1 /* -----------------------------------------------------------------------------
3 * (c) The GHC Team 1998-2003
5 * Generational garbage collector
7 * ---------------------------------------------------------------------------*/
9 #include "PosixSource.h"
14 #include "OSThreads.h"
16 #include "LdvProfile.h"
21 #include "BlockAlloc.h"
27 #include "ParTicky.h" // ToDo: move into Rts.h
28 #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"
50 // Turn off inlining when debugging - it obfuscates things
53 # define STATIC_INLINE static
56 /* STATIC OBJECT LIST.
59 * We maintain a linked list of static objects that are still live.
60 * The requirements for this list are:
62 * - we need to scan the list while adding to it, in order to
63 * scavenge all the static objects (in the same way that
64 * breadth-first scavenging works for dynamic objects).
66 * - we need to be able to tell whether an object is already on
67 * the list, to break loops.
69 * Each static object has a "static link field", which we use for
70 * linking objects on to the list. We use a stack-type list, consing
71 * objects on the front as they are added (this means that the
72 * scavenge phase is depth-first, not breadth-first, but that
75 * A separate list is kept for objects that have been scavenged
76 * already - this is so that we can zero all the marks afterwards.
78 * An object is on the list if its static link field is non-zero; this
79 * means that we have to mark the end of the list with '1', not NULL.
81 * Extra notes for generational GC:
83 * Each generation has a static object list associated with it. When
84 * collecting generations up to N, we treat the static object lists
85 * from generations > N as roots.
87 * We build up a static object list while collecting generations 0..N,
88 * which is then appended to the static object list of generation N+1.
90 static StgClosure* static_objects; // live static objects
91 StgClosure* scavenged_static_objects; // static objects scavenged so far
93 /* N is the oldest generation being collected, where the generations
94 * are numbered starting at 0. A major GC (indicated by the major_gc
95 * flag) is when we're collecting all generations. We only attempt to
96 * deal with static objects and GC CAFs when doing a major GC.
99 static rtsBool major_gc;
101 /* Youngest generation that objects should be evacuated to in
102 * evacuate(). (Logically an argument to evacuate, but it's static
103 * a lot of the time so we optimise it into a global variable).
109 StgWeak *old_weak_ptr_list; // also pending finaliser list
111 /* Which stage of processing various kinds of weak pointer are we at?
112 * (see traverse_weak_ptr_list() below for discussion).
114 typedef enum { WeakPtrs, WeakThreads, WeakDone } WeakStage;
115 static WeakStage weak_stage;
117 /* List of all threads during GC
119 static StgTSO *old_all_threads;
120 StgTSO *resurrected_threads;
122 /* Flag indicating failure to evacuate an object to the desired
125 static rtsBool failed_to_evac;
127 /* Old to-space (used for two-space collector only)
129 static bdescr *old_to_blocks;
131 /* Data used for allocation area sizing.
133 static lnat new_blocks; // blocks allocated during this GC
134 static lnat g0s0_pcnt_kept = 30; // percentage of g0s0 live at last minor GC
136 /* Used to avoid long recursion due to selector thunks
138 static lnat thunk_selector_depth = 0;
139 #define MAX_THUNK_SELECTOR_DEPTH 8
141 /* -----------------------------------------------------------------------------
142 Static function declarations
143 -------------------------------------------------------------------------- */
145 static bdescr * gc_alloc_block ( step *stp );
146 static void mark_root ( StgClosure **root );
148 // Use a register argument for evacuate, if available.
150 #define REGPARM1 __attribute__((regparm(1)))
155 REGPARM1 static StgClosure * evacuate (StgClosure *q);
157 static void zero_static_object_list ( StgClosure* first_static );
159 static rtsBool traverse_weak_ptr_list ( void );
160 static void mark_weak_ptr_list ( StgWeak **list );
162 static StgClosure * eval_thunk_selector ( nat field, StgSelector * p );
165 static void scavenge ( step * );
166 static void scavenge_mark_stack ( void );
167 static void scavenge_stack ( StgPtr p, StgPtr stack_end );
168 static rtsBool scavenge_one ( StgPtr p );
169 static void scavenge_large ( step * );
170 static void scavenge_static ( void );
171 static void scavenge_mutable_list ( generation *g );
173 static void scavenge_large_bitmap ( StgPtr p,
174 StgLargeBitmap *large_bitmap,
177 #if 0 && defined(DEBUG)
178 static void gcCAFs ( void );
181 /* -----------------------------------------------------------------------------
182 inline functions etc. for dealing with the mark bitmap & stack.
183 -------------------------------------------------------------------------- */
185 #define MARK_STACK_BLOCKS 4
187 static bdescr *mark_stack_bdescr;
188 static StgPtr *mark_stack;
189 static StgPtr *mark_sp;
190 static StgPtr *mark_splim;
192 // Flag and pointers used for falling back to a linear scan when the
193 // mark stack overflows.
194 static rtsBool mark_stack_overflowed;
195 static bdescr *oldgen_scan_bd;
196 static StgPtr oldgen_scan;
198 STATIC_INLINE rtsBool
199 mark_stack_empty(void)
201 return mark_sp == mark_stack;
204 STATIC_INLINE rtsBool
205 mark_stack_full(void)
207 return mark_sp >= mark_splim;
211 reset_mark_stack(void)
213 mark_sp = mark_stack;
217 push_mark_stack(StgPtr p)
228 /* -----------------------------------------------------------------------------
229 Allocate a new to-space block in the given step.
230 -------------------------------------------------------------------------- */
233 gc_alloc_block(step *stp)
235 bdescr *bd = allocBlock();
236 bd->gen_no = stp->gen_no;
240 // blocks in to-space in generations up to and including N
241 // get the BF_EVACUATED flag.
242 if (stp->gen_no <= N) {
243 bd->flags = BF_EVACUATED;
248 // Start a new to-space block, chain it on after the previous one.
249 if (stp->hp_bd == NULL) {
252 stp->hp_bd->free = stp->hp;
253 stp->hp_bd->link = bd;
258 stp->hpLim = stp->hp + BLOCK_SIZE_W;
266 /* -----------------------------------------------------------------------------
269 Rough outline of the algorithm: for garbage collecting generation N
270 (and all younger generations):
272 - follow all pointers in the root set. the root set includes all
273 mutable objects in all generations (mutable_list).
275 - for each pointer, evacuate the object it points to into either
277 + to-space of the step given by step->to, which is the next
278 highest step in this generation or the first step in the next
279 generation if this is the last step.
281 + to-space of generations[evac_gen]->steps[0], if evac_gen != 0.
282 When we evacuate an object we attempt to evacuate
283 everything it points to into the same generation - this is
284 achieved by setting evac_gen to the desired generation. If
285 we can't do this, then an entry in the mut list has to
286 be made for the cross-generation pointer.
288 + if the object is already in a generation > N, then leave
291 - repeatedly scavenge to-space from each step in each generation
292 being collected until no more objects can be evacuated.
294 - free from-space in each step, and set from-space = to-space.
296 Locks held: sched_mutex
298 -------------------------------------------------------------------------- */
301 GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc )
305 lnat live, allocated, collected = 0, copied = 0;
306 lnat oldgen_saved_blocks = 0;
310 CostCentreStack *prev_CCS;
313 #if defined(DEBUG) && defined(GRAN)
314 IF_DEBUG(gc, debugBelch("@@ Starting garbage collection at %ld (%lx)\n",
318 #if defined(RTS_USER_SIGNALS)
323 // tell the STM to discard any cached closures its hoping to re-use
326 // tell the stats department that we've started a GC
329 // Init stats and print par specific (timing) info
330 PAR_TICKY_PAR_START();
332 // attribute any costs to CCS_GC
338 /* Approximate how much we allocated.
339 * Todo: only when generating stats?
341 allocated = calcAllocated();
343 /* Figure out which generation to collect
345 if (force_major_gc) {
346 N = RtsFlags.GcFlags.generations - 1;
350 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
351 if (generations[g].steps[0].n_blocks +
352 generations[g].steps[0].n_large_blocks
353 >= generations[g].max_blocks) {
357 major_gc = (N == RtsFlags.GcFlags.generations-1);
360 #ifdef RTS_GTK_FRONTPANEL
361 if (RtsFlags.GcFlags.frontpanel) {
362 updateFrontPanelBeforeGC(N);
366 // check stack sanity *before* GC (ToDo: check all threads)
368 // ToDo!: check sanity IF_DEBUG(sanity, checkTSOsSanity());
370 IF_DEBUG(sanity, checkFreeListSanity());
372 /* Initialise the static object lists
374 static_objects = END_OF_STATIC_LIST;
375 scavenged_static_objects = END_OF_STATIC_LIST;
377 /* Save the old to-space if we're doing a two-space collection
379 if (RtsFlags.GcFlags.generations == 1) {
380 old_to_blocks = g0s0->to_blocks;
381 g0s0->to_blocks = NULL;
382 g0s0->n_to_blocks = 0;
385 /* Keep a count of how many new blocks we allocated during this GC
386 * (used for resizing the allocation area, later).
390 // Initialise to-space in all the generations/steps that we're
393 for (g = 0; g <= N; g++) {
395 // throw away the mutable list. Invariant: the mutable list
396 // always has at least one block; this means we can avoid a check for
397 // NULL in recordMutable().
399 freeChain(generations[g].mut_list);
400 generations[g].mut_list = allocBlock();
403 for (s = 0; s < generations[g].n_steps; s++) {
405 // generation 0, step 0 doesn't need to-space
406 if (g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1) {
410 stp = &generations[g].steps[s];
411 ASSERT(stp->gen_no == g);
413 // start a new to-space for this step.
416 stp->to_blocks = NULL;
418 // allocate the first to-space block; extra blocks will be
419 // chained on as necessary.
420 bd = gc_alloc_block(stp);
422 stp->scan = bd->start;
425 // initialise the large object queues.
426 stp->new_large_objects = NULL;
427 stp->scavenged_large_objects = NULL;
428 stp->n_scavenged_large_blocks = 0;
430 // mark the large objects as not evacuated yet
431 for (bd = stp->large_objects; bd; bd = bd->link) {
432 bd->flags &= ~BF_EVACUATED;
435 // for a compacted step, we need to allocate the bitmap
436 if (stp->is_compacted) {
437 nat bitmap_size; // in bytes
438 bdescr *bitmap_bdescr;
441 bitmap_size = stp->n_blocks * BLOCK_SIZE / (sizeof(W_)*BITS_PER_BYTE);
443 if (bitmap_size > 0) {
444 bitmap_bdescr = allocGroup((lnat)BLOCK_ROUND_UP(bitmap_size)
446 stp->bitmap = bitmap_bdescr;
447 bitmap = bitmap_bdescr->start;
449 IF_DEBUG(gc, debugBelch("bitmap_size: %d, bitmap: %p",
450 bitmap_size, bitmap););
452 // don't forget to fill it with zeros!
453 memset(bitmap, 0, bitmap_size);
455 // For each block in this step, point to its bitmap from the
457 for (bd=stp->blocks; bd != NULL; bd = bd->link) {
458 bd->u.bitmap = bitmap;
459 bitmap += BLOCK_SIZE_W / (sizeof(W_)*BITS_PER_BYTE);
461 // Also at this point we set the BF_COMPACTED flag
462 // for this block. The invariant is that
463 // BF_COMPACTED is always unset, except during GC
464 // when it is set on those blocks which will be
466 bd->flags |= BF_COMPACTED;
473 /* make sure the older generations have at least one block to
474 * allocate into (this makes things easier for copy(), see below).
476 for (g = N+1; g < RtsFlags.GcFlags.generations; g++) {
477 for (s = 0; s < generations[g].n_steps; s++) {
478 stp = &generations[g].steps[s];
479 if (stp->hp_bd == NULL) {
480 ASSERT(stp->blocks == NULL);
481 bd = gc_alloc_block(stp);
485 /* Set the scan pointer for older generations: remember we
486 * still have to scavenge objects that have been promoted. */
488 stp->scan_bd = stp->hp_bd;
489 stp->to_blocks = NULL;
490 stp->n_to_blocks = 0;
491 stp->new_large_objects = NULL;
492 stp->scavenged_large_objects = NULL;
493 stp->n_scavenged_large_blocks = 0;
497 /* Allocate a mark stack if we're doing a major collection.
500 mark_stack_bdescr = allocGroup(MARK_STACK_BLOCKS);
501 mark_stack = (StgPtr *)mark_stack_bdescr->start;
502 mark_sp = mark_stack;
503 mark_splim = mark_stack + (MARK_STACK_BLOCKS * BLOCK_SIZE_W);
505 mark_stack_bdescr = NULL;
508 /* -----------------------------------------------------------------------
509 * follow all the roots that we know about:
510 * - mutable lists from each generation > N
511 * we want to *scavenge* these roots, not evacuate them: they're not
512 * going to move in this GC.
