVACUATED) {
1363 // large objects use the evacuated flag
1364 if (bd->flags & BF_LARGE) {
1368 // check the mark bit for compacted steps
1369 if (bd->step->is_compacted && is_marked((P_)p,bd)) {
1373 switch (info->type) {
1378 case IND_OLDGEN: // rely on compatible layout with StgInd
1379 case IND_OLDGEN_PERM:
1380 // follow indirections
1381 p = ((StgInd *)p)->indirectee;
1386 return ((StgEvacuated *)p)->evacuee;
1389 if (((StgTSO *)p)->what_next == ThreadRelocated) {
1390 p = (StgClosure *)((StgTSO *)p)->link;
1403 mark_root(StgClosure **root)
1405 *root = evacuate(*root);
1408 static __inline__ void
1409 upd_evacuee(StgClosure *p, StgClosure *dest)
1411 // Source object must be in from-space:
1412 ASSERT((Bdescr((P_)p)->flags & BF_EVACUATED) == 0);
1413 // not true: (ToDo: perhaps it should be)
1414 // ASSERT(Bdescr((P_)dest)->flags & BF_EVACUATED);
1415 p->header.info = &stg_EVACUATED_info;
1416 ((StgEvacuated *)p)->evacuee = dest;
1420 static __inline__ StgClosure *
1421 copy(StgClosure *src, nat size, step *stp)
1426 nat size_org = size;
1429 TICK_GC_WORDS_COPIED(size);
1430 /* Find out where we're going, using the handy "to" pointer in
1431 * the step of the source object. If it turns out we need to
1432 * evacuate to an older generation, adjust it here (see comment
1435 if (stp->gen_no < evac_gen) {
1436 #ifdef NO_EAGER_PROMOTION
1437 failed_to_evac = rtsTrue;
1439 stp = &generations[evac_gen].steps[0];
1443 /* chain a new block onto the to-space for the destination step if
1446 if (stp->hp + size >= stp->hpLim) {
1447 gc_alloc_block(stp);
1450 for(to = stp->hp, from = (P_)src; size>0; --size) {
1456 upd_evacuee(src,(StgClosure *)dest);
1458 // We store the size of the just evacuated object in the LDV word so that
1459 // the profiler can guess the position of the next object later.
1460 SET_EVACUAEE_FOR_LDV(src, size_org);
1462 return (StgClosure *)dest;
1465 /* Special version of copy() for when we only want to copy the info
1466 * pointer of an object, but reserve some padding after it. This is
1467 * used to optimise evacuation of BLACKHOLEs.
1472 copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *stp)
1477 nat size_to_copy_org = size_to_copy;
1480 TICK_GC_WORDS_COPIED(size_to_copy);
1481 if (stp->gen_no < evac_gen) {
1482 #ifdef NO_EAGER_PROMOTION
1483 failed_to_evac = rtsTrue;
1485 stp = &generations[evac_gen].steps[0];
1489 if (stp->hp + size_to_reserve >= stp->hpLim) {
1490 gc_alloc_block(stp);
1493 for(to = stp->hp, from = (P_)src; size_to_copy>0; --size_to_copy) {
1498 stp->hp += size_to_reserve;
1499 upd_evacuee(src,(StgClosure *)dest);
1501 // We store the size of the just evacuated object in the LDV word so that
1502 // the profiler can guess the position of the next object later.
1503 // size_to_copy_org is wrong because the closure already occupies size_to_reserve
1505 SET_EVACUAEE_FOR_LDV(src, size_to_reserve);
1507 if (size_to_reserve - size_to_copy_org > 0)
1508 FILL_SLOP(stp->hp - 1, (int)(size_to_reserve - size_to_copy_org));
1510 return (StgClosure *)dest;
1514 /* -----------------------------------------------------------------------------
1515 Evacuate a large object
1517 This just consists of removing the object from the (doubly-linked)
1518 step->large_objects list, and linking it on to the (singly-linked)
1519 step->new_large_objects list, from where it will be scavenged later.
1521 Convention: bd->flags has BF_EVACUATED set for a large object
1522 that has been evacuated, or unset otherwise.
1523 -------------------------------------------------------------------------- */
1527 evacuate_large(StgPtr p)
1529 bdescr *bd = Bdescr(p);
1532 // object must be at the beginning of the block (or be a ByteArray)
1533 ASSERT(get_itbl((StgClosure *)p)->type == ARR_WORDS ||
1534 (((W_)p & BLOCK_MASK) == 0));
1536 // already evacuated?
1537 if (bd->flags & BF_EVACUATED) {
1538 /* Don't forget to set the failed_to_evac flag if we didn't get
1539 * the desired destination (see comments in evacuate()).
1541 if (bd->gen_no < evac_gen) {
1542 failed_to_evac = rtsTrue;
1543 TICK_GC_FAILED_PROMOTION();
1549 // remove from large_object list
1551 bd->u.back->link = bd->link;
1552 } else { // first object in the list
1553 stp->large_objects = bd->link;
1556 bd->link->u.back = bd->u.back;
1559 /* link it on to the evacuated large object list of the destination step
1562 if (stp->gen_no < evac_gen) {
1563 #ifdef NO_EAGER_PROMOTION
1564 failed_to_evac = rtsTrue;
1566 stp = &generations[evac_gen].steps[0];
1571 bd->gen_no = stp->gen_no;
1572 bd->link = stp->new_large_objects;
1573 stp->new_large_objects = bd;
1574 bd->flags |= BF_EVACUATED;
1577 /* -----------------------------------------------------------------------------
1578 Adding a MUT_CONS to an older generation.
1580 This is necessary from time to time when we end up with an
1581 old-to-new generation pointer in a non-mutable object. We defer
1582 the promotion until the next GC.
1583 -------------------------------------------------------------------------- */
1586 mkMutCons(StgClosure *ptr, generation *gen)
1591 stp = &gen->steps[0];
1593 /* chain a new block onto the to-space for the destination step if
1596 if (stp->hp + sizeofW(StgIndOldGen) >= stp->hpLim) {
1597 gc_alloc_block(stp);
1600 q = (StgMutVar *)stp->hp;
1601 stp->hp += sizeofW(StgMutVar);
1603 SET_HDR(q,&stg_MUT_CONS_info,CCS_GC);
1605 recordOldToNewPtrs((StgMutClosure *)q);
1607 return (StgClosure *)q;
1610 /* -----------------------------------------------------------------------------
1613 This is called (eventually) for every live object in the system.
1615 The caller to evacuate specifies a desired generation in the
1616 evac_gen global variable. The following conditions apply to
1617 evacuating an object which resides in generation M when we're
1618 collecting up to generation N
1622 else evac to step->to
1624 if M < evac_gen evac to evac_gen, step 0
1626 if the object is already evacuated, then we check which generation
1629 if M >= evac_gen do nothing
1630 if M < evac_gen set failed_to_evac flag to indicate that we
1631 didn't manage to evacuate this object into evac_gen.
1633 -------------------------------------------------------------------------- */
1636 evacuate(StgClosure *q)
1641 const StgInfoTable *info;
1644 if (HEAP_ALLOCED(q)) {
1647 if (bd->gen_no > N) {
1648 /* Can't evacuate this object, because it's in a generation
1649 * older than the ones we're collecting. Let's hope that it's
1650 * in evac_gen or older, or we will have to arrange to track
1651 * this pointer using the mutable list.
1653 if (bd->gen_no < evac_gen) {
1655 failed_to_evac = rtsTrue;
1656 TICK_GC_FAILED_PROMOTION();
1661 /* evacuate large objects by re-linking them onto a different list.
1663 if (bd->flags & BF_LARGE) {
1665 if (info->type == TSO &&
1666 ((StgTSO *)q)->what_next == ThreadRelocated) {
1667 q = (StgClosure *)((StgTSO *)q)->link;
1670 evacuate_large((P_)q);
1674 /* If the object is in a step that we're compacting, then we
1675 * need to use an alternative evacuate procedure.
