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 /* Saved nursery (used for 2-space collector only)
129 static bdescr *saved_nursery;
130 static nat saved_n_blocks;
132 /* Data used for allocation area sizing.
134 static lnat new_blocks; // blocks allocated during this GC
135 static lnat new_scavd_blocks; // ditto, but depth-first blocks
136 static lnat g0s0_pcnt_kept = 30; // percentage of g0s0 live at last minor GC
138 /* Used to avoid long recursion due to selector thunks
140 static lnat thunk_selector_depth = 0;
141 #define MAX_THUNK_SELECTOR_DEPTH 8
143 /* -----------------------------------------------------------------------------
144 Static function declarations
145 -------------------------------------------------------------------------- */
147 static bdescr * gc_alloc_block ( step *stp );
148 static void mark_root ( StgClosure **root );
150 // Use a register argument for evacuate, if available.
152 #define REGPARM1 __attribute__((regparm(1)))
157 REGPARM1 static StgClosure * evacuate (StgClosure *q);
159 static void zero_static_object_list ( StgClosure* first_static );
161 static rtsBool traverse_weak_ptr_list ( void );
162 static void mark_weak_ptr_list ( StgWeak **list );
164 static StgClosure * eval_thunk_selector ( nat field, StgSelector * p );
167 static void scavenge ( step * );
168 static void scavenge_mark_stack ( void );
169 static void scavenge_stack ( StgPtr p, StgPtr stack_end );
170 static rtsBool scavenge_one ( StgPtr p );
171 static void scavenge_large ( step * );
172 static void scavenge_static ( void );
173 static void scavenge_mutable_list ( generation *g );
175 static void scavenge_large_bitmap ( StgPtr p,
176 StgLargeBitmap *large_bitmap,
179 #if 0 && defined(DEBUG)
180 static void gcCAFs ( void );
183 /* -----------------------------------------------------------------------------
184 inline functions etc. for dealing with the mark bitmap & stack.
185 -------------------------------------------------------------------------- */
187 #define MARK_STACK_BLOCKS 4
189 static bdescr *mark_stack_bdescr;
190 static StgPtr *mark_stack;
191 static StgPtr *mark_sp;
192 static StgPtr *mark_splim;
194 // Flag and pointers used for falling back to a linear scan when the
195 // mark stack overflows.
196 static rtsBool mark_stack_overflowed;
197 static bdescr *oldgen_scan_bd;
198 static StgPtr oldgen_scan;
200 STATIC_INLINE rtsBool
201 mark_stack_empty(void)
203 return mark_sp == mark_stack;
206 STATIC_INLINE rtsBool
207 mark_stack_full(void)
209 return mark_sp >= mark_splim;
213 reset_mark_stack(void)
215 mark_sp = mark_stack;
219 push_mark_stack(StgPtr p)
230 /* -----------------------------------------------------------------------------
231 Allocate a new to-space block in the given step.
232 -------------------------------------------------------------------------- */
235 gc_alloc_block(step *stp)
237 bdescr *bd = allocBlock();
238 bd->gen_no = stp->gen_no;
242 // blocks in to-space in generations up to and including N
243 // get the BF_EVACUATED flag.
244 if (stp->gen_no <= N) {
245 bd->flags = BF_EVACUATED;
250 // Start a new to-space block, chain it on after the previous one.
251 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;
267 gc_alloc_scavd_block(step *stp)
269 bdescr *bd = allocBlock();
270 bd->gen_no = stp->gen_no;
273 // blocks in to-space in generations up to and including N
274 // get the BF_EVACUATED flag.
275 if (stp->gen_no <= N) {
276 bd->flags = BF_EVACUATED;
281 bd->link = stp->blocks;
284 if (stp->scavd_hp != NULL) {
285 Bdescr(stp->scavd_hp)->free = stp->scavd_hp;
287 stp->scavd_hp = bd->start;
288 stp->scavd_hpLim = stp->scavd_hp + BLOCK_SIZE_W;
296 /* -----------------------------------------------------------------------------
299 Rough outline of the algorithm: for garbage collecting generation N
300 (and all younger generations):
302 - follow all pointers in the root set. the root set includes all
303 mutable objects in all generations (mutable_list).
305 - for each pointer, evacuate the object it points to into either
307 + to-space of the step given by step->to, which is the next
308 highest step in this generation or the first step in the next
309 generation if this is the last step.
311 + to-space of generations[evac_gen]->steps[0], if evac_gen != 0.
312 When we evacuate an object we attempt to evacuate
313 everything it points to into the same generation - this is
314 achieved by setting evac_gen to the desired generation. If
315 we can't do this, then an entry in the mut list has to
316 be made for the cross-generation pointer.
318 + if the object is already in a generation > N, then leave
321 - repeatedly scavenge to-space from each step in each generation
322 being collected until no more objects can be evacuated.
324 - free from-space in each step, and set from-space = to-space.
326 Locks held: sched_mutex
328 -------------------------------------------------------------------------- */
331 GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc )
335 lnat live, allocated, collected = 0, copied = 0, scavd_copied = 0;
336 lnat oldgen_saved_blocks = 0;
340 CostCentreStack *prev_CCS;
343 #if defined(DEBUG) && defined(GRAN)
344 IF_DEBUG(gc, debugBelch("@@ Starting garbage collection at %ld (%lx)\n",
348 #if defined(RTS_USER_SIGNALS)
353 // tell the STM to discard any cached closures its hoping to re-use
356 // tell the stats department that we've started a GC
359 // Init stats and print par specific (timing) info
360 PAR_TICKY_PAR_START();
362 // attribute any costs to CCS_GC
368 /* Approximate how much we allocated.
369 * Todo: only when generating stats?
371 allocated = calcAllocated();
373 /* Figure out which generation to collect
375 if (force_major_gc) {
376 N = RtsFlags.GcFlags.generations - 1;
380 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
381 if (generations[g].steps[0].n_blocks +
382 generations[g].steps[0].n_large_blocks
383 >= generations[g].max_blocks) {
387 major_gc = (N == RtsFlags.GcFlags.generations-1);
390 #ifdef RTS_GTK_FRONTPANEL
391 if (RtsFlags.GcFlags.frontpanel) {
392 updateFrontPanelBeforeGC(N);
396 // check stack sanity *before* GC (ToDo: check all threads)
398 // ToDo!: check sanity IF_DEBUG(sanity, checkTSOsSanity());
400 IF_DEBUG(sanity, checkFreeListSanity());
402 /* Initialise the static object lists
404 static_objects = END_OF_STATIC_LIST;
405 scavenged_static_objects = END_OF_STATIC_LIST;
407 /* Save the nursery if we're doing a two-space collection.
408 * g0s0->blocks will be used for to-space, so we need to get the
409 * nursery out of the way.
411 if (RtsFlags.GcFlags.generations == 1) {
412 saved_nursery = g0s0->blocks;
413 saved_n_blocks = g0s0->n_blocks;
418 /* Keep a count of how many new blocks we allocated during this GC
419 * (used for resizing the allocation area, later).
422 new_scavd_blocks = 0;
424 // Initialise to-space in all the generations/steps that we're
427 for (g = 0; g <= N; g++) {
429 // throw away the mutable list. Invariant: the mutable list
430 // always has at least one block; this means we can avoid a check for
431 // NULL in recordMutable().
