1 /* -----------------------------------------------------------------------------
3 * (c) The GHC Team 1998-2003
5 * Generational garbage collector
7 * ---------------------------------------------------------------------------*/
9 #include "PosixSource.h"
15 #include "LdvProfile.h"
20 #include "BlockAlloc.h"
26 #include "ParTicky.h" // ToDo: move into Rts.h
27 #include "GCCompact.h"
29 #if defined(GRAN) || defined(PAR)
30 # include "GranSimRts.h"
31 # include "ParallelRts.h"
35 # include "ParallelDebug.h"
40 #if defined(RTS_GTK_FRONTPANEL)
41 #include "FrontPanel.h"
44 #include "RetainerProfile.h"
48 /* STATIC OBJECT LIST.
51 * We maintain a linked list of static objects that are still live.
52 * The requirements for this list are:
54 * - we need to scan the list while adding to it, in order to
55 * scavenge all the static objects (in the same way that
56 * breadth-first scavenging works for dynamic objects).
58 * - we need to be able to tell whether an object is already on
59 * the list, to break loops.
61 * Each static object has a "static link field", which we use for
62 * linking objects on to the list. We use a stack-type list, consing
63 * objects on the front as they are added (this means that the
64 * scavenge phase is depth-first, not breadth-first, but that
67 * A separate list is kept for objects that have been scavenged
68 * already - this is so that we can zero all the marks afterwards.
70 * An object is on the list if its static link field is non-zero; this
71 * means that we have to mark the end of the list with '1', not NULL.
73 * Extra notes for generational GC:
75 * Each generation has a static object list associated with it. When
76 * collecting generations up to N, we treat the static object lists
77 * from generations > N as roots.
79 * We build up a static object list while collecting generations 0..N,
80 * which is then appended to the static object list of generation N+1.
82 static StgClosure* static_objects; // live static objects
83 StgClosure* scavenged_static_objects; // static objects scavenged so far
85 /* N is the oldest generation being collected, where the generations
86 * are numbered starting at 0. A major GC (indicated by the major_gc
87 * flag) is when we're collecting all generations. We only attempt to
88 * deal with static objects and GC CAFs when doing a major GC.
91 static rtsBool major_gc;
93 /* Youngest generation that objects should be evacuated to in
94 * evacuate(). (Logically an argument to evacuate, but it's static
95 * a lot of the time so we optimise it into a global variable).
101 StgWeak *old_weak_ptr_list; // also pending finaliser list
103 /* Which stage of processing various kinds of weak pointer are we at?
104 * (see traverse_weak_ptr_list() below for discussion).
106 typedef enum { WeakPtrs, WeakThreads, WeakDone } WeakStage;
107 static WeakStage weak_stage;
109 /* List of all threads during GC
111 static StgTSO *old_all_threads;
112 StgTSO *resurrected_threads;
114 /* Flag indicating failure to evacuate an object to the desired
117 static rtsBool failed_to_evac;
119 /* Old to-space (used for two-space collector only)
121 static bdescr *old_to_blocks;
123 /* Data used for allocation area sizing.
125 static lnat new_blocks; // blocks allocated during this GC
126 static lnat g0s0_pcnt_kept = 30; // percentage of g0s0 live at last minor GC
128 /* Used to avoid long recursion due to selector thunks
130 static lnat thunk_selector_depth = 0;
131 #define MAX_THUNK_SELECTOR_DEPTH 8
133 /* -----------------------------------------------------------------------------
134 Static function declarations
135 -------------------------------------------------------------------------- */
137 static bdescr * gc_alloc_block ( step *stp );
138 static void mark_root ( StgClosure **root );
140 // Use a register argument for evacuate, if available.
142 #define REGPARM1 __attribute__((regparm(1)))
147 REGPARM1 static StgClosure * evacuate (StgClosure *q);
149 static void zero_static_object_list ( StgClosure* first_static );
150 static void zero_mutable_list ( StgMutClosure *first );
152 static rtsBool traverse_weak_ptr_list ( void );
153 static void mark_weak_ptr_list ( StgWeak **list );
155 static StgClosure * eval_thunk_selector ( nat field, StgSelector * p );
158 static void scavenge ( step * );
159 static void scavenge_mark_stack ( void );
160 static void scavenge_stack ( StgPtr p, StgPtr stack_end );
161 static rtsBool scavenge_one ( StgPtr p );
162 static void scavenge_large ( step * );
163 static void scavenge_static ( void );
164 static void scavenge_mutable_list ( generation *g );
165 static void scavenge_mut_once_list ( generation *g );
167 static void scavenge_large_bitmap ( StgPtr p,
168 StgLargeBitmap *large_bitmap,
171 #if 0 && defined(DEBUG)
172 static void gcCAFs ( void );
175 /* -----------------------------------------------------------------------------
176 inline functions etc. for dealing with the mark bitmap & stack.
177 -------------------------------------------------------------------------- */
179 #define MARK_STACK_BLOCKS 4
181 static bdescr *mark_stack_bdescr;
182 static StgPtr *mark_stack;
183 static StgPtr *mark_sp;
184 static StgPtr *mark_splim;
186 // Flag and pointers used for falling back to a linear scan when the
187 // mark stack overflows.
188 static rtsBool mark_stack_overflowed;
189 static bdescr *oldgen_scan_bd;
190 static StgPtr oldgen_scan;
192 STATIC_INLINE rtsBool
193 mark_stack_empty(void)
195 return mark_sp == mark_stack;
198 STATIC_INLINE rtsBool
199 mark_stack_full(void)
201 return mark_sp >= mark_splim;
205 reset_mark_stack(void)
207 mark_sp = mark_stack;
211 push_mark_stack(StgPtr p)
222 /* -----------------------------------------------------------------------------
223 Allocate a new to-space block in the given step.
224 -------------------------------------------------------------------------- */
227 gc_alloc_block(step *stp)
229 bdescr *bd = allocBlock();
230 bd->gen_no = stp->gen_no;
234 // blocks in to-space in generations up to and including N
235 // get the BF_EVACUATED flag.
236 if (stp->gen_no <= N) {
237 bd->flags = BF_EVACUATED;
242 // Start a new to-space block, chain it on after the previous one.
243 if (stp->hp_bd == NULL) {
246 stp->hp_bd->free = stp->hp;
247 stp->hp_bd->link = bd;
252 stp->hpLim = stp->hp + BLOCK_SIZE_W;
260 /* -----------------------------------------------------------------------------
263 Rough outline of the algorithm: for garbage collecting generation N
264 (and all younger generations):
266 - follow all pointers in the root set. the root set includes all
267 mutable objects in all generations (mutable_list and mut_once_list).
269 - for each pointer, evacuate the object it points to into either
271 + to-space of the step given by step->to, which is the next
272 highest step in this generation or the first step in the next
273 generation if this is the last step.
275 + to-space of generations[evac_gen]->steps[0], if evac_gen != 0.
276 When we evacuate an object we attempt to evacuate
277 everything it points to into the same generation - this is
278 achieved by setting evac_gen to the desired generation. If
279 we can't do this, then an entry in the mut_once list has to
280 be made for the cross-generation pointer.
282 + if the object is already in a generation > N, then leave
285 - repeatedly scavenge to-space from each step in each generation
286 being collected until no more objects can be evacuated.
288 - free from-space in each step, and set from-space = to-space.
290 Locks held: sched_mutex
292 -------------------------------------------------------------------------- */
295 GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc )
299 lnat live, allocated, collected = 0, copied = 0;
300 lnat oldgen_saved_blocks = 0;
304 CostCentreStack *prev_CCS;
307 #if defined(DEBUG) && defined(GRAN)
308 IF_DEBUG(gc, debugBelch("@@ Starting garbage collection at %ld (%lx)\n",
312 #if defined(RTS_USER_SIGNALS)
317 // tell the stats department that we've started a GC
320 // Init stats and print par specific (timing) info
321 PAR_TICKY_PAR_START();
323 // attribute any costs to CCS_GC
329 /* Approximate how much we allocated.
330 * Todo: only when generating stats?
332 allocated = calcAllocated();
334 /* Figure out which generation to collect
336 if (force_major_gc) {
337 N = RtsFlags.GcFlags.generations - 1;
341 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
342 if (generations[g].steps[0].n_blocks +
343 generations[g].steps[0].n_large_blocks
344 >= generations[g].max_blocks) {
348 major_gc = (N == RtsFlags.GcFlags.generations-1);
351 #ifdef RTS_GTK_FRONTPANEL
352 if (RtsFlags.GcFlags.frontpanel) {
353 updateFrontPanelBeforeGC(N);
357 // check stack sanity *before* GC (ToDo: check all threads)
359 // ToDo!: check sanity IF_DEBUG(sanity, checkTSOsSanity());
361 IF_DEBUG(sanity, checkFreeListSanity());
363 /* Initialise the static object lists
365 static_objects = END_OF_STATIC_LIST;
366 scavenged_static_objects = END_OF_STATIC_LIST;
368 /* zero the mutable list for the oldest generation (see comment by
369 * zero_mutable_list below).
372 zero_mutable_list(generations[RtsFlags.GcFlags.generations-1].mut_once_list);
375 /* Save the old to-space if we're doing a two-space collection
377 if (RtsFlags.GcFlags.generations == 1) {
378 old_to_blocks = g0s0->to_blocks;
379 g0s0->to_blocks = NULL;
380 g0s0->n_to_blocks = 0;
383 /* Keep a count of how many new blocks we allocated during this GC
384 * (used for resizing the allocation area, later).
388 // Initialise to-space in all the generations/steps that we're
391 for (g = 0; g <= N; g++) {
392 generations[g].mut_once_list = END_MUT_LIST;
393 generations[g].mut_list = END_MUT_LIST;
395 for (s = 0; s < generations[g].n_steps; s++) {
397 // generation 0, step 0 doesn't need to-space
398 if (g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1) {
402 stp = &generations[g].steps[s];
403 ASSERT(stp->gen_no == g);
405 // start a new to-space for this step.
408 stp->to_blocks = NULL;
410 // allocate the first to-space block; extra blocks will be
411 // chained on as necessary.
412 bd = gc_alloc_block(stp);
414 stp->scan = bd->start;
417 // initialise the large object queues.
418 stp->new_large_objects = NULL;
419 stp->scavenged_large_objects = NULL;
420 stp->n_scavenged_large_blocks = 0;
422 // mark the large objects as not evacuated yet
423 for (bd = stp->large_objects; bd; bd = bd->link) {
424 bd->flags &= ~BF_EVACUATED;
427 // for a compacted step, we need to allocate the bitmap
428 if (stp->is_compacted) {
429 nat bitmap_size; // in bytes
430 bdescr *bitmap_bdescr;
433 bitmap_size = stp->n_blocks * BLOCK_SIZE / (sizeof(W_)*BITS_PER_BYTE);
435 if (bitmap_size > 0) {
436 bitmap_bdescr = allocGroup((nat)BLOCK_ROUND_UP(bitmap_size)
438 stp->bitmap = bitmap_bdescr;
439 bitmap = bitmap_bdescr->start;
441 IF_DEBUG(gc, debugBelch("bitmap_size: %d, bitmap: %p",
442 bitmap_size, bitmap););
444 // don't forget to fill it with zeros!
445 memset(bitmap, 0, bitmap_size);
447 // For each block in this step, point to its bitmap from the
449 for (bd=stp->blocks; bd != NULL; bd = bd->link) {
450 bd->u.bitmap = bitmap;
451 bitmap += BLOCK_SIZE_W / (sizeof(W_)*BITS_PER_BYTE);
453 // Also at this point we set the BF_COMPACTED flag
454 // for this block. The invariant is that
455 // BF_COMPACTED is always unset, except during GC
456 // when it is set on those blocks which will be
458 bd->flags |= BF_COMPACTED;
465 /* make sure the older generations have at least one block to
466 * allocate into (this makes things easier for copy(), see below).
468 for (g = N+1; g < RtsFlags.GcFlags.generations; g++) {
469 for (s = 0; s < generations[g].n_steps; s++) {
470 stp = &generations[g].steps[s];
471 if (stp->hp_bd == NULL) {
472 ASSERT(stp->blocks == NULL);
473 bd = gc_alloc_block(stp);
477 /* Set the scan pointer for older generations: remember we
478 * still have to scavenge objects that have been promoted. */
480 stp->scan_bd = stp->hp_bd;
481 stp->to_blocks = NULL;
482 stp->n_to_blocks = 0;
483 stp->new_large_objects = NULL;
484 stp->scavenged_large_objects = NULL;
485 stp->n_scavenged_large_blocks = 0;
489 /* Allocate a mark stack if we're doing a major collection.
492 mark_stack_bdescr = allocGroup(MARK_STACK_BLOCKS);
493 mark_stack = (StgPtr *)mark_stack_bdescr->start;
494 mark_sp = mark_stack;
495 mark_splim = mark_stack + (MARK_STACK_BLOCKS * BLOCK_SIZE_W);
497 mark_stack_bdescr = NULL;
500 /* -----------------------------------------------------------------------
501 * follow all the roots that we know about:
502 * - mutable lists from each generation > N
503 * we want to *scavenge* these roots, not evacuate them: they're not
504 * going to move in this GC.
