1 /* -----------------------------------------------------------------------------
3 * (c) The GHC Team 1998-2003
5 * Generational garbage collector
7 * ---------------------------------------------------------------------------*/
9 #include "PosixSource.h"
14 #include "OSThreads.h"
16 #include "LdvProfile.h"
21 #include "BlockAlloc.h"
27 #include "ParTicky.h" // ToDo: move into Rts.h
28 #include "GCCompact.h"
31 #if defined(GRAN) || defined(PAR)
32 # include "GranSimRts.h"
33 # include "ParallelRts.h"
37 # include "ParallelDebug.h"
42 #if defined(RTS_GTK_FRONTPANEL)
43 #include "FrontPanel.h"
46 #include "RetainerProfile.h"
50 // Turn off inlining when debugging - it obfuscates things
53 # define STATIC_INLINE static
56 /* STATIC OBJECT LIST.
59 * We maintain a linked list of static objects that are still live.
60 * The requirements for this list are:
62 * - we need to scan the list while adding to it, in order to
63 * scavenge all the static objects (in the same way that
64 * breadth-first scavenging works for dynamic objects).
66 * - we need to be able to tell whether an object is already on
67 * the list, to break loops.
69 * Each static object has a "static link field", which we use for
70 * linking objects on to the list. We use a stack-type list, consing
71 * objects on the front as they are added (this means that the
72 * scavenge phase is depth-first, not breadth-first, but that
75 * A separate list is kept for objects that have been scavenged
76 * already - this is so that we can zero all the marks afterwards.
78 * An object is on the list if its static link field is non-zero; this
79 * means that we have to mark the end of the list with '1', not NULL.
81 * Extra notes for generational GC:
83 * Each generation has a static object list associated with it. When
84 * collecting generations up to N, we treat the static object lists
85 * from generations > N as roots.
87 * We build up a static object list while collecting generations 0..N,
88 * which is then appended to the static object list of generation N+1.
90 static StgClosure* static_objects; // live static objects
91 StgClosure* scavenged_static_objects; // static objects scavenged so far
93 /* N is the oldest generation being collected, where the generations
94 * are numbered starting at 0. A major GC (indicated by the major_gc
95 * flag) is when we're collecting all generations. We only attempt to
96 * deal with static objects and GC CAFs when doing a major GC.
99 static rtsBool major_gc;
101 /* Youngest generation that objects should be evacuated to in
102 * evacuate(). (Logically an argument to evacuate, but it's static
103 * a lot of the time so we optimise it into a global variable).
109 StgWeak *old_weak_ptr_list; // also pending finaliser list
111 /* Which stage of processing various kinds of weak pointer are we at?
112 * (see traverse_weak_ptr_list() below for discussion).
114 typedef enum { WeakPtrs, WeakThreads, WeakDone } WeakStage;
115 static WeakStage weak_stage;
117 /* List of all threads during GC
119 static StgTSO *old_all_threads;
120 StgTSO *resurrected_threads;
122 /* Flag indicating failure to evacuate an object to the desired
125 static rtsBool failed_to_evac;
127 /* Old to-space (used for two-space collector only)
129 static bdescr *old_to_blocks;
131 /* Data used for allocation area sizing.
133 static lnat new_blocks; // blocks allocated during this GC
134 static lnat g0s0_pcnt_kept = 30; // percentage of g0s0 live at last minor GC
136 /* Used to avoid long recursion due to selector thunks
138 static lnat thunk_selector_depth = 0;
139 #define MAX_THUNK_SELECTOR_DEPTH 8
141 /* -----------------------------------------------------------------------------
142 Static function declarations
143 -------------------------------------------------------------------------- */
145 static bdescr * gc_alloc_block ( step *stp );
146 static void mark_root ( StgClosure **root );
148 // Use a register argument for evacuate, if available.
150 #define REGPARM1 __attribute__((regparm(1)))
155 REGPARM1 static StgClosure * evacuate (StgClosure *q);
157 static void zero_static_object_list ( StgClosure* first_static );
159 static rtsBool traverse_weak_ptr_list ( void );
160 static void mark_weak_ptr_list ( StgWeak **list );
162 static StgClosure * eval_thunk_selector ( nat field, StgSelector * p );
165 static void scavenge ( step * );
166 static void scavenge_mark_stack ( void );
167 static void scavenge_stack ( StgPtr p, StgPtr stack_end );
168 static rtsBool scavenge_one ( StgPtr p );
169 static void scavenge_large ( step * );
170 static void scavenge_static ( void );
171 static void scavenge_mutable_list ( generation *g );
173 static void scavenge_large_bitmap ( StgPtr p,
174 StgLargeBitmap *large_bitmap,
177 #if 0 && defined(DEBUG)
178 static void gcCAFs ( void );
181 /* -----------------------------------------------------------------------------
182 inline functions etc. for dealing with the mark bitmap & stack.
183 -------------------------------------------------------------------------- */
185 #define MARK_STACK_BLOCKS 4
187 static bdescr *mark_stack_bdescr;
188 static StgPtr *mark_stack;
189 static StgPtr *mark_sp;
190 static StgPtr *mark_splim;
192 // Flag and pointers used for falling back to a linear scan when the
193 // mark stack overflows.
194 static rtsBool mark_stack_overflowed;
195 static bdescr *oldgen_scan_bd;
196 static StgPtr oldgen_scan;
198 STATIC_INLINE rtsBool
199 mark_stack_empty(void)
201 return mark_sp == mark_stack;
204 STATIC_INLINE rtsBool
205 mark_stack_full(void)
207 return mark_sp >= mark_splim;
211 reset_mark_stack(void)
213 mark_sp = mark_stack;
217 push_mark_stack(StgPtr p)
228 /* -----------------------------------------------------------------------------
229 Allocate a new to-space block in the given step.
230 -------------------------------------------------------------------------- */
233 gc_alloc_block(step *stp)
235 bdescr *bd = allocBlock();
236 bd->gen_no = stp->gen_no;
240 // blocks in to-space in generations up to and including N
241 // get the BF_EVACUATED flag.
242 if (stp->gen_no <= N) {
243 bd->flags = BF_EVACUATED;
248 // Start a new to-space block, chain it on after the previous one.
249 if (stp->hp_bd == NULL) {
252 stp->hp_bd->free = stp->hp;
253 stp->hp_bd->link = bd;
258 stp->hpLim = stp->hp + BLOCK_SIZE_W;
266 /* -----------------------------------------------------------------------------
269 Rough outline of the algorithm: for garbage collecting generation N
270 (and all younger generations):
272 - follow all pointers in the root set. the root set includes all
273 mutable objects in all generations (mutable_list).
275 - for each pointer, evacuate the object it points to into either
277 + to-space of the step given by step->to, which is the next
278 highest step in this generation or the first step in the next
279 generation if this is the last step.
281 + to-space of generations[evac_gen]->steps[0], if evac_gen != 0.
282 When we evacuate an object we attempt to evacuate
283 everything it points to into the same generation - this is
284 achieved by setting evac_gen to the desired generation. If
285 we can't do this, then an entry in the mut list has to
286 be made for the cross-generation pointer.
288 + if the object is already in a generation > N, then leave
291 - repeatedly scavenge to-space from each step in each generation
292 being collected until no more objects can be evacuated.
294 - free from-space in each step, and set from-space = to-space.
296 Locks held: sched_mutex
298 -------------------------------------------------------------------------- */
301 GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc )
305 lnat live, allocated, collected = 0, copied = 0;
306 lnat oldgen_saved_blocks = 0;
310 CostCentreStack *prev_CCS;
313 #if defined(DEBUG) && defined(GRAN)
314 IF_DEBUG(gc, debugBelch("@@ Starting garbage collection at %ld (%lx)\n",
318 #if defined(RTS_USER_SIGNALS)
323 // tell the STM to discard any cached closures its hoping to re-use
326 // tell the stats department that we've started a GC
329 // Init stats and print par specific (timing) info
330 PAR_TICKY_PAR_START();
332 // attribute any costs to CCS_GC
338 /* Approximate how much we allocated.
339 * Todo: only when generating stats?
341 allocated = calcAllocated();
343 /* Figure out which generation to collect
345 if (force_major_gc) {
346 N = RtsFlags.GcFlags.generations - 1;
350 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
351 if (generations[g].steps[0].n_blocks +
352 generations[g].steps[0].n_large_blocks
353 >= generations[g].max_blocks) {
357 major_gc = (N == RtsFlags.GcFlags.generations-1);
360 #ifdef RTS_GTK_FRONTPANEL
361 if (RtsFlags.GcFlags.frontpanel) {
362 updateFrontPanelBeforeGC(N);
366 // check stack sanity *before* GC (ToDo: check all threads)
368 // ToDo!: check sanity IF_DEBUG(sanity, checkTSOsSanity());
370 IF_DEBUG(sanity, checkFreeListSanity());
372 /* Initialise the static object lists
374 static_objects = END_OF_STATIC_LIST;
375 scavenged_static_objects = END_OF_STATIC_LIST;
377 /* Save the old to-space if we're doing a two-space collection
379 if (RtsFlags.GcFlags.generations == 1) {
380 old_to_blocks = g0s0->to_blocks;
381 g0s0->to_blocks = NULL;
382 g0s0->n_to_blocks = 0;
385 /* Keep a count of how many new blocks we allocated during this GC
386 * (used for resizing the allocation area, later).
390 // Initialise to-space in all the generations/steps that we're
393 for (g = 0; g <= N; g++) {
395 // throw away the mutable list. Invariant: the mutable list
396 // always has at least one block; this means we can avoid a check for
397 // NULL in recordMutable().
399 freeChain(generations[g].mut_list);
400 generations[g].mut_list = allocBlock();
403 for (s = 0; s < generations[g].n_steps; s++) {
405 // generation 0, step 0 doesn't need to-space
406 if (g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1) {
410 stp = &generations[g].steps[s];
411 ASSERT(stp->gen_no == g);
413 // start a new to-space for this step.
416 stp->to_blocks = NULL;
418 // allocate the first to-space block; extra blocks will be
419 // chained on as necessary.
420 bd = gc_alloc_block(stp);
422 stp->scan = bd->start;
425 // initialise the large object queues.
426 stp->new_large_objects = NULL;
427 stp->scavenged_large_objects = NULL;
428 stp->n_scavenged_large_blocks = 0;
430 // mark the large objects as not evacuated yet
431 for (bd = stp->large_objects; bd; bd = bd->link) {
432 bd->flags &= ~BF_EVACUATED;
435 // for a compacted step, we need to allocate the bitmap
436 if (stp->is_compacted) {
437 nat bitmap_size; // in bytes
438 bdescr *bitmap_bdescr;
441 bitmap_size = stp->n_blocks * BLOCK_SIZE / (sizeof(W_)*BITS_PER_BYTE);
443 if (bitmap_size > 0) {
444 bitmap_bdescr = allocGroup((lnat)BLOCK_ROUND_UP(bitmap_size)
446 stp->bitmap = bitmap_bdescr;
447 bitmap = bitmap_bdescr->start;
449 IF_DEBUG(gc, debugBelch("bitmap_size: %d, bitmap: %p",
450 bitmap_size, bitmap););
452 // don't forget to fill it with zeros!
453 memset(bitmap, 0, bitmap_size);
455 // For each block in this step, point to its bitmap from the
457 for (bd=stp->blocks; bd != NULL; bd = bd->link) {
458 bd->u.bitmap = bitmap;
459 bitmap += BLOCK_SIZE_W / (sizeof(W_)*BITS_PER_BYTE);
461 // Also at this point we set the BF_COMPACTED flag
462 // for this block. The invariant is that
463 // BF_COMPACTED is always unset, except during GC
464 // when it is set on those blocks which will be
466 bd->flags |= BF_COMPACTED;
473 /* make sure the older generations have at least one block to
474 * allocate into (this makes things easier for copy(), see below).
476 for (g = N+1; g < RtsFlags.GcFlags.generations; g++) {
477 for (s = 0; s < generations[g].n_steps; s++) {
478 stp = &generations[g].steps[s];
479 if (stp->hp_bd == NULL) {
480 ASSERT(stp->blocks == NULL);
481 bd = gc_alloc_block(stp);
485 /* Set the scan pointer for older generations: remember we
486 * still have to scavenge objects that have been promoted. */
488 stp->scan_bd = stp->hp_bd;
489 stp->to_blocks = NULL;
490 stp->n_to_blocks = 0;
491 stp->new_large_objects = NULL;
492 stp->scavenged_large_objects = NULL;
493 stp->n_scavenged_large_blocks = 0;
497 /* Allocate a mark stack if we're doing a major collection.
