1 /* -----------------------------------------------------------------------------
2 * $Id: GC.c,v 1.153 2003/04/01 15:05:13 sof Exp $
4 * (c) The GHC Team 1998-2003
6 * Generational garbage collector
8 * ---------------------------------------------------------------------------*/
10 #include "PosixSource.h"
16 #include "StoragePriv.h"
19 #include "SchedAPI.h" // for ReverCAFs prototype
21 #include "BlockAlloc.h"
26 #include "StablePriv.h"
28 #include "ParTicky.h" // ToDo: move into Rts.h
29 #include "GCCompact.h"
31 #if defined(GRAN) || defined(PAR)
32 # include "GranSimRts.h"
33 # include "ParallelRts.h"
37 # include "ParallelDebug.h"
42 #if defined(RTS_GTK_FRONTPANEL)
43 #include "FrontPanel.h"
46 #include "RetainerProfile.h"
47 #include "LdvProfile.h"
51 /* STATIC OBJECT LIST.
54 * We maintain a linked list of static objects that are still live.
55 * The requirements for this list are:
57 * - we need to scan the list while adding to it, in order to
58 * scavenge all the static objects (in the same way that
59 * breadth-first scavenging works for dynamic objects).
61 * - we need to be able to tell whether an object is already on
62 * the list, to break loops.
64 * Each static object has a "static link field", which we use for
65 * linking objects on to the list. We use a stack-type list, consing
66 * objects on the front as they are added (this means that the
67 * scavenge phase is depth-first, not breadth-first, but that
70 * A separate list is kept for objects that have been scavenged
71 * already - this is so that we can zero all the marks afterwards.
73 * An object is on the list if its static link field is non-zero; this
74 * means that we have to mark the end of the list with '1', not NULL.
76 * Extra notes for generational GC:
78 * Each generation has a static object list associated with it. When
79 * collecting generations up to N, we treat the static object lists
80 * from generations > N as roots.
82 * We build up a static object list while collecting generations 0..N,
83 * which is then appended to the static object list of generation N+1.
85 static StgClosure* static_objects; // live static objects
86 StgClosure* scavenged_static_objects; // static objects scavenged so far
88 /* N is the oldest generation being collected, where the generations
89 * are numbered starting at 0. A major GC (indicated by the major_gc
90 * flag) is when we're collecting all generations. We only attempt to
91 * deal with static objects and GC CAFs when doing a major GC.
94 static rtsBool major_gc;
96 /* Youngest generation that objects should be evacuated to in
97 * evacuate(). (Logically an argument to evacuate, but it's static
98 * a lot of the time so we optimise it into a global variable).
104 StgWeak *old_weak_ptr_list; // also pending finaliser list
106 /* Which stage of processing various kinds of weak pointer are we at?
107 * (see traverse_weak_ptr_list() below for discussion).
109 typedef enum { WeakPtrs, WeakThreads, WeakDone } WeakStage;
110 static WeakStage weak_stage;
112 /* List of all threads during GC
114 static StgTSO *old_all_threads;
115 StgTSO *resurrected_threads;
117 /* Flag indicating failure to evacuate an object to the desired
120 static rtsBool failed_to_evac;
122 /* Old to-space (used for two-space collector only)
124 static bdescr *old_to_blocks;
126 /* Data used for allocation area sizing.
128 static lnat new_blocks; // blocks allocated during this GC
129 static lnat g0s0_pcnt_kept = 30; // percentage of g0s0 live at last minor GC
131 /* Used to avoid long recursion due to selector thunks
133 static lnat thunk_selector_depth = 0;
134 #define MAX_THUNK_SELECTOR_DEPTH 8
136 /* -----------------------------------------------------------------------------
137 Static function declarations
138 -------------------------------------------------------------------------- */
140 static bdescr * gc_alloc_block ( step *stp );
141 static void mark_root ( StgClosure **root );
143 // Use a register argument for evacuate, if available.
145 static StgClosure * evacuate (StgClosure *q) __attribute__((regparm(1)));
147 static StgClosure * evacuate (StgClosure *q);
150 static void zero_static_object_list ( StgClosure* first_static );
151 static void zero_mutable_list ( StgMutClosure *first );
153 static rtsBool traverse_weak_ptr_list ( void );
154 static void mark_weak_ptr_list ( StgWeak **list );
156 static StgClosure * eval_thunk_selector ( nat field, StgSelector * p );
159 static void scavenge ( step * );
160 static void scavenge_mark_stack ( void );
161 static void scavenge_stack ( StgPtr p, StgPtr stack_end );
162 static rtsBool scavenge_one ( StgPtr p );
163 static void scavenge_large ( step * );
164 static void scavenge_static ( void );
165 static void scavenge_mutable_list ( generation *g );
166 static void scavenge_mut_once_list ( generation *g );
168 static void scavenge_large_bitmap ( StgPtr p,
169 StgLargeBitmap *large_bitmap,
172 #if 0 && defined(DEBUG)
173 static void gcCAFs ( void );
176 /* -----------------------------------------------------------------------------
177 inline functions etc. for dealing with the mark bitmap & stack.
178 -------------------------------------------------------------------------- */
180 #define MARK_STACK_BLOCKS 4
182 static bdescr *mark_stack_bdescr;
183 static StgPtr *mark_stack;
184 static StgPtr *mark_sp;
185 static StgPtr *mark_splim;
187 // Flag and pointers used for falling back to a linear scan when the
188 // mark stack overflows.
189 static rtsBool mark_stack_overflowed;
190 static bdescr *oldgen_scan_bd;
191 static StgPtr oldgen_scan;
193 static inline rtsBool
194 mark_stack_empty(void)
196 return mark_sp == mark_stack;
199 static inline rtsBool
200 mark_stack_full(void)
202 return mark_sp >= mark_splim;
206 reset_mark_stack(void)
208 mark_sp = mark_stack;
212 push_mark_stack(StgPtr p)
223 /* -----------------------------------------------------------------------------
224 Allocate a new to-space block in the given step.
225 -------------------------------------------------------------------------- */
228 gc_alloc_block(step *stp)
230 bdescr *bd = allocBlock();
231 bd->gen_no = stp->gen_no;
235 // blocks in to-space in generations up to and including N
236 // get the BF_EVACUATED flag.
237 if (stp->gen_no <= N) {
238 bd->flags = BF_EVACUATED;
243 // Start a new to-space block, chain it on after the previous one.
244 if (stp->hp_bd == NULL) {
247 stp->hp_bd->free = stp->hp;
248 stp->hp_bd->link = bd;
253 stp->hpLim = stp->hp + BLOCK_SIZE_W;
261 /* -----------------------------------------------------------------------------
264 Rough outline of the algorithm: for garbage collecting generation N
265 (and all younger generations):
267 - follow all pointers in the root set. the root set includes all
268 mutable objects in all generations (mutable_list and mut_once_list).
270 - for each pointer, evacuate the object it points to into either
272 + to-space of the step given by step->to, which is the next
273 highest step in this generation or the first step in the next
274 generation if this is the last step.
276 + to-space of generations[evac_gen]->steps[0], if evac_gen != 0.
277 When we evacuate an object we attempt to evacuate
278 everything it points to into the same generation - this is
279 achieved by setting evac_gen to the desired generation. If
280 we can't do this, then an entry in the mut_once list has to
281 be made for the cross-generation pointer.
283 + if the object is already in a generation > N, then leave
286 - repeatedly scavenge to-space from each step in each generation
287 being collected until no more objects can be evacuated.
289 - free from-space in each step, and set from-space = to-space.
291 Locks held: sched_mutex
293 -------------------------------------------------------------------------- */
296 GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc )
300 lnat live, allocated, collected = 0, copied = 0;
301 lnat oldgen_saved_blocks = 0;
305 CostCentreStack *prev_CCS;
308 #if defined(DEBUG) && defined(GRAN)
309 IF_DEBUG(gc, belch("@@ Starting garbage collection at %ld (%lx)\n",
313 #if defined(RTS_USER_SIGNALS)
318 // tell the stats department that we've started a GC
321 // Init stats and print par specific (timing) info
322 PAR_TICKY_PAR_START();
324 // attribute any costs to CCS_GC
330 /* Approximate how much we allocated.
331 * Todo: only when generating stats?
333 allocated = calcAllocated();
335 /* Figure out which generation to collect
337 if (force_major_gc) {
338 N = RtsFlags.GcFlags.generations - 1;
342 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
343 if (generations[g].steps[0].n_blocks +
344 generations[g].steps[0].n_large_blocks
345 >= generations[g].max_blocks) {
349 major_gc = (N == RtsFlags.GcFlags.generations-1);
352 #ifdef RTS_GTK_FRONTPANEL
353 if (RtsFlags.GcFlags.frontpanel) {
354 updateFrontPanelBeforeGC(N);
358 // check stack sanity *before* GC (ToDo: check all threads)
360 // ToDo!: check sanity IF_DEBUG(sanity, checkTSOsSanity());
362 IF_DEBUG(sanity, checkFreeListSanity());
364 /* Initialise the static object lists
366 static_objects = END_OF_STATIC_LIST;
367 scavenged_static_objects = END_OF_STATIC_LIST;
369 /* zero the mutable list for the oldest generation (see comment by
370 * zero_mutable_list below).
373 zero_mutable_list(generations[RtsFlags.GcFlags.generations-1].mut_once_list);
376 /* Save the old to-space if we're doing a two-space collection
378 if (RtsFlags.GcFlags.generations == 1) {
379 old_to_blocks = g0s0->to_blocks;
380 g0s0->to_blocks = NULL;
383 /* Keep a count of how many new blocks we allocated during this GC
384 * (used for resizing the allocation area, later).
388 // Initialise to-space in all the generations/steps that we're
391 for (g = 0; g <= N; g++) {
392 generations[g].mut_once_list = END_MUT_LIST;
393 generations[g].mut_list = END_MUT_LIST;
395 for (s = 0; s < generations[g].n_steps; s++) {
397 // generation 0, step 0 doesn't need to-space
398 if (g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1) {
402 stp = &generations[g].steps[s];
403 ASSERT(stp->gen_no == g);
405 // start a new to-space for this step.
408 stp->to_blocks = NULL;
410 // allocate the first to-space block; extra blocks will be
411 // chained on as necessary.
412 bd = gc_alloc_block(stp);
414 stp->scan = bd->start;
417 // initialise the large object queues.
418 stp->new_large_objects = NULL;
419 stp->scavenged_large_objects = NULL;
420 stp->n_scavenged_large_blocks = 0;
422 // mark the large objects as not evacuated yet
423 for (bd = stp->large_objects; bd; bd = bd->link) {
424 bd->flags = BF_LARGE;
427 // for a compacted step, we need to allocate the bitmap
428 if (stp->is_compacted) {
429 nat bitmap_size; // in bytes
430 bdescr *bitmap_bdescr;
433 bitmap_size = stp->n_blocks * BLOCK_SIZE / (sizeof(W_)*BITS_PER_BYTE);
435 if (bitmap_size > 0) {
436 bitmap_bdescr = allocGroup((nat)BLOCK_ROUND_UP(bitmap_size)
438 stp->bitmap = bitmap_bdescr;
439 bitmap = bitmap_bdescr->start;
441 IF_DEBUG(gc, belch("bitmap_size: %d, bitmap: %p",
442 bitmap_size, bitmap););
444 // don't forget to fill it with zeros!
445 memset(bitmap, 0, bitmap_size);
447 // for each block in this step, point to its bitmap from the
449 for (bd=stp->blocks; bd != NULL; bd = bd->link) {
450 bd->u.bitmap = bitmap;
451 bitmap += BLOCK_SIZE_W / (sizeof(W_)*BITS_PER_BYTE);
458 /* make sure the older generations have at least one block to
459 * allocate into (this makes things easier for copy(), see below).
461 for (g = N+1; g < RtsFlags.GcFlags.generations; g++) {
462 for (s = 0; s < generations[g].n_steps; s++) {
463 stp = &generations[g].steps[s];
464 if (stp->hp_bd == NULL) {
465 ASSERT(stp->blocks == NULL);
466 bd = gc_alloc_block(stp);
470 /* Set the scan pointer for older generations: remember we
471 * still have to scavenge objects that have been promoted. */
473 stp->scan_bd = stp->hp_bd;
474 stp->to_blocks = NULL;
475 stp->n_to_blocks = 0;
476 stp->new_large_objects = NULL;
477 stp->scavenged_large_objects = NULL;
478 stp->n_scavenged_large_blocks = 0;
482 /* Allocate a mark stack if we're doing a major collection.
