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 ...
1724 return copy(q,sizeofW(StgHeader)+1,stp);
1728 return copy(q,sizeofW(StgThunk)+1,stp);
1733 #ifdef NO_PROMOTE_THUNKS
1734 if (bd->gen_no == 0 &&
1735 bd->step->no != 0 &&
1736 bd->step->no == generations[bd->gen_no].n_steps-1) {
1740 return copy(q,sizeofW(StgThunk)+2,stp);
1748 return copy(q,sizeofW(StgHeader)+2,stp);
1754 case IND_OLDGEN_PERM:
1758 return copy(q,sizeW_fromITBL(info),stp);
1761 return copy(q,bco_sizeW((StgBCO *)q),stp);
1764 case SE_CAF_BLACKHOLE:
1767 return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
1769 case THUNK_SELECTOR:
1773 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
1774 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1777 p = eval_thunk_selector(info->layout.selector_offset,
1781 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1783 // q is still BLACKHOLE'd.
1784 thunk_selector_depth++;
1786 thunk_selector_depth--;
1789 // We store the size of the just evacuated object in the
1790 // LDV word so that the profiler can guess the position of
1791 // the next object later.
1792 SET_EVACUAEE_FOR_LDV(q, THUNK_SELECTOR_sizeW());
1800 // follow chains of indirections, don't evacuate them
1801 q = ((StgInd*)q)->indirectee;
1805 if (info->srt_bitmap != 0 && major_gc &&
1806 *THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
1807 *THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
1808 static_objects = (StgClosure *)q;
1813 if (info->srt_bitmap != 0 && major_gc &&
1814 *FUN_STATIC_LINK((StgClosure *)q) == NULL) {
1815 *FUN_STATIC_LINK((StgClosure *)q) = static_objects;
1816 static_objects = (StgClosure *)q;
1821 /* If q->saved_info != NULL, then it's a revertible CAF - it'll be
1822 * on the CAF list, so don't do anything with it here (we'll
1823 * scavenge it later).
1826 && ((StgIndStatic *)q)->saved_info == NULL
1827 && *IND_STATIC_LINK((StgClosure *)q) == NULL) {
1828 *IND_STATIC_LINK((StgClosure *)q) = static_objects;
1829 static_objects = (StgClosure *)q;
1834 if (major_gc && *STATIC_LINK(info,(StgClosure *)q) == NULL) {
1835 *STATIC_LINK(info,(StgClosure *)q) = static_objects;
1836 static_objects = (StgClosure *)q;
1840 case CONSTR_INTLIKE:
1841 case CONSTR_CHARLIKE:
1842 case CONSTR_NOCAF_STATIC:
1843 /* no need to put these on the static linked list, they don't need
1857 case CATCH_STM_FRAME:
1858 case CATCH_RETRY_FRAME:
1859 case ATOMICALLY_FRAME:
1860 // shouldn't see these
1861 barf("evacuate: stack frame at %p\n", q);
1864 return copy(q,pap_sizeW((StgPAP*)q),stp);
1867 return copy(q,ap_sizeW((StgAP*)q),stp);
1870 return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp);
1873 /* Already evacuated, just return the forwarding address.
1874 * HOWEVER: if the requested destination generation (evac_gen) is
1875 * older than the actual generation (because the object was
1876 * already evacuated to a younger generation) then we have to
1877 * set the failed_to_evac flag to indicate that we couldn't
1878 * manage to promote the object to the desired generation.
1880 if (evac_gen > 0) { // optimisation
1881 StgClosure *p = ((StgEvacuated*)q)->evacuee;
1882 if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < evac_gen) {
1883 failed_to_evac = rtsTrue;
1884 TICK_GC_FAILED_PROMOTION();
1887 return ((StgEvacuated*)q)->evacuee;
1890 // just copy the block
1891 return copy(q,arr_words_sizeW((StgArrWords *)q),stp);
1894 case MUT_ARR_PTRS_FROZEN:
1895 case MUT_ARR_PTRS_FROZEN0:
1896 // just copy the block
1897 return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
1901 StgTSO *tso = (StgTSO *)q;
1903 /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
1905 if (tso->what_next == ThreadRelocated) {
1906 q = (StgClosure *)tso->link;
1910 /* To evacuate a small TSO, we need to relocate the update frame
1917 new_tso = (StgTSO *)copyPart((StgClosure *)tso,
1919 sizeofW(StgTSO), stp);
1920 move_TSO(tso, new_tso);
1921 for (p = tso->sp, q = new_tso->sp;
1922 p < tso->stack+tso->stack_size;) {
1926 return (StgClosure *)new_tso;
1933 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
1934 to = copy(q,BLACKHOLE_sizeW(),stp);
1935 //ToDo: derive size etc from reverted IP
1936 //to = copy(q,size,stp);
1938 debugBelch("@@ evacuate: RBH %p (%s) to %p (%s)",
1939 q, info_type(q), to, info_type(to)));
1944 ASSERT(sizeofW(StgBlockedFetch) >= MIN_NONUPD_SIZE);
1945 to = copy(q,sizeofW(StgBlockedFetch),stp);
1947 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
1948 q, info_type(q), to, info_type(to)));
1955 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1956 to = copy(q,sizeofW(StgFetchMe),stp);
1958 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
1959 q, info_type(q), to, info_type(to)));
1963 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1964 to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
1966 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
1967 q, info_type(q), to, info_type(to)));
1972 return copy(q,sizeofW(StgTRecHeader),stp);
1974 case TVAR_WAIT_QUEUE:
1975 return copy(q,sizeofW(StgTVarWaitQueue),stp);
1978 return copy(q,sizeofW(StgTVar),stp);
1981 return copy(q,sizeofW(StgTRecChunk),stp);
1984 barf("evacuate: strange closure type %d", (int)(info->type));
1990 /* -----------------------------------------------------------------------------
1991 Evaluate a THUNK_SELECTOR if possible.
1993 returns: NULL if we couldn't evaluate this THUNK_SELECTOR, or
1994 a closure pointer if we evaluated it and this is the result. Note
1995 that "evaluating" the THUNK_SELECTOR doesn't necessarily mean
1996 reducing it to HNF, just that we have eliminated the selection.
1997 The result might be another thunk, or even another THUNK_SELECTOR.
1999 If the return value is non-NULL, the original selector thunk has
2000 been BLACKHOLE'd, and should be updated with an indirection or a
2001 forwarding pointer. If the return value is NULL, then the selector
2005 ToDo: the treatment of THUNK_SELECTORS could be improved in the
2006 following way (from a suggestion by Ian Lynagh):
2008 We can have a chain like this:
2012 |-----> sel_0 --> (a,b)
2014 |-----> sel_0 --> ...
2016 and the depth limit means we don't go all the way to the end of the
2017 chain, which results in a space leak. This affects the recursive
2018 call to evacuate() in the THUNK_SELECTOR case in evacuate(): *not*
2019 the recursive call to eval_thunk_selector() in
2020 eval_thunk_selector().