433 freeChain(generations[g].mut_list);
434 generations[g].mut_list = allocBlock();
437 for (s = 0; s < generations[g].n_steps; s++) {
439 // generation 0, step 0 doesn't need to-space
440 if (g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1) {
444 stp = &generations[g].steps[s];
445 ASSERT(stp->gen_no == g);
447 // start a new to-space for this step.
448 stp->old_blocks = stp->blocks;
449 stp->n_old_blocks = stp->n_blocks;
451 // allocate the first to-space block; extra blocks will be
452 // chained on as necessary.
454 bd = gc_alloc_block(stp);
457 stp->scan = bd->start;
460 // allocate a block for "already scavenged" objects. This goes
461 // on the front of the stp->blocks list, so it won't be
462 // traversed by the scavenging sweep.
463 gc_alloc_scavd_block(stp);
465 // initialise the large object queues.
466 stp->new_large_objects = NULL;
467 stp->scavenged_large_objects = NULL;
468 stp->n_scavenged_large_blocks = 0;
470 // mark the large objects as not evacuated yet
471 for (bd = stp->large_objects; bd; bd = bd->link) {
472 bd->flags &= ~BF_EVACUATED;
475 // for a compacted step, we need to allocate the bitmap
476 if (stp->is_compacted) {
477 nat bitmap_size; // in bytes
478 bdescr *bitmap_bdescr;
481 bitmap_size = stp->n_old_blocks * BLOCK_SIZE / (sizeof(W_)*BITS_PER_BYTE);
483 if (bitmap_size > 0) {
484 bitmap_bdescr = allocGroup((lnat)BLOCK_ROUND_UP(bitmap_size)
486 stp->bitmap = bitmap_bdescr;
487 bitmap = bitmap_bdescr->start;
489 IF_DEBUG(gc, debugBelch("bitmap_size: %d, bitmap: %p",
490 bitmap_size, bitmap););
492 // don't forget to fill it with zeros!
493 memset(bitmap, 0, bitmap_size);
495 // For each block in this step, point to its bitmap from the
497 for (bd=stp->old_blocks; bd != NULL; bd = bd->link) {
498 bd->u.bitmap = bitmap;
499 bitmap += BLOCK_SIZE_W / (sizeof(W_)*BITS_PER_BYTE);
501 // Also at this point we set the BF_COMPACTED flag
502 // for this block. The invariant is that
503 // BF_COMPACTED is always unset, except during GC
504 // when it is set on those blocks which will be
506 bd->flags |= BF_COMPACTED;
513 /* make sure the older generations have at least one block to
514 * allocate into (this makes things easier for copy(), see below).
516 for (g = N+1; g < RtsFlags.GcFlags.generations; g++) {
517 for (s = 0; s < generations[g].n_steps; s++) {
518 stp = &generations[g].steps[s];
519 if (stp->hp_bd == NULL) {
520 ASSERT(stp->blocks == NULL);
521 bd = gc_alloc_block(stp);
525 if (stp->scavd_hp == NULL) {
526 gc_alloc_scavd_block(stp);
529 /* Set the scan pointer for older generations: remember we
530 * still have to scavenge objects that have been promoted. */
532 stp->scan_bd = stp->hp_bd;
533 stp->new_large_objects = NULL;
534 stp->scavenged_large_objects = NULL;
535 stp->n_scavenged_large_blocks = 0;
539 /* Allocate a mark stack if we're doing a major collection.
542 mark_stack_bdescr = allocGroup(MARK_STACK_BLOCKS);
543 mark_stack = (StgPtr *)mark_stack_bdescr->start;
544 mark_sp = mark_stack;
545 mark_splim = mark_stack + (MARK_STACK_BLOCKS * BLOCK_SIZE_W);
547 mark_stack_bdescr = NULL;
550 /* -----------------------------------------------------------------------
551 * follow all the roots that we know about:
552 * - mutable lists from each generation > N
553 * we want to *scavenge* these roots, not evacuate them: they're not
554 * going to move in this GC.
555 * Also: do them in reverse generation order. This is because we
556 * often want to promote objects that are pointed to by older
557 * generations early, so we don't have to repeatedly copy them.
558 * Doing the generations in reverse order ensures that we don't end
559 * up in the situation where we want to evac an object to gen 3 and
560 * it has already been evaced to gen 2.
564 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
565 generations[g].saved_mut_list = generations[g].mut_list;
566 generations[g].mut_list = allocBlock();
567 // mut_list always has at least one block.
570 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
571 IF_PAR_DEBUG(verbose, printMutableList(&generations[g]));
572 scavenge_mutable_list(&generations[g]);
574 for (st = generations[g].n_steps-1; st >= 0; st--) {
575 scavenge(&generations[g].steps[st]);
580 /* follow roots from the CAF list (used by GHCi)
585 /* follow all the roots that the application knows about.
588 get_roots(mark_root);
591 /* And don't forget to mark the TSO if we got here direct from
593 /* Not needed in a seq version?
595 CurrentTSO = (StgTSO *)MarkRoot((StgClosure *)CurrentTSO);
599 // Mark the entries in the GALA table of the parallel system
600 markLocalGAs(major_gc);
601 // Mark all entries on the list of pending fetches
602 markPendingFetches(major_gc);
605 /* Mark the weak pointer list, and prepare to detect dead weak
608 mark_weak_ptr_list(&weak_ptr_list);
609 old_weak_ptr_list = weak_ptr_list;
610 weak_ptr_list = NULL;
611 weak_stage = WeakPtrs;
613 /* The all_threads list is like the weak_ptr_list.
614 * See traverse_weak_ptr_list() for the details.
616 old_all_threads = all_threads;
617 all_threads = END_TSO_QUEUE;
618 resurrected_threads = END_TSO_QUEUE;
620 /* Mark the stable pointer table.
622 markStablePtrTable(mark_root);
624 /* -------------------------------------------------------------------------
625 * Repeatedly scavenge all the areas we know about until there's no
626 * more scavenging to be done.
633 // scavenge static objects
634 if (major_gc && static_objects != END_OF_STATIC_LIST) {
635 IF_DEBUG(sanity, checkStaticObjects(static_objects));
639 /* When scavenging the older generations: Objects may have been
640 * evacuated from generations <= N into older generations, and we
641 * need to scavenge these objects. We're going to try to ensure that
642 * any evacuations that occur move the objects into at least the
643 * same generation as the object being scavenged, otherwise we
644 * have to create new entries on the mutable list for the older
648 // scavenge each step in generations 0..maxgen
654 // scavenge objects in compacted generation
655 if (mark_stack_overflowed || oldgen_scan_bd != NULL ||
656 (mark_stack_bdescr != NULL && !mark_stack_empty())) {
657 scavenge_mark_stack();
661 for (gen = RtsFlags.GcFlags.generations; --gen >= 0; ) {
662 for (st = generations[gen].n_steps; --st >= 0; ) {
663 if (gen == 0 && st == 0 && RtsFlags.GcFlags.generations > 1) {
666 stp = &generations[gen].steps[st];
668 if (stp->hp_bd != stp->scan_bd || stp->scan < stp->hp) {
673 if (stp->new_large_objects != NULL) {
682 if (flag) { goto loop; }
684 // must be last... invariant is that everything is fully
685 // scavenged at this point.
686 if (traverse_weak_ptr_list()) { // returns rtsTrue if evaced something
691 /* Update the pointers from the "main thread" list - these are
692 * treated as weak pointers because we want to allow a main thread
693 * to get a BlockedOnDeadMVar exception in the same way as any other
694 * thread. Note that the threads should all have been retained by
695 * GC by virtue of being on the all_threads list, we're just
696 * updating pointers here.