485 mark_stack_bdescr = allocGroup(MARK_STACK_BLOCKS);
486 mark_stack = (StgPtr *)mark_stack_bdescr->start;
487 mark_sp = mark_stack;
488 mark_splim = mark_stack + (MARK_STACK_BLOCKS * BLOCK_SIZE_W);
490 mark_stack_bdescr = NULL;
493 /* -----------------------------------------------------------------------
494 * follow all the roots that we know about:
495 * - mutable lists from each generation > N
496 * we want to *scavenge* these roots, not evacuate them: they're not
497 * going to move in this GC.
498 * Also: do them in reverse generation order. This is because we
499 * often want to promote objects that are pointed to by older
500 * generations early, so we don't have to repeatedly copy them.
501 * Doing the generations in reverse order ensures that we don't end
502 * up in the situation where we want to evac an object to gen 3 and
503 * it has already been evaced to gen 2.
507 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
508 generations[g].saved_mut_list = generations[g].mut_list;
509 generations[g].mut_list = END_MUT_LIST;
512 // Do the mut-once lists first
513 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
514 IF_PAR_DEBUG(verbose,
515 printMutOnceList(&generations[g]));
516 scavenge_mut_once_list(&generations[g]);
518 for (st = generations[g].n_steps-1; st >= 0; st--) {
519 scavenge(&generations[g].steps[st]);
523 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
524 IF_PAR_DEBUG(verbose,
525 printMutableList(&generations[g]));
526 scavenge_mutable_list(&generations[g]);
528 for (st = generations[g].n_steps-1; st >= 0; st--) {
529 scavenge(&generations[g].steps[st]);
534 /* follow roots from the CAF list (used by GHCi)
539 /* follow all the roots that the application knows about.
542 get_roots(mark_root);
545 /* And don't forget to mark the TSO if we got here direct from
547 /* Not needed in a seq version?
549 CurrentTSO = (StgTSO *)MarkRoot((StgClosure *)CurrentTSO);
553 // Mark the entries in the GALA table of the parallel system
554 markLocalGAs(major_gc);
555 // Mark all entries on the list of pending fetches
556 markPendingFetches(major_gc);
559 /* Mark the weak pointer list, and prepare to detect dead weak
562 mark_weak_ptr_list(&weak_ptr_list);
563 old_weak_ptr_list = weak_ptr_list;
564 weak_ptr_list = NULL;
565 weak_stage = WeakPtrs;
567 /* The all_threads list is like the weak_ptr_list.
568 * See traverse_weak_ptr_list() for the details.
570 old_all_threads = all_threads;
571 all_threads = END_TSO_QUEUE;
572 resurrected_threads = END_TSO_QUEUE;
574 /* Mark the stable pointer table.
576 markStablePtrTable(mark_root);
580 /* ToDo: To fix the caf leak, we need to make the commented out
581 * parts of this code do something sensible - as described in
584 extern void markHugsObjects(void);
589 /* -------------------------------------------------------------------------
590 * Repeatedly scavenge all the areas we know about until there's no
591 * more scavenging to be done.
598 // scavenge static objects
599 if (major_gc && static_objects != END_OF_STATIC_LIST) {
600 IF_DEBUG(sanity, checkStaticObjects(static_objects));
604 /* When scavenging the older generations: Objects may have been
605 * evacuated from generations <= N into older generations, and we
606 * need to scavenge these objects. We're going to try to ensure that
607 * any evacuations that occur move the objects into at least the
608 * same generation as the object being scavenged, otherwise we
609 * have to create new entries on the mutable list for the older
613 // scavenge each step in generations 0..maxgen
619 // scavenge objects in compacted generation
620 if (mark_stack_overflowed || oldgen_scan_bd != NULL ||
621 (mark_stack_bdescr != NULL && !mark_stack_empty())) {
622 scavenge_mark_stack();
626 for (gen = RtsFlags.GcFlags.generations; --gen >= 0; ) {
627 for (st = generations[gen].n_steps; --st >= 0; ) {
628 if (gen == 0 && st == 0 && RtsFlags.GcFlags.generations > 1) {
631 stp = &generations[gen].steps[st];
633 if (stp->hp_bd != stp->scan_bd || stp->scan < stp->hp) {
638 if (stp->new_large_objects != NULL) {
647 if (flag) { goto loop; }
649 // must be last... invariant is that everything is fully
650 // scavenged at this point.
651 if (traverse_weak_ptr_list()) { // returns rtsTrue if evaced something
656 /* Update the pointers from the "main thread" list - these are
657 * treated as weak pointers because we want to allow a main thread
658 * to get a BlockedOnDeadMVar exception in the same way as any other
659 * thread. Note that the threads should all have been retained by
660 * GC by virtue of being on the all_threads list, we're just
661 * updating pointers here.
666 for (m = main_threads; m != NULL; m = m->link) {
667 tso = (StgTSO *) isAlive((StgClosure *)m->tso);
669 barf("main thread has been GC'd");
676 // Reconstruct the Global Address tables used in GUM
677 rebuildGAtables(major_gc);
678 IF_DEBUG(sanity, checkLAGAtable(rtsTrue/*check closures, too*/));
681 // Now see which stable names are still alive.
684 // Tidy the end of the to-space chains
685 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
686 for (s = 0; s < generations[g].n_steps; s++) {
687 stp = &generations[g].steps[s];
688 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
689 ASSERT(Bdescr(stp->hp) == stp->hp_bd);
690 stp->hp_bd->free = stp->hp;
696 // We call processHeapClosureForDead() on every closure destroyed during
697 // the current garbage collection, so we invoke LdvCensusForDead().
698 if (RtsFlags.ProfFlags.doHeapProfile == HEAP_BY_LDV
699 || RtsFlags.ProfFlags.bioSelector != NULL)
703 // NO MORE EVACUATION AFTER THIS POINT!
704 // Finally: compaction of the oldest generation.
705 if (major_gc && oldest_gen->steps[0].is_compacted) {
706 // save number of blocks for stats
707 oldgen_saved_blocks = oldest_gen->steps[0].n_blocks;
711 IF_DEBUG(sanity, checkGlobalTSOList(rtsFalse));
713 /* run through all the generations/steps and tidy up
715 copied = new_blocks * BLOCK_SIZE_W;
716 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
719 generations[g].collections++; // for stats
722 for (s = 0; s < generations[g].n_steps; s++) {
724 stp = &generations[g].steps[s];
726 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
727 // stats information: how much we copied
729 copied -= stp->hp_bd->start + BLOCK_SIZE_W -
734 // for generations we collected...
737 // rough calculation of garbage collected, for stats output
738 if (stp->is_compacted) {
739 collected += (oldgen_saved_blocks - stp->n_blocks) * BLOCK_SIZE_W;
741 collected += stp->n_blocks * BLOCK_SIZE_W;
744 /* free old memory and shift to-space into from-space for all
745 * the collected steps (except the allocation area). These
746 * freed blocks will probaby be quickly recycled.
748 if (!(g == 0 && s == 0)) {
749 if (stp->is_compacted) {
750 // for a compacted step, just shift the new to-space
751 // onto the front of the now-compacted existing blocks.
752 for (bd = stp->to_blocks; bd != NULL; bd = bd->link) {
753 bd->flags &= ~BF_EVACUATED; // now from-space
755 // tack the new blocks on the end of the existing blocks
756 if (stp->blocks == NULL) {
757 stp->blocks = stp->to_blocks;
759 for (bd = stp->blocks; bd != NULL; bd = next) {
762 bd->link = stp->to_blocks;
766 // add the new blocks to the block tally
767 stp->n_blocks += stp->n_to_blocks;
769 freeChain(stp->blocks);
770 stp->blocks = stp->to_blocks;
771 stp->n_blocks = stp->n_to_blocks;
772 for (bd = stp->blocks; bd != NULL; bd = bd->link) {
773 bd->flags &= ~BF_EVACUATED; // now from-space
776 stp->to_blocks = NULL;
777 stp->n_to_blocks = 0;
780 /* LARGE OBJECTS. The current live large objects are chained on
781 * scavenged_large, having been moved during garbage
782 * collection from large_objects. Any objects left on
783 * large_objects list are therefore dead, so we free them here.
785 for (bd = stp->large_objects; bd != NULL; bd = next) {
791 // update the count of blocks used by large objects
792 for (bd = stp->scavenged_large_objects; bd != NULL; bd = bd->link) {
793 bd->flags &= ~BF_EVACUATED;
795 stp->large_objects = stp->scavenged_large_objects;
796 stp->n_large_blocks = stp->n_scavenged_large_blocks;
799 // for older generations...
801 /* For older generations, we need to append the
802 * scavenged_large_object list (i.e. large objects that have been
803 * promoted during this GC) to the large_object list for that step.
805 for (bd = stp->scavenged_large_objects; bd; bd = next) {
807 bd->flags &= ~BF_EVACUATED;
808 dbl_link_onto(bd, &stp->large_objects);
811 // add the new blocks we promoted during this GC
812 stp->n_blocks += stp->n_to_blocks;
813 stp->n_to_blocks = 0;
814 stp->n_large_blocks += stp->n_scavenged_large_blocks;
819 /* Reset the sizes of the older generations when we do a major
822 * CURRENT STRATEGY: make all generations except zero the same size.
823 * We have to stay within the maximum heap size, and leave a certain
824 * percentage of the maximum heap size available to allocate into.
826 if (major_gc && RtsFlags.GcFlags.generations > 1) {
827 nat live, size, min_alloc;
828 nat max = RtsFlags.GcFlags.maxHeapSize;
829 nat gens = RtsFlags.GcFlags.generations;
831 // live in the oldest generations
832 live = oldest_gen->steps[0].n_blocks +
833 oldest_gen->steps[0].n_large_blocks;
835 // default max size for all generations except zero
836 size = stg_max(live * RtsFlags.GcFlags.oldGenFactor,
837 RtsFlags.GcFlags.minOldGenSize);
839 // minimum size for generation zero
840 min_alloc = stg_max((RtsFlags.GcFlags.pcFreeHeap * max) / 200,
841 RtsFlags.GcFlags.minAllocAreaSize);
843 // Auto-enable compaction when the residency reaches a
844 // certain percentage of the maximum heap size (default: 30%).
845 if (RtsFlags.GcFlags.generations > 1 &&
846 (RtsFlags.GcFlags.compact ||
848 oldest_gen->steps[0].n_blocks >
849 (RtsFlags.GcFlags.compactThreshold * max) / 100))) {
850 oldest_gen->steps[0].is_compacted = 1;
851 // fprintf(stderr,"compaction: on\n", live);
853 oldest_gen->steps[0].is_compacted = 0;
854 // fprintf(stderr,"compaction: off\n", live);
857 // if we're going to go over the maximum heap size, reduce the
858 // size of the generations accordingly. The calculation is
859 // different if compaction is turned on, because we don't need
860 // to double the space required to collect the old generation.
863 // this test is necessary to ensure that the calculations
864 // below don't have any negative results - we're working
865 // with unsigned values here.
866 if (max < min_alloc) {
870 if (oldest_gen->steps[0].is_compacted) {
871 if ( (size + (size - 1) * (gens - 2) * 2) + min_alloc > max ) {
872 size = (max - min_alloc) / ((gens - 1) * 2 - 1);
875 if ( (size * (gens - 1) * 2) + min_alloc > max ) {
876 size = (max - min_alloc) / ((gens - 1) * 2);
886 fprintf(stderr,"live: %d, min_alloc: %d, size : %d, max = %d\n", live,
887 min_alloc, size, max);
890 for (g = 0; g < gens; g++) {
891 generations[g].max_blocks = size;
895 // Guess the amount of live data for stats.
898 /* Free the small objects allocated via allocate(), since this will
899 * all have been copied into G0S1 now.
901 if (small_alloc_list != NULL) {
902 freeChain(small_alloc_list);
904 small_alloc_list = NULL;
908 alloc_blocks_lim = RtsFlags.GcFlags.minAllocAreaSize;
910 // Start a new pinned_object_block
911 pinned_object_block = NULL;
913 /* Free the mark stack.
915 if (mark_stack_bdescr != NULL) {
916 freeGroup(mark_stack_bdescr);
921 for (g = 0; g <= N; g++) {
922 for (s = 0; s < generations[g].n_steps; s++) {
923 stp = &generations[g].steps[s];
924 if (stp->is_compacted && stp->bitmap != NULL) {
925 freeGroup(stp->bitmap);
930 /* Two-space collector:
931 * Free the old to-space, and estimate the amount of live data.
933 if (RtsFlags.GcFlags.generations == 1) {
936 if (old_to_blocks != NULL) {
937 freeChain(old_to_blocks);
939 for (bd = g0s0->to_blocks; bd != NULL; bd = bd->link) {
940 bd->flags = 0; // now from-space
943 /* For a two-space collector, we need to resize the nursery. */
945 /* set up a new nursery. Allocate a nursery size based on a
946 * function of the amount of live data (by default a factor of 2)
947 * Use the blocks from the old nursery if possible, freeing up any
950 * If we get near the maximum heap size, then adjust our nursery
951 * size accordingly. If the nursery is the same size as the live
952 * data (L), then we need 3L bytes. We can reduce the size of the
953 * nursery to bring the required memory down near 2L bytes.