500 mark_stack_bdescr = allocGroup(MARK_STACK_BLOCKS);
501 mark_stack = (StgPtr *)mark_stack_bdescr->start;
502 mark_sp = mark_stack;
503 mark_splim = mark_stack + (MARK_STACK_BLOCKS * BLOCK_SIZE_W);
505 mark_stack_bdescr = NULL;
508 /* -----------------------------------------------------------------------
509 * follow all the roots that we know about:
510 * - mutable lists from each generation > N
511 * we want to *scavenge* these roots, not evacuate them: they're not
512 * going to move in this GC.
513 * Also: do them in reverse generation order. This is because we
514 * often want to promote objects that are pointed to by older
515 * generations early, so we don't have to repeatedly copy them.
516 * Doing the generations in reverse order ensures that we don't end
517 * up in the situation where we want to evac an object to gen 3 and
518 * it has already been evaced to gen 2.
522 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
523 generations[g].saved_mut_list = generations[g].mut_list;
524 generations[g].mut_list = allocBlock();
525 // mut_list always has at least one block.
528 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
529 IF_PAR_DEBUG(verbose, printMutableList(&generations[g]));
530 scavenge_mutable_list(&generations[g]);
532 for (st = generations[g].n_steps-1; st >= 0; st--) {
533 scavenge(&generations[g].steps[st]);
538 /* follow roots from the CAF list (used by GHCi)
543 /* follow all the roots that the application knows about.
546 get_roots(mark_root);
549 /* And don't forget to mark the TSO if we got here direct from
551 /* Not needed in a seq version?
553 CurrentTSO = (StgTSO *)MarkRoot((StgClosure *)CurrentTSO);
557 // Mark the entries in the GALA table of the parallel system
558 markLocalGAs(major_gc);
559 // Mark all entries on the list of pending fetches
560 markPendingFetches(major_gc);
563 /* Mark the weak pointer list, and prepare to detect dead weak
566 mark_weak_ptr_list(&weak_ptr_list);
567 old_weak_ptr_list = weak_ptr_list;
568 weak_ptr_list = NULL;
569 weak_stage = WeakPtrs;
571 /* The all_threads list is like the weak_ptr_list.
572 * See traverse_weak_ptr_list() for the details.
574 old_all_threads = all_threads;
575 all_threads = END_TSO_QUEUE;
576 resurrected_threads = END_TSO_QUEUE;
578 /* Mark the stable pointer table.
580 markStablePtrTable(mark_root);
582 /* -------------------------------------------------------------------------
583 * Repeatedly scavenge all the areas we know about until there's no
584 * more scavenging to be done.
591 // scavenge static objects
592 if (major_gc && static_objects != END_OF_STATIC_LIST) {
593 IF_DEBUG(sanity, checkStaticObjects(static_objects));
597 /* When scavenging the older generations: Objects may have been
598 * evacuated from generations <= N into older generations, and we
599 * need to scavenge these objects. We're going to try to ensure that
600 * any evacuations that occur move the objects into at least the
601 * same generation as the object being scavenged, otherwise we
602 * have to create new entries on the mutable list for the older
606 // scavenge each step in generations 0..maxgen
612 // scavenge objects in compacted generation
613 if (mark_stack_overflowed || oldgen_scan_bd != NULL ||
614 (mark_stack_bdescr != NULL && !mark_stack_empty())) {
615 scavenge_mark_stack();
619 for (gen = RtsFlags.GcFlags.generations; --gen >= 0; ) {
620 for (st = generations[gen].n_steps; --st >= 0; ) {
621 if (gen == 0 && st == 0 && RtsFlags.GcFlags.generations > 1) {
624 stp = &generations[gen].steps[st];
626 if (stp->hp_bd != stp->scan_bd || stp->scan < stp->hp) {
631 if (stp->new_large_objects != NULL) {
640 if (flag) { goto loop; }
642 // must be last... invariant is that everything is fully
643 // scavenged at this point.
644 if (traverse_weak_ptr_list()) { // returns rtsTrue if evaced something
649 /* Update the pointers from the "main thread" list - these are
650 * treated as weak pointers because we want to allow a main thread
651 * to get a BlockedOnDeadMVar exception in the same way as any other
652 * thread. Note that the threads should all have been retained by
653 * GC by virtue of being on the all_threads list, we're just
654 * updating pointers here.
659 for (m = main_threads; m != NULL; m = m->link) {
660 tso = (StgTSO *) isAlive((StgClosure *)m->tso);
662 barf("main thread has been GC'd");
669 // Reconstruct the Global Address tables used in GUM
670 rebuildGAtables(major_gc);
671 IF_DEBUG(sanity, checkLAGAtable(rtsTrue/*check closures, too*/));
674 // Now see which stable names are still alive.
677 // Tidy the end of the to-space chains
678 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
679 for (s = 0; s < generations[g].n_steps; s++) {
680 stp = &generations[g].steps[s];
681 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
682 ASSERT(Bdescr(stp->hp) == stp->hp_bd);
683 stp->hp_bd->free = stp->hp;
689 // We call processHeapClosureForDead() on every closure destroyed during
690 // the current garbage collection, so we invoke LdvCensusForDead().
691 if (RtsFlags.ProfFlags.doHeapProfile == HEAP_BY_LDV
692 || RtsFlags.ProfFlags.bioSelector != NULL)
696 // NO MORE EVACUATION AFTER THIS POINT!
697 // Finally: compaction of the oldest generation.
698 if (major_gc && oldest_gen->steps[0].is_compacted) {
699 // save number of blocks for stats
700 oldgen_saved_blocks = oldest_gen->steps[0].n_blocks;
704 IF_DEBUG(sanity, checkGlobalTSOList(rtsFalse));
706 /* run through all the generations/steps and tidy up
708 copied = new_blocks * BLOCK_SIZE_W;
709 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
712 generations[g].collections++; // for stats
715 // Count the mutable list as bytes "copied" for the purposes of
716 // stats. Every mutable list is copied during every GC.
718 for (bd = generations[g].mut_list; bd != NULL; bd = bd->link) {
719 copied += (bd->free - bd->start) * sizeof(StgWord);
723 for (s = 0; s < generations[g].n_steps; s++) {
725 stp = &generations[g].steps[s];
727 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
728 // stats information: how much we copied
730 copied -= stp->hp_bd->start + BLOCK_SIZE_W -
735 // for generations we collected...
738 // rough calculation of garbage collected, for stats output
739 if (stp->is_compacted) {
740 collected += (oldgen_saved_blocks - stp->n_blocks) * BLOCK_SIZE_W;
742 collected += stp->n_blocks * BLOCK_SIZE_W;
745 /* free old memory and shift to-space into from-space for all
746 * the collected steps (except the allocation area). These
747 * freed blocks will probaby be quickly recycled.
749 if (!(g == 0 && s == 0)) {
750 if (stp->is_compacted) {
751 // for a compacted step, just shift the new to-space
752 // onto the front of the now-compacted existing blocks.
753 for (bd = stp->to_blocks; bd != NULL; bd = bd->link) {
754 bd->flags &= ~BF_EVACUATED; // now from-space
756 // tack the new blocks on the end of the existing blocks
757 if (stp->blocks == NULL) {
758 stp->blocks = stp->to_blocks;
760 for (bd = stp->blocks; bd != NULL; bd = next) {
763 bd->link = stp->to_blocks;
765 // NB. this step might not be compacted next
766 // time, so reset the BF_COMPACTED flags.
767 // They are set before GC if we're going to
768 // compact. (search for BF_COMPACTED above).
769 bd->flags &= ~BF_COMPACTED;
772 // add the new blocks to the block tally
773 stp->n_blocks += stp->n_to_blocks;
775 freeChain(stp->blocks);
776 stp->blocks = stp->to_blocks;
777 stp->n_blocks = stp->n_to_blocks;
778 for (bd = stp->blocks; bd != NULL; bd = bd->link) {
779 bd->flags &= ~BF_EVACUATED; // now from-space
782 stp->to_blocks = NULL;
783 stp->n_to_blocks = 0;
786 /* LARGE OBJECTS. The current live large objects are chained on
787 * scavenged_large, having been moved during garbage
788 * collection from large_objects. Any objects left on
789 * large_objects list are therefore dead, so we free them here.
791 for (bd = stp->large_objects; bd != NULL; bd = next) {
797 // update the count of blocks used by large objects
798 for (bd = stp->scavenged_large_objects; bd != NULL; bd = bd->link) {
799 bd->flags &= ~BF_EVACUATED;
801 stp->large_objects = stp->scavenged_large_objects;
802 stp->n_large_blocks = stp->n_scavenged_large_blocks;
805 // for older generations...
807 /* For older generations, we need to append the
808 * scavenged_large_object list (i.e. large objects that have been
809 * promoted during this GC) to the large_object list for that step.
811 for (bd = stp->scavenged_large_objects; bd; bd = next) {
813 bd->flags &= ~BF_EVACUATED;
814 dbl_link_onto(bd, &stp->large_objects);
817 // add the new blocks we promoted during this GC
818 stp->n_blocks += stp->n_to_blocks;
819 stp->n_to_blocks = 0;
820 stp->n_large_blocks += stp->n_scavenged_large_blocks;
825 /* Reset the sizes of the older generations when we do a major
828 * CURRENT STRATEGY: make all generations except zero the same size.
829 * We have to stay within the maximum heap size, and leave a certain
830 * percentage of the maximum heap size available to allocate into.
832 if (major_gc && RtsFlags.GcFlags.generations > 1) {
833 nat live, size, min_alloc;
834 nat max = RtsFlags.GcFlags.maxHeapSize;
835 nat gens = RtsFlags.GcFlags.generations;
837 // live in the oldest generations
838 live = oldest_gen->steps[0].n_blocks +
839 oldest_gen->steps[0].n_large_blocks;
841 // default max size for all generations except zero
842 size = stg_max(live * RtsFlags.GcFlags.oldGenFactor,
843 RtsFlags.GcFlags.minOldGenSize);
845 // minimum size for generation zero
846 min_alloc = stg_max((RtsFlags.GcFlags.pcFreeHeap * max) / 200,
847 RtsFlags.GcFlags.minAllocAreaSize);
849 // Auto-enable compaction when the residency reaches a
850 // certain percentage of the maximum heap size (default: 30%).
851 if (RtsFlags.GcFlags.generations > 1 &&
852 (RtsFlags.GcFlags.compact ||
854 oldest_gen->steps[0].n_blocks >
855 (RtsFlags.GcFlags.compactThreshold * max) / 100))) {
856 oldest_gen->steps[0].is_compacted = 1;
857 // debugBelch("compaction: on\n", live);
859 oldest_gen->steps[0].is_compacted = 0;
860 // debugBelch("compaction: off\n", live);
863 // if we're going to go over the maximum heap size, reduce the
864 // size of the generations accordingly. The calculation is
865 // different if compaction is turned on, because we don't need
866 // to double the space required to collect the old generation.
869 // this test is necessary to ensure that the calculations
870 // below don't have any negative results - we're working
871 // with unsigned values here.
872 if (max < min_alloc) {
876 if (oldest_gen->steps[0].is_compacted) {
877 if ( (size + (size - 1) * (gens - 2) * 2) + min_alloc > max ) {
878 size = (max - min_alloc) / ((gens - 1) * 2 - 1);
881 if ( (size * (gens - 1) * 2) + min_alloc > max ) {
882 size = (max - min_alloc) / ((gens - 1) * 2);
892 debugBelch("live: %d, min_alloc: %d, size : %d, max = %d\n", live,
893 min_alloc, size, max);
896 for (g = 0; g < gens; g++) {
897 generations[g].max_blocks = size;
901 // Guess the amount of live data for stats.
904 /* Free the small objects allocated via allocate(), since this will
905 * all have been copied into G0S1 now.
907 if (small_alloc_list != NULL) {
908 freeChain(small_alloc_list);
910 small_alloc_list = NULL;
914 alloc_blocks_lim = RtsFlags.GcFlags.minAllocAreaSize;
916 // Start a new pinned_object_block
917 pinned_object_block = NULL;
919 /* Free the mark stack.
921 if (mark_stack_bdescr != NULL) {
922 freeGroup(mark_stack_bdescr);
927 for (g = 0; g <= N; g++) {
928 for (s = 0; s < generations[g].n_steps; s++) {
929 stp = &generations[g].steps[s];
930 if (stp->is_compacted && stp->bitmap != NULL) {
931 freeGroup(stp->bitmap);
936 /* Two-space collector:
937 * Free the old to-space, and estimate the amount of live data.