513 * Also: do them in reverse generation order. This is because we
514 * often want to promote objects that are pointed to by older
515 * generations early, so we don't have to repeatedly copy them.
516 * Doing the generations in reverse order ensures that we don't end
517 * up in the situation where we want to evac an object to gen 3 and
518 * it has already been evaced to gen 2.
522 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
523 generations[g].saved_mut_list = generations[g].mut_list;
524 generations[g].mut_list = allocBlock();
525 // mut_list always has at least one block.
528 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
529 IF_PAR_DEBUG(verbose, printMutableList(&generations[g]));
530 scavenge_mutable_list(&generations[g]);
532 for (st = generations[g].n_steps-1; st >= 0; st--) {
533 scavenge(&generations[g].steps[st]);
538 /* follow roots from the CAF list (used by GHCi)
543 /* follow all the roots that the application knows about.
546 get_roots(mark_root);
549 /* And don't forget to mark the TSO if we got here direct from
551 /* Not needed in a seq version?
553 CurrentTSO = (StgTSO *)MarkRoot((StgClosure *)CurrentTSO);
557 // Mark the entries in the GALA table of the parallel system
558 markLocalGAs(major_gc);
559 // Mark all entries on the list of pending fetches
560 markPendingFetches(major_gc);
563 /* Mark the weak pointer list, and prepare to detect dead weak
566 mark_weak_ptr_list(&weak_ptr_list);
567 old_weak_ptr_list = weak_ptr_list;
568 weak_ptr_list = NULL;
569 weak_stage = WeakPtrs;
571 /* The all_threads list is like the weak_ptr_list.
572 * See traverse_weak_ptr_list() for the details.
574 old_all_threads = all_threads;
575 all_threads = END_TSO_QUEUE;
576 resurrected_threads = END_TSO_QUEUE;
578 /* Mark the stable pointer table.
580 markStablePtrTable(mark_root);
582 /* -------------------------------------------------------------------------
583 * Repeatedly scavenge all the areas we know about until there's no
584 * more scavenging to be done.
591 // scavenge static objects
592 if (major_gc && static_objects != END_OF_STATIC_LIST) {
593 IF_DEBUG(sanity, checkStaticObjects(static_objects));
597 /* When scavenging the older generations: Objects may have been
598 * evacuated from generations <= N into older generations, and we
599 * need to scavenge these objects. We're going to try to ensure that
600 * any evacuations that occur move the objects into at least the
601 * same generation as the object being scavenged, otherwise we
602 * have to create new entries on the mutable list for the older
606 // scavenge each step in generations 0..maxgen
612 // scavenge objects in compacted generation
613 if (mark_stack_overflowed || oldgen_scan_bd != NULL ||
614 (mark_stack_bdescr != NULL && !mark_stack_empty())) {
615 scavenge_mark_stack();
619 for (gen = RtsFlags.GcFlags.generations; --gen >= 0; ) {
620 for (st = generations[gen].n_steps; --st >= 0; ) {
621 if (gen == 0 && st == 0 && RtsFlags.GcFlags.generations > 1) {
624 stp = &generations[gen].steps[st];
626 if (stp->hp_bd != stp->scan_bd || stp->scan < stp->hp) {
631 if (stp->new_large_objects != NULL) {
640 if (flag) { goto loop; }
642 // must be last... invariant is that everything is fully
643 // scavenged at this point.
644 if (traverse_weak_ptr_list()) { // returns rtsTrue if evaced something
649 /* Update the pointers from the "main thread" list - these are
650 * treated as weak pointers because we want to allow a main thread
651 * to get a BlockedOnDeadMVar exception in the same way as any other
652 * thread. Note that the threads should all have been retained by
653 * GC by virtue of being on the all_threads list, we're just
654 * updating pointers here.
659 for (m = main_threads; m != NULL; m = m->link) {
660 tso = (StgTSO *) isAlive((StgClosure *)m->tso);
662 barf("main thread has been GC'd");
669 // Reconstruct the Global Address tables used in GUM
670 rebuildGAtables(major_gc);
671 IF_DEBUG(sanity, checkLAGAtable(rtsTrue/*check closures, too*/));
674 // Now see which stable names are still alive.
677 // Tidy the end of the to-space chains
678 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
679 for (s = 0; s < generations[g].n_steps; s++) {
680 stp = &generations[g].steps[s];
681 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
682 ASSERT(Bdescr(stp->hp) == stp->hp_bd);
683 stp->hp_bd->free = stp->hp;
689 // We call processHeapClosureForDead() on every closure destroyed during
690 // the current garbage collection, so we invoke LdvCensusForDead().
691 if (RtsFlags.ProfFlags.doHeapProfile == HEAP_BY_LDV
692 || RtsFlags.ProfFlags.bioSelector != NULL)
696 // NO MORE EVACUATION AFTER THIS POINT!
697 // Finally: compaction of the oldest generation.
698 if (major_gc && oldest_gen->steps[0].is_compacted) {
699 // save number of blocks for stats
700 oldgen_saved_blocks = oldest_gen->steps[0].n_blocks;
704 IF_DEBUG(sanity, checkGlobalTSOList(rtsFalse));
706 /* run through all the generations/steps and tidy up
708 copied = new_blocks * BLOCK_SIZE_W;
709 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
712 generations[g].collections++; // for stats
715 // Count the mutable list as bytes "copied" for the purposes of
716 // stats. Every mutable list is copied during every GC.
718 for (bd = generations[g].mut_list; bd != NULL; bd = bd->link) {
719 copied += (bd->free - bd->start) * sizeof(StgWord);
723 for (s = 0; s < generations[g].n_steps; s++) {
725 stp = &generations[g].steps[s];
727 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
728 // stats information: how much we copied
730 copied -= stp->hp_bd->start + BLOCK_SIZE_W -
735 // for generations we collected...
738 // rough calculation of garbage collected, for stats output
739 if (stp->is_compacted) {
740 collected += (oldgen_saved_blocks - stp->n_blocks) * BLOCK_SIZE_W;
742 collected += stp->n_blocks * BLOCK_SIZE_W;
745 /* free old memory and shift to-space into from-space for all
746 * the collected steps (except the allocation area). These
747 * freed blocks will probaby be quickly recycled.
749 if (!(g == 0 && s == 0)) {
750 if (stp->is_compacted) {
751 // for a compacted step, just shift the new to-space
752 // onto the front of the now-compacted existing blocks.
753 for (bd = stp->to_blocks; bd != NULL; bd = bd->link) {
754 bd->flags &= ~BF_EVACUATED; // now from-space
756 // tack the new blocks on the end of the existing blocks
757 if (stp->blocks == NULL) {
758 stp->blocks = stp->to_blocks;
760 for (bd = stp->blocks; bd != NULL; bd = next) {
763 bd->link = stp->to_blocks;
765 // NB. this step might not be compacted next
766 // time, so reset the BF_COMPACTED flags.
767 // They are set before GC if we're going to
768 // compact. (search for BF_COMPACTED above).
769 bd->flags &= ~BF_COMPACTED;
772 // add the new blocks to the block tally
773 stp->n_blocks += stp->n_to_blocks;
775 freeChain(stp->blocks);
776 stp->blocks = stp->to_blocks;
777 stp->n_blocks = stp->n_to_blocks;
778 for (bd = stp->blocks; bd != NULL; bd = bd->link) {
779 bd->flags &= ~BF_EVACUATED; // now from-space
782 stp->to_blocks = NULL;
783 stp->n_to_blocks = 0;
786 /* LARGE OBJECTS. The current live large objects are chained on
787 * scavenged_large, having been moved during garbage
788 * collection from large_objects. Any objects left on
789 * large_objects list are therefore dead, so we free them here.
791 for (bd = stp->large_objects; bd != NULL; bd = next) {
797 // update the count of blocks used by large objects
798 for (bd = stp->scavenged_large_objects; bd != NULL; bd = bd->link) {
799 bd->flags &= ~BF_EVACUATED;
801 stp->large_objects = stp->scavenged_large_objects;
802 stp->n_large_blocks = stp->n_scavenged_large_blocks;
805 // for older generations...
807 /* For older generations, we need to append the
808 * scavenged_large_object list (i.e. large objects that have been
809 * promoted during this GC) to the large_object list for that step.
811 for (bd = stp->scavenged_large_objects; bd; bd = next) {
813 bd->flags &= ~BF_EVACUATED;
814 dbl_link_onto(bd, &stp->large_objects);
817 // add the new blocks we promoted during this GC
818 stp->n_blocks += stp->n_to_blocks;
819 stp->n_to_blocks = 0;
820 stp->n_large_blocks += stp->n_scavenged_large_blocks;
825 /* Reset the sizes of the older generations when we do a major
828 * CURRENT STRATEGY: make all generations except zero the same size.
829 * We have to stay within the maximum heap size, and leave a certain
830 * percentage of the maximum heap size available to allocate into.
832 if (major_gc && RtsFlags.GcFlags.generations > 1) {
833 nat live, size, min_alloc;
834 nat max = RtsFlags.GcFlags.maxHeapSize;
835 nat gens = RtsFlags.GcFlags.generations;
837 // live in the oldest generations
838 live = oldest_gen->steps[0].n_blocks +
839 oldest_gen->steps[0].n_large_blocks;
841 // default max size for all generations except zero
842 size = stg_max(live * RtsFlags.GcFlags.oldGenFactor,
843 RtsFlags.GcFlags.minOldGenSize);
845 // minimum size for generation zero
846 min_alloc = stg_max((RtsFlags.GcFlags.pcFreeHeap * max) / 200,
847 RtsFlags.GcFlags.minAllocAreaSize);
849 // Auto-enable compaction when the residency reaches a
850 // certain percentage of the maximum heap size (default: 30%).
851 if (RtsFlags.GcFlags.generations > 1 &&
852 (RtsFlags.GcFlags.compact ||
854 oldest_gen->steps[0].n_blocks >
855 (RtsFlags.GcFlags.compactThreshold * max) / 100))) {
856 oldest_gen->steps[0].is_compacted = 1;
857 // debugBelch("compaction: on\n", live);
859 oldest_gen->steps[0].is_compacted = 0;
860 // debugBelch("compaction: off\n", live);
863 // if we're going to go over the maximum heap size, reduce the
864 // size of the generations accordingly. The calculation is
865 // different if compaction is turned on, because we don't need
866 // to double the space required to collect the old generation.
869 // this test is necessary to ensure that the calculations
870 // below don't have any negative results - we're working
871 // with unsigned values here.
872 if (max < min_alloc) {
876 if (oldest_gen->steps[0].is_compacted) {
877 if ( (size + (size - 1) * (gens - 2) * 2) + min_alloc > max ) {
878 size = (max - min_alloc) / ((gens - 1) * 2 - 1);
881 if ( (size * (gens - 1) * 2) + min_alloc > max ) {
882 size = (max - min_alloc) / ((gens - 1) * 2);
892 debugBelch("live: %d, min_alloc: %d, size : %d, max = %d\n", live,
893 min_alloc, size, max);
896 for (g = 0; g < gens; g++) {
897 generations[g].max_blocks = size;
901 // Guess the amount of live data for stats.
904 /* Free the small objects allocated via allocate(), since this will
905 * all have been copied into G0S1 now.
907 if (small_alloc_list != NULL) {
908 freeChain(small_alloc_list);
910 small_alloc_list = NULL;
914 alloc_blocks_lim = RtsFlags.GcFlags.minAllocAreaSize;
916 // Start a new pinned_object_block
917 pinned_object_block = NULL;
919 /* Free the mark stack.
921 if (mark_stack_bdescr != NULL) {
922 freeGroup(mark_stack_bdescr);
927 for (g = 0; g <= N; g++) {
928 for (s = 0; s < generations[g].n_steps; s++) {
929 stp = &generations[g].steps[s];
930 if (stp->is_compacted && stp->bitmap != NULL) {
931 freeGroup(stp->bitmap);
936 /* Two-space collector:
937 * Free the old to-space, and estimate the amount of live data.
939 if (RtsFlags.GcFlags.generations == 1) {
942 if (old_to_blocks != NULL) {
943 freeChain(old_to_blocks);
945 for (bd = g0s0->to_blocks; bd != NULL; bd = bd->link) {
946 bd->flags = 0; // now from-space
949 /* For a two-space collector, we need to resize the nursery. */
951 /* set up a new nursery. Allocate a nursery size based on a
952 * function of the amount of live data (by default a factor of 2)
953 * Use the blocks from the old nursery if possible, freeing up any
956 * If we get near the maximum heap size, then adjust our nursery
957 * size accordingly. If the nursery is the same size as the live
958 * data (L), then we need 3L bytes. We can reduce the size of the
959 * nursery to bring the required memory down near 2L bytes.