701 for (m = main_threads; m != NULL; m = m->link) {
702 tso = (StgTSO *) isAlive((StgClosure *)m->tso);
704 barf("main thread has been GC'd");
711 // Reconstruct the Global Address tables used in GUM
712 rebuildGAtables(major_gc);
713 IF_DEBUG(sanity, checkLAGAtable(rtsTrue/*check closures, too*/));
716 // Now see which stable names are still alive.
719 // Tidy the end of the to-space chains
720 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
721 for (s = 0; s < generations[g].n_steps; s++) {
722 stp = &generations[g].steps[s];
723 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
724 ASSERT(Bdescr(stp->hp) == stp->hp_bd);
725 stp->hp_bd->free = stp->hp;
726 Bdescr(stp->scavd_hp)->free = stp->scavd_hp;
732 // We call processHeapClosureForDead() on every closure destroyed during
733 // the current garbage collection, so we invoke LdvCensusForDead().
734 if (RtsFlags.ProfFlags.doHeapProfile == HEAP_BY_LDV
735 || RtsFlags.ProfFlags.bioSelector != NULL)
739 // NO MORE EVACUATION AFTER THIS POINT!
740 // Finally: compaction of the oldest generation.
741 if (major_gc && oldest_gen->steps[0].is_compacted) {
742 // save number of blocks for stats
743 oldgen_saved_blocks = oldest_gen->steps[0].n_old_blocks;
747 IF_DEBUG(sanity, checkGlobalTSOList(rtsFalse));
749 /* run through all the generations/steps and tidy up
751 copied = new_blocks * BLOCK_SIZE_W;
752 scavd_copied = new_scavd_blocks * BLOCK_SIZE_W;
753 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
756 generations[g].collections++; // for stats
759 // Count the mutable list as bytes "copied" for the purposes of
760 // stats. Every mutable list is copied during every GC.
762 for (bd = generations[g].mut_list; bd != NULL; bd = bd->link) {
763 copied += (bd->free - bd->start) * sizeof(StgWord);
767 for (s = 0; s < generations[g].n_steps; s++) {
769 stp = &generations[g].steps[s];
771 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
772 // stats information: how much we copied
774 copied -= stp->hp_bd->start + BLOCK_SIZE_W -
776 scavd_copied -= (P_)(BLOCK_ROUND_UP(stp->scavd_hp)) - stp->scavd_hp;
780 // for generations we collected...
783 // rough calculation of garbage collected, for stats output
784 if (stp->is_compacted) {
785 collected += (oldgen_saved_blocks - stp->n_old_blocks) * BLOCK_SIZE_W;
787 if (g == 0 && s == 0) {
788 collected += countNurseryBlocks() * BLOCK_SIZE_W;
789 collected += alloc_blocks;
791 collected += stp->n_old_blocks * BLOCK_SIZE_W;
795 /* free old memory and shift to-space into from-space for all
796 * the collected steps (except the allocation area). These
797 * freed blocks will probaby be quickly recycled.
799 if (!(g == 0 && s == 0)) {
800 if (stp->is_compacted) {
801 // for a compacted step, just shift the new to-space
802 // onto the front of the now-compacted existing blocks.
803 for (bd = stp->blocks; bd != NULL; bd = bd->link) {
804 bd->flags &= ~BF_EVACUATED; // now from-space
806 // tack the new blocks on the end of the existing blocks
807 if (stp->old_blocks != NULL) {
808 for (bd = stp->old_blocks; bd != NULL; bd = next) {
811 bd->link = stp->blocks;
813 // NB. this step might not be compacted next
814 // time, so reset the BF_COMPACTED flags.
815 // They are set before GC if we're going to
816 // compact. (search for BF_COMPACTED above).
817 bd->flags &= ~BF_COMPACTED;
819 stp->blocks = stp->old_blocks;
821 // add the new blocks to the block tally
822 stp->n_blocks += stp->n_old_blocks;
824 freeChain(stp->old_blocks);
825 for (bd = stp->blocks; bd != NULL; bd = bd->link) {
826 bd->flags &= ~BF_EVACUATED; // now from-space
829 stp->old_blocks = NULL;
830 stp->n_old_blocks = 0;
833 /* LARGE OBJECTS. The current live large objects are chained on
834 * scavenged_large, having been moved during garbage
835 * collection from large_objects. Any objects left on
836 * large_objects list are therefore dead, so we free them here.
838 for (bd = stp->large_objects; bd != NULL; bd = next) {
844 // update the count of blocks used by large objects
845 for (bd = stp->scavenged_large_objects; bd != NULL; bd = bd->link) {
846 bd->flags &= ~BF_EVACUATED;
848 stp->large_objects = stp->scavenged_large_objects;
849 stp->n_large_blocks = stp->n_scavenged_large_blocks;
852 // for older generations...
854 /* For older generations, we need to append the
855 * scavenged_large_object list (i.e. large objects that have been
856 * promoted during this GC) to the large_object list for that step.
858 for (bd = stp->scavenged_large_objects; bd; bd = next) {
860 bd->flags &= ~BF_EVACUATED;
861 dbl_link_onto(bd, &stp->large_objects);
864 // add the new blocks we promoted during this GC
865 stp->n_large_blocks += stp->n_scavenged_large_blocks;
870 /* Reset the sizes of the older generations when we do a major
873 * CURRENT STRATEGY: make all generations except zero the same size.
874 * We have to stay within the maximum heap size, and leave a certain
875 * percentage of the maximum heap size available to allocate into.
877 if (major_gc && RtsFlags.GcFlags.generations > 1) {
878 nat live, size, min_alloc;
879 nat max = RtsFlags.GcFlags.maxHeapSize;
880 nat gens = RtsFlags.GcFlags.generations;
882 // live in the oldest generations
883 live = oldest_gen->steps[0].n_blocks +
884 oldest_gen->steps[0].n_large_blocks;
886 // default max size for all generations except zero
887 size = stg_max(live * RtsFlags.GcFlags.oldGenFactor,
888 RtsFlags.GcFlags.minOldGenSize);
890 // minimum size for generation zero
891 min_alloc = stg_max((RtsFlags.GcFlags.pcFreeHeap * max) / 200,
892 RtsFlags.GcFlags.minAllocAreaSize);
894 // Auto-enable compaction when the residency reaches a
895 // certain percentage of the maximum heap size (default: 30%).
896 if (RtsFlags.GcFlags.generations > 1 &&
897 (RtsFlags.GcFlags.compact ||
899 oldest_gen->steps[0].n_blocks >
900 (RtsFlags.GcFlags.compactThreshold * max) / 100))) {
901 oldest_gen->steps[0].is_compacted = 1;
902 // debugBelch("compaction: on\n", live);
904 oldest_gen->steps[0].is_compacted = 0;
905 // debugBelch("compaction: off\n", live);
908 // if we're going to go over the maximum heap size, reduce the
909 // size of the generations accordingly. The calculation is
910 // different if compaction is turned on, because we don't need
911 // to double the space required to collect the old generation.
914 // this test is necessary to ensure that the calculations
915 // below don't have any negative results - we're working
916 // with unsigned values here.