955 * A normal 2-space collector would need 4L bytes to give the same
956 * performance we get from 3L bytes, reducing to the same
957 * performance at 2L bytes.
959 blocks = g0s0->n_to_blocks;
961 if ( RtsFlags.GcFlags.maxHeapSize != 0 &&
962 blocks * RtsFlags.GcFlags.oldGenFactor * 2 >
963 RtsFlags.GcFlags.maxHeapSize ) {
964 long adjusted_blocks; // signed on purpose
967 adjusted_blocks = (RtsFlags.GcFlags.maxHeapSize - 2 * blocks);
968 IF_DEBUG(gc, belch("@@ Near maximum heap size of 0x%x blocks, blocks = %d, adjusted to %ld", RtsFlags.GcFlags.maxHeapSize, blocks, adjusted_blocks));
969 pc_free = adjusted_blocks * 100 / RtsFlags.GcFlags.maxHeapSize;
970 if (pc_free < RtsFlags.GcFlags.pcFreeHeap) /* might even be < 0 */ {
973 blocks = adjusted_blocks;
976 blocks *= RtsFlags.GcFlags.oldGenFactor;
977 if (blocks < RtsFlags.GcFlags.minAllocAreaSize) {
978 blocks = RtsFlags.GcFlags.minAllocAreaSize;
981 resizeNursery(blocks);
984 /* Generational collector:
985 * If the user has given us a suggested heap size, adjust our
986 * allocation area to make best use of the memory available.
989 if (RtsFlags.GcFlags.heapSizeSuggestion) {
991 nat needed = calcNeeded(); // approx blocks needed at next GC
993 /* Guess how much will be live in generation 0 step 0 next time.
994 * A good approximation is obtained by finding the
995 * percentage of g0s0 that was live at the last minor GC.
998 g0s0_pcnt_kept = (new_blocks * 100) / g0s0->n_blocks;
1001 /* Estimate a size for the allocation area based on the
1002 * information available. We might end up going slightly under
1003 * or over the suggested heap size, but we should be pretty
1006 * Formula: suggested - needed
1007 * ----------------------------
1008 * 1 + g0s0_pcnt_kept/100
1010 * where 'needed' is the amount of memory needed at the next
1011 * collection for collecting all steps except g0s0.
1014 (((long)RtsFlags.GcFlags.heapSizeSuggestion - (long)needed) * 100) /
1015 (100 + (long)g0s0_pcnt_kept);
1017 if (blocks < (long)RtsFlags.GcFlags.minAllocAreaSize) {
1018 blocks = RtsFlags.GcFlags.minAllocAreaSize;
1021 resizeNursery((nat)blocks);
1024 // we might have added extra large blocks to the nursery, so
1025 // resize back to minAllocAreaSize again.
1026 resizeNursery(RtsFlags.GcFlags.minAllocAreaSize);
1030 // mark the garbage collected CAFs as dead
1031 #if 0 && defined(DEBUG) // doesn't work at the moment
1032 if (major_gc) { gcCAFs(); }
1036 // resetStaticObjectForRetainerProfiling() must be called before
1038 resetStaticObjectForRetainerProfiling();
1041 // zero the scavenged static object list
1043 zero_static_object_list(scavenged_static_objects);
1046 // Reset the nursery
1049 RELEASE_LOCK(&sched_mutex);
1051 // start any pending finalizers
1052 scheduleFinalizers(old_weak_ptr_list);
1054 // send exceptions to any threads which were about to die
1055 resurrectThreads(resurrected_threads);
1057 ACQUIRE_LOCK(&sched_mutex);
1059 // Update the stable pointer hash table.
1060 updateStablePtrTable(major_gc);
1062 // check sanity after GC
1063 IF_DEBUG(sanity, checkSanity());
1065 // extra GC trace info
1066 IF_DEBUG(gc, statDescribeGens());
1069 // symbol-table based profiling
1070 /* heapCensus(to_blocks); */ /* ToDo */
1073 // restore enclosing cost centre
1078 // check for memory leaks if sanity checking is on
1079 IF_DEBUG(sanity, memInventory());
1081 #ifdef RTS_GTK_FRONTPANEL
1082 if (RtsFlags.GcFlags.frontpanel) {
1083 updateFrontPanelAfterGC( N, live );
1087 // ok, GC over: tell the stats department what happened.
1088 stat_endGC(allocated, collected, live, copied, N);
1090 #if defined(RTS_USER_SIGNALS)
1091 // unblock signals again
1092 unblockUserSignals();
1099 /* -----------------------------------------------------------------------------
1102 traverse_weak_ptr_list is called possibly many times during garbage
1103 collection. It returns a flag indicating whether it did any work
1104 (i.e. called evacuate on any live pointers).
1106 Invariant: traverse_weak_ptr_list is called when the heap is in an
1107 idempotent state. That means that there are no pending
1108 evacuate/scavenge operations. This invariant helps the weak
1109 pointer code decide which weak pointers are dead - if there are no
1110 new live weak pointers, then all the currently unreachable ones are
1113 For generational GC: we just don't try to finalize weak pointers in
1114 older generations than the one we're collecting. This could
1115 probably be optimised by keeping per-generation lists of weak
1116 pointers, but for a few weak pointers this scheme will work.
1118 There are three distinct stages to processing weak pointers:
1120 - weak_stage == WeakPtrs
1122 We process all the weak pointers whos keys are alive (evacuate
1123 their values and finalizers), and repeat until we can find no new
1124 live keys. If no live keys are found in this pass, then we
1125 evacuate the finalizers of all the dead weak pointers in order to
1128 - weak_stage == WeakThreads
1130 Now, we discover which *threads* are still alive. Pointers to
1131 threads from the all_threads and main thread lists are the
1132 weakest of all: a pointers from the finalizer of a dead weak
1133 pointer can keep a thread alive. Any threads found to be unreachable
1134 are evacuated and placed on the resurrected_threads list so we
1135 can send them a signal later.
1137 - weak_stage == WeakDone
1139 No more evacuation is done.
1141 -------------------------------------------------------------------------- */
1144 traverse_weak_ptr_list(void)
1146 StgWeak *w, **last_w, *next_w;
1148 rtsBool flag = rtsFalse;
1150 switch (weak_stage) {
1156 /* doesn't matter where we evacuate values/finalizers to, since
1157 * these pointers are treated as roots (iff the keys are alive).
1161 last_w = &old_weak_ptr_list;
1162 for (w = old_weak_ptr_list; w != NULL; w = next_w) {
1164 /* There might be a DEAD_WEAK on the list if finalizeWeak# was
1165 * called on a live weak pointer object. Just remove it.
1167 if (w->header.info == &stg_DEAD_WEAK_info) {
1168 next_w = ((StgDeadWeak *)w)->link;
1173 switch (get_itbl(w)->type) {
1176 next_w = (StgWeak *)((StgEvacuated *)w)->evacuee;
1181 /* Now, check whether the key is reachable.
1183 new = isAlive(w->key);
1186 // evacuate the value and finalizer
1187 w->value = evacuate(w->value);
1188 w->finalizer = evacuate(w->finalizer);
1189 // remove this weak ptr from the old_weak_ptr list
1191 // and put it on the new weak ptr list
1193 w->link = weak_ptr_list;
1196 IF_DEBUG(weak, belch("Weak pointer still alive at %p -> %p",
1201 last_w = &(w->link);
1207 barf("traverse_weak_ptr_list: not WEAK");
1211 /* If we didn't make any changes, then we can go round and kill all
1212 * the dead weak pointers. The old_weak_ptr list is used as a list
1213 * of pending finalizers later on.
1215 if (flag == rtsFalse) {
1216 for (w = old_weak_ptr_list; w; w = w->link) {
1217 w->finalizer = evacuate(w->finalizer);
1220 // Next, move to the WeakThreads stage after fully
1221 // scavenging the finalizers we've just evacuated.
1222 weak_stage = WeakThreads;
1228 /* Now deal with the all_threads list, which behaves somewhat like
1229 * the weak ptr list. If we discover any threads that are about to
1230 * become garbage, we wake them up and administer an exception.
1233 StgTSO *t, *tmp, *next, **prev;
1235 prev = &old_all_threads;
1236 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1238 (StgClosure *)tmp = isAlive((StgClosure *)t);
1244 ASSERT(get_itbl(t)->type == TSO);
1245 switch (t->what_next) {
1246 case ThreadRelocated:
1251 case ThreadComplete:
1252 // finshed or died. The thread might still be alive, but we
1253 // don't keep it on the all_threads list. Don't forget to
1254 // stub out its global_link field.
1255 next = t->global_link;
1256 t->global_link = END_TSO_QUEUE;
1264 // not alive (yet): leave this thread on the
1265 // old_all_threads list.
1266 prev = &(t->global_link);
1267 next = t->global_link;
1270 // alive: move this thread onto the all_threads list.
1271 next = t->global_link;
1272 t->global_link = all_threads;
1279 /* And resurrect any threads which were about to become garbage.
1282 StgTSO *t, *tmp, *next;
1283 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1284 next = t->global_link;
1285 (StgClosure *)tmp = evacuate((StgClosure *)t);
1286 tmp->global_link = resurrected_threads;
1287 resurrected_threads = tmp;
1291 weak_stage = WeakDone; // *now* we're done,
1292 return rtsTrue; // but one more round of scavenging, please
1295 barf("traverse_weak_ptr_list");
1300 /* -----------------------------------------------------------------------------
1301 After GC, the live weak pointer list may have forwarding pointers
1302 on it, because a weak pointer object was evacuated after being
1303 moved to the live weak pointer list. We remove those forwarding
1306 Also, we don't consider weak pointer objects to be reachable, but
1307 we must nevertheless consider them to be "live" and retain them.
1308 Therefore any weak pointer objects which haven't as yet been
1309 evacuated need to be evacuated now.
1310 -------------------------------------------------------------------------- */
1314 mark_weak_ptr_list ( StgWeak **list )
1316 StgWeak *w, **last_w;
1319 for (w = *list; w; w = w->link) {
1320 // w might be WEAK, EVACUATED, or DEAD_WEAK (actually CON_STATIC) here
1321 ASSERT(w->header.info == &stg_DEAD_WEAK_info
1322 || get_itbl(w)->type == WEAK || get_itbl(w)->type == EVACUATED);
1323 (StgClosure *)w = evacuate((StgClosure *)w);
1325 last_w = &(w->link);
1329 /* -----------------------------------------------------------------------------
1330 isAlive determines whether the given closure is still alive (after
1331 a garbage collection) or not. It returns the new address of the
1332 closure if it is alive, or NULL otherwise.
1334 NOTE: Use it before compaction only!
1335 -------------------------------------------------------------------------- */
1339 isAlive(StgClosure *p)
1341 const StgInfoTable *info;
1346 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
1349 // ignore static closures
1351 // ToDo: for static closures, check the static link field.
1352 // Problem here is that we sometimes don't set the link field, eg.
1353 // for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
1355 if (!HEAP_ALLOCED(p)) {
1359 // ignore closures in generations that we're not collecting.
1361 if (bd->gen_no > N) {
1365 // if it's a pointer into to-space, then we're done
1366 if (bd->flags & BF_EVACUATED) {
1370 // large objects use the evacuated flag
1371 if (bd->flags & BF_LARGE) {
1375 // check the mark bit for compacted steps
1376 if (bd->step->is_compacted && is_marked((P_)p,bd)) {
1380 switch (info->type) {
1385 case IND_OLDGEN: // rely on compatible layout with StgInd
1386 case IND_OLDGEN_PERM:
1387 // follow indirections
1388 p = ((StgInd *)p)->indirectee;
1393 return ((StgEvacuated *)p)->evacuee;
1396 if (((StgTSO *)p)->what_next == ThreadRelocated) {
1397 p = (StgClosure *)((StgTSO *)p)->link;
1410 mark_root(StgClosure **root)
1412 *root = evacuate(*root);
1415 static __inline__ void
1416 upd_evacuee(StgClosure *p, StgClosure *dest)
1418 // Source object must be in from-space:
1419 ASSERT((Bdescr((P_)p)->flags & BF_EVACUATED) == 0);
1420 // not true: (ToDo: perhaps it should be)
1421 // ASSERT(Bdescr((P_)dest)->flags & BF_EVACUATED);
1422 p->header.info = &stg_EVACUATED_info;
1423 ((StgEvacuated *)p)->evacuee = dest;
1427 static __inline__ StgClosure *
1428 copy(StgClosure *src, nat size, step *stp)
1433 nat size_org = size;
1436 TICK_GC_WORDS_COPIED(size);
1437 /* Find out where we're going, using the handy "to" pointer in
1438 * the step of the source object. If it turns out we need to
1439 * evacuate to an older generation, adjust it here (see comment
1442 if (stp->gen_no < evac_gen) {
1443 #ifdef NO_EAGER_PROMOTION
1444 failed_to_evac = rtsTrue;
1446 stp = &generations[evac_gen].steps[0];
1450 /* chain a new block onto the to-space for the destination step if
1453 if (stp->hp + size >= stp->hpLim) {
1454 gc_alloc_block(stp);
1457 for(to = stp->hp, from = (P_)src; size>0; --size) {
1463 upd_evacuee(src,(StgClosure *)dest);
1465 // We store the size of the just evacuated object in the LDV word so that
1466 // the profiler can guess the position of the next object later.