505 * Also: do them in reverse generation order. This is because we
506 * often want to promote objects that are pointed to by older
507 * generations early, so we don't have to repeatedly copy them.
508 * Doing the generations in reverse order ensures that we don't end
509 * up in the situation where we want to evac an object to gen 3 and
510 * it has already been evaced to gen 2.
514 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
515 generations[g].saved_mut_list = generations[g].mut_list;
516 generations[g].mut_list = END_MUT_LIST;
519 // Do the mut-once lists first
520 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
521 IF_PAR_DEBUG(verbose,
522 printMutOnceList(&generations[g]));
523 scavenge_mut_once_list(&generations[g]);
525 for (st = generations[g].n_steps-1; st >= 0; st--) {
526 scavenge(&generations[g].steps[st]);
530 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
531 IF_PAR_DEBUG(verbose,
532 printMutableList(&generations[g]));
533 scavenge_mutable_list(&generations[g]);
535 for (st = generations[g].n_steps-1; st >= 0; st--) {
536 scavenge(&generations[g].steps[st]);
541 /* follow roots from the CAF list (used by GHCi)
546 /* follow all the roots that the application knows about.
549 get_roots(mark_root);
552 /* And don't forget to mark the TSO if we got here direct from
554 /* Not needed in a seq version?
556 CurrentTSO = (StgTSO *)MarkRoot((StgClosure *)CurrentTSO);
560 // Mark the entries in the GALA table of the parallel system
561 markLocalGAs(major_gc);
562 // Mark all entries on the list of pending fetches
563 markPendingFetches(major_gc);
566 /* Mark the weak pointer list, and prepare to detect dead weak
569 mark_weak_ptr_list(&weak_ptr_list);
570 old_weak_ptr_list = weak_ptr_list;
571 weak_ptr_list = NULL;
572 weak_stage = WeakPtrs;
574 /* The all_threads list is like the weak_ptr_list.
575 * See traverse_weak_ptr_list() for the details.
577 old_all_threads = all_threads;
578 all_threads = END_TSO_QUEUE;
579 resurrected_threads = END_TSO_QUEUE;
581 /* Mark the stable pointer table.
583 markStablePtrTable(mark_root);
585 /* -------------------------------------------------------------------------
586 * Repeatedly scavenge all the areas we know about until there's no
587 * more scavenging to be done.
594 // scavenge static objects
595 if (major_gc && static_objects != END_OF_STATIC_LIST) {
596 IF_DEBUG(sanity, checkStaticObjects(static_objects));
600 /* When scavenging the older generations: Objects may have been
601 * evacuated from generations <= N into older generations, and we
602 * need to scavenge these objects. We're going to try to ensure that
603 * any evacuations that occur move the objects into at least the
604 * same generation as the object being scavenged, otherwise we
605 * have to create new entries on the mutable list for the older
609 // scavenge each step in generations 0..maxgen
615 // scavenge objects in compacted generation
616 if (mark_stack_overflowed || oldgen_scan_bd != NULL ||
617 (mark_stack_bdescr != NULL && !mark_stack_empty())) {
618 scavenge_mark_stack();
622 for (gen = RtsFlags.GcFlags.generations; --gen >= 0; ) {
623 for (st = generations[gen].n_steps; --st >= 0; ) {
624 if (gen == 0 && st == 0 && RtsFlags.GcFlags.generations > 1) {
627 stp = &generations[gen].steps[st];
629 if (stp->hp_bd != stp->scan_bd || stp->scan < stp->hp) {
634 if (stp->new_large_objects != NULL) {
643 if (flag) { goto loop; }
645 // must be last... invariant is that everything is fully
646 // scavenged at this point.
647 if (traverse_weak_ptr_list()) { // returns rtsTrue if evaced something
652 /* Update the pointers from the "main thread" list - these are
653 * treated as weak pointers because we want to allow a main thread
654 * to get a BlockedOnDeadMVar exception in the same way as any other
655 * thread. Note that the threads should all have been retained by
656 * GC by virtue of being on the all_threads list, we're just
657 * updating pointers here.
662 for (m = main_threads; m != NULL; m = m->link) {
663 tso = (StgTSO *) isAlive((StgClosure *)m->tso);
665 barf("main thread has been GC'd");
672 // Reconstruct the Global Address tables used in GUM
673 rebuildGAtables(major_gc);
674 IF_DEBUG(sanity, checkLAGAtable(rtsTrue/*check closures, too*/));
677 // Now see which stable names are still alive.
680 // Tidy the end of the to-space chains
681 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
682 for (s = 0; s < generations[g].n_steps; s++) {
683 stp = &generations[g].steps[s];
684 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
685 ASSERT(Bdescr(stp->hp) == stp->hp_bd);
686 stp->hp_bd->free = stp->hp;
692 // We call processHeapClosureForDead() on every closure destroyed during
693 // the current garbage collection, so we invoke LdvCensusForDead().
694 if (RtsFlags.ProfFlags.doHeapProfile == HEAP_BY_LDV
695 || RtsFlags.ProfFlags.bioSelector != NULL)
699 // NO MORE EVACUATION AFTER THIS POINT!
700 // Finally: compaction of the oldest generation.
701 if (major_gc && oldest_gen->steps[0].is_compacted) {
702 // save number of blocks for stats
703 oldgen_saved_blocks = oldest_gen->steps[0].n_blocks;
707 IF_DEBUG(sanity, checkGlobalTSOList(rtsFalse));
709 /* run through all the generations/steps and tidy up
711 copied = new_blocks * BLOCK_SIZE_W;
712 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
715 generations[g].collections++; // for stats
718 for (s = 0; s < generations[g].n_steps; s++) {
720 stp = &generations[g].steps[s];
722 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
723 // stats information: how much we copied
725 copied -= stp->hp_bd->start + BLOCK_SIZE_W -
730 // for generations we collected...
733 // rough calculation of garbage collected, for stats output
734 if (stp->is_compacted) {
735 collected += (oldgen_saved_blocks - stp->n_blocks) * BLOCK_SIZE_W;
737 collected += stp->n_blocks * BLOCK_SIZE_W;
740 /* free old memory and shift to-space into from-space for all
741 * the collected steps (except the allocation area). These
742 * freed blocks will probaby be quickly recycled.
744 if (!(g == 0 && s == 0)) {
745 if (stp->is_compacted) {
746 // for a compacted step, just shift the new to-space
747 // onto the front of the now-compacted existing blocks.
748 for (bd = stp->to_blocks; bd != NULL; bd = bd->link) {
749 bd->flags &= ~BF_EVACUATED; // now from-space
751 // tack the new blocks on the end of the existing blocks
752 if (stp->blocks == NULL) {
753 stp->blocks = stp->to_blocks;
755 for (bd = stp->blocks; bd != NULL; bd = next) {
758 bd->link = stp->to_blocks;
760 // NB. this step might not be compacted next
761 // time, so reset the BF_COMPACTED flags.
762 // They are set before GC if we're going to
763 // compact. (search for BF_COMPACTED above).
764 bd->flags &= ~BF_COMPACTED;
767 // add the new blocks to the block tally
768 stp->n_blocks += stp->n_to_blocks;
770 freeChain(stp->blocks);
771 stp->blocks = stp->to_blocks;
772 stp->n_blocks = stp->n_to_blocks;
773 for (bd = stp->blocks; bd != NULL; bd = bd->link) {
774 bd->flags &= ~BF_EVACUATED; // now from-space
777 stp->to_blocks = NULL;
778 stp->n_to_blocks = 0;
781 /* LARGE OBJECTS. The current live large objects are chained on
782 * scavenged_large, having been moved during garbage
783 * collection from large_objects. Any objects left on
784 * large_objects list are therefore dead, so we free them here.
786 for (bd = stp->large_objects; bd != NULL; bd = next) {
792 // update the count of blocks used by large objects
793 for (bd = stp->scavenged_large_objects; bd != NULL; bd = bd->link) {
794 bd->flags &= ~BF_EVACUATED;
796 stp->large_objects = stp->scavenged_large_objects;
797 stp->n_large_blocks = stp->n_scavenged_large_blocks;
800 // for older generations...
802 /* For older generations, we need to append the
803 * scavenged_large_object list (i.e. large objects that have been
804 * promoted during this GC) to the large_object list for that step.
806 for (bd = stp->scavenged_large_objects; bd; bd = next) {
808 bd->flags &= ~BF_EVACUATED;
809 dbl_link_onto(bd, &stp->large_objects);
812 // add the new blocks we promoted during this GC
813 stp->n_blocks += stp->n_to_blocks;
814 stp->n_to_blocks = 0;
815 stp->n_large_blocks += stp->n_scavenged_large_blocks;
820 /* Reset the sizes of the older generations when we do a major
823 * CURRENT STRATEGY: make all generations except zero the same size.
824 * We have to stay within the maximum heap size, and leave a certain
825 * percentage of the maximum heap size available to allocate into.
827 if (major_gc && RtsFlags.GcFlags.generations > 1) {
828 nat live, size, min_alloc;
829 nat max = RtsFlags.GcFlags.maxHeapSize;
830 nat gens = RtsFlags.GcFlags.generations;
832 // live in the oldest generations
833 live = oldest_gen->steps[0].n_blocks +
834 oldest_gen->steps[0].n_large_blocks;
836 // default max size for all generations except zero
837 size = stg_max(live * RtsFlags.GcFlags.oldGenFactor,
838 RtsFlags.GcFlags.minOldGenSize);
840 // minimum size for generation zero
841 min_alloc = stg_max((RtsFlags.GcFlags.pcFreeHeap * max) / 200,
842 RtsFlags.GcFlags.minAllocAreaSize);
844 // Auto-enable compaction when the residency reaches a
845 // certain percentage of the maximum heap size (default: 30%).
846 if (RtsFlags.GcFlags.generations > 1 &&
847 (RtsFlags.GcFlags.compact ||
849 oldest_gen->steps[0].n_blocks >
850 (RtsFlags.GcFlags.compactThreshold * max) / 100))) {
851 oldest_gen->steps[0].is_compacted = 1;
852 // debugBelch("compaction: on\n", live);
854 oldest_gen->steps[0].is_compacted = 0;
855 // debugBelch("compaction: off\n", live);
858 // if we're going to go over the maximum heap size, reduce the
859 // size of the generations accordingly. The calculation is
860 // different if compaction is turned on, because we don't need
861 // to double the space required to collect the old generation.
864 // this test is necessary to ensure that the calculations
865 // below don't have any negative results - we're working
866 // with unsigned values here.
867 if (max < min_alloc) {
871 if (oldest_gen->steps[0].is_compacted) {
872 if ( (size + (size - 1) * (gens - 2) * 2) + min_alloc > max ) {
873 size = (max - min_alloc) / ((gens - 1) * 2 - 1);
876 if ( (size * (gens - 1) * 2) + min_alloc > max ) {
877 size = (max - min_alloc) / ((gens - 1) * 2);
887 debugBelch("live: %d, min_alloc: %d, size : %d, max = %d\n", live,
888 min_alloc, size, max);
891 for (g = 0; g < gens; g++) {
892 generations[g].max_blocks = size;
896 // Guess the amount of live data for stats.
899 /* Free the small objects allocated via allocate(), since this will
900 * all have been copied into G0S1 now.
902 if (small_alloc_list != NULL) {
903 freeChain(small_alloc_list);
905 small_alloc_list = NULL;
909 alloc_blocks_lim = RtsFlags.GcFlags.minAllocAreaSize;
911 // Start a new pinned_object_block
912 pinned_object_block = NULL;
914 /* Free the mark stack.
916 if (mark_stack_bdescr != NULL) {
917 freeGroup(mark_stack_bdescr);
922 for (g = 0; g <= N; g++) {
923 for (s = 0; s < generations[g].n_steps; s++) {
924 stp = &generations[g].steps[s];
925 if (stp->is_compacted && stp->bitmap != NULL) {
926 freeGroup(stp->bitmap);
931 /* Two-space collector:
932 * Free the old to-space, and estimate the amount of live data.
934 if (RtsFlags.GcFlags.generations == 1) {
937 if (old_to_blocks != NULL) {
938 freeChain(old_to_blocks);
940 for (bd = g0s0->to_blocks; bd != NULL; bd = bd->link) {
941 bd->flags = 0; // now from-space
944 /* For a two-space collector, we need to resize the nursery. */
946 /* set up a new nursery. Allocate a nursery size based on a
947 * function of the amount of live data (by default a factor of 2)
948 * Use the blocks from the old nursery if possible, freeing up any
951 * If we get near the maximum heap size, then adjust our nursery
952 * size accordingly. If the nursery is the same size as the live
953 * data (L), then we need 3L bytes. We can reduce the size of the
954 * nursery to bring the required memory down near 2L bytes.
956 * A normal 2-space collector would need 4L bytes to give the same
957 * performance we get from 3L bytes, reducing to the same
958 * performance at 2L bytes.