917 if (max < min_alloc) {
921 if (oldest_gen->steps[0].is_compacted) {
922 if ( (size + (size - 1) * (gens - 2) * 2) + min_alloc > max ) {
923 size = (max - min_alloc) / ((gens - 1) * 2 - 1);
926 if ( (size * (gens - 1) * 2) + min_alloc > max ) {
927 size = (max - min_alloc) / ((gens - 1) * 2);
937 debugBelch("live: %d, min_alloc: %d, size : %d, max = %d\n", live,
938 min_alloc, size, max);
941 for (g = 0; g < gens; g++) {
942 generations[g].max_blocks = size;
946 // Guess the amount of live data for stats.
949 /* Free the small objects allocated via allocate(), since this will
950 * all have been copied into G0S1 now.
952 if (small_alloc_list != NULL) {
953 freeChain(small_alloc_list);
955 small_alloc_list = NULL;
959 alloc_blocks_lim = RtsFlags.GcFlags.minAllocAreaSize;
961 // Start a new pinned_object_block
962 pinned_object_block = NULL;
964 /* Free the mark stack.
966 if (mark_stack_bdescr != NULL) {
967 freeGroup(mark_stack_bdescr);
972 for (g = 0; g <= N; g++) {
973 for (s = 0; s < generations[g].n_steps; s++) {
974 stp = &generations[g].steps[s];
975 if (stp->is_compacted && stp->bitmap != NULL) {
976 freeGroup(stp->bitmap);
981 /* Two-space collector:
982 * Free the old to-space, and estimate the amount of live data.
984 if (RtsFlags.GcFlags.generations == 1) {
987 if (g0s0->old_blocks != NULL) {
988 freeChain(g0s0->old_blocks);
990 for (bd = g0s0->blocks; bd != NULL; bd = bd->link) {
991 bd->flags = 0; // now from-space
993 g0s0->old_blocks = g0s0->blocks;
994 g0s0->n_old_blocks = g0s0->n_blocks;
995 g0s0->blocks = saved_nursery;
996 g0s0->n_blocks = saved_n_blocks;
998 /* For a two-space collector, we need to resize the nursery. */
1000 /* set up a new nursery. Allocate a nursery size based on a
1001 * function of the amount of live data (by default a factor of 2)
1002 * Use the blocks from the old nursery if possible, freeing up any
1005 * If we get near the maximum heap size, then adjust our nursery
1006 * size accordingly. If the nursery is the same size as the live
1007 * data (L), then we need 3L bytes. We can reduce the size of the
1008 * nursery to bring the required memory down near 2L bytes.
1010 * A normal 2-space collector would need 4L bytes to give the same
1011 * performance we get from 3L bytes, reducing to the same
1012 * performance at 2L bytes.
1014 blocks = g0s0->n_old_blocks;
1016 if ( RtsFlags.GcFlags.maxHeapSize != 0 &&
1017 blocks * RtsFlags.GcFlags.oldGenFactor * 2 >
1018 RtsFlags.GcFlags.maxHeapSize ) {
1019 long adjusted_blocks; // signed on purpose
1022 adjusted_blocks = (RtsFlags.GcFlags.maxHeapSize - 2 * blocks);
1023 IF_DEBUG(gc, debugBelch("@@ Near maximum heap size of 0x%x blocks, blocks = %d, adjusted to %ld", RtsFlags.GcFlags.maxHeapSize, blocks, adjusted_blocks));
1024 pc_free = adjusted_blocks * 100 / RtsFlags.GcFlags.maxHeapSize;
1025 if (pc_free < RtsFlags.GcFlags.pcFreeHeap) /* might even be < 0 */ {
1028 blocks = adjusted_blocks;
1031 blocks *= RtsFlags.GcFlags.oldGenFactor;
1032 if (blocks < RtsFlags.GcFlags.minAllocAreaSize) {
1033 blocks = RtsFlags.GcFlags.minAllocAreaSize;
1036 resizeNurseries(blocks);
1039 /* Generational collector:
1040 * If the user has given us a suggested heap size, adjust our
1041 * allocation area to make best use of the memory available.
1044 if (RtsFlags.GcFlags.heapSizeSuggestion) {
1046 nat needed = calcNeeded(); // approx blocks needed at next GC
1048 /* Guess how much will be live in generation 0 step 0 next time.
1049 * A good approximation is obtained by finding the
1050 * percentage of g0s0 that was live at the last minor GC.
1053 g0s0_pcnt_kept = (new_blocks * 100) / countNurseryBlocks();
1056 /* Estimate a size for the allocation area based on the
1057 * information available. We might end up going slightly under
1058 * or over the suggested heap size, but we should be pretty
1061 * Formula: suggested - needed
1062 * ----------------------------
1063 * 1 + g0s0_pcnt_kept/100
1065 * where 'needed' is the amount of memory needed at the next
1066 * collection for collecting all steps except g0s0.
1069 (((long)RtsFlags.GcFlags.heapSizeSuggestion - (long)needed) * 100) /
1070 (100 + (long)g0s0_pcnt_kept);
1072 if (blocks < (long)RtsFlags.GcFlags.minAllocAreaSize) {
1073 blocks = RtsFlags.GcFlags.minAllocAreaSize;
1076 resizeNurseries((nat)blocks);
1079 // we might have added extra large blocks to the nursery, so
1080 // resize back to minAllocAreaSize again.
1081 resizeNurseriesFixed(RtsFlags.GcFlags.minAllocAreaSize);
1085 // mark the garbage collected CAFs as dead
1086 #if 0 && defined(DEBUG) // doesn't work at the moment
1087 if (major_gc) { gcCAFs(); }
1091 // resetStaticObjectForRetainerProfiling() must be called before
1093 resetStaticObjectForRetainerProfiling();
1096 // zero the scavenged static object list
1098 zero_static_object_list(scavenged_static_objects);
1101 // Reset the nursery
1104 RELEASE_LOCK(&sched_mutex);
1106 // start any pending finalizers
1107 scheduleFinalizers(old_weak_ptr_list);
1109 // send exceptions to any threads which were about to die
1110 resurrectThreads(resurrected_threads);
1112 ACQUIRE_LOCK(&sched_mutex);
1114 // Update the stable pointer hash table.
1115 updateStablePtrTable(major_gc);
1117 // check sanity after GC
1118 IF_DEBUG(sanity, checkSanity());
1120 // extra GC trace info
1121 IF_DEBUG(gc, statDescribeGens());
1124 // symbol-table based profiling
1125 /* heapCensus(to_blocks); */ /* ToDo */
1128 // restore enclosing cost centre
1133 // check for memory leaks if sanity checking is on
1134 IF_DEBUG(sanity, memInventory());
1136 #ifdef RTS_GTK_FRONTPANEL
1137 if (RtsFlags.GcFlags.frontpanel) {
1138 updateFrontPanelAfterGC( N, live );
1142 // ok, GC over: tell the stats department what happened.
1143 stat_endGC(allocated, collected, live, copied, scavd_copied, N);
1145 #if defined(RTS_USER_SIGNALS)
1146 // unblock signals again
1147 unblockUserSignals();
1154 /* -----------------------------------------------------------------------------
1157 traverse_weak_ptr_list is called possibly many times during garbage
1158 collection. It returns a flag indicating whether it did any work
1159 (i.e. called evacuate on any live pointers).
