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 resizeNurseries(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;
1270 // not alive (yet): leave this thread on the
1271 // old_all_threads list.
1272 prev = &(t->global_link);
1273 next = t->global_link;
1276 // alive: move this thread onto the all_threads list.
1277 next = t->global_link;
1278 t->global_link = all_threads;
1285 /* And resurrect any threads which were about to become garbage.
1288 StgTSO *t, *tmp, *next;
1289 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1290 next = t->global_link;
1291 tmp = (StgTSO *)evacuate((StgClosure *)t);
1292 tmp->global_link = resurrected_threads;
1293 resurrected_threads = tmp;
1297 weak_stage = WeakDone; // *now* we're done,
1298 return rtsTrue; // but one more round of scavenging, please
1301 barf("traverse_weak_ptr_list");
1307 /* -----------------------------------------------------------------------------
1308 After GC, the live weak pointer list may have forwarding pointers
1309 on it, because a weak pointer object was evacuated after being
1310 moved to the live weak pointer list. We remove those forwarding
1313 Also, we don't consider weak pointer objects to be reachable, but
1314 we must nevertheless consider them to be "live" and retain them.
1315 Therefore any weak pointer objects which haven't as yet been
1316 evacuated need to be evacuated now.
1317 -------------------------------------------------------------------------- */
1321 mark_weak_ptr_list ( StgWeak **list )
1323 StgWeak *w, **last_w;
1326 for (w = *list; w; w = w->link) {
1327 // w might be WEAK, EVACUATED, or DEAD_WEAK (actually CON_STATIC) here
1328 ASSERT(w->header.info == &stg_DEAD_WEAK_info
1329 || get_itbl(w)->type == WEAK || get_itbl(w)->type == EVACUATED);
1330 w = (StgWeak *)evacuate((StgClosure *)w);
1332 last_w = &(w->link);
1336 /* -----------------------------------------------------------------------------
1337 isAlive determines whether the given closure is still alive (after
1338 a garbage collection) or not. It returns the new address of the
1339 closure if it is alive, or NULL otherwise.
1341 NOTE: Use it before compaction only!
1342 -------------------------------------------------------------------------- */
1346 isAlive(StgClosure *p)
1348 const StgInfoTable *info;
1353 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
1356 // ignore static closures
1358 // ToDo: for static closures, check the static link field.
1359 // Problem here is that we sometimes don't set the link field, eg.
1360 // for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
1362 if (!HEAP_ALLOCED(p)) {
1366 // ignore closures in generations that we're not collecting.
1368 if (bd->gen_no > N) {
1372 // if it's a pointer into to-space, then we're done
1373 if (bd->flags & BF_EVACUATED) {
1377 // large objects use the evacuated flag
1378 if (bd->flags & BF_LARGE) {
1382 // check the mark bit for compacted steps
1383 if ((bd->flags & BF_COMPACTED) && is_marked((P_)p,bd)) {
1387 switch (info->type) {
1392 case IND_OLDGEN: // rely on compatible layout with StgInd
1393 case IND_OLDGEN_PERM:
1394 // follow indirections
1395 p = ((StgInd *)p)->indirectee;
1400 return ((StgEvacuated *)p)->evacuee;
1403 if (((StgTSO *)p)->what_next == ThreadRelocated) {
1404 p = (StgClosure *)((StgTSO *)p)->link;
1417 mark_root(StgClosure **root)
1419 *root = evacuate(*root);
1423 upd_evacuee(StgClosure *p, StgClosure *dest)
1425 // not true: (ToDo: perhaps it should be)
1426 // ASSERT(Bdescr((P_)dest)->flags & BF_EVACUATED);
1427 SET_INFO(p, &stg_EVACUATED_info);
1428 ((StgEvacuated *)p)->evacuee = dest;
1432 STATIC_INLINE StgClosure *
1433 copy(StgClosure *src, nat size, step *stp)
1438 nat size_org = size;
1441 TICK_GC_WORDS_COPIED(size);
1442 /* Find out where we're going, using the handy "to" pointer in
1443 * the step of the source object. If it turns out we need to
1444 * evacuate to an older generation, adjust it here (see comment
1447 if (stp->gen_no < evac_gen) {
1448 #ifdef NO_EAGER_PROMOTION
1449 failed_to_evac = rtsTrue;
1451 stp = &generations[evac_gen].steps[0];
1455 /* chain a new block onto the to-space for the destination step if
1458 if (stp->hp + size >= stp->hpLim) {
1459 gc_alloc_block(stp);
1462 for(to = stp->hp, from = (P_)src; size>0; --size) {
1468 upd_evacuee(src,(StgClosure *)dest);
1470 // We store the size of the just evacuated object in the LDV word so that
1471 // the profiler can guess the position of the next object later.
1472 SET_EVACUAEE_FOR_LDV(src, size_org);
1474 return (StgClosure *)dest;
1477 /* Special version of copy() for when we only want to copy the info
1478 * pointer of an object, but reserve some padding after it. This is
1479 * used to optimise evacuation of BLACKHOLEs.
1484 copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *stp)
1489 nat size_to_copy_org = size_to_copy;
1492 TICK_GC_WORDS_COPIED(size_to_copy);
1493 if (stp->gen_no < evac_gen) {
1494 #ifdef NO_EAGER_PROMOTION
1495 failed_to_evac = rtsTrue;
1497 stp = &generations[evac_gen].steps[0];
1501 if (stp->hp + size_to_reserve >= stp->hpLim) {
1502 gc_alloc_block(stp);
1505 for(to = stp->hp, from = (P_)src; size_to_copy>0; --size_to_copy) {
1510 stp->hp += size_to_reserve;
1511 upd_evacuee(src,(StgClosure *)dest);
1513 // We store the size of the just evacuated object in the LDV word so that
1514 // the profiler can guess the position of the next object later.
1515 // size_to_copy_org is wrong because the closure already occupies size_to_reserve
1517 SET_EVACUAEE_FOR_LDV(src, size_to_reserve);
1519 if (size_to_reserve - size_to_copy_org > 0)
1520 FILL_SLOP(stp->hp - 1, (int)(size_to_reserve - size_to_copy_org));
1522 return (StgClosure *)dest;
1526 /* -----------------------------------------------------------------------------
1527 Evacuate a large object
1529 This just consists of removing the object from the (doubly-linked)
1530 step->large_objects list, and linking it on to the (singly-linked)
1531 step->new_large_objects list, from where it will be scavenged later.
1533 Convention: bd->flags has BF_EVACUATED set for a large object
1534 that has been evacuated, or unset otherwise.
1535 -------------------------------------------------------------------------- */
1539 evacuate_large(StgPtr p)
1541 bdescr *bd = Bdescr(p);
1544 // object must be at the beginning of the block (or be a ByteArray)
1545 ASSERT(get_itbl((StgClosure *)p)->type == ARR_WORDS ||
1546 (((W_)p & BLOCK_MASK) == 0));
1548 // already evacuated?
1549 if (bd->flags & BF_EVACUATED) {
1550 /* Don't forget to set the failed_to_evac flag if we didn't get
1551 * the desired destination (see comments in evacuate()).
1553 if (bd->gen_no < evac_gen) {
1554 failed_to_evac = rtsTrue;
1555 TICK_GC_FAILED_PROMOTION();
1561 // remove from large_object list
1563 bd->u.back->link = bd->link;
1564 } else { // first object in the list
1565 stp->large_objects = bd->link;
1568 bd->link->u.back = bd->u.back;
1571 /* link it on to the evacuated large object list of the destination step
1574 if (stp->gen_no < evac_gen) {
1575 #ifdef NO_EAGER_PROMOTION
1576 failed_to_evac = rtsTrue;
1578 stp = &generations[evac_gen].steps[0];
1583 bd->gen_no = stp->gen_no;
1584 bd->link = stp->new_large_objects;
1585 stp->new_large_objects = bd;
1586 bd->flags |= BF_EVACUATED;
1589 /* -----------------------------------------------------------------------------
1592 This is called (eventually) for every live object in the system.
1594 The caller to evacuate specifies a desired generation in the
1595 evac_gen global variable. The following conditions apply to
1596 evacuating an object which resides in generation M when we're
1597 collecting up to generation N
1601 else evac to step->to
1603 if M < evac_gen evac to evac_gen, step 0
1605 if the object is already evacuated, then we check which generation
1608 if M >= evac_gen do nothing
1609 if M < evac_gen set failed_to_evac flag to indicate that we
1610 didn't manage to evacuate this object into evac_gen.