1677 if (bd->step->is_compacted) {
1678 if (!is_marked((P_)q,bd)) {
1680 if (mark_stack_full()) {
1681 mark_stack_overflowed = rtsTrue;
1684 push_mark_stack((P_)q);
1692 else stp = NULL; // make sure copy() will crash if HEAP_ALLOCED is wrong
1695 // make sure the info pointer is into text space
1696 ASSERT(LOOKS_LIKE_CLOSURE_PTR(q));
1699 switch (info -> type) {
1703 return copy(q,sizeW_fromITBL(info),stp);
1707 StgWord w = (StgWord)q->payload[0];
1708 if (q->header.info == Czh_con_info &&
1709 // unsigned, so always true: (StgChar)w >= MIN_CHARLIKE &&
1710 (StgChar)w <= MAX_CHARLIKE) {
1711 return (StgClosure *)CHARLIKE_CLOSURE((StgChar)w);
1713 if (q->header.info == Izh_con_info &&
1714 (StgInt)w >= MIN_INTLIKE && (StgInt)w <= MAX_INTLIKE) {
1715 return (StgClosure *)INTLIKE_CLOSURE((StgInt)w);
1717 // else, fall through ...
1723 return copy(q,sizeofW(StgHeader)+1,stp);
1725 case THUNK_1_0: // here because of MIN_UPD_SIZE
1730 #ifdef NO_PROMOTE_THUNKS
1731 if (bd->gen_no == 0 &&
1732 bd->step->no != 0 &&
1733 bd->step->no == generations[bd->gen_no].n_steps-1) {
1737 return copy(q,sizeofW(StgHeader)+2,stp);
1745 return copy(q,sizeofW(StgHeader)+2,stp);
1751 case IND_OLDGEN_PERM:
1755 return copy(q,sizeW_fromITBL(info),stp);
1758 return copy(q,bco_sizeW((StgBCO *)q),stp);
1761 case SE_CAF_BLACKHOLE:
1764 return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
1767 to = copy(q,BLACKHOLE_sizeW(),stp);
1770 case THUNK_SELECTOR:
1774 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
1775 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1778 p = eval_thunk_selector(info->layout.selector_offset,
1782 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1784 // q is still BLACKHOLE'd.
1785 thunk_selector_depth++;
1787 thunk_selector_depth--;
1790 // We store the size of the just evacuated object in the
1791 // LDV word so that the profiler can guess the position of
1792 // the next object later.
1793 SET_EVACUAEE_FOR_LDV(q, THUNK_SELECTOR_sizeW());
1801 // follow chains of indirections, don't evacuate them
1802 q = ((StgInd*)q)->indirectee;
1806 if (info->srt_len > 0 && major_gc &&
1807 THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
1808 THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
1809 static_objects = (StgClosure *)q;
1814 if (info->srt_len > 0 && major_gc &&
1815 FUN_STATIC_LINK((StgClosure *)q) == NULL) {
1816 FUN_STATIC_LINK((StgClosure *)q) = static_objects;
1817 static_objects = (StgClosure *)q;
1822 /* If q->saved_info != NULL, then it's a revertible CAF - it'll be
1823 * on the CAF list, so don't do anything with it here (we'll
1824 * scavenge it later).
1827 && ((StgIndStatic *)q)->saved_info == NULL
1828 && IND_STATIC_LINK((StgClosure *)q) == NULL) {
1829 IND_STATIC_LINK((StgClosure *)q) = static_objects;
1830 static_objects = (StgClosure *)q;
1835 if (major_gc && STATIC_LINK(info,(StgClosure *)q) == NULL) {
1836 STATIC_LINK(info,(StgClosure *)q) = static_objects;
1837 static_objects = (StgClosure *)q;
1841 case CONSTR_INTLIKE:
1842 case CONSTR_CHARLIKE:
1843 case CONSTR_NOCAF_STATIC:
1844 /* no need to put these on the static linked list, they don't need
1858 // shouldn't see these
1859 barf("evacuate: stack frame at %p\n", q);
1863 return copy(q,pap_sizeW((StgPAP*)q),stp);
1866 return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp);
1869 /* Already evacuated, just return the forwarding address.
1870 * HOWEVER: if the requested destination generation (evac_gen) is
1871 * older than the actual generation (because the object was
1872 * already evacuated to a younger generation) then we have to
1873 * set the failed_to_evac flag to indicate that we couldn't
1874 * manage to promote the object to the desired generation.
1876 if (evac_gen > 0) { // optimisation
1877 StgClosure *p = ((StgEvacuated*)q)->evacuee;
1878 if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < evac_gen) {
1879 failed_to_evac = rtsTrue;
1880 TICK_GC_FAILED_PROMOTION();
1883 return ((StgEvacuated*)q)->evacuee;
1886 // just copy the block
1887 return copy(q,arr_words_sizeW((StgArrWords *)q),stp);
1890 case MUT_ARR_PTRS_FROZEN:
1891 // just copy the block
1892 return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
1896 StgTSO *tso = (StgTSO *)q;
1898 /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
1900 if (tso->what_next == ThreadRelocated) {
1901 q = (StgClosure *)tso->link;
1905 /* To evacuate a small TSO, we need to relocate the update frame
1909 StgTSO *new_tso = (StgTSO *)copy((StgClosure *)tso,tso_sizeW(tso),stp);
1910 move_TSO(tso, new_tso);
1911 return (StgClosure *)new_tso;
1916 case RBH: // cf. BLACKHOLE_BQ
1918 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
1919 to = copy(q,BLACKHOLE_sizeW(),stp);
1920 //ToDo: derive size etc from reverted IP
1921 //to = copy(q,size,stp);
1923 belch("@@ evacuate: RBH %p (%s) to %p (%s)",
1924 q, info_type(q), to, info_type(to)));
1929 ASSERT(sizeofW(StgBlockedFetch) >= MIN_NONUPD_SIZE);
1930 to = copy(q,sizeofW(StgBlockedFetch),stp);
1932 belch("@@ evacuate: %p (%s) to %p (%s)",
1933 q, info_type(q), to, info_type(to)));
1940 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1941 to = copy(q,sizeofW(StgFetchMe),stp);
1943 belch("@@ evacuate: %p (%s) to %p (%s)",
1944 q, info_type(q), to, info_type(to)));
1948 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1949 to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
1951 belch("@@ evacuate: %p (%s) to %p (%s)",
1952 q, info_type(q), to, info_type(to)));
1957 barf("evacuate: strange closure type %d", (int)(info->type));
1963 /* -----------------------------------------------------------------------------
1964 Evaluate a THUNK_SELECTOR if possible.
1966 returns: NULL if we couldn't evaluate this THUNK_SELECTOR, or
1967 a closure pointer if we evaluated it and this is the result. Note
1968 that "evaluating" the THUNK_SELECTOR doesn't necessarily mean
1969 reducing it to HNF, just that we have eliminated the selection.
1970 The result might be another thunk, or even another THUNK_SELECTOR.
1972 If the return value is non-NULL, the original selector thunk has
1973 been BLACKHOLE'd, and should be updated with an indirection or a
1974 forwarding pointer. If the return value is NULL, then the selector
1976 -------------------------------------------------------------------------- */
1979 eval_thunk_selector( nat field, StgSelector * p )
1982 const StgInfoTable *info_ptr;
1983 StgClosure *selectee;
1985 selectee = p->selectee;
1987 // Save the real info pointer (NOTE: not the same as get_itbl()).
1988 info_ptr = p->header.info;
1990 // If the THUNK_SELECTOR is in a generation that we are not
1991 // collecting, then bail out early. We won't be able to save any
1992 // space in any case, and updating with an indirection is trickier
1994 if (Bdescr((StgPtr)p)->gen_no > N) {
1998 // BLACKHOLE the selector thunk, since it is now under evaluation.
1999 // This is important to stop us going into an infinite loop if
2000 // this selector thunk eventually refers to itself.
2001 SET_INFO(p,&stg_BLACKHOLE_info);
2005 // We don't want to end up in to-space, because this causes
2006 // problems when the GC later tries to evacuate the result of
2007 // eval_thunk_selector(). There are various ways this could
2010 // - following an IND_STATIC
2012 // - when the old generation is compacted, the mark phase updates
2013 // from-space pointers to be to-space pointers, and we can't
2014 // reliably tell which we're following (eg. from an IND_STATIC).