1161 Invariant: traverse_weak_ptr_list is called when the heap is in an
1162 idempotent state. That means that there are no pending
1163 evacuate/scavenge operations. This invariant helps the weak
1164 pointer code decide which weak pointers are dead - if there are no
1165 new live weak pointers, then all the currently unreachable ones are
1168 For generational GC: we just don't try to finalize weak pointers in
1169 older generations than the one we're collecting. This could
1170 probably be optimised by keeping per-generation lists of weak
1171 pointers, but for a few weak pointers this scheme will work.
1173 There are three distinct stages to processing weak pointers:
1175 - weak_stage == WeakPtrs
1177 We process all the weak pointers whos keys are alive (evacuate
1178 their values and finalizers), and repeat until we can find no new
1179 live keys. If no live keys are found in this pass, then we
1180 evacuate the finalizers of all the dead weak pointers in order to
1183 - weak_stage == WeakThreads
1185 Now, we discover which *threads* are still alive. Pointers to
1186 threads from the all_threads and main thread lists are the
1187 weakest of all: a pointers from the finalizer of a dead weak
1188 pointer can keep a thread alive. Any threads found to be unreachable
1189 are evacuated and placed on the resurrected_threads list so we
1190 can send them a signal later.
1192 - weak_stage == WeakDone
1194 No more evacuation is done.
1196 -------------------------------------------------------------------------- */
1199 traverse_weak_ptr_list(void)
1201 StgWeak *w, **last_w, *next_w;
1203 rtsBool flag = rtsFalse;
1205 switch (weak_stage) {
1211 /* doesn't matter where we evacuate values/finalizers to, since
1212 * these pointers are treated as roots (iff the keys are alive).
1216 last_w = &old_weak_ptr_list;
1217 for (w = old_weak_ptr_list; w != NULL; w = next_w) {
1219 /* There might be a DEAD_WEAK on the list if finalizeWeak# was
1220 * called on a live weak pointer object. Just remove it.
1222 if (w->header.info == &stg_DEAD_WEAK_info) {
1223 next_w = ((StgDeadWeak *)w)->link;
1228 switch (get_itbl(w)->type) {
1231 next_w = (StgWeak *)((StgEvacuated *)w)->evacuee;
1236 /* Now, check whether the key is reachable.
1238 new = isAlive(w->key);
1241 // evacuate the value and finalizer
1242 w->value = evacuate(w->value);
1243 w->finalizer = evacuate(w->finalizer);
1244 // remove this weak ptr from the old_weak_ptr list
1246 // and put it on the new weak ptr list
1248 w->link = weak_ptr_list;
1251 IF_DEBUG(weak, debugBelch("Weak pointer still alive at %p -> %p",
1256 last_w = &(w->link);
1262 barf("traverse_weak_ptr_list: not WEAK");
1266 /* If we didn't make any changes, then we can go round and kill all
1267 * the dead weak pointers. The old_weak_ptr list is used as a list
1268 * of pending finalizers later on.
1270 if (flag == rtsFalse) {
1271 for (w = old_weak_ptr_list; w; w = w->link) {
1272 w->finalizer = evacuate(w->finalizer);
1275 // Next, move to the WeakThreads stage after fully
1276 // scavenging the finalizers we've just evacuated.
1277 weak_stage = WeakThreads;
1283 /* Now deal with the all_threads list, which behaves somewhat like
1284 * the weak ptr list. If we discover any threads that are about to
1285 * become garbage, we wake them up and administer an exception.
1288 StgTSO *t, *tmp, *next, **prev;
1290 prev = &old_all_threads;
1291 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1293 tmp = (StgTSO *)isAlive((StgClosure *)t);
1299 ASSERT(get_itbl(t)->type == TSO);
1300 switch (t->what_next) {
1301 case ThreadRelocated:
1306 case ThreadComplete:
1307 // finshed or died. The thread might still be alive, but we
1308 // don't keep it on the all_threads list. Don't forget to
1309 // stub out its global_link field.
1310 next = t->global_link;
1311 t->global_link = END_TSO_QUEUE;
1318 // Threads blocked on black holes: if the black hole
1319 // is alive, then the thread is alive too.
1320 if (tmp == NULL && t->why_blocked == BlockedOnBlackHole) {
1321 if (isAlive(t->block_info.closure)) {
1322 t = (StgTSO *)evacuate((StgClosure *)t);
1329 // not alive (yet): leave this thread on the
1330 // old_all_threads list.
1331 prev = &(t->global_link);
1332 next = t->global_link;
1335 // alive: move this thread onto the all_threads list.
1336 next = t->global_link;
1337 t->global_link = all_threads;
1344 /* If we evacuated any threads, we need to go back to the scavenger.
1346 if (flag) return rtsTrue;
1348 /* And resurrect any threads which were about to become garbage.
1351 StgTSO *t, *tmp, *next;
1352 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1353 next = t->global_link;
1354 tmp = (StgTSO *)evacuate((StgClosure *)t);
1355 tmp->global_link = resurrected_threads;
1356 resurrected_threads = tmp;
1360 /* Finally, we can update the blackhole_queue. This queue
1361 * simply strings together TSOs blocked on black holes, it is
1362 * not intended to keep anything alive. Hence, we do not follow
1363 * pointers on the blackhole_queue until now, when we have
1364 * determined which TSOs are otherwise reachable. We know at
1365 * this point that all TSOs have been evacuated, however.
1369 for (pt = &blackhole_queue; *pt != END_TSO_QUEUE; pt = &((*pt)->link)) {
1370 *pt = (StgTSO *)isAlive((StgClosure *)*pt);
1371 ASSERT(*pt != NULL);
1375 weak_stage = WeakDone; // *now* we're done,
1376 return rtsTrue; // but one more round of scavenging, please
1379 barf("traverse_weak_ptr_list");
1385 /* -----------------------------------------------------------------------------
1386 After GC, the live weak pointer list may have forwarding pointers
1387 on it, because a weak pointer object was evacuated after being
1388 moved to the live weak pointer list. We remove those forwarding
1391 Also, we don't consider weak pointer objects to be reachable, but
1392 we must nevertheless consider them to be "live" and retain them.
1393 Therefore any weak pointer objects which haven't as yet been
1394 evacuated need to be evacuated now.
1395 -------------------------------------------------------------------------- */
1399 mark_weak_ptr_list ( StgWeak **list )
1401 StgWeak *w, **last_w;
1404 for (w = *list; w; w = w->link) {
1405 // w might be WEAK, EVACUATED, or DEAD_WEAK (actually CON_STATIC) here
1406 ASSERT(w->header.info == &stg_DEAD_WEAK_info
1407 || get_itbl(w)->type == WEAK || get_itbl(w)->type == EVACUATED);
1408 w = (StgWeak *)evacuate((StgClosure *)w);
1410 last_w = &(w->link);
1414 /* -----------------------------------------------------------------------------
1415 isAlive determines whether the given closure is still alive (after
1416 a garbage collection) or not. It returns the new address of the
1417 closure if it is alive, or NULL otherwise.
1419 NOTE: Use it before compaction only!
1420 -------------------------------------------------------------------------- */
1424 isAlive(StgClosure *p)
1426 const StgInfoTable *info;
1431 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
1434 // ignore static closures
1436 // ToDo: for static closures, check the static link field.
1437 // Problem here is that we sometimes don't set the link field, eg.
1438 // for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
1440 if (!HEAP_ALLOCED(p)) {
1444 // ignore closures in generations that we're not collecting.