960 blocks = g0s0->n_to_blocks;
962 if ( RtsFlags.GcFlags.maxHeapSize != 0 &&
963 blocks * RtsFlags.GcFlags.oldGenFactor * 2 >
964 RtsFlags.GcFlags.maxHeapSize ) {
965 long adjusted_blocks; // signed on purpose
968 adjusted_blocks = (RtsFlags.GcFlags.maxHeapSize - 2 * blocks);
969 IF_DEBUG(gc, debugBelch("@@ Near maximum heap size of 0x%x blocks, blocks = %d, adjusted to %ld", RtsFlags.GcFlags.maxHeapSize, blocks, adjusted_blocks));
970 pc_free = adjusted_blocks * 100 / RtsFlags.GcFlags.maxHeapSize;
971 if (pc_free < RtsFlags.GcFlags.pcFreeHeap) /* might even be < 0 */ {
974 blocks = adjusted_blocks;
977 blocks *= RtsFlags.GcFlags.oldGenFactor;
978 if (blocks < RtsFlags.GcFlags.minAllocAreaSize) {
979 blocks = RtsFlags.GcFlags.minAllocAreaSize;
982 resizeNursery(blocks);
985 /* Generational collector:
986 * If the user has given us a suggested heap size, adjust our
987 * allocation area to make best use of the memory available.
990 if (RtsFlags.GcFlags.heapSizeSuggestion) {
992 nat needed = calcNeeded(); // approx blocks needed at next GC
994 /* Guess how much will be live in generation 0 step 0 next time.
995 * A good approximation is obtained by finding the
996 * percentage of g0s0 that was live at the last minor GC.
999 g0s0_pcnt_kept = (new_blocks * 100) / g0s0->n_blocks;
1002 /* Estimate a size for the allocation area based on the
1003 * information available. We might end up going slightly under
1004 * or over the suggested heap size, but we should be pretty
1007 * Formula: suggested - needed
1008 * ----------------------------
1009 * 1 + g0s0_pcnt_kept/100
1011 * where 'needed' is the amount of memory needed at the next
1012 * collection for collecting all steps except g0s0.
1015 (((long)RtsFlags.GcFlags.heapSizeSuggestion - (long)needed) * 100) /
1016 (100 + (long)g0s0_pcnt_kept);
1018 if (blocks < (long)RtsFlags.GcFlags.minAllocAreaSize) {
1019 blocks = RtsFlags.GcFlags.minAllocAreaSize;
1022 resizeNursery((nat)blocks);
1025 // we might have added extra large blocks to the nursery, so
1026 // resize back to minAllocAreaSize again.
1027 resizeNursery(RtsFlags.GcFlags.minAllocAreaSize);
1031 // mark the garbage collected CAFs as dead
1032 #if 0 && defined(DEBUG) // doesn't work at the moment
1033 if (major_gc) { gcCAFs(); }
1037 // resetStaticObjectForRetainerProfiling() must be called before
1039 resetStaticObjectForRetainerProfiling();
1042 // zero the scavenged static object list
1044 zero_static_object_list(scavenged_static_objects);
1047 // Reset the nursery
1050 RELEASE_LOCK(&sched_mutex);
1052 // start any pending finalizers
1053 scheduleFinalizers(old_weak_ptr_list);
1055 // send exceptions to any threads which were about to die
1056 resurrectThreads(resurrected_threads);
1058 ACQUIRE_LOCK(&sched_mutex);
1060 // Update the stable pointer hash table.
1061 updateStablePtrTable(major_gc);
1063 // check sanity after GC
1064 IF_DEBUG(sanity, checkSanity());
1066 // extra GC trace info
1067 IF_DEBUG(gc, statDescribeGens());
1070 // symbol-table based profiling
1071 /* heapCensus(to_blocks); */ /* ToDo */
1074 // restore enclosing cost centre
1079 // check for memory leaks if sanity checking is on
1080 IF_DEBUG(sanity, memInventory());
1082 #ifdef RTS_GTK_FRONTPANEL
1083 if (RtsFlags.GcFlags.frontpanel) {
1084 updateFrontPanelAfterGC( N, live );
1088 // ok, GC over: tell the stats department what happened.
1089 stat_endGC(allocated, collected, live, copied, N);
1091 #if defined(RTS_USER_SIGNALS)
1092 // unblock signals again
1093 unblockUserSignals();
1100 /* -----------------------------------------------------------------------------
1103 traverse_weak_ptr_list is called possibly many times during garbage
1104 collection. It returns a flag indicating whether it did any work
1105 (i.e. called evacuate on any live pointers).
1107 Invariant: traverse_weak_ptr_list is called when the heap is in an
1108 idempotent state. That means that there are no pending
1109 evacuate/scavenge operations. This invariant helps the weak
1110 pointer code decide which weak pointers are dead - if there are no
1111 new live weak pointers, then all the currently unreachable ones are
1114 For generational GC: we just don't try to finalize weak pointers in
1115 older generations than the one we're collecting. This could
1116 probably be optimised by keeping per-generation lists of weak
1117 pointers, but for a few weak pointers this scheme will work.
1119 There are three distinct stages to processing weak pointers:
1121 - weak_stage == WeakPtrs
1123 We process all the weak pointers whos keys are alive (evacuate
1124 their values and finalizers), and repeat until we can find no new
1125 live keys. If no live keys are found in this pass, then we
1126 evacuate the finalizers of all the dead weak pointers in order to
1129 - weak_stage == WeakThreads
1131 Now, we discover which *threads* are still alive. Pointers to
1132 threads from the all_threads and main thread lists are the
1133 weakest of all: a pointers from the finalizer of a dead weak
1134 pointer can keep a thread alive. Any threads found to be unreachable
1135 are evacuated and placed on the resurrected_threads list so we
1136 can send them a signal later.
1138 - weak_stage == WeakDone
1140 No more evacuation is done.
1142 -------------------------------------------------------------------------- */
1145 traverse_weak_ptr_list(void)
1147 StgWeak *w, **last_w, *next_w;
1149 rtsBool flag = rtsFalse;
1151 switch (weak_stage) {
1157 /* doesn't matter where we evacuate values/finalizers to, since
1158 * these pointers are treated as roots (iff the keys are alive).
1162 last_w = &old_weak_ptr_list;
1163 for (w = old_weak_ptr_list; w != NULL; w = next_w) {
1165 /* There might be a DEAD_WEAK on the list if finalizeWeak# was
1166 * called on a live weak pointer object. Just remove it.
1168 if (w->header.info == &stg_DEAD_WEAK_info) {
1169 next_w = ((StgDeadWeak *)w)->link;
1174 switch (get_itbl(w)->type) {
1177 next_w = (StgWeak *)((StgEvacuated *)w)->evacuee;
1182 /* Now, check whether the key is reachable.
1184 new = isAlive(w->key);
1187 // evacuate the value and finalizer
1188 w->value = evacuate(w->value);
1189 w->finalizer = evacuate(w->finalizer);
1190 // remove this weak ptr from the old_weak_ptr list
1192 // and put it on the new weak ptr list
1194 w->link = weak_ptr_list;
1197 IF_DEBUG(weak, debugBelch("Weak pointer still alive at %p -> %p",
1202 last_w = &(w->link);
1208 barf("traverse_weak_ptr_list: not WEAK");
1212 /* If we didn't make any changes, then we can go round and kill all
1213 * the dead weak pointers. The old_weak_ptr list is used as a list
1214 * of pending finalizers later on.
1216 if (flag == rtsFalse) {
1217 for (w = old_weak_ptr_list; w; w = w->link) {
1218 w->finalizer = evacuate(w->finalizer);
1221 // Next, move to the WeakThreads stage after fully
1222 // scavenging the finalizers we've just evacuated.
1223 weak_stage = WeakThreads;
1229 /* Now deal with the all_threads list, which behaves somewhat like
1230 * the weak ptr list. If we discover any threads that are about to
1231 * become garbage, we wake them up and administer an exception.
1234 StgTSO *t, *tmp, *next, **prev;
1236 prev = &old_all_threads;
1237 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1239 (StgClosure *)tmp = isAlive((StgClosure *)t);
1245 ASSERT(get_itbl(t)->type == TSO);
1246 switch (t->what_next) {
1247 case ThreadRelocated:
1252 case ThreadComplete:
1253 // finshed or died. The thread might still be alive, but we
1254 // don't keep it on the all_threads list. Don't forget to
1255 // stub out its global_link field.
1256 next = t->global_link;
1257 t->global_link = END_TSO_QUEUE;
1265 // not alive (yet): leave this thread on the
1266 // old_all_threads list.
1267 prev = &(t->global_link);
1268 next = t->global_link;
1271 // alive: move this thread onto the all_threads list.
1272 next = t->global_link;
1273 t->global_link = all_threads;
1280 /* And resurrect any threads which were about to become garbage.
1283 StgTSO *t, *tmp, *next;
1284 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1285 next = t->global_link;
1286 (StgClosure *)tmp = evacuate((StgClosure *)t);
1287 tmp->global_link = resurrected_threads;
1288 resurrected_threads = tmp;
1292 weak_stage = WeakDone; // *now* we're done,
1293 return rtsTrue; // but one more round of scavenging, please
1296 barf("traverse_weak_ptr_list");
1302 /* -----------------------------------------------------------------------------
1303 After GC, the live weak pointer list may have forwarding pointers
1304 on it, because a weak pointer object was evacuated after being
1305 moved to the live weak pointer list. We remove those forwarding
1308 Also, we don't consider weak pointer objects to be reachable, but
1309 we must nevertheless consider them to be "live" and retain them.
1310 Therefore any weak pointer objects which haven't as yet been
1311 evacuated need to be evacuated now.
1312 -------------------------------------------------------------------------- */
1316 mark_weak_ptr_list ( StgWeak **list )
1318 StgWeak *w, **last_w;
1321 for (w = *list; w; w = w->link) {
1322 // w might be WEAK, EVACUATED, or DEAD_WEAK (actually CON_STATIC) here
1323 ASSERT(w->header.info == &stg_DEAD_WEAK_info
1324 || get_itbl(w)->type == WEAK || get_itbl(w)->type == EVACUATED);
1325 (StgClosure *)w = evacuate((StgClosure *)w);
1327 last_w = &(w->link);
1331 /* -----------------------------------------------------------------------------
1332 isAlive determines whether the given closure is still alive (after
1333 a garbage collection) or not. It returns the new address of the
1334 closure if it is alive, or NULL otherwise.
1336 NOTE: Use it before compaction only!
1337 -------------------------------------------------------------------------- */
1341 isAlive(StgClosure *p)
1343 const StgInfoTable *info;
1348 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
1351 // ignore static closures
1353 // ToDo: for static closures, check the static link field.
1354 // Problem here is that we sometimes don't set the link field, eg.
1355 // for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
1357 if (!HEAP_ALLOCED(p)) {
1361 // ignore closures in generations that we're not collecting.
1363 if (bd->gen_no > N) {
1367 // if it's a pointer into to-space, then we're done
1368 if (bd->flags & BF_EVACUATED) {
1372 // large objects use the evacuated flag
1373 if (bd->flags & BF_LARGE) {
1377 // check the mark bit for compacted steps
1378 if ((bd->flags & BF_COMPACTED) && is_marked((P_)p,bd)) {
1382 switch (info->type) {
1387 case IND_OLDGEN: // rely on compatible layout with StgInd
1388 case IND_OLDGEN_PERM:
1389 // follow indirections
1390 p = ((StgInd *)p)->indirectee;
1395 return ((StgEvacuated *)p)->evacuee;
1398 if (((StgTSO *)p)->what_next == ThreadRelocated) {
1399 p = (StgClosure *)((StgTSO *)p)->link;
1412 mark_root(StgClosure **root)
1414 *root = evacuate(*root);
1418 upd_evacuee(StgClosure *p, StgClosure *dest)
1420 // Source object must be in from-space:
1421 ASSERT((Bdescr((P_)p)->flags & BF_EVACUATED) == 0);
1422 // not true: (ToDo: perhaps it should be)
1423 // ASSERT(Bdescr((P_)dest)->flags & BF_EVACUATED);
1424 SET_INFO(p, &stg_EVACUATED_info);
1425 ((StgEvacuated *)p)->evacuee = dest;
1429 STATIC_INLINE StgClosure *
1430 copy(StgClosure *src, nat size, step *stp)
1435 nat size_org = size;
1438 TICK_GC_WORDS_COPIED(size);
1439 /* Find out where we're going, using the handy "to" pointer in
1440 * the step of the source object. If it turns out we need to
1441 * evacuate to an older generation, adjust it here (see comment
1444 if (stp->gen_no < evac_gen) {
1445 #ifdef NO_EAGER_PROMOTION
1446 failed_to_evac = rtsTrue;
1448 stp = &generations[evac_gen].steps[0];
1452 /* chain a new block onto the to-space for the destination step if
1455 if (stp->hp + size >= stp->hpLim) {
1456 gc_alloc_block(stp);
1459 for(to = stp->hp, from = (P_)src; size>0; --size) {
1465 upd_evacuee(src,(StgClosure *)dest);
1467 // We store the size of the just evacuated object in the LDV word so that
1468 // the profiler can guess the position of the next object later.
1469 SET_EVACUAEE_FOR_LDV(src, size_org);
1471 return (StgClosure *)dest;
1474 /* Special version of copy() for when we only want to copy the info
1475 * pointer of an object, but reserve some padding after it. This is
1476 * used to optimise evacuation of BLACKHOLEs.