2016 // So we use the block-descriptor test to find out if we're in
2019 if (Bdescr((StgPtr)selectee)->flags & BF_EVACUATED) {
2023 info = get_itbl(selectee);
2024 switch (info->type) {
2032 case CONSTR_NOCAF_STATIC:
2033 // check that the size is in range
2034 ASSERT(field < (StgWord32)(info->layout.payload.ptrs +
2035 info->layout.payload.nptrs));
2037 // ToDo: shouldn't we test whether this pointer is in
2039 return selectee->payload[field];
2044 case IND_OLDGEN_PERM:
2046 selectee = ((StgInd *)selectee)->indirectee;
2050 // We don't follow pointers into to-space; the constructor
2051 // has already been evacuated, so we won't save any space
2052 // leaks by evaluating this selector thunk anyhow.
2055 case THUNK_SELECTOR:
2059 // check that we don't recurse too much, re-using the
2060 // depth bound also used in evacuate().
2061 thunk_selector_depth++;
2062 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
2066 val = eval_thunk_selector(info->layout.selector_offset,
2067 (StgSelector *)selectee);
2069 thunk_selector_depth--;
2074 // We evaluated this selector thunk, so update it with
2075 // an indirection. NOTE: we don't use UPD_IND here,
2076 // because we are guaranteed that p is in a generation
2077 // that we are collecting, and we never want to put the
2078 // indirection on a mutable list.
2080 // For the purposes of LDV profiling, we have destroyed
2081 // the original selector thunk.
2082 SET_INFO(p, info_ptr);
2083 LDV_recordDead_FILL_SLOP_DYNAMIC(selectee);
2085 ((StgInd *)selectee)->indirectee = val;
2086 SET_INFO(selectee,&stg_IND_info);
2088 // For the purposes of LDV profiling, we have created an
2090 LDV_recordCreate(selectee);
2106 case SE_CAF_BLACKHOLE:
2119 // not evaluated yet
2123 barf("eval_thunk_selector: strange selectee %d",
2128 // We didn't manage to evaluate this thunk; restore the old info pointer
2129 SET_INFO(p, info_ptr);
2133 /* -----------------------------------------------------------------------------
2134 move_TSO is called to update the TSO structure after it has been
2135 moved from one place to another.
2136 -------------------------------------------------------------------------- */
2139 move_TSO (StgTSO *src, StgTSO *dest)
2143 // relocate the stack pointers...
2144 diff = (StgPtr)dest - (StgPtr)src; // In *words*
2145 dest->sp = (StgPtr)dest->sp + diff;
2148 /* evacuate the SRT. If srt_len is zero, then there isn't an
2149 * srt field in the info table. That's ok, because we'll
2150 * never dereference it.
2153 scavenge_srt (StgClosure **srt, nat srt_len)
2155 StgClosure **srt_end;
2157 srt_end = srt + srt_len;
2159 for (; srt < srt_end; srt++) {
2160 /* Special-case to handle references to closures hiding out in DLLs, since
2161 double indirections required to get at those. The code generator knows
2162 which is which when generating the SRT, so it stores the (indirect)
2163 reference to the DLL closure in the table by first adding one to it.
2164 We check for this here, and undo the addition before evacuating it.
2166 If the SRT entry hasn't got bit 0 set, the SRT entry points to a
2167 closure that's fixed at link-time, and no extra magic is required.
2169 #ifdef ENABLE_WIN32_DLL_SUPPORT
2170 if ( (unsigned long)(*srt) & 0x1 ) {
2171 evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
2183 scavenge_thunk_srt(const StgInfoTable *info)
2185 StgThunkInfoTable *thunk_info;
2187 thunk_info = itbl_to_thunk_itbl(info);
2188 scavenge_srt((StgClosure **)thunk_info->srt, thunk_info->i.srt_len);
2192 scavenge_fun_srt(const StgInfoTable *info)
2194 StgFunInfoTable *fun_info;
2196 fun_info = itbl_to_fun_itbl(info);
2197 scavenge_srt((StgClosure **)fun_info->srt, fun_info->i.srt_len);
2201 scavenge_ret_srt(const StgInfoTable *info)
2203 StgRetInfoTable *ret_info;
2205 ret_info = itbl_to_ret_itbl(info);
2206 scavenge_srt((StgClosure **)ret_info->srt, ret_info->i.srt_len);
2209 /* -----------------------------------------------------------------------------
2211 -------------------------------------------------------------------------- */
2214 scavengeTSO (StgTSO *tso)
2216 // chase the link field for any TSOs on the same queue
2217 (StgClosure *)tso->link = evacuate((StgClosure *)tso->link);
2218 if ( tso->why_blocked == BlockedOnMVar
2219 || tso->why_blocked == BlockedOnBlackHole
2220 || tso->why_blocked == BlockedOnException
2222 || tso->why_blocked == BlockedOnGA
2223 || tso->why_blocked == BlockedOnGA_NoSend
2226 tso->block_info.closure = evacuate(tso->block_info.closure);
2228 if ( tso->blocked_exceptions != NULL ) {
2229 tso->blocked_exceptions =
2230 (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
2233 // scavenge this thread's stack
2234 scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
2237 /* -----------------------------------------------------------------------------
2238 Blocks of function args occur on the stack (at the top) and
2240 -------------------------------------------------------------------------- */
2242 static inline StgPtr
2243 scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
2250 switch (fun_info->fun_type) {
2252 bitmap = BITMAP_BITS(fun_info->bitmap);
2253 size = BITMAP_SIZE(fun_info->bitmap);
2256 size = ((StgLargeBitmap *)fun_info->bitmap)->size;
2257 scavenge_large_bitmap(p, (StgLargeBitmap *)fun_info->bitmap, size);
2261 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->fun_type]);
2262 size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->fun_type]);
2265 if ((bitmap & 1) == 0) {
2266 (StgClosure *)*p = evacuate((StgClosure *)*p);
2269 bitmap = bitmap >> 1;
2277 static inline StgPtr
2278 scavenge_PAP (StgPAP *pap)
2281 StgWord bitmap, size;
2282 StgFunInfoTable *fun_info;
2284 pap->fun = evacuate(pap->fun);
2285 fun_info = get_fun_itbl(pap->fun);
2286 ASSERT(fun_info->i.type != PAP);
2288 p = (StgPtr)pap->payload;
2291 switch (fun_info->fun_type) {
2293 bitmap = BITMAP_BITS(fun_info->bitmap);
2296 scavenge_large_bitmap(p, (StgLargeBitmap *)fun_info->bitmap, size);
2300 scavenge_large_bitmap((StgPtr)pap->payload, BCO_BITMAP(pap->fun), size);
2304 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->fun_type]);
2308 if ((bitmap & 1) == 0) {
2309 (StgClosure *)*p = evacuate((StgClosure *)*p);
2312 bitmap = bitmap >> 1;
2320 /* -----------------------------------------------------------------------------
2321 Scavenge a given step until there are no more objects in this step
2324 evac_gen is set by the caller to be either zero (for a step in a
2325 generation < N) or G where G is the generation of the step being
2328 We sometimes temporarily change evac_gen back to zero if we're
2329 scavenging a mutable object where early promotion isn't such a good
2331 -------------------------------------------------------------------------- */
2339 nat saved_evac_gen = evac_gen;
2344 failed_to_evac = rtsFalse;
2346 /* scavenge phase - standard breadth-first scavenging of the
2350 while (bd != stp->hp_bd || p < stp->hp) {
2352 // If we're at the end of this block, move on to the next block
2353 if (bd != stp->hp_bd && p == bd->free) {
2359 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2360 info = get_itbl((StgClosure *)p);
2362 ASSERT(thunk_selector_depth == 0);
2365 switch (info->type) {
2368 /* treat MVars specially, because we don't want to evacuate the
2369 * mut_link field in the middle of the closure.
2372 StgMVar *mvar = ((StgMVar *)p);
2374 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
2375 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
2376 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
2377 evac_gen = saved_evac_gen;
2378 recordMutable((StgMutClosure *)mvar);
2379 failed_to_evac = rtsFalse; // mutable.