961 * A normal 2-space collector would need 4L bytes to give the same
962 * performance we get from 3L bytes, reducing to the same
963 * performance at 2L bytes.
965 blocks = g0s0->n_to_blocks;
967 if ( RtsFlags.GcFlags.maxHeapSize != 0 &&
968 blocks * RtsFlags.GcFlags.oldGenFactor * 2 >
969 RtsFlags.GcFlags.maxHeapSize ) {
970 long adjusted_blocks; // signed on purpose
973 adjusted_blocks = (RtsFlags.GcFlags.maxHeapSize - 2 * blocks);
974 IF_DEBUG(gc, debugBelch("@@ Near maximum heap size of 0x%x blocks, blocks = %d, adjusted to %ld", RtsFlags.GcFlags.maxHeapSize, blocks, adjusted_blocks));
975 pc_free = adjusted_blocks * 100 / RtsFlags.GcFlags.maxHeapSize;
976 if (pc_free < RtsFlags.GcFlags.pcFreeHeap) /* might even be < 0 */ {
979 blocks = adjusted_blocks;
982 blocks *= RtsFlags.GcFlags.oldGenFactor;
983 if (blocks < RtsFlags.GcFlags.minAllocAreaSize) {
984 blocks = RtsFlags.GcFlags.minAllocAreaSize;
987 resizeNurseries(blocks);
990 /* Generational collector:
991 * If the user has given us a suggested heap size, adjust our
992 * allocation area to make best use of the memory available.
995 if (RtsFlags.GcFlags.heapSizeSuggestion) {
997 nat needed = calcNeeded(); // approx blocks needed at next GC
999 /* Guess how much will be live in generation 0 step 0 next time.
1000 * A good approximation is obtained by finding the
1001 * percentage of g0s0 that was live at the last minor GC.
1004 g0s0_pcnt_kept = (new_blocks * 100) / countNurseryBlocks();
1007 /* Estimate a size for the allocation area based on the
1008 * information available. We might end up going slightly under
1009 * or over the suggested heap size, but we should be pretty
1012 * Formula: suggested - needed
1013 * ----------------------------
1014 * 1 + g0s0_pcnt_kept/100
1016 * where 'needed' is the amount of memory needed at the next
1017 * collection for collecting all steps except g0s0.
1020 (((long)RtsFlags.GcFlags.heapSizeSuggestion - (long)needed) * 100) /
1021 (100 + (long)g0s0_pcnt_kept);
1023 if (blocks < (long)RtsFlags.GcFlags.minAllocAreaSize) {
1024 blocks = RtsFlags.GcFlags.minAllocAreaSize;
1027 resizeNurseries((nat)blocks);
1030 // we might have added extra large blocks to the nursery, so
1031 // resize back to minAllocAreaSize again.
1032 resizeNurseriesFixed(RtsFlags.GcFlags.minAllocAreaSize);
1036 // mark the garbage collected CAFs as dead
1037 #if 0 && defined(DEBUG) // doesn't work at the moment
1038 if (major_gc) { gcCAFs(); }
1042 // resetStaticObjectForRetainerProfiling() must be called before
1044 resetStaticObjectForRetainerProfiling();
1047 // zero the scavenged static object list
1049 zero_static_object_list(scavenged_static_objects);
1052 // Reset the nursery
1055 RELEASE_LOCK(&sched_mutex);
1057 // start any pending finalizers
1058 scheduleFinalizers(old_weak_ptr_list);
1060 // send exceptions to any threads which were about to die
1061 resurrectThreads(resurrected_threads);
1063 ACQUIRE_LOCK(&sched_mutex);
1065 // Update the stable pointer hash table.
1066 updateStablePtrTable(major_gc);
1068 // check sanity after GC
1069 IF_DEBUG(sanity, checkSanity());
1071 // extra GC trace info
1072 IF_DEBUG(gc, statDescribeGens());
1075 // symbol-table based profiling
1076 /* heapCensus(to_blocks); */ /* ToDo */
1079 // restore enclosing cost centre
1084 // check for memory leaks if sanity checking is on
1085 IF_DEBUG(sanity, memInventory());
1087 #ifdef RTS_GTK_FRONTPANEL
1088 if (RtsFlags.GcFlags.frontpanel) {
1089 updateFrontPanelAfterGC( N, live );
1093 // ok, GC over: tell the stats department what happened.
1094 stat_endGC(allocated, collected, live, copied, N);
1096 #if defined(RTS_USER_SIGNALS)
1097 // unblock signals again
1098 unblockUserSignals();
1105 /* -----------------------------------------------------------------------------
1108 traverse_weak_ptr_list is called possibly many times during garbage
1109 collection. It returns a flag indicating whether it did any work
1110 (i.e. called evacuate on any live pointers).
1112 Invariant: traverse_weak_ptr_list is called when the heap is in an
1113 idempotent state. That means that there are no pending
1114 evacuate/scavenge operations. This invariant helps the weak
1115 pointer code decide which weak pointers are dead - if there are no
1116 new live weak pointers, then all the currently unreachable ones are
1119 For generational GC: we just don't try to finalize weak pointers in
1120 older generations than the one we're collecting. This could
1121 probably be optimised by keeping per-generation lists of weak
1122 pointers, but for a few weak pointers this scheme will work.
1124 There are three distinct stages to processing weak pointers:
1126 - weak_stage == WeakPtrs
1128 We process all the weak pointers whos keys are alive (evacuate
1129 their values and finalizers), and repeat until we can find no new
1130 live keys. If no live keys are found in this pass, then we
1131 evacuate the finalizers of all the dead weak pointers in order to
1134 - weak_stage == WeakThreads
1136 Now, we discover which *threads* are still alive. Pointers to
1137 threads from the all_threads and main thread lists are the
1138 weakest of all: a pointers from the finalizer of a dead weak
1139 pointer can keep a thread alive. Any threads found to be unreachable
1140 are evacuated and placed on the resurrected_threads list so we
1141 can send them a signal later.
1143 - weak_stage == WeakDone
1145 No more evacuation is done.
1147 -------------------------------------------------------------------------- */
1150 traverse_weak_ptr_list(void)
1152 StgWeak *w, **last_w, *next_w;
1154 rtsBool flag = rtsFalse;
1156 switch (weak_stage) {
1162 /* doesn't matter where we evacuate values/finalizers to, since
1163 * these pointers are treated as roots (iff the keys are alive).
1167 last_w = &old_weak_ptr_list;
1168 for (w = old_weak_ptr_list; w != NULL; w = next_w) {
1170 /* There might be a DEAD_WEAK on the list if finalizeWeak# was
1171 * called on a live weak pointer object. Just remove it.
1173 if (w->header.info == &stg_DEAD_WEAK_info) {
1174 next_w = ((StgDeadWeak *)w)->link;
1179 switch (get_itbl(w)->type) {
1182 next_w = (StgWeak *)((StgEvacuated *)w)->evacuee;
1187 /* Now, check whether the key is reachable.
1189 new = isAlive(w->key);
1192 // evacuate the value and finalizer
1193 w->value = evacuate(w->value);
1194 w->finalizer = evacuate(w->finalizer);
1195 // remove this weak ptr from the old_weak_ptr list
1197 // and put it on the new weak ptr list
1199 w->link = weak_ptr_list;
1202 IF_DEBUG(weak, debugBelch("Weak pointer still alive at %p -> %p",
1207 last_w = &(w->link);
1213 barf("traverse_weak_ptr_list: not WEAK");
1217 /* If we didn't make any changes, then we can go round and kill all
1218 * the dead weak pointers. The old_weak_ptr list is used as a list
1219 * of pending finalizers later on.
1221 if (flag == rtsFalse) {
1222 for (w = old_weak_ptr_list; w; w = w->link) {
1223 w->finalizer = evacuate(w->finalizer);
1226 // Next, move to the WeakThreads stage after fully
1227 // scavenging the finalizers we've just evacuated.
1228 weak_stage = WeakThreads;
1234 /* Now deal with the all_threads list, which behaves somewhat like
1235 * the weak ptr list. If we discover any threads that are about to
1236 * become garbage, we wake them up and administer an exception.
1239 StgTSO *t, *tmp, *next, **prev;
1241 prev = &old_all_threads;
1242 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1244 tmp = (StgTSO *)isAlive((StgClosure *)t);
1250 ASSERT(get_itbl(t)->type == TSO);
1251 switch (t->what_next) {
1252 case ThreadRelocated:
1257 case ThreadComplete:
1258 // finshed or died. The thread might still be alive, but we
1259 // don't keep it on the all_threads list. Don't forget to
1260 // stub out its global_link field.
1261 next = t->global_link;
1262 t->global_link = END_TSO_QUEUE;
1269 // Threads blocked on black holes: if the black hole
1270 // is alive, then the thread is alive too.
1271 if (tmp == NULL && t->why_blocked == BlockedOnBlackHole) {
1272 if (isAlive(t->block_info.closure)) {
1273 t = (StgTSO *)evacuate((StgClosure *)t);
1280 // not alive (yet): leave this thread on the
1281 // old_all_threads list.
1282 prev = &(t->global_link);
1283 next = t->global_link;
1286 // alive: move this thread onto the all_threads list.
1287 next = t->global_link;
1288 t->global_link = all_threads;
1295 /* If we evacuated any threads, we need to go back to the scavenger.
1297 if (flag) return rtsTrue;
1299 /* And resurrect any threads which were about to become garbage.
1302 StgTSO *t, *tmp, *next;
1303 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1304 next = t->global_link;
1305 tmp = (StgTSO *)evacuate((StgClosure *)t);
1306 tmp->global_link = resurrected_threads;
1307 resurrected_threads = tmp;
1311 /* Finally, we can update the blackhole_queue. This queue
1312 * simply strings together TSOs blocked on black holes, it is
1313 * not intended to keep anything alive. Hence, we do not follow
1314 * pointers on the blackhole_queue until now, when we have
1315 * determined which TSOs are otherwise reachable. We know at
1316 * this point that all TSOs have been evacuated, however.
1320 for (pt = &blackhole_queue; *pt != END_TSO_QUEUE; pt = &((*pt)->link)) {
1321 *pt = (StgTSO *)isAlive((StgClosure *)*pt);
1322 ASSERT(*pt != NULL);
1326 weak_stage = WeakDone; // *now* we're done,
1327 return rtsTrue; // but one more round of scavenging, please
1330 barf("traverse_weak_ptr_list");
1336 /* -----------------------------------------------------------------------------
1337 After GC, the live weak pointer list may have forwarding pointers
1338 on it, because a weak pointer object was evacuated after being
1339 moved to the live weak pointer list. We remove those forwarding
1342 Also, we don't consider weak pointer objects to be reachable, but
1343 we must nevertheless consider them to be "live" and retain them.
1344 Therefore any weak pointer objects which haven't as yet been
1345 evacuated need to be evacuated now.
1346 -------------------------------------------------------------------------- */
1350 mark_weak_ptr_list ( StgWeak **list )
1352 StgWeak *w, **last_w;
1355 for (w = *list; w; w = w->link) {
1356 // w might be WEAK, EVACUATED, or DEAD_WEAK (actually CON_STATIC) here
1357 ASSERT(w->header.info == &stg_DEAD_WEAK_info
1358 || get_itbl(w)->type == WEAK || get_itbl(w)->type == EVACUATED);
1359 w = (StgWeak *)evacuate((StgClosure *)w);
1361 last_w = &(w->link);
1365 /* -----------------------------------------------------------------------------
1366 isAlive determines whether the given closure is still alive (after
1367 a garbage collection) or not. It returns the new address of the
1368 closure if it is alive, or NULL otherwise.
1370 NOTE: Use it before compaction only!
1371 -------------------------------------------------------------------------- */
1375 isAlive(StgClosure *p)
1377 const StgInfoTable *info;
1382 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
1385 // ignore static closures
1387 // ToDo: for static closures, check the static link field.
1388 // Problem here is that we sometimes don't set the link field, eg.
1389 // for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
1391 if (!HEAP_ALLOCED(p)) {
1395 // ignore closures in generations that we're not collecting.