2022 We could eliminate the depth bound in this case, in the following
2025 - traverse the chain once to discover the *value* of the
2026 THUNK_SELECTOR. Mark all THUNK_SELECTORS that we
2027 visit on the way as having been visited already (somehow).
2029 - in a second pass, traverse the chain again updating all
2030 THUNK_SEELCTORS that we find on the way with indirections to
2033 - if we encounter a "marked" THUNK_SELECTOR in a normal
2034 evacuate(), we konw it can't be updated so just evac it.
2036 Program that illustrates the problem:
2039 foo (x:xs) = let (ys, zs) = foo xs
2040 in if x >= 0 then (x:ys, zs) else (ys, x:zs)
2042 main = bar [1..(100000000::Int)]
2043 bar xs = (\(ys, zs) -> print ys >> print zs) (foo xs)
2045 -------------------------------------------------------------------------- */
2047 static inline rtsBool
2048 is_to_space ( StgClosure *p )
2052 bd = Bdescr((StgPtr)p);
2053 if (HEAP_ALLOCED(p) &&
2054 ((bd->flags & BF_EVACUATED)
2055 || ((bd->flags & BF_COMPACTED) &&
2056 is_marked((P_)p,bd)))) {
2064 eval_thunk_selector( nat field, StgSelector * p )
2067 const StgInfoTable *info_ptr;
2068 StgClosure *selectee;
2070 selectee = p->selectee;
2072 // Save the real info pointer (NOTE: not the same as get_itbl()).
2073 info_ptr = p->header.info;
2075 // If the THUNK_SELECTOR is in a generation that we are not
2076 // collecting, then bail out early. We won't be able to save any
2077 // space in any case, and updating with an indirection is trickier
2079 if (Bdescr((StgPtr)p)->gen_no > N) {
2083 // BLACKHOLE the selector thunk, since it is now under evaluation.
2084 // This is important to stop us going into an infinite loop if
2085 // this selector thunk eventually refers to itself.
2086 SET_INFO(p,&stg_BLACKHOLE_info);
2090 // We don't want to end up in to-space, because this causes
2091 // problems when the GC later tries to evacuate the result of
2092 // eval_thunk_selector(). There are various ways this could
2095 // 1. following an IND_STATIC
2097 // 2. when the old generation is compacted, the mark phase updates
2098 // from-space pointers to be to-space pointers, and we can't
2099 // reliably tell which we're following (eg. from an IND_STATIC).
2101 // 3. compacting GC again: if we're looking at a constructor in
2102 // the compacted generation, it might point directly to objects
2103 // in to-space. We must bale out here, otherwise doing the selection
2104 // will result in a to-space pointer being returned.
2106 // (1) is dealt with using a BF_EVACUATED test on the
2107 // selectee. (2) and (3): we can tell if we're looking at an
2108 // object in the compacted generation that might point to
2109 // to-space objects by testing that (a) it is BF_COMPACTED, (b)
2110 // the compacted generation is being collected, and (c) the
2111 // object is marked. Only a marked object may have pointers that
2112 // point to to-space objects, because that happens when
2115 // The to-space test is now embodied in the in_to_space() inline
2116 // function, as it is re-used below.
2118 if (is_to_space(selectee)) {
2122 info = get_itbl(selectee);
2123 switch (info->type) {
2131 case CONSTR_NOCAF_STATIC:
2132 // check that the size is in range
2133 ASSERT(field < (StgWord32)(info->layout.payload.ptrs +
2134 info->layout.payload.nptrs));
2136 // Select the right field from the constructor, and check
2137 // that the result isn't in to-space. It might be in
2138 // to-space if, for example, this constructor contains
2139 // pointers to younger-gen objects (and is on the mut-once
2144 q = selectee->payload[field];
2145 if (is_to_space(q)) {
2155 case IND_OLDGEN_PERM:
2157 selectee = ((StgInd *)selectee)->indirectee;
2161 // We don't follow pointers into to-space; the constructor
2162 // has already been evacuated, so we won't save any space
2163 // leaks by evaluating this selector thunk anyhow.
2166 case THUNK_SELECTOR:
2170 // check that we don't recurse too much, re-using the
2171 // depth bound also used in evacuate().
2172 if (thunk_selector_depth >= MAX_THUNK_SELECTOR_DEPTH) {
2175 thunk_selector_depth++;
2177 val = eval_thunk_selector(info->layout.selector_offset,
2178 (StgSelector *)selectee);
2180 thunk_selector_depth--;
2185 // We evaluated this selector thunk, so update it with
2186 // an indirection. NOTE: we don't use UPD_IND here,
2187 // because we are guaranteed that p is in a generation
2188 // that we are collecting, and we never want to put the
2189 // indirection on a mutable list.
2191 // For the purposes of LDV profiling, we have destroyed
2192 // the original selector thunk.
2193 SET_INFO(p, info_ptr);
2194 LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(selectee);
2196 ((StgInd *)selectee)->indirectee = val;
2197 SET_INFO(selectee,&stg_IND_info);
2199 // For the purposes of LDV profiling, we have created an
2201 LDV_RECORD_CREATE(selectee);
2218 case SE_CAF_BLACKHOLE:
2230 // not evaluated yet
2234 barf("eval_thunk_selector: strange selectee %d",
2239 // We didn't manage to evaluate this thunk; restore the old info pointer
2240 SET_INFO(p, info_ptr);
2244 /* -----------------------------------------------------------------------------
2245 move_TSO is called to update the TSO structure after it has been
2246 moved from one place to another.
2247 -------------------------------------------------------------------------- */
2250 move_TSO (StgTSO *src, StgTSO *dest)
2254 // relocate the stack pointer...
2255 diff = (StgPtr)dest - (StgPtr)src; // In *words*
2256 dest->sp = (StgPtr)dest->sp + diff;
2259 /* Similar to scavenge_large_bitmap(), but we don't write back the
2260 * pointers we get back from evacuate().
2263 scavenge_large_srt_bitmap( StgLargeSRT *large_srt )
2270 bitmap = large_srt->l.bitmap[b];
2271 size = (nat)large_srt->l.size;
2272 p = (StgClosure **)large_srt->srt;
2273 for (i = 0; i < size; ) {
2274 if ((bitmap & 1) != 0) {
2279 if (i % BITS_IN(W_) == 0) {
2281 bitmap = large_srt->l.bitmap[b];
2283 bitmap = bitmap >> 1;
2288 /* evacuate the SRT. If srt_bitmap is zero, then there isn't an
2289 * srt field in the info table. That's ok, because we'll
2290 * never dereference it.
2293 scavenge_srt (StgClosure **srt, nat srt_bitmap)
2298 bitmap = srt_bitmap;
2301 if (bitmap == (StgHalfWord)(-1)) {
2302 scavenge_large_srt_bitmap( (StgLargeSRT *)srt );
2306 while (bitmap != 0) {
2307 if ((bitmap & 1) != 0) {
2308 #ifdef ENABLE_WIN32_DLL_SUPPORT
2309 // Special-case to handle references to closures hiding out in DLLs, since
2310 // double indirections required to get at those. The code generator knows
2311 // which is which when generating the SRT, so it stores the (indirect)
2312 // reference to the DLL closure in the table by first adding one to it.