2380 p += sizeofW(StgMVar);
2385 scavenge_fun_srt(info);
2386 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2387 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2388 p += sizeofW(StgHeader) + 2;
2392 scavenge_thunk_srt(info);
2394 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2395 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2396 p += sizeofW(StgHeader) + 2;
2400 scavenge_thunk_srt(info);
2401 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2402 p += sizeofW(StgHeader) + 2; // MIN_UPD_SIZE
2406 scavenge_fun_srt(info);
2408 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2409 p += sizeofW(StgHeader) + 1;
2413 scavenge_thunk_srt(info);
2414 p += sizeofW(StgHeader) + 2; // MIN_UPD_SIZE
2418 scavenge_fun_srt(info);
2420 p += sizeofW(StgHeader) + 1;
2424 scavenge_thunk_srt(info);
2425 p += sizeofW(StgHeader) + 2;
2429 scavenge_fun_srt(info);
2431 p += sizeofW(StgHeader) + 2;
2435 scavenge_thunk_srt(info);
2436 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2437 p += sizeofW(StgHeader) + 2;
2441 scavenge_fun_srt(info);
2443 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2444 p += sizeofW(StgHeader) + 2;
2448 scavenge_fun_srt(info);
2452 scavenge_thunk_srt(info);
2463 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2464 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2465 (StgClosure *)*p = evacuate((StgClosure *)*p);
2467 p += info->layout.payload.nptrs;
2472 StgBCO *bco = (StgBCO *)p;
2473 (StgClosure *)bco->instrs = evacuate((StgClosure *)bco->instrs);
2474 (StgClosure *)bco->literals = evacuate((StgClosure *)bco->literals);
2475 (StgClosure *)bco->ptrs = evacuate((StgClosure *)bco->ptrs);
2476 (StgClosure *)bco->itbls = evacuate((StgClosure *)bco->itbls);
2477 p += bco_sizeW(bco);
2482 if (stp->gen->no != 0) {
2485 // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an
2486 // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
2487 LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
2490 // Todo: maybe use SET_HDR() and remove LDV_recordCreate()?
2492 SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
2495 // We pretend that p has just been created.
2496 LDV_recordCreate((StgClosure *)p);
2500 case IND_OLDGEN_PERM:
2501 ((StgIndOldGen *)p)->indirectee =
2502 evacuate(((StgIndOldGen *)p)->indirectee);
2503 if (failed_to_evac) {
2504 failed_to_evac = rtsFalse;
2505 recordOldToNewPtrs((StgMutClosure *)p);
2507 p += sizeofW(StgIndOldGen);
2512 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2513 evac_gen = saved_evac_gen;
2514 recordMutable((StgMutClosure *)p);
2515 failed_to_evac = rtsFalse; // mutable anyhow
2516 p += sizeofW(StgMutVar);
2521 failed_to_evac = rtsFalse; // mutable anyhow
2522 p += sizeofW(StgMutVar);
2526 case SE_CAF_BLACKHOLE:
2529 p += BLACKHOLE_sizeW();
2534 StgBlockingQueue *bh = (StgBlockingQueue *)p;
2535 (StgClosure *)bh->blocking_queue =
2536 evacuate((StgClosure *)bh->blocking_queue);
2537 recordMutable((StgMutClosure *)bh);
2538 failed_to_evac = rtsFalse;
2539 p += BLACKHOLE_sizeW();
2543 case THUNK_SELECTOR:
2545 StgSelector *s = (StgSelector *)p;
2546 s->selectee = evacuate(s->selectee);
2547 p += THUNK_SELECTOR_sizeW();
2551 // A chunk of stack saved in a heap object
2554 StgAP_STACK *ap = (StgAP_STACK *)p;
2556 ap->fun = evacuate(ap->fun);
2557 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2558 p = (StgPtr)ap->payload + ap->size;
2564 p = scavenge_PAP((StgPAP *)p);
2568 // nothing to follow
2569 p += arr_words_sizeW((StgArrWords *)p);
2573 // follow everything
2577 evac_gen = 0; // repeatedly mutable
2578 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2579 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2580 (StgClosure *)*p = evacuate((StgClosure *)*p);
2582 evac_gen = saved_evac_gen;
2583 recordMutable((StgMutClosure *)q);
2584 failed_to_evac = rtsFalse; // mutable anyhow.
2588 case MUT_ARR_PTRS_FROZEN:
2589 // follow everything
2593 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2594 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2595 (StgClosure *)*p = evacuate((StgClosure *)*p);
2597 // it's tempting to recordMutable() if failed_to_evac is
2598 // false, but that breaks some assumptions (eg. every
2599 // closure on the mutable list is supposed to have the MUT
2600 // flag set, and MUT_ARR_PTRS_FROZEN doesn't).
2606 StgTSO *tso = (StgTSO *)p;
2609 evac_gen = saved_evac_gen;
2610 recordMutable((StgMutClosure *)tso);
2611 failed_to_evac = rtsFalse; // mutable anyhow.
2612 p += tso_sizeW(tso);
2617 case RBH: // cf. BLACKHOLE_BQ
2620 nat size, ptrs, nonptrs, vhs;
2622 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2624 StgRBH *rbh = (StgRBH *)p;
2625 (StgClosure *)rbh->blocking_queue =
2626 evacuate((StgClosure *)rbh->blocking_queue);
2627 recordMutable((StgMutClosure *)to);
2628 failed_to_evac = rtsFalse; // mutable anyhow.
2630 belch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2631 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2632 // ToDo: use size of reverted closure here!
2633 p += BLACKHOLE_sizeW();
2639 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2640 // follow the pointer to the node which is being demanded
2641 (StgClosure *)bf->node =
2642 evacuate((StgClosure *)bf->node);
2643 // follow the link to the rest of the blocking queue
2644 (StgClosure *)bf->link =
2645 evacuate((StgClosure *)bf->link);
2646 if (failed_to_evac) {
2647 failed_to_evac = rtsFalse;
2648 recordMutable((StgMutClosure *)bf);
2651 belch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
2652 bf, info_type((StgClosure *)bf),
2653 bf->node, info_type(bf->node)));
2654 p += sizeofW(StgBlockedFetch);
2662 p += sizeofW(StgFetchMe);
2663 break; // nothing to do in this case
2665 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
2667 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
2668 (StgClosure *)fmbq->blocking_queue =
2669 evacuate((StgClosure *)fmbq->blocking_queue);
2670 if (failed_to_evac) {
2671 failed_to_evac = rtsFalse;
2672 recordMutable((StgMutClosure *)fmbq);
2675 belch("@@ scavenge: %p (%s) exciting, isn't it",
2676 p, info_type((StgClosure *)p)));
2677 p += sizeofW(StgFetchMeBlockingQueue);
2683 barf("scavenge: unimplemented/strange closure type %d @ %p",
2687 /* If we didn't manage to promote all the objects pointed to by
2688 * the current object, then we have to designate this object as
2689 * mutable (because it contains old-to-new generation pointers).
2691 if (failed_to_evac) {
2692 failed_to_evac = rtsFalse;
2693 mkMutCons((StgClosure *)q, &generations[evac_gen]);
2701 /* -----------------------------------------------------------------------------
2702 Scavenge everything on the mark stack.
2704 This is slightly different from scavenge():
2705 - we don't walk linearly through the objects, so the scavenger
2706 doesn't need to advance the pointer on to the next object.
2707 -------------------------------------------------------------------------- */
2710 scavenge_mark_stack(void)
2716 evac_gen = oldest_gen->no;
2717 saved_evac_gen = evac_gen;
2720 while (!mark_stack_empty()) {
2721 p = pop_mark_stack();
2723 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2724 info = get_itbl((StgClosure *)p);
2727 switch (info->type) {
2730 /* treat MVars specially, because we don't want to evacuate the
2731 * mut_link field in the middle of the closure.
2734 StgMVar *mvar = ((StgMVar *)p);
2736 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
2737 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
2738 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
2739 evac_gen = saved_evac_gen;
2740 failed_to_evac = rtsFalse; // mutable.