1481 copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *stp)
1486 nat size_to_copy_org = size_to_copy;
1489 TICK_GC_WORDS_COPIED(size_to_copy);
1490 if (stp->gen_no < evac_gen) {
1491 #ifdef NO_EAGER_PROMOTION
1492 failed_to_evac = rtsTrue;
1494 stp = &generations[evac_gen].steps[0];
1498 if (stp->hp + size_to_reserve >= stp->hpLim) {
1499 gc_alloc_block(stp);
1502 for(to = stp->hp, from = (P_)src; size_to_copy>0; --size_to_copy) {
1507 stp->hp += size_to_reserve;
1508 upd_evacuee(src,(StgClosure *)dest);
1510 // We store the size of the just evacuated object in the LDV word so that
1511 // the profiler can guess the position of the next object later.
1512 // size_to_copy_org is wrong because the closure already occupies size_to_reserve
1514 SET_EVACUAEE_FOR_LDV(src, size_to_reserve);
1516 if (size_to_reserve - size_to_copy_org > 0)
1517 FILL_SLOP(stp->hp - 1, (int)(size_to_reserve - size_to_copy_org));
1519 return (StgClosure *)dest;
1523 /* -----------------------------------------------------------------------------
1524 Evacuate a large object
1526 This just consists of removing the object from the (doubly-linked)
1527 step->large_objects list, and linking it on to the (singly-linked)
1528 step->new_large_objects list, from where it will be scavenged later.
1530 Convention: bd->flags has BF_EVACUATED set for a large object
1531 that has been evacuated, or unset otherwise.
1532 -------------------------------------------------------------------------- */
1536 evacuate_large(StgPtr p)
1538 bdescr *bd = Bdescr(p);
1541 // object must be at the beginning of the block (or be a ByteArray)
1542 ASSERT(get_itbl((StgClosure *)p)->type == ARR_WORDS ||
1543 (((W_)p & BLOCK_MASK) == 0));
1545 // already evacuated?
1546 if (bd->flags & BF_EVACUATED) {
1547 /* Don't forget to set the failed_to_evac flag if we didn't get
1548 * the desired destination (see comments in evacuate()).
1550 if (bd->gen_no < evac_gen) {
1551 failed_to_evac = rtsTrue;
1552 TICK_GC_FAILED_PROMOTION();
1558 // remove from large_object list
1560 bd->u.back->link = bd->link;
1561 } else { // first object in the list
1562 stp->large_objects = bd->link;
1565 bd->link->u.back = bd->u.back;
1568 /* link it on to the evacuated large object list of the destination step
1571 if (stp->gen_no < evac_gen) {
1572 #ifdef NO_EAGER_PROMOTION
1573 failed_to_evac = rtsTrue;
1575 stp = &generations[evac_gen].steps[0];
1580 bd->gen_no = stp->gen_no;
1581 bd->link = stp->new_large_objects;
1582 stp->new_large_objects = bd;
1583 bd->flags |= BF_EVACUATED;
1586 /* -----------------------------------------------------------------------------
1587 Adding a MUT_CONS to an older generation.
1589 This is necessary from time to time when we end up with an
1590 old-to-new generation pointer in a non-mutable object. We defer
1591 the promotion until the next GC.
1592 -------------------------------------------------------------------------- */
1595 mkMutCons(StgClosure *ptr, generation *gen)
1600 stp = &gen->steps[0];
1602 /* chain a new block onto the to-space for the destination step if
1605 if (stp->hp + sizeofW(StgIndOldGen) >= stp->hpLim) {
1606 gc_alloc_block(stp);
1609 q = (StgMutVar *)stp->hp;
1610 stp->hp += sizeofW(StgMutVar);
1612 SET_HDR(q,&stg_MUT_CONS_info,CCS_GC);
1614 recordOldToNewPtrs((StgMutClosure *)q);
1616 return (StgClosure *)q;
1619 /* -----------------------------------------------------------------------------
1622 This is called (eventually) for every live object in the system.
1624 The caller to evacuate specifies a desired generation in the
1625 evac_gen global variable. The following conditions apply to
1626 evacuating an object which resides in generation M when we're
1627 collecting up to generation N
1631 else evac to step->to
1633 if M < evac_gen evac to evac_gen, step 0
1635 if the object is already evacuated, then we check which generation
1638 if M >= evac_gen do nothing
1639 if M < evac_gen set failed_to_evac flag to indicate that we
1640 didn't manage to evacuate this object into evac_gen.
1645 evacuate() is the single most important function performance-wise
1646 in the GC. Various things have been tried to speed it up, but as
1647 far as I can tell the code generated by gcc 3.2 with -O2 is about
1648 as good as it's going to get. We pass the argument to evacuate()
1649 in a register using the 'regparm' attribute (see the prototype for
1650 evacuate() near the top of this file).
1652 Changing evacuate() to take an (StgClosure **) rather than
1653 returning the new pointer seems attractive, because we can avoid
1654 writing back the pointer when it hasn't changed (eg. for a static
1655 object, or an object in a generation > N). However, I tried it and
1656 it doesn't help. One reason is that the (StgClosure **) pointer
1657 gets spilled to the stack inside evacuate(), resulting in far more
1658 extra reads/writes than we save.
1659 -------------------------------------------------------------------------- */
1661 REGPARM1 static StgClosure *
1662 evacuate(StgClosure *q)
1667 const StgInfoTable *info;
1670 if (HEAP_ALLOCED(q)) {
1673 if (bd->gen_no > N) {
1674 /* Can't evacuate this object, because it's in a generation
1675 * older than the ones we're collecting. Let's hope that it's
1676 * in evac_gen or older, or we will have to arrange to track
1677 * this pointer using the mutable list.
1679 if (bd->gen_no < evac_gen) {
1681 failed_to_evac = rtsTrue;
1682 TICK_GC_FAILED_PROMOTION();
1687 /* evacuate large objects by re-linking them onto a different list.
1689 if (bd->flags & BF_LARGE) {
1691 if (info->type == TSO &&
1692 ((StgTSO *)q)->what_next == ThreadRelocated) {
1693 q = (StgClosure *)((StgTSO *)q)->link;
1696 evacuate_large((P_)q);
1700 /* If the object is in a step that we're compacting, then we
1701 * need to use an alternative evacuate procedure.
1703 if (bd->flags & BF_COMPACTED) {
1704 if (!is_marked((P_)q,bd)) {
1706 if (mark_stack_full()) {
1707 mark_stack_overflowed = rtsTrue;
1710 push_mark_stack((P_)q);
1718 else stp = NULL; // make sure copy() will crash if HEAP_ALLOCED is wrong
1721 // make sure the info pointer is into text space
1722 ASSERT(LOOKS_LIKE_CLOSURE_PTR(q));
1725 switch (info -> type) {
1729 return copy(q,sizeW_fromITBL(info),stp);
1733 StgWord w = (StgWord)q->payload[0];
1734 if (q->header.info == Czh_con_info &&
1735 // unsigned, so always true: (StgChar)w >= MIN_CHARLIKE &&
1736 (StgChar)w <= MAX_CHARLIKE) {
1737 return (StgClosure *)CHARLIKE_CLOSURE((StgChar)w);
1739 if (q->header.info == Izh_con_info &&
1740 (StgInt)w >= MIN_INTLIKE && (StgInt)w <= MAX_INTLIKE) {
1741 return (StgClosure *)INTLIKE_CLOSURE((StgInt)w);
1743 // else, fall through ...
1749 return copy(q,sizeofW(StgHeader)+1,stp);
1751 case THUNK_1_0: // here because of MIN_UPD_SIZE
1756 #ifdef NO_PROMOTE_THUNKS
1757 if (bd->gen_no == 0 &&
1758 bd->step->no != 0 &&
1759 bd->step->no == generations[bd->gen_no].n_steps-1) {
1763 return copy(q,sizeofW(StgHeader)+2,stp);
1771 return copy(q,sizeofW(StgHeader)+2,stp);
1777 case IND_OLDGEN_PERM:
1781 return copy(q,sizeW_fromITBL(info),stp);
1784 return copy(q,bco_sizeW((StgBCO *)q),stp);
1787 case SE_CAF_BLACKHOLE:
1790 return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
1793 to = copy(q,BLACKHOLE_sizeW(),stp);
1796 case THUNK_SELECTOR:
1800 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
1801 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1804 p = eval_thunk_selector(info->layout.selector_offset,
1808 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1810 // q is still BLACKHOLE'd.
1811 thunk_selector_depth++;
1813 thunk_selector_depth--;
1816 // We store the size of the just evacuated object in the
1817 // LDV word so that the profiler can guess the position of
1818 // the next object later.
1819 SET_EVACUAEE_FOR_LDV(q, THUNK_SELECTOR_sizeW());
1827 // follow chains of indirections, don't evacuate them
1828 q = ((StgInd*)q)->indirectee;
1832 if (info->srt_bitmap != 0 && major_gc &&
1833 THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
1834 THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
1835 static_objects = (StgClosure *)q;
1840 if (info->srt_bitmap != 0 && major_gc &&
1841 FUN_STATIC_LINK((StgClosure *)q) == NULL) {
1842 FUN_STATIC_LINK((StgClosure *)q) = static_objects;
1843 static_objects = (StgClosure *)q;
1848 /* If q->saved_info != NULL, then it's a revertible CAF - it'll be
1849 * on the CAF list, so don't do anything with it here (we'll
1850 * scavenge it later).
1853 && ((StgIndStatic *)q)->saved_info == NULL
1854 && IND_STATIC_LINK((StgClosure *)q) == NULL) {
1855 IND_STATIC_LINK((StgClosure *)q) = static_objects;
1856 static_objects = (StgClosure *)q;
1861 if (major_gc && STATIC_LINK(info,(StgClosure *)q) == NULL) {
1862 STATIC_LINK(info,(StgClosure *)q) = static_objects;
1863 static_objects = (StgClosure *)q;
1867 case CONSTR_INTLIKE:
1868 case CONSTR_CHARLIKE:
1869 case CONSTR_NOCAF_STATIC:
1870 /* no need to put these on the static linked list, they don't need
1884 // shouldn't see these
1885 barf("evacuate: stack frame at %p\n", q);
1889 return copy(q,pap_sizeW((StgPAP*)q),stp);
1892 return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp);
1895 /* Already evacuated, just return the forwarding address.
1896 * HOWEVER: if the requested destination generation (evac_gen) is
1897 * older than the actual generation (because the object was
1898 * already evacuated to a younger generation) then we have to
1899 * set the failed_to_evac flag to indicate that we couldn't
1900 * manage to promote the object to the desired generation.
1902 if (evac_gen > 0) { // optimisation
1903 StgClosure *p = ((StgEvacuated*)q)->evacuee;
1904 if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < evac_gen) {
1905 failed_to_evac = rtsTrue;
1906 TICK_GC_FAILED_PROMOTION();
1909 return ((StgEvacuated*)q)->evacuee;
1912 // just copy the block
1913 return copy(q,arr_words_sizeW((StgArrWords *)q),stp);
1916 case MUT_ARR_PTRS_FROZEN:
1917 // just copy the block
1918 return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
1922 StgTSO *tso = (StgTSO *)q;
1924 /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
1926 if (tso->what_next == ThreadRelocated) {
1927 q = (StgClosure *)tso->link;
1931 /* To evacuate a small TSO, we need to relocate the update frame
1938 new_tso = (StgTSO *)copyPart((StgClosure *)tso,
1940 sizeofW(StgTSO), stp);
1941 move_TSO(tso, new_tso);
1942 for (p = tso->sp, q = new_tso->sp;
1943 p < tso->stack+tso->stack_size;) {
1947 return (StgClosure *)new_tso;
1952 case RBH: // cf. BLACKHOLE_BQ
1954 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
1955 to = copy(q,BLACKHOLE_sizeW(),stp);
1956 //ToDo: derive size etc from reverted IP
1957 //to = copy(q,size,stp);
1959 debugBelch("@@ evacuate: RBH %p (%s) to %p (%s)",
1960 q, info_type(q), to, info_type(to)));
1965 ASSERT(sizeofW(StgBlockedFetch) >= MIN_NONUPD_SIZE);
1966 to = copy(q,sizeofW(StgBlockedFetch),stp);
1968 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
1969 q, info_type(q), to, info_type(to)));
1976 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1977 to = copy(q,sizeofW(StgFetchMe),stp);
1979 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
1980 q, info_type(q), to, info_type(to)));
1984 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1985 to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
1987 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
1988 q, info_type(q), to, info_type(to)));
1993 barf("evacuate: strange closure type %d", (int)(info->type));
1999 /* -----------------------------------------------------------------------------
2000 Evaluate a THUNK_SELECTOR if possible.
2002 returns: NULL if we couldn't evaluate this THUNK_SELECTOR, or
2003 a closure pointer if we evaluated it and this is the result. Note
2004 that "evaluating" the THUNK_SELECTOR doesn't necessarily mean
2005 reducing it to HNF, just that we have eliminated the selection.