2313 // We check for this here, and undo the addition before evacuating it.
2315 // If the SRT entry hasn't got bit 0 set, the SRT entry points to a
2316 // closure that's fixed at link-time, and no extra magic is required.
2317 if ( (unsigned long)(*srt) & 0x1 ) {
2318 evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
2327 bitmap = bitmap >> 1;
2333 scavenge_thunk_srt(const StgInfoTable *info)
2335 StgThunkInfoTable *thunk_info;
2337 thunk_info = itbl_to_thunk_itbl(info);
2338 scavenge_srt((StgClosure **)GET_SRT(thunk_info), thunk_info->i.srt_bitmap);
2342 scavenge_fun_srt(const StgInfoTable *info)
2344 StgFunInfoTable *fun_info;
2346 fun_info = itbl_to_fun_itbl(info);
2347 scavenge_srt((StgClosure **)GET_FUN_SRT(fun_info), fun_info->i.srt_bitmap);
2350 /* -----------------------------------------------------------------------------
2352 -------------------------------------------------------------------------- */
2355 scavengeTSO (StgTSO *tso)
2357 // chase the link field for any TSOs on the same queue
2358 tso->link = (StgTSO *)evacuate((StgClosure *)tso->link);
2359 if ( tso->why_blocked == BlockedOnMVar
2360 || tso->why_blocked == BlockedOnBlackHole
2361 || tso->why_blocked == BlockedOnException
2363 || tso->why_blocked == BlockedOnGA
2364 || tso->why_blocked == BlockedOnGA_NoSend
2367 tso->block_info.closure = evacuate(tso->block_info.closure);
2369 if ( tso->blocked_exceptions != NULL ) {
2370 tso->blocked_exceptions =
2371 (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
2374 // scavange current transaction record
2375 tso->trec = (StgTRecHeader *)evacuate((StgClosure *)tso->trec);
2377 // scavenge this thread's stack
2378 scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
2381 /* -----------------------------------------------------------------------------
2382 Blocks of function args occur on the stack (at the top) and
2384 -------------------------------------------------------------------------- */
2386 STATIC_INLINE StgPtr
2387 scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
2394 switch (fun_info->f.fun_type) {
2396 bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
2397 size = BITMAP_SIZE(fun_info->f.b.bitmap);
2400 size = GET_FUN_LARGE_BITMAP(fun_info)->size;
2401 scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
2405 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2406 size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->f.fun_type]);
2409 if ((bitmap & 1) == 0) {
2410 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2413 bitmap = bitmap >> 1;
2421 STATIC_INLINE StgPtr
2422 scavenge_PAP_payload (StgClosure *fun, StgClosure **payload, StgWord size)
2426 StgFunInfoTable *fun_info;
2428 fun_info = get_fun_itbl(fun);
2429 ASSERT(fun_info->i.type != PAP);
2430 p = (StgPtr)payload;
2432 switch (fun_info->f.fun_type) {
2434 bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
2437 scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
2441 scavenge_large_bitmap((StgPtr)payload, BCO_BITMAP(fun), size);
2445 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2448 if ((bitmap & 1) == 0) {
2449 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2452 bitmap = bitmap >> 1;
2460 STATIC_INLINE StgPtr
2461 scavenge_PAP (StgPAP *pap)
2463 pap->fun = evacuate(pap->fun);
2464 return scavenge_PAP_payload (pap->fun, pap->payload, pap->n_args);
2467 STATIC_INLINE StgPtr
2468 scavenge_AP (StgAP *ap)
2470 ap->fun = evacuate(ap->fun);
2471 return scavenge_PAP_payload (ap->fun, ap->payload, ap->n_args);
2474 /* -----------------------------------------------------------------------------
2475 Scavenge a given step until there are no more objects in this step
2478 evac_gen is set by the caller to be either zero (for a step in a
2479 generation < N) or G where G is the generation of the step being
2482 We sometimes temporarily change evac_gen back to zero if we're
2483 scavenging a mutable object where early promotion isn't such a good
2485 -------------------------------------------------------------------------- */
2493 nat saved_evac_gen = evac_gen;
2498 failed_to_evac = rtsFalse;
2500 /* scavenge phase - standard breadth-first scavenging of the
2504 while (bd != stp->hp_bd || p < stp->hp) {
2506 // If we're at the end of this block, move on to the next block
2507 if (bd != stp->hp_bd && p == bd->free) {
2513 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2514 info = get_itbl((StgClosure *)p);
2516 ASSERT(thunk_selector_depth == 0);
2519 switch (info->type) {
2523 StgMVar *mvar = ((StgMVar *)p);
2525 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
2526 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
2527 mvar->value = evacuate((StgClosure *)mvar->value);
2528 evac_gen = saved_evac_gen;
2529 failed_to_evac = rtsTrue; // mutable.
2530 p += sizeofW(StgMVar);
2535 scavenge_fun_srt(info);
2536 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2537 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2538 p += sizeofW(StgHeader) + 2;
2542 scavenge_thunk_srt(info);
2543 ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
2544 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2545 p += sizeofW(StgThunk) + 2;
2549 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2550 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2551 p += sizeofW(StgHeader) + 2;
2555 scavenge_thunk_srt(info);
2556 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2557 p += sizeofW(StgThunk) + 1;
2561 scavenge_fun_srt(info);
2563 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2564 p += sizeofW(StgHeader) + 1;
2568 scavenge_thunk_srt(info);
2569 p += sizeofW(StgThunk) + 1;
2573 scavenge_fun_srt(info);
2575 p += sizeofW(StgHeader) + 1;
2579 scavenge_thunk_srt(info);
2580 p += sizeofW(StgThunk) + 2;
2584 scavenge_fun_srt(info);
2586 p += sizeofW(StgHeader) + 2;
2590 scavenge_thunk_srt(info);
2591 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2592 p += sizeofW(StgThunk) + 2;
2596 scavenge_fun_srt(info);
2598 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2599 p += sizeofW(StgHeader) + 2;
2603 scavenge_fun_srt(info);
2610 scavenge_thunk_srt(info);
2611 end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
2612 for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
2613 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2615 p += info->layout.payload.nptrs;
2627 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2628 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2629 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2631 p += info->layout.payload.nptrs;
2636 StgBCO *bco = (StgBCO *)p;
2637 bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
2638 bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
2639 bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
2640 bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
2641 p += bco_sizeW(bco);
2646 if (stp->gen->no != 0) {
2649 // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an
2650 // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
2651 LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
2654 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
2656 SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
2658 // We pretend that p has just been created.