2745 scavenge_fun_srt(info);
2746 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2747 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2751 scavenge_thunk_srt(info);
2753 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2754 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2759 scavenge_fun_srt(info);
2760 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2765 scavenge_thunk_srt(info);
2768 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2773 scavenge_fun_srt(info);
2778 scavenge_thunk_srt(info);
2786 scavenge_fun_srt(info);
2790 scavenge_thunk_srt(info);
2801 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2802 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2803 (StgClosure *)*p = evacuate((StgClosure *)*p);
2809 StgBCO *bco = (StgBCO *)p;
2810 (StgClosure *)bco->instrs = evacuate((StgClosure *)bco->instrs);
2811 (StgClosure *)bco->literals = evacuate((StgClosure *)bco->literals);
2812 (StgClosure *)bco->ptrs = evacuate((StgClosure *)bco->ptrs);
2813 (StgClosure *)bco->itbls = evacuate((StgClosure *)bco->itbls);
2818 // don't need to do anything here: the only possible case
2819 // is that we're in a 1-space compacting collector, with
2820 // no "old" generation.
2824 case IND_OLDGEN_PERM:
2825 ((StgIndOldGen *)p)->indirectee =
2826 evacuate(((StgIndOldGen *)p)->indirectee);
2827 if (failed_to_evac) {
2828 recordOldToNewPtrs((StgMutClosure *)p);
2830 failed_to_evac = rtsFalse;
2835 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2836 evac_gen = saved_evac_gen;
2837 failed_to_evac = rtsFalse;
2842 failed_to_evac = rtsFalse;
2846 case SE_CAF_BLACKHOLE:
2854 StgBlockingQueue *bh = (StgBlockingQueue *)p;
2855 (StgClosure *)bh->blocking_queue =
2856 evacuate((StgClosure *)bh->blocking_queue);
2857 failed_to_evac = rtsFalse;
2861 case THUNK_SELECTOR:
2863 StgSelector *s = (StgSelector *)p;
2864 s->selectee = evacuate(s->selectee);
2868 // A chunk of stack saved in a heap object
2871 StgAP_STACK *ap = (StgAP_STACK *)p;
2873 ap->fun = evacuate(ap->fun);
2874 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2880 scavenge_PAP((StgPAP *)p);
2884 // follow everything
2888 evac_gen = 0; // repeatedly mutable
2889 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2890 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2891 (StgClosure *)*p = evacuate((StgClosure *)*p);
2893 evac_gen = saved_evac_gen;
2894 failed_to_evac = rtsFalse; // mutable anyhow.
2898 case MUT_ARR_PTRS_FROZEN:
2899 // follow everything
2903 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2904 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2905 (StgClosure *)*p = evacuate((StgClosure *)*p);
2912 StgTSO *tso = (StgTSO *)p;
2915 evac_gen = saved_evac_gen;
2916 failed_to_evac = rtsFalse;
2921 case RBH: // cf. BLACKHOLE_BQ
2924 nat size, ptrs, nonptrs, vhs;
2926 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2928 StgRBH *rbh = (StgRBH *)p;
2929 (StgClosure *)rbh->blocking_queue =
2930 evacuate((StgClosure *)rbh->blocking_queue);
2931 recordMutable((StgMutClosure *)rbh);
2932 failed_to_evac = rtsFalse; // mutable anyhow.
2934 belch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2935 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2941 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2942 // follow the pointer to the node which is being demanded
2943 (StgClosure *)bf->node =
2944 evacuate((StgClosure *)bf->node);
2945 // follow the link to the rest of the blocking queue
2946 (StgClosure *)bf->link =
2947 evacuate((StgClosure *)bf->link);
2948 if (failed_to_evac) {
2949 failed_to_evac = rtsFalse;
2950 recordMutable((StgMutClosure *)bf);
2953 belch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
2954 bf, info_type((StgClosure *)bf),
2955 bf->node, info_type(bf->node)));
2963 break; // nothing to do in this case
2965 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
2967 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
2968 (StgClosure *)fmbq->blocking_queue =
2969 evacuate((StgClosure *)fmbq->blocking_queue);
2970 if (failed_to_evac) {
2971 failed_to_evac = rtsFalse;
2972 recordMutable((StgMutClosure *)fmbq);
2975 belch("@@ scavenge: %p (%s) exciting, isn't it",
2976 p, info_type((StgClosure *)p)));
2982 barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p",
2986 if (failed_to_evac) {
2987 failed_to_evac = rtsFalse;
2988 mkMutCons((StgClosure *)q, &generations[evac_gen]);
2991 // mark the next bit to indicate "scavenged"
2992 mark(q+1, Bdescr(q));
2994 } // while (!mark_stack_empty())
2996 // start a new linear scan if the mark stack overflowed at some point
2997 if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
2998 IF_DEBUG(gc, belch("scavenge_mark_stack: starting linear scan"));
2999 mark_stack_overflowed = rtsFalse;
3000 oldgen_scan_bd = oldest_gen->steps[0].blocks;
3001 oldgen_scan = oldgen_scan_bd->start;
3004 if (oldgen_scan_bd) {
3005 // push a new thing on the mark stack
3007 // find a closure that is marked but not scavenged, and start
3009 while (oldgen_scan < oldgen_scan_bd->free
3010 && !is_marked(oldgen_scan,oldgen_scan_bd)) {
3014 if (oldgen_scan < oldgen_scan_bd->free) {
3016 // already scavenged?
3017 if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
3018 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3021 push_mark_stack(oldgen_scan);
3022 // ToDo: bump the linear scan by the actual size of the object
3023 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3027 oldgen_scan_bd = oldgen_scan_bd->link;
3028 if (oldgen_scan_bd != NULL) {
3029 oldgen_scan = oldgen_scan_bd->start;
3035 /* -----------------------------------------------------------------------------
3036 Scavenge one object.
3038 This is used for objects that are temporarily marked as mutable
3039 because they contain old-to-new generation pointers. Only certain
3040 objects can have this property.
3041 -------------------------------------------------------------------------- */
3044 scavenge_one(StgPtr p)
3046 const StgInfoTable *info;
3047 nat saved_evac_gen = evac_gen;
3050 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3051 info = get_itbl((StgClosure *)p);
3053 switch (info->type) {
3056 case FUN_1_0: // hardly worth specialising these guys
3076 case IND_OLDGEN_PERM:
3080 end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3081 for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
3082 (StgClosure *)*q = evacuate((StgClosure *)*q);
3088 case SE_CAF_BLACKHOLE:
3093 case THUNK_SELECTOR:
3095 StgSelector *s = (StgSelector *)p;
3096 s->selectee = evacuate(s->selectee);
3101 // nothing to follow
3106 // follow everything
3109 evac_gen = 0; // repeatedly mutable
3110 recordMutable((StgMutClosure *)p);
3111 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3112 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3113 (StgClosure *)*p = evacuate((StgClosure *)*p);
3115 evac_gen = saved_evac_gen;
3116 failed_to_evac = rtsFalse;
3120 case MUT_ARR_PTRS_FROZEN:
3122 // follow everything
3125 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3126 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3127 (StgClosure *)*p = evacuate((StgClosure *)*p);
3134 StgTSO *tso = (StgTSO *)p;
3136 evac_gen = 0; // repeatedly mutable
3138 recordMutable((StgMutClosure *)tso);
3139 evac_gen = saved_evac_gen;
3140 failed_to_evac = rtsFalse;
3146 StgAP_STACK *ap = (StgAP_STACK *)p;
3148 ap->fun = evacuate(ap->fun);
3149 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3150 p = (StgPtr)ap->payload + ap->size;
3156 p = scavenge_PAP((StgPAP *)p);
3160 // This might happen if for instance a MUT_CONS was pointing to a
3161 // THUNK which has since been updated. The IND_OLDGEN will
3162 // be on the mutable list anyway, so we don't need to do anything
3167 barf("scavenge_one: strange object %d", (int)(info->type));
3170 no_luck = failed_to_evac;
3171 failed_to_evac = rtsFalse;
3175 /* -----------------------------------------------------------------------------
3176 Scavenging mutable lists.
3178 We treat the mutable list of each generation > N (i.e. all the
3179 generations older than the one being collected) as roots. We also
3180 remove non-mutable objects from the mutable list at this point.
3181 -------------------------------------------------------------------------- */
3184 scavenge_mut_once_list(generation *gen)
3186 const StgInfoTable *info;
3187 StgMutClosure *p, *next, *new_list;
3189 p = gen->mut_once_list;
3190 new_list = END_MUT_LIST;
3194 failed_to_evac = rtsFalse;
3196 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
3198 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3201 if (info->type==RBH)
3202 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3204 switch(info->type) {
3207 case IND_OLDGEN_PERM:
3209 /* Try to pull the indirectee into this generation, so we can
3210 * remove the indirection from the mutable list.
