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 if (g == 0 && s == 0) {
743 collected += countNurseryBlocks() * BLOCK_SIZE_W;
744 collected += alloc_blocks;
746 collected += stp->n_blocks * BLOCK_SIZE_W;
750 /* free old memory and shift to-space into from-space for all
751 * the collected steps (except the allocation area). These
752 * freed blocks will probaby be quickly recycled.
754 if (!(g == 0 && s == 0)) {
755 if (stp->is_compacted) {
756 // for a compacted step, just shift the new to-space
757 // onto the front of the now-compacted existing blocks.
758 for (bd = stp->to_blocks; bd != NULL; bd = bd->link) {
759 bd->flags &= ~BF_EVACUATED; // now from-space
761 // tack the new blocks on the end of the existing blocks
762 if (stp->blocks == NULL) {
763 stp->blocks = stp->to_blocks;
765 for (bd = stp->blocks; bd != NULL; bd = next) {
768 bd->link = stp->to_blocks;
770 // NB. this step might not be compacted next
771 // time, so reset the BF_COMPACTED flags.
772 // They are set before GC if we're going to
773 // compact. (search for BF_COMPACTED above).
774 bd->flags &= ~BF_COMPACTED;
777 // add the new blocks to the block tally
778 stp->n_blocks += stp->n_to_blocks;
780 freeChain(stp->blocks);
781 stp->blocks = stp->to_blocks;
782 stp->n_blocks = stp->n_to_blocks;
783 for (bd = stp->blocks; bd != NULL; bd = bd->link) {
784 bd->flags &= ~BF_EVACUATED; // now from-space
787 stp->to_blocks = NULL;
788 stp->n_to_blocks = 0;
791 /* LARGE OBJECTS. The current live large objects are chained on
792 * scavenged_large, having been moved during garbage
793 * collection from large_objects. Any objects left on
794 * large_objects list are therefore dead, so we free them here.
796 for (bd = stp->large_objects; bd != NULL; bd = next) {
802 // update the count of blocks used by large objects
803 for (bd = stp->scavenged_large_objects; bd != NULL; bd = bd->link) {
804 bd->flags &= ~BF_EVACUATED;
806 stp->large_objects = stp->scavenged_large_objects;
807 stp->n_large_blocks = stp->n_scavenged_large_blocks;
810 // for older generations...
812 /* For older generations, we need to append the
813 * scavenged_large_object list (i.e. large objects that have been
814 * promoted during this GC) to the large_object list for that step.
816 for (bd = stp->scavenged_large_objects; bd; bd = next) {
818 bd->flags &= ~BF_EVACUATED;
819 dbl_link_onto(bd, &stp->large_objects);
822 // add the new blocks we promoted during this GC
823 stp->n_blocks += stp->n_to_blocks;
824 stp->n_to_blocks = 0;
825 stp->n_large_blocks += stp->n_scavenged_large_blocks;
830 /* Reset the sizes of the older generations when we do a major
833 * CURRENT STRATEGY: make all generations except zero the same size.
834 * We have to stay within the maximum heap size, and leave a certain
835 * percentage of the maximum heap size available to allocate into.
837 if (major_gc && RtsFlags.GcFlags.generations > 1) {
838 nat live, size, min_alloc;
839 nat max = RtsFlags.GcFlags.maxHeapSize;
840 nat gens = RtsFlags.GcFlags.generations;
842 // live in the oldest generations
843 live = oldest_gen->steps[0].n_blocks +
844 oldest_gen->steps[0].n_large_blocks;
846 // default max size for all generations except zero
847 size = stg_max(live * RtsFlags.GcFlags.oldGenFactor,
848 RtsFlags.GcFlags.minOldGenSize);
850 // minimum size for generation zero
851 min_alloc = stg_max((RtsFlags.GcFlags.pcFreeHeap * max) / 200,
852 RtsFlags.GcFlags.minAllocAreaSize);
854 // Auto-enable compaction when the residency reaches a
855 // certain percentage of the maximum heap size (default: 30%).
856 if (RtsFlags.GcFlags.generations > 1 &&
857 (RtsFlags.GcFlags.compact ||
859 oldest_gen->steps[0].n_blocks >
860 (RtsFlags.GcFlags.compactThreshold * max) / 100))) {
861 oldest_gen->steps[0].is_compacted = 1;
862 // debugBelch("compaction: on\n", live);
864 oldest_gen->steps[0].is_compacted = 0;
865 // debugBelch("compaction: off\n", live);
868 // if we're going to go over the maximum heap size, reduce the
869 // size of the generations accordingly. The calculation is
870 // different if compaction is turned on, because we don't need
871 // to double the space required to collect the old generation.
874 // this test is necessary to ensure that the calculations
875 // below don't have any negative results - we're working
876 // with unsigned values here.
877 if (max < min_alloc) {
881 if (oldest_gen->steps[0].is_compacted) {
882 if ( (size + (size - 1) * (gens - 2) * 2) + min_alloc > max ) {
883 size = (max - min_alloc) / ((gens - 1) * 2 - 1);
886 if ( (size * (gens - 1) * 2) + min_alloc > max ) {
887 size = (max - min_alloc) / ((gens - 1) * 2);
897 debugBelch("live: %d, min_alloc: %d, size : %d, max = %d\n", live,
898 min_alloc, size, max);
901 for (g = 0; g < gens; g++) {
902 generations[g].max_blocks = size;
906 // Guess the amount of live data for stats.
909 /* Free the small objects allocated via allocate(), since this will
910 * all have been copied into G0S1 now.
912 if (small_alloc_list != NULL) {
913 freeChain(small_alloc_list);
915 small_alloc_list = NULL;
919 alloc_blocks_lim = RtsFlags.GcFlags.minAllocAreaSize;
921 // Start a new pinned_object_block
922 pinned_object_block = NULL;
924 /* Free the mark stack.
926 if (mark_stack_bdescr != NULL) {
927 freeGroup(mark_stack_bdescr);
932 for (g = 0; g <= N; g++) {
933 for (s = 0; s < generations[g].n_steps; s++) {
934 stp = &generations[g].steps[s];
935 if (stp->is_compacted && stp->bitmap != NULL) {
936 freeGroup(stp->bitmap);
941 /* Two-space collector:
942 * Free the old to-space, and estimate the amount of live data.
944 if (RtsFlags.GcFlags.generations == 1) {
947 if (old_to_blocks != NULL) {
948 freeChain(old_to_blocks);
950 for (bd = g0s0->to_blocks; bd != NULL; bd = bd->link) {
951 bd->flags = 0; // now from-space
954 /* For a two-space collector, we need to resize the nursery. */
956 /* set up a new nursery. Allocate a nursery size based on a
957 * function of the amount of live data (by default a factor of 2)
958 * Use the blocks from the old nursery if possible, freeing up any
961 * If we get near the maximum heap size, then adjust our nursery
962 * size accordingly. If the nursery is the same size as the live
963 * data (L), then we need 3L bytes. We can reduce the size of the
964 * nursery to bring the required memory down near 2L bytes.
966 * A normal 2-space collector would need 4L bytes to give the same
967 * performance we get from 3L bytes, reducing to the same
968 * performance at 2L bytes.
970 blocks = g0s0->n_to_blocks;
972 if ( RtsFlags.GcFlags.maxHeapSize != 0 &&
973 blocks * RtsFlags.GcFlags.oldGenFactor * 2 >
974 RtsFlags.GcFlags.maxHeapSize ) {
975 long adjusted_blocks; // signed on purpose
978 adjusted_blocks = (RtsFlags.GcFlags.maxHeapSize - 2 * blocks);
979 IF_DEBUG(gc, debugBelch("@@ Near maximum heap size of 0x%x blocks, blocks = %d, adjusted to %ld", RtsFlags.GcFlags.maxHeapSize, blocks, adjusted_blocks));
980 pc_free = adjusted_blocks * 100 / RtsFlags.GcFlags.maxHeapSize;
981 if (pc_free < RtsFlags.GcFlags.pcFreeHeap) /* might even be < 0 */ {
984 blocks = adjusted_blocks;
987 blocks *= RtsFlags.GcFlags.oldGenFactor;
988 if (blocks < RtsFlags.GcFlags.minAllocAreaSize) {
989 blocks = RtsFlags.GcFlags.minAllocAreaSize;
992 resizeNurseries(blocks);
995 /* Generational collector:
996 * If the user has given us a suggested heap size, adjust our
997 * allocation area to make best use of the memory available.
1000 if (RtsFlags.GcFlags.heapSizeSuggestion) {
1002 nat needed = calcNeeded(); // approx blocks needed at next GC
1004 /* Guess how much will be live in generation 0 step 0 next time.
1005 * A good approximation is obtained by finding the
1006 * percentage of g0s0 that was live at the last minor GC.
1009 g0s0_pcnt_kept = (new_blocks * 100) / countNurseryBlocks();
1012 /* Estimate a size for the allocation area based on the
1013 * information available. We might end up going slightly under
1014 * or over the suggested heap size, but we should be pretty
1017 * Formula: suggested - needed
1018 * ----------------------------
1019 * 1 + g0s0_pcnt_kept/100
1021 * where 'needed' is the amount of memory needed at the next
1022 * collection for collecting all steps except g0s0.
1025 (((long)RtsFlags.GcFlags.heapSizeSuggestion - (long)needed) * 100) /
1026 (100 + (long)g0s0_pcnt_kept);
1028 if (blocks < (long)RtsFlags.GcFlags.minAllocAreaSize) {
1029 blocks = RtsFlags.GcFlags.minAllocAreaSize;
1032 resizeNurseries((nat)blocks);
1035 // we might have added extra large blocks to the nursery, so
1036 // resize back to minAllocAreaSize again.
1037 resizeNurseriesFixed(RtsFlags.GcFlags.minAllocAreaSize);
1041 // mark the garbage collected CAFs as dead
1042 #if 0 && defined(DEBUG) // doesn't work at the moment
1043 if (major_gc) { gcCAFs(); }
1047 // resetStaticObjectForRetainerProfiling() must be called before
1049 resetStaticObjectForRetainerProfiling();
1052 // zero the scavenged static object list
1054 zero_static_object_list(scavenged_static_objects);
1057 // Reset the nursery
1060 RELEASE_LOCK(&sched_mutex);
1062 // start any pending finalizers
1063 scheduleFinalizers(old_weak_ptr_list);
1065 // send exceptions to any threads which were about to die
1066 resurrectThreads(resurrected_threads);
1068 ACQUIRE_LOCK(&sched_mutex);
1070 // Update the stable pointer hash table.