939 if (RtsFlags.GcFlags.generations == 1) {
942 if (old_to_blocks != NULL) {
943 freeChain(old_to_blocks);
945 for (bd = g0s0->to_blocks; bd != NULL; bd = bd->link) {
946 bd->flags = 0; // now from-space
949 /* For a two-space collector, we need to resize the nursery. */
951 /* set up a new nursery. Allocate a nursery size based on a
952 * function of the amount of live data (by default a factor of 2)
953 * Use the blocks from the old nursery if possible, freeing up any
956 * If we get near the maximum heap size, then adjust our nursery
957 * size accordingly. If the nursery is the same size as the live
958 * data (L), then we need 3L bytes. We can reduce the size of the
959 * nursery to bring the required memory down near 2L bytes.
961 * A normal 2-space collector would need 4L bytes to give the same
962 * performance we get from 3L bytes, reducing to the same
963 * performance at 2L bytes.
965 blocks = g0s0->n_to_blocks;
967 if ( RtsFlags.GcFlags.maxHeapSize != 0 &&
968 blocks * RtsFlags.GcFlags.oldGenFactor * 2 >
969 RtsFlags.GcFlags.maxHeapSize ) {
970 long adjusted_blocks; // signed on purpose
973 adjusted_blocks = (RtsFlags.GcFlags.maxHeapSize - 2 * blocks);
974 IF_DEBUG(gc, debugBelch("@@ Near maximum heap size of 0x%x blocks, blocks = %d, adjusted to %ld", RtsFlags.GcFlags.maxHeapSize, blocks, adjusted_blocks));
975 pc_free = adjusted_blocks * 100 / RtsFlags.GcFlags.maxHeapSize;
976 if (pc_free < RtsFlags.GcFlags.pcFreeHeap) /* might even be < 0 */ {
979 blocks = adjusted_blocks;
982 blocks *= RtsFlags.GcFlags.oldGenFactor;
983 if (blocks < RtsFlags.GcFlags.minAllocAreaSize) {
984 blocks = RtsFlags.GcFlags.minAllocAreaSize;
987 resizeNurseries(blocks);
990 /* Generational collector:
991 * If the user has given us a suggested heap size, adjust our
992 * allocation area to make best use of the memory available.
995 if (RtsFlags.GcFlags.heapSizeSuggestion) {
997 nat needed = calcNeeded(); // approx blocks needed at next GC
999 /* Guess how much will be live in generation 0 step 0 next time.
1000 * A good approximation is obtained by finding the
1001 * percentage of g0s0 that was live at the last minor GC.
1004 g0s0_pcnt_kept = (new_blocks * 100) / countNurseryBlocks();
1007 /* Estimate a size for the allocation area based on the
1008 * information available. We might end up going slightly under
1009 * or over the suggested heap size, but we should be pretty
1012 * Formula: suggested - needed
1013 * ----------------------------
1014 * 1 + g0s0_pcnt_kept/100
1016 * where 'needed' is the amount of memory needed at the next
1017 * collection for collecting all steps except g0s0.
1020 (((long)RtsFlags.GcFlags.heapSizeSuggestion - (long)needed) * 100) /
1021 (100 + (long)g0s0_pcnt_kept);
1023 if (blocks < (long)RtsFlags.GcFlags.minAllocAreaSize) {
1024 blocks = RtsFlags.GcFlags.minAllocAreaSize;
1027 resizeNurseries((nat)blocks);
1030 // we might have added extra large blocks to the nursery, so
1031 // resize back to minAllocAreaSize again.
1032 resizeNurseriesFixed(RtsFlags.GcFlags.minAllocAreaSize);
1036 // mark the garbage collected CAFs as dead
1037 #if 0 && defined(DEBUG) // doesn't work at the moment
1038 if (major_gc) { gcCAFs(); }
1042 // resetStaticObjectForRetainerProfiling() must be called before
1044 resetStaticObjectForRetainerProfiling();
1047 // zero the scavenged static object list
1049 zero_static_object_list(scavenged_static_objects);
1052 // Reset the nursery
1055 RELEASE_LOCK(&sched_mutex);
1057 // start any pending finalizers
1058 scheduleFinalizers(old_weak_ptr_list);
1060 // send exceptions to any threads which were about to die
1061 resurrectThreads(resurrected_threads);
1063 ACQUIRE_LOCK(&sched_mutex);
1065 // Update the stable pointer hash table.
1066 updateStablePtrTable(major_gc);
1068 // check sanity after GC
1069 IF_DEBUG(sanity, checkSanity());
1071 // extra GC trace info
1072 IF_DEBUG(gc, statDescribeGens());
1075 // symbol-table based profiling
1076 /* heapCensus(to_blocks); */ /* ToDo */
1079 // restore enclosing cost centre
1084 // check for memory leaks if sanity checking is on
1085 IF_DEBUG(sanity, memInventory());
1087 #ifdef RTS_GTK_FRONTPANEL
1088 if (RtsFlags.GcFlags.frontpanel) {
1089 updateFrontPanelAfterGC( N, live );
1093 // ok, GC over: tell the stats department what happened.
1094 stat_endGC(allocated, collected, live, copied, N);
1096 #if defined(RTS_USER_SIGNALS)
1097 // unblock signals again
1098 unblockUserSignals();
1105 /* -----------------------------------------------------------------------------
1108 traverse_weak_ptr_list is called possibly many times during garbage
1109 collection. It returns a flag indicating whether it did any work
1110 (i.e. called evacuate on any live pointers).
1112 Invariant: traverse_weak_ptr_list is called when the heap is in an
1113 idempotent state. That means that there are no pending
1114 evacuate/scavenge operations. This invariant helps the weak
1115 pointer code decide which weak pointers are dead - if there are no
1116 new live weak pointers, then all the currently unreachable ones are
1119 For generational GC: we just don't try to finalize weak pointers in
1120 older generations than the one we're collecting. This could
1121 probably be optimised by keeping per-generation lists of weak
1122 pointers, but for a few weak pointers this scheme will work.
1124 There are three distinct stages to processing weak pointers:
1126 - weak_stage == WeakPtrs
1128 We process all the weak pointers whos keys are alive (evacuate
1129 their values and finalizers), and repeat until we can find no new
1130 live keys. If no live keys are found in this pass, then we
1131 evacuate the finalizers of all the dead weak pointers in order to
1134 - weak_stage == WeakThreads
1136 Now, we discover which *threads* are still alive. Pointers to
1137 threads from the all_threads and main thread lists are the
1138 weakest of all: a pointers from the finalizer of a dead weak
1139 pointer can keep a thread alive. Any threads found to be unreachable
1140 are evacuated and placed on the resurrected_threads list so we
1141 can send them a signal later.
1143 - weak_stage == WeakDone
1145 No more evacuation is done.
1147 -------------------------------------------------------------------------- */
1150 traverse_weak_ptr_list(void)
1152 StgWeak *w, **last_w, *next_w;
1154 rtsBool flag = rtsFalse;
1156 switch (weak_stage) {
1162 /* doesn't matter where we evacuate values/finalizers to, since
1163 * these pointers are treated as roots (iff the keys are alive).
1167 last_w = &old_weak_ptr_list;
1168 for (w = old_weak_ptr_list; w != NULL; w = next_w) {
1170 /* There might be a DEAD_WEAK on the list if finalizeWeak# was
1171 * called on a live weak pointer object. Just remove it.
1173 if (w->header.info == &stg_DEAD_WEAK_info) {
1174 next_w = ((StgDeadWeak *)w)->link;
1179 switch (get_itbl(w)->type) {
1182 next_w = (StgWeak *)((StgEvacuated *)w)->evacuee;
1187 /* Now, check whether the key is reachable.
1189 new = isAlive(w->key);
1192 // evacuate the value and finalizer
1193 w->value = evacuate(w->value);
1194 w->finalizer = evacuate(w->finalizer);
1195 // remove this weak ptr from the old_weak_ptr list
1197 // and put it on the new weak ptr list
1199 w->link = weak_ptr_list;
1202 IF_DEBUG(weak, debugBelch("Weak pointer still alive at %p -> %p",
1207 last_w = &(w->link);
1213 barf("traverse_weak_ptr_list: not WEAK");
1217 /* If we didn't make any changes, then we can go round and kill all
1218 * the dead weak pointers. The old_weak_ptr list is used as a list
1219 * of pending finalizers later on.
1221 if (flag == rtsFalse) {
1222 for (w = old_weak_ptr_list; w; w = w->link) {
1223 w->finalizer = evacuate(w->finalizer);
1226 // Next, move to the WeakThreads stage after fully
1227 // scavenging the finalizers we've just evacuated.
1228 weak_stage = WeakThreads;
1234 /* Now deal with the all_threads list, which behaves somewhat like
1235 * the weak ptr list. If we discover any threads that are about to
1236 * become garbage, we wake them up and administer an exception.
1239 StgTSO *t, *tmp, *next, **prev;
1241 prev = &old_all_threads;
1242 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1244 tmp = (StgTSO *)isAlive((StgClosure *)t);
1250 ASSERT(get_itbl(t)->type == TSO);
1251 switch (t->what_next) {
1252 case ThreadRelocated:
1257 case ThreadComplete:
1258 // finshed or died. The thread might still be alive, but we
1259 // don't keep it on the all_threads list. Don't forget to
1260 // stub out its global_link field.
1261 next = t->global_link;
1262 t->global_link = END_TSO_QUEUE;
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 /* Finally, we can update the blackhole_queue. This queue
1298 * simply strings together TSOs blocked on black holes, it is
1299 * not intended to keep anything alive. Hence, we do not follow
1300 * pointers on the blackhole_queue until now, when we have
1301 * determined which TSOs are otherwise reachable. We know at
1302 * this point that all TSOs have been evacuated, however.
1306 for (pt = &blackhole_queue; *pt != END_TSO_QUEUE; pt = &((*pt)->link)) {
1307 *pt = (StgTSO *)isAlive((StgClosure *)*pt);
1308 ASSERT(*pt != NULL);
1312 weak_stage = WeakDone; // *now* we're done,
1313 return rtsTrue; // but one more round of scavenging, please
1316 barf("traverse_weak_ptr_list");
1322 /* -----------------------------------------------------------------------------
1323 After GC, the live weak pointer list may have forwarding pointers
1324 on it, because a weak pointer object was evacuated after being
1325 moved to the live weak pointer list. We remove those forwarding
1328 Also, we don't consider weak pointer objects to be reachable, but
1329 we must nevertheless consider them to be "live" and retain them.
1330 Therefore any weak pointer objects which haven't as yet been
1331 evacuated need to be evacuated now.
1332 -------------------------------------------------------------------------- */
1336 mark_weak_ptr_list ( StgWeak **list )
1338 StgWeak *w, **last_w;
1341 for (w = *list; w; w = w->link) {
1342 // w might be WEAK, EVACUATED, or DEAD_WEAK (actually CON_STATIC) here
1343 ASSERT(w->header.info == &stg_DEAD_WEAK_info
1344 || get_itbl(w)->type == WEAK || get_itbl(w)->type == EVACUATED);
1345 w = (StgWeak *)evacuate((StgClosure *)w);
1347 last_w = &(w->link);
1351 /* -----------------------------------------------------------------------------
1352 isAlive determines whether the given closure is still alive (after
1353 a garbage collection) or not. It returns the new address of the
1354 closure if it is alive, or NULL otherwise.
1356 NOTE: Use it before compaction only!
1357 -------------------------------------------------------------------------- */
1361 isAlive(StgClosure *p)
1363 const StgInfoTable *info;
1368 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
1371 // ignore static closures
1373 // ToDo: for static closures, check the static link field.
1374 // Problem here is that we sometimes don't set the link field, eg.
1375 // for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
1377 if (!HEAP_ALLOCED(p)) {
1381 // ignore closures in generations that we're not collecting.