3212 ((StgIndOldGen *)p)->indirectee =
3213 evacuate(((StgIndOldGen *)p)->indirectee);
3215 #if 0 && defined(DEBUG)
3216 if (RtsFlags.DebugFlags.gc)
3217 /* Debugging code to print out the size of the thing we just
3221 StgPtr start = gen->steps[0].scan;
3222 bdescr *start_bd = gen->steps[0].scan_bd;
3224 scavenge(&gen->steps[0]);
3225 if (start_bd != gen->steps[0].scan_bd) {
3226 size += (P_)BLOCK_ROUND_UP(start) - start;
3227 start_bd = start_bd->link;
3228 while (start_bd != gen->steps[0].scan_bd) {
3229 size += BLOCK_SIZE_W;
3230 start_bd = start_bd->link;
3232 size += gen->steps[0].scan -
3233 (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
3235 size = gen->steps[0].scan - start;
3237 belch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
3241 /* failed_to_evac might happen if we've got more than two
3242 * generations, we're collecting only generation 0, the
3243 * indirection resides in generation 2 and the indirectee is
3246 if (failed_to_evac) {
3247 failed_to_evac = rtsFalse;
3248 p->mut_link = new_list;
3251 /* the mut_link field of an IND_STATIC is overloaded as the
3252 * static link field too (it just so happens that we don't need
3253 * both at the same time), so we need to NULL it out when
3254 * removing this object from the mutable list because the static
3255 * link fields are all assumed to be NULL before doing a major
3263 /* MUT_CONS is a kind of MUT_VAR, except it that we try to remove
3264 * it from the mutable list if possible by promoting whatever it
3267 if (scavenge_one((StgPtr)((StgMutVar *)p)->var)) {
3268 /* didn't manage to promote everything, so put the
3269 * MUT_CONS back on the list.
3271 p->mut_link = new_list;
3277 // shouldn't have anything else on the mutables list
3278 barf("scavenge_mut_once_list: strange object? %d", (int)(info->type));
3282 gen->mut_once_list = new_list;
3287 scavenge_mutable_list(generation *gen)
3289 const StgInfoTable *info;
3290 StgMutClosure *p, *next;
3292 p = gen->saved_mut_list;
3296 failed_to_evac = rtsFalse;
3298 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
3300 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3303 if (info->type==RBH)
3304 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3306 switch(info->type) {
3309 // follow everything
3310 p->mut_link = gen->mut_list;
3315 end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3316 for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
3317 (StgClosure *)*q = evacuate((StgClosure *)*q);
3322 // Happens if a MUT_ARR_PTRS in the old generation is frozen
3323 case MUT_ARR_PTRS_FROZEN:
3328 end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3329 for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
3330 (StgClosure *)*q = evacuate((StgClosure *)*q);
3334 if (failed_to_evac) {
3335 failed_to_evac = rtsFalse;
3336 mkMutCons((StgClosure *)p, gen);
3342 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3343 p->mut_link = gen->mut_list;
3349 StgMVar *mvar = (StgMVar *)p;
3350 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
3351 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
3352 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
3353 p->mut_link = gen->mut_list;
3360 StgTSO *tso = (StgTSO *)p;
3364 /* Don't take this TSO off the mutable list - it might still
3365 * point to some younger objects (because we set evac_gen to 0
3368 tso->mut_link = gen->mut_list;
3369 gen->mut_list = (StgMutClosure *)tso;
3375 StgBlockingQueue *bh = (StgBlockingQueue *)p;
3376 (StgClosure *)bh->blocking_queue =
3377 evacuate((StgClosure *)bh->blocking_queue);
3378 p->mut_link = gen->mut_list;
3383 /* Happens if a BLACKHOLE_BQ in the old generation is updated:
3386 case IND_OLDGEN_PERM:
3387 /* Try to pull the indirectee into this generation, so we can
3388 * remove the indirection from the mutable list.
3391 ((StgIndOldGen *)p)->indirectee =
3392 evacuate(((StgIndOldGen *)p)->indirectee);
3395 if (failed_to_evac) {
3396 failed_to_evac = rtsFalse;
3397 p->mut_link = gen->mut_once_list;
3398 gen->mut_once_list = p;
3405 // HWL: check whether all of these are necessary
3407 case RBH: // cf. BLACKHOLE_BQ
3409 // nat size, ptrs, nonptrs, vhs;
3411 // StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3412 StgRBH *rbh = (StgRBH *)p;
3413 (StgClosure *)rbh->blocking_queue =
3414 evacuate((StgClosure *)rbh->blocking_queue);
3415 if (failed_to_evac) {
3416 failed_to_evac = rtsFalse;
3417 recordMutable((StgMutClosure *)rbh);
3419 // ToDo: use size of reverted closure here!
3420 p += BLACKHOLE_sizeW();
3426 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3427 // follow the pointer to the node which is being demanded
3428 (StgClosure *)bf->node =
3429 evacuate((StgClosure *)bf->node);
3430 // follow the link to the rest of the blocking queue
3431 (StgClosure *)bf->link =
3432 evacuate((StgClosure *)bf->link);
3433 if (failed_to_evac) {
3434 failed_to_evac = rtsFalse;
3435 recordMutable((StgMutClosure *)bf);
3437 p += sizeofW(StgBlockedFetch);
3443 barf("scavenge_mutable_list: REMOTE_REF %d", (int)(info->type));
3446 p += sizeofW(StgFetchMe);
3447 break; // nothing to do in this case
3449 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
3451 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3452 (StgClosure *)fmbq->blocking_queue =
3453 evacuate((StgClosure *)fmbq->blocking_queue);
3454 if (failed_to_evac) {
3455 failed_to_evac = rtsFalse;
3456 recordMutable((StgMutClosure *)fmbq);
3458 p += sizeofW(StgFetchMeBlockingQueue);
3464 // shouldn't have anything else on the mutables list
3465 barf("scavenge_mutable_list: strange object? %d", (int)(info->type));
3472 scavenge_static(void)
3474 StgClosure* p = static_objects;
3475 const StgInfoTable *info;
3477 /* Always evacuate straight to the oldest generation for static
3479 evac_gen = oldest_gen->no;
3481 /* keep going until we've scavenged all the objects on the linked
3483 while (p != END_OF_STATIC_LIST) {
3485 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3488 if (info->type==RBH)
3489 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3491 // make sure the info pointer is into text space
3493 /* Take this object *off* the static_objects list,
3494 * and put it on the scavenged_static_objects list.
3496 static_objects = STATIC_LINK(info,p);
3497 STATIC_LINK(info,p) = scavenged_static_objects;
3498 scavenged_static_objects = p;
3500 switch (info -> type) {
3504 StgInd *ind = (StgInd *)p;
3505 ind->indirectee = evacuate(ind->indirectee);
3507 /* might fail to evacuate it, in which case we have to pop it
3508 * back on the mutable list (and take it off the
3509 * scavenged_static list because the static link and mut link
3510 * pointers are one and the same).
3512 if (failed_to_evac) {
3513 failed_to_evac = rtsFalse;
3514 scavenged_static_objects = IND_STATIC_LINK(p);
3515 ((StgMutClosure *)ind)->mut_link = oldest_gen->mut_once_list;
3516 oldest_gen->mut_once_list = (StgMutClosure *)ind;
3522 scavenge_thunk_srt(info);
3526 scavenge_fun_srt(info);
3533 next = (P_)p->payload + info->layout.payload.ptrs;
3534 // evacuate the pointers
3535 for (q = (P_)p->payload; q < next; q++) {
3536 (StgClosure *)*q = evacuate((StgClosure *)*q);
3542 barf("scavenge_static: strange closure %d", (int)(info->type));
3545 ASSERT(failed_to_evac == rtsFalse);
3547 /* get the next static object from the list. Remember, there might
3548 * be more stuff on this list now that we've done some evacuating!