1615 evacuate() is the single most important function performance-wise
1616 in the GC. Various things have been tried to speed it up, but as
1617 far as I can tell the code generated by gcc 3.2 with -O2 is about
1618 as good as it's going to get. We pass the argument to evacuate()
1619 in a register using the 'regparm' attribute (see the prototype for
1620 evacuate() near the top of this file).
1622 Changing evacuate() to take an (StgClosure **) rather than
1623 returning the new pointer seems attractive, because we can avoid
1624 writing back the pointer when it hasn't changed (eg. for a static
1625 object, or an object in a generation > N). However, I tried it and
1626 it doesn't help. One reason is that the (StgClosure **) pointer
1627 gets spilled to the stack inside evacuate(), resulting in far more
1628 extra reads/writes than we save.
1629 -------------------------------------------------------------------------- */
1631 REGPARM1 static StgClosure *
1632 evacuate(StgClosure *q)
1639 const StgInfoTable *info;
1642 if (HEAP_ALLOCED(q)) {
1645 if (bd->gen_no > N) {
1646 /* Can't evacuate this object, because it's in a generation
1647 * older than the ones we're collecting. Let's hope that it's
1648 * in evac_gen or older, or we will have to arrange to track
1649 * this pointer using the mutable list.
1651 if (bd->gen_no < evac_gen) {
1653 failed_to_evac = rtsTrue;
1654 TICK_GC_FAILED_PROMOTION();
1659 /* evacuate large objects by re-linking them onto a different list.
1661 if (bd->flags & BF_LARGE) {
1663 if (info->type == TSO &&
1664 ((StgTSO *)q)->what_next == ThreadRelocated) {
1665 q = (StgClosure *)((StgTSO *)q)->link;
1668 evacuate_large((P_)q);
1672 /* If the object is in a step that we're compacting, then we
1673 * need to use an alternative evacuate procedure.
1675 if (bd->flags & BF_COMPACTED) {
1676 if (!is_marked((P_)q,bd)) {
1678 if (mark_stack_full()) {
1679 mark_stack_overflowed = rtsTrue;
1682 push_mark_stack((P_)q);
1687 /* Object is not already evacuated. */
1688 ASSERT((bd->flags & BF_EVACUATED) == 0);
1693 else stp = NULL; // make sure copy() will crash if HEAP_ALLOCED is wrong
1696 // make sure the info pointer is into text space
1697 ASSERT(LOOKS_LIKE_CLOSURE_PTR(q));
1700 switch (info -> type) {
1704 return copy(q,sizeW_fromITBL(info),stp);
1708 StgWord w = (StgWord)q->payload[0];
1709 if (q->header.info == Czh_con_info &&
1710 // unsigned, so always true: (StgChar)w >= MIN_CHARLIKE &&
1711 (StgChar)w <= MAX_CHARLIKE) {
1712 return (StgClosure *)CHARLIKE_CLOSURE((StgChar)w);
1714 if (q->header.info == Izh_con_info &&
1715 (StgInt)w >= MIN_INTLIKE && (StgInt)w <= MAX_INTLIKE) {
1716 return (StgClosure *)INTLIKE_CLOSURE((StgInt)w);
1718 // else, fall through ...
1726 return copy(q,sizeofW(StgHeader)+1,stp);
1731 #ifdef NO_PROMOTE_THUNKS
1732 if (bd->gen_no == 0 &&
1733 bd->step->no != 0 &&
1734 bd->step->no == generations[bd->gen_no].n_steps-1) {
1738 return copy(q,sizeofW(StgHeader)+2,stp);
1746 return copy(q,sizeofW(StgHeader)+2,stp);
1752 case IND_OLDGEN_PERM:
1756 return copy(q,sizeW_fromITBL(info),stp);
1759 return copy(q,bco_sizeW((StgBCO *)q),stp);
1762 case SE_CAF_BLACKHOLE:
1765 return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
1767 case THUNK_SELECTOR:
1771 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
1772 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1775 p = eval_thunk_selector(info->layout.selector_offset,
1779 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1781 // q is still BLACKHOLE'd.
1782 thunk_selector_depth++;
1784 thunk_selector_depth--;
1787 // We store the size of the just evacuated object in the
1788 // LDV word so that the profiler can guess the position of
1789 // the next object later.
1790 SET_EVACUAEE_FOR_LDV(q, THUNK_SELECTOR_sizeW());
1798 // follow chains of indirections, don't evacuate them
1799 q = ((StgInd*)q)->indirectee;
1803 if (info->srt_bitmap != 0 && major_gc &&
1804 THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
1805 THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
1806 static_objects = (StgClosure *)q;
1811 if (info->srt_bitmap != 0 && major_gc &&
1812 FUN_STATIC_LINK((StgClosure *)q) == NULL) {
1813 FUN_STATIC_LINK((StgClosure *)q) = static_objects;
1814 static_objects = (StgClosure *)q;
1819 /* If q->saved_info != NULL, then it's a revertible CAF - it'll be
1820 * on the CAF list, so don't do anything with it here (we'll
1821 * scavenge it later).
1824 && ((StgIndStatic *)q)->saved_info == NULL
1825 && IND_STATIC_LINK((StgClosure *)q) == NULL) {
1826 IND_STATIC_LINK((StgClosure *)q) = static_objects;
1827 static_objects = (StgClosure *)q;
1832 if (major_gc && STATIC_LINK(info,(StgClosure *)q) == NULL) {
1833 STATIC_LINK(info,(StgClosure *)q) = static_objects;
1834 static_objects = (StgClosure *)q;
1838 case CONSTR_INTLIKE:
1839 case CONSTR_CHARLIKE:
1840 case CONSTR_NOCAF_STATIC:
1841 /* no need to put these on the static linked list, they don't need
1855 case CATCH_STM_FRAME:
1856 case CATCH_RETRY_FRAME:
1857 case ATOMICALLY_FRAME:
1858 // shouldn't see these
1859 barf("evacuate: stack frame at %p\n", q);
1863 return copy(q,pap_sizeW((StgPAP*)q),stp);
1866 return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp);
1869 /* Already evacuated, just return the forwarding address.
1870 * HOWEVER: if the requested destination generation (evac_gen) is
1871 * older than the actual generation (because the object was
1872 * already evacuated to a younger generation) then we have to
1873 * set the failed_to_evac flag to indicate that we couldn't
1874 * manage to promote the object to the desired generation.
1876 if (evac_gen > 0) { // optimisation
1877 StgClosure *p = ((StgEvacuated*)q)->evacuee;
1878 if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < evac_gen) {
1879 failed_to_evac = rtsTrue;
1880 TICK_GC_FAILED_PROMOTION();
1883 return ((StgEvacuated*)q)->evacuee;
1886 // just copy the block
1887 return copy(q,arr_words_sizeW((StgArrWords *)q),stp);
1890 case MUT_ARR_PTRS_FROZEN:
1891 case MUT_ARR_PTRS_FROZEN0:
1892 // just copy the block
1893 return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
1897 StgTSO *tso = (StgTSO *)q;
1899 /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
1901 if (tso->what_next == ThreadRelocated) {
1902 q = (StgClosure *)tso->link;
1906 /* To evacuate a small TSO, we need to relocate the update frame
1913 new_tso = (StgTSO *)copyPart((StgClosure *)tso,
1915 sizeofW(StgTSO), stp);
1916 move_TSO(tso, new_tso);
1917 for (p = tso->sp, q = new_tso->sp;
1918 p < tso->stack+tso->stack_size;) {
1922 return (StgClosure *)new_tso;
1929 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
1930 to = copy(q,BLACKHOLE_sizeW(),stp);
1931 //ToDo: derive size etc from reverted IP
1932 //to = copy(q,size,stp);
1934 debugBelch("@@ evacuate: RBH %p (%s) to %p (%s)",
1935 q, info_type(q), to, info_type(to)));
1940 ASSERT(sizeofW(StgBlockedFetch) >= MIN_NONUPD_SIZE);
1941 to = copy(q,sizeofW(StgBlockedFetch),stp);
1943 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
1944 q, info_type(q), to, info_type(to)));
1951 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1952 to = copy(q,sizeofW(StgFetchMe),stp);
1954 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
1955 q, info_type(q), to, info_type(to)));
1959 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1960 to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
1962 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
1963 q, info_type(q), to, info_type(to)));
1968 return copy(q,sizeofW(StgTRecHeader),stp);
1970 case TVAR_WAIT_QUEUE:
1971 return copy(q,sizeofW(StgTVarWaitQueue),stp);
1974 return copy(q,sizeofW(StgTVar),stp);
1977 return copy(q,sizeofW(StgTRecChunk),stp);
1980 barf("evacuate: strange closure type %d", (int)(info->type));
1986 /* -----------------------------------------------------------------------------