1383 if (bd->gen_no > N) {
1387 // if it's a pointer into to-space, then we're done
1388 if (bd->flags & BF_EVACUATED) {
1392 // large objects use the evacuated flag
1393 if (bd->flags & BF_LARGE) {
1397 // check the mark bit for compacted steps
1398 if ((bd->flags & BF_COMPACTED) && is_marked((P_)p,bd)) {
1402 switch (info->type) {
1407 case IND_OLDGEN: // rely on compatible layout with StgInd
1408 case IND_OLDGEN_PERM:
1409 // follow indirections
1410 p = ((StgInd *)p)->indirectee;
1415 return ((StgEvacuated *)p)->evacuee;
1418 if (((StgTSO *)p)->what_next == ThreadRelocated) {
1419 p = (StgClosure *)((StgTSO *)p)->link;
1432 mark_root(StgClosure **root)
1434 *root = evacuate(*root);
1438 upd_evacuee(StgClosure *p, StgClosure *dest)
1440 // not true: (ToDo: perhaps it should be)
1441 // ASSERT(Bdescr((P_)dest)->flags & BF_EVACUATED);
1442 SET_INFO(p, &stg_EVACUATED_info);
1443 ((StgEvacuated *)p)->evacuee = dest;
1447 STATIC_INLINE StgClosure *
1448 copy(StgClosure *src, nat size, step *stp)
1453 nat size_org = size;
1456 TICK_GC_WORDS_COPIED(size);
1457 /* Find out where we're going, using the handy "to" pointer in
1458 * the step of the source object. If it turns out we need to
1459 * evacuate to an older generation, adjust it here (see comment
1462 if (stp->gen_no < evac_gen) {
1463 #ifdef NO_EAGER_PROMOTION
1464 failed_to_evac = rtsTrue;
1466 stp = &generations[evac_gen].steps[0];
1470 /* chain a new block onto the to-space for the destination step if
1473 if (stp->hp + size >= stp->hpLim) {
1474 gc_alloc_block(stp);
1477 for(to = stp->hp, from = (P_)src; size>0; --size) {
1483 upd_evacuee(src,(StgClosure *)dest);
1485 // We store the size of the just evacuated object in the LDV word so that
1486 // the profiler can guess the position of the next object later.
1487 SET_EVACUAEE_FOR_LDV(src, size_org);
1489 return (StgClosure *)dest;
1492 /* Special version of copy() for when we only want to copy the info
1493 * pointer of an object, but reserve some padding after it. This is
1494 * used to optimise evacuation of BLACKHOLEs.
1499 copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *stp)
1504 nat size_to_copy_org = size_to_copy;
1507 TICK_GC_WORDS_COPIED(size_to_copy);
1508 if (stp->gen_no < evac_gen) {
1509 #ifdef NO_EAGER_PROMOTION
1510 failed_to_evac = rtsTrue;
1512 stp = &generations[evac_gen].steps[0];
1516 if (stp->hp + size_to_reserve >= stp->hpLim) {
1517 gc_alloc_block(stp);
1520 for(to = stp->hp, from = (P_)src; size_to_copy>0; --size_to_copy) {
1525 stp->hp += size_to_reserve;
1526 upd_evacuee(src,(StgClosure *)dest);
1528 // We store the size of the just evacuated object in the LDV word so that
1529 // the profiler can guess the position of the next object later.
1530 // size_to_copy_org is wrong because the closure already occupies size_to_reserve
1532 SET_EVACUAEE_FOR_LDV(src, size_to_reserve);
1534 if (size_to_reserve - size_to_copy_org > 0)
1535 FILL_SLOP(stp->hp - 1, (int)(size_to_reserve - size_to_copy_org));
1537 return (StgClosure *)dest;
1541 /* -----------------------------------------------------------------------------
1542 Evacuate a large object
1544 This just consists of removing the object from the (doubly-linked)
1545 step->large_objects list, and linking it on to the (singly-linked)
1546 step->new_large_objects list, from where it will be scavenged later.
1548 Convention: bd->flags has BF_EVACUATED set for a large object
1549 that has been evacuated, or unset otherwise.
1550 -------------------------------------------------------------------------- */
1554 evacuate_large(StgPtr p)
1556 bdescr *bd = Bdescr(p);
1559 // object must be at the beginning of the block (or be a ByteArray)
1560 ASSERT(get_itbl((StgClosure *)p)->type == ARR_WORDS ||
1561 (((W_)p & BLOCK_MASK) == 0));
1563 // already evacuated?
1564 if (bd->flags & BF_EVACUATED) {
1565 /* Don't forget to set the failed_to_evac flag if we didn't get
1566 * the desired destination (see comments in evacuate()).
1568 if (bd->gen_no < evac_gen) {
1569 failed_to_evac = rtsTrue;
1570 TICK_GC_FAILED_PROMOTION();
1576 // remove from large_object list
1578 bd->u.back->link = bd->link;
1579 } else { // first object in the list
1580 stp->large_objects = bd->link;
1583 bd->link->u.back = bd->u.back;
1586 /* link it on to the evacuated large object list of the destination step
1589 if (stp->gen_no < evac_gen) {
1590 #ifdef NO_EAGER_PROMOTION
1591 failed_to_evac = rtsTrue;
1593 stp = &generations[evac_gen].steps[0];
1598 bd->gen_no = stp->gen_no;
1599 bd->link = stp->new_large_objects;
1600 stp->new_large_objects = bd;
1601 bd->flags |= BF_EVACUATED;
1604 /* -----------------------------------------------------------------------------
1607 This is called (eventually) for every live object in the system.
1609 The caller to evacuate specifies a desired generation in the
1610 evac_gen global variable. The following conditions apply to
1611 evacuating an object which resides in generation M when we're
1612 collecting up to generation N
1616 else evac to step->to
1618 if M < evac_gen evac to evac_gen, step 0
1620 if the object is already evacuated, then we check which generation
1623 if M >= evac_gen do nothing
1624 if M < evac_gen set failed_to_evac flag to indicate that we
1625 didn't manage to evacuate this object into evac_gen.
1630 evacuate() is the single most important function performance-wise
1631 in the GC. Various things have been tried to speed it up, but as
1632 far as I can tell the code generated by gcc 3.2 with -O2 is about
1633 as good as it's going to get. We pass the argument to evacuate()
1634 in a register using the 'regparm' attribute (see the prototype for
1635 evacuate() near the top of this file).
1637 Changing evacuate() to take an (StgClosure **) rather than
1638 returning the new pointer seems attractive, because we can avoid
1639 writing back the pointer when it hasn't changed (eg. for a static
1640 object, or an object in a generation > N). However, I tried it and
1641 it doesn't help. One reason is that the (StgClosure **) pointer
1642 gets spilled to the stack inside evacuate(), resulting in far more
1643 extra reads/writes than we save.
1644 -------------------------------------------------------------------------- */
1646 REGPARM1 static StgClosure *
1647 evacuate(StgClosure *q)
1654 const StgInfoTable *info;
1657 if (HEAP_ALLOCED(q)) {
1660 if (bd->gen_no > N) {
1661 /* Can't evacuate this object, because it's in a generation
1662 * older than the ones we're collecting. Let's hope that it's
1663 * in evac_gen or older, or we will have to arrange to track
1664 * this pointer using the mutable list.
1666 if (bd->gen_no < evac_gen) {
1668 failed_to_evac = rtsTrue;
1669 TICK_GC_FAILED_PROMOTION();
1674 /* evacuate large objects by re-linking them onto a different list.
1676 if (bd->flags & BF_LARGE) {
1678 if (info->type == TSO &&
1679 ((StgTSO *)q)->what_next == ThreadRelocated) {
1680 q = (StgClosure *)((StgTSO *)q)->link;
1683 evacuate_large((P_)q);
1687 /* If the object is in a step that we're compacting, then we
1688 * need to use an alternative evacuate procedure.
1690 if (bd->flags & BF_COMPACTED) {
1691 if (!is_marked((P_)q,bd)) {
1693 if (mark_stack_full()) {
1694 mark_stack_overflowed = rtsTrue;
1697 push_mark_stack((P_)q);
1702 /* Object is not already evacuated. */
1703 ASSERT((bd->flags & BF_EVACUATED) == 0);
1708 else stp = NULL; // make sure copy() will crash if HEAP_ALLOCED is wrong
1711 // make sure the info pointer is into text space
1712 ASSERT(LOOKS_LIKE_CLOSURE_PTR(q));
1715 switch (info -> type) {
1719 return copy(q,sizeW_fromITBL(info),stp);
1723 StgWord w = (StgWord)q->payload[0];
1724 if (q->header.info == Czh_con_info &&
1725 // unsigned, so always true: (StgChar)w >= MIN_CHARLIKE &&
1726 (StgChar)w <= MAX_CHARLIKE) {
1727 return (StgClosure *)CHARLIKE_CLOSURE((StgChar)w);
1729 if (q->header.info == Izh_con_info &&
1730 (StgInt)w >= MIN_INTLIKE && (StgInt)w <= MAX_INTLIKE) {
1731 return (StgClosure *)INTLIKE_CLOSURE((StgInt)w);
1733 // else, fall through ...
1739 return copy(q,sizeofW(StgHeader)+1,stp);
1743 return copy(q,sizeofW(StgThunk)+1,stp);
1748 #ifdef NO_PROMOTE_THUNKS
1749 if (bd->gen_no == 0 &&
1750 bd->step->no != 0 &&
1751 bd->step->no == generations[bd->gen_no].n_steps-1) {
1755 return copy(q,sizeofW(StgThunk)+2,stp);
1763 return copy(q,sizeofW(StgHeader)+2,stp);
1766 return copy(q,thunk_sizeW_fromITBL(info),stp);
1771 case IND_OLDGEN_PERM:
1775 return copy(q,sizeW_fromITBL(info),stp);
1778 return copy(q,bco_sizeW((StgBCO *)q),stp);
1781 case SE_CAF_BLACKHOLE:
1784 return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
1786 case THUNK_SELECTOR:
1790 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
1791 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1794 p = eval_thunk_selector(info->layout.selector_offset,
1798 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1800 // q is still BLACKHOLE'd.
1801 thunk_selector_depth++;
1803 thunk_selector_depth--;
1806 // We store the size of the just evacuated object in the
1807 // LDV word so that the profiler can guess the position of
1808 // the next object later.
1809 SET_EVACUAEE_FOR_LDV(q, THUNK_SELECTOR_sizeW());
1817 // follow chains of indirections, don't evacuate them
1818 q = ((StgInd*)q)->indirectee;
1822 if (info->srt_bitmap != 0 && major_gc &&
1823 *THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
1824 *THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
1825 static_objects = (StgClosure *)q;
1830 if (info->srt_bitmap != 0 && major_gc &&
1831 *FUN_STATIC_LINK((StgClosure *)q) == NULL) {
1832 *FUN_STATIC_LINK((StgClosure *)q) = static_objects;
1833 static_objects = (StgClosure *)q;
1838 /* If q->saved_info != NULL, then it's a revertible CAF - it'll be
1839 * on the CAF list, so don't do anything with it here (we'll
1840 * scavenge it later).
1843 && ((StgIndStatic *)q)->saved_info == NULL
1844 && *IND_STATIC_LINK((StgClosure *)q) == NULL) {
1845 *IND_STATIC_LINK((StgClosure *)q) = static_objects;
1846 static_objects = (StgClosure *)q;
1851 if (major_gc && *STATIC_LINK(info,(StgClosure *)q) == NULL) {
1852 *STATIC_LINK(info,(StgClosure *)q) = static_objects;
1853 static_objects = (StgClosure *)q;
1857 case CONSTR_INTLIKE:
1858 case CONSTR_CHARLIKE:
1859 case CONSTR_NOCAF_STATIC:
1860 /* no need to put these on the static linked list, they don't need
1874 case CATCH_STM_FRAME:
1875 case CATCH_RETRY_FRAME:
1876 case ATOMICALLY_FRAME:
1877 // shouldn't see these
1878 barf("evacuate: stack frame at %p\n", q);
1881 return copy(q,pap_sizeW((StgPAP*)q),stp);
1884 return copy(q,ap_sizeW((StgAP*)q),stp);
1887 return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp);
1890 /* Already evacuated, just return the forwarding address.
1891 * HOWEVER: if the requested destination generation (evac_gen) is
1892 * older than the actual generation (because the object was
1893 * already evacuated to a younger generation) then we have to
1894 * set the failed_to_evac flag to indicate that we couldn't
1895 * manage to promote the object to the desired generation.