1397 if (bd->gen_no > N) {
1401 // if it's a pointer into to-space, then we're done
1402 if (bd->flags & BF_EVACUATED) {
1406 // large objects use the evacuated flag
1407 if (bd->flags & BF_LARGE) {
1411 // check the mark bit for compacted steps
1412 if ((bd->flags & BF_COMPACTED) && is_marked((P_)p,bd)) {
1416 switch (info->type) {
1421 case IND_OLDGEN: // rely on compatible layout with StgInd
1422 case IND_OLDGEN_PERM:
1423 // follow indirections
1424 p = ((StgInd *)p)->indirectee;
1429 return ((StgEvacuated *)p)->evacuee;
1432 if (((StgTSO *)p)->what_next == ThreadRelocated) {
1433 p = (StgClosure *)((StgTSO *)p)->link;
1446 mark_root(StgClosure **root)
1448 *root = evacuate(*root);
1452 upd_evacuee(StgClosure *p, StgClosure *dest)
1454 // not true: (ToDo: perhaps it should be)
1455 // ASSERT(Bdescr((P_)dest)->flags & BF_EVACUATED);
1456 SET_INFO(p, &stg_EVACUATED_info);
1457 ((StgEvacuated *)p)->evacuee = dest;
1461 STATIC_INLINE StgClosure *
1462 copy(StgClosure *src, nat size, step *stp)
1467 nat size_org = size;
1470 TICK_GC_WORDS_COPIED(size);
1471 /* Find out where we're going, using the handy "to" pointer in
1472 * the step of the source object. If it turns out we need to
1473 * evacuate to an older generation, adjust it here (see comment
1476 if (stp->gen_no < evac_gen) {
1477 #ifdef NO_EAGER_PROMOTION
1478 failed_to_evac = rtsTrue;
1480 stp = &generations[evac_gen].steps[0];
1484 /* chain a new block onto the to-space for the destination step if
1487 if (stp->hp + size >= stp->hpLim) {
1488 gc_alloc_block(stp);
1491 for(to = stp->hp, from = (P_)src; size>0; --size) {
1497 upd_evacuee(src,(StgClosure *)dest);
1499 // We store the size of the just evacuated object in the LDV word so that
1500 // the profiler can guess the position of the next object later.
1501 SET_EVACUAEE_FOR_LDV(src, size_org);
1503 return (StgClosure *)dest;
1506 /* Special version of copy() for when we only want to copy the info
1507 * pointer of an object, but reserve some padding after it. This is
1508 * used to optimise evacuation of BLACKHOLEs.
1513 copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *stp)
1518 nat size_to_copy_org = size_to_copy;
1521 TICK_GC_WORDS_COPIED(size_to_copy);
1522 if (stp->gen_no < evac_gen) {
1523 #ifdef NO_EAGER_PROMOTION
1524 failed_to_evac = rtsTrue;
1526 stp = &generations[evac_gen].steps[0];
1530 if (stp->hp + size_to_reserve >= stp->hpLim) {
1531 gc_alloc_block(stp);
1534 for(to = stp->hp, from = (P_)src; size_to_copy>0; --size_to_copy) {
1539 stp->hp += size_to_reserve;
1540 upd_evacuee(src,(StgClosure *)dest);
1542 // We store the size of the just evacuated object in the LDV word so that
1543 // the profiler can guess the position of the next object later.
1544 // size_to_copy_org is wrong because the closure already occupies size_to_reserve
1546 SET_EVACUAEE_FOR_LDV(src, size_to_reserve);
1548 if (size_to_reserve - size_to_copy_org > 0)
1549 FILL_SLOP(stp->hp - 1, (int)(size_to_reserve - size_to_copy_org));
1551 return (StgClosure *)dest;
1555 /* -----------------------------------------------------------------------------
1556 Evacuate a large object
1558 This just consists of removing the object from the (doubly-linked)
1559 step->large_objects list, and linking it on to the (singly-linked)
1560 step->new_large_objects list, from where it will be scavenged later.
1562 Convention: bd->flags has BF_EVACUATED set for a large object
1563 that has been evacuated, or unset otherwise.
1564 -------------------------------------------------------------------------- */
1568 evacuate_large(StgPtr p)
1570 bdescr *bd = Bdescr(p);
1573 // object must be at the beginning of the block (or be a ByteArray)
1574 ASSERT(get_itbl((StgClosure *)p)->type == ARR_WORDS ||
1575 (((W_)p & BLOCK_MASK) == 0));
1577 // already evacuated?
1578 if (bd->flags & BF_EVACUATED) {
1579 /* Don't forget to set the failed_to_evac flag if we didn't get
1580 * the desired destination (see comments in evacuate()).
1582 if (bd->gen_no < evac_gen) {
1583 failed_to_evac = rtsTrue;
1584 TICK_GC_FAILED_PROMOTION();
1590 // remove from large_object list
1592 bd->u.back->link = bd->link;
1593 } else { // first object in the list
1594 stp->large_objects = bd->link;
1597 bd->link->u.back = bd->u.back;
1600 /* link it on to the evacuated large object list of the destination step
1603 if (stp->gen_no < evac_gen) {
1604 #ifdef NO_EAGER_PROMOTION
1605 failed_to_evac = rtsTrue;
1607 stp = &generations[evac_gen].steps[0];
1612 bd->gen_no = stp->gen_no;
1613 bd->link = stp->new_large_objects;
1614 stp->new_large_objects = bd;
1615 bd->flags |= BF_EVACUATED;
1618 /* -----------------------------------------------------------------------------
1621 This is called (eventually) for every live object in the system.
1623 The caller to evacuate specifies a desired generation in the
1624 evac_gen global variable. The following conditions apply to
1625 evacuating an object which resides in generation M when we're
1626 collecting up to generation N
1630 else evac to step->to
1632 if M < evac_gen evac to evac_gen, step 0
1634 if the object is already evacuated, then we check which generation
1637 if M >= evac_gen do nothing
1638 if M < evac_gen set failed_to_evac flag to indicate that we
1639 didn't manage to evacuate this object into evac_gen.
1644 evacuate() is the single most important function performance-wise
1645 in the GC. Various things have been tried to speed it up, but as
1646 far as I can tell the code generated by gcc 3.2 with -O2 is about
1647 as good as it's going to get. We pass the argument to evacuate()
1648 in a register using the 'regparm' attribute (see the prototype for
1649 evacuate() near the top of this file).
1651 Changing evacuate() to take an (StgClosure **) rather than
1652 returning the new pointer seems attractive, because we can avoid
1653 writing back the pointer when it hasn't changed (eg. for a static
1654 object, or an object in a generation > N). However, I tried it and
1655 it doesn't help. One reason is that the (StgClosure **) pointer
1656 gets spilled to the stack inside evacuate(), resulting in far more
1657 extra reads/writes than we save.
1658 -------------------------------------------------------------------------- */
1660 REGPARM1 static StgClosure *
1661 evacuate(StgClosure *q)
1668 const StgInfoTable *info;
1671 if (HEAP_ALLOCED(q)) {
1674 if (bd->gen_no > N) {
1675 /* Can't evacuate this object, because it's in a generation
1676 * older than the ones we're collecting. Let's hope that it's
1677 * in evac_gen or older, or we will have to arrange to track
1678 * this pointer using the mutable list.
1680 if (bd->gen_no < evac_gen) {
1682 failed_to_evac = rtsTrue;
1683 TICK_GC_FAILED_PROMOTION();
1688 /* evacuate large objects by re-linking them onto a different list.
1690 if (bd->flags & BF_LARGE) {
1692 if (info->type == TSO &&
1693 ((StgTSO *)q)->what_next == ThreadRelocated) {
1694 q = (StgClosure *)((StgTSO *)q)->link;
1697 evacuate_large((P_)q);
1701 /* If the object is in a step that we're compacting, then we
1702 * need to use an alternative evacuate procedure.
1704 if (bd->flags & BF_COMPACTED) {
1705 if (!is_marked((P_)q,bd)) {
1707 if (mark_stack_full()) {
1708 mark_stack_overflowed = rtsTrue;
1711 push_mark_stack((P_)q);
1716 /* Object is not already evacuated. */
1717 ASSERT((bd->flags & BF_EVACUATED) == 0);
1722 else stp = NULL; // make sure copy() will crash if HEAP_ALLOCED is wrong
1725 // make sure the info pointer is into text space
1726 ASSERT(LOOKS_LIKE_CLOSURE_PTR(q));
1729 switch (info -> type) {
1733 return copy(q,sizeW_fromITBL(info),stp);
1737 StgWord w = (StgWord)q->payload[0];
1738 if (q->header.info == Czh_con_info &&
1739 // unsigned, so always true: (StgChar)w >= MIN_CHARLIKE &&
1740 (StgChar)w <= MAX_CHARLIKE) {
1741 return (StgClosure *)CHARLIKE_CLOSURE((StgChar)w);
1743 if (q->header.info == Izh_con_info &&
1744 (StgInt)w >= MIN_INTLIKE && (StgInt)w <= MAX_INTLIKE) {
1745 return (StgClosure *)INTLIKE_CLOSURE((StgInt)w);
1747 // else, fall through ...
1753 return copy(q,sizeofW(StgHeader)+1,stp);
1757 return copy(q,sizeofW(StgThunk)+1,stp);
1762 #ifdef NO_PROMOTE_THUNKS
1763 if (bd->gen_no == 0 &&
1764 bd->step->no != 0 &&
1765 bd->step->no == generations[bd->gen_no].n_steps-1) {
1769 return copy(q,sizeofW(StgThunk)+2,stp);
1777 return copy(q,sizeofW(StgHeader)+2,stp);
1780 return copy(q,thunk_sizeW_fromITBL(info),stp);
1785 case IND_OLDGEN_PERM:
1789 return copy(q,sizeW_fromITBL(info),stp);
1792 return copy(q,bco_sizeW((StgBCO *)q),stp);
1795 case SE_CAF_BLACKHOLE:
1798 return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
1800 case THUNK_SELECTOR:
1804 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
1805 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1808 p = eval_thunk_selector(info->layout.selector_offset,
1812 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1814 // q is still BLACKHOLE'd.
1815 thunk_selector_depth++;
1817 thunk_selector_depth--;
1820 // We store the size of the just evacuated object in the
1821 // LDV word so that the profiler can guess the position of
1822 // the next object later.
1823 SET_EVACUAEE_FOR_LDV(q, THUNK_SELECTOR_sizeW());
1831 // follow chains of indirections, don't evacuate them
1832 q = ((StgInd*)q)->indirectee;
1836 if (info->srt_bitmap != 0 && major_gc &&
1837 *THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
1838 *THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
1839 static_objects = (StgClosure *)q;
1844 if (info->srt_bitmap != 0 && major_gc &&
1845 *FUN_STATIC_LINK((StgClosure *)q) == NULL) {
1846 *FUN_STATIC_LINK((StgClosure *)q) = static_objects;
1847 static_objects = (StgClosure *)q;
1852 /* If q->saved_info != NULL, then it's a revertible CAF - it'll be
1853 * on the CAF list, so don't do anything with it here (we'll
1854 * scavenge it later).
1857 && ((StgIndStatic *)q)->saved_info == NULL
1858 && *IND_STATIC_LINK((StgClosure *)q) == NULL) {
1859 *IND_STATIC_LINK((StgClosure *)q) = static_objects;
1860 static_objects = (StgClosure *)q;
1865 if (major_gc && *STATIC_LINK(info,(StgClosure *)q) == NULL) {
1866 *STATIC_LINK(info,(StgClosure *)q) = static_objects;
1867 static_objects = (StgClosure *)q;
1871 case CONSTR_INTLIKE:
1872 case CONSTR_CHARLIKE:
1873 case CONSTR_NOCAF_STATIC:
1874 /* no need to put these on the static linked list, they don't need
1888 case CATCH_STM_FRAME:
1889 case CATCH_RETRY_FRAME:
1890 case ATOMICALLY_FRAME:
1891 // shouldn't see these
1892 barf("evacuate: stack frame at %p\n", q);
1895 return copy(q,pap_sizeW((StgPAP*)q),stp);
1898 return copy(q,ap_sizeW((StgAP*)q),stp);
1901 return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp);
1904 /* Already evacuated, just return the forwarding address.
1905 * HOWEVER: if the requested destination generation (evac_gen) is
1906 * older than the actual generation (because the object was
1907 * already evacuated to a younger generation) then we have to
1908 * set the failed_to_evac flag to indicate that we couldn't
1909 * manage to promote the object to the desired generation.