1071 updateStablePtrTable(major_gc);
1073 // check sanity after GC
1074 IF_DEBUG(sanity, checkSanity());
1076 // extra GC trace info
1077 IF_DEBUG(gc, statDescribeGens());
1080 // symbol-table based profiling
1081 /* heapCensus(to_blocks); */ /* ToDo */
1084 // restore enclosing cost centre
1089 // check for memory leaks if sanity checking is on
1090 IF_DEBUG(sanity, memInventory());
1092 #ifdef RTS_GTK_FRONTPANEL
1093 if (RtsFlags.GcFlags.frontpanel) {
1094 updateFrontPanelAfterGC( N, live );
1098 // ok, GC over: tell the stats department what happened.
1099 stat_endGC(allocated, collected, live, copied, N);
1101 #if defined(RTS_USER_SIGNALS)
1102 // unblock signals again
1103 unblockUserSignals();
1110 /* -----------------------------------------------------------------------------
1113 traverse_weak_ptr_list is called possibly many times during garbage
1114 collection. It returns a flag indicating whether it did any work
1115 (i.e. called evacuate on any live pointers).
1117 Invariant: traverse_weak_ptr_list is called when the heap is in an
1118 idempotent state. That means that there are no pending
1119 evacuate/scavenge operations. This invariant helps the weak
1120 pointer code decide which weak pointers are dead - if there are no
1121 new live weak pointers, then all the currently unreachable ones are
1124 For generational GC: we just don't try to finalize weak pointers in
1125 older generations than the one we're collecting. This could
1126 probably be optimised by keeping per-generation lists of weak
1127 pointers, but for a few weak pointers this scheme will work.
1129 There are three distinct stages to processing weak pointers:
1131 - weak_stage == WeakPtrs
1133 We process all the weak pointers whos keys are alive (evacuate
1134 their values and finalizers), and repeat until we can find no new
1135 live keys. If no live keys are found in this pass, then we
1136 evacuate the finalizers of all the dead weak pointers in order to
1139 - weak_stage == WeakThreads
1141 Now, we discover which *threads* are still alive. Pointers to
1142 threads from the all_threads and main thread lists are the
1143 weakest of all: a pointers from the finalizer of a dead weak
1144 pointer can keep a thread alive. Any threads found to be unreachable
1145 are evacuated and placed on the resurrected_threads list so we
1146 can send them a signal later.
1148 - weak_stage == WeakDone
1150 No more evacuation is done.
1152 -------------------------------------------------------------------------- */
1155 traverse_weak_ptr_list(void)
1157 StgWeak *w, **last_w, *next_w;
1159 rtsBool flag = rtsFalse;
1161 switch (weak_stage) {
1167 /* doesn't matter where we evacuate values/finalizers to, since
1168 * these pointers are treated as roots (iff the keys are alive).
1172 last_w = &old_weak_ptr_list;
1173 for (w = old_weak_ptr_list; w != NULL; w = next_w) {
1175 /* There might be a DEAD_WEAK on the list if finalizeWeak# was
1176 * called on a live weak pointer object. Just remove it.
1178 if (w->header.info == &stg_DEAD_WEAK_info) {
1179 next_w = ((StgDeadWeak *)w)->link;
1184 switch (get_itbl(w)->type) {
1187 next_w = (StgWeak *)((StgEvacuated *)w)->evacuee;
1192 /* Now, check whether the key is reachable.
1194 new = isAlive(w->key);
1197 // evacuate the value and finalizer
1198 w->value = evacuate(w->value);
1199 w->finalizer = evacuate(w->finalizer);
1200 // remove this weak ptr from the old_weak_ptr list
1202 // and put it on the new weak ptr list
1204 w->link = weak_ptr_list;
1207 IF_DEBUG(weak, debugBelch("Weak pointer still alive at %p -> %p",
1212 last_w = &(w->link);
1218 barf("traverse_weak_ptr_list: not WEAK");
1222 /* If we didn't make any changes, then we can go round and kill all
1223 * the dead weak pointers. The old_weak_ptr list is used as a list
1224 * of pending finalizers later on.
1226 if (flag == rtsFalse) {
1227 for (w = old_weak_ptr_list; w; w = w->link) {
1228 w->finalizer = evacuate(w->finalizer);
1231 // Next, move to the WeakThreads stage after fully
1232 // scavenging the finalizers we've just evacuated.
1233 weak_stage = WeakThreads;
1239 /* Now deal with the all_threads list, which behaves somewhat like
1240 * the weak ptr list. If we discover any threads that are about to
1241 * become garbage, we wake them up and administer an exception.
1244 StgTSO *t, *tmp, *next, **prev;
1246 prev = &old_all_threads;
1247 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1249 tmp = (StgTSO *)isAlive((StgClosure *)t);
1255 ASSERT(get_itbl(t)->type == TSO);
1256 switch (t->what_next) {
1257 case ThreadRelocated:
1262 case ThreadComplete:
1263 // finshed or died. The thread might still be alive, but we
1264 // don't keep it on the all_threads list. Don't forget to
1265 // stub out its global_link field.
1266 next = t->global_link;
1267 t->global_link = END_TSO_QUEUE;
1274 // Threads blocked on black holes: if the black hole
1275 // is alive, then the thread is alive too.
1276 if (tmp == NULL && t->why_blocked == BlockedOnBlackHole) {
1277 if (isAlive(t->block_info.closure)) {
1278 t = (StgTSO *)evacuate((StgClosure *)t);
1285 // not alive (yet): leave this thread on the
1286 // old_all_threads list.
1287 prev = &(t->global_link);
1288 next = t->global_link;
1291 // alive: move this thread onto the all_threads list.
1292 next = t->global_link;
1293 t->global_link = all_threads;
1300 /* If we evacuated any threads, we need to go back to the scavenger.
1302 if (flag) return rtsTrue;
1304 /* And resurrect any threads which were about to become garbage.
1307 StgTSO *t, *tmp, *next;
1308 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1309 next = t->global_link;
1310 tmp = (StgTSO *)evacuate((StgClosure *)t);
1311 tmp->global_link = resurrected_threads;
1312 resurrected_threads = tmp;
1316 /* Finally, we can update the blackhole_queue. This queue
1317 * simply strings together TSOs blocked on black holes, it is
1318 * not intended to keep anything alive. Hence, we do not follow
1319 * pointers on the blackhole_queue until now, when we have
1320 * determined which TSOs are otherwise reachable. We know at
1321 * this point that all TSOs have been evacuated, however.
1325 for (pt = &blackhole_queue; *pt != END_TSO_QUEUE; pt = &((*pt)->link)) {
1326 *pt = (StgTSO *)isAlive((StgClosure *)*pt);
1327 ASSERT(*pt != NULL);
1331 weak_stage = WeakDone; // *now* we're done,
1332 return rtsTrue; // but one more round of scavenging, please
1335 barf("traverse_weak_ptr_list");
1341 /* -----------------------------------------------------------------------------
1342 After GC, the live weak pointer list may have forwarding pointers
1343 on it, because a weak pointer object was evacuated after being
1344 moved to the live weak pointer list. We remove those forwarding
1347 Also, we don't consider weak pointer objects to be reachable, but
1348 we must nevertheless consider them to be "live" and retain them.
1349 Therefore any weak pointer objects which haven't as yet been
1350 evacuated need to be evacuated now.
1351 -------------------------------------------------------------------------- */
1355 mark_weak_ptr_list ( StgWeak **list )
1357 StgWeak *w, **last_w;
1360 for (w = *list; w; w = w->link) {
1361 // w might be WEAK, EVACUATED, or DEAD_WEAK (actually CON_STATIC) here
1362 ASSERT(w->header.info == &stg_DEAD_WEAK_info
1363 || get_itbl(w)->type == WEAK || get_itbl(w)->type == EVACUATED);
1364 w = (StgWeak *)evacuate((StgClosure *)w);
1366 last_w = &(w->link);
1370 /* -----------------------------------------------------------------------------
1371 isAlive determines whether the given closure is still alive (after
1372 a garbage collection) or not. It returns the new address of the
1373 closure if it is alive, or NULL otherwise.
1375 NOTE: Use it before compaction only!
1376 -------------------------------------------------------------------------- */
1380 isAlive(StgClosure *p)
1382 const StgInfoTable *info;
1387 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
1390 // ignore static closures
1392 // ToDo: for static closures, check the static link field.
1393 // Problem here is that we sometimes don't set the link field, eg.
1394 // for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
1396 if (!HEAP_ALLOCED(p)) {
1400 // ignore closures in generations that we're not collecting.
1402 if (bd->gen_no > N) {
1406 // if it's a pointer into to-space, then we're done
1407 if (bd->flags & BF_EVACUATED) {
1411 // large objects use the evacuated flag
1412 if (bd->flags & BF_LARGE) {
1416 // check the mark bit for compacted steps
1417 if ((bd->flags & BF_COMPACTED) && is_marked((P_)p,bd)) {
1421 switch (info->type) {
1426 case IND_OLDGEN: // rely on compatible layout with StgInd
1427 case IND_OLDGEN_PERM:
1428 // follow indirections
1429 p = ((StgInd *)p)->indirectee;
1434 return ((StgEvacuated *)p)->evacuee;
1437 if (((StgTSO *)p)->what_next == ThreadRelocated) {
1438 p = (StgClosure *)((StgTSO *)p)->link;
1451 mark_root(StgClosure **root)
1453 *root = evacuate(*root);
1457 upd_evacuee(StgClosure *p, StgClosure *dest)
1459 // not true: (ToDo: perhaps it should be)
1460 // ASSERT(Bdescr((P_)dest)->flags & BF_EVACUATED);
1461 SET_INFO(p, &stg_EVACUATED_info);
1462 ((StgEvacuated *)p)->evacuee = dest;
1466 STATIC_INLINE StgClosure *
1467 copy(StgClosure *src, nat size, step *stp)
1472 nat size_org = size;
1475 TICK_GC_WORDS_COPIED(size);
1476 /* Find out where we're going, using the handy "to" pointer in
1477 * the step of the source object. If it turns out we need to
1478 * evacuate to an older generation, adjust it here (see comment
1481 if (stp->gen_no < evac_gen) {
1482 #ifdef NO_EAGER_PROMOTION
1483 failed_to_evac = rtsTrue;
1485 stp = &generations[evac_gen].steps[0];
1489 /* chain a new block onto the to-space for the destination step if
1492 if (stp->hp + size >= stp->hpLim) {
1493 gc_alloc_block(stp);
1496 for(to = stp->hp, from = (P_)src; size>0; --size) {
1502 upd_evacuee(src,(StgClosure *)dest);
1504 // We store the size of the just evacuated object in the LDV word so that
1505 // the profiler can guess the position of the next object later.