1987 Evaluate a THUNK_SELECTOR if possible.
1989 returns: NULL if we couldn't evaluate this THUNK_SELECTOR, or
1990 a closure pointer if we evaluated it and this is the result. Note
1991 that "evaluating" the THUNK_SELECTOR doesn't necessarily mean
1992 reducing it to HNF, just that we have eliminated the selection.
1993 The result might be another thunk, or even another THUNK_SELECTOR.
1995 If the return value is non-NULL, the original selector thunk has
1996 been BLACKHOLE'd, and should be updated with an indirection or a
1997 forwarding pointer. If the return value is NULL, then the selector
1999 -------------------------------------------------------------------------- */
2001 static inline rtsBool
2002 is_to_space ( StgClosure *p )
2006 bd = Bdescr((StgPtr)p);
2007 if (HEAP_ALLOCED(p) &&
2008 ((bd->flags & BF_EVACUATED)
2009 || ((bd->flags & BF_COMPACTED) &&
2010 is_marked((P_)p,bd)))) {
2018 eval_thunk_selector( nat field, StgSelector * p )
2021 const StgInfoTable *info_ptr;
2022 StgClosure *selectee;
2024 selectee = p->selectee;
2026 // Save the real info pointer (NOTE: not the same as get_itbl()).
2027 info_ptr = p->header.info;
2029 // If the THUNK_SELECTOR is in a generation that we are not
2030 // collecting, then bail out early. We won't be able to save any
2031 // space in any case, and updating with an indirection is trickier
2033 if (Bdescr((StgPtr)p)->gen_no > N) {
2037 // BLACKHOLE the selector thunk, since it is now under evaluation.
2038 // This is important to stop us going into an infinite loop if
2039 // this selector thunk eventually refers to itself.
2040 SET_INFO(p,&stg_BLACKHOLE_info);
2044 // We don't want to end up in to-space, because this causes
2045 // problems when the GC later tries to evacuate the result of
2046 // eval_thunk_selector(). There are various ways this could
2049 // 1. following an IND_STATIC
2051 // 2. when the old generation is compacted, the mark phase updates
2052 // from-space pointers to be to-space pointers, and we can't
2053 // reliably tell which we're following (eg. from an IND_STATIC).
2055 // 3. compacting GC again: if we're looking at a constructor in
2056 // the compacted generation, it might point directly to objects
2057 // in to-space. We must bale out here, otherwise doing the selection
2058 // will result in a to-space pointer being returned.
2060 // (1) is dealt with using a BF_EVACUATED test on the
2061 // selectee. (2) and (3): we can tell if we're looking at an
2062 // object in the compacted generation that might point to
2063 // to-space objects by testing that (a) it is BF_COMPACTED, (b)
2064 // the compacted generation is being collected, and (c) the
2065 // object is marked. Only a marked object may have pointers that
2066 // point to to-space objects, because that happens when
2069 // The to-space test is now embodied in the in_to_space() inline
2070 // function, as it is re-used below.
2072 if (is_to_space(selectee)) {
2076 info = get_itbl(selectee);
2077 switch (info->type) {
2085 case CONSTR_NOCAF_STATIC:
2086 // check that the size is in range
2087 ASSERT(field < (StgWord32)(info->layout.payload.ptrs +
2088 info->layout.payload.nptrs));
2090 // Select the right field from the constructor, and check
2091 // that the result isn't in to-space. It might be in
2092 // to-space if, for example, this constructor contains
2093 // pointers to younger-gen objects (and is on the mut-once
2098 q = selectee->payload[field];
2099 if (is_to_space(q)) {
2109 case IND_OLDGEN_PERM:
2111 selectee = ((StgInd *)selectee)->indirectee;
2115 // We don't follow pointers into to-space; the constructor
2116 // has already been evacuated, so we won't save any space
2117 // leaks by evaluating this selector thunk anyhow.
2120 case THUNK_SELECTOR:
2124 // check that we don't recurse too much, re-using the
2125 // depth bound also used in evacuate().
2126 if (thunk_selector_depth >= MAX_THUNK_SELECTOR_DEPTH) {
2129 thunk_selector_depth++;
2131 val = eval_thunk_selector(info->layout.selector_offset,
2132 (StgSelector *)selectee);
2134 thunk_selector_depth--;
2139 // We evaluated this selector thunk, so update it with
2140 // an indirection. NOTE: we don't use UPD_IND here,
2141 // because we are guaranteed that p is in a generation
2142 // that we are collecting, and we never want to put the
2143 // indirection on a mutable list.
2145 // For the purposes of LDV profiling, we have destroyed
2146 // the original selector thunk.
2147 SET_INFO(p, info_ptr);
2148 LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(selectee);
2150 ((StgInd *)selectee)->indirectee = val;
2151 SET_INFO(selectee,&stg_IND_info);
2153 // For the purposes of LDV profiling, we have created an
2155 LDV_RECORD_CREATE(selectee);
2172 case SE_CAF_BLACKHOLE:
2184 // not evaluated yet
2188 barf("eval_thunk_selector: strange selectee %d",
2193 // We didn't manage to evaluate this thunk; restore the old info pointer
2194 SET_INFO(p, info_ptr);
2198 /* -----------------------------------------------------------------------------
2199 move_TSO is called to update the TSO structure after it has been
2200 moved from one place to another.
2201 -------------------------------------------------------------------------- */
2204 move_TSO (StgTSO *src, StgTSO *dest)
2208 // relocate the stack pointer...
2209 diff = (StgPtr)dest - (StgPtr)src; // In *words*
2210 dest->sp = (StgPtr)dest->sp + diff;
2213 /* Similar to scavenge_large_bitmap(), but we don't write back the
2214 * pointers we get back from evacuate().
2217 scavenge_large_srt_bitmap( StgLargeSRT *large_srt )
2224 bitmap = large_srt->l.bitmap[b];
2225 size = (nat)large_srt->l.size;
2226 p = (StgClosure **)large_srt->srt;
2227 for (i = 0; i < size; ) {
2228 if ((bitmap & 1) != 0) {
2233 if (i % BITS_IN(W_) == 0) {
2235 bitmap = large_srt->l.bitmap[b];
2237 bitmap = bitmap >> 1;
2242 /* evacuate the SRT. If srt_bitmap is zero, then there isn't an
2243 * srt field in the info table. That's ok, because we'll
2244 * never dereference it.
2247 scavenge_srt (StgClosure **srt, nat srt_bitmap)
2252 bitmap = srt_bitmap;
2255 if (bitmap == (StgHalfWord)(-1)) {
2256 scavenge_large_srt_bitmap( (StgLargeSRT *)srt );
2260 while (bitmap != 0) {
2261 if ((bitmap & 1) != 0) {
2262 #ifdef ENABLE_WIN32_DLL_SUPPORT
2263 // Special-case to handle references to closures hiding out in DLLs, since
2264 // double indirections required to get at those. The code generator knows
2265 // which is which when generating the SRT, so it stores the (indirect)
2266 // reference to the DLL closure in the table by first adding one to it.
2267 // We check for this here, and undo the addition before evacuating it.
2269 // If the SRT entry hasn't got bit 0 set, the SRT entry points to a
2270 // closure that's fixed at link-time, and no extra magic is required.