1897 if (evac_gen > 0) { // optimisation
1898 StgClosure *p = ((StgEvacuated*)q)->evacuee;
1899 if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < evac_gen) {
1900 failed_to_evac = rtsTrue;
1901 TICK_GC_FAILED_PROMOTION();
1904 return ((StgEvacuated*)q)->evacuee;
1907 // just copy the block
1908 return copy(q,arr_words_sizeW((StgArrWords *)q),stp);
1911 case MUT_ARR_PTRS_FROZEN:
1912 case MUT_ARR_PTRS_FROZEN0:
1913 // just copy the block
1914 return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
1918 StgTSO *tso = (StgTSO *)q;
1920 /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
1922 if (tso->what_next == ThreadRelocated) {
1923 q = (StgClosure *)tso->link;
1927 /* To evacuate a small TSO, we need to relocate the update frame
1934 new_tso = (StgTSO *)copyPart((StgClosure *)tso,
1936 sizeofW(StgTSO), stp);
1937 move_TSO(tso, new_tso);
1938 for (p = tso->sp, q = new_tso->sp;
1939 p < tso->stack+tso->stack_size;) {
1943 return (StgClosure *)new_tso;
1950 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
1951 to = copy(q,BLACKHOLE_sizeW(),stp);
1952 //ToDo: derive size etc from reverted IP
1953 //to = copy(q,size,stp);
1955 debugBelch("@@ evacuate: RBH %p (%s) to %p (%s)",
1956 q, info_type(q), to, info_type(to)));
1961 ASSERT(sizeofW(StgBlockedFetch) >= MIN_NONUPD_SIZE);
1962 to = copy(q,sizeofW(StgBlockedFetch),stp);
1964 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
1965 q, info_type(q), to, info_type(to)));
1972 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1973 to = copy(q,sizeofW(StgFetchMe),stp);
1975 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
1976 q, info_type(q), to, info_type(to)));
1980 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1981 to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
1983 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
1984 q, info_type(q), to, info_type(to)));
1989 return copy(q,sizeofW(StgTRecHeader),stp);
1991 case TVAR_WAIT_QUEUE:
1992 return copy(q,sizeofW(StgTVarWaitQueue),stp);
1995 return copy(q,sizeofW(StgTVar),stp);
1998 return copy(q,sizeofW(StgTRecChunk),stp);
2001 barf("evacuate: strange closure type %d", (int)(info->type));
2007 /* -----------------------------------------------------------------------------
2008 Evaluate a THUNK_SELECTOR if possible.
2010 returns: NULL if we couldn't evaluate this THUNK_SELECTOR, or
2011 a closure pointer if we evaluated it and this is the result. Note
2012 that "evaluating" the THUNK_SELECTOR doesn't necessarily mean
2013 reducing it to HNF, just that we have eliminated the selection.
2014 The result might be another thunk, or even another THUNK_SELECTOR.
2016 If the return value is non-NULL, the original selector thunk has
2017 been BLACKHOLE'd, and should be updated with an indirection or a
2018 forwarding pointer. If the return value is NULL, then the selector
2022 ToDo: the treatment of THUNK_SELECTORS could be improved in the
2023 following way (from a suggestion by Ian Lynagh):
2025 We can have a chain like this:
2029 |-----> sel_0 --> (a,b)
2031 |-----> sel_0 --> ...
2033 and the depth limit means we don't go all the way to the end of the
2034 chain, which results in a space leak. This affects the recursive
2035 call to evacuate() in the THUNK_SELECTOR case in evacuate(): *not*
2036 the recursive call to eval_thunk_selector() in
2037 eval_thunk_selector().
2039 We could eliminate the depth bound in this case, in the following
2042 - traverse the chain once to discover the *value* of the
2043 THUNK_SELECTOR. Mark all THUNK_SELECTORS that we
2044 visit on the way as having been visited already (somehow).
2046 - in a second pass, traverse the chain again updating all
2047 THUNK_SEELCTORS that we find on the way with indirections to
2050 - if we encounter a "marked" THUNK_SELECTOR in a normal
2051 evacuate(), we konw it can't be updated so just evac it.
2053 Program that illustrates the problem:
2056 foo (x:xs) = let (ys, zs) = foo xs
2057 in if x >= 0 then (x:ys, zs) else (ys, x:zs)
2059 main = bar [1..(100000000::Int)]
2060 bar xs = (\(ys, zs) -> print ys >> print zs) (foo xs)
2062 -------------------------------------------------------------------------- */
2064 static inline rtsBool
2065 is_to_space ( StgClosure *p )
2069 bd = Bdescr((StgPtr)p);
2070 if (HEAP_ALLOCED(p) &&
2071 ((bd->flags & BF_EVACUATED)
2072 || ((bd->flags & BF_COMPACTED) &&
2073 is_marked((P_)p,bd)))) {
2081 eval_thunk_selector( nat field, StgSelector * p )
2084 const StgInfoTable *info_ptr;
2085 StgClosure *selectee;
2087 selectee = p->selectee;
2089 // Save the real info pointer (NOTE: not the same as get_itbl()).
2090 info_ptr = p->header.info;
2092 // If the THUNK_SELECTOR is in a generation that we are not
2093 // collecting, then bail out early. We won't be able to save any
2094 // space in any case, and updating with an indirection is trickier
2096 if (Bdescr((StgPtr)p)->gen_no > N) {
2100 // BLACKHOLE the selector thunk, since it is now under evaluation.
2101 // This is important to stop us going into an infinite loop if
2102 // this selector thunk eventually refers to itself.
2103 SET_INFO(p,&stg_BLACKHOLE_info);
2107 // We don't want to end up in to-space, because this causes
2108 // problems when the GC later tries to evacuate the result of
2109 // eval_thunk_selector(). There are various ways this could
2112 // 1. following an IND_STATIC
2114 // 2. when the old generation is compacted, the mark phase updates
2115 // from-space pointers to be to-space pointers, and we can't
2116 // reliably tell which we're following (eg. from an IND_STATIC).
2118 // 3. compacting GC again: if we're looking at a constructor in
2119 // the compacted generation, it might point directly to objects
2120 // in to-space. We must bale out here, otherwise doing the selection
2121 // will result in a to-space pointer being returned.
2123 // (1) is dealt with using a BF_EVACUATED test on the
2124 // selectee. (2) and (3): we can tell if we're looking at an
2125 // object in the compacted generation that might point to
2126 // to-space objects by testing that (a) it is BF_COMPACTED, (b)
2127 // the compacted generation is being collected, and (c) the
2128 // object is marked. Only a marked object may have pointers that
2129 // point to to-space objects, because that happens when
2132 // The to-space test is now embodied in the in_to_space() inline
2133 // function, as it is re-used below.
2135 if (is_to_space(selectee)) {
2139 info = get_itbl(selectee);
2140 switch (info->type) {
2148 case CONSTR_NOCAF_STATIC:
2149 // check that the size is in range
2150 ASSERT(field < (StgWord32)(info->layout.payload.ptrs +
2151 info->layout.payload.nptrs));
2153 // Select the right field from the constructor, and check
2154 // that the result isn't in to-space. It might be in
2155 // to-space if, for example, this constructor contains
2156 // pointers to younger-gen objects (and is on the mut-once
2161 q = selectee->payload[field];
2162 if (is_to_space(q)) {
2172 case IND_OLDGEN_PERM:
2174 selectee = ((StgInd *)selectee)->indirectee;
2178 // We don't follow pointers into to-space; the constructor
2179 // has already been evacuated, so we won't save any space
2180 // leaks by evaluating this selector thunk anyhow.
2183 case THUNK_SELECTOR:
2187 // check that we don't recurse too much, re-using the
2188 // depth bound also used in evacuate().
2189 if (thunk_selector_depth >= MAX_THUNK_SELECTOR_DEPTH) {
2192 thunk_selector_depth++;
2194 val = eval_thunk_selector(info->layout.selector_offset,
2195 (StgSelector *)selectee);
2197 thunk_selector_depth--;
2202 // We evaluated this selector thunk, so update it with
2203 // an indirection. NOTE: we don't use UPD_IND here,
2204 // because we are guaranteed that p is in a generation
2205 // that we are collecting, and we never want to put the
2206 // indirection on a mutable list.
2208 // For the purposes of LDV profiling, we have destroyed
2209 // the original selector thunk.
2210 SET_INFO(p, info_ptr);
2211 LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(selectee);
2213 ((StgInd *)selectee)->indirectee = val;
2214 SET_INFO(selectee,&stg_IND_info);
2216 // For the purposes of LDV profiling, we have created an
2218 LDV_RECORD_CREATE(selectee);
2235 case SE_CAF_BLACKHOLE:
2247 // not evaluated yet
2251 barf("eval_thunk_selector: strange selectee %d",
2256 // We didn't manage to evaluate this thunk; restore the old info pointer
2257 SET_INFO(p, info_ptr);
2261 /* -----------------------------------------------------------------------------
2262 move_TSO is called to update the TSO structure after it has been
2263 moved from one place to another.
2264 -------------------------------------------------------------------------- */
2267 move_TSO (StgTSO *src, StgTSO *dest)
2271 // relocate the stack pointer...
2272 diff = (StgPtr)dest - (StgPtr)src; // In *words*
2273 dest->sp = (StgPtr)dest->sp + diff;
2276 /* Similar to scavenge_large_bitmap(), but we don't write back the
2277 * pointers we get back from evacuate().
2280 scavenge_large_srt_bitmap( StgLargeSRT *large_srt )
2287 bitmap = large_srt->l.bitmap[b];
2288 size = (nat)large_srt->l.size;
2289 p = (StgClosure **)large_srt->srt;
2290 for (i = 0; i < size; ) {
2291 if ((bitmap & 1) != 0) {
2296 if (i % BITS_IN(W_) == 0) {
2298 bitmap = large_srt->l.bitmap[b];
2300 bitmap = bitmap >> 1;
2305 /* evacuate the SRT. If srt_bitmap is zero, then there isn't an
2306 * srt field in the info table. That's ok, because we'll
2307 * never dereference it.
2310 scavenge_srt (StgClosure **srt, nat srt_bitmap)
2315 bitmap = srt_bitmap;
2318 if (bitmap == (StgHalfWord)(-1)) {
2319 scavenge_large_srt_bitmap( (StgLargeSRT *)srt );
2323 while (bitmap != 0) {
2324 if ((bitmap & 1) != 0) {
2325 #ifdef ENABLE_WIN32_DLL_SUPPORT
2326 // Special-case to handle references to closures hiding out in DLLs, since
2327 // double indirections required to get at those. The code generator knows
2328 // which is which when generating the SRT, so it stores the (indirect)
2329 // reference to the DLL closure in the table by first adding one to it.
2330 // We check for this here, and undo the addition before evacuating it.
2332 // If the SRT entry hasn't got bit 0 set, the SRT entry points to a
2333 // closure that's fixed at link-time, and no extra magic is required.
2334 if ( (unsigned long)(*srt) & 0x1 ) {
2335 evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
2344 bitmap = bitmap >> 1;
2350 scavenge_thunk_srt(const StgInfoTable *info)
2352 StgThunkInfoTable *thunk_info;
2354 thunk_info = itbl_to_thunk_itbl(info);
2355 scavenge_srt((StgClosure **)GET_SRT(thunk_info), thunk_info->i.srt_bitmap);
2359 scavenge_fun_srt(const StgInfoTable *info)
2361 StgFunInfoTable *fun_info;
2363 fun_info = itbl_to_fun_itbl(info);
2364 scavenge_srt((StgClosure **)GET_FUN_SRT(fun_info), fun_info->i.srt_bitmap);
2367 /* -----------------------------------------------------------------------------
2369 -------------------------------------------------------------------------- */
2372 scavengeTSO (StgTSO *tso)
2374 // We don't chase the link field: TSOs on the blackhole queue are
2375 // not automatically alive, so the link field is a "weak" pointer.
2376 // Queues of TSOs are traversed explicitly.
2378 if ( tso->why_blocked == BlockedOnMVar
2379 || tso->why_blocked == BlockedOnBlackHole
2380 || tso->why_blocked == BlockedOnException
2382 || tso->why_blocked == BlockedOnGA
2383 || tso->why_blocked == BlockedOnGA_NoSend
2386 tso->block_info.closure = evacuate(tso->block_info.closure);
2388 if ( tso->blocked_exceptions != NULL ) {
2389 tso->blocked_exceptions =
2390 (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
2393 // scavange current transaction record
2394 tso->trec = (StgTRecHeader *)evacuate((StgClosure *)tso->trec);
2396 // scavenge this thread's stack
2397 scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
2400 /* -----------------------------------------------------------------------------
2401 Blocks of function args occur on the stack (at the top) and
2403 -------------------------------------------------------------------------- */
2405 STATIC_INLINE StgPtr
2406 scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
2413 switch (fun_info->f.fun_type) {
2415 bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
2416 size = BITMAP_SIZE(fun_info->f.b.bitmap);
2419 size = GET_FUN_LARGE_BITMAP(fun_info)->size;
2420 scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
2424 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2425 size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->f.fun_type]);
2428 if ((bitmap & 1) == 0) {
2429 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2432 bitmap = bitmap >> 1;
2440 STATIC_INLINE StgPtr
2441 scavenge_PAP_payload (StgClosure *fun, StgClosure **payload, StgWord size)
2445 StgFunInfoTable *fun_info;
2447 fun_info = get_fun_itbl(fun);
2448 ASSERT(fun_info->i.type != PAP);
2449 p = (StgPtr)payload;
2451 switch (fun_info->f.fun_type) {
2453 bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
2456 scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
2460 scavenge_large_bitmap((StgPtr)payload, BCO_BITMAP(fun), size);
2464 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2467 if ((bitmap & 1) == 0) {
2468 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2471 bitmap = bitmap >> 1;
2479 STATIC_INLINE StgPtr
2480 scavenge_PAP (StgPAP *pap)
2482 pap->fun = evacuate(pap->fun);
2483 return scavenge_PAP_payload (pap->fun, pap->payload, pap->n_args);
2486 STATIC_INLINE StgPtr
2487 scavenge_AP (StgAP *ap)
2489 ap->fun = evacuate(ap->fun);
2490 return scavenge_PAP_payload (ap->fun, ap->payload, ap->n_args);
2493 /* -----------------------------------------------------------------------------
2494 Scavenge a given step until there are no more objects in this step
2497 evac_gen is set by the caller to be either zero (for a step in a
2498 generation < N) or G where G is the generation of the step being
2501 We sometimes temporarily change evac_gen back to zero if we're
2502 scavenging a mutable object where early promotion isn't such a good
2504 -------------------------------------------------------------------------- */
2512 nat saved_evac_gen = evac_gen;
2517 failed_to_evac = rtsFalse;
2519 /* scavenge phase - standard breadth-first scavenging of the
2523 while (bd != stp->hp_bd || p < stp->hp) {
2525 // If we're at the end of this block, move on to the next block
2526 if (bd != stp->hp_bd && p == bd->free) {
2532 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2533 info = get_itbl((StgClosure *)p);
2535 ASSERT(thunk_selector_depth == 0);
2538 switch (info->type) {
2542 StgMVar *mvar = ((StgMVar *)p);
2544 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
2545 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
2546 mvar->value = evacuate((StgClosure *)mvar->value);
2547 evac_gen = saved_evac_gen;
2548 failed_to_evac = rtsTrue; // mutable.