1467 SET_EVACUAEE_FOR_LDV(src, size_org);
1469 return (StgClosure *)dest;
1472 /* Special version of copy() for when we only want to copy the info
1473 * pointer of an object, but reserve some padding after it. This is
1474 * used to optimise evacuation of BLACKHOLEs.
1479 copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *stp)
1484 nat size_to_copy_org = size_to_copy;
1487 TICK_GC_WORDS_COPIED(size_to_copy);
1488 if (stp->gen_no < evac_gen) {
1489 #ifdef NO_EAGER_PROMOTION
1490 failed_to_evac = rtsTrue;
1492 stp = &generations[evac_gen].steps[0];
1496 if (stp->hp + size_to_reserve >= stp->hpLim) {
1497 gc_alloc_block(stp);
1500 for(to = stp->hp, from = (P_)src; size_to_copy>0; --size_to_copy) {
1505 stp->hp += size_to_reserve;
1506 upd_evacuee(src,(StgClosure *)dest);
1508 // We store the size of the just evacuated object in the LDV word so that
1509 // the profiler can guess the position of the next object later.
1510 // size_to_copy_org is wrong because the closure already occupies size_to_reserve
1512 SET_EVACUAEE_FOR_LDV(src, size_to_reserve);
1514 if (size_to_reserve - size_to_copy_org > 0)
1515 FILL_SLOP(stp->hp - 1, (int)(size_to_reserve - size_to_copy_org));
1517 return (StgClosure *)dest;
1521 /* -----------------------------------------------------------------------------
1522 Evacuate a large object
1524 This just consists of removing the object from the (doubly-linked)
1525 step->large_objects list, and linking it on to the (singly-linked)
1526 step->new_large_objects list, from where it will be scavenged later.
1528 Convention: bd->flags has BF_EVACUATED set for a large object
1529 that has been evacuated, or unset otherwise.
1530 -------------------------------------------------------------------------- */
1534 evacuate_large(StgPtr p)
1536 bdescr *bd = Bdescr(p);
1539 // object must be at the beginning of the block (or be a ByteArray)
1540 ASSERT(get_itbl((StgClosure *)p)->type == ARR_WORDS ||
1541 (((W_)p & BLOCK_MASK) == 0));
1543 // already evacuated?
1544 if (bd->flags & BF_EVACUATED) {
1545 /* Don't forget to set the failed_to_evac flag if we didn't get
1546 * the desired destination (see comments in evacuate()).
1548 if (bd->gen_no < evac_gen) {
1549 failed_to_evac = rtsTrue;
1550 TICK_GC_FAILED_PROMOTION();
1556 // remove from large_object list
1558 bd->u.back->link = bd->link;
1559 } else { // first object in the list
1560 stp->large_objects = bd->link;
1563 bd->link->u.back = bd->u.back;
1566 /* link it on to the evacuated large object list of the destination step
1569 if (stp->gen_no < evac_gen) {
1570 #ifdef NO_EAGER_PROMOTION
1571 failed_to_evac = rtsTrue;
1573 stp = &generations[evac_gen].steps[0];
1578 bd->gen_no = stp->gen_no;
1579 bd->link = stp->new_large_objects;
1580 stp->new_large_objects = bd;
1581 bd->flags |= BF_EVACUATED;
1584 /* -----------------------------------------------------------------------------
1585 Adding a MUT_CONS to an older generation.
1587 This is necessary from time to time when we end up with an
1588 old-to-new generation pointer in a non-mutable object. We defer
1589 the promotion until the next GC.
1590 -------------------------------------------------------------------------- */
1593 mkMutCons(StgClosure *ptr, generation *gen)
1598 stp = &gen->steps[0];
1600 /* chain a new block onto the to-space for the destination step if
1603 if (stp->hp + sizeofW(StgIndOldGen) >= stp->hpLim) {
1604 gc_alloc_block(stp);
1607 q = (StgMutVar *)stp->hp;
1608 stp->hp += sizeofW(StgMutVar);
1610 SET_HDR(q,&stg_MUT_CONS_info,CCS_GC);
1612 recordOldToNewPtrs((StgMutClosure *)q);
1614 return (StgClosure *)q;
1617 /* -----------------------------------------------------------------------------
1620 This is called (eventually) for every live object in the system.
1622 The caller to evacuate specifies a desired generation in the
1623 evac_gen global variable. The following conditions apply to
1624 evacuating an object which resides in generation M when we're
1625 collecting up to generation N
1629 else evac to step->to
1631 if M < evac_gen evac to evac_gen, step 0
1633 if the object is already evacuated, then we check which generation
1636 if M >= evac_gen do nothing
1637 if M < evac_gen set failed_to_evac flag to indicate that we
1638 didn't manage to evacuate this object into evac_gen.
1640 -------------------------------------------------------------------------- */
1643 evacuate(StgClosure *q)
1648 const StgInfoTable *info;
1651 if (HEAP_ALLOCED(q)) {
1654 if (bd->gen_no > N) {
1655 /* Can't evacuate this object, because it's in a generation
1656 * older than the ones we're collecting. Let's hope that it's
1657 * in evac_gen or older, or we will have to arrange to track
1658 * this pointer using the mutable list.
1660 if (bd->gen_no < evac_gen) {
1662 failed_to_evac = rtsTrue;
1663 TICK_GC_FAILED_PROMOTION();
1668 /* evacuate large objects by re-linking them onto a different list.
1670 if (bd->flags & BF_LARGE) {
1672 if (info->type == TSO &&
1673 ((StgTSO *)q)->what_next == ThreadRelocated) {
1674 q = (StgClosure *)((StgTSO *)q)->link;
1677 evacuate_large((P_)q);
1681 /* If the object is in a step that we're compacting, then we
1682 * need to use an alternative evacuate procedure.
1684 if (bd->step->is_compacted) {
1685 if (!is_marked((P_)q,bd)) {
1687 if (mark_stack_full()) {
1688 mark_stack_overflowed = rtsTrue;
1691 push_mark_stack((P_)q);
1699 else stp = NULL; // make sure copy() will crash if HEAP_ALLOCED is wrong
1702 // make sure the info pointer is into text space
1703 ASSERT(LOOKS_LIKE_CLOSURE_PTR(q));
1706 switch (info -> type) {
1710 return copy(q,sizeW_fromITBL(info),stp);
1714 StgWord w = (StgWord)q->payload[0];
1715 if (q->header.info == Czh_con_info &&
1716 // unsigned, so always true: (StgChar)w >= MIN_CHARLIKE &&
1717 (StgChar)w <= MAX_CHARLIKE) {
1718 return (StgClosure *)CHARLIKE_CLOSURE((StgChar)w);
1720 if (q->header.info == Izh_con_info &&
1721 (StgInt)w >= MIN_INTLIKE && (StgInt)w <= MAX_INTLIKE) {
1722 return (StgClosure *)INTLIKE_CLOSURE((StgInt)w);
1724 // else, fall through ...
1730 return copy(q,sizeofW(StgHeader)+1,stp);
1732 case THUNK_1_0: // here because of MIN_UPD_SIZE
1737 #ifdef NO_PROMOTE_THUNKS
1738 if (bd->gen_no == 0 &&
1739 bd->step->no != 0 &&
1740 bd->step->no == generations[bd->gen_no].n_steps-1) {
1744 return copy(q,sizeofW(StgHeader)+2,stp);
1752 return copy(q,sizeofW(StgHeader)+2,stp);
1758 case IND_OLDGEN_PERM:
1762 return copy(q,sizeW_fromITBL(info),stp);
1765 return copy(q,bco_sizeW((StgBCO *)q),stp);
1768 case SE_CAF_BLACKHOLE:
1771 return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
1774 to = copy(q,BLACKHOLE_sizeW(),stp);
1777 case THUNK_SELECTOR:
1781 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
1782 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1785 p = eval_thunk_selector(info->layout.selector_offset,
1789 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1791 // q is still BLACKHOLE'd.
1792 thunk_selector_depth++;
1794 thunk_selector_depth--;
1797 // We store the size of the just evacuated object in the
1798 // LDV word so that the profiler can guess the position of
1799 // the next object later.
1800 SET_EVACUAEE_FOR_LDV(q, THUNK_SELECTOR_sizeW());
1808 // follow chains of indirections, don't evacuate them
1809 q = ((StgInd*)q)->indirectee;
1813 if (info->srt_len > 0 && major_gc &&
1814 THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
1815 THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
1816 static_objects = (StgClosure *)q;
1821 if (info->srt_len > 0 && major_gc &&
1822 FUN_STATIC_LINK((StgClosure *)q) == NULL) {
1823 FUN_STATIC_LINK((StgClosure *)q) = static_objects;
1824 static_objects = (StgClosure *)q;
1829 /* If q->saved_info != NULL, then it's a revertible CAF - it'll be
1830 * on the CAF list, so don't do anything with it here (we'll
1831 * scavenge it later).
1834 && ((StgIndStatic *)q)->saved_info == NULL
1835 && IND_STATIC_LINK((StgClosure *)q) == NULL) {
1836 IND_STATIC_LINK((StgClosure *)q) = static_objects;
1837 static_objects = (StgClosure *)q;
1842 if (major_gc && STATIC_LINK(info,(StgClosure *)q) == NULL) {
1843 STATIC_LINK(info,(StgClosure *)q) = static_objects;
1844 static_objects = (StgClosure *)q;
1848 case CONSTR_INTLIKE:
1849 case CONSTR_CHARLIKE:
1850 case CONSTR_NOCAF_STATIC:
1851 /* no need to put these on the static linked list, they don't need
1865 // shouldn't see these
1866 barf("evacuate: stack frame at %p\n", q);
1870 return copy(q,pap_sizeW((StgPAP*)q),stp);
1873 return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp);
1876 /* Already evacuated, just return the forwarding address.
1877 * HOWEVER: if the requested destination generation (evac_gen) is
1878 * older than the actual generation (because the object was
1879 * already evacuated to a younger generation) then we have to
1880 * set the failed_to_evac flag to indicate that we couldn't
1881 * manage to promote the object to the desired generation.
1883 if (evac_gen > 0) { // optimisation
1884 StgClosure *p = ((StgEvacuated*)q)->evacuee;
1885 if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < evac_gen) {
1886 failed_to_evac = rtsTrue;
1887 TICK_GC_FAILED_PROMOTION();
1890 return ((StgEvacuated*)q)->evacuee;
1893 // just copy the block
1894 return copy(q,arr_words_sizeW((StgArrWords *)q),stp);
1897 case MUT_ARR_PTRS_FROZEN:
1898 // just copy the block
1899 return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
1903 StgTSO *tso = (StgTSO *)q;
1905 /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
1907 if (tso->what_next == ThreadRelocated) {
1908 q = (StgClosure *)tso->link;
1912 /* To evacuate a small TSO, we need to relocate the update frame
1916 StgTSO *new_tso = (StgTSO *)copy((StgClosure *)tso,tso_sizeW(tso),stp);
1917 move_TSO(tso, new_tso);
1918 return (StgClosure *)new_tso;
1923 case RBH: // cf. BLACKHOLE_BQ
1925 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
1926 to = copy(q,BLACKHOLE_sizeW(),stp);
1927 //ToDo: derive size etc from reverted IP
1928 //to = copy(q,size,stp);
1930 belch("@@ evacuate: RBH %p (%s) to %p (%s)",
1931 q, info_type(q), to, info_type(to)));
1936 ASSERT(sizeofW(StgBlockedFetch) >= MIN_NONUPD_SIZE);
1937 to = copy(q,sizeofW(StgBlockedFetch),stp);
1939 belch("@@ evacuate: %p (%s) to %p (%s)",
1940 q, info_type(q), to, info_type(to)));
1947 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1948 to = copy(q,sizeofW(StgFetchMe),stp);
1950 belch("@@ evacuate: %p (%s) to %p (%s)",
1951 q, info_type(q), to, info_type(to)));
1955 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1956 to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
1958 belch("@@ evacuate: %p (%s) to %p (%s)",
1959 q, info_type(q), to, info_type(to)));
1964 barf("evacuate: strange closure type %d", (int)(info->type));
1970 /* -----------------------------------------------------------------------------
1971 Evaluate a THUNK_SELECTOR if possible.
1973 returns: NULL if we couldn't evaluate this THUNK_SELECTOR, or
1974 a closure pointer if we evaluated it and this is the result. Note
1975 that "evaluating" the THUNK_SELECTOR doesn't necessarily mean
1976 reducing it to HNF, just that we have eliminated the selection.