1911 if (evac_gen > 0) { // optimisation
1912 StgClosure *p = ((StgEvacuated*)q)->evacuee;
1913 if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < evac_gen) {
1914 failed_to_evac = rtsTrue;
1915 TICK_GC_FAILED_PROMOTION();
1918 return ((StgEvacuated*)q)->evacuee;
1921 // just copy the block
1922 return copy(q,arr_words_sizeW((StgArrWords *)q),stp);
1925 case MUT_ARR_PTRS_FROZEN:
1926 case MUT_ARR_PTRS_FROZEN0:
1927 // just copy the block
1928 return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
1932 StgTSO *tso = (StgTSO *)q;
1934 /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
1936 if (tso->what_next == ThreadRelocated) {
1937 q = (StgClosure *)tso->link;
1941 /* To evacuate a small TSO, we need to relocate the update frame
1948 new_tso = (StgTSO *)copyPart((StgClosure *)tso,
1950 sizeofW(StgTSO), stp);
1951 move_TSO(tso, new_tso);
1952 for (p = tso->sp, q = new_tso->sp;
1953 p < tso->stack+tso->stack_size;) {
1957 return (StgClosure *)new_tso;
1964 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
1965 to = copy(q,BLACKHOLE_sizeW(),stp);
1966 //ToDo: derive size etc from reverted IP
1967 //to = copy(q,size,stp);
1969 debugBelch("@@ evacuate: RBH %p (%s) to %p (%s)",
1970 q, info_type(q), to, info_type(to)));
1975 ASSERT(sizeofW(StgBlockedFetch) >= MIN_NONUPD_SIZE);
1976 to = copy(q,sizeofW(StgBlockedFetch),stp);
1978 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
1979 q, info_type(q), to, info_type(to)));
1986 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1987 to = copy(q,sizeofW(StgFetchMe),stp);
1989 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
1990 q, info_type(q), to, info_type(to)));
1994 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1995 to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
1997 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
1998 q, info_type(q), to, info_type(to)));
2003 return copy(q,sizeofW(StgTRecHeader),stp);
2005 case TVAR_WAIT_QUEUE:
2006 return copy(q,sizeofW(StgTVarWaitQueue),stp);
2009 return copy(q,sizeofW(StgTVar),stp);
2012 return copy(q,sizeofW(StgTRecChunk),stp);
2015 barf("evacuate: strange closure type %d", (int)(info->type));
2021 /* -----------------------------------------------------------------------------
2022 Evaluate a THUNK_SELECTOR if possible.
2024 returns: NULL if we couldn't evaluate this THUNK_SELECTOR, or
2025 a closure pointer if we evaluated it and this is the result. Note
2026 that "evaluating" the THUNK_SELECTOR doesn't necessarily mean
2027 reducing it to HNF, just that we have eliminated the selection.
2028 The result might be another thunk, or even another THUNK_SELECTOR.
2030 If the return value is non-NULL, the original selector thunk has
2031 been BLACKHOLE'd, and should be updated with an indirection or a
2032 forwarding pointer. If the return value is NULL, then the selector
2036 ToDo: the treatment of THUNK_SELECTORS could be improved in the
2037 following way (from a suggestion by Ian Lynagh):
2039 We can have a chain like this:
2043 |-----> sel_0 --> (a,b)
2045 |-----> sel_0 --> ...
2047 and the depth limit means we don't go all the way to the end of the
2048 chain, which results in a space leak. This affects the recursive
2049 call to evacuate() in the THUNK_SELECTOR case in evacuate(): *not*
2050 the recursive call to eval_thunk_selector() in
2051 eval_thunk_selector().
2053 We could eliminate the depth bound in this case, in the following
2056 - traverse the chain once to discover the *value* of the
2057 THUNK_SELECTOR. Mark all THUNK_SELECTORS that we
2058 visit on the way as having been visited already (somehow).
2060 - in a second pass, traverse the chain again updating all
2061 THUNK_SEELCTORS that we find on the way with indirections to
2064 - if we encounter a "marked" THUNK_SELECTOR in a normal
2065 evacuate(), we konw it can't be updated so just evac it.
2067 Program that illustrates the problem:
2070 foo (x:xs) = let (ys, zs) = foo xs
2071 in if x >= 0 then (x:ys, zs) else (ys, x:zs)
2073 main = bar [1..(100000000::Int)]
2074 bar xs = (\(ys, zs) -> print ys >> print zs) (foo xs)
2076 -------------------------------------------------------------------------- */
2078 static inline rtsBool
2079 is_to_space ( StgClosure *p )
2083 bd = Bdescr((StgPtr)p);
2084 if (HEAP_ALLOCED(p) &&
2085 ((bd->flags & BF_EVACUATED)
2086 || ((bd->flags & BF_COMPACTED) &&
2087 is_marked((P_)p,bd)))) {
2095 eval_thunk_selector( nat field, StgSelector * p )
2098 const StgInfoTable *info_ptr;
2099 StgClosure *selectee;
2101 selectee = p->selectee;
2103 // Save the real info pointer (NOTE: not the same as get_itbl()).
2104 info_ptr = p->header.info;
2106 // If the THUNK_SELECTOR is in a generation that we are not
2107 // collecting, then bail out early. We won't be able to save any
2108 // space in any case, and updating with an indirection is trickier
2110 if (Bdescr((StgPtr)p)->gen_no > N) {
2114 // BLACKHOLE the selector thunk, since it is now under evaluation.
2115 // This is important to stop us going into an infinite loop if
2116 // this selector thunk eventually refers to itself.
2117 SET_INFO(p,&stg_BLACKHOLE_info);
2121 // We don't want to end up in to-space, because this causes
2122 // problems when the GC later tries to evacuate the result of
2123 // eval_thunk_selector(). There are various ways this could
2126 // 1. following an IND_STATIC
2128 // 2. when the old generation is compacted, the mark phase updates
2129 // from-space pointers to be to-space pointers, and we can't
2130 // reliably tell which we're following (eg. from an IND_STATIC).
2132 // 3. compacting GC again: if we're looking at a constructor in
2133 // the compacted generation, it might point directly to objects
2134 // in to-space. We must bale out here, otherwise doing the selection
2135 // will result in a to-space pointer being returned.
2137 // (1) is dealt with using a BF_EVACUATED test on the
2138 // selectee. (2) and (3): we can tell if we're looking at an
2139 // object in the compacted generation that might point to
2140 // to-space objects by testing that (a) it is BF_COMPACTED, (b)
2141 // the compacted generation is being collected, and (c) the
2142 // object is marked. Only a marked object may have pointers that
2143 // point to to-space objects, because that happens when
2146 // The to-space test is now embodied in the in_to_space() inline
2147 // function, as it is re-used below.
2149 if (is_to_space(selectee)) {
2153 info = get_itbl(selectee);
2154 switch (info->type) {
2162 case CONSTR_NOCAF_STATIC:
2163 // check that the size is in range
2164 ASSERT(field < (StgWord32)(info->layout.payload.ptrs +
2165 info->layout.payload.nptrs));
2167 // Select the right field from the constructor, and check
2168 // that the result isn't in to-space. It might be in
2169 // to-space if, for example, this constructor contains
2170 // pointers to younger-gen objects (and is on the mut-once
2175 q = selectee->payload[field];
2176 if (is_to_space(q)) {
2186 case IND_OLDGEN_PERM:
2188 selectee = ((StgInd *)selectee)->indirectee;
2192 // We don't follow pointers into to-space; the constructor
2193 // has already been evacuated, so we won't save any space
2194 // leaks by evaluating this selector thunk anyhow.
2197 case THUNK_SELECTOR:
2201 // check that we don't recurse too much, re-using the
2202 // depth bound also used in evacuate().
2203 if (thunk_selector_depth >= MAX_THUNK_SELECTOR_DEPTH) {
2206 thunk_selector_depth++;
2208 val = eval_thunk_selector(info->layout.selector_offset,
2209 (StgSelector *)selectee);
2211 thunk_selector_depth--;
2216 // We evaluated this selector thunk, so update it with
2217 // an indirection. NOTE: we don't use UPD_IND here,
2218 // because we are guaranteed that p is in a generation
2219 // that we are collecting, and we never want to put the
2220 // indirection on a mutable list.
2222 // For the purposes of LDV profiling, we have destroyed
2223 // the original selector thunk.
2224 SET_INFO(p, info_ptr);
2225 LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(selectee);
2227 ((StgInd *)selectee)->indirectee = val;
2228 SET_INFO(selectee,&stg_IND_info);
2230 // For the purposes of LDV profiling, we have created an
2232 LDV_RECORD_CREATE(selectee);
2249 case SE_CAF_BLACKHOLE:
2261 // not evaluated yet
2265 barf("eval_thunk_selector: strange selectee %d",
2270 // We didn't manage to evaluate this thunk; restore the old info pointer
2271 SET_INFO(p, info_ptr);
2275 /* -----------------------------------------------------------------------------
2276 move_TSO is called to update the TSO structure after it has been
2277 moved from one place to another.
2278 -------------------------------------------------------------------------- */
2281 move_TSO (StgTSO *src, StgTSO *dest)
2285 // relocate the stack pointer...
2286 diff = (StgPtr)dest - (StgPtr)src; // In *words*
2287 dest->sp = (StgPtr)dest->sp + diff;
2290 /* Similar to scavenge_large_bitmap(), but we don't write back the
2291 * pointers we get back from evacuate().
2294 scavenge_large_srt_bitmap( StgLargeSRT *large_srt )
2301 bitmap = large_srt->l.bitmap[b];
2302 size = (nat)large_srt->l.size;
2303 p = (StgClosure **)large_srt->srt;
2304 for (i = 0; i < size; ) {
2305 if ((bitmap & 1) != 0) {
2310 if (i % BITS_IN(W_) == 0) {
2312 bitmap = large_srt->l.bitmap[b];
2314 bitmap = bitmap >> 1;
2319 /* evacuate the SRT. If srt_bitmap is zero, then there isn't an
2320 * srt field in the info table. That's ok, because we'll
2321 * never dereference it.
2324 scavenge_srt (StgClosure **srt, nat srt_bitmap)
2329 bitmap = srt_bitmap;
2332 if (bitmap == (StgHalfWord)(-1)) {
2333 scavenge_large_srt_bitmap( (StgLargeSRT *)srt );
2337 while (bitmap != 0) {
2338 if ((bitmap & 1) != 0) {
2339 #ifdef ENABLE_WIN32_DLL_SUPPORT
2340 // Special-case to handle references to closures hiding out in DLLs, since
2341 // double indirections required to get at those. The code generator knows
2342 // which is which when generating the SRT, so it stores the (indirect)
2343 // reference to the DLL closure in the table by first adding one to it.
2344 // We check for this here, and undo the addition before evacuating it.
2346 // If the SRT entry hasn't got bit 0 set, the SRT entry points to a
2347 // closure that's fixed at link-time, and no extra magic is required.
2348 if ( (unsigned long)(*srt) & 0x1 ) {
2349 evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
2358 bitmap = bitmap >> 1;
2364 scavenge_thunk_srt(const StgInfoTable *info)
2366 StgThunkInfoTable *thunk_info;
2368 thunk_info = itbl_to_thunk_itbl(info);
2369 scavenge_srt((StgClosure **)GET_SRT(thunk_info), thunk_info->i.srt_bitmap);
2373 scavenge_fun_srt(const StgInfoTable *info)
2375 StgFunInfoTable *fun_info;
2377 fun_info = itbl_to_fun_itbl(info);
2378 scavenge_srt((StgClosure **)GET_FUN_SRT(fun_info), fun_info->i.srt_bitmap);
2381 /* -----------------------------------------------------------------------------
2383 -------------------------------------------------------------------------- */
2386 scavengeTSO (StgTSO *tso)
2388 if ( tso->why_blocked == BlockedOnMVar
2389 || tso->why_blocked == BlockedOnBlackHole
2390 || tso->why_blocked == BlockedOnException
2392 || tso->why_blocked == BlockedOnGA
2393 || tso->why_blocked == BlockedOnGA_NoSend
2396 tso->block_info.closure = evacuate(tso->block_info.closure);
2398 if ( tso->blocked_exceptions != NULL ) {
2399 tso->blocked_exceptions =
2400 (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
2403 // We don't always chase the link field: TSOs on the blackhole
2404 // queue are not automatically alive, so the link field is a
2405 // "weak" pointer in that case.