1506 SET_EVACUAEE_FOR_LDV(src, size_org);
1508 return (StgClosure *)dest;
1511 /* Special version of copy() for when we only want to copy the info
1512 * pointer of an object, but reserve some padding after it. This is
1513 * used to optimise evacuation of BLACKHOLEs.
1518 copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *stp)
1523 nat size_to_copy_org = size_to_copy;
1526 TICK_GC_WORDS_COPIED(size_to_copy);
1527 if (stp->gen_no < evac_gen) {
1528 #ifdef NO_EAGER_PROMOTION
1529 failed_to_evac = rtsTrue;
1531 stp = &generations[evac_gen].steps[0];
1535 if (stp->hp + size_to_reserve >= stp->hpLim) {
1536 gc_alloc_block(stp);
1539 for(to = stp->hp, from = (P_)src; size_to_copy>0; --size_to_copy) {
1544 stp->hp += size_to_reserve;
1545 upd_evacuee(src,(StgClosure *)dest);
1547 // We store the size of the just evacuated object in the LDV word so that
1548 // the profiler can guess the position of the next object later.
1549 // size_to_copy_org is wrong because the closure already occupies size_to_reserve
1551 SET_EVACUAEE_FOR_LDV(src, size_to_reserve);
1553 if (size_to_reserve - size_to_copy_org > 0)
1554 FILL_SLOP(stp->hp - 1, (int)(size_to_reserve - size_to_copy_org));
1556 return (StgClosure *)dest;
1560 /* -----------------------------------------------------------------------------
1561 Evacuate a large object
1563 This just consists of removing the object from the (doubly-linked)
1564 step->large_objects list, and linking it on to the (singly-linked)
1565 step->new_large_objects list, from where it will be scavenged later.
1567 Convention: bd->flags has BF_EVACUATED set for a large object
1568 that has been evacuated, or unset otherwise.
1569 -------------------------------------------------------------------------- */
1573 evacuate_large(StgPtr p)
1575 bdescr *bd = Bdescr(p);
1578 // object must be at the beginning of the block (or be a ByteArray)
1579 ASSERT(get_itbl((StgClosure *)p)->type == ARR_WORDS ||
1580 (((W_)p & BLOCK_MASK) == 0));
1582 // already evacuated?
1583 if (bd->flags & BF_EVACUATED) {
1584 /* Don't forget to set the failed_to_evac flag if we didn't get
1585 * the desired destination (see comments in evacuate()).
1587 if (bd->gen_no < evac_gen) {
1588 failed_to_evac = rtsTrue;
1589 TICK_GC_FAILED_PROMOTION();
1595 // remove from large_object list
1597 bd->u.back->link = bd->link;
1598 } else { // first object in the list
1599 stp->large_objects = bd->link;
1602 bd->link->u.back = bd->u.back;
1605 /* link it on to the evacuated large object list of the destination step
1608 if (stp->gen_no < evac_gen) {
1609 #ifdef NO_EAGER_PROMOTION
1610 failed_to_evac = rtsTrue;
1612 stp = &generations[evac_gen].steps[0];
1617 bd->gen_no = stp->gen_no;
1618 bd->link = stp->new_large_objects;
1619 stp->new_large_objects = bd;
1620 bd->flags |= BF_EVACUATED;
1623 /* -----------------------------------------------------------------------------
1626 This is called (eventually) for every live object in the system.
1628 The caller to evacuate specifies a desired generation in the
1629 evac_gen global variable. The following conditions apply to
1630 evacuating an object which resides in generation M when we're
1631 collecting up to generation N
1635 else evac to step->to
1637 if M < evac_gen evac to evac_gen, step 0
1639 if the object is already evacuated, then we check which generation
1642 if M >= evac_gen do nothing
1643 if M < evac_gen set failed_to_evac flag to indicate that we
1644 didn't manage to evacuate this object into evac_gen.
1649 evacuate() is the single most important function performance-wise
1650 in the GC. Various things have been tried to speed it up, but as
1651 far as I can tell the code generated by gcc 3.2 with -O2 is about
1652 as good as it's going to get. We pass the argument to evacuate()
1653 in a register using the 'regparm' attribute (see the prototype for
1654 evacuate() near the top of this file).
1656 Changing evacuate() to take an (StgClosure **) rather than
1657 returning the new pointer seems attractive, because we can avoid
1658 writing back the pointer when it hasn't changed (eg. for a static
1659 object, or an object in a generation > N). However, I tried it and
1660 it doesn't help. One reason is that the (StgClosure **) pointer
1661 gets spilled to the stack inside evacuate(), resulting in far more
1662 extra reads/writes than we save.
1663 -------------------------------------------------------------------------- */
1665 REGPARM1 static StgClosure *
1666 evacuate(StgClosure *q)
1673 const StgInfoTable *info;
1676 if (HEAP_ALLOCED(q)) {
1679 if (bd->gen_no > N) {
1680 /* Can't evacuate this object, because it's in a generation
1681 * older than the ones we're collecting. Let's hope that it's
1682 * in evac_gen or older, or we will have to arrange to track
1683 * this pointer using the mutable list.
1685 if (bd->gen_no < evac_gen) {
1687 failed_to_evac = rtsTrue;
1688 TICK_GC_FAILED_PROMOTION();
1693 /* evacuate large objects by re-linking them onto a different list.
1695 if (bd->flags & BF_LARGE) {
1697 if (info->type == TSO &&
1698 ((StgTSO *)q)->what_next == ThreadRelocated) {
1699 q = (StgClosure *)((StgTSO *)q)->link;
1702 evacuate_large((P_)q);
1706 /* If the object is in a step that we're compacting, then we
1707 * need to use an alternative evacuate procedure.
1709 if (bd->flags & BF_COMPACTED) {
1710 if (!is_marked((P_)q,bd)) {
1712 if (mark_stack_full()) {
1713 mark_stack_overflowed = rtsTrue;
1716 push_mark_stack((P_)q);
1721 /* Object is not already evacuated. */
1722 ASSERT((bd->flags & BF_EVACUATED) == 0);
1727 else stp = NULL; // make sure copy() will crash if HEAP_ALLOCED is wrong
1730 // make sure the info pointer is into text space
1731 ASSERT(LOOKS_LIKE_CLOSURE_PTR(q));
1734 switch (info -> type) {
1738 return copy(q,sizeW_fromITBL(info),stp);
1742 StgWord w = (StgWord)q->payload[0];
1743 if (q->header.info == Czh_con_info &&
1744 // unsigned, so always true: (StgChar)w >= MIN_CHARLIKE &&
1745 (StgChar)w <= MAX_CHARLIKE) {
1746 return (StgClosure *)CHARLIKE_CLOSURE((StgChar)w);
1748 if (q->header.info == Izh_con_info &&
1749 (StgInt)w >= MIN_INTLIKE && (StgInt)w <= MAX_INTLIKE) {
1750 return (StgClosure *)INTLIKE_CLOSURE((StgInt)w);
1752 // else, fall through ...
1758 return copy(q,sizeofW(StgHeader)+1,stp);
1762 return copy(q,sizeofW(StgThunk)+1,stp);
1767 #ifdef NO_PROMOTE_THUNKS
1768 if (bd->gen_no == 0 &&
1769 bd->step->no != 0 &&
1770 bd->step->no == generations[bd->gen_no].n_steps-1) {
1774 return copy(q,sizeofW(StgThunk)+2,stp);
1782 return copy(q,sizeofW(StgHeader)+2,stp);
1785 return copy(q,thunk_sizeW_fromITBL(info),stp);
1790 case IND_OLDGEN_PERM:
1794 return copy(q,sizeW_fromITBL(info),stp);
1797 return copy(q,bco_sizeW((StgBCO *)q),stp);
1800 case SE_CAF_BLACKHOLE:
1803 return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
1805 case THUNK_SELECTOR:
1809 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
1810 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1813 p = eval_thunk_selector(info->layout.selector_offset,
1817 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1819 // q is still BLACKHOLE'd.
1820 thunk_selector_depth++;
1822 thunk_selector_depth--;
1825 // We store the size of the just evacuated object in the
1826 // LDV word so that the profiler can guess the position of
1827 // the next object later.
1828 SET_EVACUAEE_FOR_LDV(q, THUNK_SELECTOR_sizeW());
1836 // follow chains of indirections, don't evacuate them
1837 q = ((StgInd*)q)->indirectee;
1841 if (info->srt_bitmap != 0 && major_gc &&
1842 *THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
1843 *THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
1844 static_objects = (StgClosure *)q;
1849 if (info->srt_bitmap != 0 && major_gc &&
1850 *FUN_STATIC_LINK((StgClosure *)q) == NULL) {
1851 *FUN_STATIC_LINK((StgClosure *)q) = static_objects;
1852 static_objects = (StgClosure *)q;
1857 /* If q->saved_info != NULL, then it's a revertible CAF - it'll be
1858 * on the CAF list, so don't do anything with it here (we'll
1859 * scavenge it later).
1862 && ((StgIndStatic *)q)->saved_info == NULL
1863 && *IND_STATIC_LINK((StgClosure *)q) == NULL) {
1864 *IND_STATIC_LINK((StgClosure *)q) = static_objects;
1865 static_objects = (StgClosure *)q;
1870 if (major_gc && *STATIC_LINK(info,(StgClosure *)q) == NULL) {
1871 *STATIC_LINK(info,(StgClosure *)q) = static_objects;
1872 static_objects = (StgClosure *)q;
1876 case CONSTR_INTLIKE:
1877 case CONSTR_CHARLIKE:
1878 case CONSTR_NOCAF_STATIC:
1879 /* no need to put these on the static linked list, they don't need
1893 case CATCH_STM_FRAME:
1894 case CATCH_RETRY_FRAME:
1895 case ATOMICALLY_FRAME:
1896 // shouldn't see these
1897 barf("evacuate: stack frame at %p\n", q);
1900 return copy(q,pap_sizeW((StgPAP*)q),stp);
1903 return copy(q,ap_sizeW((StgAP*)q),stp);
1906 return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp);
1909 /* Already evacuated, just return the forwarding address.