2271 if ( (unsigned long)(*srt) & 0x1 ) {
2272 evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
2281 bitmap = bitmap >> 1;
2287 scavenge_thunk_srt(const StgInfoTable *info)
2289 StgThunkInfoTable *thunk_info;
2291 thunk_info = itbl_to_thunk_itbl(info);
2292 scavenge_srt((StgClosure **)GET_SRT(thunk_info), thunk_info->i.srt_bitmap);
2296 scavenge_fun_srt(const StgInfoTable *info)
2298 StgFunInfoTable *fun_info;
2300 fun_info = itbl_to_fun_itbl(info);
2301 scavenge_srt((StgClosure **)GET_FUN_SRT(fun_info), fun_info->i.srt_bitmap);
2305 scavenge_ret_srt(const StgInfoTable *info)
2307 StgRetInfoTable *ret_info;
2309 ret_info = itbl_to_ret_itbl(info);
2310 scavenge_srt((StgClosure **)GET_SRT(ret_info), ret_info->i.srt_bitmap);
2313 /* -----------------------------------------------------------------------------
2315 -------------------------------------------------------------------------- */
2318 scavengeTSO (StgTSO *tso)
2320 // chase the link field for any TSOs on the same queue
2321 tso->link = (StgTSO *)evacuate((StgClosure *)tso->link);
2322 if ( tso->why_blocked == BlockedOnMVar
2323 || tso->why_blocked == BlockedOnBlackHole
2324 || tso->why_blocked == BlockedOnException
2326 || tso->why_blocked == BlockedOnGA
2327 || tso->why_blocked == BlockedOnGA_NoSend
2330 tso->block_info.closure = evacuate(tso->block_info.closure);
2332 if ( tso->blocked_exceptions != NULL ) {
2333 tso->blocked_exceptions =
2334 (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
2337 // scavange current transaction record
2338 tso->trec = (StgTRecHeader *)evacuate((StgClosure *)tso->trec);
2340 // scavenge this thread's stack
2341 scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
2344 /* -----------------------------------------------------------------------------
2345 Blocks of function args occur on the stack (at the top) and
2347 -------------------------------------------------------------------------- */
2349 STATIC_INLINE StgPtr
2350 scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
2357 switch (fun_info->f.fun_type) {
2359 bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
2360 size = BITMAP_SIZE(fun_info->f.b.bitmap);
2363 size = GET_FUN_LARGE_BITMAP(fun_info)->size;
2364 scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
2368 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2369 size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->f.fun_type]);
2372 if ((bitmap & 1) == 0) {
2373 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2376 bitmap = bitmap >> 1;
2384 STATIC_INLINE StgPtr
2385 scavenge_PAP (StgPAP *pap)
2388 StgWord bitmap, size;
2389 StgFunInfoTable *fun_info;
2391 pap->fun = evacuate(pap->fun);
2392 fun_info = get_fun_itbl(pap->fun);
2393 ASSERT(fun_info->i.type != PAP);
2395 p = (StgPtr)pap->payload;
2398 switch (fun_info->f.fun_type) {
2400 bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
2403 scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
2407 scavenge_large_bitmap((StgPtr)pap->payload, BCO_BITMAP(pap->fun), size);
2411 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2415 if ((bitmap & 1) == 0) {
2416 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2419 bitmap = bitmap >> 1;
2427 /* -----------------------------------------------------------------------------
2428 Scavenge a given step until there are no more objects in this step
2431 evac_gen is set by the caller to be either zero (for a step in a
2432 generation < N) or G where G is the generation of the step being
2435 We sometimes temporarily change evac_gen back to zero if we're
2436 scavenging a mutable object where early promotion isn't such a good
2438 -------------------------------------------------------------------------- */
2446 nat saved_evac_gen = evac_gen;
2451 failed_to_evac = rtsFalse;
2453 /* scavenge phase - standard breadth-first scavenging of the
2457 while (bd != stp->hp_bd || p < stp->hp) {
2459 // If we're at the end of this block, move on to the next block
2460 if (bd != stp->hp_bd && p == bd->free) {
2466 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2467 info = get_itbl((StgClosure *)p);
2469 ASSERT(thunk_selector_depth == 0);
2472 switch (info->type) {
2476 StgMVar *mvar = ((StgMVar *)p);
2478 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
2479 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
2480 mvar->value = evacuate((StgClosure *)mvar->value);
2481 evac_gen = saved_evac_gen;
2482 failed_to_evac = rtsTrue; // mutable.
2483 p += sizeofW(StgMVar);
2488 scavenge_fun_srt(info);
2489 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2490 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2491 p += sizeofW(StgHeader) + 2;
2495 scavenge_thunk_srt(info);
2497 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2498 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2499 p += sizeofW(StgHeader) + 2;
2503 scavenge_thunk_srt(info);
2504 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2505 p += sizeofW(StgHeader) + 1;
2509 scavenge_fun_srt(info);
2511 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2512 p += sizeofW(StgHeader) + 1;
2516 scavenge_thunk_srt(info);
2517 p += sizeofW(StgHeader) + 1;
2521 scavenge_fun_srt(info);
2523 p += sizeofW(StgHeader) + 1;
2527 scavenge_thunk_srt(info);
2528 p += sizeofW(StgHeader) + 2;
2532 scavenge_fun_srt(info);
2534 p += sizeofW(StgHeader) + 2;
2538 scavenge_thunk_srt(info);
2539 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2540 p += sizeofW(StgHeader) + 2;
2544 scavenge_fun_srt(info);
2546 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2547 p += sizeofW(StgHeader) + 2;
2551 scavenge_fun_srt(info);
2555 scavenge_thunk_srt(info);
2566 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2567 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2568 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2570 p += info->layout.payload.nptrs;
2575 StgBCO *bco = (StgBCO *)p;
2576 bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
2577 bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
2578 bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
2579 bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
2580 p += bco_sizeW(bco);
2585 if (stp->gen->no != 0) {
2588 // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an
2589 // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
2590 LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
2593 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
2595 SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
2597 // We pretend that p has just been created.
2598 LDV_RECORD_CREATE((StgClosure *)p);
2601 case IND_OLDGEN_PERM:
2602 ((StgInd *)p)->indirectee = evacuate(((StgInd *)p)->indirectee);
2603 p += sizeofW(StgInd);
2608 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2609 evac_gen = saved_evac_gen;
2610 failed_to_evac = rtsTrue; // mutable anyhow
2611 p += sizeofW(StgMutVar);
2615 case SE_CAF_BLACKHOLE:
2618 p += BLACKHOLE_sizeW();
2621 case THUNK_SELECTOR:
2623 StgSelector *s = (StgSelector *)p;
2624 s->selectee = evacuate(s->selectee);
2625 p += THUNK_SELECTOR_sizeW();
2629 // A chunk of stack saved in a heap object
2632 StgAP_STACK *ap = (StgAP_STACK *)p;
2634 ap->fun = evacuate(ap->fun);
2635 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2636 p = (StgPtr)ap->payload + ap->size;
2642 p = scavenge_PAP((StgPAP *)p);
2646 // nothing to follow
2647 p += arr_words_sizeW((StgArrWords *)p);
2651 // follow everything
2655 evac_gen = 0; // repeatedly mutable
2656 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2657 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2658 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2660 evac_gen = saved_evac_gen;
2661 failed_to_evac = rtsTrue; // mutable anyhow.
2665 case MUT_ARR_PTRS_FROZEN:
2666 case MUT_ARR_PTRS_FROZEN0:
2667 // follow everything
2671 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2672 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2673 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2675 // it's tempting to recordMutable() if failed_to_evac is
2676 // false, but that breaks some assumptions (eg. every
2677 // closure on the mutable list is supposed to have the MUT
2678 // flag set, and MUT_ARR_PTRS_FROZEN doesn't).
2684 StgTSO *tso = (StgTSO *)p;
2687 evac_gen = saved_evac_gen;
2688 failed_to_evac = rtsTrue; // mutable anyhow.
2689 p += tso_sizeW(tso);
2697 nat size, ptrs, nonptrs, vhs;
2699 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2701 StgRBH *rbh = (StgRBH *)p;
2702 (StgClosure *)rbh->blocking_queue =
2703 evacuate((StgClosure *)rbh->blocking_queue);
2704 failed_to_evac = rtsTrue; // mutable anyhow.