1977 The result might be another thunk, or even another THUNK_SELECTOR.
1979 If the return value is non-NULL, the original selector thunk has
1980 been BLACKHOLE'd, and should be updated with an indirection or a
1981 forwarding pointer. If the return value is NULL, then the selector
1983 -------------------------------------------------------------------------- */
1986 eval_thunk_selector( nat field, StgSelector * p )
1989 const StgInfoTable *info_ptr;
1990 StgClosure *selectee;
1992 selectee = p->selectee;
1994 // Save the real info pointer (NOTE: not the same as get_itbl()).
1995 info_ptr = p->header.info;
1997 // If the THUNK_SELECTOR is in a generation that we are not
1998 // collecting, then bail out early. We won't be able to save any
1999 // space in any case, and updating with an indirection is trickier
2001 if (Bdescr((StgPtr)p)->gen_no > N) {
2005 // BLACKHOLE the selector thunk, since it is now under evaluation.
2006 // This is important to stop us going into an infinite loop if
2007 // this selector thunk eventually refers to itself.
2008 SET_INFO(p,&stg_BLACKHOLE_info);
2012 // We don't want to end up in to-space, because this causes
2013 // problems when the GC later tries to evacuate the result of
2014 // eval_thunk_selector(). There are various ways this could
2017 // - following an IND_STATIC
2019 // - when the old generation is compacted, the mark phase updates
2020 // from-space pointers to be to-space pointers, and we can't
2021 // reliably tell which we're following (eg. from an IND_STATIC).
2023 // So we use the block-descriptor test to find out if we're in
2026 if (HEAP_ALLOCED(selectee) &&
2027 Bdescr((StgPtr)selectee)->flags & BF_EVACUATED) {
2031 info = get_itbl(selectee);
2032 switch (info->type) {
2040 case CONSTR_NOCAF_STATIC:
2041 // check that the size is in range
2042 ASSERT(field < (StgWord32)(info->layout.payload.ptrs +
2043 info->layout.payload.nptrs));
2045 // ToDo: shouldn't we test whether this pointer is in
2047 return selectee->payload[field];
2052 case IND_OLDGEN_PERM:
2054 selectee = ((StgInd *)selectee)->indirectee;
2058 // We don't follow pointers into to-space; the constructor
2059 // has already been evacuated, so we won't save any space
2060 // leaks by evaluating this selector thunk anyhow.
2063 case THUNK_SELECTOR:
2067 // check that we don't recurse too much, re-using the
2068 // depth bound also used in evacuate().
2069 thunk_selector_depth++;
2070 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
2074 val = eval_thunk_selector(info->layout.selector_offset,
2075 (StgSelector *)selectee);
2077 thunk_selector_depth--;
2082 // We evaluated this selector thunk, so update it with
2083 // an indirection. NOTE: we don't use UPD_IND here,
2084 // because we are guaranteed that p is in a generation
2085 // that we are collecting, and we never want to put the
2086 // indirection on a mutable list.
2088 // For the purposes of LDV profiling, we have destroyed
2089 // the original selector thunk.
2090 SET_INFO(p, info_ptr);
2091 LDV_recordDead_FILL_SLOP_DYNAMIC(selectee);
2093 ((StgInd *)selectee)->indirectee = val;
2094 SET_INFO(selectee,&stg_IND_info);
2096 // For the purposes of LDV profiling, we have created an
2098 LDV_recordCreate(selectee);
2114 case SE_CAF_BLACKHOLE:
2127 // not evaluated yet
2131 barf("eval_thunk_selector: strange selectee %d",
2136 // We didn't manage to evaluate this thunk; restore the old info pointer
2137 SET_INFO(p, info_ptr);
2141 /* -----------------------------------------------------------------------------
2142 move_TSO is called to update the TSO structure after it has been
2143 moved from one place to another.
2144 -------------------------------------------------------------------------- */
2147 move_TSO (StgTSO *src, StgTSO *dest)
2151 // relocate the stack pointers...
2152 diff = (StgPtr)dest - (StgPtr)src; // In *words*
2153 dest->sp = (StgPtr)dest->sp + diff;
2156 /* evacuate the SRT. If srt_len is zero, then there isn't an
2157 * srt field in the info table. That's ok, because we'll
2158 * never dereference it.
2161 scavenge_srt (StgClosure **srt, nat srt_len)
2163 StgClosure **srt_end;
2165 srt_end = srt + srt_len;
2167 for (; srt < srt_end; srt++) {
2168 /* Special-case to handle references to closures hiding out in DLLs, since
2169 double indirections required to get at those. The code generator knows
2170 which is which when generating the SRT, so it stores the (indirect)
2171 reference to the DLL closure in the table by first adding one to it.
2172 We check for this here, and undo the addition before evacuating it.
2174 If the SRT entry hasn't got bit 0 set, the SRT entry points to a
2175 closure that's fixed at link-time, and no extra magic is required.
2177 #ifdef ENABLE_WIN32_DLL_SUPPORT
2178 if ( (unsigned long)(*srt) & 0x1 ) {
2179 evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
2191 scavenge_thunk_srt(const StgInfoTable *info)
2193 StgThunkInfoTable *thunk_info;
2195 thunk_info = itbl_to_thunk_itbl(info);
2196 scavenge_srt((StgClosure **)thunk_info->srt, thunk_info->i.srt_len);
2200 scavenge_fun_srt(const StgInfoTable *info)
2202 StgFunInfoTable *fun_info;
2204 fun_info = itbl_to_fun_itbl(info);
2205 scavenge_srt((StgClosure **)fun_info->srt, fun_info->i.srt_len);
2209 scavenge_ret_srt(const StgInfoTable *info)
2211 StgRetInfoTable *ret_info;
2213 ret_info = itbl_to_ret_itbl(info);
2214 scavenge_srt((StgClosure **)ret_info->srt, ret_info->i.srt_len);
2217 /* -----------------------------------------------------------------------------
2219 -------------------------------------------------------------------------- */
2222 scavengeTSO (StgTSO *tso)
2224 // chase the link field for any TSOs on the same queue
2225 (StgClosure *)tso->link = evacuate((StgClosure *)tso->link);
2226 if ( tso->why_blocked == BlockedOnMVar
2227 || tso->why_blocked == BlockedOnBlackHole
2228 || tso->why_blocked == BlockedOnException
2230 || tso->why_blocked == BlockedOnGA
2231 || tso->why_blocked == BlockedOnGA_NoSend
2234 tso->block_info.closure = evacuate(tso->block_info.closure);
2236 if ( tso->blocked_exceptions != NULL ) {
2237 tso->blocked_exceptions =
2238 (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
2241 // scavenge this thread's stack
2242 scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
2245 /* -----------------------------------------------------------------------------
2246 Blocks of function args occur on the stack (at the top) and
2248 -------------------------------------------------------------------------- */
2250 static inline StgPtr
2251 scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
2258 switch (fun_info->fun_type) {
2260 bitmap = BITMAP_BITS(fun_info->bitmap);
2261 size = BITMAP_SIZE(fun_info->bitmap);
2264 size = ((StgLargeBitmap *)fun_info->bitmap)->size;
2265 scavenge_large_bitmap(p, (StgLargeBitmap *)fun_info->bitmap, size);
2269 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->fun_type]);
2270 size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->fun_type]);
2273 if ((bitmap & 1) == 0) {
2274 (StgClosure *)*p = evacuate((StgClosure *)*p);
2277 bitmap = bitmap >> 1;
2285 static inline StgPtr
2286 scavenge_PAP (StgPAP *pap)
2289 StgWord bitmap, size;
2290 StgFunInfoTable *fun_info;
2292 pap->fun = evacuate(pap->fun);
2293 fun_info = get_fun_itbl(pap->fun);
2294 ASSERT(fun_info->i.type != PAP);
2296 p = (StgPtr)pap->payload;
2299 switch (fun_info->fun_type) {
2301 bitmap = BITMAP_BITS(fun_info->bitmap);
2304 scavenge_large_bitmap(p, (StgLargeBitmap *)fun_info->bitmap, size);
2308 scavenge_large_bitmap((StgPtr)pap->payload, BCO_BITMAP(pap->fun), size);
2312 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->fun_type]);
2316 if ((bitmap & 1) == 0) {
2317 (StgClosure *)*p = evacuate((StgClosure *)*p);
2320 bitmap = bitmap >> 1;
2328 /* -----------------------------------------------------------------------------
2329 Scavenge a given step until there are no more objects in this step
2332 evac_gen is set by the caller to be either zero (for a step in a
2333 generation < N) or G where G is the generation of the step being
2336 We sometimes temporarily change evac_gen back to zero if we're
2337 scavenging a mutable object where early promotion isn't such a good
2339 -------------------------------------------------------------------------- */
2347 nat saved_evac_gen = evac_gen;
2352 failed_to_evac = rtsFalse;
2354 /* scavenge phase - standard breadth-first scavenging of the
2358 while (bd != stp->hp_bd || p < stp->hp) {
2360 // If we're at the end of this block, move on to the next block
2361 if (bd != stp->hp_bd && p == bd->free) {
2367 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2368 info = get_itbl((StgClosure *)p);
2370 ASSERT(thunk_selector_depth == 0);
2373 switch (info->type) {
2376 /* treat MVars specially, because we don't want to evacuate the
2377 * mut_link field in the middle of the closure.
2380 StgMVar *mvar = ((StgMVar *)p);
2382 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
2383 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
2384 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
2385 evac_gen = saved_evac_gen;
2386 recordMutable((StgMutClosure *)mvar);
2387 failed_to_evac = rtsFalse; // mutable.
2388 p += sizeofW(StgMVar);
2393 scavenge_fun_srt(info);
2394 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2395 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2396 p += sizeofW(StgHeader) + 2;
2400 scavenge_thunk_srt(info);
2402 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2403 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2404 p += sizeofW(StgHeader) + 2;
2408 scavenge_thunk_srt(info);
2409 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2410 p += sizeofW(StgHeader) + 2; // MIN_UPD_SIZE
2414 scavenge_fun_srt(info);
2416 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2417 p += sizeofW(StgHeader) + 1;
2421 scavenge_thunk_srt(info);
2422 p += sizeofW(StgHeader) + 2; // MIN_UPD_SIZE
2426 scavenge_fun_srt(info);
2428 p += sizeofW(StgHeader) + 1;
2432 scavenge_thunk_srt(info);
2433 p += sizeofW(StgHeader) + 2;
2437 scavenge_fun_srt(info);
2439 p += sizeofW(StgHeader) + 2;
2443 scavenge_thunk_srt(info);
2444 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2445 p += sizeofW(StgHeader) + 2;
2449 scavenge_fun_srt(info);
2451 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2452 p += sizeofW(StgHeader) + 2;
2456 scavenge_fun_srt(info);
2460 scavenge_thunk_srt(info);
2471 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2472 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2473 (StgClosure *)*p = evacuate((StgClosure *)*p);
2475 p += info->layout.payload.nptrs;
2480 StgBCO *bco = (StgBCO *)p;
2481 (StgClosure *)bco->instrs = evacuate((StgClosure *)bco->instrs);
2482 (StgClosure *)bco->literals = evacuate((StgClosure *)bco->literals);
2483 (StgClosure *)bco->ptrs = evacuate((StgClosure *)bco->ptrs);
2484 (StgClosure *)bco->itbls = evacuate((StgClosure *)bco->itbls);
2485 p += bco_sizeW(bco);
2490 if (stp->gen->no != 0) {
2493 // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an
2494 // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
2495 LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
2498 // Todo: maybe use SET_HDR() and remove LDV_recordCreate()?
2500 SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
2503 // We pretend that p has just been created.