2659 LDV_RECORD_CREATE((StgClosure *)p);
2662 case IND_OLDGEN_PERM:
2663 ((StgInd *)p)->indirectee = evacuate(((StgInd *)p)->indirectee);
2664 p += sizeofW(StgInd);
2669 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2670 evac_gen = saved_evac_gen;
2671 failed_to_evac = rtsTrue; // mutable anyhow
2672 p += sizeofW(StgMutVar);
2676 case SE_CAF_BLACKHOLE:
2679 p += BLACKHOLE_sizeW();
2682 case THUNK_SELECTOR:
2684 StgSelector *s = (StgSelector *)p;
2685 s->selectee = evacuate(s->selectee);
2686 p += THUNK_SELECTOR_sizeW();
2690 // A chunk of stack saved in a heap object
2693 StgAP_STACK *ap = (StgAP_STACK *)p;
2695 ap->fun = evacuate(ap->fun);
2696 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2697 p = (StgPtr)ap->payload + ap->size;
2702 p = scavenge_PAP((StgPAP *)p);
2706 p = scavenge_AP((StgAP *)p);
2710 // nothing to follow
2711 p += arr_words_sizeW((StgArrWords *)p);
2715 // follow everything
2719 evac_gen = 0; // repeatedly mutable
2720 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2721 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2722 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2724 evac_gen = saved_evac_gen;
2725 failed_to_evac = rtsTrue; // mutable anyhow.
2729 case MUT_ARR_PTRS_FROZEN:
2730 case MUT_ARR_PTRS_FROZEN0:
2731 // follow everything
2735 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2736 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2737 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2739 // it's tempting to recordMutable() if failed_to_evac is
2740 // false, but that breaks some assumptions (eg. every
2741 // closure on the mutable list is supposed to have the MUT
2742 // flag set, and MUT_ARR_PTRS_FROZEN doesn't).
2748 StgTSO *tso = (StgTSO *)p;
2751 evac_gen = saved_evac_gen;
2752 failed_to_evac = rtsTrue; // mutable anyhow.
2753 p += tso_sizeW(tso);
2761 nat size, ptrs, nonptrs, vhs;
2763 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2765 StgRBH *rbh = (StgRBH *)p;
2766 (StgClosure *)rbh->blocking_queue =
2767 evacuate((StgClosure *)rbh->blocking_queue);
2768 failed_to_evac = rtsTrue; // mutable anyhow.
2770 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2771 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2772 // ToDo: use size of reverted closure here!
2773 p += BLACKHOLE_sizeW();
2779 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2780 // follow the pointer to the node which is being demanded
2781 (StgClosure *)bf->node =
2782 evacuate((StgClosure *)bf->node);
2783 // follow the link to the rest of the blocking queue
2784 (StgClosure *)bf->link =
2785 evacuate((StgClosure *)bf->link);
2787 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
2788 bf, info_type((StgClosure *)bf),
2789 bf->node, info_type(bf->node)));
2790 p += sizeofW(StgBlockedFetch);
2798 p += sizeofW(StgFetchMe);
2799 break; // nothing to do in this case
2803 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
2804 (StgClosure *)fmbq->blocking_queue =
2805 evacuate((StgClosure *)fmbq->blocking_queue);
2807 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
2808 p, info_type((StgClosure *)p)));
2809 p += sizeofW(StgFetchMeBlockingQueue);
2814 case TVAR_WAIT_QUEUE:
2816 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
2818 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
2819 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
2820 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
2821 evac_gen = saved_evac_gen;
2822 failed_to_evac = rtsTrue; // mutable
2823 p += sizeofW(StgTVarWaitQueue);
2829 StgTVar *tvar = ((StgTVar *) p);
2831 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
2832 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
2833 evac_gen = saved_evac_gen;
2834 failed_to_evac = rtsTrue; // mutable
2835 p += sizeofW(StgTVar);
2841 StgTRecHeader *trec = ((StgTRecHeader *) p);
2843 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
2844 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
2845 evac_gen = saved_evac_gen;
2846 failed_to_evac = rtsTrue; // mutable
2847 p += sizeofW(StgTRecHeader);
2854 StgTRecChunk *tc = ((StgTRecChunk *) p);
2855 TRecEntry *e = &(tc -> entries[0]);
2857 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
2858 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
2859 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
2860 e->expected_value = evacuate((StgClosure*)e->expected_value);
2861 e->new_value = evacuate((StgClosure*)e->new_value);
2863 evac_gen = saved_evac_gen;
2864 failed_to_evac = rtsTrue; // mutable
2865 p += sizeofW(StgTRecChunk);
2870 barf("scavenge: unimplemented/strange closure type %d @ %p",
2875 * We need to record the current object on the mutable list if
2876 * (a) It is actually mutable, or
2877 * (b) It contains pointers to a younger generation.
2878 * Case (b) arises if we didn't manage to promote everything that
2879 * the current object points to into the current generation.
2881 if (failed_to_evac) {
2882 failed_to_evac = rtsFalse;
2883 recordMutableGen((StgClosure *)q, stp->gen);
2891 /* -----------------------------------------------------------------------------
2892 Scavenge everything on the mark stack.
2894 This is slightly different from scavenge():
2895 - we don't walk linearly through the objects, so the scavenger
2896 doesn't need to advance the pointer on to the next object.
2897 -------------------------------------------------------------------------- */
2900 scavenge_mark_stack(void)
2906 evac_gen = oldest_gen->no;
2907 saved_evac_gen = evac_gen;
2910 while (!mark_stack_empty()) {
2911 p = pop_mark_stack();
2913 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2914 info = get_itbl((StgClosure *)p);
2917 switch (info->type) {
2921 StgMVar *mvar = ((StgMVar *)p);
2923 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
2924 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
2925 mvar->value = evacuate((StgClosure *)mvar->value);
2926 evac_gen = saved_evac_gen;
2927 failed_to_evac = rtsTrue; // mutable.
2932 scavenge_fun_srt(info);
2933 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2934 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2938 scavenge_thunk_srt(info);
2939 ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
2940 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2944 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2945 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2950 scavenge_fun_srt(info);
2951 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2956 scavenge_thunk_srt(info);
2957 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2962 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2967 scavenge_fun_srt(info);
2972 scavenge_thunk_srt(info);
2980 scavenge_fun_srt(info);
2987 scavenge_thunk_srt(info);
2988 end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
2989 for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
2990 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3003 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3004 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
3005 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3011 StgBCO *bco = (StgBCO *)p;
3012 bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
3013 bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
3014 bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
3015 bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
3020 // don't need to do anything here: the only possible case
3021 // is that we're in a 1-space compacting collector, with
3022 // no "old" generation.
3026 case IND_OLDGEN_PERM:
3027 ((StgInd *)p)->indirectee =
3028 evacuate(((StgInd *)p)->indirectee);
3033 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3034 evac_gen = saved_evac_gen;
3035 failed_to_evac = rtsTrue;
3039 case SE_CAF_BLACKHOLE:
3045 case THUNK_SELECTOR:
3047 StgSelector *s = (StgSelector *)p;
3048 s->selectee = evacuate(s->selectee);
3052 // A chunk of stack saved in a heap object
3055 StgAP_STACK *ap = (StgAP_STACK *)p;
3057 ap->fun = evacuate(ap->fun);
3058 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3063 scavenge_PAP((StgPAP *)p);
3067 scavenge_AP((StgAP *)p);
3071 // follow everything
3075 evac_gen = 0; // repeatedly mutable
3076 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3077 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3078 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3080 evac_gen = saved_evac_gen;
3081 failed_to_evac = rtsTrue; // mutable anyhow.