2706 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2707 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2708 // ToDo: use size of reverted closure here!
2709 p += BLACKHOLE_sizeW();
2715 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2716 // follow the pointer to the node which is being demanded
2717 (StgClosure *)bf->node =
2718 evacuate((StgClosure *)bf->node);
2719 // follow the link to the rest of the blocking queue
2720 (StgClosure *)bf->link =
2721 evacuate((StgClosure *)bf->link);
2723 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
2724 bf, info_type((StgClosure *)bf),
2725 bf->node, info_type(bf->node)));
2726 p += sizeofW(StgBlockedFetch);
2734 p += sizeofW(StgFetchMe);
2735 break; // nothing to do in this case
2739 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
2740 (StgClosure *)fmbq->blocking_queue =
2741 evacuate((StgClosure *)fmbq->blocking_queue);
2743 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
2744 p, info_type((StgClosure *)p)));
2745 p += sizeofW(StgFetchMeBlockingQueue);
2750 case TVAR_WAIT_QUEUE:
2752 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
2754 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
2755 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
2756 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
2757 evac_gen = saved_evac_gen;
2758 failed_to_evac = rtsTrue; // mutable
2759 p += sizeofW(StgTVarWaitQueue);
2765 StgTVar *tvar = ((StgTVar *) p);
2767 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
2768 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
2769 evac_gen = saved_evac_gen;
2770 failed_to_evac = rtsTrue; // mutable
2771 p += sizeofW(StgTVar);
2777 StgTRecHeader *trec = ((StgTRecHeader *) p);
2779 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
2780 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
2781 evac_gen = saved_evac_gen;
2782 failed_to_evac = rtsTrue; // mutable
2783 p += sizeofW(StgTRecHeader);
2790 StgTRecChunk *tc = ((StgTRecChunk *) p);
2791 TRecEntry *e = &(tc -> entries[0]);
2793 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
2794 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
2795 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
2796 e->expected_value = evacuate((StgClosure*)e->expected_value);
2797 e->new_value = evacuate((StgClosure*)e->new_value);
2799 evac_gen = saved_evac_gen;
2800 failed_to_evac = rtsTrue; // mutable
2801 p += sizeofW(StgTRecChunk);
2806 barf("scavenge: unimplemented/strange closure type %d @ %p",
2811 * We need to record the current object on the mutable list if
2812 * (a) It is actually mutable, or
2813 * (b) It contains pointers to a younger generation.
2814 * Case (b) arises if we didn't manage to promote everything that
2815 * the current object points to into the current generation.
2817 if (failed_to_evac) {
2818 failed_to_evac = rtsFalse;
2819 recordMutableGen((StgClosure *)q, stp->gen);
2827 /* -----------------------------------------------------------------------------
2828 Scavenge everything on the mark stack.
2830 This is slightly different from scavenge():
2831 - we don't walk linearly through the objects, so the scavenger
2832 doesn't need to advance the pointer on to the next object.
2833 -------------------------------------------------------------------------- */
2836 scavenge_mark_stack(void)
2842 evac_gen = oldest_gen->no;
2843 saved_evac_gen = evac_gen;
2846 while (!mark_stack_empty()) {
2847 p = pop_mark_stack();
2849 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2850 info = get_itbl((StgClosure *)p);
2853 switch (info->type) {
2857 StgMVar *mvar = ((StgMVar *)p);
2859 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
2860 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
2861 mvar->value = evacuate((StgClosure *)mvar->value);
2862 evac_gen = saved_evac_gen;
2863 failed_to_evac = rtsTrue; // mutable.
2868 scavenge_fun_srt(info);
2869 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2870 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2874 scavenge_thunk_srt(info);
2876 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2877 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2882 scavenge_fun_srt(info);
2883 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2888 scavenge_thunk_srt(info);
2891 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2896 scavenge_fun_srt(info);
2901 scavenge_thunk_srt(info);
2909 scavenge_fun_srt(info);
2913 scavenge_thunk_srt(info);
2924 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2925 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2926 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2932 StgBCO *bco = (StgBCO *)p;
2933 bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
2934 bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
2935 bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
2936 bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
2941 // don't need to do anything here: the only possible case
2942 // is that we're in a 1-space compacting collector, with
2943 // no "old" generation.
2947 case IND_OLDGEN_PERM:
2948 ((StgInd *)p)->indirectee =
2949 evacuate(((StgInd *)p)->indirectee);
2954 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2955 evac_gen = saved_evac_gen;
2956 failed_to_evac = rtsTrue;
2960 case SE_CAF_BLACKHOLE:
2966 case THUNK_SELECTOR:
2968 StgSelector *s = (StgSelector *)p;
2969 s->selectee = evacuate(s->selectee);
2973 // A chunk of stack saved in a heap object
2976 StgAP_STACK *ap = (StgAP_STACK *)p;
2978 ap->fun = evacuate(ap->fun);
2979 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2985 scavenge_PAP((StgPAP *)p);
2989 // follow everything
2993 evac_gen = 0; // repeatedly mutable
2994 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2995 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2996 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2998 evac_gen = saved_evac_gen;
2999 failed_to_evac = rtsTrue; // mutable anyhow.
3003 case MUT_ARR_PTRS_FROZEN:
3004 case MUT_ARR_PTRS_FROZEN0:
3005 // follow everything
3009 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3010 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3011 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3018 StgTSO *tso = (StgTSO *)p;
3021 evac_gen = saved_evac_gen;
3022 failed_to_evac = rtsTrue;
3030 nat size, ptrs, nonptrs, vhs;
3032 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3034 StgRBH *rbh = (StgRBH *)p;
3035 bh->blocking_queue =
3036 (StgTSO *)evacuate((StgClosure *)bh->blocking_queue);
3037 failed_to_evac = rtsTrue; // mutable anyhow.
3039 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3040 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3046 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3047 // follow the pointer to the node which is being demanded
3048 (StgClosure *)bf->node =
3049 evacuate((StgClosure *)bf->node);
3050 // follow the link to the rest of the blocking queue
3051 (StgClosure *)bf->link =
3052 evacuate((StgClosure *)bf->link);
3054 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3055 bf, info_type((StgClosure *)bf),
3056 bf->node, info_type(bf->node)));
3064 break; // nothing to do in this case
3068 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3069 (StgClosure *)fmbq->blocking_queue =
3070 evacuate((StgClosure *)fmbq->blocking_queue);
3072 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3073 p, info_type((StgClosure *)p)));
3078 case TVAR_WAIT_QUEUE:
3080 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3082 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3083 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3084 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3085 evac_gen = saved_evac_gen;
3086 failed_to_evac = rtsTrue; // mutable
3092 StgTVar *tvar = ((StgTVar *) p);
3094 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3095 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3096 evac_gen = saved_evac_gen;
3097 failed_to_evac = rtsTrue; // mutable
3104 StgTRecChunk *tc = ((StgTRecChunk *) p);
3105 TRecEntry *e = &(tc -> entries[0]);
3107 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3108 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3109 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3110 e->expected_value = evacuate((StgClosure*)e->expected_value);
3111 e->new_value = evacuate((StgClosure*)e->new_value);
3113 evac_gen = saved_evac_gen;
3114 failed_to_evac = rtsTrue; // mutable
3120 StgTRecHeader *trec = ((StgTRecHeader *) p);
3122 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3123 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3124 evac_gen = saved_evac_gen;
3125 failed_to_evac = rtsTrue; // mutable
3130 barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p",
3134 if (failed_to_evac) {
3135 failed_to_evac = rtsFalse;
3136 recordMutableGen((StgClosure *)q, &generations[evac_gen]);
3139 // mark the next bit to indicate "scavenged"
3140 mark(q+1, Bdescr(q));
3142 } // while (!mark_stack_empty())
3144 // start a new linear scan if the mark stack overflowed at some point
3145 if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
3146 IF_DEBUG(gc, debugBelch("scavenge_mark_stack: starting linear scan"));
3147 mark_stack_overflowed = rtsFalse;
3148 oldgen_scan_bd = oldest_gen->steps[0].blocks;
3149 oldgen_scan = oldgen_scan_bd->start;
3152 if (oldgen_scan_bd) {
3153 // push a new thing on the mark stack
3155 // find a closure that is marked but not scavenged, and start
3157 while (oldgen_scan < oldgen_scan_bd->free
3158 && !is_marked(oldgen_scan,oldgen_scan_bd)) {
3162 if (oldgen_scan < oldgen_scan_bd->free) {
3164 // already scavenged?