2504 LDV_recordCreate((StgClosure *)p);
2508 case IND_OLDGEN_PERM:
2509 ((StgIndOldGen *)p)->indirectee =
2510 evacuate(((StgIndOldGen *)p)->indirectee);
2511 if (failed_to_evac) {
2512 failed_to_evac = rtsFalse;
2513 recordOldToNewPtrs((StgMutClosure *)p);
2515 p += sizeofW(StgIndOldGen);
2520 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2521 evac_gen = saved_evac_gen;
2522 recordMutable((StgMutClosure *)p);
2523 failed_to_evac = rtsFalse; // mutable anyhow
2524 p += sizeofW(StgMutVar);
2529 failed_to_evac = rtsFalse; // mutable anyhow
2530 p += sizeofW(StgMutVar);
2534 case SE_CAF_BLACKHOLE:
2537 p += BLACKHOLE_sizeW();
2542 StgBlockingQueue *bh = (StgBlockingQueue *)p;
2543 (StgClosure *)bh->blocking_queue =
2544 evacuate((StgClosure *)bh->blocking_queue);
2545 recordMutable((StgMutClosure *)bh);
2546 failed_to_evac = rtsFalse;
2547 p += BLACKHOLE_sizeW();
2551 case THUNK_SELECTOR:
2553 StgSelector *s = (StgSelector *)p;
2554 s->selectee = evacuate(s->selectee);
2555 p += THUNK_SELECTOR_sizeW();
2559 // A chunk of stack saved in a heap object
2562 StgAP_STACK *ap = (StgAP_STACK *)p;
2564 ap->fun = evacuate(ap->fun);
2565 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2566 p = (StgPtr)ap->payload + ap->size;
2572 p = scavenge_PAP((StgPAP *)p);
2576 // nothing to follow
2577 p += arr_words_sizeW((StgArrWords *)p);
2581 // follow everything
2585 evac_gen = 0; // repeatedly mutable
2586 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2587 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2588 (StgClosure *)*p = evacuate((StgClosure *)*p);
2590 evac_gen = saved_evac_gen;
2591 recordMutable((StgMutClosure *)q);
2592 failed_to_evac = rtsFalse; // mutable anyhow.
2596 case MUT_ARR_PTRS_FROZEN:
2597 // follow everything
2601 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2602 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2603 (StgClosure *)*p = evacuate((StgClosure *)*p);
2605 // it's tempting to recordMutable() if failed_to_evac is
2606 // false, but that breaks some assumptions (eg. every
2607 // closure on the mutable list is supposed to have the MUT
2608 // flag set, and MUT_ARR_PTRS_FROZEN doesn't).
2614 StgTSO *tso = (StgTSO *)p;
2617 evac_gen = saved_evac_gen;
2618 recordMutable((StgMutClosure *)tso);
2619 failed_to_evac = rtsFalse; // mutable anyhow.
2620 p += tso_sizeW(tso);
2625 case RBH: // cf. BLACKHOLE_BQ
2628 nat size, ptrs, nonptrs, vhs;
2630 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2632 StgRBH *rbh = (StgRBH *)p;
2633 (StgClosure *)rbh->blocking_queue =
2634 evacuate((StgClosure *)rbh->blocking_queue);
2635 recordMutable((StgMutClosure *)to);
2636 failed_to_evac = rtsFalse; // mutable anyhow.
2638 belch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2639 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2640 // ToDo: use size of reverted closure here!
2641 p += BLACKHOLE_sizeW();
2647 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2648 // follow the pointer to the node which is being demanded
2649 (StgClosure *)bf->node =
2650 evacuate((StgClosure *)bf->node);
2651 // follow the link to the rest of the blocking queue
2652 (StgClosure *)bf->link =
2653 evacuate((StgClosure *)bf->link);
2654 if (failed_to_evac) {
2655 failed_to_evac = rtsFalse;
2656 recordMutable((StgMutClosure *)bf);
2659 belch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
2660 bf, info_type((StgClosure *)bf),
2661 bf->node, info_type(bf->node)));
2662 p += sizeofW(StgBlockedFetch);
2670 p += sizeofW(StgFetchMe);
2671 break; // nothing to do in this case
2673 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
2675 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
2676 (StgClosure *)fmbq->blocking_queue =
2677 evacuate((StgClosure *)fmbq->blocking_queue);
2678 if (failed_to_evac) {
2679 failed_to_evac = rtsFalse;
2680 recordMutable((StgMutClosure *)fmbq);
2683 belch("@@ scavenge: %p (%s) exciting, isn't it",
2684 p, info_type((StgClosure *)p)));
2685 p += sizeofW(StgFetchMeBlockingQueue);
2691 barf("scavenge: unimplemented/strange closure type %d @ %p",
2695 /* If we didn't manage to promote all the objects pointed to by
2696 * the current object, then we have to designate this object as
2697 * mutable (because it contains old-to-new generation pointers).
2699 if (failed_to_evac) {
2700 failed_to_evac = rtsFalse;
2701 mkMutCons((StgClosure *)q, &generations[evac_gen]);
2709 /* -----------------------------------------------------------------------------
2710 Scavenge everything on the mark stack.
2712 This is slightly different from scavenge():
2713 - we don't walk linearly through the objects, so the scavenger
2714 doesn't need to advance the pointer on to the next object.
2715 -------------------------------------------------------------------------- */
2718 scavenge_mark_stack(void)
2724 evac_gen = oldest_gen->no;
2725 saved_evac_gen = evac_gen;
2728 while (!mark_stack_empty()) {
2729 p = pop_mark_stack();
2731 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2732 info = get_itbl((StgClosure *)p);
2735 switch (info->type) {
2738 /* treat MVars specially, because we don't want to evacuate the
2739 * mut_link field in the middle of the closure.
2742 StgMVar *mvar = ((StgMVar *)p);
2744 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
2745 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
2746 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
2747 evac_gen = saved_evac_gen;
2748 failed_to_evac = rtsFalse; // mutable.
2753 scavenge_fun_srt(info);
2754 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2755 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2759 scavenge_thunk_srt(info);
2761 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2762 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2767 scavenge_fun_srt(info);
2768 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2773 scavenge_thunk_srt(info);
2776 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2781 scavenge_fun_srt(info);
2786 scavenge_thunk_srt(info);
2794 scavenge_fun_srt(info);
2798 scavenge_thunk_srt(info);
2809 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2810 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2811 (StgClosure *)*p = evacuate((StgClosure *)*p);
2817 StgBCO *bco = (StgBCO *)p;
2818 (StgClosure *)bco->instrs = evacuate((StgClosure *)bco->instrs);
2819 (StgClosure *)bco->literals = evacuate((StgClosure *)bco->literals);
2820 (StgClosure *)bco->ptrs = evacuate((StgClosure *)bco->ptrs);
2821 (StgClosure *)bco->itbls = evacuate((StgClosure *)bco->itbls);
2826 // don't need to do anything here: the only possible case
2827 // is that we're in a 1-space compacting collector, with
2828 // no "old" generation.
2832 case IND_OLDGEN_PERM:
2833 ((StgIndOldGen *)p)->indirectee =
2834 evacuate(((StgIndOldGen *)p)->indirectee);
2835 if (failed_to_evac) {
2836 recordOldToNewPtrs((StgMutClosure *)p);
2838 failed_to_evac = rtsFalse;
2843 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2844 evac_gen = saved_evac_gen;
2845 failed_to_evac = rtsFalse;
2850 failed_to_evac = rtsFalse;
2854 case SE_CAF_BLACKHOLE:
2862 StgBlockingQueue *bh = (StgBlockingQueue *)p;
2863 (StgClosure *)bh->blocking_queue =
2864 evacuate((StgClosure *)bh->blocking_queue);
2865 failed_to_evac = rtsFalse;
2869 case THUNK_SELECTOR:
2871 StgSelector *s = (StgSelector *)p;
2872 s->selectee = evacuate(s->selectee);
2876 // A chunk of stack saved in a heap object
2879 StgAP_STACK *ap = (StgAP_STACK *)p;
2881 ap->fun = evacuate(ap->fun);
2882 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2888 scavenge_PAP((StgPAP *)p);
2892 // follow everything
2896 evac_gen = 0; // repeatedly mutable
2897 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2898 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2899 (StgClosure *)*p = evacuate((StgClosure *)*p);
2901 evac_gen = saved_evac_gen;
2902 failed_to_evac = rtsFalse; // mutable anyhow.
2906 case MUT_ARR_PTRS_FROZEN:
2907 // follow everything
2911 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2912 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2913 (StgClosure *)*p = evacuate((StgClosure *)*p);
2920 StgTSO *tso = (StgTSO *)p;
2923 evac_gen = saved_evac_gen;
2924 failed_to_evac = rtsFalse;
2929 case RBH: // cf. BLACKHOLE_BQ
2932 nat size, ptrs, nonptrs, vhs;
2934 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2936 StgRBH *rbh = (StgRBH *)p;
2937 (StgClosure *)rbh->blocking_queue =
2938 evacuate((StgClosure *)rbh->blocking_queue);
2939 recordMutable((StgMutClosure *)rbh);
2940 failed_to_evac = rtsFalse; // mutable anyhow.
2942 belch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2943 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2949 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2950 // follow the pointer to the node which is being demanded
2951 (StgClosure *)bf->node =
2952 evacuate((StgClosure *)bf->node);
2953 // follow the link to the rest of the blocking queue
2954 (StgClosure *)bf->link =
2955 evacuate((StgClosure *)bf->link);
2956 if (failed_to_evac) {
2957 failed_to_evac = rtsFalse;
2958 recordMutable((StgMutClosure *)bf);
2961 belch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
2962 bf, info_type((StgClosure *)bf),
2963 bf->node, info_type(bf->node)));
2971 break; // nothing to do in this case
2973 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
2975 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
2976 (StgClosure *)fmbq->blocking_queue =
2977 evacuate((StgClosure *)fmbq->blocking_queue);
2978 if (failed_to_evac) {
2979 failed_to_evac = rtsFalse;
2980 recordMutable((StgMutClosure *)fmbq);
2983 belch("@@ scavenge: %p (%s) exciting, isn't it",
2984 p, info_type((StgClosure *)p)));
2990 barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p",
2994 if (failed_to_evac) {
2995 failed_to_evac = rtsFalse;
2996 mkMutCons((StgClosure *)q, &generations[evac_gen]);
2999 // mark the next bit to indicate "scavenged"
3000 mark(q+1, Bdescr(q));
3002 } // while (!mark_stack_empty())
3004 // start a new linear scan if the mark stack overflowed at some point
3005 if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
3006 IF_DEBUG(gc, belch("scavenge_mark_stack: starting linear scan"));
3007 mark_stack_overflowed = rtsFalse;
3008 oldgen_scan_bd = oldest_gen->steps[0].blocks;
3009 oldgen_scan = oldgen_scan_bd->start;
3012 if (oldgen_scan_bd) {
3013 // push a new thing on the mark stack
3015 // find a closure that is marked but not scavenged, and start
3017 while (oldgen_scan < oldgen_scan_bd->free
3018 && !is_marked(oldgen_scan,oldgen_scan_bd)) {
3022 if (oldgen_scan < oldgen_scan_bd->free) {
3024 // already scavenged?
3025 if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
3026 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3029 push_mark_stack(oldgen_scan);
3030 // ToDo: bump the linear scan by the actual size of the object
3031 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3035 oldgen_scan_bd = oldgen_scan_bd->link;
3036 if (oldgen_scan_bd != NULL) {
3037 oldgen_scan = oldgen_scan_bd->start;
3043 /* -----------------------------------------------------------------------------
3044 Scavenge one object.
3046 This is used for objects that are temporarily marked as mutable
3047 because they contain old-to-new generation pointers. Only certain
3048 objects can have this property.
3049 -------------------------------------------------------------------------- */
3052 scavenge_one(StgPtr p)
3054 const StgInfoTable *info;
3055 nat saved_evac_gen = evac_gen;
3058 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3059 info = get_itbl((StgClosure *)p);
3061 switch (info->type) {
3064 case FUN_1_0: // hardly worth specialising these guys
3084 case IND_OLDGEN_PERM:
3088 end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3089 for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
3090 (StgClosure *)*q = evacuate((StgClosure *)*q);
3096 case SE_CAF_BLACKHOLE:
3101 case THUNK_SELECTOR:
3103 StgSelector *s = (StgSelector *)p;
3104 s->selectee = evacuate(s->selectee);
3109 // nothing to follow
3114 // follow everything
3117 evac_gen = 0; // repeatedly mutable
3118 recordMutable((StgMutClosure *)p);
3119 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3120 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3121 (StgClosure *)*p = evacuate((StgClosure *)*p);
3123 evac_gen = saved_evac_gen;
3124 failed_to_evac = rtsFalse;
3128 case MUT_ARR_PTRS_FROZEN:
3130 // follow everything
3133 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3134 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3135 (StgClosure *)*p = evacuate((StgClosure *)*p);
3142 StgTSO *tso = (StgTSO *)p;
3144 evac_gen = 0; // repeatedly mutable
3146 recordMutable((StgMutClosure *)tso);
3147 evac_gen = saved_evac_gen;
3148 failed_to_evac = rtsFalse;
3154 StgAP_STACK *ap = (StgAP_STACK *)p;
3156 ap->fun = evacuate(ap->fun);
3157 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3158 p = (StgPtr)ap->payload + ap->size;
3164 p = scavenge_PAP((StgPAP *)p);
3168 // This might happen if for instance a MUT_CONS was pointing to a
3169 // THUNK which has since been updated. The IND_OLDGEN will
3170 // be on the mutable list anyway, so we don't need to do anything
3175 barf("scavenge_one: strange object %d", (int)(info->type));
3178 no_luck = failed_to_evac;
3179 failed_to_evac = rtsFalse;
3183 /* -----------------------------------------------------------------------------
3184 Scavenging mutable lists.
3186 We treat the mutable list of each generation > N (i.e. all the
3187 generations older than the one being collected) as roots. We also
3188 remove non-mutable objects from the mutable list at this point.