2406 if (tso->why_blocked != BlockedOnBlackHole) {
2407 tso->link = (StgTSO *)evacuate((StgClosure *)tso->link);
2410 // scavange current transaction record
2411 tso->trec = (StgTRecHeader *)evacuate((StgClosure *)tso->trec);
2413 // scavenge this thread's stack
2414 scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
2417 /* -----------------------------------------------------------------------------
2418 Blocks of function args occur on the stack (at the top) and
2420 -------------------------------------------------------------------------- */
2422 STATIC_INLINE StgPtr
2423 scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
2430 switch (fun_info->f.fun_type) {
2432 bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
2433 size = BITMAP_SIZE(fun_info->f.b.bitmap);
2436 size = GET_FUN_LARGE_BITMAP(fun_info)->size;
2437 scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
2441 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2442 size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->f.fun_type]);
2445 if ((bitmap & 1) == 0) {
2446 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2449 bitmap = bitmap >> 1;
2457 STATIC_INLINE StgPtr
2458 scavenge_PAP_payload (StgClosure *fun, StgClosure **payload, StgWord size)
2462 StgFunInfoTable *fun_info;
2464 fun_info = get_fun_itbl(fun);
2465 ASSERT(fun_info->i.type != PAP);
2466 p = (StgPtr)payload;
2468 switch (fun_info->f.fun_type) {
2470 bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
2473 scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
2477 scavenge_large_bitmap((StgPtr)payload, BCO_BITMAP(fun), size);
2481 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2484 if ((bitmap & 1) == 0) {
2485 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2488 bitmap = bitmap >> 1;
2496 STATIC_INLINE StgPtr
2497 scavenge_PAP (StgPAP *pap)
2499 pap->fun = evacuate(pap->fun);
2500 return scavenge_PAP_payload (pap->fun, pap->payload, pap->n_args);
2503 STATIC_INLINE StgPtr
2504 scavenge_AP (StgAP *ap)
2506 ap->fun = evacuate(ap->fun);
2507 return scavenge_PAP_payload (ap->fun, ap->payload, ap->n_args);
2510 /* -----------------------------------------------------------------------------
2511 Scavenge a given step until there are no more objects in this step
2514 evac_gen is set by the caller to be either zero (for a step in a
2515 generation < N) or G where G is the generation of the step being
2518 We sometimes temporarily change evac_gen back to zero if we're
2519 scavenging a mutable object where early promotion isn't such a good
2521 -------------------------------------------------------------------------- */
2529 nat saved_evac_gen = evac_gen;
2534 failed_to_evac = rtsFalse;
2536 /* scavenge phase - standard breadth-first scavenging of the
2540 while (bd != stp->hp_bd || p < stp->hp) {
2542 // If we're at the end of this block, move on to the next block
2543 if (bd != stp->hp_bd && p == bd->free) {
2549 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2550 info = get_itbl((StgClosure *)p);
2552 ASSERT(thunk_selector_depth == 0);
2555 switch (info->type) {
2559 StgMVar *mvar = ((StgMVar *)p);
2561 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
2562 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
2563 mvar->value = evacuate((StgClosure *)mvar->value);
2564 evac_gen = saved_evac_gen;
2565 failed_to_evac = rtsTrue; // mutable.
2566 p += sizeofW(StgMVar);
2571 scavenge_fun_srt(info);
2572 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2573 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2574 p += sizeofW(StgHeader) + 2;
2578 scavenge_thunk_srt(info);
2579 ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
2580 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2581 p += sizeofW(StgThunk) + 2;
2585 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2586 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2587 p += sizeofW(StgHeader) + 2;
2591 scavenge_thunk_srt(info);
2592 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2593 p += sizeofW(StgThunk) + 1;
2597 scavenge_fun_srt(info);
2599 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2600 p += sizeofW(StgHeader) + 1;
2604 scavenge_thunk_srt(info);
2605 p += sizeofW(StgThunk) + 1;
2609 scavenge_fun_srt(info);
2611 p += sizeofW(StgHeader) + 1;
2615 scavenge_thunk_srt(info);
2616 p += sizeofW(StgThunk) + 2;
2620 scavenge_fun_srt(info);
2622 p += sizeofW(StgHeader) + 2;
2626 scavenge_thunk_srt(info);
2627 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2628 p += sizeofW(StgThunk) + 2;
2632 scavenge_fun_srt(info);
2634 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2635 p += sizeofW(StgHeader) + 2;
2639 scavenge_fun_srt(info);
2646 scavenge_thunk_srt(info);
2647 end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
2648 for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
2649 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2651 p += info->layout.payload.nptrs;
2663 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2664 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2665 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2667 p += info->layout.payload.nptrs;
2672 StgBCO *bco = (StgBCO *)p;
2673 bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
2674 bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
2675 bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
2676 bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
2677 p += bco_sizeW(bco);
2682 if (stp->gen->no != 0) {
2685 // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an
2686 // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
2687 LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
2690 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
2692 SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
2694 // We pretend that p has just been created.
2695 LDV_RECORD_CREATE((StgClosure *)p);
2698 case IND_OLDGEN_PERM:
2699 ((StgInd *)p)->indirectee = evacuate(((StgInd *)p)->indirectee);
2700 p += sizeofW(StgInd);
2705 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2706 evac_gen = saved_evac_gen;
2707 failed_to_evac = rtsTrue; // mutable anyhow
2708 p += sizeofW(StgMutVar);
2712 case SE_CAF_BLACKHOLE:
2715 p += BLACKHOLE_sizeW();
2718 case THUNK_SELECTOR:
2720 StgSelector *s = (StgSelector *)p;
2721 s->selectee = evacuate(s->selectee);
2722 p += THUNK_SELECTOR_sizeW();
2726 // A chunk of stack saved in a heap object
2729 StgAP_STACK *ap = (StgAP_STACK *)p;
2731 ap->fun = evacuate(ap->fun);
2732 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2733 p = (StgPtr)ap->payload + ap->size;
2738 p = scavenge_PAP((StgPAP *)p);
2742 p = scavenge_AP((StgAP *)p);
2746 // nothing to follow
2747 p += arr_words_sizeW((StgArrWords *)p);
2751 // follow everything
2755 evac_gen = 0; // repeatedly mutable
2756 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2757 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2758 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2760 evac_gen = saved_evac_gen;
2761 failed_to_evac = rtsTrue; // mutable anyhow.
2765 case MUT_ARR_PTRS_FROZEN:
2766 case MUT_ARR_PTRS_FROZEN0:
2767 // follow everything
2771 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2772 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2773 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2775 // it's tempting to recordMutable() if failed_to_evac is
2776 // false, but that breaks some assumptions (eg. every
2777 // closure on the mutable list is supposed to have the MUT
2778 // flag set, and MUT_ARR_PTRS_FROZEN doesn't).
2784 StgTSO *tso = (StgTSO *)p;
2787 evac_gen = saved_evac_gen;
2788 failed_to_evac = rtsTrue; // mutable anyhow.
2789 p += tso_sizeW(tso);
2797 nat size, ptrs, nonptrs, vhs;
2799 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2801 StgRBH *rbh = (StgRBH *)p;
2802 (StgClosure *)rbh->blocking_queue =
2803 evacuate((StgClosure *)rbh->blocking_queue);
2804 failed_to_evac = rtsTrue; // mutable anyhow.
2806 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2807 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2808 // ToDo: use size of reverted closure here!
2809 p += BLACKHOLE_sizeW();
2815 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2816 // follow the pointer to the node which is being demanded
2817 (StgClosure *)bf->node =
2818 evacuate((StgClosure *)bf->node);
2819 // follow the link to the rest of the blocking queue
2820 (StgClosure *)bf->link =
2821 evacuate((StgClosure *)bf->link);
2823 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
2824 bf, info_type((StgClosure *)bf),
2825 bf->node, info_type(bf->node)));
2826 p += sizeofW(StgBlockedFetch);
2834 p += sizeofW(StgFetchMe);
2835 break; // nothing to do in this case
2839 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
2840 (StgClosure *)fmbq->blocking_queue =
2841 evacuate((StgClosure *)fmbq->blocking_queue);
2843 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
2844 p, info_type((StgClosure *)p)));
2845 p += sizeofW(StgFetchMeBlockingQueue);
2850 case TVAR_WAIT_QUEUE:
2852 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
2854 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
2855 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
2856 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
2857 evac_gen = saved_evac_gen;
2858 failed_to_evac = rtsTrue; // mutable
2859 p += sizeofW(StgTVarWaitQueue);
2865 StgTVar *tvar = ((StgTVar *) p);
2867 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
2868 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
2869 evac_gen = saved_evac_gen;
2870 failed_to_evac = rtsTrue; // mutable
2871 p += sizeofW(StgTVar);
2877 StgTRecHeader *trec = ((StgTRecHeader *) p);
2879 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
2880 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
2881 evac_gen = saved_evac_gen;
2882 failed_to_evac = rtsTrue; // mutable
2883 p += sizeofW(StgTRecHeader);
2890 StgTRecChunk *tc = ((StgTRecChunk *) p);
2891 TRecEntry *e = &(tc -> entries[0]);
2893 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
2894 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
2895 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
2896 e->expected_value = evacuate((StgClosure*)e->expected_value);
2897 e->new_value = evacuate((StgClosure*)e->new_value);
2899 evac_gen = saved_evac_gen;
2900 failed_to_evac = rtsTrue; // mutable
2901 p += sizeofW(StgTRecChunk);
2906 barf("scavenge: unimplemented/strange closure type %d @ %p",
2911 * We need to record the current object on the mutable list if
2912 * (a) It is actually mutable, or
2913 * (b) It contains pointers to a younger generation.
2914 * Case (b) arises if we didn't manage to promote everything that
2915 * the current object points to into the current generation.
2917 if (failed_to_evac) {
2918 failed_to_evac = rtsFalse;
2919 recordMutableGen((StgClosure *)q, stp->gen);
2927 /* -----------------------------------------------------------------------------
2928 Scavenge everything on the mark stack.
2930 This is slightly different from scavenge():
2931 - we don't walk linearly through the objects, so the scavenger
2932 doesn't need to advance the pointer on to the next object.
2933 -------------------------------------------------------------------------- */
2936 scavenge_mark_stack(void)
2942 evac_gen = oldest_gen->no;
2943 saved_evac_gen = evac_gen;
2946 while (!mark_stack_empty()) {
2947 p = pop_mark_stack();
2949 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2950 info = get_itbl((StgClosure *)p);
2953 switch (info->type) {
2957 StgMVar *mvar = ((StgMVar *)p);
2959 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
2960 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
2961 mvar->value = evacuate((StgClosure *)mvar->value);
2962 evac_gen = saved_evac_gen;
2963 failed_to_evac = rtsTrue; // mutable.
2968 scavenge_fun_srt(info);
2969 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2970 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2974 scavenge_thunk_srt(info);
2975 ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
2976 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2980 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2981 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2986 scavenge_fun_srt(info);
2987 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2992 scavenge_thunk_srt(info);
2993 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2998 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3003 scavenge_fun_srt(info);
3008 scavenge_thunk_srt(info);
3016 scavenge_fun_srt(info);
3023 scavenge_thunk_srt(info);
3024 end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
3025 for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
3026 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3039 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3040 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
3041 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3047 StgBCO *bco = (StgBCO *)p;
3048 bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
3049 bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
3050 bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
3051 bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
3056 // don't need to do anything here: the only possible case
3057 // is that we're in a 1-space compacting collector, with
3058 // no "old" generation.
3062 case IND_OLDGEN_PERM:
3063 ((StgInd *)p)->indirectee =
3064 evacuate(((StgInd *)p)->indirectee);
3069 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3070 evac_gen = saved_evac_gen;
3071 failed_to_evac = rtsTrue;
3075 case SE_CAF_BLACKHOLE:
3081 case THUNK_SELECTOR:
3083 StgSelector *s = (StgSelector *)p;
3084 s->selectee = evacuate(s->selectee);
3088 // A chunk of stack saved in a heap object
3091 StgAP_STACK *ap = (StgAP_STACK *)p;
3093 ap->fun = evacuate(ap->fun);
3094 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3099 scavenge_PAP((StgPAP *)p);
3103 scavenge_AP((StgAP *)p);
3107 // follow everything
3111 evac_gen = 0; // repeatedly mutable
3112 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3113 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3114 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3116 evac_gen = saved_evac_gen;
3117 failed_to_evac = rtsTrue; // mutable anyhow.
3121 case MUT_ARR_PTRS_FROZEN:
3122 case MUT_ARR_PTRS_FROZEN0:
3123 // follow everything
3127 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3128 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3129 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3136 StgTSO *tso = (StgTSO *)p;
3139 evac_gen = saved_evac_gen;
3140 failed_to_evac = rtsTrue;
3148 nat size, ptrs, nonptrs, vhs;
3150 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3152 StgRBH *rbh = (StgRBH *)p;
3153 bh->blocking_queue =
3154 (StgTSO *)evacuate((StgClosure *)bh->blocking_queue);
3155 failed_to_evac = rtsTrue; // mutable anyhow.