2549 p += sizeofW(StgMVar);
2554 scavenge_fun_srt(info);
2555 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2556 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2557 p += sizeofW(StgHeader) + 2;
2561 scavenge_thunk_srt(info);
2562 ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
2563 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2564 p += sizeofW(StgThunk) + 2;
2568 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2569 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2570 p += sizeofW(StgHeader) + 2;
2574 scavenge_thunk_srt(info);
2575 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2576 p += sizeofW(StgThunk) + 1;
2580 scavenge_fun_srt(info);
2582 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2583 p += sizeofW(StgHeader) + 1;
2587 scavenge_thunk_srt(info);
2588 p += sizeofW(StgThunk) + 1;
2592 scavenge_fun_srt(info);
2594 p += sizeofW(StgHeader) + 1;
2598 scavenge_thunk_srt(info);
2599 p += sizeofW(StgThunk) + 2;
2603 scavenge_fun_srt(info);
2605 p += sizeofW(StgHeader) + 2;
2609 scavenge_thunk_srt(info);
2610 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2611 p += sizeofW(StgThunk) + 2;
2615 scavenge_fun_srt(info);
2617 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2618 p += sizeofW(StgHeader) + 2;
2622 scavenge_fun_srt(info);
2629 scavenge_thunk_srt(info);
2630 end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
2631 for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
2632 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2634 p += info->layout.payload.nptrs;
2646 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2647 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2648 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2650 p += info->layout.payload.nptrs;
2655 StgBCO *bco = (StgBCO *)p;
2656 bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
2657 bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
2658 bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
2659 bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
2660 p += bco_sizeW(bco);
2665 if (stp->gen->no != 0) {
2668 // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an
2669 // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
2670 LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
2673 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
2675 SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
2677 // We pretend that p has just been created.
2678 LDV_RECORD_CREATE((StgClosure *)p);
2681 case IND_OLDGEN_PERM:
2682 ((StgInd *)p)->indirectee = evacuate(((StgInd *)p)->indirectee);
2683 p += sizeofW(StgInd);
2688 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2689 evac_gen = saved_evac_gen;
2690 failed_to_evac = rtsTrue; // mutable anyhow
2691 p += sizeofW(StgMutVar);
2695 case SE_CAF_BLACKHOLE:
2698 p += BLACKHOLE_sizeW();
2701 case THUNK_SELECTOR:
2703 StgSelector *s = (StgSelector *)p;
2704 s->selectee = evacuate(s->selectee);
2705 p += THUNK_SELECTOR_sizeW();
2709 // A chunk of stack saved in a heap object
2712 StgAP_STACK *ap = (StgAP_STACK *)p;
2714 ap->fun = evacuate(ap->fun);
2715 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2716 p = (StgPtr)ap->payload + ap->size;
2721 p = scavenge_PAP((StgPAP *)p);
2725 p = scavenge_AP((StgAP *)p);
2729 // nothing to follow
2730 p += arr_words_sizeW((StgArrWords *)p);
2734 // follow everything
2738 evac_gen = 0; // repeatedly mutable
2739 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2740 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2741 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2743 evac_gen = saved_evac_gen;
2744 failed_to_evac = rtsTrue; // mutable anyhow.
2748 case MUT_ARR_PTRS_FROZEN:
2749 case MUT_ARR_PTRS_FROZEN0:
2750 // follow everything
2754 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2755 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2756 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2758 // it's tempting to recordMutable() if failed_to_evac is
2759 // false, but that breaks some assumptions (eg. every
2760 // closure on the mutable list is supposed to have the MUT
2761 // flag set, and MUT_ARR_PTRS_FROZEN doesn't).
2767 StgTSO *tso = (StgTSO *)p;
2770 evac_gen = saved_evac_gen;
2771 failed_to_evac = rtsTrue; // mutable anyhow.
2772 p += tso_sizeW(tso);
2780 nat size, ptrs, nonptrs, vhs;
2782 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2784 StgRBH *rbh = (StgRBH *)p;
2785 (StgClosure *)rbh->blocking_queue =
2786 evacuate((StgClosure *)rbh->blocking_queue);
2787 failed_to_evac = rtsTrue; // mutable anyhow.
2789 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2790 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2791 // ToDo: use size of reverted closure here!
2792 p += BLACKHOLE_sizeW();
2798 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2799 // follow the pointer to the node which is being demanded
2800 (StgClosure *)bf->node =
2801 evacuate((StgClosure *)bf->node);
2802 // follow the link to the rest of the blocking queue
2803 (StgClosure *)bf->link =
2804 evacuate((StgClosure *)bf->link);
2806 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
2807 bf, info_type((StgClosure *)bf),
2808 bf->node, info_type(bf->node)));
2809 p += sizeofW(StgBlockedFetch);
2817 p += sizeofW(StgFetchMe);
2818 break; // nothing to do in this case
2822 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
2823 (StgClosure *)fmbq->blocking_queue =
2824 evacuate((StgClosure *)fmbq->blocking_queue);
2826 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
2827 p, info_type((StgClosure *)p)));
2828 p += sizeofW(StgFetchMeBlockingQueue);
2833 case TVAR_WAIT_QUEUE:
2835 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
2837 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
2838 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
2839 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
2840 evac_gen = saved_evac_gen;
2841 failed_to_evac = rtsTrue; // mutable
2842 p += sizeofW(StgTVarWaitQueue);
2848 StgTVar *tvar = ((StgTVar *) p);
2850 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
2851 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
2852 evac_gen = saved_evac_gen;
2853 failed_to_evac = rtsTrue; // mutable
2854 p += sizeofW(StgTVar);
2860 StgTRecHeader *trec = ((StgTRecHeader *) p);
2862 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
2863 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
2864 evac_gen = saved_evac_gen;
2865 failed_to_evac = rtsTrue; // mutable
2866 p += sizeofW(StgTRecHeader);
2873 StgTRecChunk *tc = ((StgTRecChunk *) p);
2874 TRecEntry *e = &(tc -> entries[0]);
2876 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
2877 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
2878 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
2879 e->expected_value = evacuate((StgClosure*)e->expected_value);
2880 e->new_value = evacuate((StgClosure*)e->new_value);
2882 evac_gen = saved_evac_gen;
2883 failed_to_evac = rtsTrue; // mutable
2884 p += sizeofW(StgTRecChunk);
2889 barf("scavenge: unimplemented/strange closure type %d @ %p",
2894 * We need to record the current object on the mutable list if
2895 * (a) It is actually mutable, or
2896 * (b) It contains pointers to a younger generation.
2897 * Case (b) arises if we didn't manage to promote everything that
2898 * the current object points to into the current generation.
2900 if (failed_to_evac) {
2901 failed_to_evac = rtsFalse;
2902 recordMutableGen((StgClosure *)q, stp->gen);
2910 /* -----------------------------------------------------------------------------
2911 Scavenge everything on the mark stack.
2913 This is slightly different from scavenge():
2914 - we don't walk linearly through the objects, so the scavenger
2915 doesn't need to advance the pointer on to the next object.
2916 -------------------------------------------------------------------------- */
2919 scavenge_mark_stack(void)
2925 evac_gen = oldest_gen->no;
2926 saved_evac_gen = evac_gen;
2929 while (!mark_stack_empty()) {
2930 p = pop_mark_stack();
2932 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2933 info = get_itbl((StgClosure *)p);
2936 switch (info->type) {
2940 StgMVar *mvar = ((StgMVar *)p);
2942 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
2943 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
2944 mvar->value = evacuate((StgClosure *)mvar->value);
2945 evac_gen = saved_evac_gen;
2946 failed_to_evac = rtsTrue; // mutable.
2951 scavenge_fun_srt(info);
2952 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2953 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2957 scavenge_thunk_srt(info);
2958 ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
2959 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2963 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2964 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2969 scavenge_fun_srt(info);
2970 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2975 scavenge_thunk_srt(info);
2976 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2981 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2986 scavenge_fun_srt(info);
2991 scavenge_thunk_srt(info);
2999 scavenge_fun_srt(info);
3006 scavenge_thunk_srt(info);
3007 end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
3008 for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
3009 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3022 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3023 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
3024 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3030 StgBCO *bco = (StgBCO *)p;
3031 bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
3032 bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
3033 bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
3034 bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
3039 // don't need to do anything here: the only possible case
3040 // is that we're in a 1-space compacting collector, with
3041 // no "old" generation.
3045 case IND_OLDGEN_PERM:
3046 ((StgInd *)p)->indirectee =
3047 evacuate(((StgInd *)p)->indirectee);
3052 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3053 evac_gen = saved_evac_gen;
3054 failed_to_evac = rtsTrue;
3058 case SE_CAF_BLACKHOLE:
3064 case THUNK_SELECTOR:
3066 StgSelector *s = (StgSelector *)p;
3067 s->selectee = evacuate(s->selectee);
3071 // A chunk of stack saved in a heap object
3074 StgAP_STACK *ap = (StgAP_STACK *)p;
3076 ap->fun = evacuate(ap->fun);
3077 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3082 scavenge_PAP((StgPAP *)p);
3086 scavenge_AP((StgAP *)p);
3090 // follow everything
3094 evac_gen = 0; // repeatedly mutable
3095 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3096 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3097 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3099 evac_gen = saved_evac_gen;
3100 failed_to_evac = rtsTrue; // mutable anyhow.
3104 case MUT_ARR_PTRS_FROZEN:
3105 case MUT_ARR_PTRS_FROZEN0:
3106 // follow everything
3110 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3111 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3112 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3119 StgTSO *tso = (StgTSO *)p;
3122 evac_gen = saved_evac_gen;
3123 failed_to_evac = rtsTrue;
3131 nat size, ptrs, nonptrs, vhs;
3133 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3135 StgRBH *rbh = (StgRBH *)p;
3136 bh->blocking_queue =
3137 (StgTSO *)evacuate((StgClosure *)bh->blocking_queue);
3138 failed_to_evac = rtsTrue; // mutable anyhow.