2006 The result might be another thunk, or even another THUNK_SELECTOR.
2008 If the return value is non-NULL, the original selector thunk has
2009 been BLACKHOLE'd, and should be updated with an indirection or a
2010 forwarding pointer. If the return value is NULL, then the selector
2012 -------------------------------------------------------------------------- */
2014 static inline rtsBool
2015 is_to_space ( StgClosure *p )
2019 bd = Bdescr((StgPtr)p);
2020 if (HEAP_ALLOCED(p) &&
2021 ((bd->flags & BF_EVACUATED)
2022 || ((bd->flags & BF_COMPACTED) &&
2023 is_marked((P_)p,bd)))) {
2031 eval_thunk_selector( nat field, StgSelector * p )
2034 const StgInfoTable *info_ptr;
2035 StgClosure *selectee;
2037 selectee = p->selectee;
2039 // Save the real info pointer (NOTE: not the same as get_itbl()).
2040 info_ptr = p->header.info;
2042 // If the THUNK_SELECTOR is in a generation that we are not
2043 // collecting, then bail out early. We won't be able to save any
2044 // space in any case, and updating with an indirection is trickier
2046 if (Bdescr((StgPtr)p)->gen_no > N) {
2050 // BLACKHOLE the selector thunk, since it is now under evaluation.
2051 // This is important to stop us going into an infinite loop if
2052 // this selector thunk eventually refers to itself.
2053 SET_INFO(p,&stg_BLACKHOLE_info);
2057 // We don't want to end up in to-space, because this causes
2058 // problems when the GC later tries to evacuate the result of
2059 // eval_thunk_selector(). There are various ways this could
2062 // 1. following an IND_STATIC
2064 // 2. when the old generation is compacted, the mark phase updates
2065 // from-space pointers to be to-space pointers, and we can't
2066 // reliably tell which we're following (eg. from an IND_STATIC).
2068 // 3. compacting GC again: if we're looking at a constructor in
2069 // the compacted generation, it might point directly to objects
2070 // in to-space. We must bale out here, otherwise doing the selection
2071 // will result in a to-space pointer being returned.
2073 // (1) is dealt with using a BF_EVACUATED test on the
2074 // selectee. (2) and (3): we can tell if we're looking at an
2075 // object in the compacted generation that might point to
2076 // to-space objects by testing that (a) it is BF_COMPACTED, (b)
2077 // the compacted generation is being collected, and (c) the
2078 // object is marked. Only a marked object may have pointers that
2079 // point to to-space objects, because that happens when
2082 // The to-space test is now embodied in the in_to_space() inline
2083 // function, as it is re-used below.
2085 if (is_to_space(selectee)) {
2089 info = get_itbl(selectee);
2090 switch (info->type) {
2098 case CONSTR_NOCAF_STATIC:
2099 // check that the size is in range
2100 ASSERT(field < (StgWord32)(info->layout.payload.ptrs +
2101 info->layout.payload.nptrs));
2103 // Select the right field from the constructor, and check
2104 // that the result isn't in to-space. It might be in
2105 // to-space if, for example, this constructor contains
2106 // pointers to younger-gen objects (and is on the mut-once
2111 q = selectee->payload[field];
2112 if (is_to_space(q)) {
2122 case IND_OLDGEN_PERM:
2124 selectee = ((StgInd *)selectee)->indirectee;
2128 // We don't follow pointers into to-space; the constructor
2129 // has already been evacuated, so we won't save any space
2130 // leaks by evaluating this selector thunk anyhow.
2133 case THUNK_SELECTOR:
2137 // check that we don't recurse too much, re-using the
2138 // depth bound also used in evacuate().
2139 thunk_selector_depth++;
2140 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
2144 val = eval_thunk_selector(info->layout.selector_offset,
2145 (StgSelector *)selectee);
2147 thunk_selector_depth--;
2152 // We evaluated this selector thunk, so update it with
2153 // an indirection. NOTE: we don't use UPD_IND here,
2154 // because we are guaranteed that p is in a generation
2155 // that we are collecting, and we never want to put the
2156 // indirection on a mutable list.
2158 // For the purposes of LDV profiling, we have destroyed
2159 // the original selector thunk.
2160 SET_INFO(p, info_ptr);
2161 LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(selectee);
2163 ((StgInd *)selectee)->indirectee = val;
2164 SET_INFO(selectee,&stg_IND_info);
2166 // For the purposes of LDV profiling, we have created an
2168 LDV_RECORD_CREATE(selectee);
2185 case SE_CAF_BLACKHOLE:
2198 // not evaluated yet
2202 barf("eval_thunk_selector: strange selectee %d",
2207 // We didn't manage to evaluate this thunk; restore the old info pointer
2208 SET_INFO(p, info_ptr);
2212 /* -----------------------------------------------------------------------------
2213 move_TSO is called to update the TSO structure after it has been
2214 moved from one place to another.
2215 -------------------------------------------------------------------------- */
2218 move_TSO (StgTSO *src, StgTSO *dest)
2222 // relocate the stack pointer...
2223 diff = (StgPtr)dest - (StgPtr)src; // In *words*
2224 dest->sp = (StgPtr)dest->sp + diff;
2227 /* Similar to scavenge_large_bitmap(), but we don't write back the
2228 * pointers we get back from evacuate().
2231 scavenge_large_srt_bitmap( StgLargeSRT *large_srt )
2238 bitmap = large_srt->l.bitmap[b];
2239 size = (nat)large_srt->l.size;
2240 p = (StgClosure **)large_srt->srt;
2241 for (i = 0; i < size; ) {
2242 if ((bitmap & 1) != 0) {
2247 if (i % BITS_IN(W_) == 0) {
2249 bitmap = large_srt->l.bitmap[b];
2251 bitmap = bitmap >> 1;
2256 /* evacuate the SRT. If srt_bitmap is zero, then there isn't an
2257 * srt field in the info table. That's ok, because we'll
2258 * never dereference it.
2261 scavenge_srt (StgClosure **srt, nat srt_bitmap)
2266 bitmap = srt_bitmap;
2269 if (bitmap == (StgHalfWord)(-1)) {
2270 scavenge_large_srt_bitmap( (StgLargeSRT *)srt );
2274 while (bitmap != 0) {
2275 if ((bitmap & 1) != 0) {
2276 #ifdef ENABLE_WIN32_DLL_SUPPORT
2277 // Special-case to handle references to closures hiding out in DLLs, since
2278 // double indirections required to get at those. The code generator knows
2279 // which is which when generating the SRT, so it stores the (indirect)
2280 // reference to the DLL closure in the table by first adding one to it.
2281 // We check for this here, and undo the addition before evacuating it.
2283 // If the SRT entry hasn't got bit 0 set, the SRT entry points to a
2284 // closure that's fixed at link-time, and no extra magic is required.
2285 if ( (unsigned long)(*srt) & 0x1 ) {
2286 evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
2295 bitmap = bitmap >> 1;
2301 scavenge_thunk_srt(const StgInfoTable *info)
2303 StgThunkInfoTable *thunk_info;
2305 thunk_info = itbl_to_thunk_itbl(info);
2306 scavenge_srt((StgClosure **)thunk_info->srt, thunk_info->i.srt_bitmap);
2310 scavenge_fun_srt(const StgInfoTable *info)
2312 StgFunInfoTable *fun_info;
2314 fun_info = itbl_to_fun_itbl(info);
2315 scavenge_srt((StgClosure **)fun_info->f.srt, fun_info->i.srt_bitmap);
2319 scavenge_ret_srt(const StgInfoTable *info)
2321 StgRetInfoTable *ret_info;
2323 ret_info = itbl_to_ret_itbl(info);
2324 scavenge_srt((StgClosure **)ret_info->srt, ret_info->i.srt_bitmap);
2327 /* -----------------------------------------------------------------------------
2329 -------------------------------------------------------------------------- */
2332 scavengeTSO (StgTSO *tso)
2334 // chase the link field for any TSOs on the same queue
2335 (StgClosure *)tso->link = evacuate((StgClosure *)tso->link);
2336 if ( tso->why_blocked == BlockedOnMVar
2337 || tso->why_blocked == BlockedOnBlackHole
2338 || tso->why_blocked == BlockedOnException
2340 || tso->why_blocked == BlockedOnGA
2341 || tso->why_blocked == BlockedOnGA_NoSend
2344 tso->block_info.closure = evacuate(tso->block_info.closure);
2346 if ( tso->blocked_exceptions != NULL ) {
2347 tso->blocked_exceptions =
2348 (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
2351 // scavenge this thread's stack
2352 scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
2355 /* -----------------------------------------------------------------------------
2356 Blocks of function args occur on the stack (at the top) and
2358 -------------------------------------------------------------------------- */
2360 STATIC_INLINE StgPtr
2361 scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
2368 switch (fun_info->f.fun_type) {
2370 bitmap = BITMAP_BITS(fun_info->f.bitmap);
2371 size = BITMAP_SIZE(fun_info->f.bitmap);
2374 size = ((StgLargeBitmap *)fun_info->f.bitmap)->size;
2375 scavenge_large_bitmap(p, (StgLargeBitmap *)fun_info->f.bitmap, size);
2379 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2380 size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->f.fun_type]);
2383 if ((bitmap & 1) == 0) {
2384 (StgClosure *)*p = evacuate((StgClosure *)*p);
2387 bitmap = bitmap >> 1;
2395 STATIC_INLINE StgPtr
2396 scavenge_PAP (StgPAP *pap)
2399 StgWord bitmap, size;
2400 StgFunInfoTable *fun_info;
2402 pap->fun = evacuate(pap->fun);
2403 fun_info = get_fun_itbl(pap->fun);
2404 ASSERT(fun_info->i.type != PAP);
2406 p = (StgPtr)pap->payload;
2409 switch (fun_info->f.fun_type) {
2411 bitmap = BITMAP_BITS(fun_info->f.bitmap);
2414 scavenge_large_bitmap(p, (StgLargeBitmap *)fun_info->f.bitmap, size);
2418 scavenge_large_bitmap((StgPtr)pap->payload, BCO_BITMAP(pap->fun), size);
2422 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2426 if ((bitmap & 1) == 0) {
2427 (StgClosure *)*p = evacuate((StgClosure *)*p);
2430 bitmap = bitmap >> 1;
2438 /* -----------------------------------------------------------------------------
2439 Scavenge a given step until there are no more objects in this step
2442 evac_gen is set by the caller to be either zero (for a step in a
2443 generation < N) or G where G is the generation of the step being
2446 We sometimes temporarily change evac_gen back to zero if we're
2447 scavenging a mutable object where early promotion isn't such a good
2449 -------------------------------------------------------------------------- */
2457 nat saved_evac_gen = evac_gen;
2462 failed_to_evac = rtsFalse;
2464 /* scavenge phase - standard breadth-first scavenging of the
2468 while (bd != stp->hp_bd || p < stp->hp) {
2470 // If we're at the end of this block, move on to the next block
2471 if (bd != stp->hp_bd && p == bd->free) {
2477 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2478 info = get_itbl((StgClosure *)p);
2480 ASSERT(thunk_selector_depth == 0);
2483 switch (info->type) {
2486 /* treat MVars specially, because we don't want to evacuate the
2487 * mut_link field in the middle of the closure.
2490 StgMVar *mvar = ((StgMVar *)p);
2492 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
2493 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
2494 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
2495 evac_gen = saved_evac_gen;
2496 recordMutable((StgMutClosure *)mvar);
2497 failed_to_evac = rtsFalse; // mutable.
2498 p += sizeofW(StgMVar);
2503 scavenge_fun_srt(info);
2504 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2505 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2506 p += sizeofW(StgHeader) + 2;
2510 scavenge_thunk_srt(info);
2512 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2513 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2514 p += sizeofW(StgHeader) + 2;
2518 scavenge_thunk_srt(info);
2519 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2520 p += sizeofW(StgHeader) + 2; // MIN_UPD_SIZE
2524 scavenge_fun_srt(info);
2526 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2527 p += sizeofW(StgHeader) + 1;
2531 scavenge_thunk_srt(info);
2532 p += sizeofW(StgHeader) + 2; // MIN_UPD_SIZE
2536 scavenge_fun_srt(info);
2538 p += sizeofW(StgHeader) + 1;
2542 scavenge_thunk_srt(info);
2543 p += sizeofW(StgHeader) + 2;
2547 scavenge_fun_srt(info);
2549 p += sizeofW(StgHeader) + 2;
2553 scavenge_thunk_srt(info);
2554 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2555 p += sizeofW(StgHeader) + 2;
2559 scavenge_fun_srt(info);
2561 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2562 p += sizeofW(StgHeader) + 2;
2566 scavenge_fun_srt(info);
2570 scavenge_thunk_srt(info);
2581 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2582 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2583 (StgClosure *)*p = evacuate((StgClosure *)*p);
2585 p += info->layout.payload.nptrs;
2590 StgBCO *bco = (StgBCO *)p;
2591 (StgClosure *)bco->instrs = evacuate((StgClosure *)bco->instrs);
2592 (StgClosure *)bco->literals = evacuate((StgClosure *)bco->literals);
2593 (StgClosure *)bco->ptrs = evacuate((StgClosure *)bco->ptrs);
2594 (StgClosure *)bco->itbls = evacuate((StgClosure *)bco->itbls);
2595 p += bco_sizeW(bco);
2600 if (stp->gen->no != 0) {
2603 // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an
2604 // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
2605 LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
2608 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
2610 SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
2612 // We pretend that p has just been created.