3157 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3158 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3164 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3165 // follow the pointer to the node which is being demanded
3166 (StgClosure *)bf->node =
3167 evacuate((StgClosure *)bf->node);
3168 // follow the link to the rest of the blocking queue
3169 (StgClosure *)bf->link =
3170 evacuate((StgClosure *)bf->link);
3172 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3173 bf, info_type((StgClosure *)bf),
3174 bf->node, info_type(bf->node)));
3182 break; // nothing to do in this case
3186 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3187 (StgClosure *)fmbq->blocking_queue =
3188 evacuate((StgClosure *)fmbq->blocking_queue);
3190 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3191 p, info_type((StgClosure *)p)));
3196 case TVAR_WAIT_QUEUE:
3198 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3200 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3201 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3202 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3203 evac_gen = saved_evac_gen;
3204 failed_to_evac = rtsTrue; // mutable
3210 StgTVar *tvar = ((StgTVar *) p);
3212 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3213 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3214 evac_gen = saved_evac_gen;
3215 failed_to_evac = rtsTrue; // mutable
3222 StgTRecChunk *tc = ((StgTRecChunk *) p);
3223 TRecEntry *e = &(tc -> entries[0]);
3225 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3226 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3227 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3228 e->expected_value = evacuate((StgClosure*)e->expected_value);
3229 e->new_value = evacuate((StgClosure*)e->new_value);
3231 evac_gen = saved_evac_gen;
3232 failed_to_evac = rtsTrue; // mutable
3238 StgTRecHeader *trec = ((StgTRecHeader *) p);
3240 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3241 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3242 evac_gen = saved_evac_gen;
3243 failed_to_evac = rtsTrue; // mutable
3248 barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p",
3252 if (failed_to_evac) {
3253 failed_to_evac = rtsFalse;
3254 recordMutableGen((StgClosure *)q, &generations[evac_gen]);
3257 // mark the next bit to indicate "scavenged"
3258 mark(q+1, Bdescr(q));
3260 } // while (!mark_stack_empty())
3262 // start a new linear scan if the mark stack overflowed at some point
3263 if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
3264 IF_DEBUG(gc, debugBelch("scavenge_mark_stack: starting linear scan"));
3265 mark_stack_overflowed = rtsFalse;
3266 oldgen_scan_bd = oldest_gen->steps[0].blocks;
3267 oldgen_scan = oldgen_scan_bd->start;
3270 if (oldgen_scan_bd) {
3271 // push a new thing on the mark stack
3273 // find a closure that is marked but not scavenged, and start
3275 while (oldgen_scan < oldgen_scan_bd->free
3276 && !is_marked(oldgen_scan,oldgen_scan_bd)) {
3280 if (oldgen_scan < oldgen_scan_bd->free) {
3282 // already scavenged?
3283 if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
3284 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3287 push_mark_stack(oldgen_scan);
3288 // ToDo: bump the linear scan by the actual size of the object
3289 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3293 oldgen_scan_bd = oldgen_scan_bd->link;
3294 if (oldgen_scan_bd != NULL) {
3295 oldgen_scan = oldgen_scan_bd->start;
3301 /* -----------------------------------------------------------------------------
3302 Scavenge one object.
3304 This is used for objects that are temporarily marked as mutable
3305 because they contain old-to-new generation pointers. Only certain
3306 objects can have this property.
3307 -------------------------------------------------------------------------- */
3310 scavenge_one(StgPtr p)
3312 const StgInfoTable *info;
3313 nat saved_evac_gen = evac_gen;
3316 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3317 info = get_itbl((StgClosure *)p);
3319 switch (info->type) {
3323 StgMVar *mvar = ((StgMVar *)p);
3325 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
3326 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
3327 mvar->value = evacuate((StgClosure *)mvar->value);
3328 evac_gen = saved_evac_gen;
3329 failed_to_evac = rtsTrue; // mutable.
3342 end = (StgPtr)((StgThunk *)p)->payload + info->layout.payload.ptrs;
3343 for (q = (StgPtr)((StgThunk *)p)->payload; q < end; q++) {
3344 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3350 case FUN_1_0: // hardly worth specialising these guys
3367 end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3368 for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
3369 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3376 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3377 evac_gen = saved_evac_gen;
3378 failed_to_evac = rtsTrue; // mutable anyhow
3382 case SE_CAF_BLACKHOLE:
3387 case THUNK_SELECTOR:
3389 StgSelector *s = (StgSelector *)p;
3390 s->selectee = evacuate(s->selectee);
3396 StgAP_STACK *ap = (StgAP_STACK *)p;
3398 ap->fun = evacuate(ap->fun);
3399 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3400 p = (StgPtr)ap->payload + ap->size;
3405 p = scavenge_PAP((StgPAP *)p);
3409 p = scavenge_AP((StgAP *)p);
3413 // nothing to follow
3418 // follow everything
3421 evac_gen = 0; // repeatedly mutable
3422 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3423 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3424 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3426 evac_gen = saved_evac_gen;
3427 failed_to_evac = rtsTrue;
3431 case MUT_ARR_PTRS_FROZEN:
3432 case MUT_ARR_PTRS_FROZEN0:
3434 // follow everything
3437 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3438 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3439 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3446 StgTSO *tso = (StgTSO *)p;
3448 evac_gen = 0; // repeatedly mutable
3450 evac_gen = saved_evac_gen;
3451 failed_to_evac = rtsTrue;
3459 nat size, ptrs, nonptrs, vhs;
3461 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3463 StgRBH *rbh = (StgRBH *)p;
3464 (StgClosure *)rbh->blocking_queue =
3465 evacuate((StgClosure *)rbh->blocking_queue);
3466 failed_to_evac = rtsTrue; // mutable anyhow.
3468 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3469 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3470 // ToDo: use size of reverted closure here!
3476 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3477 // follow the pointer to the node which is being demanded
3478 (StgClosure *)bf->node =
3479 evacuate((StgClosure *)bf->node);
3480 // follow the link to the rest of the blocking queue
3481 (StgClosure *)bf->link =
3482 evacuate((StgClosure *)bf->link);
3484 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3485 bf, info_type((StgClosure *)bf),
3486 bf->node, info_type(bf->node)));
3494 break; // nothing to do in this case
3498 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3499 (StgClosure *)fmbq->blocking_queue =
3500 evacuate((StgClosure *)fmbq->blocking_queue);
3502 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3503 p, info_type((StgClosure *)p)));
3508 case TVAR_WAIT_QUEUE:
3510 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3512 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3513 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3514 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3515 evac_gen = saved_evac_gen;
3516 failed_to_evac = rtsTrue; // mutable
3522 StgTVar *tvar = ((StgTVar *) p);
3524 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3525 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3526 evac_gen = saved_evac_gen;
3527 failed_to_evac = rtsTrue; // mutable
3533 StgTRecHeader *trec = ((StgTRecHeader *) p);
3535 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3536 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3537 evac_gen = saved_evac_gen;
3538 failed_to_evac = rtsTrue; // mutable
3545 StgTRecChunk *tc = ((StgTRecChunk *) p);
3546 TRecEntry *e = &(tc -> entries[0]);
3548 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3549 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3550 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3551 e->expected_value = evacuate((StgClosure*)e->expected_value);
3552 e->new_value = evacuate((StgClosure*)e->new_value);
3554 evac_gen = saved_evac_gen;
3555 failed_to_evac = rtsTrue; // mutable
3560 case IND_OLDGEN_PERM:
3563 /* Careful here: a THUNK can be on the mutable list because
3564 * it contains pointers to young gen objects. If such a thunk
3565 * is updated, the IND_OLDGEN will be added to the mutable
3566 * list again, and we'll scavenge it twice. evacuate()
3567 * doesn't check whether the object has already been
3568 * evacuated, so we perform that check here.
3570 StgClosure *q = ((StgInd *)p)->indirectee;
3571 if (HEAP_ALLOCED(q) && Bdescr((StgPtr)q)->flags & BF_EVACUATED) {
3574 ((StgInd *)p)->indirectee = evacuate(q);
3577 #if 0 && defined(DEBUG)
3578 if (RtsFlags.DebugFlags.gc)
3579 /* Debugging code to print out the size of the thing we just
3583 StgPtr start = gen->steps[0].scan;
3584 bdescr *start_bd = gen->steps[0].scan_bd;
3586 scavenge(&gen->steps[0]);
3587 if (start_bd != gen->steps[0].scan_bd) {
3588 size += (P_)BLOCK_ROUND_UP(start) - start;
3589 start_bd = start_bd->link;
3590 while (start_bd != gen->steps[0].scan_bd) {
3591 size += BLOCK_SIZE_W;
3592 start_bd = start_bd->link;
3594 size += gen->steps[0].scan -
3595 (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
3597 size = gen->steps[0].scan - start;
3599 debugBelch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
3605 barf("scavenge_one: strange object %d", (int)(info->type));
3608 no_luck = failed_to_evac;
3609 failed_to_evac = rtsFalse;
3613 /* -----------------------------------------------------------------------------
3614 Scavenging mutable lists.
3616 We treat the mutable list of each generation > N (i.e. all the
3617 generations older than the one being collected) as roots. We also
3618 remove non-mutable objects from the mutable list at this point.
3619 -------------------------------------------------------------------------- */
3622 scavenge_mutable_list(generation *gen)
3627 bd = gen->saved_mut_list;
3630 for (; bd != NULL; bd = bd->link) {
3631 for (q = bd->start; q < bd->free; q++) {
3633 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3634 if (scavenge_one(p)) {
3635 /* didn't manage to promote everything, so put the
3636 * object back on the list.
3638 recordMutableGen((StgClosure *)p,gen);
3643 // free the old mut_list
3644 freeChain(gen->saved_mut_list);
3645 gen->saved_mut_list = NULL;
3650 scavenge_static(void)
3652 StgClosure* p = static_objects;
3653 const StgInfoTable *info;
3655 /* Always evacuate straight to the oldest generation for static
3657 evac_gen = oldest_gen->no;
3659 /* keep going until we've scavenged all the objects on the linked
3661 while (p != END_OF_STATIC_LIST) {
3663 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3666 if (info->type==RBH)
3667 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3669 // make sure the info pointer is into text space
3671 /* Take this object *off* the static_objects list,
3672 * and put it on the scavenged_static_objects list.
3674 static_objects = *STATIC_LINK(info,p);
3675 *STATIC_LINK(info,p) = scavenged_static_objects;
3676 scavenged_static_objects = p;
3678 switch (info -> type) {
3682 StgInd *ind = (StgInd *)p;
3683 ind->indirectee = evacuate(ind->indirectee);
3685 /* might fail to evacuate it, in which case we have to pop it
3686 * back on the mutable list of the oldest generation. We
3687 * leave it *on* the scavenged_static_objects list, though,
3688 * in case we visit this object again.
3690 if (failed_to_evac) {
3691 failed_to_evac = rtsFalse;
3692 recordMutableGen((StgClosure *)p,oldest_gen);
3698 scavenge_thunk_srt(info);
3702 scavenge_fun_srt(info);
3709 next = (P_)p->payload + info->layout.payload.ptrs;
3710 // evacuate the pointers
3711 for (q = (P_)p->payload; q < next; q++) {
3712 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3718 barf("scavenge_static: strange closure %d", (int)(info->type));
3721 ASSERT(failed_to_evac == rtsFalse);
3723 /* get the next static object from the list. Remember, there might
3724 * be more stuff on this list now that we've done some evacuating!
3725 * (static_objects is a global)
3731 /* -----------------------------------------------------------------------------
3732 scavenge a chunk of memory described by a bitmap
3733 -------------------------------------------------------------------------- */
3736 scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
3742 bitmap = large_bitmap->bitmap[b];
3743 for (i = 0; i < size; ) {
3744 if ((bitmap & 1) == 0) {
3745 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3749 if (i % BITS_IN(W_) == 0) {
3751 bitmap = large_bitmap->bitmap[b];
3753 bitmap = bitmap >> 1;
3758 STATIC_INLINE StgPtr
3759 scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap)
3762 if ((bitmap & 1) == 0) {
3763 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3766 bitmap = bitmap >> 1;
3772 /* -----------------------------------------------------------------------------
3773 scavenge_stack walks over a section of stack and evacuates all the
3774 objects pointed to by it. We can use the same code for walking
3775 AP_STACK_UPDs, since these are just sections of copied stack.
3776 -------------------------------------------------------------------------- */
3780 scavenge_stack(StgPtr p, StgPtr stack_end)
3782 const StgRetInfoTable* info;
3786 //IF_DEBUG(sanity, debugBelch(" scavenging stack between %p and %p", p, stack_end));
3789 * Each time around this loop, we are looking at a chunk of stack
3790 * that starts with an activation record.
3793 while (p < stack_end) {
3794 info = get_ret_itbl((StgClosure *)p);
3796 switch (info->i.type) {
3799 ((StgUpdateFrame *)p)->updatee
3800 = evacuate(((StgUpdateFrame *)p)->updatee);
3801 p += sizeofW(StgUpdateFrame);
3804 // small bitmap (< 32 entries, or 64 on a 64-bit machine)
3805 case CATCH_STM_FRAME:
3806 case CATCH_RETRY_FRAME:
3807 case ATOMICALLY_FRAME:
3812 bitmap = BITMAP_BITS(info->i.layout.bitmap);
3813 size = BITMAP_SIZE(info->i.layout.bitmap);
3814 // NOTE: the payload starts immediately after the info-ptr, we
3815 // don't have an StgHeader in the same sense as a heap closure.