1446 if (bd->gen_no > N) {
1450 // if it's a pointer into to-space, then we're done
1451 if (bd->flags & BF_EVACUATED) {
1455 // large objects use the evacuated flag
1456 if (bd->flags & BF_LARGE) {
1460 // check the mark bit for compacted steps
1461 if ((bd->flags & BF_COMPACTED) && is_marked((P_)p,bd)) {
1465 switch (info->type) {
1470 case IND_OLDGEN: // rely on compatible layout with StgInd
1471 case IND_OLDGEN_PERM:
1472 // follow indirections
1473 p = ((StgInd *)p)->indirectee;
1478 return ((StgEvacuated *)p)->evacuee;
1481 if (((StgTSO *)p)->what_next == ThreadRelocated) {
1482 p = (StgClosure *)((StgTSO *)p)->link;
1495 mark_root(StgClosure **root)
1497 *root = evacuate(*root);
1501 upd_evacuee(StgClosure *p, StgClosure *dest)
1503 // not true: (ToDo: perhaps it should be)
1504 // ASSERT(Bdescr((P_)dest)->flags & BF_EVACUATED);
1505 SET_INFO(p, &stg_EVACUATED_info);
1506 ((StgEvacuated *)p)->evacuee = dest;
1510 STATIC_INLINE StgClosure *
1511 copy(StgClosure *src, nat size, step *stp)
1517 nat size_org = size;
1520 TICK_GC_WORDS_COPIED(size);
1521 /* Find out where we're going, using the handy "to" pointer in
1522 * the step of the source object. If it turns out we need to
1523 * evacuate to an older generation, adjust it here (see comment
1526 if (stp->gen_no < evac_gen) {
1527 #ifdef NO_EAGER_PROMOTION
1528 failed_to_evac = rtsTrue;
1530 stp = &generations[evac_gen].steps[0];
1534 /* chain a new block onto the to-space for the destination step if
1537 if (stp->hp + size >= stp->hpLim) {
1538 gc_alloc_block(stp);
1543 stp->hp = to + size;
1544 for (i = 0; i < size; i++) { // unroll for small i
1547 upd_evacuee((StgClosure *)from,(StgClosure *)to);
1550 // We store the size of the just evacuated object in the LDV word so that
1551 // the profiler can guess the position of the next object later.
1552 SET_EVACUAEE_FOR_LDV(from, size_org);
1554 return (StgClosure *)to;
1557 // Same as copy() above, except the object will be allocated in memory
1558 // that will not be scavenged. Used for object that have no pointer
1560 STATIC_INLINE StgClosure *
1561 copy_noscav(StgClosure *src, nat size, step *stp)
1567 nat size_org = size;
1570 TICK_GC_WORDS_COPIED(size);
1571 /* Find out where we're going, using the handy "to" pointer in
1572 * the step of the source object. If it turns out we need to
1573 * evacuate to an older generation, adjust it here (see comment
1576 if (stp->gen_no < evac_gen) {
1577 #ifdef NO_EAGER_PROMOTION
1578 failed_to_evac = rtsTrue;
1580 stp = &generations[evac_gen].steps[0];
1584 /* chain a new block onto the to-space for the destination step if
1587 if (stp->scavd_hp + size >= stp->scavd_hpLim) {
1588 gc_alloc_scavd_block(stp);
1593 stp->scavd_hp = to + size;
1594 for (i = 0; i < size; i++) { // unroll for small i
1597 upd_evacuee((StgClosure *)from,(StgClosure *)to);
1600 // We store the size of the just evacuated object in the LDV word so that
1601 // the profiler can guess the position of the next object later.
1602 SET_EVACUAEE_FOR_LDV(from, size_org);
1604 return (StgClosure *)to;
1607 /* Special version of copy() for when we only want to copy the info
1608 * pointer of an object, but reserve some padding after it. This is
1609 * used to optimise evacuation of BLACKHOLEs.
1614 copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *stp)
1619 nat size_to_copy_org = size_to_copy;
1622 TICK_GC_WORDS_COPIED(size_to_copy);
1623 if (stp->gen_no < evac_gen) {
1624 #ifdef NO_EAGER_PROMOTION
1625 failed_to_evac = rtsTrue;
1627 stp = &generations[evac_gen].steps[0];
1631 if (stp->hp + size_to_reserve >= stp->hpLim) {
1632 gc_alloc_block(stp);
1635 for(to = stp->hp, from = (P_)src; size_to_copy>0; --size_to_copy) {
1640 stp->hp += size_to_reserve;
1641 upd_evacuee(src,(StgClosure *)dest);
1643 // We store the size of the just evacuated object in the LDV word so that
1644 // the profiler can guess the position of the next object later.
1645 // size_to_copy_org is wrong because the closure already occupies size_to_reserve
1647 SET_EVACUAEE_FOR_LDV(src, size_to_reserve);
1649 if (size_to_reserve - size_to_copy_org > 0)
1650 FILL_SLOP(stp->hp - 1, (int)(size_to_reserve - size_to_copy_org));
1652 return (StgClosure *)dest;
1656 /* -----------------------------------------------------------------------------
1657 Evacuate a large object
1659 This just consists of removing the object from the (doubly-linked)
1660 step->large_objects list, and linking it on to the (singly-linked)
1661 step->new_large_objects list, from where it will be scavenged later.
1663 Convention: bd->flags has BF_EVACUATED set for a large object
1664 that has been evacuated, or unset otherwise.
1665 -------------------------------------------------------------------------- */
1669 evacuate_large(StgPtr p)
1671 bdescr *bd = Bdescr(p);
1674 // object must be at the beginning of the block (or be a ByteArray)
1675 ASSERT(get_itbl((StgClosure *)p)->type == ARR_WORDS ||
1676 (((W_)p & BLOCK_MASK) == 0));
1678 // already evacuated?
1679 if (bd->flags & BF_EVACUATED) {
1680 /* Don't forget to set the failed_to_evac flag if we didn't get
1681 * the desired destination (see comments in evacuate()).
1683 if (bd->gen_no < evac_gen) {
1684 failed_to_evac = rtsTrue;
1685 TICK_GC_FAILED_PROMOTION();
1691 // remove from large_object list
1693 bd->u.back->link = bd->link;
1694 } else { // first object in the list
1695 stp->large_objects = bd->link;
1698 bd->link->u.back = bd->u.back;
1701 /* link it on to the evacuated large object list of the destination step
1704 if (stp->gen_no < evac_gen) {
1705 #ifdef NO_EAGER_PROMOTION
1706 failed_to_evac = rtsTrue;
1708 stp = &generations[evac_gen].steps[0];
1713 bd->gen_no = stp->gen_no;
1714 bd->link = stp->new_large_objects;
1715 stp->new_large_objects = bd;
1716 bd->flags |= BF_EVACUATED;
1719 /* -----------------------------------------------------------------------------
1722 This is called (eventually) for every live object in the system.
1724 The caller to evacuate specifies a desired generation in the
1725 evac_gen global variable. The following conditions apply to
1726 evacuating an object which resides in generation M when we're
1727 collecting up to generation N
1731 else evac to step->to
1733 if M < evac_gen evac to evac_gen, step 0
1735 if the object is already evacuated, then we check which generation
1738 if M >= evac_gen do nothing
1739 if M < evac_gen set failed_to_evac flag to indicate that we
1740 didn't manage to evacuate this object into evac_gen.