3189 -------------------------------------------------------------------------- */
3192 scavenge_mut_once_list(generation *gen)
3194 const StgInfoTable *info;
3195 StgMutClosure *p, *next, *new_list;
3197 p = gen->mut_once_list;
3198 new_list = END_MUT_LIST;
3202 failed_to_evac = rtsFalse;
3204 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
3206 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3209 if (info->type==RBH)
3210 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3212 switch(info->type) {
3215 case IND_OLDGEN_PERM:
3217 /* Try to pull the indirectee into this generation, so we can
3218 * remove the indirection from the mutable list.
3220 ((StgIndOldGen *)p)->indirectee =
3221 evacuate(((StgIndOldGen *)p)->indirectee);
3223 #if 0 && defined(DEBUG)
3224 if (RtsFlags.DebugFlags.gc)
3225 /* Debugging code to print out the size of the thing we just
3229 StgPtr start = gen->steps[0].scan;
3230 bdescr *start_bd = gen->steps[0].scan_bd;
3232 scavenge(&gen->steps[0]);
3233 if (start_bd != gen->steps[0].scan_bd) {
3234 size += (P_)BLOCK_ROUND_UP(start) - start;
3235 start_bd = start_bd->link;
3236 while (start_bd != gen->steps[0].scan_bd) {
3237 size += BLOCK_SIZE_W;
3238 start_bd = start_bd->link;
3240 size += gen->steps[0].scan -
3241 (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
3243 size = gen->steps[0].scan - start;
3245 belch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
3249 /* failed_to_evac might happen if we've got more than two
3250 * generations, we're collecting only generation 0, the
3251 * indirection resides in generation 2 and the indirectee is
3254 if (failed_to_evac) {
3255 failed_to_evac = rtsFalse;
3256 p->mut_link = new_list;
3259 /* the mut_link field of an IND_STATIC is overloaded as the
3260 * static link field too (it just so happens that we don't need
3261 * both at the same time), so we need to NULL it out when
3262 * removing this object from the mutable list because the static
3263 * link fields are all assumed to be NULL before doing a major
3271 /* MUT_CONS is a kind of MUT_VAR, except it that we try to remove
3272 * it from the mutable list if possible by promoting whatever it
3275 if (scavenge_one((StgPtr)((StgMutVar *)p)->var)) {
3276 /* didn't manage to promote everything, so put the
3277 * MUT_CONS back on the list.
3279 p->mut_link = new_list;
3285 // shouldn't have anything else on the mutables list
3286 barf("scavenge_mut_once_list: strange object? %d", (int)(info->type));
3290 gen->mut_once_list = new_list;
3295 scavenge_mutable_list(generation *gen)
3297 const StgInfoTable *info;
3298 StgMutClosure *p, *next;
3300 p = gen->saved_mut_list;
3304 failed_to_evac = rtsFalse;
3306 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
3308 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3311 if (info->type==RBH)
3312 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3314 switch(info->type) {
3317 // follow everything
3318 p->mut_link = gen->mut_list;
3323 end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3324 for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
3325 (StgClosure *)*q = evacuate((StgClosure *)*q);
3330 // Happens if a MUT_ARR_PTRS in the old generation is frozen
3331 case MUT_ARR_PTRS_FROZEN:
3336 end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3337 for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
3338 (StgClosure *)*q = evacuate((StgClosure *)*q);
3342 if (failed_to_evac) {
3343 failed_to_evac = rtsFalse;
3344 mkMutCons((StgClosure *)p, gen);
3350 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3351 p->mut_link = gen->mut_list;
3357 StgMVar *mvar = (StgMVar *)p;
3358 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
3359 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
3360 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
3361 p->mut_link = gen->mut_list;
3368 StgTSO *tso = (StgTSO *)p;
3372 /* Don't take this TSO off the mutable list - it might still
3373 * point to some younger objects (because we set evac_gen to 0
3376 tso->mut_link = gen->mut_list;
3377 gen->mut_list = (StgMutClosure *)tso;
3383 StgBlockingQueue *bh = (StgBlockingQueue *)p;
3384 (StgClosure *)bh->blocking_queue =
3385 evacuate((StgClosure *)bh->blocking_queue);
3386 p->mut_link = gen->mut_list;
3391 /* Happens if a BLACKHOLE_BQ in the old generation is updated:
3394 case IND_OLDGEN_PERM:
3395 /* Try to pull the indirectee into this generation, so we can
3396 * remove the indirection from the mutable list.
3399 ((StgIndOldGen *)p)->indirectee =
3400 evacuate(((StgIndOldGen *)p)->indirectee);
3403 if (failed_to_evac) {
3404 failed_to_evac = rtsFalse;
3405 p->mut_link = gen->mut_once_list;
3406 gen->mut_once_list = p;
3413 // HWL: check whether all of these are necessary
3415 case RBH: // cf. BLACKHOLE_BQ
3417 // nat size, ptrs, nonptrs, vhs;
3419 // StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3420 StgRBH *rbh = (StgRBH *)p;
3421 (StgClosure *)rbh->blocking_queue =
3422 evacuate((StgClosure *)rbh->blocking_queue);
3423 if (failed_to_evac) {
3424 failed_to_evac = rtsFalse;
3425 recordMutable((StgMutClosure *)rbh);
3427 // ToDo: use size of reverted closure here!
3428 p += BLACKHOLE_sizeW();
3434 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3435 // follow the pointer to the node which is being demanded
3436 (StgClosure *)bf->node =
3437 evacuate((StgClosure *)bf->node);
3438 // follow the link to the rest of the blocking queue
3439 (StgClosure *)bf->link =
3440 evacuate((StgClosure *)bf->link);
3441 if (failed_to_evac) {
3442 failed_to_evac = rtsFalse;
3443 recordMutable((StgMutClosure *)bf);
3445 p += sizeofW(StgBlockedFetch);
3451 barf("scavenge_mutable_list: REMOTE_REF %d", (int)(info->type));
3454 p += sizeofW(StgFetchMe);
3455 break; // nothing to do in this case
3457 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
3459 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3460 (StgClosure *)fmbq->blocking_queue =
3461 evacuate((StgClosure *)fmbq->blocking_queue);
3462 if (failed_to_evac) {
3463 failed_to_evac = rtsFalse;
3464 recordMutable((StgMutClosure *)fmbq);
3466 p += sizeofW(StgFetchMeBlockingQueue);
3472 // shouldn't have anything else on the mutables list
3473 barf("scavenge_mutable_list: strange object? %d", (int)(info->type));
3480 scavenge_static(void)
3482 StgClosure* p = static_objects;
3483 const StgInfoTable *info;
3485 /* Always evacuate straight to the oldest generation for static
3487 evac_gen = oldest_gen->no;
3489 /* keep going until we've scavenged all the objects on the linked
3491 while (p != END_OF_STATIC_LIST) {
3493 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3496 if (info->type==RBH)
3497 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3499 // make sure the info pointer is into text space
3501 /* Take this object *off* the static_objects list,
3502 * and put it on the scavenged_static_objects list.
3504 static_objects = STATIC_LINK(info,p);
3505 STATIC_LINK(info,p) = scavenged_static_objects;
3506 scavenged_static_objects = p;
3508 switch (info -> type) {
3512 StgInd *ind = (StgInd *)p;
3513 ind->indirectee = evacuate(ind->indirectee);
3515 /* might fail to evacuate it, in which case we have to pop it
3516 * back on the mutable list (and take it off the
3517 * scavenged_static list because the static link and mut link
3518 * pointers are one and the same).
3520 if (failed_to_evac) {
3521 failed_to_evac = rtsFalse;
3522 scavenged_static_objects = IND_STATIC_LINK(p);
3523 ((StgMutClosure *)ind)->mut_link = oldest_gen->mut_once_list;
3524 oldest_gen->mut_once_list = (StgMutClosure *)ind;
3530 scavenge_thunk_srt(info);
3534 scavenge_fun_srt(info);
3541 next = (P_)p->payload + info->layout.payload.ptrs;
3542 // evacuate the pointers
3543 for (q = (P_)p->payload; q < next; q++) {
3544 (StgClosure *)*q = evacuate((StgClosure *)*q);
3550 barf("scavenge_static: strange closure %d", (int)(info->type));
3553 ASSERT(failed_to_evac == rtsFalse);
3555 /* get the next static object from the list. Remember, there might
3556 * be more stuff on this list now that we've done some evacuating!
3557 * (static_objects is a global)
3563 /* -----------------------------------------------------------------------------
3564 scavenge a chunk of memory described by a bitmap
3565 -------------------------------------------------------------------------- */
3568 scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
3574 bitmap = large_bitmap->bitmap[b];
3575 for (i = 0; i < size; ) {
3576 if ((bitmap & 1) == 0) {
3577 (StgClosure *)*p = evacuate((StgClosure *)*p);
3581 if (i % BITS_IN(W_) == 0) {
3583 bitmap = large_bitmap->bitmap[b];
3585 bitmap = bitmap >> 1;
3590 static inline StgPtr
3591 scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap)
3594 if ((bitmap & 1) == 0) {
3595 (StgClosure *)*p = evacuate((StgClosure *)*p);
3598 bitmap = bitmap >> 1;
3604 /* -----------------------------------------------------------------------------
3605 scavenge_stack walks over a section of stack and evacuates all the
3606 objects pointed to by it. We can use the same code for walking
3607 AP_STACK_UPDs, since these are just sections of copied stack.
3608 -------------------------------------------------------------------------- */
3612 scavenge_stack(StgPtr p, StgPtr stack_end)
3614 const StgRetInfoTable* info;
3618 //IF_DEBUG(sanity, belch(" scavenging stack between %p and %p", p, stack_end));
3621 * Each time around this loop, we are looking at a chunk of stack
3622 * that starts with an activation record.
3625 while (p < stack_end) {
3626 info = get_ret_itbl((StgClosure *)p);
3628 switch (info->i.type) {
3631 ((StgUpdateFrame *)p)->updatee
3632 = evacuate(((StgUpdateFrame *)p)->updatee);
3633 p += sizeofW(StgUpdateFrame);
3636 // small bitmap (< 32 entries, or 64 on a 64-bit machine)
3641 bitmap = BITMAP_BITS(info->i.layout.bitmap);
3642 size = BITMAP_SIZE(info->i.layout.bitmap);
3643 // NOTE: the payload starts immediately after the info-ptr, we
3644 // don't have an StgHeader in the same sense as a heap closure.
3646 p = scavenge_small_bitmap(p, size, bitmap);
3649 scavenge_srt((StgClosure **)info->srt, info->i.srt_len);
3657 (StgClosure *)*p = evacuate((StgClosure *)*p);
3660 size = BCO_BITMAP_SIZE(bco);
3661 scavenge_large_bitmap(p, BCO_BITMAP(bco), size);
3666 // large bitmap (> 32 entries, or > 64 on a 64-bit machine)
3672 size = info->i.layout.large_bitmap->size;
3674 scavenge_large_bitmap(p, info->i.layout.large_bitmap, size);
3676 // and don't forget to follow the SRT
3680 // Dynamic bitmap: the mask is stored on the stack, and
3681 // there are a number of non-pointers followed by a number
3682 // of pointers above the bitmapped area. (see StgMacros.h,
3687 dyn = ((StgRetDyn *)p)->liveness;
3689 // traverse the bitmap first
3690 bitmap = GET_LIVENESS(dyn);
3691 p = (P_)&((StgRetDyn *)p)->payload[0];
3692 size = RET_DYN_SIZE;
3693 p = scavenge_small_bitmap(p, size, bitmap);
3695 // skip over the non-ptr words
3696 p += GET_NONPTRS(dyn);
3698 // follow the ptr words
3699 for (size = GET_PTRS(dyn); size > 0; size--) {
3700 (StgClosure *)*p = evacuate((StgClosure *)*p);
3708 StgRetFun *ret_fun = (StgRetFun *)p;
3709 StgFunInfoTable *fun_info;
3711 ret_fun->fun = evacuate(ret_fun->fun);
3712 fun_info = get_fun_itbl(ret_fun->fun);
3713 p = scavenge_arg_block(fun_info, ret_fun->payload);
3718 barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->i.type));
3723 /*-----------------------------------------------------------------------------
3724 scavenge the large object list.