1910 * HOWEVER: if the requested destination generation (evac_gen) is
1911 * older than the actual generation (because the object was
1912 * already evacuated to a younger generation) then we have to
1913 * set the failed_to_evac flag to indicate that we couldn't
1914 * manage to promote the object to the desired generation.
1916 if (evac_gen > 0) { // optimisation
1917 StgClosure *p = ((StgEvacuated*)q)->evacuee;
1918 if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < evac_gen) {
1919 failed_to_evac = rtsTrue;
1920 TICK_GC_FAILED_PROMOTION();
1923 return ((StgEvacuated*)q)->evacuee;
1926 // just copy the block
1927 return copy(q,arr_words_sizeW((StgArrWords *)q),stp);
1930 case MUT_ARR_PTRS_FROZEN:
1931 case MUT_ARR_PTRS_FROZEN0:
1932 // just copy the block
1933 return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
1937 StgTSO *tso = (StgTSO *)q;
1939 /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
1941 if (tso->what_next == ThreadRelocated) {
1942 q = (StgClosure *)tso->link;
1946 /* To evacuate a small TSO, we need to relocate the update frame
1953 new_tso = (StgTSO *)copyPart((StgClosure *)tso,
1955 sizeofW(StgTSO), stp);
1956 move_TSO(tso, new_tso);
1957 for (p = tso->sp, q = new_tso->sp;
1958 p < tso->stack+tso->stack_size;) {
1962 return (StgClosure *)new_tso;
1969 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
1970 to = copy(q,BLACKHOLE_sizeW(),stp);
1971 //ToDo: derive size etc from reverted IP
1972 //to = copy(q,size,stp);
1974 debugBelch("@@ evacuate: RBH %p (%s) to %p (%s)",
1975 q, info_type(q), to, info_type(to)));
1980 ASSERT(sizeofW(StgBlockedFetch) >= MIN_NONUPD_SIZE);
1981 to = copy(q,sizeofW(StgBlockedFetch),stp);
1983 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
1984 q, info_type(q), to, info_type(to)));
1991 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1992 to = copy(q,sizeofW(StgFetchMe),stp);
1994 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
1995 q, info_type(q), to, info_type(to)));
1999 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
2000 to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
2002 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
2003 q, info_type(q), to, info_type(to)));
2008 return copy(q,sizeofW(StgTRecHeader),stp);
2010 case TVAR_WAIT_QUEUE:
2011 return copy(q,sizeofW(StgTVarWaitQueue),stp);
2014 return copy(q,sizeofW(StgTVar),stp);
2017 return copy(q,sizeofW(StgTRecChunk),stp);
2020 barf("evacuate: strange closure type %d", (int)(info->type));
2026 /* -----------------------------------------------------------------------------
2027 Evaluate a THUNK_SELECTOR if possible.
2029 returns: NULL if we couldn't evaluate this THUNK_SELECTOR, or
2030 a closure pointer if we evaluated it and this is the result. Note
2031 that "evaluating" the THUNK_SELECTOR doesn't necessarily mean
2032 reducing it to HNF, just that we have eliminated the selection.
2033 The result might be another thunk, or even another THUNK_SELECTOR.
2035 If the return value is non-NULL, the original selector thunk has
2036 been BLACKHOLE'd, and should be updated with an indirection or a
2037 forwarding pointer. If the return value is NULL, then the selector
2041 ToDo: the treatment of THUNK_SELECTORS could be improved in the
2042 following way (from a suggestion by Ian Lynagh):
2044 We can have a chain like this:
2048 |-----> sel_0 --> (a,b)
2050 |-----> sel_0 --> ...
2052 and the depth limit means we don't go all the way to the end of the
2053 chain, which results in a space leak. This affects the recursive
2054 call to evacuate() in the THUNK_SELECTOR case in evacuate(): *not*
2055 the recursive call to eval_thunk_selector() in
2056 eval_thunk_selector().
2058 We could eliminate the depth bound in this case, in the following
2061 - traverse the chain once to discover the *value* of the
2062 THUNK_SELECTOR. Mark all THUNK_SELECTORS that we
2063 visit on the way as having been visited already (somehow).
2065 - in a second pass, traverse the chain again updating all
2066 THUNK_SEELCTORS that we find on the way with indirections to
2069 - if we encounter a "marked" THUNK_SELECTOR in a normal
2070 evacuate(), we konw it can't be updated so just evac it.
2072 Program that illustrates the problem:
2075 foo (x:xs) = let (ys, zs) = foo xs
2076 in if x >= 0 then (x:ys, zs) else (ys, x:zs)
2078 main = bar [1..(100000000::Int)]
2079 bar xs = (\(ys, zs) -> print ys >> print zs) (foo xs)
2081 -------------------------------------------------------------------------- */
2083 static inline rtsBool
2084 is_to_space ( StgClosure *p )
2088 bd = Bdescr((StgPtr)p);
2089 if (HEAP_ALLOCED(p) &&
2090 ((bd->flags & BF_EVACUATED)
2091 || ((bd->flags & BF_COMPACTED) &&
2092 is_marked((P_)p,bd)))) {
2100 eval_thunk_selector( nat field, StgSelector * p )
2103 const StgInfoTable *info_ptr;
2104 StgClosure *selectee;
2106 selectee = p->selectee;
2108 // Save the real info pointer (NOTE: not the same as get_itbl()).
2109 info_ptr = p->header.info;
2111 // If the THUNK_SELECTOR is in a generation that we are not
2112 // collecting, then bail out early. We won't be able to save any
2113 // space in any case, and updating with an indirection is trickier
2115 if (Bdescr((StgPtr)p)->gen_no > N) {
2119 // BLACKHOLE the selector thunk, since it is now under evaluation.
2120 // This is important to stop us going into an infinite loop if
2121 // this selector thunk eventually refers to itself.
2122 SET_INFO(p,&stg_BLACKHOLE_info);
2126 // We don't want to end up in to-space, because this causes
2127 // problems when the GC later tries to evacuate the result of
2128 // eval_thunk_selector(). There are various ways this could
2131 // 1. following an IND_STATIC
2133 // 2. when the old generation is compacted, the mark phase updates
2134 // from-space pointers to be to-space pointers, and we can't
2135 // reliably tell which we're following (eg. from an IND_STATIC).
2137 // 3. compacting GC again: if we're looking at a constructor in
2138 // the compacted generation, it might point directly to objects
2139 // in to-space. We must bale out here, otherwise doing the selection
2140 // will result in a to-space pointer being returned.
2142 // (1) is dealt with using a BF_EVACUATED test on the
2143 // selectee. (2) and (3): we can tell if we're looking at an
2144 // object in the compacted generation that might point to
2145 // to-space objects by testing that (a) it is BF_COMPACTED, (b)
2146 // the compacted generation is being collected, and (c) the
2147 // object is marked. Only a marked object may have pointers that
2148 // point to to-space objects, because that happens when
2151 // The to-space test is now embodied in the in_to_space() inline
2152 // function, as it is re-used below.
2154 if (is_to_space(selectee)) {
2158 info = get_itbl(selectee);
2159 switch (info->type) {
2167 case CONSTR_NOCAF_STATIC:
2168 // check that the size is in range
2169 ASSERT(field < (StgWord32)(info->layout.payload.ptrs +
2170 info->layout.payload.nptrs));
2172 // Select the right field from the constructor, and check
2173 // that the result isn't in to-space. It might be in
2174 // to-space if, for example, this constructor contains
2175 // pointers to younger-gen objects (and is on the mut-once
2180 q = selectee->payload[field];
2181 if (is_to_space(q)) {
2191 case IND_OLDGEN_PERM:
2193 selectee = ((StgInd *)selectee)->indirectee;
2197 // We don't follow pointers into to-space; the constructor
2198 // has already been evacuated, so we won't save any space
2199 // leaks by evaluating this selector thunk anyhow.
2202 case THUNK_SELECTOR:
2206 // check that we don't recurse too much, re-using the
2207 // depth bound also used in evacuate().
2208 if (thunk_selector_depth >= MAX_THUNK_SELECTOR_DEPTH) {
2211 thunk_selector_depth++;
2213 val = eval_thunk_selector(info->layout.selector_offset,
2214 (StgSelector *)selectee);
2216 thunk_selector_depth--;
2221 // We evaluated this selector thunk, so update it with
2222 // an indirection. NOTE: we don't use UPD_IND here,
2223 // because we are guaranteed that p is in a generation
2224 // that we are collecting, and we never want to put the
2225 // indirection on a mutable list.
2227 // For the purposes of LDV profiling, we have destroyed
2228 // the original selector thunk.
2229 SET_INFO(p, info_ptr);
2230 LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(selectee);
2232 ((StgInd *)selectee)->indirectee = val;
2233 SET_INFO(selectee,&stg_IND_info);
2235 // For the purposes of LDV profiling, we have created an
2237 LDV_RECORD_CREATE(selectee);
2254 case SE_CAF_BLACKHOLE:
2266 // not evaluated yet
2270 barf("eval_thunk_selector: strange selectee %d",
2275 // We didn't manage to evaluate this thunk; restore the old info pointer
2276 SET_INFO(p, info_ptr);
2280 /* -----------------------------------------------------------------------------
2281 move_TSO is called to update the TSO structure after it has been
2282 moved from one place to another.
2283 -------------------------------------------------------------------------- */
2286 move_TSO (StgTSO *src, StgTSO *dest)
2290 // relocate the stack pointer...
2291 diff = (StgPtr)dest - (StgPtr)src; // In *words*
2292 dest->sp = (StgPtr)dest->sp + diff;
2295 /* Similar to scavenge_large_bitmap(), but we don't write back the
2296 * pointers we get back from evacuate().
2299 scavenge_large_srt_bitmap( StgLargeSRT *large_srt )
2306 bitmap = large_srt->l.bitmap[b];
2307 size = (nat)large_srt->l.size;
2308 p = (StgClosure **)large_srt->srt;
2309 for (i = 0; i < size; ) {
2310 if ((bitmap & 1) != 0) {
2315 if (i % BITS_IN(W_) == 0) {
2317 bitmap = large_srt->l.bitmap[b];
2319 bitmap = bitmap >> 1;
2324 /* evacuate the SRT. If srt_bitmap is zero, then there isn't an
2325 * srt field in the info table. That's ok, because we'll
2326 * never dereference it.