3085 case MUT_ARR_PTRS_FROZEN:
3086 case MUT_ARR_PTRS_FROZEN0:
3087 // follow everything
3091 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3092 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3093 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3100 StgTSO *tso = (StgTSO *)p;
3103 evac_gen = saved_evac_gen;
3104 failed_to_evac = rtsTrue;
3112 nat size, ptrs, nonptrs, vhs;
3114 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3116 StgRBH *rbh = (StgRBH *)p;
3117 bh->blocking_queue =
3118 (StgTSO *)evacuate((StgClosure *)bh->blocking_queue);
3119 failed_to_evac = rtsTrue; // mutable anyhow.
3121 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3122 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3128 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3129 // follow the pointer to the node which is being demanded
3130 (StgClosure *)bf->node =
3131 evacuate((StgClosure *)bf->node);
3132 // follow the link to the rest of the blocking queue
3133 (StgClosure *)bf->link =
3134 evacuate((StgClosure *)bf->link);
3136 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3137 bf, info_type((StgClosure *)bf),
3138 bf->node, info_type(bf->node)));
3146 break; // nothing to do in this case
3150 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3151 (StgClosure *)fmbq->blocking_queue =
3152 evacuate((StgClosure *)fmbq->blocking_queue);
3154 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3155 p, info_type((StgClosure *)p)));
3160 case TVAR_WAIT_QUEUE:
3162 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3164 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3165 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3166 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3167 evac_gen = saved_evac_gen;
3168 failed_to_evac = rtsTrue; // mutable
3174 StgTVar *tvar = ((StgTVar *) p);
3176 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3177 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3178 evac_gen = saved_evac_gen;
3179 failed_to_evac = rtsTrue; // mutable
3186 StgTRecChunk *tc = ((StgTRecChunk *) p);
3187 TRecEntry *e = &(tc -> entries[0]);
3189 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3190 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3191 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3192 e->expected_value = evacuate((StgClosure*)e->expected_value);
3193 e->new_value = evacuate((StgClosure*)e->new_value);
3195 evac_gen = saved_evac_gen;
3196 failed_to_evac = rtsTrue; // mutable
3202 StgTRecHeader *trec = ((StgTRecHeader *) p);
3204 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3205 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3206 evac_gen = saved_evac_gen;
3207 failed_to_evac = rtsTrue; // mutable
3212 barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p",
3216 if (failed_to_evac) {
3217 failed_to_evac = rtsFalse;
3218 recordMutableGen((StgClosure *)q, &generations[evac_gen]);
3221 // mark the next bit to indicate "scavenged"
3222 mark(q+1, Bdescr(q));
3224 } // while (!mark_stack_empty())
3226 // start a new linear scan if the mark stack overflowed at some point
3227 if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
3228 IF_DEBUG(gc, debugBelch("scavenge_mark_stack: starting linear scan"));
3229 mark_stack_overflowed = rtsFalse;
3230 oldgen_scan_bd = oldest_gen->steps[0].blocks;
3231 oldgen_scan = oldgen_scan_bd->start;
3234 if (oldgen_scan_bd) {
3235 // push a new thing on the mark stack
3237 // find a closure that is marked but not scavenged, and start
3239 while (oldgen_scan < oldgen_scan_bd->free
3240 && !is_marked(oldgen_scan,oldgen_scan_bd)) {
3244 if (oldgen_scan < oldgen_scan_bd->free) {
3246 // already scavenged?
3247 if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
3248 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3251 push_mark_stack(oldgen_scan);
3252 // ToDo: bump the linear scan by the actual size of the object
3253 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3257 oldgen_scan_bd = oldgen_scan_bd->link;
3258 if (oldgen_scan_bd != NULL) {
3259 oldgen_scan = oldgen_scan_bd->start;
3265 /* -----------------------------------------------------------------------------
3266 Scavenge one object.
3268 This is used for objects that are temporarily marked as mutable
3269 because they contain old-to-new generation pointers. Only certain
3270 objects can have this property.
3271 -------------------------------------------------------------------------- */
3274 scavenge_one(StgPtr p)
3276 const StgInfoTable *info;
3277 nat saved_evac_gen = evac_gen;
3280 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3281 info = get_itbl((StgClosure *)p);
3283 switch (info->type) {
3287 StgMVar *mvar = ((StgMVar *)p);
3289 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
3290 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
3291 mvar->value = evacuate((StgClosure *)mvar->value);
3292 evac_gen = saved_evac_gen;
3293 failed_to_evac = rtsTrue; // mutable.
3306 end = (StgPtr)((StgThunk *)p)->payload + info->layout.payload.ptrs;
3307 for (q = (StgPtr)((StgThunk *)p)->payload; q < end; q++) {
3308 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3314 case FUN_1_0: // hardly worth specialising these guys
3331 end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3332 for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
3333 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3340 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3341 evac_gen = saved_evac_gen;
3342 failed_to_evac = rtsTrue; // mutable anyhow
3346 case SE_CAF_BLACKHOLE:
3351 case THUNK_SELECTOR:
3353 StgSelector *s = (StgSelector *)p;
3354 s->selectee = evacuate(s->selectee);
3360 StgAP_STACK *ap = (StgAP_STACK *)p;
3362 ap->fun = evacuate(ap->fun);
3363 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3364 p = (StgPtr)ap->payload + ap->size;
3369 p = scavenge_AP((StgAP *)p);
3373 p = scavenge_PAP((StgPAP *)p);
3377 // nothing to follow
3382 // follow everything
3385 evac_gen = 0; // repeatedly mutable
3386 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3387 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3388 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3390 evac_gen = saved_evac_gen;
3391 failed_to_evac = rtsTrue;
3395 case MUT_ARR_PTRS_FROZEN:
3396 case MUT_ARR_PTRS_FROZEN0:
3398 // follow everything
3401 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3402 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3403 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3410 StgTSO *tso = (StgTSO *)p;
3412 evac_gen = 0; // repeatedly mutable
3414 evac_gen = saved_evac_gen;
3415 failed_to_evac = rtsTrue;
3423 nat size, ptrs, nonptrs, vhs;
3425 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3427 StgRBH *rbh = (StgRBH *)p;
3428 (StgClosure *)rbh->blocking_queue =
3429 evacuate((StgClosure *)rbh->blocking_queue);
3430 failed_to_evac = rtsTrue; // mutable anyhow.
3432 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3433 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3434 // ToDo: use size of reverted closure here!