3165 if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
3166 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3169 push_mark_stack(oldgen_scan);
3170 // ToDo: bump the linear scan by the actual size of the object
3171 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3175 oldgen_scan_bd = oldgen_scan_bd->link;
3176 if (oldgen_scan_bd != NULL) {
3177 oldgen_scan = oldgen_scan_bd->start;
3183 /* -----------------------------------------------------------------------------
3184 Scavenge one object.
3186 This is used for objects that are temporarily marked as mutable
3187 because they contain old-to-new generation pointers. Only certain
3188 objects can have this property.
3189 -------------------------------------------------------------------------- */
3192 scavenge_one(StgPtr p)
3194 const StgInfoTable *info;
3195 nat saved_evac_gen = evac_gen;
3198 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3199 info = get_itbl((StgClosure *)p);
3201 switch (info->type) {
3205 StgMVar *mvar = ((StgMVar *)p);
3207 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
3208 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
3209 mvar->value = evacuate((StgClosure *)mvar->value);
3210 evac_gen = saved_evac_gen;
3211 failed_to_evac = rtsTrue; // mutable.
3216 case FUN_1_0: // hardly worth specialising these guys
3239 end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3240 for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
3241 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3248 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3249 evac_gen = saved_evac_gen;
3250 failed_to_evac = rtsTrue; // mutable anyhow
3254 case SE_CAF_BLACKHOLE:
3259 case THUNK_SELECTOR:
3261 StgSelector *s = (StgSelector *)p;
3262 s->selectee = evacuate(s->selectee);
3268 StgAP_STACK *ap = (StgAP_STACK *)p;
3270 ap->fun = evacuate(ap->fun);
3271 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3272 p = (StgPtr)ap->payload + ap->size;
3278 p = scavenge_PAP((StgPAP *)p);
3282 // nothing to follow
3287 // follow everything
3290 evac_gen = 0; // repeatedly mutable
3291 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3292 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3293 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3295 evac_gen = saved_evac_gen;
3296 failed_to_evac = rtsTrue;
3300 case MUT_ARR_PTRS_FROZEN:
3301 case MUT_ARR_PTRS_FROZEN0:
3303 // follow everything
3306 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3307 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3308 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3315 StgTSO *tso = (StgTSO *)p;
3317 evac_gen = 0; // repeatedly mutable
3319 evac_gen = saved_evac_gen;
3320 failed_to_evac = rtsTrue;
3328 nat size, ptrs, nonptrs, vhs;
3330 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3332 StgRBH *rbh = (StgRBH *)p;
3333 (StgClosure *)rbh->blocking_queue =
3334 evacuate((StgClosure *)rbh->blocking_queue);
3335 failed_to_evac = rtsTrue; // mutable anyhow.
3337 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3338 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3339 // ToDo: use size of reverted closure here!
3345 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3346 // follow the pointer to the node which is being demanded
3347 (StgClosure *)bf->node =
3348 evacuate((StgClosure *)bf->node);
3349 // follow the link to the rest of the blocking queue
3350 (StgClosure *)bf->link =
3351 evacuate((StgClosure *)bf->link);
3353 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3354 bf, info_type((StgClosure *)bf),
3355 bf->node, info_type(bf->node)));
3363 break; // nothing to do in this case
3367 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3368 (StgClosure *)fmbq->blocking_queue =
3369 evacuate((StgClosure *)fmbq->blocking_queue);
3371 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3372 p, info_type((StgClosure *)p)));
3377 case TVAR_WAIT_QUEUE:
3379 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3381 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3382 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3383 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3384 evac_gen = saved_evac_gen;
3385 failed_to_evac = rtsTrue; // mutable
3391 StgTVar *tvar = ((StgTVar *) p);
3393 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3394 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3395 evac_gen = saved_evac_gen;
3396 failed_to_evac = rtsTrue; // mutable
3402 StgTRecHeader *trec = ((StgTRecHeader *) p);
3404 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3405 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3406 evac_gen = saved_evac_gen;
3407 failed_to_evac = rtsTrue; // mutable
3414 StgTRecChunk *tc = ((StgTRecChunk *) p);
3415 TRecEntry *e = &(tc -> entries[0]);
3417 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3418 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3419 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3420 e->expected_value = evacuate((StgClosure*)e->expected_value);
3421 e->new_value = evacuate((StgClosure*)e->new_value);
3423 evac_gen = saved_evac_gen;
3424 failed_to_evac = rtsTrue; // mutable
3429 case IND_OLDGEN_PERM:
3432 /* Careful here: a THUNK can be on the mutable list because
3433 * it contains pointers to young gen objects. If such a thunk
3434 * is updated, the IND_OLDGEN will be added to the mutable
3435 * list again, and we'll scavenge it twice. evacuate()
3436 * doesn't check whether the object has already been
3437 * evacuated, so we perform that check here.
3439 StgClosure *q = ((StgInd *)p)->indirectee;
3440 if (HEAP_ALLOCED(q) && Bdescr((StgPtr)q)->flags & BF_EVACUATED) {
3443 ((StgInd *)p)->indirectee = evacuate(q);
3446 #if 0 && defined(DEBUG)
3447 if (RtsFlags.DebugFlags.gc)
3448 /* Debugging code to print out the size of the thing we just
3452 StgPtr start = gen->steps[0].scan;
3453 bdescr *start_bd = gen->steps[0].scan_bd;
3455 scavenge(&gen->steps[0]);
3456 if (start_bd != gen->steps[0].scan_bd) {
3457 size += (P_)BLOCK_ROUND_UP(start) - start;
3458 start_bd = start_bd->link;
3459 while (start_bd != gen->steps[0].scan_bd) {
3460 size += BLOCK_SIZE_W;
3461 start_bd = start_bd->link;
3463 size += gen->steps[0].scan -
3464 (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
3466 size = gen->steps[0].scan - start;
3468 debugBelch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
3474 barf("scavenge_one: strange object %d", (int)(info->type));
3477 no_luck = failed_to_evac;
3478 failed_to_evac = rtsFalse;
3482 /* -----------------------------------------------------------------------------
3483 Scavenging mutable lists.
3485 We treat the mutable list of each generation > N (i.e. all the
3486 generations older than the one being collected) as roots. We also
3487 remove non-mutable objects from the mutable list at this point.
3488 -------------------------------------------------------------------------- */
3491 scavenge_mutable_list(generation *gen)
3496 bd = gen->saved_mut_list;
3499 for (; bd != NULL; bd = bd->link) {
3500 for (q = bd->start; q < bd->free; q++) {
3502 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3503 if (scavenge_one(p)) {
3504 /* didn't manage to promote everything, so put the
3505 * object back on the list.
3507 recordMutableGen((StgClosure *)p,gen);
3512 // free the old mut_list
3513 freeChain(gen->saved_mut_list);
3514 gen->saved_mut_list = NULL;
3519 scavenge_static(void)
3521 StgClosure* p = static_objects;
3522 const StgInfoTable *info;
3524 /* Always evacuate straight to the oldest generation for static
3526 evac_gen = oldest_gen->no;
3528 /* keep going until we've scavenged all the objects on the linked
3530 while (p != END_OF_STATIC_LIST) {
3532 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3535 if (info->type==RBH)
3536 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3538 // make sure the info pointer is into text space
3540 /* Take this object *off* the static_objects list,
3541 * and put it on the scavenged_static_objects list.
3543 static_objects = STATIC_LINK(info,p);
3544 STATIC_LINK(info,p) = scavenged_static_objects;
3545 scavenged_static_objects = p;
3547 switch (info -> type) {
3551 StgInd *ind = (StgInd *)p;
3552 ind->indirectee = evacuate(ind->indirectee);
3554 /* might fail to evacuate it, in which case we have to pop it
3555 * back on the mutable list of the oldest generation. We
3556 * leave it *on* the scavenged_static_objects list, though,
3557 * in case we visit this object again.