2329 scavenge_srt (StgClosure **srt, nat srt_bitmap)
2334 bitmap = srt_bitmap;
2337 if (bitmap == (StgHalfWord)(-1)) {
2338 scavenge_large_srt_bitmap( (StgLargeSRT *)srt );
2342 while (bitmap != 0) {
2343 if ((bitmap & 1) != 0) {
2344 #ifdef ENABLE_WIN32_DLL_SUPPORT
2345 // Special-case to handle references to closures hiding out in DLLs, since
2346 // double indirections required to get at those. The code generator knows
2347 // which is which when generating the SRT, so it stores the (indirect)
2348 // reference to the DLL closure in the table by first adding one to it.
2349 // We check for this here, and undo the addition before evacuating it.
2351 // If the SRT entry hasn't got bit 0 set, the SRT entry points to a
2352 // closure that's fixed at link-time, and no extra magic is required.
2353 if ( (unsigned long)(*srt) & 0x1 ) {
2354 evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
2363 bitmap = bitmap >> 1;
2369 scavenge_thunk_srt(const StgInfoTable *info)
2371 StgThunkInfoTable *thunk_info;
2373 thunk_info = itbl_to_thunk_itbl(info);
2374 scavenge_srt((StgClosure **)GET_SRT(thunk_info), thunk_info->i.srt_bitmap);
2378 scavenge_fun_srt(const StgInfoTable *info)
2380 StgFunInfoTable *fun_info;
2382 fun_info = itbl_to_fun_itbl(info);
2383 scavenge_srt((StgClosure **)GET_FUN_SRT(fun_info), fun_info->i.srt_bitmap);
2386 /* -----------------------------------------------------------------------------
2388 -------------------------------------------------------------------------- */
2391 scavengeTSO (StgTSO *tso)
2393 if ( tso->why_blocked == BlockedOnMVar
2394 || tso->why_blocked == BlockedOnBlackHole
2395 || tso->why_blocked == BlockedOnException
2397 || tso->why_blocked == BlockedOnGA
2398 || tso->why_blocked == BlockedOnGA_NoSend
2401 tso->block_info.closure = evacuate(tso->block_info.closure);
2403 if ( tso->blocked_exceptions != NULL ) {
2404 tso->blocked_exceptions =
2405 (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
2408 // We don't always chase the link field: TSOs on the blackhole
2409 // queue are not automatically alive, so the link field is a
2410 // "weak" pointer in that case.
2411 if (tso->why_blocked != BlockedOnBlackHole) {
2412 tso->link = (StgTSO *)evacuate((StgClosure *)tso->link);
2415 // scavange current transaction record
2416 tso->trec = (StgTRecHeader *)evacuate((StgClosure *)tso->trec);
2418 // scavenge this thread's stack
2419 scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
2422 /* -----------------------------------------------------------------------------
2423 Blocks of function args occur on the stack (at the top) and
2425 -------------------------------------------------------------------------- */
2427 STATIC_INLINE StgPtr
2428 scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
2435 switch (fun_info->f.fun_type) {
2437 bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
2438 size = BITMAP_SIZE(fun_info->f.b.bitmap);
2441 size = GET_FUN_LARGE_BITMAP(fun_info)->size;
2442 scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
2446 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2447 size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->f.fun_type]);
2450 if ((bitmap & 1) == 0) {
2451 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2454 bitmap = bitmap >> 1;
2462 STATIC_INLINE StgPtr
2463 scavenge_PAP_payload (StgClosure *fun, StgClosure **payload, StgWord size)
2467 StgFunInfoTable *fun_info;
2469 fun_info = get_fun_itbl(fun);
2470 ASSERT(fun_info->i.type != PAP);
2471 p = (StgPtr)payload;
2473 switch (fun_info->f.fun_type) {
2475 bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
2478 scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
2482 scavenge_large_bitmap((StgPtr)payload, BCO_BITMAP(fun), size);
2486 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2489 if ((bitmap & 1) == 0) {
2490 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2493 bitmap = bitmap >> 1;
2501 STATIC_INLINE StgPtr
2502 scavenge_PAP (StgPAP *pap)
2504 pap->fun = evacuate(pap->fun);
2505 return scavenge_PAP_payload (pap->fun, pap->payload, pap->n_args);
2508 STATIC_INLINE StgPtr
2509 scavenge_AP (StgAP *ap)
2511 ap->fun = evacuate(ap->fun);
2512 return scavenge_PAP_payload (ap->fun, ap->payload, ap->n_args);
2515 /* -----------------------------------------------------------------------------
2516 Scavenge a given step until there are no more objects in this step
2519 evac_gen is set by the caller to be either zero (for a step in a
2520 generation < N) or G where G is the generation of the step being
2523 We sometimes temporarily change evac_gen back to zero if we're
2524 scavenging a mutable object where early promotion isn't such a good
2526 -------------------------------------------------------------------------- */
2534 nat saved_evac_gen = evac_gen;
2539 failed_to_evac = rtsFalse;
2541 /* scavenge phase - standard breadth-first scavenging of the
2545 while (bd != stp->hp_bd || p < stp->hp) {
2547 // If we're at the end of this block, move on to the next block
2548 if (bd != stp->hp_bd && p == bd->free) {
2554 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2555 info = get_itbl((StgClosure *)p);
2557 ASSERT(thunk_selector_depth == 0);
2560 switch (info->type) {
2564 StgMVar *mvar = ((StgMVar *)p);
2566 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
2567 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
2568 mvar->value = evacuate((StgClosure *)mvar->value);
2569 evac_gen = saved_evac_gen;
2570 failed_to_evac = rtsTrue; // mutable.
2571 p += sizeofW(StgMVar);
2576 scavenge_fun_srt(info);
2577 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2578 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2579 p += sizeofW(StgHeader) + 2;
2583 scavenge_thunk_srt(info);
2584 ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
2585 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2586 p += sizeofW(StgThunk) + 2;
2590 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2591 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2592 p += sizeofW(StgHeader) + 2;
2596 scavenge_thunk_srt(info);
2597 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2598 p += sizeofW(StgThunk) + 1;
2602 scavenge_fun_srt(info);
2604 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2605 p += sizeofW(StgHeader) + 1;
2609 scavenge_thunk_srt(info);
2610 p += sizeofW(StgThunk) + 1;
2614 scavenge_fun_srt(info);
2616 p += sizeofW(StgHeader) + 1;
2620 scavenge_thunk_srt(info);
2621 p += sizeofW(StgThunk) + 2;
2625 scavenge_fun_srt(info);
2627 p += sizeofW(StgHeader) + 2;
2631 scavenge_thunk_srt(info);
2632 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2633 p += sizeofW(StgThunk) + 2;
2637 scavenge_fun_srt(info);
2639 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2640 p += sizeofW(StgHeader) + 2;
2644 scavenge_fun_srt(info);
2651 scavenge_thunk_srt(info);
2652 end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
2653 for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
2654 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2656 p += info->layout.payload.nptrs;
2668 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2669 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2670 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2672 p += info->layout.payload.nptrs;
2677 StgBCO *bco = (StgBCO *)p;
2678 bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
2679 bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
2680 bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
2681 bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
2682 p += bco_sizeW(bco);
2687 if (stp->gen->no != 0) {
2690 // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an
2691 // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
2692 LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
2695 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
2697 SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
2699 // We pretend that p has just been created.
2700 LDV_RECORD_CREATE((StgClosure *)p);
2703 case IND_OLDGEN_PERM:
2704 ((StgInd *)p)->indirectee = evacuate(((StgInd *)p)->indirectee);
2705 p += sizeofW(StgInd);
2710 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2711 evac_gen = saved_evac_gen;
2712 failed_to_evac = rtsTrue; // mutable anyhow
2713 p += sizeofW(StgMutVar);
2717 case SE_CAF_BLACKHOLE:
2720 p += BLACKHOLE_sizeW();
2723 case THUNK_SELECTOR:
2725 StgSelector *s = (StgSelector *)p;
2726 s->selectee = evacuate(s->selectee);
2727 p += THUNK_SELECTOR_sizeW();
2731 // A chunk of stack saved in a heap object
2734 StgAP_STACK *ap = (StgAP_STACK *)p;
2736 ap->fun = evacuate(ap->fun);
2737 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2738 p = (StgPtr)ap->payload + ap->size;
2743 p = scavenge_PAP((StgPAP *)p);
2747 p = scavenge_AP((StgAP *)p);
2751 // nothing to follow
2752 p += arr_words_sizeW((StgArrWords *)p);
2756 // follow everything
2760 evac_gen = 0; // repeatedly mutable
2761 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2762 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2763 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2765 evac_gen = saved_evac_gen;
2766 failed_to_evac = rtsTrue; // mutable anyhow.
2770 case MUT_ARR_PTRS_FROZEN:
2771 case MUT_ARR_PTRS_FROZEN0:
2772 // follow everything
2776 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2777 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2778 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2780 // it's tempting to recordMutable() if failed_to_evac is
2781 // false, but that breaks some assumptions (eg. every
2782 // closure on the mutable list is supposed to have the MUT
2783 // flag set, and MUT_ARR_PTRS_FROZEN doesn't).
2789 StgTSO *tso = (StgTSO *)p;
2792 evac_gen = saved_evac_gen;
2793 failed_to_evac = rtsTrue; // mutable anyhow.
2794 p += tso_sizeW(tso);
2802 nat size, ptrs, nonptrs, vhs;
2804 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2806 StgRBH *rbh = (StgRBH *)p;
2807 (StgClosure *)rbh->blocking_queue =
2808 evacuate((StgClosure *)rbh->blocking_queue);
2809 failed_to_evac = rtsTrue; // mutable anyhow.
2811 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2812 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2813 // ToDo: use size of reverted closure here!