3440 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3441 // follow the pointer to the node which is being demanded
3442 (StgClosure *)bf->node =
3443 evacuate((StgClosure *)bf->node);
3444 // follow the link to the rest of the blocking queue
3445 (StgClosure *)bf->link =
3446 evacuate((StgClosure *)bf->link);
3448 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3449 bf, info_type((StgClosure *)bf),
3450 bf->node, info_type(bf->node)));
3458 break; // nothing to do in this case
3462 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3463 (StgClosure *)fmbq->blocking_queue =
3464 evacuate((StgClosure *)fmbq->blocking_queue);
3466 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3467 p, info_type((StgClosure *)p)));
3472 case TVAR_WAIT_QUEUE:
3474 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3476 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3477 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3478 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3479 evac_gen = saved_evac_gen;
3480 failed_to_evac = rtsTrue; // mutable
3486 StgTVar *tvar = ((StgTVar *) p);
3488 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3489 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3490 evac_gen = saved_evac_gen;
3491 failed_to_evac = rtsTrue; // mutable
3497 StgTRecHeader *trec = ((StgTRecHeader *) p);
3499 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3500 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3501 evac_gen = saved_evac_gen;
3502 failed_to_evac = rtsTrue; // mutable
3509 StgTRecChunk *tc = ((StgTRecChunk *) p);
3510 TRecEntry *e = &(tc -> entries[0]);
3512 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3513 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3514 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3515 e->expected_value = evacuate((StgClosure*)e->expected_value);
3516 e->new_value = evacuate((StgClosure*)e->new_value);
3518 evac_gen = saved_evac_gen;
3519 failed_to_evac = rtsTrue; // mutable
3524 case IND_OLDGEN_PERM:
3527 /* Careful here: a THUNK can be on the mutable list because
3528 * it contains pointers to young gen objects. If such a thunk
3529 * is updated, the IND_OLDGEN will be added to the mutable
3530 * list again, and we'll scavenge it twice. evacuate()
3531 * doesn't check whether the object has already been
3532 * evacuated, so we perform that check here.
3534 StgClosure *q = ((StgInd *)p)->indirectee;
3535 if (HEAP_ALLOCED(q) && Bdescr((StgPtr)q)->flags & BF_EVACUATED) {
3538 ((StgInd *)p)->indirectee = evacuate(q);
3541 #if 0 && defined(DEBUG)
3542 if (RtsFlags.DebugFlags.gc)
3543 /* Debugging code to print out the size of the thing we just
3547 StgPtr start = gen->steps[0].scan;
3548 bdescr *start_bd = gen->steps[0].scan_bd;
3550 scavenge(&gen->steps[0]);
3551 if (start_bd != gen->steps[0].scan_bd) {
3552 size += (P_)BLOCK_ROUND_UP(start) - start;
3553 start_bd = start_bd->link;
3554 while (start_bd != gen->steps[0].scan_bd) {
3555 size += BLOCK_SIZE_W;
3556 start_bd = start_bd->link;
3558 size += gen->steps[0].scan -
3559 (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
3561 size = gen->steps[0].scan - start;
3563 debugBelch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
3569 barf("scavenge_one: strange object %d", (int)(info->type));
3572 no_luck = failed_to_evac;
3573 failed_to_evac = rtsFalse;
3577 /* -----------------------------------------------------------------------------
3578 Scavenging mutable lists.
3580 We treat the mutable list of each generation > N (i.e. all the
3581 generations older than the one being collected) as roots. We also
3582 remove non-mutable objects from the mutable list at this point.
3583 -------------------------------------------------------------------------- */
3586 scavenge_mutable_list(generation *gen)
3591 bd = gen->saved_mut_list;
3594 for (; bd != NULL; bd = bd->link) {
3595 for (q = bd->start; q < bd->free; q++) {
3597 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3598 if (scavenge_one(p)) {
3599 /* didn't manage to promote everything, so put the
3600 * object back on the list.
3602 recordMutableGen((StgClosure *)p,gen);
3607 // free the old mut_list
3608 freeChain(gen->saved_mut_list);
3609 gen->saved_mut_list = NULL;
3614 scavenge_static(void)
3616 StgClosure* p = static_objects;
3617 const StgInfoTable *info;
3619 /* Always evacuate straight to the oldest generation for static
3621 evac_gen = oldest_gen->no;
3623 /* keep going until we've scavenged all the objects on the linked
3625 while (p != END_OF_STATIC_LIST) {
3627 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3630 if (info->type==RBH)
3631 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3633 // make sure the info pointer is into text space
3635 /* Take this object *off* the static_objects list,
3636 * and put it on the scavenged_static_objects list.
3638 static_objects = *STATIC_LINK(info,p);
3639 *STATIC_LINK(info,p) = scavenged_static_objects;
3640 scavenged_static_objects = p;
3642 switch (info -> type) {
3646 StgInd *ind = (StgInd *)p;
3647 ind->indirectee = evacuate(ind->indirectee);
3649 /* might fail to evacuate it, in which case we have to pop it
3650 * back on the mutable list of the oldest generation. We
3651 * leave it *on* the scavenged_static_objects list, though,
3652 * in case we visit this object again.
3654 if (failed_to_evac) {
3655 failed_to_evac = rtsFalse;
3656 recordMutableGen((StgClosure *)p,oldest_gen);
3662 scavenge_thunk_srt(info);
3666 scavenge_fun_srt(info);
3673 next = (P_)p->payload + info->layout.payload.ptrs;
3674 // evacuate the pointers
3675 for (q = (P_)p->payload; q < next; q++) {
3676 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3682 barf("scavenge_static: strange closure %d", (int)(info->type));
3685 ASSERT(failed_to_evac == rtsFalse);
3687 /* get the next static object from the list. Remember, there might
3688 * be more stuff on this list now that we've done some evacuating!
3689 * (static_objects is a global)
3695 /* -----------------------------------------------------------------------------
3696 scavenge a chunk of memory described by a bitmap
3697 -------------------------------------------------------------------------- */
3700 scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
3706 bitmap = large_bitmap->bitmap[b];
3707 for (i = 0; i < size; ) {
3708 if ((bitmap & 1) == 0) {
3709 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3713 if (i % BITS_IN(W_) == 0) {
3715 bitmap = large_bitmap->bitmap[b];
3717 bitmap = bitmap >> 1;
3722 STATIC_INLINE StgPtr
3723 scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap)
3726 if ((bitmap & 1) == 0) {
3727 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3730 bitmap = bitmap >> 1;
3736 /* -----------------------------------------------------------------------------
3737 scavenge_stack walks over a section of stack and evacuates all the
3738 objects pointed to by it. We can use the same code for walking
3739 AP_STACK_UPDs, since these are just sections of copied stack.
3740 -------------------------------------------------------------------------- */
3744 scavenge_stack(StgPtr p, StgPtr stack_end)
3746 const StgRetInfoTable* info;
3750 //IF_DEBUG(sanity, debugBelch(" scavenging stack between %p and %p", p, stack_end));
3753 * Each time around this loop, we are looking at a chunk of stack
3754 * that starts with an activation record.