3817 p = scavenge_small_bitmap(p, size, bitmap);
3820 scavenge_srt((StgClosure **)GET_SRT(info), info->i.srt_bitmap);
3828 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3831 size = BCO_BITMAP_SIZE(bco);
3832 scavenge_large_bitmap(p, BCO_BITMAP(bco), size);
3837 // large bitmap (> 32 entries, or > 64 on a 64-bit machine)
3843 size = GET_LARGE_BITMAP(&info->i)->size;
3845 scavenge_large_bitmap(p, GET_LARGE_BITMAP(&info->i), size);
3847 // and don't forget to follow the SRT
3851 // Dynamic bitmap: the mask is stored on the stack, and
3852 // there are a number of non-pointers followed by a number
3853 // of pointers above the bitmapped area. (see StgMacros.h,
3858 dyn = ((StgRetDyn *)p)->liveness;
3860 // traverse the bitmap first
3861 bitmap = RET_DYN_LIVENESS(dyn);
3862 p = (P_)&((StgRetDyn *)p)->payload[0];
3863 size = RET_DYN_BITMAP_SIZE;
3864 p = scavenge_small_bitmap(p, size, bitmap);
3866 // skip over the non-ptr words
3867 p += RET_DYN_NONPTRS(dyn) + RET_DYN_NONPTR_REGS_SIZE;
3869 // follow the ptr words
3870 for (size = RET_DYN_PTRS(dyn); size > 0; size--) {
3871 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3879 StgRetFun *ret_fun = (StgRetFun *)p;
3880 StgFunInfoTable *fun_info;
3882 ret_fun->fun = evacuate(ret_fun->fun);
3883 fun_info = get_fun_itbl(ret_fun->fun);
3884 p = scavenge_arg_block(fun_info, ret_fun->payload);
3889 barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->i.type));
3894 /*-----------------------------------------------------------------------------
3895 scavenge the large object list.
3897 evac_gen set by caller; similar games played with evac_gen as with
3898 scavenge() - see comment at the top of scavenge(). Most large
3899 objects are (repeatedly) mutable, so most of the time evac_gen will
3901 --------------------------------------------------------------------------- */
3904 scavenge_large(step *stp)
3909 bd = stp->new_large_objects;
3911 for (; bd != NULL; bd = stp->new_large_objects) {
3913 /* take this object *off* the large objects list and put it on
3914 * the scavenged large objects list. This is so that we can
3915 * treat new_large_objects as a stack and push new objects on
3916 * the front when evacuating.
3918 stp->new_large_objects = bd->link;
3919 dbl_link_onto(bd, &stp->scavenged_large_objects);
3921 // update the block count in this step.
3922 stp->n_scavenged_large_blocks += bd->blocks;
3925 if (scavenge_one(p)) {
3926 recordMutableGen((StgClosure *)p, stp->gen);
3931 /* -----------------------------------------------------------------------------
3932 Initialising the static object & mutable lists
3933 -------------------------------------------------------------------------- */
3936 zero_static_object_list(StgClosure* first_static)
3940 const StgInfoTable *info;
3942 for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
3944 link = *STATIC_LINK(info, p);
3945 *STATIC_LINK(info,p) = NULL;
3949 /* -----------------------------------------------------------------------------
3951 -------------------------------------------------------------------------- */
3958 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
3959 c = (StgIndStatic *)c->static_link)
3961 SET_INFO(c, c->saved_info);
3962 c->saved_info = NULL;
3963 // could, but not necessary: c->static_link = NULL;
3965 revertible_caf_list = NULL;
3969 markCAFs( evac_fn evac )
3973 for (c = (StgIndStatic *)caf_list; c != NULL;
3974 c = (StgIndStatic *)c->static_link)
3976 evac(&c->indirectee);
3978 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
3979 c = (StgIndStatic *)c->static_link)
3981 evac(&c->indirectee);
3985 /* -----------------------------------------------------------------------------
3986 Sanity code for CAF garbage collection.
3988 With DEBUG turned on, we manage a CAF list in addition to the SRT
3989 mechanism. After GC, we run down the CAF list and blackhole any
3990 CAFs which have been garbage collected. This means we get an error
3991 whenever the program tries to enter a garbage collected CAF.
3993 Any garbage collected CAFs are taken off the CAF list at the same
3995 -------------------------------------------------------------------------- */
3997 #if 0 && defined(DEBUG)
4004 const StgInfoTable *info;
4015 ASSERT(info->type == IND_STATIC);
4017 if (STATIC_LINK(info,p) == NULL) {
4018 IF_DEBUG(gccafs, debugBelch("CAF gc'd at 0x%04lx", (long)p));
4020 SET_INFO(p,&stg_BLACKHOLE_info);
4021 p = STATIC_LINK2(info,p);
4025 pp = &STATIC_LINK2(info,p);
4032 // debugBelch("%d CAFs live", i);
4037 /* -----------------------------------------------------------------------------
4040 Whenever a thread returns to the scheduler after possibly doing
4041 some work, we have to run down the stack and black-hole all the
4042 closures referred to by update frames.
4043 -------------------------------------------------------------------------- */
4046 threadLazyBlackHole(StgTSO *tso)
4049 StgRetInfoTable *info;
4053 stack_end = &tso->stack[tso->stack_size];
4055 frame = (StgClosure *)tso->sp;
4058 info = get_ret_itbl(frame);
4060 switch (info->i.type) {
4063 bh = ((StgUpdateFrame *)frame)->updatee;
4065 /* if the thunk is already blackholed, it means we've also
4066 * already blackholed the rest of the thunks on this stack,
4067 * so we can stop early.
4069 * The blackhole made for a CAF is a CAF_BLACKHOLE, so they
4070 * don't interfere with this optimisation.
4072 if (bh->header.info == &stg_BLACKHOLE_info) {
4076 if (bh->header.info != &stg_CAF_BLACKHOLE_info) {
4077 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4078 debugBelch("Unexpected lazy BHing required at 0x%04x\n",(int)bh);
4082 // We pretend that bh is now dead.
4083 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4085 SET_INFO(bh,&stg_BLACKHOLE_info);
4087 // We pretend that bh has just been created.
4088 LDV_RECORD_CREATE(bh);
4091 frame = (StgClosure *) ((StgUpdateFrame *)frame + 1);
4097 // normal stack frames; do nothing except advance the pointer
4099 frame = (StgClosure *)((StgPtr)frame + stack_frame_sizeW(frame));
4105 /* -----------------------------------------------------------------------------
4108 * Code largely pinched from old RTS, then hacked to bits. We also do
4109 * lazy black holing here.
4111 * -------------------------------------------------------------------------- */
4113 struct stack_gap { StgWord gap_size; struct stack_gap *next_gap; };
4116 threadSqueezeStack(StgTSO *tso)
4119 rtsBool prev_was_update_frame;
4120 StgClosure *updatee = NULL;
4122 StgRetInfoTable *info;
4123 StgWord current_gap_size;
4124 struct stack_gap *gap;
4127 // Traverse the stack upwards, replacing adjacent update frames
4128 // with a single update frame and a "stack gap". A stack gap
4129 // contains two values: the size of the gap, and the distance
4130 // to the next gap (or the stack top).
4132 bottom = &(tso->stack[tso->stack_size]);
4136 ASSERT(frame < bottom);
4138 prev_was_update_frame = rtsFalse;
4139 current_gap_size = 0;
4140 gap = (struct stack_gap *) (tso->sp - sizeofW(StgUpdateFrame));
4142 while (frame < bottom) {
4144 info = get_ret_itbl((StgClosure *)frame);
4145 switch (info->i.type) {
4149 StgUpdateFrame *upd = (StgUpdateFrame *)frame;
4151 if (upd->updatee->header.info == &stg_BLACKHOLE_info) {
4153 // found a BLACKHOLE'd update frame; we've been here
4154 // before, in a previous GC, so just break out.
4156 // Mark the end of the gap, if we're in one.
4157 if (current_gap_size != 0) {
4158 gap = (struct stack_gap *)(frame-sizeofW(StgUpdateFrame));
4161 frame += sizeofW(StgUpdateFrame);
4162 goto done_traversing;
4165 if (prev_was_update_frame) {
4167 TICK_UPD_SQUEEZED();
4168 /* wasn't there something about update squeezing and ticky to be
4169 * sorted out? oh yes: we aren't counting each enter properly
4170 * in this case. See the log somewhere. KSW 1999-04-21
4172 * Check two things: that the two update frames don't point to
4173 * the same object, and that the updatee_bypass isn't already an
4174 * indirection. Both of these cases only happen when we're in a
4175 * block hole-style loop (and there are multiple update frames
4176 * on the stack pointing to the same closure), but they can both
4177 * screw us up if we don't check.
4179 if (upd->updatee != updatee && !closure_IND(upd->updatee)) {
4180 UPD_IND_NOLOCK(upd->updatee, updatee);
4183 // now mark this update frame as a stack gap. The gap
4184 // marker resides in the bottom-most update frame of
4185 // the series of adjacent frames, and covers all the
4186 // frames in this series.
4187 current_gap_size += sizeofW(StgUpdateFrame);
4188 ((struct stack_gap *)frame)->gap_size = current_gap_size;
4189 ((struct stack_gap *)frame)->next_gap = gap;
4191 frame += sizeofW(StgUpdateFrame);
4195 // single update frame, or the topmost update frame in a series
4197 StgClosure *bh = upd->updatee;
4199 // Do lazy black-holing
4200 if (bh->header.info != &stg_BLACKHOLE_info &&
4201 bh->header.info != &stg_CAF_BLACKHOLE_info) {
4202 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4203 debugBelch("Unexpected lazy BHing required at 0x%04x",(int)bh);
4206 /* zero out the slop so that the sanity checker can tell
4207 * where the next closure is.
4210 StgInfoTable *bh_info = get_itbl(bh);
4211 nat np = bh_info->layout.payload.ptrs,
4212 nw = bh_info->layout.payload.nptrs, i;
4213 /* don't zero out slop for a THUNK_SELECTOR,
4214 * because its layout info is used for a
4215 * different purpose, and it's exactly the
4216 * same size as a BLACKHOLE in any case.
4218 if (bh_info->type != THUNK_SELECTOR) {
4219 for (i = 0; i < np + nw; i++) {
4220 ((StgClosure *)bh)->payload[i] = INVALID_OBJECT;
4226 // We pretend that bh is now dead.
4227 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4229 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
4230 SET_INFO(bh,&stg_BLACKHOLE_info);
4232 // We pretend that bh has just been created.
4233 LDV_RECORD_CREATE(bh);
4236 prev_was_update_frame = rtsTrue;
4237 updatee = upd->updatee;
4238 frame += sizeofW(StgUpdateFrame);
4244 prev_was_update_frame = rtsFalse;
4246 // we're not in a gap... check whether this is the end of a gap
4247 // (an update frame can't be the end of a gap).
4248 if (current_gap_size != 0) {
4249 gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
4251 current_gap_size = 0;
4253 frame += stack_frame_sizeW((StgClosure *)frame);
4260 // Now we have a stack with gaps in it, and we have to walk down
4261 // shoving the stack up to fill in the gaps. A diagram might
4265 // | ********* | <- sp
4269 // | stack_gap | <- gap | chunk_size
4271 // | ......... | <- gap_end v
4277 // 'sp' points the the current top-of-stack
4278 // 'gap' points to the stack_gap structure inside the gap
4279 // ***** indicates real stack data
4280 // ..... indicates gap
4281 // <empty> indicates unused
4285 void *gap_start, *next_gap_start, *gap_end;
4288 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4289 sp = next_gap_start;
4291 while ((StgPtr)gap > tso->sp) {
4293 // we're working in *bytes* now...
4294 gap_start = next_gap_start;
4295 gap_end = (void*) ((unsigned char*)gap_start - gap->gap_size * sizeof(W_));
4297 gap = gap->next_gap;
4298 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4300 chunk_size = (unsigned char*)gap_end - (unsigned char*)next_gap_start;
4302 memmove(sp, next_gap_start, chunk_size);
4305 tso->sp = (StgPtr)sp;
4309 /* -----------------------------------------------------------------------------
4312 * We have to prepare for GC - this means doing lazy black holing
4313 * here. We also take the opportunity to do stack squeezing if it's
4315 * -------------------------------------------------------------------------- */
4317 threadPaused(StgTSO *tso)
4319 if ( RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue )
4320 threadSqueezeStack(tso); // does black holing too
4322 threadLazyBlackHole(tso);
4325 /* -----------------------------------------------------------------------------
4327 * -------------------------------------------------------------------------- */
4331 printMutableList(generation *gen)
4336 debugBelch("@@ Mutable list %p: ", gen->mut_list);
4338 for (bd = gen->mut_list; bd != NULL; bd = bd->link) {
4339 for (p = bd->start; p < bd->free; p++) {
4340 debugBelch("%p (%s), ", (void *)*p, info_type((StgClosure *)*p));