3549 * (static_objects is a global)
3555 /* -----------------------------------------------------------------------------
3556 scavenge a chunk of memory described by a bitmap
3557 -------------------------------------------------------------------------- */
3560 scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
3566 bitmap = large_bitmap->bitmap[b];
3567 for (i = 0; i < size; ) {
3568 if ((bitmap & 1) == 0) {
3569 (StgClosure *)*p = evacuate((StgClosure *)*p);
3573 if (i % BITS_IN(W_) == 0) {
3575 bitmap = large_bitmap->bitmap[b];
3577 bitmap = bitmap >> 1;
3582 static inline StgPtr
3583 scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap)
3586 if ((bitmap & 1) == 0) {
3587 (StgClosure *)*p = evacuate((StgClosure *)*p);
3590 bitmap = bitmap >> 1;
3596 /* -----------------------------------------------------------------------------
3597 scavenge_stack walks over a section of stack and evacuates all the
3598 objects pointed to by it. We can use the same code for walking
3599 AP_STACK_UPDs, since these are just sections of copied stack.
3600 -------------------------------------------------------------------------- */
3604 scavenge_stack(StgPtr p, StgPtr stack_end)
3606 const StgRetInfoTable* info;
3610 //IF_DEBUG(sanity, belch(" scavenging stack between %p and %p", p, stack_end));
3613 * Each time around this loop, we are looking at a chunk of stack
3614 * that starts with an activation record.
3617 while (p < stack_end) {
3618 info = get_ret_itbl((StgClosure *)p);
3620 switch (info->i.type) {
3623 ((StgUpdateFrame *)p)->updatee
3624 = evacuate(((StgUpdateFrame *)p)->updatee);
3625 p += sizeofW(StgUpdateFrame);
3628 // small bitmap (< 32 entries, or 64 on a 64-bit machine)
3633 bitmap = BITMAP_BITS(info->i.layout.bitmap);
3634 size = BITMAP_SIZE(info->i.layout.bitmap);
3635 // NOTE: the payload starts immediately after the info-ptr, we
3636 // don't have an StgHeader in the same sense as a heap closure.
3638 p = scavenge_small_bitmap(p, size, bitmap);
3641 scavenge_srt((StgClosure **)info->srt, info->i.srt_len);
3649 (StgClosure *)*p = evacuate((StgClosure *)*p);
3652 size = BCO_BITMAP_SIZE(bco);
3653 scavenge_large_bitmap(p, BCO_BITMAP(bco), size);
3658 // large bitmap (> 32 entries, or > 64 on a 64-bit machine)
3664 size = info->i.layout.large_bitmap->size;
3666 scavenge_large_bitmap(p, info->i.layout.large_bitmap, size);
3668 // and don't forget to follow the SRT
3672 // Dynamic bitmap: the mask is stored on the stack, and
3673 // there are a number of non-pointers followed by a number
3674 // of pointers above the bitmapped area. (see StgMacros.h,
3679 dyn = ((StgRetDyn *)p)->liveness;
3681 // traverse the bitmap first
3682 bitmap = GET_LIVENESS(dyn);
3683 p = (P_)&((StgRetDyn *)p)->payload[0];
3684 size = RET_DYN_SIZE;
3685 p = scavenge_small_bitmap(p, size, bitmap);
3687 // skip over the non-ptr words
3688 p += GET_NONPTRS(dyn);
3690 // follow the ptr words
3691 for (size = GET_PTRS(dyn); size > 0; size--) {
3692 (StgClosure *)*p = evacuate((StgClosure *)*p);
3700 StgRetFun *ret_fun = (StgRetFun *)p;
3701 StgFunInfoTable *fun_info;
3703 ret_fun->fun = evacuate(ret_fun->fun);
3704 fun_info = get_fun_itbl(ret_fun->fun);
3705 p = scavenge_arg_block(fun_info, ret_fun->payload);
3710 barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->i.type));
3715 /*-----------------------------------------------------------------------------
3716 scavenge the large object list.
3718 evac_gen set by caller; similar games played with evac_gen as with
3719 scavenge() - see comment at the top of scavenge(). Most large
3720 objects are (repeatedly) mutable, so most of the time evac_gen will
3722 --------------------------------------------------------------------------- */
3725 scavenge_large(step *stp)
3730 bd = stp->new_large_objects;
3732 for (; bd != NULL; bd = stp->new_large_objects) {
3734 /* take this object *off* the large objects list and put it on
3735 * the scavenged large objects list. This is so that we can
3736 * treat new_large_objects as a stack and push new objects on
3737 * the front when evacuating.
3739 stp->new_large_objects = bd->link;
3740 dbl_link_onto(bd, &stp->scavenged_large_objects);
3742 // update the block count in this step.
3743 stp->n_scavenged_large_blocks += bd->blocks;
3746 if (scavenge_one(p)) {
3747 mkMutCons((StgClosure *)p, stp->gen);
3752 /* -----------------------------------------------------------------------------
3753 Initialising the static object & mutable lists
3754 -------------------------------------------------------------------------- */
3757 zero_static_object_list(StgClosure* first_static)
3761 const StgInfoTable *info;
3763 for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
3765 link = STATIC_LINK(info, p);
3766 STATIC_LINK(info,p) = NULL;
3770 /* This function is only needed because we share the mutable link
3771 * field with the static link field in an IND_STATIC, so we have to
3772 * zero the mut_link field before doing a major GC, which needs the
3773 * static link field.
3775 * It doesn't do any harm to zero all the mutable link fields on the
3780 zero_mutable_list( StgMutClosure *first )
3782 StgMutClosure *next, *c;
3784 for (c = first; c != END_MUT_LIST; c = next) {
3790 /* -----------------------------------------------------------------------------
3792 -------------------------------------------------------------------------- */
3799 for (c = (StgIndStatic *)caf_list; c != NULL;
3800 c = (StgIndStatic *)c->static_link)
3802 c->header.info = c->saved_info;
3803 c->saved_info = NULL;
3804 // could, but not necessary: c->static_link = NULL;
3810 markCAFs( evac_fn evac )
3814 for (c = (StgIndStatic *)caf_list; c != NULL;
3815 c = (StgIndStatic *)c->static_link)
3817 evac(&c->indirectee);
3821 /* -----------------------------------------------------------------------------
3822 Sanity code for CAF garbage collection.
3824 With DEBUG turned on, we manage a CAF list in addition to the SRT
3825 mechanism. After GC, we run down the CAF list and blackhole any
3826 CAFs which have been garbage collected. This means we get an error
3827 whenever the program tries to enter a garbage collected CAF.
3829 Any garbage collected CAFs are taken off the CAF list at the same
3831 -------------------------------------------------------------------------- */
3833 #if 0 && defined(DEBUG)
3840 const StgInfoTable *info;
3851 ASSERT(info->type == IND_STATIC);
3853 if (STATIC_LINK(info,p) == NULL) {
3854 IF_DEBUG(gccafs, belch("CAF gc'd at 0x%04lx", (long)p));
3856 SET_INFO(p,&stg_BLACKHOLE_info);
3857 p = STATIC_LINK2(info,p);
3861 pp = &STATIC_LINK2(info,p);
3868 // belch("%d CAFs live", i);
3873 /* -----------------------------------------------------------------------------
3876 Whenever a thread returns to the scheduler after possibly doing
3877 some work, we have to run down the stack and black-hole all the
3878 closures referred to by update frames.
3879 -------------------------------------------------------------------------- */
3882 threadLazyBlackHole(StgTSO *tso)
3885 StgRetInfoTable *info;
3886 StgBlockingQueue *bh;
3889 stack_end = &tso->stack[tso->stack_size];
3891 frame = (StgClosure *)tso->sp;
3894 info = get_ret_itbl(frame);
3896 switch (info->i.type) {
3899 bh = (StgBlockingQueue *)((StgUpdateFrame *)frame)->updatee;
3901 /* if the thunk is already blackholed, it means we've also
3902 * already blackholed the rest of the thunks on this stack,
3903 * so we can stop early.
3905 * The blackhole made for a CAF is a CAF_BLACKHOLE, so they
3906 * don't interfere with this optimisation.