3559 if (failed_to_evac) {
3560 failed_to_evac = rtsFalse;
3561 recordMutableGen((StgClosure *)p,oldest_gen);
3567 scavenge_thunk_srt(info);
3571 scavenge_fun_srt(info);
3578 next = (P_)p->payload + info->layout.payload.ptrs;
3579 // evacuate the pointers
3580 for (q = (P_)p->payload; q < next; q++) {
3581 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3587 barf("scavenge_static: strange closure %d", (int)(info->type));
3590 ASSERT(failed_to_evac == rtsFalse);
3592 /* get the next static object from the list. Remember, there might
3593 * be more stuff on this list now that we've done some evacuating!
3594 * (static_objects is a global)
3600 /* -----------------------------------------------------------------------------
3601 scavenge a chunk of memory described by a bitmap
3602 -------------------------------------------------------------------------- */
3605 scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
3611 bitmap = large_bitmap->bitmap[b];
3612 for (i = 0; i < size; ) {
3613 if ((bitmap & 1) == 0) {
3614 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3618 if (i % BITS_IN(W_) == 0) {
3620 bitmap = large_bitmap->bitmap[b];
3622 bitmap = bitmap >> 1;
3627 STATIC_INLINE StgPtr
3628 scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap)
3631 if ((bitmap & 1) == 0) {
3632 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3635 bitmap = bitmap >> 1;
3641 /* -----------------------------------------------------------------------------
3642 scavenge_stack walks over a section of stack and evacuates all the
3643 objects pointed to by it. We can use the same code for walking
3644 AP_STACK_UPDs, since these are just sections of copied stack.
3645 -------------------------------------------------------------------------- */
3649 scavenge_stack(StgPtr p, StgPtr stack_end)
3651 const StgRetInfoTable* info;
3655 //IF_DEBUG(sanity, debugBelch(" scavenging stack between %p and %p", p, stack_end));
3658 * Each time around this loop, we are looking at a chunk of stack
3659 * that starts with an activation record.
3662 while (p < stack_end) {
3663 info = get_ret_itbl((StgClosure *)p);
3665 switch (info->i.type) {
3668 ((StgUpdateFrame *)p)->updatee
3669 = evacuate(((StgUpdateFrame *)p)->updatee);
3670 p += sizeofW(StgUpdateFrame);
3673 // small bitmap (< 32 entries, or 64 on a 64-bit machine)
3674 case CATCH_STM_FRAME:
3675 case CATCH_RETRY_FRAME:
3676 case ATOMICALLY_FRAME:
3681 bitmap = BITMAP_BITS(info->i.layout.bitmap);
3682 size = BITMAP_SIZE(info->i.layout.bitmap);
3683 // NOTE: the payload starts immediately after the info-ptr, we
3684 // don't have an StgHeader in the same sense as a heap closure.
3686 p = scavenge_small_bitmap(p, size, bitmap);
3689 scavenge_srt((StgClosure **)GET_SRT(info), info->i.srt_bitmap);
3697 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3700 size = BCO_BITMAP_SIZE(bco);
3701 scavenge_large_bitmap(p, BCO_BITMAP(bco), size);
3706 // large bitmap (> 32 entries, or > 64 on a 64-bit machine)
3712 size = GET_LARGE_BITMAP(&info->i)->size;
3714 scavenge_large_bitmap(p, GET_LARGE_BITMAP(&info->i), size);
3716 // and don't forget to follow the SRT
3720 // Dynamic bitmap: the mask is stored on the stack, and
3721 // there are a number of non-pointers followed by a number
3722 // of pointers above the bitmapped area. (see StgMacros.h,
3727 dyn = ((StgRetDyn *)p)->liveness;
3729 // traverse the bitmap first
3730 bitmap = RET_DYN_LIVENESS(dyn);
3731 p = (P_)&((StgRetDyn *)p)->payload[0];
3732 size = RET_DYN_BITMAP_SIZE;
3733 p = scavenge_small_bitmap(p, size, bitmap);
3735 // skip over the non-ptr words
3736 p += RET_DYN_NONPTRS(dyn) + RET_DYN_NONPTR_REGS_SIZE;
3738 // follow the ptr words
3739 for (size = RET_DYN_PTRS(dyn); size > 0; size--) {
3740 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3748 StgRetFun *ret_fun = (StgRetFun *)p;
3749 StgFunInfoTable *fun_info;
3751 ret_fun->fun = evacuate(ret_fun->fun);
3752 fun_info = get_fun_itbl(ret_fun->fun);
3753 p = scavenge_arg_block(fun_info, ret_fun->payload);
3758 barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->i.type));
3763 /*-----------------------------------------------------------------------------
3764 scavenge the large object list.
3766 evac_gen set by caller; similar games played with evac_gen as with
3767 scavenge() - see comment at the top of scavenge(). Most large
3768 objects are (repeatedly) mutable, so most of the time evac_gen will
3770 --------------------------------------------------------------------------- */
3773 scavenge_large(step *stp)
3778 bd = stp->new_large_objects;
3780 for (; bd != NULL; bd = stp->new_large_objects) {
3782 /* take this object *off* the large objects list and put it on
3783 * the scavenged large objects list. This is so that we can
3784 * treat new_large_objects as a stack and push new objects on
3785 * the front when evacuating.
3787 stp->new_large_objects = bd->link;
3788 dbl_link_onto(bd, &stp->scavenged_large_objects);
3790 // update the block count in this step.
3791 stp->n_scavenged_large_blocks += bd->blocks;
3794 if (scavenge_one(p)) {
3795 recordMutableGen((StgClosure *)p, stp->gen);
3800 /* -----------------------------------------------------------------------------
3801 Initialising the static object & mutable lists
3802 -------------------------------------------------------------------------- */
3805 zero_static_object_list(StgClosure* first_static)
3809 const StgInfoTable *info;
3811 for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
3813 link = STATIC_LINK(info, p);
3814 STATIC_LINK(info,p) = NULL;
3818 /* -----------------------------------------------------------------------------
3820 -------------------------------------------------------------------------- */
3827 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
3828 c = (StgIndStatic *)c->static_link)
3830 SET_INFO(c, c->saved_info);
3831 c->saved_info = NULL;
3832 // could, but not necessary: c->static_link = NULL;
3834 revertible_caf_list = NULL;
3838 markCAFs( evac_fn evac )
3842 for (c = (StgIndStatic *)caf_list; c != NULL;
3843 c = (StgIndStatic *)c->static_link)
3845 evac(&c->indirectee);
3847 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
3848 c = (StgIndStatic *)c->static_link)
3850 evac(&c->indirectee);
3854 /* -----------------------------------------------------------------------------
3855 Sanity code for CAF garbage collection.
3857 With DEBUG turned on, we manage a CAF list in addition to the SRT
3858 mechanism. After GC, we run down the CAF list and blackhole any
3859 CAFs which have been garbage collected. This means we get an error
3860 whenever the program tries to enter a garbage collected CAF.
3862 Any garbage collected CAFs are taken off the CAF list at the same
3864 -------------------------------------------------------------------------- */
3866 #if 0 && defined(DEBUG)
3873 const StgInfoTable *info;
3884 ASSERT(info->type == IND_STATIC);
3886 if (STATIC_LINK(info,p) == NULL) {
3887 IF_DEBUG(gccafs, debugBelch("CAF gc'd at 0x%04lx", (long)p));
3889 SET_INFO(p,&stg_BLACKHOLE_info);
3890 p = STATIC_LINK2(info,p);
3894 pp = &STATIC_LINK2(info,p);
3901 // debugBelch("%d CAFs live", i);
3906 /* -----------------------------------------------------------------------------
3909 Whenever a thread returns to the scheduler after possibly doing
3910 some work, we have to run down the stack and black-hole all the
3911 closures referred to by update frames.
3912 -------------------------------------------------------------------------- */
3915 threadLazyBlackHole(StgTSO *tso)
3918 StgRetInfoTable *info;
3922 stack_end = &tso->stack[tso->stack_size];
3924 frame = (StgClosure *)tso->sp;
3927 info = get_ret_itbl(frame);
3929 switch (info->i.type) {
3932 bh = ((StgUpdateFrame *)frame)->updatee;
3934 /* if the thunk is already blackholed, it means we've also
3935 * already blackholed the rest of the thunks on this stack,
3936 * so we can stop early.