1745 evacuate() is the single most important function performance-wise
1746 in the GC. Various things have been tried to speed it up, but as
1747 far as I can tell the code generated by gcc 3.2 with -O2 is about
1748 as good as it's going to get. We pass the argument to evacuate()
1749 in a register using the 'regparm' attribute (see the prototype for
1750 evacuate() near the top of this file).
1752 Changing evacuate() to take an (StgClosure **) rather than
1753 returning the new pointer seems attractive, because we can avoid
1754 writing back the pointer when it hasn't changed (eg. for a static
1755 object, or an object in a generation > N). However, I tried it and
1756 it doesn't help. One reason is that the (StgClosure **) pointer
1757 gets spilled to the stack inside evacuate(), resulting in far more
1758 extra reads/writes than we save.
1759 -------------------------------------------------------------------------- */
1761 REGPARM1 static StgClosure *
1762 evacuate(StgClosure *q)
1769 const StgInfoTable *info;
1772 ASSERT(LOOKS_LIKE_CLOSURE_PTR(q));
1774 if (!HEAP_ALLOCED(q)) {
1776 if (!major_gc) return q;
1779 switch (info->type) {
1782 if (info->srt_bitmap != 0 &&
1783 *THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
1784 *THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
1785 static_objects = (StgClosure *)q;
1790 if (info->srt_bitmap != 0 &&
1791 *FUN_STATIC_LINK((StgClosure *)q) == NULL) {
1792 *FUN_STATIC_LINK((StgClosure *)q) = static_objects;
1793 static_objects = (StgClosure *)q;
1798 /* If q->saved_info != NULL, then it's a revertible CAF - it'll be
1799 * on the CAF list, so don't do anything with it here (we'll
1800 * scavenge it later).
1802 if (((StgIndStatic *)q)->saved_info == NULL
1803 && *IND_STATIC_LINK((StgClosure *)q) == NULL) {
1804 *IND_STATIC_LINK((StgClosure *)q) = static_objects;
1805 static_objects = (StgClosure *)q;
1810 if (*STATIC_LINK(info,(StgClosure *)q) == NULL) {
1811 *STATIC_LINK(info,(StgClosure *)q) = static_objects;
1812 static_objects = (StgClosure *)q;
1816 case CONSTR_INTLIKE:
1817 case CONSTR_CHARLIKE:
1818 case CONSTR_NOCAF_STATIC:
1819 /* no need to put these on the static linked list, they don't need
1825 barf("evacuate(static): strange closure type %d", (int)(info->type));
1831 if (bd->gen_no > N) {
1832 /* Can't evacuate this object, because it's in a generation
1833 * older than the ones we're collecting. Let's hope that it's
1834 * in evac_gen or older, or we will have to arrange to track
1835 * this pointer using the mutable list.
1837 if (bd->gen_no < evac_gen) {
1839 failed_to_evac = rtsTrue;
1840 TICK_GC_FAILED_PROMOTION();
1845 if ((bd->flags & (BF_LARGE | BF_COMPACTED | BF_EVACUATED)) != 0) {
1847 /* pointer into to-space: just return it. This normally
1848 * shouldn't happen, but alllowing it makes certain things
1849 * slightly easier (eg. the mutable list can contain the same
1850 * object twice, for example).
1852 if (bd->flags & BF_EVACUATED) {
1853 if (bd->gen_no < evac_gen) {
1854 failed_to_evac = rtsTrue;
1855 TICK_GC_FAILED_PROMOTION();
1860 /* evacuate large objects by re-linking them onto a different list.
1862 if (bd->flags & BF_LARGE) {
1864 if (info->type == TSO &&
1865 ((StgTSO *)q)->what_next == ThreadRelocated) {
1866 q = (StgClosure *)((StgTSO *)q)->link;
1869 evacuate_large((P_)q);
1873 /* If the object is in a step that we're compacting, then we
1874 * need to use an alternative evacuate procedure.
1876 if (bd->flags & BF_COMPACTED) {
1877 if (!is_marked((P_)q,bd)) {
1879 if (mark_stack_full()) {
1880 mark_stack_overflowed = rtsTrue;
1883 push_mark_stack((P_)q);
1893 switch (info->type) {
1897 return copy(q,sizeW_fromITBL(info),stp);
1901 StgWord w = (StgWord)q->payload[0];
1902 if (q->header.info == Czh_con_info &&
1903 // unsigned, so always true: (StgChar)w >= MIN_CHARLIKE &&
1904 (StgChar)w <= MAX_CHARLIKE) {
1905 return (StgClosure *)CHARLIKE_CLOSURE((StgChar)w);
1907 if (q->header.info == Izh_con_info &&
1908 (StgInt)w >= MIN_INTLIKE && (StgInt)w <= MAX_INTLIKE) {
1909 return (StgClosure *)INTLIKE_CLOSURE((StgInt)w);
1912 return copy_noscav(q,sizeofW(StgHeader)+1,stp);
1918 return copy(q,sizeofW(StgHeader)+1,stp);
1922 return copy(q,sizeofW(StgThunk)+1,stp);
1927 #ifdef NO_PROMOTE_THUNKS
1928 if (bd->gen_no == 0 &&
1929 bd->step->no != 0 &&
1930 bd->step->no == generations[bd->gen_no].n_steps-1) {
1934 return copy(q,sizeofW(StgThunk)+2,stp);
1941 return copy(q,sizeofW(StgHeader)+2,stp);
1944 return copy_noscav(q,sizeofW(StgHeader)+2,stp);
1947 return copy(q,thunk_sizeW_fromITBL(info),stp);
1952 case IND_OLDGEN_PERM:
1955 return copy(q,sizeW_fromITBL(info),stp);
1958 return copy(q,bco_sizeW((StgBCO *)q),stp);
1961 case SE_CAF_BLACKHOLE:
1964 return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
1966 case THUNK_SELECTOR:
1970 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
1971 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1974 p = eval_thunk_selector(info->layout.selector_offset,
1978 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1981 // q is still BLACKHOLE'd.
1982 thunk_selector_depth++;
1985 // Update the THUNK_SELECTOR with an indirection to the
1986 // EVACUATED closure now at p. Why do this rather than
1987 // upd_evacuee(q,p)? Because we have an invariant that an
1988 // EVACUATED closure always points to an object in the
1989 // same or an older generation (required by the short-cut
1990 // test in the EVACUATED case, below).
1991 SET_INFO(q, &stg_IND_info);
1992 ((StgInd *)q)->indirectee = p;
1995 // We store the size of the just evacuated object in the
1996 // LDV word so that the profiler can guess the position of
1997 // the next object later.
1998 SET_EVACUAEE_FOR_LDV(q, THUNK_SELECTOR_sizeW());
2006 // follow chains of indirections, don't evacuate them
2007 q = ((StgInd*)q)->indirectee;
2019 case CATCH_STM_FRAME:
2020 case CATCH_RETRY_FRAME:
2021 case ATOMICALLY_FRAME:
2022 // shouldn't see these
2023 barf("evacuate: stack frame at %p\n", q);
2026 return copy(q,pap_sizeW((StgPAP*)q),stp);
2029 return copy(q,ap_sizeW((StgAP*)q),stp);
2032 return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp);
2035 /* Already evacuated, just return the forwarding address.
2036 * HOWEVER: if the requested destination generation (evac_gen) is
2037 * older than the actual generation (because the object was
2038 * already evacuated to a younger generation) then we have to
2039 * set the failed_to_evac flag to indicate that we couldn't
2040 * manage to promote the object to the desired generation.