3908 if (bh->header.info == &stg_BLACKHOLE_info) {
3912 if (bh->header.info != &stg_BLACKHOLE_BQ_info &&
3913 bh->header.info != &stg_CAF_BLACKHOLE_info) {
3914 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
3915 belch("Unexpected lazy BHing required at 0x%04x",(int)bh);
3919 // We pretend that bh is now dead.
3920 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
3922 SET_INFO(bh,&stg_BLACKHOLE_info);
3925 // We pretend that bh has just been created.
3926 LDV_recordCreate(bh);
3930 frame = (StgClosure *) ((StgUpdateFrame *)frame + 1);
3936 // normal stack frames; do nothing except advance the pointer
3938 (StgPtr)frame += stack_frame_sizeW(frame);
3944 /* -----------------------------------------------------------------------------
3947 * Code largely pinched from old RTS, then hacked to bits. We also do
3948 * lazy black holing here.
3950 * -------------------------------------------------------------------------- */
3952 struct stack_gap { StgWord gap_size; struct stack_gap *next_gap; };
3955 threadSqueezeStack(StgTSO *tso)
3958 rtsBool prev_was_update_frame;
3959 StgClosure *updatee = NULL;
3961 StgRetInfoTable *info;
3962 StgWord current_gap_size;
3963 struct stack_gap *gap;
3966 // Traverse the stack upwards, replacing adjacent update frames
3967 // with a single update frame and a "stack gap". A stack gap
3968 // contains two values: the size of the gap, and the distance
3969 // to the next gap (or the stack top).
3971 bottom = &(tso->stack[tso->stack_size]);
3975 ASSERT(frame < bottom);
3977 prev_was_update_frame = rtsFalse;
3978 current_gap_size = 0;
3979 gap = (struct stack_gap *) (tso->sp - sizeofW(StgUpdateFrame));
3981 while (frame < bottom) {
3983 info = get_ret_itbl((StgClosure *)frame);
3984 switch (info->i.type) {
3988 StgUpdateFrame *upd = (StgUpdateFrame *)frame;
3990 if (upd->updatee->header.info == &stg_BLACKHOLE_info) {
3992 // found a BLACKHOLE'd update frame; we've been here
3993 // before, in a previous GC, so just break out.
3995 // Mark the end of the gap, if we're in one.
3996 if (current_gap_size != 0) {
3997 gap = (struct stack_gap *)(frame-sizeofW(StgUpdateFrame));
4000 frame += sizeofW(StgUpdateFrame);
4001 goto done_traversing;
4004 if (prev_was_update_frame) {
4006 TICK_UPD_SQUEEZED();
4007 /* wasn't there something about update squeezing and ticky to be
4008 * sorted out? oh yes: we aren't counting each enter properly
4009 * in this case. See the log somewhere. KSW 1999-04-21
4011 * Check two things: that the two update frames don't point to
4012 * the same object, and that the updatee_bypass isn't already an
4013 * indirection. Both of these cases only happen when we're in a
4014 * block hole-style loop (and there are multiple update frames
4015 * on the stack pointing to the same closure), but they can both
4016 * screw us up if we don't check.
4018 if (upd->updatee != updatee && !closure_IND(upd->updatee)) {
4019 // this wakes the threads up
4020 UPD_IND_NOLOCK(upd->updatee, updatee);
4023 // now mark this update frame as a stack gap. The gap
4024 // marker resides in the bottom-most update frame of
4025 // the series of adjacent frames, and covers all the
4026 // frames in this series.
4027 current_gap_size += sizeofW(StgUpdateFrame);
4028 ((struct stack_gap *)frame)->gap_size = current_gap_size;
4029 ((struct stack_gap *)frame)->next_gap = gap;
4031 frame += sizeofW(StgUpdateFrame);
4035 // single update frame, or the topmost update frame in a series
4037 StgBlockingQueue *bh = (StgBlockingQueue *)upd->updatee;
4039 // Do lazy black-holing
4040 if (bh->header.info != &stg_BLACKHOLE_info &&
4041 bh->header.info != &stg_BLACKHOLE_BQ_info &&
4042 bh->header.info != &stg_CAF_BLACKHOLE_info) {
4043 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4044 belch("Unexpected lazy BHing required at 0x%04x",(int)bh);
4047 /* zero out the slop so that the sanity checker can tell
4048 * where the next closure is.
4051 StgInfoTable *bh_info = get_itbl(bh);
4052 nat np = bh_info->layout.payload.ptrs,
4053 nw = bh_info->layout.payload.nptrs, i;
4054 /* don't zero out slop for a THUNK_SELECTOR,
4055 * because its layout info is used for a
4056 * different purpose, and it's exactly the
4057 * same size as a BLACKHOLE in any case.
4059 if (bh_info->type != THUNK_SELECTOR) {
4060 for (i = np; i < np + nw; i++) {
4061 ((StgClosure *)bh)->payload[i] = 0;
4067 // We pretend that bh is now dead.
4068 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4070 // Todo: maybe use SET_HDR() and remove LDV_recordCreate()?
4071 SET_INFO(bh,&stg_BLACKHOLE_info);
4073 // We pretend that bh has just been created.
4074 LDV_recordCreate(bh);
4078 prev_was_update_frame = rtsTrue;
4079 updatee = upd->updatee;
4080 frame += sizeofW(StgUpdateFrame);
4086 prev_was_update_frame = rtsFalse;
4088 // we're not in a gap... check whether this is the end of a gap
4089 // (an update frame can't be the end of a gap).
4090 if (current_gap_size != 0) {
4091 gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
4093 current_gap_size = 0;
4095 frame += stack_frame_sizeW((StgClosure *)frame);
4102 // Now we have a stack with gaps in it, and we have to walk down
4103 // shoving the stack up to fill in the gaps. A diagram might
4107 // | ********* | <- sp
4111 // | stack_gap | <- gap | chunk_size
4113 // | ......... | <- gap_end v
4119 // 'sp' points the the current top-of-stack
4120 // 'gap' points to the stack_gap structure inside the gap
4121 // ***** indicates real stack data
4122 // ..... indicates gap
4123 // <empty> indicates unused
4127 void *gap_start, *next_gap_start, *gap_end;
4130 next_gap_start = (void *)gap + sizeof(StgUpdateFrame);
4131 sp = next_gap_start;
4133 while ((StgPtr)gap > tso->sp) {
4135 // we're working in *bytes* now...
4136 gap_start = next_gap_start;
4137 gap_end = gap_start - gap->gap_size * sizeof(W_);
4139 gap = gap->next_gap;
4140 next_gap_start = (void *)gap + sizeof(StgUpdateFrame);
4142 chunk_size = gap_end - next_gap_start;
4144 memmove(sp, next_gap_start, chunk_size);
4147 tso->sp = (StgPtr)sp;
4151 /* -----------------------------------------------------------------------------
4154 * We have to prepare for GC - this means doing lazy black holing
4155 * here. We also take the opportunity to do stack squeezing if it's
4157 * -------------------------------------------------------------------------- */
4159 threadPaused(StgTSO *tso)
4161 if ( RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue )
4162 threadSqueezeStack(tso); // does black holing too
4164 threadLazyBlackHole(tso);
4167 /* -----------------------------------------------------------------------------
4169 * -------------------------------------------------------------------------- */
4173 printMutOnceList(generation *gen)
4175 StgMutClosure *p, *next;
4177 p = gen->mut_once_list;
4180 fprintf(stderr, "@@ Mut once list %p: ", gen->mut_once_list);
4181 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
4182 fprintf(stderr, "%p (%s), ",
4183 p, info_type((StgClosure *)p));
4185 fputc('\n', stderr);
4189 printMutableList(generation *gen)
4191 StgMutClosure *p, *next;
4196 fprintf(stderr, "@@ Mutable list %p: ", gen->mut_list);
4197 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
4198 fprintf(stderr, "%p (%s), ",
4199 p, info_type((StgClosure *)p));
4201 fputc('\n', stderr);
4204 static inline rtsBool
4205 maybeLarge(StgClosure *closure)
4207 StgInfoTable *info = get_itbl(closure);
4209 /* closure types that may be found on the new_large_objects list;
4210 see scavenge_large */
4211 return (info->type == MUT_ARR_PTRS ||
4212 info->type == MUT_ARR_PTRS_FROZEN ||
4213 info->type == TSO ||
4214 info->type == ARR_WORDS);