3757 while (p < stack_end) {
3758 info = get_ret_itbl((StgClosure *)p);
3760 switch (info->i.type) {
3763 ((StgUpdateFrame *)p)->updatee
3764 = evacuate(((StgUpdateFrame *)p)->updatee);
3765 p += sizeofW(StgUpdateFrame);
3768 // small bitmap (< 32 entries, or 64 on a 64-bit machine)
3769 case CATCH_STM_FRAME:
3770 case CATCH_RETRY_FRAME:
3771 case ATOMICALLY_FRAME:
3776 bitmap = BITMAP_BITS(info->i.layout.bitmap);
3777 size = BITMAP_SIZE(info->i.layout.bitmap);
3778 // NOTE: the payload starts immediately after the info-ptr, we
3779 // don't have an StgHeader in the same sense as a heap closure.
3781 p = scavenge_small_bitmap(p, size, bitmap);
3784 scavenge_srt((StgClosure **)GET_SRT(info), info->i.srt_bitmap);
3792 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3795 size = BCO_BITMAP_SIZE(bco);
3796 scavenge_large_bitmap(p, BCO_BITMAP(bco), size);
3801 // large bitmap (> 32 entries, or > 64 on a 64-bit machine)
3807 size = GET_LARGE_BITMAP(&info->i)->size;
3809 scavenge_large_bitmap(p, GET_LARGE_BITMAP(&info->i), size);
3811 // and don't forget to follow the SRT
3815 // Dynamic bitmap: the mask is stored on the stack, and
3816 // there are a number of non-pointers followed by a number
3817 // of pointers above the bitmapped area. (see StgMacros.h,
3822 dyn = ((StgRetDyn *)p)->liveness;
3824 // traverse the bitmap first
3825 bitmap = RET_DYN_LIVENESS(dyn);
3826 p = (P_)&((StgRetDyn *)p)->payload[0];
3827 size = RET_DYN_BITMAP_SIZE;
3828 p = scavenge_small_bitmap(p, size, bitmap);
3830 // skip over the non-ptr words
3831 p += RET_DYN_NONPTRS(dyn) + RET_DYN_NONPTR_REGS_SIZE;
3833 // follow the ptr words
3834 for (size = RET_DYN_PTRS(dyn); size > 0; size--) {
3835 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3843 StgRetFun *ret_fun = (StgRetFun *)p;
3844 StgFunInfoTable *fun_info;
3846 ret_fun->fun = evacuate(ret_fun->fun);
3847 fun_info = get_fun_itbl(ret_fun->fun);
3848 p = scavenge_arg_block(fun_info, ret_fun->payload);
3853 barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->i.type));
3858 /*-----------------------------------------------------------------------------
3859 scavenge the large object list.
3861 evac_gen set by caller; similar games played with evac_gen as with
3862 scavenge() - see comment at the top of scavenge(). Most large
3863 objects are (repeatedly) mutable, so most of the time evac_gen will
3865 --------------------------------------------------------------------------- */
3868 scavenge_large(step *stp)
3873 bd = stp->new_large_objects;
3875 for (; bd != NULL; bd = stp->new_large_objects) {
3877 /* take this object *off* the large objects list and put it on
3878 * the scavenged large objects list. This is so that we can
3879 * treat new_large_objects as a stack and push new objects on
3880 * the front when evacuating.
3882 stp->new_large_objects = bd->link;
3883 dbl_link_onto(bd, &stp->scavenged_large_objects);
3885 // update the block count in this step.
3886 stp->n_scavenged_large_blocks += bd->blocks;
3889 if (scavenge_one(p)) {
3890 recordMutableGen((StgClosure *)p, stp->gen);
3895 /* -----------------------------------------------------------------------------
3896 Initialising the static object & mutable lists
3897 -------------------------------------------------------------------------- */
3900 zero_static_object_list(StgClosure* first_static)
3904 const StgInfoTable *info;
3906 for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
3908 link = *STATIC_LINK(info, p);
3909 *STATIC_LINK(info,p) = NULL;
3913 /* -----------------------------------------------------------------------------
3915 -------------------------------------------------------------------------- */
3922 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
3923 c = (StgIndStatic *)c->static_link)
3925 SET_INFO(c, c->saved_info);
3926 c->saved_info = NULL;
3927 // could, but not necessary: c->static_link = NULL;
3929 revertible_caf_list = NULL;
3933 markCAFs( evac_fn evac )
3937 for (c = (StgIndStatic *)caf_list; c != NULL;
3938 c = (StgIndStatic *)c->static_link)
3940 evac(&c->indirectee);
3942 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
3943 c = (StgIndStatic *)c->static_link)
3945 evac(&c->indirectee);
3949 /* -----------------------------------------------------------------------------
3950 Sanity code for CAF garbage collection.
3952 With DEBUG turned on, we manage a CAF list in addition to the SRT
3953 mechanism. After GC, we run down the CAF list and blackhole any
3954 CAFs which have been garbage collected. This means we get an error
3955 whenever the program tries to enter a garbage collected CAF.
3957 Any garbage collected CAFs are taken off the CAF list at the same
3959 -------------------------------------------------------------------------- */
3961 #if 0 && defined(DEBUG)
3968 const StgInfoTable *info;
3979 ASSERT(info->type == IND_STATIC);
3981 if (STATIC_LINK(info,p) == NULL) {
3982 IF_DEBUG(gccafs, debugBelch("CAF gc'd at 0x%04lx", (long)p));
3984 SET_INFO(p,&stg_BLACKHOLE_info);
3985 p = STATIC_LINK2(info,p);
3989 pp = &STATIC_LINK2(info,p);
3996 // debugBelch("%d CAFs live", i);
4001 /* -----------------------------------------------------------------------------
4004 Whenever a thread returns to the scheduler after possibly doing
4005 some work, we have to run down the stack and black-hole all the
4006 closures referred to by update frames.
4007 -------------------------------------------------------------------------- */
4010 threadLazyBlackHole(StgTSO *tso)
4013 StgRetInfoTable *info;
4017 stack_end = &tso->stack[tso->stack_size];
4019 frame = (StgClosure *)tso->sp;
4022 info = get_ret_itbl(frame);
4024 switch (info->i.type) {
4027 bh = ((StgUpdateFrame *)frame)->updatee;
4029 /* if the thunk is already blackholed, it means we've also
4030 * already blackholed the rest of the thunks on this stack,
4031 * so we can stop early.
4033 * The blackhole made for a CAF is a CAF_BLACKHOLE, so they
4034 * don't interfere with this optimisation.
4036 if (bh->header.info == &stg_BLACKHOLE_info) {
4040 if (bh->header.info != &stg_CAF_BLACKHOLE_info) {
4041 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4042 debugBelch("Unexpected lazy BHing required at 0x%04x\n",(int)bh);
4046 // We pretend that bh is now dead.
4047 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4049 SET_INFO(bh,&stg_BLACKHOLE_info);
4051 // We pretend that bh has just been created.
4052 LDV_RECORD_CREATE(bh);
4055 frame = (StgClosure *) ((StgUpdateFrame *)frame + 1);
4061 // normal stack frames; do nothing except advance the pointer
4063 frame = (StgClosure *)((StgPtr)frame + stack_frame_sizeW(frame));
4069 /* -----------------------------------------------------------------------------
4072 * Code largely pinched from old RTS, then hacked to bits. We also do
4073 * lazy black holing here.