2613 LDV_RECORD_CREATE((StgClosure *)p);
2616 case IND_OLDGEN_PERM:
2617 ((StgIndOldGen *)p)->indirectee =
2618 evacuate(((StgIndOldGen *)p)->indirectee);
2619 if (failed_to_evac) {
2620 failed_to_evac = rtsFalse;
2621 recordOldToNewPtrs((StgMutClosure *)p);
2623 p += sizeofW(StgIndOldGen);
2628 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2629 evac_gen = saved_evac_gen;
2630 recordMutable((StgMutClosure *)p);
2631 failed_to_evac = rtsFalse; // mutable anyhow
2632 p += sizeofW(StgMutVar);
2637 failed_to_evac = rtsFalse; // mutable anyhow
2638 p += sizeofW(StgMutVar);
2642 case SE_CAF_BLACKHOLE:
2645 p += BLACKHOLE_sizeW();
2650 StgBlockingQueue *bh = (StgBlockingQueue *)p;
2651 (StgClosure *)bh->blocking_queue =
2652 evacuate((StgClosure *)bh->blocking_queue);
2653 recordMutable((StgMutClosure *)bh);
2654 failed_to_evac = rtsFalse;
2655 p += BLACKHOLE_sizeW();
2659 case THUNK_SELECTOR:
2661 StgSelector *s = (StgSelector *)p;
2662 s->selectee = evacuate(s->selectee);
2663 p += THUNK_SELECTOR_sizeW();
2667 // A chunk of stack saved in a heap object
2670 StgAP_STACK *ap = (StgAP_STACK *)p;
2672 ap->fun = evacuate(ap->fun);
2673 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2674 p = (StgPtr)ap->payload + ap->size;
2680 p = scavenge_PAP((StgPAP *)p);
2684 // nothing to follow
2685 p += arr_words_sizeW((StgArrWords *)p);
2689 // follow everything
2693 evac_gen = 0; // repeatedly mutable
2694 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2695 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2696 (StgClosure *)*p = evacuate((StgClosure *)*p);
2698 evac_gen = saved_evac_gen;
2699 recordMutable((StgMutClosure *)q);
2700 failed_to_evac = rtsFalse; // mutable anyhow.
2704 case MUT_ARR_PTRS_FROZEN:
2705 // follow everything
2709 // Set the mut_link field to NULL, so that we will put this
2710 // array back on the mutable list if it is subsequently thawed
2712 ((StgMutArrPtrs*)p)->mut_link = NULL;
2714 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2715 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2716 (StgClosure *)*p = evacuate((StgClosure *)*p);
2718 // it's tempting to recordMutable() if failed_to_evac is
2719 // false, but that breaks some assumptions (eg. every
2720 // closure on the mutable list is supposed to have the MUT
2721 // flag set, and MUT_ARR_PTRS_FROZEN doesn't).
2727 StgTSO *tso = (StgTSO *)p;
2730 evac_gen = saved_evac_gen;
2731 recordMutable((StgMutClosure *)tso);
2732 failed_to_evac = rtsFalse; // mutable anyhow.
2733 p += tso_sizeW(tso);
2738 case RBH: // cf. BLACKHOLE_BQ
2741 nat size, ptrs, nonptrs, vhs;
2743 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2745 StgRBH *rbh = (StgRBH *)p;
2746 (StgClosure *)rbh->blocking_queue =
2747 evacuate((StgClosure *)rbh->blocking_queue);
2748 recordMutable((StgMutClosure *)to);
2749 failed_to_evac = rtsFalse; // mutable anyhow.
2751 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2752 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2753 // ToDo: use size of reverted closure here!
2754 p += BLACKHOLE_sizeW();
2760 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2761 // follow the pointer to the node which is being demanded
2762 (StgClosure *)bf->node =
2763 evacuate((StgClosure *)bf->node);
2764 // follow the link to the rest of the blocking queue
2765 (StgClosure *)bf->link =
2766 evacuate((StgClosure *)bf->link);
2767 if (failed_to_evac) {
2768 failed_to_evac = rtsFalse;
2769 recordMutable((StgMutClosure *)bf);
2772 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
2773 bf, info_type((StgClosure *)bf),
2774 bf->node, info_type(bf->node)));
2775 p += sizeofW(StgBlockedFetch);
2783 p += sizeofW(StgFetchMe);
2784 break; // nothing to do in this case
2786 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
2788 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
2789 (StgClosure *)fmbq->blocking_queue =
2790 evacuate((StgClosure *)fmbq->blocking_queue);
2791 if (failed_to_evac) {
2792 failed_to_evac = rtsFalse;
2793 recordMutable((StgMutClosure *)fmbq);
2796 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
2797 p, info_type((StgClosure *)p)));
2798 p += sizeofW(StgFetchMeBlockingQueue);
2804 barf("scavenge: unimplemented/strange closure type %d @ %p",
2808 /* If we didn't manage to promote all the objects pointed to by
2809 * the current object, then we have to designate this object as
2810 * mutable (because it contains old-to-new generation pointers).
2812 if (failed_to_evac) {
2813 failed_to_evac = rtsFalse;
2814 mkMutCons((StgClosure *)q, &generations[evac_gen]);
2822 /* -----------------------------------------------------------------------------
2823 Scavenge everything on the mark stack.
2825 This is slightly different from scavenge():
2826 - we don't walk linearly through the objects, so the scavenger
2827 doesn't need to advance the pointer on to the next object.
2828 -------------------------------------------------------------------------- */
2831 scavenge_mark_stack(void)
2837 evac_gen = oldest_gen->no;
2838 saved_evac_gen = evac_gen;
2841 while (!mark_stack_empty()) {
2842 p = pop_mark_stack();
2844 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2845 info = get_itbl((StgClosure *)p);
2848 switch (info->type) {
2851 /* treat MVars specially, because we don't want to evacuate the
2852 * mut_link field in the middle of the closure.
2855 StgMVar *mvar = ((StgMVar *)p);
2857 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
2858 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
2859 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
2860 evac_gen = saved_evac_gen;
2861 failed_to_evac = rtsFalse; // mutable.
2866 scavenge_fun_srt(info);
2867 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2868 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2872 scavenge_thunk_srt(info);
2874 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2875 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2880 scavenge_fun_srt(info);
2881 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2886 scavenge_thunk_srt(info);
2889 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2894 scavenge_fun_srt(info);
2899 scavenge_thunk_srt(info);
2907 scavenge_fun_srt(info);
2911 scavenge_thunk_srt(info);
2922 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2923 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2924 (StgClosure *)*p = evacuate((StgClosure *)*p);
2930 StgBCO *bco = (StgBCO *)p;
2931 (StgClosure *)bco->instrs = evacuate((StgClosure *)bco->instrs);
2932 (StgClosure *)bco->literals = evacuate((StgClosure *)bco->literals);
2933 (StgClosure *)bco->ptrs = evacuate((StgClosure *)bco->ptrs);
2934 (StgClosure *)bco->itbls = evacuate((StgClosure *)bco->itbls);
2939 // don't need to do anything here: the only possible case
2940 // is that we're in a 1-space compacting collector, with
2941 // no "old" generation.
2945 case IND_OLDGEN_PERM:
2946 ((StgIndOldGen *)p)->indirectee =
2947 evacuate(((StgIndOldGen *)p)->indirectee);
2948 if (failed_to_evac) {
2949 recordOldToNewPtrs((StgMutClosure *)p);
2951 failed_to_evac = rtsFalse;
2956 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2957 evac_gen = saved_evac_gen;
2958 failed_to_evac = rtsFalse;
2963 failed_to_evac = rtsFalse;
2967 case SE_CAF_BLACKHOLE:
2975 StgBlockingQueue *bh = (StgBlockingQueue *)p;
2976 (StgClosure *)bh->blocking_queue =
2977 evacuate((StgClosure *)bh->blocking_queue);
2978 failed_to_evac = rtsFalse;
2982 case THUNK_SELECTOR:
2984 StgSelector *s = (StgSelector *)p;
2985 s->selectee = evacuate(s->selectee);
2989 // A chunk of stack saved in a heap object
2992 StgAP_STACK *ap = (StgAP_STACK *)p;
2994 ap->fun = evacuate(ap->fun);
2995 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3001 scavenge_PAP((StgPAP *)p);
3005 // follow everything
3009 evac_gen = 0; // repeatedly mutable
3010 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3011 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3012 (StgClosure *)*p = evacuate((StgClosure *)*p);
3014 evac_gen = saved_evac_gen;
3015 failed_to_evac = rtsFalse; // mutable anyhow.
3019 case MUT_ARR_PTRS_FROZEN:
3020 // follow everything
3024 // Set the mut_link field to NULL, so that we will put this
3025 // array on the mutable list if it is subsequently thawed
3027 ((StgMutArrPtrs*)p)->mut_link = NULL;
3029 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3030 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3031 (StgClosure *)*p = evacuate((StgClosure *)*p);
3038 StgTSO *tso = (StgTSO *)p;
3041 evac_gen = saved_evac_gen;
3042 failed_to_evac = rtsFalse;
3047 case RBH: // cf. BLACKHOLE_BQ
3050 nat size, ptrs, nonptrs, vhs;
3052 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3054 StgRBH *rbh = (StgRBH *)p;
3055 (StgClosure *)rbh->blocking_queue =
3056 evacuate((StgClosure *)rbh->blocking_queue);
3057 recordMutable((StgMutClosure *)rbh);
3058 failed_to_evac = rtsFalse; // mutable anyhow.
3060 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3061 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3067 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3068 // follow the pointer to the node which is being demanded
3069 (StgClosure *)bf->node =
3070 evacuate((StgClosure *)bf->node);
3071 // follow the link to the rest of the blocking queue
3072 (StgClosure *)bf->link =
3073 evacuate((StgClosure *)bf->link);
3074 if (failed_to_evac) {
3075 failed_to_evac = rtsFalse;
3076 recordMutable((StgMutClosure *)bf);
3079 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3080 bf, info_type((StgClosure *)bf),
3081 bf->node, info_type(bf->node)));
3089 break; // nothing to do in this case
3091 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
3093 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3094 (StgClosure *)fmbq->blocking_queue =
3095 evacuate((StgClosure *)fmbq->blocking_queue);
3096 if (failed_to_evac) {
3097 failed_to_evac = rtsFalse;
3098 recordMutable((StgMutClosure *)fmbq);
3101 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3102 p, info_type((StgClosure *)p)));
3108 barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p",
3112 if (failed_to_evac) {
3113 failed_to_evac = rtsFalse;
3114 mkMutCons((StgClosure *)q, &generations[evac_gen]);
3117 // mark the next bit to indicate "scavenged"
3118 mark(q+1, Bdescr(q));
3120 } // while (!mark_stack_empty())
3122 // start a new linear scan if the mark stack overflowed at some point
3123 if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
3124 IF_DEBUG(gc, debugBelch("scavenge_mark_stack: starting linear scan"));
3125 mark_stack_overflowed = rtsFalse;
3126 oldgen_scan_bd = oldest_gen->steps[0].blocks;
3127 oldgen_scan = oldgen_scan_bd->start;
3130 if (oldgen_scan_bd) {
3131 // push a new thing on the mark stack
3133 // find a closure that is marked but not scavenged, and start
3135 while (oldgen_scan < oldgen_scan_bd->free
3136 && !is_marked(oldgen_scan,oldgen_scan_bd)) {
3140 if (oldgen_scan < oldgen_scan_bd->free) {
3142 // already scavenged?
3143 if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
3144 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3147 push_mark_stack(oldgen_scan);
3148 // ToDo: bump the linear scan by the actual size of the object
3149 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3153 oldgen_scan_bd = oldgen_scan_bd->link;
3154 if (oldgen_scan_bd != NULL) {
3155 oldgen_scan = oldgen_scan_bd->start;
3161 /* -----------------------------------------------------------------------------
3162 Scavenge one object.
3164 This is used for objects that are temporarily marked as mutable
3165 because they contain old-to-new generation pointers. Only certain
3166 objects can have this property.