3726 evac_gen set by caller; similar games played with evac_gen as with
3727 scavenge() - see comment at the top of scavenge(). Most large
3728 objects are (repeatedly) mutable, so most of the time evac_gen will
3730 --------------------------------------------------------------------------- */
3733 scavenge_large(step *stp)
3738 bd = stp->new_large_objects;
3740 for (; bd != NULL; bd = stp->new_large_objects) {
3742 /* take this object *off* the large objects list and put it on
3743 * the scavenged large objects list. This is so that we can
3744 * treat new_large_objects as a stack and push new objects on
3745 * the front when evacuating.
3747 stp->new_large_objects = bd->link;
3748 dbl_link_onto(bd, &stp->scavenged_large_objects);
3750 // update the block count in this step.
3751 stp->n_scavenged_large_blocks += bd->blocks;
3754 if (scavenge_one(p)) {
3755 mkMutCons((StgClosure *)p, stp->gen);
3760 /* -----------------------------------------------------------------------------
3761 Initialising the static object & mutable lists
3762 -------------------------------------------------------------------------- */
3765 zero_static_object_list(StgClosure* first_static)
3769 const StgInfoTable *info;
3771 for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
3773 link = STATIC_LINK(info, p);
3774 STATIC_LINK(info,p) = NULL;
3778 /* This function is only needed because we share the mutable link
3779 * field with the static link field in an IND_STATIC, so we have to
3780 * zero the mut_link field before doing a major GC, which needs the
3781 * static link field.
3783 * It doesn't do any harm to zero all the mutable link fields on the
3788 zero_mutable_list( StgMutClosure *first )
3790 StgMutClosure *next, *c;
3792 for (c = first; c != END_MUT_LIST; c = next) {
3798 /* -----------------------------------------------------------------------------
3800 -------------------------------------------------------------------------- */
3807 for (c = (StgIndStatic *)caf_list; c != NULL;
3808 c = (StgIndStatic *)c->static_link)
3810 c->header.info = c->saved_info;
3811 c->saved_info = NULL;
3812 // could, but not necessary: c->static_link = NULL;
3818 markCAFs( evac_fn evac )
3822 for (c = (StgIndStatic *)caf_list; c != NULL;
3823 c = (StgIndStatic *)c->static_link)
3825 evac(&c->indirectee);
3829 /* -----------------------------------------------------------------------------
3830 Sanity code for CAF garbage collection.
3832 With DEBUG turned on, we manage a CAF list in addition to the SRT
3833 mechanism. After GC, we run down the CAF list and blackhole any
3834 CAFs which have been garbage collected. This means we get an error
3835 whenever the program tries to enter a garbage collected CAF.
3837 Any garbage collected CAFs are taken off the CAF list at the same
3839 -------------------------------------------------------------------------- */
3841 #if 0 && defined(DEBUG)
3848 const StgInfoTable *info;
3859 ASSERT(info->type == IND_STATIC);
3861 if (STATIC_LINK(info,p) == NULL) {
3862 IF_DEBUG(gccafs, belch("CAF gc'd at 0x%04lx", (long)p));
3864 SET_INFO(p,&stg_BLACKHOLE_info);
3865 p = STATIC_LINK2(info,p);
3869 pp = &STATIC_LINK2(info,p);
3876 // belch("%d CAFs live", i);
3881 /* -----------------------------------------------------------------------------
3884 Whenever a thread returns to the scheduler after possibly doing
3885 some work, we have to run down the stack and black-hole all the
3886 closures referred to by update frames.
3887 -------------------------------------------------------------------------- */
3890 threadLazyBlackHole(StgTSO *tso)
3893 StgRetInfoTable *info;
3894 StgBlockingQueue *bh;
3897 stack_end = &tso->stack[tso->stack_size];
3899 frame = (StgClosure *)tso->sp;
3902 info = get_ret_itbl(frame);
3904 switch (info->i.type) {
3907 bh = (StgBlockingQueue *)((StgUpdateFrame *)frame)->updatee;
3909 /* if the thunk is already blackholed, it means we've also
3910 * already blackholed the rest of the thunks on this stack,
3911 * so we can stop early.
3913 * The blackhole made for a CAF is a CAF_BLACKHOLE, so they
3914 * don't interfere with this optimisation.
3916 if (bh->header.info == &stg_BLACKHOLE_info) {
3920 if (bh->header.info != &stg_BLACKHOLE_BQ_info &&
3921 bh->header.info != &stg_CAF_BLACKHOLE_info) {
3922 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
3923 belch("Unexpected lazy BHing required at 0x%04x",(int)bh);
3927 // We pretend that bh is now dead.
3928 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
3930 SET_INFO(bh,&stg_BLACKHOLE_info);
3933 // We pretend that bh has just been created.
3934 LDV_recordCreate(bh);
3938 frame = (StgClosure *) ((StgUpdateFrame *)frame + 1);
3944 // normal stack frames; do nothing except advance the pointer
3946 (StgPtr)frame += stack_frame_sizeW(frame);
3952 /* -----------------------------------------------------------------------------
3955 * Code largely pinched from old RTS, then hacked to bits. We also do
3956 * lazy black holing here.
3958 * -------------------------------------------------------------------------- */
3960 struct stack_gap { StgWord gap_size; struct stack_gap *next_gap; };
3963 threadSqueezeStack(StgTSO *tso)
3966 rtsBool prev_was_update_frame;
3967 StgClosure *updatee = NULL;
3969 StgRetInfoTable *info;
3970 StgWord current_gap_size;
3971 struct stack_gap *gap;
3974 // Traverse the stack upwards, replacing adjacent update frames
3975 // with a single update frame and a "stack gap". A stack gap
3976 // contains two values: the size of the gap, and the distance
3977 // to the next gap (or the stack top).
3979 bottom = &(tso->stack[tso->stack_size]);
3983 ASSERT(frame < bottom);
3985 prev_was_update_frame = rtsFalse;
3986 current_gap_size = 0;
3987 gap = (struct stack_gap *) (tso->sp - sizeofW(StgUpdateFrame));
3989 while (frame < bottom) {
3991 info = get_ret_itbl((StgClosure *)frame);
3992 switch (info->i.type) {
3996 StgUpdateFrame *upd = (StgUpdateFrame *)frame;
3998 if (upd->updatee->header.info == &stg_BLACKHOLE_info) {
4000 // found a BLACKHOLE'd update frame; we've been here
4001 // before, in a previous GC, so just break out.
4003 // Mark the end of the gap, if we're in one.
4004 if (current_gap_size != 0) {
4005 gap = (struct stack_gap *)(frame-sizeofW(StgUpdateFrame));
4008 frame += sizeofW(StgUpdateFrame);
4009 goto done_traversing;
4012 if (prev_was_update_frame) {
4014 TICK_UPD_SQUEEZED();
4015 /* wasn't there something about update squeezing and ticky to be
4016 * sorted out? oh yes: we aren't counting each enter properly
4017 * in this case. See the log somewhere. KSW 1999-04-21
4019 * Check two things: that the two update frames don't point to
4020 * the same object, and that the updatee_bypass isn't already an
4021 * indirection. Both of these cases only happen when we're in a
4022 * block hole-style loop (and there are multiple update frames
4023 * on the stack pointing to the same closure), but they can both
4024 * screw us up if we don't check.
4026 if (upd->updatee != updatee && !closure_IND(upd->updatee)) {
4027 // this wakes the threads up
4028 UPD_IND_NOLOCK(upd->updatee, updatee);
4031 // now mark this update frame as a stack gap. The gap
4032 // marker resides in the bottom-most update frame of
4033 // the series of adjacent frames, and covers all the
4034 // frames in this series.
4035 current_gap_size += sizeofW(StgUpdateFrame);
4036 ((struct stack_gap *)frame)->gap_size = current_gap_size;
4037 ((struct stack_gap *)frame)->next_gap = gap;
4039 frame += sizeofW(StgUpdateFrame);
4043 // single update frame, or the topmost update frame in a series
4045 StgBlockingQueue *bh = (StgBlockingQueue *)upd->updatee;
4047 // Do lazy black-holing
4048 if (bh->header.info != &stg_BLACKHOLE_info &&
4049 bh->header.info != &stg_BLACKHOLE_BQ_info &&
4050 bh->header.info != &stg_CAF_BLACKHOLE_info) {
4051 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4052 belch("Unexpected lazy BHing required at 0x%04x",(int)bh);
4055 /* zero out the slop so that the sanity checker can tell
4056 * where the next closure is.
4059 StgInfoTable *bh_info = get_itbl(bh);
4060 nat np = bh_info->layout.payload.ptrs,
4061 nw = bh_info->layout.payload.nptrs, i;
4062 /* don't zero out slop for a THUNK_SELECTOR,
4063 * because its layout info is used for a
4064 * different purpose, and it's exactly the
4065 * same size as a BLACKHOLE in any case.
4067 if (bh_info->type != THUNK_SELECTOR) {
4068 for (i = np; i < np + nw; i++) {
4069 ((StgClosure *)bh)->payload[i] = 0;
4075 // We pretend that bh is now dead.
4076 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4078 // Todo: maybe use SET_HDR() and remove LDV_recordCreate()?
4079 SET_INFO(bh,&stg_BLACKHOLE_info);
4081 // We pretend that bh has just been created.
4082 LDV_recordCreate(bh);
4086 prev_was_update_frame = rtsTrue;
4087 updatee = upd->updatee;
4088 frame += sizeofW(StgUpdateFrame);
4094 prev_was_update_frame = rtsFalse;
4096 // we're not in a gap... check whether this is the end of a gap
4097 // (an update frame can't be the end of a gap).
4098 if (current_gap_size != 0) {
4099 gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
4101 current_gap_size = 0;
4103 frame += stack_frame_sizeW((StgClosure *)frame);
4110 // Now we have a stack with gaps in it, and we have to walk down
4111 // shoving the stack up to fill in the gaps. A diagram might
4115 // | ********* | <- sp
4119 // | stack_gap | <- gap | chunk_size
4121 // | ......... | <- gap_end v
4127 // 'sp' points the the current top-of-stack
4128 // 'gap' points to the stack_gap structure inside the gap
4129 // ***** indicates real stack data
4130 // ..... indicates gap
4131 // <empty> indicates unused
4135 void *gap_start, *next_gap_start, *gap_end;
4138 next_gap_start = (void *)gap + sizeof(StgUpdateFrame);
4139 sp = next_gap_start;
4141 while ((StgPtr)gap > tso->sp) {
4143 // we're working in *bytes* now...
4144 gap_start = next_gap_start;
4145 gap_end = gap_start - gap->gap_size * sizeof(W_);
4147 gap = gap->next_gap;
4148 next_gap_start = (void *)gap + sizeof(StgUpdateFrame);
4150 chunk_size = gap_end - next_gap_start;
4152 memmove(sp, next_gap_start, chunk_size);
4155 tso->sp = (StgPtr)sp;
4159 /* -----------------------------------------------------------------------------
4162 * We have to prepare for GC - this means doing lazy black holing
4163 * here. We also take the opportunity to do stack squeezing if it's
4165 * -------------------------------------------------------------------------- */
4167 threadPaused(StgTSO *tso)
4169 if ( RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue )
4170 threadSqueezeStack(tso); // does black holing too
4172 threadLazyBlackHole(tso);
4175 /* -----------------------------------------------------------------------------
4177 * -------------------------------------------------------------------------- */
4181 printMutOnceList(generation *gen)
4183 StgMutClosure *p, *next;
4185 p = gen->mut_once_list;
4188 fprintf(stderr, "@@ Mut once list %p: ", gen->mut_once_list);
4189 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
4190 fprintf(stderr, "%p (%s), ",
4191 p, info_type((StgClosure *)p));
4193 fputc('\n', stderr);
4197 printMutableList(generation *gen)
4199 StgMutClosure *p, *next;
4204 fprintf(stderr, "@@ Mutable list %p: ", gen->mut_list);
4205 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
4206 fprintf(stderr, "%p (%s), ",
4207 p, info_type((StgClosure *)p));
4209 fputc('\n', stderr);
4212 static inline rtsBool
4213 maybeLarge(StgClosure *closure)
4215 StgInfoTable *info = get_itbl(closure);
4217 /* closure types that may be found on the new_large_objects list;
4218 see scavenge_large */
4219 return (info->type == MUT_ARR_PTRS ||
4220 info->type == MUT_ARR_PTRS_FROZEN ||
4221 info->type == TSO ||
4222 info->type == ARR_WORDS);