3140 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3141 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3147 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3148 // follow the pointer to the node which is being demanded
3149 (StgClosure *)bf->node =
3150 evacuate((StgClosure *)bf->node);
3151 // follow the link to the rest of the blocking queue
3152 (StgClosure *)bf->link =
3153 evacuate((StgClosure *)bf->link);
3155 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3156 bf, info_type((StgClosure *)bf),
3157 bf->node, info_type(bf->node)));
3165 break; // nothing to do in this case
3169 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3170 (StgClosure *)fmbq->blocking_queue =
3171 evacuate((StgClosure *)fmbq->blocking_queue);
3173 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3174 p, info_type((StgClosure *)p)));
3179 case TVAR_WAIT_QUEUE:
3181 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3183 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3184 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3185 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3186 evac_gen = saved_evac_gen;
3187 failed_to_evac = rtsTrue; // mutable
3193 StgTVar *tvar = ((StgTVar *) p);
3195 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3196 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3197 evac_gen = saved_evac_gen;
3198 failed_to_evac = rtsTrue; // mutable
3205 StgTRecChunk *tc = ((StgTRecChunk *) p);
3206 TRecEntry *e = &(tc -> entries[0]);
3208 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3209 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3210 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3211 e->expected_value = evacuate((StgClosure*)e->expected_value);
3212 e->new_value = evacuate((StgClosure*)e->new_value);
3214 evac_gen = saved_evac_gen;
3215 failed_to_evac = rtsTrue; // mutable
3221 StgTRecHeader *trec = ((StgTRecHeader *) p);
3223 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3224 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3225 evac_gen = saved_evac_gen;
3226 failed_to_evac = rtsTrue; // mutable
3231 barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p",
3235 if (failed_to_evac) {
3236 failed_to_evac = rtsFalse;
3237 recordMutableGen((StgClosure *)q, &generations[evac_gen]);
3240 // mark the next bit to indicate "scavenged"
3241 mark(q+1, Bdescr(q));
3243 } // while (!mark_stack_empty())
3245 // start a new linear scan if the mark stack overflowed at some point
3246 if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
3247 IF_DEBUG(gc, debugBelch("scavenge_mark_stack: starting linear scan"));
3248 mark_stack_overflowed = rtsFalse;
3249 oldgen_scan_bd = oldest_gen->steps[0].blocks;
3250 oldgen_scan = oldgen_scan_bd->start;
3253 if (oldgen_scan_bd) {
3254 // push a new thing on the mark stack
3256 // find a closure that is marked but not scavenged, and start
3258 while (oldgen_scan < oldgen_scan_bd->free
3259 && !is_marked(oldgen_scan,oldgen_scan_bd)) {
3263 if (oldgen_scan < oldgen_scan_bd->free) {
3265 // already scavenged?
3266 if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
3267 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3270 push_mark_stack(oldgen_scan);
3271 // ToDo: bump the linear scan by the actual size of the object
3272 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3276 oldgen_scan_bd = oldgen_scan_bd->link;
3277 if (oldgen_scan_bd != NULL) {
3278 oldgen_scan = oldgen_scan_bd->start;
3284 /* -----------------------------------------------------------------------------
3285 Scavenge one object.
3287 This is used for objects that are temporarily marked as mutable
3288 because they contain old-to-new generation pointers. Only certain
3289 objects can have this property.
3290 -------------------------------------------------------------------------- */
3293 scavenge_one(StgPtr p)
3295 const StgInfoTable *info;
3296 nat saved_evac_gen = evac_gen;
3299 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3300 info = get_itbl((StgClosure *)p);
3302 switch (info->type) {
3306 StgMVar *mvar = ((StgMVar *)p);
3308 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
3309 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
3310 mvar->value = evacuate((StgClosure *)mvar->value);
3311 evac_gen = saved_evac_gen;
3312 failed_to_evac = rtsTrue; // mutable.
3325 end = (StgPtr)((StgThunk *)p)->payload + info->layout.payload.ptrs;
3326 for (q = (StgPtr)((StgThunk *)p)->payload; q < end; q++) {
3327 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3333 case FUN_1_0: // hardly worth specialising these guys
3350 end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3351 for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
3352 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3359 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3360 evac_gen = saved_evac_gen;
3361 failed_to_evac = rtsTrue; // mutable anyhow
3365 case SE_CAF_BLACKHOLE:
3370 case THUNK_SELECTOR:
3372 StgSelector *s = (StgSelector *)p;
3373 s->selectee = evacuate(s->selectee);
3379 StgAP_STACK *ap = (StgAP_STACK *)p;
3381 ap->fun = evacuate(ap->fun);
3382 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3383 p = (StgPtr)ap->payload + ap->size;
3388 p = scavenge_PAP((StgPAP *)p);
3392 p = scavenge_AP((StgAP *)p);
3396 // nothing to follow
3401 // follow everything
3404 evac_gen = 0; // repeatedly mutable
3405 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3406 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3407 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3409 evac_gen = saved_evac_gen;
3410 failed_to_evac = rtsTrue;
3414 case MUT_ARR_PTRS_FROZEN:
3415 case MUT_ARR_PTRS_FROZEN0:
3417 // follow everything
3420 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3421 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3422 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3429 StgTSO *tso = (StgTSO *)p;
3431 evac_gen = 0; // repeatedly mutable
3433 evac_gen = saved_evac_gen;
3434 failed_to_evac = rtsTrue;
3442 nat size, ptrs, nonptrs, vhs;
3444 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3446 StgRBH *rbh = (StgRBH *)p;
3447 (StgClosure *)rbh->blocking_queue =
3448 evacuate((StgClosure *)rbh->blocking_queue);
3449 failed_to_evac = rtsTrue; // mutable anyhow.
3451 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3452 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3453 // ToDo: use size of reverted closure here!
3459 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3460 // follow the pointer to the node which is being demanded
3461 (StgClosure *)bf->node =
3462 evacuate((StgClosure *)bf->node);
3463 // follow the link to the rest of the blocking queue
3464 (StgClosure *)bf->link =
3465 evacuate((StgClosure *)bf->link);
3467 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3468 bf, info_type((StgClosure *)bf),
3469 bf->node, info_type(bf->node)));
3477 break; // nothing to do in this case
3481 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3482 (StgClosure *)fmbq->blocking_queue =
3483 evacuate((StgClosure *)fmbq->blocking_queue);
3485 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3486 p, info_type((StgClosure *)p)));
3491 case TVAR_WAIT_QUEUE:
3493 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3495 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3496 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3497 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3498 evac_gen = saved_evac_gen;
3499 failed_to_evac = rtsTrue; // mutable
3505 StgTVar *tvar = ((StgTVar *) p);
3507 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3508 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3509 evac_gen = saved_evac_gen;
3510 failed_to_evac = rtsTrue; // mutable
3516 StgTRecHeader *trec = ((StgTRecHeader *) p);
3518 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3519 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3520 evac_gen = saved_evac_gen;
3521 failed_to_evac = rtsTrue; // mutable
3528 StgTRecChunk *tc = ((StgTRecChunk *) p);
3529 TRecEntry *e = &(tc -> entries[0]);
3531 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3532 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3533 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3534 e->expected_value = evacuate((StgClosure*)e->expected_value);
3535 e->new_value = evacuate((StgClosure*)e->new_value);
3537 evac_gen = saved_evac_gen;
3538 failed_to_evac = rtsTrue; // mutable
3543 case IND_OLDGEN_PERM:
3546 /* Careful here: a THUNK can be on the mutable list because
3547 * it contains pointers to young gen objects. If such a thunk
3548 * is updated, the IND_OLDGEN will be added to the mutable
3549 * list again, and we'll scavenge it twice. evacuate()
3550 * doesn't check whether the object has already been
3551 * evacuated, so we perform that check here.
3553 StgClosure *q = ((StgInd *)p)->indirectee;
3554 if (HEAP_ALLOCED(q) && Bdescr((StgPtr)q)->flags & BF_EVACUATED) {
3557 ((StgInd *)p)->indirectee = evacuate(q);
3560 #if 0 && defined(DEBUG)
3561 if (RtsFlags.DebugFlags.gc)
3562 /* Debugging code to print out the size of the thing we just
3566 StgPtr start = gen->steps[0].scan;
3567 bdescr *start_bd = gen->steps[0].scan_bd;
3569 scavenge(&gen->steps[0]);
3570 if (start_bd != gen->steps[0].scan_bd) {
3571 size += (P_)BLOCK_ROUND_UP(start) - start;
3572 start_bd = start_bd->link;
3573 while (start_bd != gen->steps[0].scan_bd) {
3574 size += BLOCK_SIZE_W;
3575 start_bd = start_bd->link;
3577 size += gen->steps[0].scan -
3578 (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
3580 size = gen->steps[0].scan - start;
3582 debugBelch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
3588 barf("scavenge_one: strange object %d", (int)(info->type));
3591 no_luck = failed_to_evac;
3592 failed_to_evac = rtsFalse;
3596 /* -----------------------------------------------------------------------------
3597 Scavenging mutable lists.
3599 We treat the mutable list of each generation > N (i.e. all the
3600 generations older than the one being collected) as roots. We also
3601 remove non-mutable objects from the mutable list at this point.
3602 -------------------------------------------------------------------------- */
3605 scavenge_mutable_list(generation *gen)
3610 bd = gen->saved_mut_list;
3613 for (; bd != NULL; bd = bd->link) {
3614 for (q = bd->start; q < bd->free; q++) {
3616 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3617 if (scavenge_one(p)) {
3618 /* didn't manage to promote everything, so put the
3619 * object back on the list.
3621 recordMutableGen((StgClosure *)p,gen);
3626 // free the old mut_list
3627 freeChain(gen->saved_mut_list);
3628 gen->saved_mut_list = NULL;
3633 scavenge_static(void)
3635 StgClosure* p = static_objects;
3636 const StgInfoTable *info;
3638 /* Always evacuate straight to the oldest generation for static
3640 evac_gen = oldest_gen->no;
3642 /* keep going until we've scavenged all the objects on the linked
3644 while (p != END_OF_STATIC_LIST) {
3646 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3649 if (info->type==RBH)
3650 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3652 // make sure the info pointer is into text space
3654 /* Take this object *off* the static_objects list,
3655 * and put it on the scavenged_static_objects list.
3657 static_objects = *STATIC_LINK(info,p);
3658 *STATIC_LINK(info,p) = scavenged_static_objects;
3659 scavenged_static_objects = p;
3661 switch (info -> type) {
3665 StgInd *ind = (StgInd *)p;
3666 ind->indirectee = evacuate(ind->indirectee);
3668 /* might fail to evacuate it, in which case we have to pop it
3669 * back on the mutable list of the oldest generation. We
3670 * leave it *on* the scavenged_static_objects list, though,
3671 * in case we visit this object again.
3673 if (failed_to_evac) {
3674 failed_to_evac = rtsFalse;
3675 recordMutableGen((StgClosure *)p,oldest_gen);
3681 scavenge_thunk_srt(info);
3685 scavenge_fun_srt(info);
3692 next = (P_)p->payload + info->layout.payload.ptrs;
3693 // evacuate the pointers
3694 for (q = (P_)p->payload; q < next; q++) {
3695 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3701 barf("scavenge_static: strange closure %d", (int)(info->type));
3704 ASSERT(failed_to_evac == rtsFalse);
3706 /* get the next static object from the list. Remember, there might
3707 * be more stuff on this list now that we've done some evacuating!
3708 * (static_objects is a global)
3714 /* -----------------------------------------------------------------------------
3715 scavenge a chunk of memory described by a bitmap
3716 -------------------------------------------------------------------------- */
3719 scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
3725 bitmap = large_bitmap->bitmap[b];
3726 for (i = 0; i < size; ) {
3727 if ((bitmap & 1) == 0) {
3728 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3732 if (i % BITS_IN(W_) == 0) {
3734 bitmap = large_bitmap->bitmap[b];
3736 bitmap = bitmap >> 1;
3741 STATIC_INLINE StgPtr
3742 scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap)
3745 if ((bitmap & 1) == 0) {
3746 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3749 bitmap = bitmap >> 1;
3755 /* -----------------------------------------------------------------------------
3756 scavenge_stack walks over a section of stack and evacuates all the
3757 objects pointed to by it. We can use the same code for walking
3758 AP_STACK_UPDs, since these are just sections of copied stack.
3759 -------------------------------------------------------------------------- */
3763 scavenge_stack(StgPtr p, StgPtr stack_end)
3765 const StgRetInfoTable* info;
3769 //IF_DEBUG(sanity, debugBelch(" scavenging stack between %p and %p", p, stack_end));
3772 * Each time around this loop, we are looking at a chunk of stack
3773 * that starts with an activation record.
3776 while (p < stack_end) {
3777 info = get_ret_itbl((StgClosure *)p);
3779 switch (info->i.type) {
3782 ((StgUpdateFrame *)p)->updatee
3783 = evacuate(((StgUpdateFrame *)p)->updatee);
3784 p += sizeofW(StgUpdateFrame);
3787 // small bitmap (< 32 entries, or 64 on a 64-bit machine)
3788 case CATCH_STM_FRAME:
3789 case CATCH_RETRY_FRAME:
3790 case ATOMICALLY_FRAME:
3795 bitmap = BITMAP_BITS(info->i.layout.bitmap);
3796 size = BITMAP_SIZE(info->i.layout.bitmap);
3797 // NOTE: the payload starts immediately after the info-ptr, we
3798 // don't have an StgHeader in the same sense as a heap closure.