3167 -------------------------------------------------------------------------- */
3170 scavenge_one(StgPtr p)
3172 const StgInfoTable *info;
3173 nat saved_evac_gen = evac_gen;
3176 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3177 info = get_itbl((StgClosure *)p);
3179 switch (info->type) {
3182 case FUN_1_0: // hardly worth specialising these guys
3202 case IND_OLDGEN_PERM:
3206 end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3207 for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
3208 (StgClosure *)*q = evacuate((StgClosure *)*q);
3214 case SE_CAF_BLACKHOLE:
3219 case THUNK_SELECTOR:
3221 StgSelector *s = (StgSelector *)p;
3222 s->selectee = evacuate(s->selectee);
3227 // nothing to follow
3232 // follow everything
3235 evac_gen = 0; // repeatedly mutable
3236 recordMutable((StgMutClosure *)p);
3237 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3238 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3239 (StgClosure *)*p = evacuate((StgClosure *)*p);
3241 evac_gen = saved_evac_gen;
3242 failed_to_evac = rtsFalse;
3246 case MUT_ARR_PTRS_FROZEN:
3248 // follow everything
3251 // Set the mut_link field to NULL, so that we will put this
3252 // array on the mutable list if it is subsequently thawed
3254 ((StgMutArrPtrs*)p)->mut_link = NULL;
3256 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3257 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3258 (StgClosure *)*p = evacuate((StgClosure *)*p);
3265 StgTSO *tso = (StgTSO *)p;
3267 evac_gen = 0; // repeatedly mutable
3269 recordMutable((StgMutClosure *)tso);
3270 evac_gen = saved_evac_gen;
3271 failed_to_evac = rtsFalse;
3277 StgAP_STACK *ap = (StgAP_STACK *)p;
3279 ap->fun = evacuate(ap->fun);
3280 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3281 p = (StgPtr)ap->payload + ap->size;
3287 p = scavenge_PAP((StgPAP *)p);
3291 // This might happen if for instance a MUT_CONS was pointing to a
3292 // THUNK which has since been updated. The IND_OLDGEN will
3293 // be on the mutable list anyway, so we don't need to do anything
3298 barf("scavenge_one: strange object %d", (int)(info->type));
3301 no_luck = failed_to_evac;
3302 failed_to_evac = rtsFalse;
3306 /* -----------------------------------------------------------------------------
3307 Scavenging mutable lists.
3309 We treat the mutable list of each generation > N (i.e. all the
3310 generations older than the one being collected) as roots. We also
3311 remove non-mutable objects from the mutable list at this point.
3312 -------------------------------------------------------------------------- */
3315 scavenge_mut_once_list(generation *gen)
3317 const StgInfoTable *info;
3318 StgMutClosure *p, *next, *new_list;
3320 p = gen->mut_once_list;
3321 new_list = END_MUT_LIST;
3325 failed_to_evac = rtsFalse;
3327 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
3329 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3332 if (info->type==RBH)
3333 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3335 switch(info->type) {
3338 case IND_OLDGEN_PERM:
3340 /* Try to pull the indirectee into this generation, so we can
3341 * remove the indirection from the mutable list.
3343 ((StgIndOldGen *)p)->indirectee =
3344 evacuate(((StgIndOldGen *)p)->indirectee);
3346 #if 0 && defined(DEBUG)
3347 if (RtsFlags.DebugFlags.gc)
3348 /* Debugging code to print out the size of the thing we just
3352 StgPtr start = gen->steps[0].scan;
3353 bdescr *start_bd = gen->steps[0].scan_bd;
3355 scavenge(&gen->steps[0]);
3356 if (start_bd != gen->steps[0].scan_bd) {
3357 size += (P_)BLOCK_ROUND_UP(start) - start;
3358 start_bd = start_bd->link;
3359 while (start_bd != gen->steps[0].scan_bd) {
3360 size += BLOCK_SIZE_W;
3361 start_bd = start_bd->link;
3363 size += gen->steps[0].scan -
3364 (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
3366 size = gen->steps[0].scan - start;
3368 debugBelch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
3372 /* failed_to_evac might happen if we've got more than two
3373 * generations, we're collecting only generation 0, the
3374 * indirection resides in generation 2 and the indirectee is
3377 if (failed_to_evac) {
3378 failed_to_evac = rtsFalse;
3379 p->mut_link = new_list;
3382 /* the mut_link field of an IND_STATIC is overloaded as the
3383 * static link field too (it just so happens that we don't need
3384 * both at the same time), so we need to NULL it out when
3385 * removing this object from the mutable list because the static
3386 * link fields are all assumed to be NULL before doing a major
3394 /* MUT_CONS is a kind of MUT_VAR, except it that we try to remove
3395 * it from the mutable list if possible by promoting whatever it
3398 if (scavenge_one((StgPtr)((StgMutVar *)p)->var)) {
3399 /* didn't manage to promote everything, so put the
3400 * MUT_CONS back on the list.
3402 p->mut_link = new_list;
3408 // shouldn't have anything else on the mutables list
3409 barf("scavenge_mut_once_list: strange object? %d", (int)(info->type));
3413 gen->mut_once_list = new_list;
3418 scavenge_mutable_list(generation *gen)
3420 const StgInfoTable *info;
3421 StgMutClosure *p, *next;
3423 p = gen->saved_mut_list;
3427 failed_to_evac = rtsFalse;
3429 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
3431 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3434 if (info->type==RBH)
3435 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3437 switch(info->type) {
3440 // follow everything
3441 p->mut_link = gen->mut_list;
3446 end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3447 for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
3448 (StgClosure *)*q = evacuate((StgClosure *)*q);
3453 // Happens if a MUT_ARR_PTRS in the old generation is frozen
3454 case MUT_ARR_PTRS_FROZEN:
3459 end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3460 for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
3461 (StgClosure *)*q = evacuate((StgClosure *)*q);
3464 // Set the mut_link field to NULL, so that we will put this
3465 // array back on the mutable list if it is subsequently thawed
3468 if (failed_to_evac) {
3469 failed_to_evac = rtsFalse;
3470 mkMutCons((StgClosure *)p, gen);
3476 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3477 p->mut_link = gen->mut_list;
3483 StgMVar *mvar = (StgMVar *)p;
3484 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
3485 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
3486 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
3487 p->mut_link = gen->mut_list;
3494 StgTSO *tso = (StgTSO *)p;
3498 /* Don't take this TSO off the mutable list - it might still
3499 * point to some younger objects (because we set evac_gen to 0
3502 tso->mut_link = gen->mut_list;
3503 gen->mut_list = (StgMutClosure *)tso;
3509 StgBlockingQueue *bh = (StgBlockingQueue *)p;
3510 (StgClosure *)bh->blocking_queue =
3511 evacuate((StgClosure *)bh->blocking_queue);
3512 p->mut_link = gen->mut_list;
3517 /* Happens if a BLACKHOLE_BQ in the old generation is updated:
3520 case IND_OLDGEN_PERM:
3521 /* Try to pull the indirectee into this generation, so we can
3522 * remove the indirection from the mutable list.
3525 ((StgIndOldGen *)p)->indirectee =
3526 evacuate(((StgIndOldGen *)p)->indirectee);
3529 if (failed_to_evac) {
3530 failed_to_evac = rtsFalse;
3531 p->mut_link = gen->mut_once_list;
3532 gen->mut_once_list = p;
3539 // HWL: check whether all of these are necessary
3541 case RBH: // cf. BLACKHOLE_BQ
3543 // nat size, ptrs, nonptrs, vhs;
3545 // StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3546 StgRBH *rbh = (StgRBH *)p;
3547 (StgClosure *)rbh->blocking_queue =
3548 evacuate((StgClosure *)rbh->blocking_queue);
3549 if (failed_to_evac) {
3550 failed_to_evac = rtsFalse;
3551 recordMutable((StgMutClosure *)rbh);
3553 // ToDo: use size of reverted closure here!
3554 p += BLACKHOLE_sizeW();
3560 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3561 // follow the pointer to the node which is being demanded
3562 (StgClosure *)bf->node =
3563 evacuate((StgClosure *)bf->node);
3564 // follow the link to the rest of the blocking queue
3565 (StgClosure *)bf->link =
3566 evacuate((StgClosure *)bf->link);
3567 if (failed_to_evac) {
3568 failed_to_evac = rtsFalse;
3569 recordMutable((StgMutClosure *)bf);
3571 p += sizeofW(StgBlockedFetch);
3577 barf("scavenge_mutable_list: REMOTE_REF %d", (int)(info->type));
3580 p += sizeofW(StgFetchMe);
3581 break; // nothing to do in this case
3583 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
3585 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3586 (StgClosure *)fmbq->blocking_queue =
3587 evacuate((StgClosure *)fmbq->blocking_queue);
3588 if (failed_to_evac) {
3589 failed_to_evac = rtsFalse;
3590 recordMutable((StgMutClosure *)fmbq);
3592 p += sizeofW(StgFetchMeBlockingQueue);
3598 // shouldn't have anything else on the mutables list
3599 barf("scavenge_mutable_list: strange object? %d", (int)(info->type));
3606 scavenge_static(void)
3608 StgClosure* p = static_objects;
3609 const StgInfoTable *info;
3611 /* Always evacuate straight to the oldest generation for static
3613 evac_gen = oldest_gen->no;
3615 /* keep going until we've scavenged all the objects on the linked
3617 while (p != END_OF_STATIC_LIST) {
3619 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3622 if (info->type==RBH)
3623 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3625 // make sure the info pointer is into text space
3627 /* Take this object *off* the static_objects list,
3628 * and put it on the scavenged_static_objects list.
3630 static_objects = STATIC_LINK(info,p);
3631 STATIC_LINK(info,p) = scavenged_static_objects;
3632 scavenged_static_objects = p;
3634 switch (info -> type) {
3638 StgInd *ind = (StgInd *)p;
3639 ind->indirectee = evacuate(ind->indirectee);
3641 /* might fail to evacuate it, in which case we have to pop it
3642 * back on the mutable list (and take it off the
3643 * scavenged_static list because the static link and mut link
3644 * pointers are one and the same).
3646 if (failed_to_evac) {
3647 failed_to_evac = rtsFalse;
3648 scavenged_static_objects = IND_STATIC_LINK(p);
3649 ((StgMutClosure *)ind)->mut_link = oldest_gen->mut_once_list;
3650 oldest_gen->mut_once_list = (StgMutClosure *)ind;
3656 scavenge_thunk_srt(info);
3660 scavenge_fun_srt(info);
3667 next = (P_)p->payload + info->layout.payload.ptrs;
3668 // evacuate the pointers
3669 for (q = (P_)p->payload; q < next; q++) {
3670 (StgClosure *)*q = evacuate((StgClosure *)*q);
3676 barf("scavenge_static: strange closure %d", (int)(info->type));
3679 ASSERT(failed_to_evac == rtsFalse);
3681 /* get the next static object from the list. Remember, there might
3682 * be more stuff on this list now that we've done some evacuating!
3683 * (static_objects is a global)
3689 /* -----------------------------------------------------------------------------
3690 scavenge a chunk of memory described by a bitmap
3691 -------------------------------------------------------------------------- */
3694 scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
3700 bitmap = large_bitmap->bitmap[b];
3701 for (i = 0; i < size; ) {
3702 if ((bitmap & 1) == 0) {
3703 (StgClosure *)*p = evacuate((StgClosure *)*p);
3707 if (i % BITS_IN(W_) == 0) {
3709 bitmap = large_bitmap->bitmap[b];
3711 bitmap = bitmap >> 1;
3716 STATIC_INLINE StgPtr
3717 scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap)
3720 if ((bitmap & 1) == 0) {
3721 (StgClosure *)*p = evacuate((StgClosure *)*p);
3724 bitmap = bitmap >> 1;
3730 /* -----------------------------------------------------------------------------
3731 scavenge_stack walks over a section of stack and evacuates all the
3732 objects pointed to by it. We can use the same code for walking
3733 AP_STACK_UPDs, since these are just sections of copied stack.
3734 -------------------------------------------------------------------------- */
3738 scavenge_stack(StgPtr p, StgPtr stack_end)
3740 const StgRetInfoTable* info;
3744 //IF_DEBUG(sanity, debugBelch(" scavenging stack between %p and %p", p, stack_end));
3747 * Each time around this loop, we are looking at a chunk of stack
3748 * that starts with an activation record.
3751 while (p < stack_end) {
3752 info = get_ret_itbl((StgClosure *)p);
3754 switch (info->i.type) {
3757 ((StgUpdateFrame *)p)->updatee
3758 = evacuate(((StgUpdateFrame *)p)->updatee);
3759 p += sizeofW(StgUpdateFrame);
3762 // small bitmap (< 32 entries, or 64 on a 64-bit machine)
3767 bitmap = BITMAP_BITS(info->i.layout.bitmap);
3768 size = BITMAP_SIZE(info->i.layout.bitmap);
3769 // NOTE: the payload starts immediately after the info-ptr, we
3770 // don't have an StgHeader in the same sense as a heap closure.
3772 p = scavenge_small_bitmap(p, size, bitmap);
3775 scavenge_srt((StgClosure **)info->srt, info->i.srt_bitmap);
3783 (StgClosure *)*p = evacuate((StgClosure *)*p);
3786 size = BCO_BITMAP_SIZE(bco);
3787 scavenge_large_bitmap(p, BCO_BITMAP(bco), size);
3792 // large bitmap (> 32 entries, or > 64 on a 64-bit machine)
3798 size = info->i.layout.large_bitmap->size;
3800 scavenge_large_bitmap(p, info->i.layout.large_bitmap, size);
3802 // and don't forget to follow the SRT
3806 // Dynamic bitmap: the mask is stored on the stack, and
3807 // there are a number of non-pointers followed by a number
3808 // of pointers above the bitmapped area. (see StgMacros.h,
3813 dyn = ((StgRetDyn *)p)->liveness;
3815 // traverse the bitmap first
3816 bitmap = RET_DYN_LIVENESS(dyn);
3817 p = (P_)&((StgRetDyn *)p)->payload[0];
3818 size = RET_DYN_BITMAP_SIZE;
3819 p = scavenge_small_bitmap(p, size, bitmap);
3821 // skip over the non-ptr words
3822 p += RET_DYN_NONPTRS(dyn) + RET_DYN_NONPTR_REGS_SIZE;
3824 // follow the ptr words
3825 for (size = RET_DYN_PTRS(dyn); size > 0; size--) {
3826 (StgClosure *)*p = evacuate((StgClosure *)*p);
3834 StgRetFun *ret_fun = (StgRetFun *)p;
3835 StgFunInfoTable *fun_info;
3837 ret_fun->fun = evacuate(ret_fun->fun);
3838 fun_info = get_fun_itbl(ret_fun->fun);
3839 p = scavenge_arg_block(fun_info, ret_fun->payload);
3844 barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->i.type));
3849 /*-----------------------------------------------------------------------------
3850 scavenge the large object list.