2814 p += BLACKHOLE_sizeW();
2820 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2821 // follow the pointer to the node which is being demanded
2822 (StgClosure *)bf->node =
2823 evacuate((StgClosure *)bf->node);
2824 // follow the link to the rest of the blocking queue
2825 (StgClosure *)bf->link =
2826 evacuate((StgClosure *)bf->link);
2828 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
2829 bf, info_type((StgClosure *)bf),
2830 bf->node, info_type(bf->node)));
2831 p += sizeofW(StgBlockedFetch);
2839 p += sizeofW(StgFetchMe);
2840 break; // nothing to do in this case
2844 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
2845 (StgClosure *)fmbq->blocking_queue =
2846 evacuate((StgClosure *)fmbq->blocking_queue);
2848 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
2849 p, info_type((StgClosure *)p)));
2850 p += sizeofW(StgFetchMeBlockingQueue);
2855 case TVAR_WAIT_QUEUE:
2857 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
2859 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
2860 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
2861 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
2862 evac_gen = saved_evac_gen;
2863 failed_to_evac = rtsTrue; // mutable
2864 p += sizeofW(StgTVarWaitQueue);
2870 StgTVar *tvar = ((StgTVar *) p);
2872 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
2873 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
2874 evac_gen = saved_evac_gen;
2875 failed_to_evac = rtsTrue; // mutable
2876 p += sizeofW(StgTVar);
2882 StgTRecHeader *trec = ((StgTRecHeader *) p);
2884 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
2885 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
2886 evac_gen = saved_evac_gen;
2887 failed_to_evac = rtsTrue; // mutable
2888 p += sizeofW(StgTRecHeader);
2895 StgTRecChunk *tc = ((StgTRecChunk *) p);
2896 TRecEntry *e = &(tc -> entries[0]);
2898 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
2899 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
2900 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
2901 e->expected_value = evacuate((StgClosure*)e->expected_value);
2902 e->new_value = evacuate((StgClosure*)e->new_value);
2904 evac_gen = saved_evac_gen;
2905 failed_to_evac = rtsTrue; // mutable
2906 p += sizeofW(StgTRecChunk);
2911 barf("scavenge: unimplemented/strange closure type %d @ %p",
2916 * We need to record the current object on the mutable list if
2917 * (a) It is actually mutable, or
2918 * (b) It contains pointers to a younger generation.
2919 * Case (b) arises if we didn't manage to promote everything that
2920 * the current object points to into the current generation.
2922 if (failed_to_evac) {
2923 failed_to_evac = rtsFalse;
2924 recordMutableGen((StgClosure *)q, stp->gen);
2932 /* -----------------------------------------------------------------------------
2933 Scavenge everything on the mark stack.
2935 This is slightly different from scavenge():
2936 - we don't walk linearly through the objects, so the scavenger
2937 doesn't need to advance the pointer on to the next object.
2938 -------------------------------------------------------------------------- */
2941 scavenge_mark_stack(void)
2947 evac_gen = oldest_gen->no;
2948 saved_evac_gen = evac_gen;
2951 while (!mark_stack_empty()) {
2952 p = pop_mark_stack();
2954 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2955 info = get_itbl((StgClosure *)p);
2958 switch (info->type) {
2962 StgMVar *mvar = ((StgMVar *)p);
2964 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
2965 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
2966 mvar->value = evacuate((StgClosure *)mvar->value);
2967 evac_gen = saved_evac_gen;
2968 failed_to_evac = rtsTrue; // mutable.
2973 scavenge_fun_srt(info);
2974 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2975 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2979 scavenge_thunk_srt(info);
2980 ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
2981 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2985 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2986 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2991 scavenge_fun_srt(info);
2992 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2997 scavenge_thunk_srt(info);
2998 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
3003 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3008 scavenge_fun_srt(info);
3013 scavenge_thunk_srt(info);
3021 scavenge_fun_srt(info);
3028 scavenge_thunk_srt(info);
3029 end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
3030 for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
3031 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3044 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3045 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
3046 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3052 StgBCO *bco = (StgBCO *)p;
3053 bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
3054 bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
3055 bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
3056 bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
3061 // don't need to do anything here: the only possible case
3062 // is that we're in a 1-space compacting collector, with
3063 // no "old" generation.
3067 case IND_OLDGEN_PERM:
3068 ((StgInd *)p)->indirectee =
3069 evacuate(((StgInd *)p)->indirectee);
3074 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3075 evac_gen = saved_evac_gen;
3076 failed_to_evac = rtsTrue;
3080 case SE_CAF_BLACKHOLE:
3086 case THUNK_SELECTOR:
3088 StgSelector *s = (StgSelector *)p;
3089 s->selectee = evacuate(s->selectee);
3093 // A chunk of stack saved in a heap object
3096 StgAP_STACK *ap = (StgAP_STACK *)p;
3098 ap->fun = evacuate(ap->fun);
3099 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3104 scavenge_PAP((StgPAP *)p);
3108 scavenge_AP((StgAP *)p);
3112 // follow everything
3116 evac_gen = 0; // repeatedly mutable
3117 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3118 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3119 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3121 evac_gen = saved_evac_gen;
3122 failed_to_evac = rtsTrue; // mutable anyhow.
3126 case MUT_ARR_PTRS_FROZEN:
3127 case MUT_ARR_PTRS_FROZEN0:
3128 // follow everything
3132 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3133 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3134 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3141 StgTSO *tso = (StgTSO *)p;
3144 evac_gen = saved_evac_gen;
3145 failed_to_evac = rtsTrue;
3153 nat size, ptrs, nonptrs, vhs;
3155 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3157 StgRBH *rbh = (StgRBH *)p;
3158 bh->blocking_queue =
3159 (StgTSO *)evacuate((StgClosure *)bh->blocking_queue);
3160 failed_to_evac = rtsTrue; // mutable anyhow.
3162 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3163 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3169 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3170 // follow the pointer to the node which is being demanded
3171 (StgClosure *)bf->node =
3172 evacuate((StgClosure *)bf->node);
3173 // follow the link to the rest of the blocking queue
3174 (StgClosure *)bf->link =
3175 evacuate((StgClosure *)bf->link);
3177 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3178 bf, info_type((StgClosure *)bf),
3179 bf->node, info_type(bf->node)));
3187 break; // nothing to do in this case
3191 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3192 (StgClosure *)fmbq->blocking_queue =
3193 evacuate((StgClosure *)fmbq->blocking_queue);
3195 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3196 p, info_type((StgClosure *)p)));
3201 case TVAR_WAIT_QUEUE:
3203 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3205 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3206 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3207 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3208 evac_gen = saved_evac_gen;
3209 failed_to_evac = rtsTrue; // mutable
3215 StgTVar *tvar = ((StgTVar *) p);
3217 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3218 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3219 evac_gen = saved_evac_gen;
3220 failed_to_evac = rtsTrue; // mutable
3227 StgTRecChunk *tc = ((StgTRecChunk *) p);
3228 TRecEntry *e = &(tc -> entries[0]);
3230 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3231 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3232 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3233 e->expected_value = evacuate((StgClosure*)e->expected_value);
3234 e->new_value = evacuate((StgClosure*)e->new_value);
3236 evac_gen = saved_evac_gen;
3237 failed_to_evac = rtsTrue; // mutable
3243 StgTRecHeader *trec = ((StgTRecHeader *) p);
3245 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3246 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3247 evac_gen = saved_evac_gen;
3248 failed_to_evac = rtsTrue; // mutable
3253 barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p",
3257 if (failed_to_evac) {
3258 failed_to_evac = rtsFalse;
3259 recordMutableGen((StgClosure *)q, &generations[evac_gen]);
3262 // mark the next bit to indicate "scavenged"
3263 mark(q+1, Bdescr(q));
3265 } // while (!mark_stack_empty())
3267 // start a new linear scan if the mark stack overflowed at some point
3268 if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
3269 IF_DEBUG(gc, debugBelch("scavenge_mark_stack: starting linear scan"));
3270 mark_stack_overflowed = rtsFalse;
3271 oldgen_scan_bd = oldest_gen->steps[0].blocks;
3272 oldgen_scan = oldgen_scan_bd->start;
3275 if (oldgen_scan_bd) {
3276 // push a new thing on the mark stack
3278 // find a closure that is marked but not scavenged, and start
3280 while (oldgen_scan < oldgen_scan_bd->free
3281 && !is_marked(oldgen_scan,oldgen_scan_bd)) {
3285 if (oldgen_scan < oldgen_scan_bd->free) {
3287 // already scavenged?
3288 if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
3289 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3292 push_mark_stack(oldgen_scan);
3293 // ToDo: bump the linear scan by the actual size of the object
3294 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3298 oldgen_scan_bd = oldgen_scan_bd->link;
3299 if (oldgen_scan_bd != NULL) {
3300 oldgen_scan = oldgen_scan_bd->start;
3306 /* -----------------------------------------------------------------------------
3307 Scavenge one object.
3309 This is used for objects that are temporarily marked as mutable
3310 because they contain old-to-new generation pointers. Only certain
3311 objects can have this property.
3312 -------------------------------------------------------------------------- */
3315 scavenge_one(StgPtr p)
3317 const StgInfoTable *info;
3318 nat saved_evac_gen = evac_gen;
3321 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3322 info = get_itbl((StgClosure *)p);
3324 switch (info->type) {
3328 StgMVar *mvar = ((StgMVar *)p);
3330 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
3331 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
3332 mvar->value = evacuate((StgClosure *)mvar->value);
3333 evac_gen = saved_evac_gen;
3334 failed_to_evac = rtsTrue; // mutable.
3347 end = (StgPtr)((StgThunk *)p)->payload + info->layout.payload.ptrs;
3348 for (q = (StgPtr)((StgThunk *)p)->payload; q < end; q++) {
3349 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3355 case FUN_1_0: // hardly worth specialising these guys
3372 end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3373 for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
3374 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3381 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3382 evac_gen = saved_evac_gen;
3383 failed_to_evac = rtsTrue; // mutable anyhow
3387 case SE_CAF_BLACKHOLE:
3392 case THUNK_SELECTOR:
3394 StgSelector *s = (StgSelector *)p;
3395 s->selectee = evacuate(s->selectee);
3401 StgAP_STACK *ap = (StgAP_STACK *)p;
3403 ap->fun = evacuate(ap->fun);
3404 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3405 p = (StgPtr)ap->payload + ap->size;
3410 p = scavenge_PAP((StgPAP *)p);
3414 p = scavenge_AP((StgAP *)p);
3418 // nothing to follow
3423 // follow everything
3426 evac_gen = 0; // repeatedly mutable
3427 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3428 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3429 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3431 evac_gen = saved_evac_gen;
3432 failed_to_evac = rtsTrue;
3436 case MUT_ARR_PTRS_FROZEN:
3437 case MUT_ARR_PTRS_FROZEN0:
3439 // follow everything
3442 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3443 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3444 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3451 StgTSO *tso = (StgTSO *)p;
3453 evac_gen = 0; // repeatedly mutable
3455 evac_gen = saved_evac_gen;
3456 failed_to_evac = rtsTrue;
3464 nat size, ptrs, nonptrs, vhs;
3466 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3468 StgRBH *rbh = (StgRBH *)p;
3469 (StgClosure *)rbh->blocking_queue =
3470 evacuate((StgClosure *)rbh->blocking_queue);
3471 failed_to_evac = rtsTrue; // mutable anyhow.