3800 p = scavenge_small_bitmap(p, size, bitmap);
3803 scavenge_srt((StgClosure **)GET_SRT(info), info->i.srt_bitmap);
3811 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3814 size = BCO_BITMAP_SIZE(bco);
3815 scavenge_large_bitmap(p, BCO_BITMAP(bco), size);
3820 // large bitmap (> 32 entries, or > 64 on a 64-bit machine)
3826 size = GET_LARGE_BITMAP(&info->i)->size;
3828 scavenge_large_bitmap(p, GET_LARGE_BITMAP(&info->i), size);
3830 // and don't forget to follow the SRT
3834 // Dynamic bitmap: the mask is stored on the stack, and
3835 // there are a number of non-pointers followed by a number
3836 // of pointers above the bitmapped area. (see StgMacros.h,
3841 dyn = ((StgRetDyn *)p)->liveness;
3843 // traverse the bitmap first
3844 bitmap = RET_DYN_LIVENESS(dyn);
3845 p = (P_)&((StgRetDyn *)p)->payload[0];
3846 size = RET_DYN_BITMAP_SIZE;
3847 p = scavenge_small_bitmap(p, size, bitmap);
3849 // skip over the non-ptr words
3850 p += RET_DYN_NONPTRS(dyn) + RET_DYN_NONPTR_REGS_SIZE;
3852 // follow the ptr words
3853 for (size = RET_DYN_PTRS(dyn); size > 0; size--) {
3854 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3862 StgRetFun *ret_fun = (StgRetFun *)p;
3863 StgFunInfoTable *fun_info;
3865 ret_fun->fun = evacuate(ret_fun->fun);
3866 fun_info = get_fun_itbl(ret_fun->fun);
3867 p = scavenge_arg_block(fun_info, ret_fun->payload);
3872 barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->i.type));
3877 /*-----------------------------------------------------------------------------
3878 scavenge the large object list.
3880 evac_gen set by caller; similar games played with evac_gen as with
3881 scavenge() - see comment at the top of scavenge(). Most large
3882 objects are (repeatedly) mutable, so most of the time evac_gen will
3884 --------------------------------------------------------------------------- */
3887 scavenge_large(step *stp)
3892 bd = stp->new_large_objects;
3894 for (; bd != NULL; bd = stp->new_large_objects) {
3896 /* take this object *off* the large objects list and put it on
3897 * the scavenged large objects list. This is so that we can
3898 * treat new_large_objects as a stack and push new objects on
3899 * the front when evacuating.
3901 stp->new_large_objects = bd->link;
3902 dbl_link_onto(bd, &stp->scavenged_large_objects);
3904 // update the block count in this step.
3905 stp->n_scavenged_large_blocks += bd->blocks;
3908 if (scavenge_one(p)) {
3909 recordMutableGen((StgClosure *)p, stp->gen);
3914 /* -----------------------------------------------------------------------------
3915 Initialising the static object & mutable lists
3916 -------------------------------------------------------------------------- */
3919 zero_static_object_list(StgClosure* first_static)
3923 const StgInfoTable *info;
3925 for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
3927 link = *STATIC_LINK(info, p);
3928 *STATIC_LINK(info,p) = NULL;
3932 /* -----------------------------------------------------------------------------
3934 -------------------------------------------------------------------------- */
3941 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
3942 c = (StgIndStatic *)c->static_link)
3944 SET_INFO(c, c->saved_info);
3945 c->saved_info = NULL;
3946 // could, but not necessary: c->static_link = NULL;
3948 revertible_caf_list = NULL;
3952 markCAFs( evac_fn evac )
3956 for (c = (StgIndStatic *)caf_list; c != NULL;
3957 c = (StgIndStatic *)c->static_link)
3959 evac(&c->indirectee);
3961 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
3962 c = (StgIndStatic *)c->static_link)
3964 evac(&c->indirectee);
3968 /* -----------------------------------------------------------------------------
3969 Sanity code for CAF garbage collection.
3971 With DEBUG turned on, we manage a CAF list in addition to the SRT
3972 mechanism. After GC, we run down the CAF list and blackhole any
3973 CAFs which have been garbage collected. This means we get an error
3974 whenever the program tries to enter a garbage collected CAF.
3976 Any garbage collected CAFs are taken off the CAF list at the same
3978 -------------------------------------------------------------------------- */
3980 #if 0 && defined(DEBUG)
3987 const StgInfoTable *info;
3998 ASSERT(info->type == IND_STATIC);
4000 if (STATIC_LINK(info,p) == NULL) {
4001 IF_DEBUG(gccafs, debugBelch("CAF gc'd at 0x%04lx", (long)p));
4003 SET_INFO(p,&stg_BLACKHOLE_info);
4004 p = STATIC_LINK2(info,p);
4008 pp = &STATIC_LINK2(info,p);
4015 // debugBelch("%d CAFs live", i);
4020 /* -----------------------------------------------------------------------------
4023 Whenever a thread returns to the scheduler after possibly doing
4024 some work, we have to run down the stack and black-hole all the
4025 closures referred to by update frames.
4026 -------------------------------------------------------------------------- */
4029 threadLazyBlackHole(StgTSO *tso)
4032 StgRetInfoTable *info;
4036 stack_end = &tso->stack[tso->stack_size];
4038 frame = (StgClosure *)tso->sp;
4041 info = get_ret_itbl(frame);
4043 switch (info->i.type) {
4046 bh = ((StgUpdateFrame *)frame)->updatee;
4048 /* if the thunk is already blackholed, it means we've also
4049 * already blackholed the rest of the thunks on this stack,
4050 * so we can stop early.
4052 * The blackhole made for a CAF is a CAF_BLACKHOLE, so they
4053 * don't interfere with this optimisation.
4055 if (bh->header.info == &stg_BLACKHOLE_info) {
4059 if (bh->header.info != &stg_CAF_BLACKHOLE_info) {
4060 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4061 debugBelch("Unexpected lazy BHing required at 0x%04x\n",(int)bh);
4065 // We pretend that bh is now dead.
4066 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4068 SET_INFO(bh,&stg_BLACKHOLE_info);
4070 // We pretend that bh has just been created.
4071 LDV_RECORD_CREATE(bh);
4074 frame = (StgClosure *) ((StgUpdateFrame *)frame + 1);
4080 // normal stack frames; do nothing except advance the pointer
4082 frame = (StgClosure *)((StgPtr)frame + stack_frame_sizeW(frame));
4088 /* -----------------------------------------------------------------------------
4091 * Code largely pinched from old RTS, then hacked to bits. We also do
4092 * lazy black holing here.
4094 * -------------------------------------------------------------------------- */
4096 struct stack_gap { StgWord gap_size; struct stack_gap *next_gap; };
4099 threadSqueezeStack(StgTSO *tso)
4102 rtsBool prev_was_update_frame;
4103 StgClosure *updatee = NULL;
4105 StgRetInfoTable *info;
4106 StgWord current_gap_size;
4107 struct stack_gap *gap;
4110 // Traverse the stack upwards, replacing adjacent update frames
4111 // with a single update frame and a "stack gap". A stack gap
4112 // contains two values: the size of the gap, and the distance
4113 // to the next gap (or the stack top).
4115 bottom = &(tso->stack[tso->stack_size]);
4119 ASSERT(frame < bottom);
4121 prev_was_update_frame = rtsFalse;
4122 current_gap_size = 0;
4123 gap = (struct stack_gap *) (tso->sp - sizeofW(StgUpdateFrame));
4125 while (frame < bottom) {
4127 info = get_ret_itbl((StgClosure *)frame);
4128 switch (info->i.type) {
4132 StgUpdateFrame *upd = (StgUpdateFrame *)frame;
4134 if (upd->updatee->header.info == &stg_BLACKHOLE_info) {
4136 // found a BLACKHOLE'd update frame; we've been here
4137 // before, in a previous GC, so just break out.
4139 // Mark the end of the gap, if we're in one.
4140 if (current_gap_size != 0) {
4141 gap = (struct stack_gap *)(frame-sizeofW(StgUpdateFrame));
4144 frame += sizeofW(StgUpdateFrame);
4145 goto done_traversing;
4148 if (prev_was_update_frame) {
4150 TICK_UPD_SQUEEZED();
4151 /* wasn't there something about update squeezing and ticky to be
4152 * sorted out? oh yes: we aren't counting each enter properly
4153 * in this case. See the log somewhere. KSW 1999-04-21
4155 * Check two things: that the two update frames don't point to
4156 * the same object, and that the updatee_bypass isn't already an
4157 * indirection. Both of these cases only happen when we're in a
4158 * block hole-style loop (and there are multiple update frames
4159 * on the stack pointing to the same closure), but they can both
4160 * screw us up if we don't check.
4162 if (upd->updatee != updatee && !closure_IND(upd->updatee)) {
4163 UPD_IND_NOLOCK(upd->updatee, updatee);
4166 // now mark this update frame as a stack gap. The gap
4167 // marker resides in the bottom-most update frame of
4168 // the series of adjacent frames, and covers all the
4169 // frames in this series.
4170 current_gap_size += sizeofW(StgUpdateFrame);
4171 ((struct stack_gap *)frame)->gap_size = current_gap_size;
4172 ((struct stack_gap *)frame)->next_gap = gap;
4174 frame += sizeofW(StgUpdateFrame);
4178 // single update frame, or the topmost update frame in a series
4180 StgClosure *bh = upd->updatee;
4182 // Do lazy black-holing
4183 if (bh->header.info != &stg_BLACKHOLE_info &&
4184 bh->header.info != &stg_CAF_BLACKHOLE_info) {
4185 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4186 debugBelch("Unexpected lazy BHing required at 0x%04x",(int)bh);
4189 /* zero out the slop so that the sanity checker can tell
4190 * where the next closure is.
4193 StgInfoTable *bh_info = get_itbl(bh);
4194 nat np = bh_info->layout.payload.ptrs,
4195 nw = bh_info->layout.payload.nptrs, i;
4196 /* don't zero out slop for a THUNK_SELECTOR,
4197 * because its layout info is used for a
4198 * different purpose, and it's exactly the
4199 * same size as a BLACKHOLE in any case.
4201 if (bh_info->type != THUNK_SELECTOR) {
4202 for (i = 0; i < np + nw; i++) {
4203 ((StgClosure *)bh)->payload[i] = INVALID_OBJECT;
4209 // We pretend that bh is now dead.
4210 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4212 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
4213 SET_INFO(bh,&stg_BLACKHOLE_info);
4215 // We pretend that bh has just been created.
4216 LDV_RECORD_CREATE(bh);
4219 prev_was_update_frame = rtsTrue;
4220 updatee = upd->updatee;
4221 frame += sizeofW(StgUpdateFrame);
4227 prev_was_update_frame = rtsFalse;
4229 // we're not in a gap... check whether this is the end of a gap
4230 // (an update frame can't be the end of a gap).
4231 if (current_gap_size != 0) {
4232 gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
4234 current_gap_size = 0;
4236 frame += stack_frame_sizeW((StgClosure *)frame);
4243 // Now we have a stack with gaps in it, and we have to walk down
4244 // shoving the stack up to fill in the gaps. A diagram might
4248 // | ********* | <- sp
4252 // | stack_gap | <- gap | chunk_size
4254 // | ......... | <- gap_end v
4260 // 'sp' points the the current top-of-stack
4261 // 'gap' points to the stack_gap structure inside the gap
4262 // ***** indicates real stack data
4263 // ..... indicates gap
4264 // <empty> indicates unused
4268 void *gap_start, *next_gap_start, *gap_end;
4271 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4272 sp = next_gap_start;
4274 while ((StgPtr)gap > tso->sp) {
4276 // we're working in *bytes* now...
4277 gap_start = next_gap_start;
4278 gap_end = (void*) ((unsigned char*)gap_start - gap->gap_size * sizeof(W_));
4280 gap = gap->next_gap;
4281 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4283 chunk_size = (unsigned char*)gap_end - (unsigned char*)next_gap_start;
4285 memmove(sp, next_gap_start, chunk_size);
4288 tso->sp = (StgPtr)sp;
4292 /* -----------------------------------------------------------------------------
4295 * We have to prepare for GC - this means doing lazy black holing
4296 * here. We also take the opportunity to do stack squeezing if it's
4298 * -------------------------------------------------------------------------- */
4300 threadPaused(StgTSO *tso)
4302 if ( RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue )
4303 threadSqueezeStack(tso); // does black holing too
4305 threadLazyBlackHole(tso);
4308 /* -----------------------------------------------------------------------------
4310 * -------------------------------------------------------------------------- */
4314 printMutableList(generation *gen)
4319 debugBelch("@@ Mutable list %p: ", gen->mut_list);
4321 for (bd = gen->mut_list; bd != NULL; bd = bd->link) {
4322 for (p = bd->start; p < bd->free; p++) {
4323 debugBelch("%p (%s), ", (void *)*p, info_type((StgClosure *)*p));