4075 * -------------------------------------------------------------------------- */
4077 struct stack_gap { StgWord gap_size; struct stack_gap *next_gap; };
4080 threadSqueezeStack(StgTSO *tso)
4083 rtsBool prev_was_update_frame;
4084 StgClosure *updatee = NULL;
4086 StgRetInfoTable *info;
4087 StgWord current_gap_size;
4088 struct stack_gap *gap;
4091 // Traverse the stack upwards, replacing adjacent update frames
4092 // with a single update frame and a "stack gap". A stack gap
4093 // contains two values: the size of the gap, and the distance
4094 // to the next gap (or the stack top).
4096 bottom = &(tso->stack[tso->stack_size]);
4100 ASSERT(frame < bottom);
4102 prev_was_update_frame = rtsFalse;
4103 current_gap_size = 0;
4104 gap = (struct stack_gap *) (tso->sp - sizeofW(StgUpdateFrame));
4106 while (frame < bottom) {
4108 info = get_ret_itbl((StgClosure *)frame);
4109 switch (info->i.type) {
4113 StgUpdateFrame *upd = (StgUpdateFrame *)frame;
4115 if (upd->updatee->header.info == &stg_BLACKHOLE_info) {
4117 // found a BLACKHOLE'd update frame; we've been here
4118 // before, in a previous GC, so just break out.
4120 // Mark the end of the gap, if we're in one.
4121 if (current_gap_size != 0) {
4122 gap = (struct stack_gap *)(frame-sizeofW(StgUpdateFrame));
4125 frame += sizeofW(StgUpdateFrame);
4126 goto done_traversing;
4129 if (prev_was_update_frame) {
4131 TICK_UPD_SQUEEZED();
4132 /* wasn't there something about update squeezing and ticky to be
4133 * sorted out? oh yes: we aren't counting each enter properly
4134 * in this case. See the log somewhere. KSW 1999-04-21
4136 * Check two things: that the two update frames don't point to
4137 * the same object, and that the updatee_bypass isn't already an
4138 * indirection. Both of these cases only happen when we're in a
4139 * block hole-style loop (and there are multiple update frames
4140 * on the stack pointing to the same closure), but they can both
4141 * screw us up if we don't check.
4143 if (upd->updatee != updatee && !closure_IND(upd->updatee)) {
4144 UPD_IND_NOLOCK(upd->updatee, updatee);
4147 // now mark this update frame as a stack gap. The gap
4148 // marker resides in the bottom-most update frame of
4149 // the series of adjacent frames, and covers all the
4150 // frames in this series.
4151 current_gap_size += sizeofW(StgUpdateFrame);
4152 ((struct stack_gap *)frame)->gap_size = current_gap_size;
4153 ((struct stack_gap *)frame)->next_gap = gap;
4155 frame += sizeofW(StgUpdateFrame);
4159 // single update frame, or the topmost update frame in a series
4161 StgClosure *bh = upd->updatee;
4163 // Do lazy black-holing
4164 if (bh->header.info != &stg_BLACKHOLE_info &&
4165 bh->header.info != &stg_CAF_BLACKHOLE_info) {
4166 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4167 debugBelch("Unexpected lazy BHing required at 0x%04x",(int)bh);
4170 /* zero out the slop so that the sanity checker can tell
4171 * where the next closure is.
4174 StgInfoTable *bh_info = get_itbl(bh);
4175 nat np = bh_info->layout.payload.ptrs,
4176 nw = bh_info->layout.payload.nptrs, i;
4177 /* don't zero out slop for a THUNK_SELECTOR,
4178 * because its layout info is used for a
4179 * different purpose, and it's exactly the
4180 * same size as a BLACKHOLE in any case.
4182 if (bh_info->type != THUNK_SELECTOR) {
4183 for (i = 0; i < np + nw; i++) {
4184 ((StgClosure *)bh)->payload[i] = INVALID_OBJECT;
4190 // We pretend that bh is now dead.
4191 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4193 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
4194 SET_INFO(bh,&stg_BLACKHOLE_info);
4196 // We pretend that bh has just been created.
4197 LDV_RECORD_CREATE(bh);
4200 prev_was_update_frame = rtsTrue;
4201 updatee = upd->updatee;
4202 frame += sizeofW(StgUpdateFrame);
4208 prev_was_update_frame = rtsFalse;
4210 // we're not in a gap... check whether this is the end of a gap
4211 // (an update frame can't be the end of a gap).
4212 if (current_gap_size != 0) {
4213 gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
4215 current_gap_size = 0;
4217 frame += stack_frame_sizeW((StgClosure *)frame);
4224 // Now we have a stack with gaps in it, and we have to walk down
4225 // shoving the stack up to fill in the gaps. A diagram might
4229 // | ********* | <- sp
4233 // | stack_gap | <- gap | chunk_size
4235 // | ......... | <- gap_end v
4241 // 'sp' points the the current top-of-stack
4242 // 'gap' points to the stack_gap structure inside the gap
4243 // ***** indicates real stack data
4244 // ..... indicates gap
4245 // <empty> indicates unused
4249 void *gap_start, *next_gap_start, *gap_end;
4252 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4253 sp = next_gap_start;
4255 while ((StgPtr)gap > tso->sp) {
4257 // we're working in *bytes* now...
4258 gap_start = next_gap_start;
4259 gap_end = (void*) ((unsigned char*)gap_start - gap->gap_size * sizeof(W_));
4261 gap = gap->next_gap;
4262 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4264 chunk_size = (unsigned char*)gap_end - (unsigned char*)next_gap_start;
4266 memmove(sp, next_gap_start, chunk_size);
4269 tso->sp = (StgPtr)sp;
4273 /* -----------------------------------------------------------------------------
4276 * We have to prepare for GC - this means doing lazy black holing
4277 * here. We also take the opportunity to do stack squeezing if it's
4279 * -------------------------------------------------------------------------- */
4281 threadPaused(StgTSO *tso)
4283 if ( RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue )
4284 threadSqueezeStack(tso); // does black holing too
4286 threadLazyBlackHole(tso);
4289 /* -----------------------------------------------------------------------------
4291 * -------------------------------------------------------------------------- */
4295 printMutableList(generation *gen)
4300 debugBelch("@@ Mutable list %p: ", gen->mut_list);
4302 for (bd = gen->mut_list; bd != NULL; bd = bd->link) {
4303 for (p = bd->start; p < bd->free; p++) {
4304 debugBelch("%p (%s), ", (void *)*p, info_type((StgClosure *)*p));
4310 STATIC_INLINE rtsBool
4311 maybeLarge(StgClosure *closure)
4313 StgInfoTable *info = get_itbl(closure);
4315 /* closure types that may be found on the new_large_objects list;
4316 see scavenge_large */
4317 return (info->type == MUT_ARR_PTRS ||
4318 info->type == MUT_ARR_PTRS_FROZEN ||
4319 info->type == MUT_ARR_PTRS_FROZEN0 ||
4320 info->type == TSO ||
4321 info->type == ARR_WORDS);