3473 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3474 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3475 // ToDo: use size of reverted closure here!
3481 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3482 // follow the pointer to the node which is being demanded
3483 (StgClosure *)bf->node =
3484 evacuate((StgClosure *)bf->node);
3485 // follow the link to the rest of the blocking queue
3486 (StgClosure *)bf->link =
3487 evacuate((StgClosure *)bf->link);
3489 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3490 bf, info_type((StgClosure *)bf),
3491 bf->node, info_type(bf->node)));
3499 break; // nothing to do in this case
3503 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3504 (StgClosure *)fmbq->blocking_queue =
3505 evacuate((StgClosure *)fmbq->blocking_queue);
3507 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3508 p, info_type((StgClosure *)p)));
3513 case TVAR_WAIT_QUEUE:
3515 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3517 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3518 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3519 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3520 evac_gen = saved_evac_gen;
3521 failed_to_evac = rtsTrue; // mutable
3527 StgTVar *tvar = ((StgTVar *) p);
3529 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3530 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3531 evac_gen = saved_evac_gen;
3532 failed_to_evac = rtsTrue; // mutable
3538 StgTRecHeader *trec = ((StgTRecHeader *) p);
3540 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3541 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3542 evac_gen = saved_evac_gen;
3543 failed_to_evac = rtsTrue; // mutable
3550 StgTRecChunk *tc = ((StgTRecChunk *) p);
3551 TRecEntry *e = &(tc -> entries[0]);
3553 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3554 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3555 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3556 e->expected_value = evacuate((StgClosure*)e->expected_value);
3557 e->new_value = evacuate((StgClosure*)e->new_value);
3559 evac_gen = saved_evac_gen;
3560 failed_to_evac = rtsTrue; // mutable
3565 case IND_OLDGEN_PERM:
3568 /* Careful here: a THUNK can be on the mutable list because
3569 * it contains pointers to young gen objects. If such a thunk
3570 * is updated, the IND_OLDGEN will be added to the mutable
3571 * list again, and we'll scavenge it twice. evacuate()
3572 * doesn't check whether the object has already been
3573 * evacuated, so we perform that check here.
3575 StgClosure *q = ((StgInd *)p)->indirectee;
3576 if (HEAP_ALLOCED(q) && Bdescr((StgPtr)q)->flags & BF_EVACUATED) {
3579 ((StgInd *)p)->indirectee = evacuate(q);
3582 #if 0 && defined(DEBUG)
3583 if (RtsFlags.DebugFlags.gc)
3584 /* Debugging code to print out the size of the thing we just
3588 StgPtr start = gen->steps[0].scan;
3589 bdescr *start_bd = gen->steps[0].scan_bd;
3591 scavenge(&gen->steps[0]);
3592 if (start_bd != gen->steps[0].scan_bd) {
3593 size += (P_)BLOCK_ROUND_UP(start) - start;
3594 start_bd = start_bd->link;
3595 while (start_bd != gen->steps[0].scan_bd) {
3596 size += BLOCK_SIZE_W;
3597 start_bd = start_bd->link;
3599 size += gen->steps[0].scan -
3600 (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
3602 size = gen->steps[0].scan - start;
3604 debugBelch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
3610 barf("scavenge_one: strange object %d", (int)(info->type));
3613 no_luck = failed_to_evac;
3614 failed_to_evac = rtsFalse;
3618 /* -----------------------------------------------------------------------------
3619 Scavenging mutable lists.
3621 We treat the mutable list of each generation > N (i.e. all the
3622 generations older than the one being collected) as roots. We also
3623 remove non-mutable objects from the mutable list at this point.
3624 -------------------------------------------------------------------------- */
3627 scavenge_mutable_list(generation *gen)
3632 bd = gen->saved_mut_list;
3635 for (; bd != NULL; bd = bd->link) {
3636 for (q = bd->start; q < bd->free; q++) {
3638 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3639 if (scavenge_one(p)) {
3640 /* didn't manage to promote everything, so put the
3641 * object back on the list.
3643 recordMutableGen((StgClosure *)p,gen);
3648 // free the old mut_list
3649 freeChain(gen->saved_mut_list);
3650 gen->saved_mut_list = NULL;
3655 scavenge_static(void)
3657 StgClosure* p = static_objects;
3658 const StgInfoTable *info;
3660 /* Always evacuate straight to the oldest generation for static
3662 evac_gen = oldest_gen->no;
3664 /* keep going until we've scavenged all the objects on the linked
3666 while (p != END_OF_STATIC_LIST) {
3668 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3671 if (info->type==RBH)
3672 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3674 // make sure the info pointer is into text space
3676 /* Take this object *off* the static_objects list,
3677 * and put it on the scavenged_static_objects list.
3679 static_objects = *STATIC_LINK(info,p);
3680 *STATIC_LINK(info,p) = scavenged_static_objects;
3681 scavenged_static_objects = p;
3683 switch (info -> type) {
3687 StgInd *ind = (StgInd *)p;
3688 ind->indirectee = evacuate(ind->indirectee);
3690 /* might fail to evacuate it, in which case we have to pop it
3691 * back on the mutable list of the oldest generation. We
3692 * leave it *on* the scavenged_static_objects list, though,
3693 * in case we visit this object again.
3695 if (failed_to_evac) {
3696 failed_to_evac = rtsFalse;
3697 recordMutableGen((StgClosure *)p,oldest_gen);
3703 scavenge_thunk_srt(info);
3707 scavenge_fun_srt(info);
3714 next = (P_)p->payload + info->layout.payload.ptrs;
3715 // evacuate the pointers
3716 for (q = (P_)p->payload; q < next; q++) {
3717 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3723 barf("scavenge_static: strange closure %d", (int)(info->type));
3726 ASSERT(failed_to_evac == rtsFalse);
3728 /* get the next static object from the list. Remember, there might
3729 * be more stuff on this list now that we've done some evacuating!
3730 * (static_objects is a global)
3736 /* -----------------------------------------------------------------------------
3737 scavenge a chunk of memory described by a bitmap
3738 -------------------------------------------------------------------------- */
3741 scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
3747 bitmap = large_bitmap->bitmap[b];
3748 for (i = 0; i < size; ) {
3749 if ((bitmap & 1) == 0) {
3750 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3754 if (i % BITS_IN(W_) == 0) {
3756 bitmap = large_bitmap->bitmap[b];
3758 bitmap = bitmap >> 1;
3763 STATIC_INLINE StgPtr
3764 scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap)
3767 if ((bitmap & 1) == 0) {
3768 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3771 bitmap = bitmap >> 1;
3777 /* -----------------------------------------------------------------------------
3778 scavenge_stack walks over a section of stack and evacuates all the
3779 objects pointed to by it. We can use the same code for walking
3780 AP_STACK_UPDs, since these are just sections of copied stack.
3781 -------------------------------------------------------------------------- */
3785 scavenge_stack(StgPtr p, StgPtr stack_end)
3787 const StgRetInfoTable* info;
3791 //IF_DEBUG(sanity, debugBelch(" scavenging stack between %p and %p", p, stack_end));
3794 * Each time around this loop, we are looking at a chunk of stack
3795 * that starts with an activation record.
3798 while (p < stack_end) {
3799 info = get_ret_itbl((StgClosure *)p);
3801 switch (info->i.type) {
3804 ((StgUpdateFrame *)p)->updatee
3805 = evacuate(((StgUpdateFrame *)p)->updatee);
3806 p += sizeofW(StgUpdateFrame);
3809 // small bitmap (< 32 entries, or 64 on a 64-bit machine)
3810 case CATCH_STM_FRAME:
3811 case CATCH_RETRY_FRAME:
3812 case ATOMICALLY_FRAME:
3817 bitmap = BITMAP_BITS(info->i.layout.bitmap);
3818 size = BITMAP_SIZE(info->i.layout.bitmap);
3819 // NOTE: the payload starts immediately after the info-ptr, we
3820 // don't have an StgHeader in the same sense as a heap closure.
3822 p = scavenge_small_bitmap(p, size, bitmap);
3825 scavenge_srt((StgClosure **)GET_SRT(info), info->i.srt_bitmap);
3833 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3836 size = BCO_BITMAP_SIZE(bco);
3837 scavenge_large_bitmap(p, BCO_BITMAP(bco), size);
3842 // large bitmap (> 32 entries, or > 64 on a 64-bit machine)
3848 size = GET_LARGE_BITMAP(&info->i)->size;
3850 scavenge_large_bitmap(p, GET_LARGE_BITMAP(&info->i), size);
3852 // and don't forget to follow the SRT
3856 // Dynamic bitmap: the mask is stored on the stack, and
3857 // there are a number of non-pointers followed by a number
3858 // of pointers above the bitmapped area. (see StgMacros.h,
3863 dyn = ((StgRetDyn *)p)->liveness;
3865 // traverse the bitmap first
3866 bitmap = RET_DYN_LIVENESS(dyn);
3867 p = (P_)&((StgRetDyn *)p)->payload[0];
3868 size = RET_DYN_BITMAP_SIZE;
3869 p = scavenge_small_bitmap(p, size, bitmap);
3871 // skip over the non-ptr words
3872 p += RET_DYN_NONPTRS(dyn) + RET_DYN_NONPTR_REGS_SIZE;
3874 // follow the ptr words
3875 for (size = RET_DYN_PTRS(dyn); size > 0; size--) {
3876 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3884 StgRetFun *ret_fun = (StgRetFun *)p;
3885 StgFunInfoTable *fun_info;
3887 ret_fun->fun = evacuate(ret_fun->fun);
3888 fun_info = get_fun_itbl(ret_fun->fun);
3889 p = scavenge_arg_block(fun_info, ret_fun->payload);
3894 barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->i.type));
3899 /*-----------------------------------------------------------------------------
3900 scavenge the large object list.