3852 evac_gen set by caller; similar games played with evac_gen as with
3853 scavenge() - see comment at the top of scavenge(). Most large
3854 objects are (repeatedly) mutable, so most of the time evac_gen will
3856 --------------------------------------------------------------------------- */
3859 scavenge_large(step *stp)
3864 bd = stp->new_large_objects;
3866 for (; bd != NULL; bd = stp->new_large_objects) {
3868 /* take this object *off* the large objects list and put it on
3869 * the scavenged large objects list. This is so that we can
3870 * treat new_large_objects as a stack and push new objects on
3871 * the front when evacuating.
3873 stp->new_large_objects = bd->link;
3874 dbl_link_onto(bd, &stp->scavenged_large_objects);
3876 // update the block count in this step.
3877 stp->n_scavenged_large_blocks += bd->blocks;
3880 if (scavenge_one(p)) {
3881 mkMutCons((StgClosure *)p, stp->gen);
3886 /* -----------------------------------------------------------------------------
3887 Initialising the static object & mutable lists
3888 -------------------------------------------------------------------------- */
3891 zero_static_object_list(StgClosure* first_static)
3895 const StgInfoTable *info;
3897 for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
3899 link = STATIC_LINK(info, p);
3900 STATIC_LINK(info,p) = NULL;
3904 /* This function is only needed because we share the mutable link
3905 * field with the static link field in an IND_STATIC, so we have to
3906 * zero the mut_link field before doing a major GC, which needs the
3907 * static link field.
3909 * It doesn't do any harm to zero all the mutable link fields on the
3914 zero_mutable_list( StgMutClosure *first )
3916 StgMutClosure *next, *c;
3918 for (c = first; c != END_MUT_LIST; c = next) {
3924 /* -----------------------------------------------------------------------------
3926 -------------------------------------------------------------------------- */
3933 for (c = (StgIndStatic *)caf_list; c != NULL;
3934 c = (StgIndStatic *)c->static_link)
3936 SET_INFO(c, c->saved_info);
3937 c->saved_info = NULL;
3938 // could, but not necessary: c->static_link = NULL;
3944 markCAFs( evac_fn evac )
3948 for (c = (StgIndStatic *)caf_list; c != NULL;
3949 c = (StgIndStatic *)c->static_link)
3951 evac(&c->indirectee);
3955 /* -----------------------------------------------------------------------------
3956 Sanity code for CAF garbage collection.
3958 With DEBUG turned on, we manage a CAF list in addition to the SRT
3959 mechanism. After GC, we run down the CAF list and blackhole any
3960 CAFs which have been garbage collected. This means we get an error
3961 whenever the program tries to enter a garbage collected CAF.
3963 Any garbage collected CAFs are taken off the CAF list at the same
3965 -------------------------------------------------------------------------- */
3967 #if 0 && defined(DEBUG)
3974 const StgInfoTable *info;
3985 ASSERT(info->type == IND_STATIC);
3987 if (STATIC_LINK(info,p) == NULL) {
3988 IF_DEBUG(gccafs, debugBelch("CAF gc'd at 0x%04lx", (long)p));
3990 SET_INFO(p,&stg_BLACKHOLE_info);
3991 p = STATIC_LINK2(info,p);
3995 pp = &STATIC_LINK2(info,p);
4002 // debugBelch("%d CAFs live", i);
4007 /* -----------------------------------------------------------------------------
4010 Whenever a thread returns to the scheduler after possibly doing
4011 some work, we have to run down the stack and black-hole all the
4012 closures referred to by update frames.
4013 -------------------------------------------------------------------------- */
4016 threadLazyBlackHole(StgTSO *tso)
4019 StgRetInfoTable *info;
4020 StgBlockingQueue *bh;
4023 stack_end = &tso->stack[tso->stack_size];
4025 frame = (StgClosure *)tso->sp;
4028 info = get_ret_itbl(frame);
4030 switch (info->i.type) {
4033 bh = (StgBlockingQueue *)((StgUpdateFrame *)frame)->updatee;
4035 /* if the thunk is already blackholed, it means we've also
4036 * already blackholed the rest of the thunks on this stack,
4037 * so we can stop early.
4039 * The blackhole made for a CAF is a CAF_BLACKHOLE, so they
4040 * don't interfere with this optimisation.
4042 if (bh->header.info == &stg_BLACKHOLE_info) {
4046 if (bh->header.info != &stg_BLACKHOLE_BQ_info &&
4047 bh->header.info != &stg_CAF_BLACKHOLE_info) {
4048 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4049 debugBelch("Unexpected lazy BHing required at 0x%04x",(int)bh);
4053 // We pretend that bh is now dead.
4054 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4056 SET_INFO(bh,&stg_BLACKHOLE_info);
4058 // We pretend that bh has just been created.
4059 LDV_RECORD_CREATE(bh);
4062 frame = (StgClosure *) ((StgUpdateFrame *)frame + 1);
4068 // normal stack frames; do nothing except advance the pointer
4070 (StgPtr)frame += stack_frame_sizeW(frame);
4076 /* -----------------------------------------------------------------------------
4079 * Code largely pinched from old RTS, then hacked to bits. We also do
4080 * lazy black holing here.
4082 * -------------------------------------------------------------------------- */
4084 struct stack_gap { StgWord gap_size; struct stack_gap *next_gap; };
4087 threadSqueezeStack(StgTSO *tso)
4090 rtsBool prev_was_update_frame;
4091 StgClosure *updatee = NULL;
4093 StgRetInfoTable *info;
4094 StgWord current_gap_size;
4095 struct stack_gap *gap;
4098 // Traverse the stack upwards, replacing adjacent update frames
4099 // with a single update frame and a "stack gap". A stack gap
4100 // contains two values: the size of the gap, and the distance
4101 // to the next gap (or the stack top).
4103 bottom = &(tso->stack[tso->stack_size]);
4107 ASSERT(frame < bottom);
4109 prev_was_update_frame = rtsFalse;
4110 current_gap_size = 0;
4111 gap = (struct stack_gap *) (tso->sp - sizeofW(StgUpdateFrame));
4113 while (frame < bottom) {
4115 info = get_ret_itbl((StgClosure *)frame);
4116 switch (info->i.type) {
4120 StgUpdateFrame *upd = (StgUpdateFrame *)frame;
4122 if (upd->updatee->header.info == &stg_BLACKHOLE_info) {
4124 // found a BLACKHOLE'd update frame; we've been here
4125 // before, in a previous GC, so just break out.
4127 // Mark the end of the gap, if we're in one.
4128 if (current_gap_size != 0) {
4129 gap = (struct stack_gap *)(frame-sizeofW(StgUpdateFrame));
4132 frame += sizeofW(StgUpdateFrame);
4133 goto done_traversing;
4136 if (prev_was_update_frame) {
4138 TICK_UPD_SQUEEZED();
4139 /* wasn't there something about update squeezing and ticky to be
4140 * sorted out? oh yes: we aren't counting each enter properly
4141 * in this case. See the log somewhere. KSW 1999-04-21
4143 * Check two things: that the two update frames don't point to
4144 * the same object, and that the updatee_bypass isn't already an
4145 * indirection. Both of these cases only happen when we're in a
4146 * block hole-style loop (and there are multiple update frames
4147 * on the stack pointing to the same closure), but they can both
4148 * screw us up if we don't check.
4150 if (upd->updatee != updatee && !closure_IND(upd->updatee)) {
4151 // this wakes the threads up
4152 UPD_IND_NOLOCK(upd->updatee, updatee);
4155 // now mark this update frame as a stack gap. The gap
4156 // marker resides in the bottom-most update frame of
4157 // the series of adjacent frames, and covers all the
4158 // frames in this series.
4159 current_gap_size += sizeofW(StgUpdateFrame);
4160 ((struct stack_gap *)frame)->gap_size = current_gap_size;
4161 ((struct stack_gap *)frame)->next_gap = gap;
4163 frame += sizeofW(StgUpdateFrame);
4167 // single update frame, or the topmost update frame in a series
4169 StgBlockingQueue *bh = (StgBlockingQueue *)upd->updatee;
4171 // Do lazy black-holing
4172 if (bh->header.info != &stg_BLACKHOLE_info &&
4173 bh->header.info != &stg_BLACKHOLE_BQ_info &&
4174 bh->header.info != &stg_CAF_BLACKHOLE_info) {
4175 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4176 debugBelch("Unexpected lazy BHing required at 0x%04x",(int)bh);
4179 /* zero out the slop so that the sanity checker can tell
4180 * where the next closure is.
4183 StgInfoTable *bh_info = get_itbl(bh);
4184 nat np = bh_info->layout.payload.ptrs,
4185 nw = bh_info->layout.payload.nptrs, i;
4186 /* don't zero out slop for a THUNK_SELECTOR,
4187 * because its layout info is used for a
4188 * different purpose, and it's exactly the
4189 * same size as a BLACKHOLE in any case.
4191 if (bh_info->type != THUNK_SELECTOR) {
4192 for (i = 0; i < np + nw; i++) {
4193 ((StgClosure *)bh)->payload[i] = INVALID_OBJECT;
4199 // We pretend that bh is now dead.
4200 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4202 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
4203 SET_INFO(bh,&stg_BLACKHOLE_info);
4205 // We pretend that bh has just been created.
4206 LDV_RECORD_CREATE(bh);
4209 prev_was_update_frame = rtsTrue;
4210 updatee = upd->updatee;
4211 frame += sizeofW(StgUpdateFrame);
4217 prev_was_update_frame = rtsFalse;
4219 // we're not in a gap... check whether this is the end of a gap
4220 // (an update frame can't be the end of a gap).
4221 if (current_gap_size != 0) {
4222 gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
4224 current_gap_size = 0;
4226 frame += stack_frame_sizeW((StgClosure *)frame);
4233 // Now we have a stack with gaps in it, and we have to walk down
4234 // shoving the stack up to fill in the gaps. A diagram might
4238 // | ********* | <- sp
4242 // | stack_gap | <- gap | chunk_size
4244 // | ......... | <- gap_end v
4250 // 'sp' points the the current top-of-stack
4251 // 'gap' points to the stack_gap structure inside the gap
4252 // ***** indicates real stack data
4253 // ..... indicates gap
4254 // <empty> indicates unused
4258 void *gap_start, *next_gap_start, *gap_end;
4261 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4262 sp = next_gap_start;
4264 while ((StgPtr)gap > tso->sp) {
4266 // we're working in *bytes* now...
4267 gap_start = next_gap_start;
4268 gap_end = (void*) ((unsigned char*)gap_start - gap->gap_size * sizeof(W_));
4270 gap = gap->next_gap;
4271 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4273 chunk_size = (unsigned char*)gap_end - (unsigned char*)next_gap_start;
4274 (unsigned char*)sp -= chunk_size;
4275 memmove(sp, next_gap_start, chunk_size);
4278 tso->sp = (StgPtr)sp;
4282 /* -----------------------------------------------------------------------------
4285 * We have to prepare for GC - this means doing lazy black holing
4286 * here. We also take the opportunity to do stack squeezing if it's
4288 * -------------------------------------------------------------------------- */
4290 threadPaused(StgTSO *tso)
4292 if ( RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue )
4293 threadSqueezeStack(tso); // does black holing too
4295 threadLazyBlackHole(tso);
4298 /* -----------------------------------------------------------------------------
4300 * -------------------------------------------------------------------------- */
4304 printMutOnceList(generation *gen)
4306 StgMutClosure *p, *next;
4308 p = gen->mut_once_list;
4311 debugBelch("@@ Mut once list %p: ", gen->mut_once_list);
4312 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
4313 debugBelch("%p (%s), ",
4314 p, info_type((StgClosure *)p));
4320 printMutableList(generation *gen)
4322 StgMutClosure *p, *next;
4327 debugBelch("@@ Mutable list %p: ", gen->mut_list);
4328 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
4329 debugBelch("%p (%s), ",
4330 p, info_type((StgClosure *)p));
4335 STATIC_INLINE rtsBool
4336 maybeLarge(StgClosure *closure)
4338 StgInfoTable *info = get_itbl(closure);
4340 /* closure types that may be found on the new_large_objects list;
4341 see scavenge_large */
4342 return (info->type == MUT_ARR_PTRS ||
4343 info->type == MUT_ARR_PTRS_FROZEN ||
4344 info->type == TSO ||
4345 info->type == ARR_WORDS);