3938 * The blackhole made for a CAF is a CAF_BLACKHOLE, so they
3939 * don't interfere with this optimisation.
3941 if (bh->header.info == &stg_BLACKHOLE_info) {
3945 if (bh->header.info != &stg_CAF_BLACKHOLE_info) {
3946 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
3947 debugBelch("Unexpected lazy BHing required at 0x%04x\n",(int)bh);
3951 // We pretend that bh is now dead.
3952 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
3954 SET_INFO(bh,&stg_BLACKHOLE_info);
3956 // We pretend that bh has just been created.
3957 LDV_RECORD_CREATE(bh);
3960 frame = (StgClosure *) ((StgUpdateFrame *)frame + 1);
3966 // normal stack frames; do nothing except advance the pointer
3968 frame = (StgClosure *)((StgPtr)frame + stack_frame_sizeW(frame));
3974 /* -----------------------------------------------------------------------------
3977 * Code largely pinched from old RTS, then hacked to bits. We also do
3978 * lazy black holing here.
3980 * -------------------------------------------------------------------------- */
3982 struct stack_gap { StgWord gap_size; struct stack_gap *next_gap; };
3985 threadSqueezeStack(StgTSO *tso)
3988 rtsBool prev_was_update_frame;
3989 StgClosure *updatee = NULL;
3991 StgRetInfoTable *info;
3992 StgWord current_gap_size;
3993 struct stack_gap *gap;
3996 // Traverse the stack upwards, replacing adjacent update frames
3997 // with a single update frame and a "stack gap". A stack gap
3998 // contains two values: the size of the gap, and the distance
3999 // to the next gap (or the stack top).
4001 bottom = &(tso->stack[tso->stack_size]);
4005 ASSERT(frame < bottom);
4007 prev_was_update_frame = rtsFalse;
4008 current_gap_size = 0;
4009 gap = (struct stack_gap *) (tso->sp - sizeofW(StgUpdateFrame));
4011 while (frame < bottom) {
4013 info = get_ret_itbl((StgClosure *)frame);
4014 switch (info->i.type) {
4018 StgUpdateFrame *upd = (StgUpdateFrame *)frame;
4020 if (upd->updatee->header.info == &stg_BLACKHOLE_info) {
4022 // found a BLACKHOLE'd update frame; we've been here
4023 // before, in a previous GC, so just break out.
4025 // Mark the end of the gap, if we're in one.
4026 if (current_gap_size != 0) {
4027 gap = (struct stack_gap *)(frame-sizeofW(StgUpdateFrame));
4030 frame += sizeofW(StgUpdateFrame);
4031 goto done_traversing;
4034 if (prev_was_update_frame) {
4036 TICK_UPD_SQUEEZED();
4037 /* wasn't there something about update squeezing and ticky to be
4038 * sorted out? oh yes: we aren't counting each enter properly
4039 * in this case. See the log somewhere. KSW 1999-04-21
4041 * Check two things: that the two update frames don't point to
4042 * the same object, and that the updatee_bypass isn't already an
4043 * indirection. Both of these cases only happen when we're in a
4044 * block hole-style loop (and there are multiple update frames
4045 * on the stack pointing to the same closure), but they can both
4046 * screw us up if we don't check.
4048 if (upd->updatee != updatee && !closure_IND(upd->updatee)) {
4049 UPD_IND_NOLOCK(upd->updatee, updatee);
4052 // now mark this update frame as a stack gap. The gap
4053 // marker resides in the bottom-most update frame of
4054 // the series of adjacent frames, and covers all the
4055 // frames in this series.
4056 current_gap_size += sizeofW(StgUpdateFrame);
4057 ((struct stack_gap *)frame)->gap_size = current_gap_size;
4058 ((struct stack_gap *)frame)->next_gap = gap;
4060 frame += sizeofW(StgUpdateFrame);
4064 // single update frame, or the topmost update frame in a series
4066 StgClosure *bh = upd->updatee;
4068 // Do lazy black-holing
4069 if (bh->header.info != &stg_BLACKHOLE_info &&
4070 bh->header.info != &stg_CAF_BLACKHOLE_info) {
4071 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4072 debugBelch("Unexpected lazy BHing required at 0x%04x",(int)bh);
4075 /* zero out the slop so that the sanity checker can tell
4076 * where the next closure is.
4079 StgInfoTable *bh_info = get_itbl(bh);
4080 nat np = bh_info->layout.payload.ptrs,
4081 nw = bh_info->layout.payload.nptrs, i;
4082 /* don't zero out slop for a THUNK_SELECTOR,
4083 * because its layout info is used for a
4084 * different purpose, and it's exactly the
4085 * same size as a BLACKHOLE in any case.
4087 if (bh_info->type != THUNK_SELECTOR) {
4088 for (i = 0; i < np + nw; i++) {
4089 ((StgClosure *)bh)->payload[i] = INVALID_OBJECT;
4095 // We pretend that bh is now dead.
4096 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4098 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
4099 SET_INFO(bh,&stg_BLACKHOLE_info);
4101 // We pretend that bh has just been created.
4102 LDV_RECORD_CREATE(bh);
4105 prev_was_update_frame = rtsTrue;
4106 updatee = upd->updatee;
4107 frame += sizeofW(StgUpdateFrame);
4113 prev_was_update_frame = rtsFalse;
4115 // we're not in a gap... check whether this is the end of a gap
4116 // (an update frame can't be the end of a gap).
4117 if (current_gap_size != 0) {
4118 gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
4120 current_gap_size = 0;
4122 frame += stack_frame_sizeW((StgClosure *)frame);
4129 // Now we have a stack with gaps in it, and we have to walk down
4130 // shoving the stack up to fill in the gaps. A diagram might
4134 // | ********* | <- sp
4138 // | stack_gap | <- gap | chunk_size
4140 // | ......... | <- gap_end v
4146 // 'sp' points the the current top-of-stack
4147 // 'gap' points to the stack_gap structure inside the gap
4148 // ***** indicates real stack data
4149 // ..... indicates gap
4150 // <empty> indicates unused
4154 void *gap_start, *next_gap_start, *gap_end;
4157 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4158 sp = next_gap_start;
4160 while ((StgPtr)gap > tso->sp) {
4162 // we're working in *bytes* now...
4163 gap_start = next_gap_start;
4164 gap_end = (void*) ((unsigned char*)gap_start - gap->gap_size * sizeof(W_));
4166 gap = gap->next_gap;
4167 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4169 chunk_size = (unsigned char*)gap_end - (unsigned char*)next_gap_start;
4171 memmove(sp, next_gap_start, chunk_size);
4174 tso->sp = (StgPtr)sp;
4178 /* -----------------------------------------------------------------------------
4181 * We have to prepare for GC - this means doing lazy black holing
4182 * here. We also take the opportunity to do stack squeezing if it's
4184 * -------------------------------------------------------------------------- */
4186 threadPaused(StgTSO *tso)
4188 if ( RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue )
4189 threadSqueezeStack(tso); // does black holing too
4191 threadLazyBlackHole(tso);
4194 /* -----------------------------------------------------------------------------
4196 * -------------------------------------------------------------------------- */
4200 printMutableList(generation *gen)
4205 debugBelch("@@ Mutable list %p: ", gen->mut_list);
4207 for (bd = gen->mut_list; bd != NULL; bd = bd->link) {
4208 for (p = bd->start; p < bd->free; p++) {
4209 debugBelch("%p (%s), ", (void *)*p, info_type((StgClosure *)*p));
4215 STATIC_INLINE rtsBool
4216 maybeLarge(StgClosure *closure)
4218 StgInfoTable *info = get_itbl(closure);
4220 /* closure types that may be found on the new_large_objects list;
4221 see scavenge_large */
4222 return (info->type == MUT_ARR_PTRS ||
4223 info->type == MUT_ARR_PTRS_FROZEN ||
4224 info->type == MUT_ARR_PTRS_FROZEN0 ||
4225 info->type == TSO ||
4226 info->type == ARR_WORDS);