3902 evac_gen set by caller; similar games played with evac_gen as with
3903 scavenge() - see comment at the top of scavenge(). Most large
3904 objects are (repeatedly) mutable, so most of the time evac_gen will
3906 --------------------------------------------------------------------------- */
3909 scavenge_large(step *stp)
3914 bd = stp->new_large_objects;
3916 for (; bd != NULL; bd = stp->new_large_objects) {
3918 /* take this object *off* the large objects list and put it on
3919 * the scavenged large objects list. This is so that we can
3920 * treat new_large_objects as a stack and push new objects on
3921 * the front when evacuating.
3923 stp->new_large_objects = bd->link;
3924 dbl_link_onto(bd, &stp->scavenged_large_objects);
3926 // update the block count in this step.
3927 stp->n_scavenged_large_blocks += bd->blocks;
3930 if (scavenge_one(p)) {
3931 recordMutableGen((StgClosure *)p, stp->gen);
3936 /* -----------------------------------------------------------------------------
3937 Initialising the static object & mutable lists
3938 -------------------------------------------------------------------------- */
3941 zero_static_object_list(StgClosure* first_static)
3945 const StgInfoTable *info;
3947 for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
3949 link = *STATIC_LINK(info, p);
3950 *STATIC_LINK(info,p) = NULL;
3954 /* -----------------------------------------------------------------------------
3956 -------------------------------------------------------------------------- */
3963 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
3964 c = (StgIndStatic *)c->static_link)
3966 SET_INFO(c, c->saved_info);
3967 c->saved_info = NULL;
3968 // could, but not necessary: c->static_link = NULL;
3970 revertible_caf_list = NULL;
3974 markCAFs( evac_fn evac )
3978 for (c = (StgIndStatic *)caf_list; c != NULL;
3979 c = (StgIndStatic *)c->static_link)
3981 evac(&c->indirectee);
3983 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
3984 c = (StgIndStatic *)c->static_link)
3986 evac(&c->indirectee);
3990 /* -----------------------------------------------------------------------------
3991 Sanity code for CAF garbage collection.
3993 With DEBUG turned on, we manage a CAF list in addition to the SRT
3994 mechanism. After GC, we run down the CAF list and blackhole any
3995 CAFs which have been garbage collected. This means we get an error
3996 whenever the program tries to enter a garbage collected CAF.
3998 Any garbage collected CAFs are taken off the CAF list at the same
4000 -------------------------------------------------------------------------- */
4002 #if 0 && defined(DEBUG)
4009 const StgInfoTable *info;
4020 ASSERT(info->type == IND_STATIC);
4022 if (STATIC_LINK(info,p) == NULL) {
4023 IF_DEBUG(gccafs, debugBelch("CAF gc'd at 0x%04lx", (long)p));
4025 SET_INFO(p,&stg_BLACKHOLE_info);
4026 p = STATIC_LINK2(info,p);
4030 pp = &STATIC_LINK2(info,p);
4037 // debugBelch("%d CAFs live", i);
4042 /* -----------------------------------------------------------------------------
4045 Whenever a thread returns to the scheduler after possibly doing
4046 some work, we have to run down the stack and black-hole all the
4047 closures referred to by update frames.
4048 -------------------------------------------------------------------------- */
4051 threadLazyBlackHole(StgTSO *tso)
4054 StgRetInfoTable *info;
4058 stack_end = &tso->stack[tso->stack_size];
4060 frame = (StgClosure *)tso->sp;
4063 info = get_ret_itbl(frame);
4065 switch (info->i.type) {
4068 bh = ((StgUpdateFrame *)frame)->updatee;
4070 /* if the thunk is already blackholed, it means we've also
4071 * already blackholed the rest of the thunks on this stack,
4072 * so we can stop early.
4074 * The blackhole made for a CAF is a CAF_BLACKHOLE, so they
4075 * don't interfere with this optimisation.
4077 if (bh->header.info == &stg_BLACKHOLE_info) {
4081 if (bh->header.info != &stg_CAF_BLACKHOLE_info) {
4082 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4083 debugBelch("Unexpected lazy BHing required at 0x%04x\n",(int)bh);
4087 // We pretend that bh is now dead.
4088 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4090 SET_INFO(bh,&stg_BLACKHOLE_info);
4092 // We pretend that bh has just been created.
4093 LDV_RECORD_CREATE(bh);
4096 frame = (StgClosure *) ((StgUpdateFrame *)frame + 1);
4102 // normal stack frames; do nothing except advance the pointer
4104 frame = (StgClosure *)((StgPtr)frame + stack_frame_sizeW(frame));
4110 /* -----------------------------------------------------------------------------
4113 * Code largely pinched from old RTS, then hacked to bits. We also do
4114 * lazy black holing here.
4116 * -------------------------------------------------------------------------- */
4118 struct stack_gap { StgWord gap_size; struct stack_gap *next_gap; };
4121 threadSqueezeStack(StgTSO *tso)
4124 rtsBool prev_was_update_frame;
4125 StgClosure *updatee = NULL;
4127 StgRetInfoTable *info;
4128 StgWord current_gap_size;
4129 struct stack_gap *gap;
4132 // Traverse the stack upwards, replacing adjacent update frames
4133 // with a single update frame and a "stack gap". A stack gap
4134 // contains two values: the size of the gap, and the distance
4135 // to the next gap (or the stack top).
4137 bottom = &(tso->stack[tso->stack_size]);
4141 ASSERT(frame < bottom);
4143 prev_was_update_frame = rtsFalse;
4144 current_gap_size = 0;
4145 gap = (struct stack_gap *) (tso->sp - sizeofW(StgUpdateFrame));
4147 while (frame < bottom) {
4149 info = get_ret_itbl((StgClosure *)frame);
4150 switch (info->i.type) {
4154 StgUpdateFrame *upd = (StgUpdateFrame *)frame;
4156 if (upd->updatee->header.info == &stg_BLACKHOLE_info) {
4158 // found a BLACKHOLE'd update frame; we've been here
4159 // before, in a previous GC, so just break out.
4161 // Mark the end of the gap, if we're in one.
4162 if (current_gap_size != 0) {
4163 gap = (struct stack_gap *)(frame-sizeofW(StgUpdateFrame));
4166 frame += sizeofW(StgUpdateFrame);
4167 goto done_traversing;
4170 if (prev_was_update_frame) {
4172 TICK_UPD_SQUEEZED();
4173 /* wasn't there something about update squeezing and ticky to be
4174 * sorted out? oh yes: we aren't counting each enter properly
4175 * in this case. See the log somewhere. KSW 1999-04-21
4177 * Check two things: that the two update frames don't point to
4178 * the same object, and that the updatee_bypass isn't already an
4179 * indirection. Both of these cases only happen when we're in a
4180 * block hole-style loop (and there are multiple update frames
4181 * on the stack pointing to the same closure), but they can both
4182 * screw us up if we don't check.
4184 if (upd->updatee != updatee && !closure_IND(upd->updatee)) {
4185 UPD_IND_NOLOCK(upd->updatee, updatee);
4188 // now mark this update frame as a stack gap. The gap
4189 // marker resides in the bottom-most update frame of
4190 // the series of adjacent frames, and covers all the
4191 // frames in this series.
4192 current_gap_size += sizeofW(StgUpdateFrame);
4193 ((struct stack_gap *)frame)->gap_size = current_gap_size;
4194 ((struct stack_gap *)frame)->next_gap = gap;
4196 frame += sizeofW(StgUpdateFrame);
4200 // single update frame, or the topmost update frame in a series
4202 StgClosure *bh = upd->updatee;
4204 // Do lazy black-holing
4205 if (bh->header.info != &stg_BLACKHOLE_info &&
4206 bh->header.info != &stg_CAF_BLACKHOLE_info) {
4207 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4208 debugBelch("Unexpected lazy BHing required at 0x%04x",(int)bh);
4211 // zero out the slop so that the sanity checker can tell
4212 // where the next closure is.
4213 DEBUG_FILL_SLOP(bh);
4216 // We pretend that bh is now dead.
4217 // ToDo: is the slop filling the same as DEBUG_FILL_SLOP?
4218 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4220 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
4221 SET_INFO(bh,&stg_BLACKHOLE_info);
4223 // We pretend that bh has just been created.
4224 LDV_RECORD_CREATE(bh);
4227 prev_was_update_frame = rtsTrue;
4228 updatee = upd->updatee;
4229 frame += sizeofW(StgUpdateFrame);
4235 prev_was_update_frame = rtsFalse;
4237 // we're not in a gap... check whether this is the end of a gap
4238 // (an update frame can't be the end of a gap).
4239 if (current_gap_size != 0) {
4240 gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
4242 current_gap_size = 0;
4244 frame += stack_frame_sizeW((StgClosure *)frame);
4251 // Now we have a stack with gaps in it, and we have to walk down
4252 // shoving the stack up to fill in the gaps. A diagram might
4256 // | ********* | <- sp
4260 // | stack_gap | <- gap | chunk_size
4262 // | ......... | <- gap_end v
4268 // 'sp' points the the current top-of-stack
4269 // 'gap' points to the stack_gap structure inside the gap
4270 // ***** indicates real stack data
4271 // ..... indicates gap
4272 // <empty> indicates unused
4276 void *gap_start, *next_gap_start, *gap_end;
4279 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4280 sp = next_gap_start;
4282 while ((StgPtr)gap > tso->sp) {
4284 // we're working in *bytes* now...
4285 gap_start = next_gap_start;
4286 gap_end = (void*) ((unsigned char*)gap_start - gap->gap_size * sizeof(W_));
4288 gap = gap->next_gap;
4289 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4291 chunk_size = (unsigned char*)gap_end - (unsigned char*)next_gap_start;
4293 memmove(sp, next_gap_start, chunk_size);
4296 tso->sp = (StgPtr)sp;
4300 /* -----------------------------------------------------------------------------
4303 * We have to prepare for GC - this means doing lazy black holing
4304 * here. We also take the opportunity to do stack squeezing if it's
4306 * -------------------------------------------------------------------------- */
4308 threadPaused(StgTSO *tso)
4310 if ( RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue )
4311 threadSqueezeStack(tso); // does black holing too
4313 threadLazyBlackHole(tso);
4316 /* -----------------------------------------------------------------------------
4318 * -------------------------------------------------------------------------- */
4322 printMutableList(generation *gen)
4327 debugBelch("@@ Mutable list %p: ", gen->mut_list);
4329 for (bd = gen->mut_list; bd != NULL; bd = bd->link) {
4330 for (p = bd->start; p < bd->free; p++) {
4331 debugBelch("%p (%s), ", (void *)*p, info_type((StgClosure *)*p));