2043 * Optimisation: the check is fairly expensive, but we can often
2044 * shortcut it if either the required generation is 0, or the
2045 * current object (the EVACUATED) is in a high enough generation.
2046 * We know that an EVACUATED always points to an object in the
2047 * same or an older generation. stp is the lowest step that the
2048 * current object would be evacuated to, so we only do the full
2049 * check if stp is too low.
2051 if (evac_gen > 0 && stp->gen_no < evac_gen) { // optimisation
2052 StgClosure *p = ((StgEvacuated*)q)->evacuee;
2053 if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < evac_gen) {
2054 failed_to_evac = rtsTrue;
2055 TICK_GC_FAILED_PROMOTION();
2058 return ((StgEvacuated*)q)->evacuee;
2061 // just copy the block
2062 return copy_noscav(q,arr_words_sizeW((StgArrWords *)q),stp);
2065 case MUT_ARR_PTRS_FROZEN:
2066 case MUT_ARR_PTRS_FROZEN0:
2067 // just copy the block
2068 return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
2072 StgTSO *tso = (StgTSO *)q;
2074 /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
2076 if (tso->what_next == ThreadRelocated) {
2077 q = (StgClosure *)tso->link;
2081 /* To evacuate a small TSO, we need to relocate the update frame
2088 new_tso = (StgTSO *)copyPart((StgClosure *)tso,
2090 sizeofW(StgTSO), stp);
2091 move_TSO(tso, new_tso);
2092 for (p = tso->sp, q = new_tso->sp;
2093 p < tso->stack+tso->stack_size;) {
2097 return (StgClosure *)new_tso;
2104 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
2105 to = copy(q,BLACKHOLE_sizeW(),stp);
2106 //ToDo: derive size etc from reverted IP
2107 //to = copy(q,size,stp);
2109 debugBelch("@@ evacuate: RBH %p (%s) to %p (%s)",
2110 q, info_type(q), to, info_type(to)));
2115 ASSERT(sizeofW(StgBlockedFetch) >= MIN_NONUPD_SIZE);
2116 to = copy(q,sizeofW(StgBlockedFetch),stp);
2118 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
2119 q, info_type(q), to, info_type(to)));
2126 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
2127 to = copy(q,sizeofW(StgFetchMe),stp);
2129 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
2130 q, info_type(q), to, info_type(to)));
2134 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
2135 to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
2137 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
2138 q, info_type(q), to, info_type(to)));
2143 return copy(q,sizeofW(StgTRecHeader),stp);
2145 case TVAR_WAIT_QUEUE:
2146 return copy(q,sizeofW(StgTVarWaitQueue),stp);
2149 return copy(q,sizeofW(StgTVar),stp);
2152 return copy(q,sizeofW(StgTRecChunk),stp);
2155 barf("evacuate: strange closure type %d", (int)(info->type));
2161 /* -----------------------------------------------------------------------------
2162 Evaluate a THUNK_SELECTOR if possible.
2164 returns: NULL if we couldn't evaluate this THUNK_SELECTOR, or
2165 a closure pointer if we evaluated it and this is the result. Note
2166 that "evaluating" the THUNK_SELECTOR doesn't necessarily mean
2167 reducing it to HNF, just that we have eliminated the selection.
2168 The result might be another thunk, or even another THUNK_SELECTOR.
2170 If the return value is non-NULL, the original selector thunk has
2171 been BLACKHOLE'd, and should be updated with an indirection or a
2172 forwarding pointer. If the return value is NULL, then the selector
2176 ToDo: the treatment of THUNK_SELECTORS could be improved in the
2177 following way (from a suggestion by Ian Lynagh):
2179 We can have a chain like this:
2183 |-----> sel_0 --> (a,b)
2185 |-----> sel_0 --> ...
2187 and the depth limit means we don't go all the way to the end of the
2188 chain, which results in a space leak. This affects the recursive
2189 call to evacuate() in the THUNK_SELECTOR case in evacuate(): *not*
2190 the recursive call to eval_thunk_selector() in
2191 eval_thunk_selector().
2193 We could eliminate the depth bound in this case, in the following
2196 - traverse the chain once to discover the *value* of the
2197 THUNK_SELECTOR. Mark all THUNK_SELECTORS that we
2198 visit on the way as having been visited already (somehow).
2200 - in a second pass, traverse the chain again updating all
2201 THUNK_SEELCTORS that we find on the way with indirections to
2204 - if we encounter a "marked" THUNK_SELECTOR in a normal
2205 evacuate(), we konw it can't be updated so just evac it.
2207 Program that illustrates the problem:
2210 foo (x:xs) = let (ys, zs) = foo xs
2211 in if x >= 0 then (x:ys, zs) else (ys, x:zs)
2213 main = bar [1..(100000000::Int)]
2214 bar xs = (\(ys, zs) -> print ys >> print zs) (foo xs)
2216 -------------------------------------------------------------------------- */
2218 static inline rtsBool
2219 is_to_space ( StgClosure *p )
2223 bd = Bdescr((StgPtr)p);
2224 if (HEAP_ALLOCED(p) &&
2225 ((bd->flags & BF_EVACUATED)
2226 || ((bd->flags & BF_COMPACTED) &&
2227 is_marked((P_)p,bd)))) {
2235 eval_thunk_selector( nat field, StgSelector * p )
2238 const StgInfoTable *info_ptr;
2239 StgClosure *selectee;
2241 selectee = p->selectee;
2243 // Save the real info pointer (NOTE: not the same as get_itbl()).
2244 info_ptr = p->header.info;
2246 // If the THUNK_SELECTOR is in a generation that we are not
2247 // collecting, then bail out early. We won't be able to save any
2248 // space in any case, and updating with an indirection is trickier
2250 if (Bdescr((StgPtr)p)->gen_no > N) {
2254 // BLACKHOLE the selector thunk, since it is now under evaluation.
2255 // This is important to stop us going into an infinite loop if
2256 // this selector thunk eventually refers to itself.
2257 SET_INFO(p,&stg_BLACKHOLE_info);
2261 // We don't want to end up in to-space, because this causes
2262 // problems when the GC later tries to evacuate the result of
2263 // eval_thunk_selector(). There are various ways this could
2266 // 1. following an IND_STATIC
2268 // 2. when the old generation is compacted, the mark phase updates
2269 // from-space pointers to be to-space pointers, and we can't
2270 // reliably tell which we're following (eg. from an IND_STATIC).
2272 // 3. compacting GC again: if we're looking at a constructor in
2273 // the compacted generation, it might point directly to objects
2274 // in to-space. We must bale out here, otherwise doing the selection
2275 // will result in a to-space pointer being returned.
2277 // (1) is dealt with using a BF_EVACUATED test on the
2278 // selectee. (2) and (3): we can tell if we're looking at an
2279 // object in the compacted generation that might point to
2280 // to-space objects by testing that (a) it is BF_COMPACTED, (b)
2281 // the compacted generation is being collected, and (c) the
2282 // object is marked. Only a marked object may have pointers that
2283 // point to to-space objects, because that happens when
2286 // The to-space test is now embodied in the in_to_space() inline
2287 // function, as it is re-used below.
2289 if (is_to_space(selectee)) {
2293 info = get_itbl(selectee);
2294 switch (info->type) {
2302 case CONSTR_NOCAF_STATIC:
2303 // check that the size is in range
2304 ASSERT(field < (StgWord32)(info->layout.payload.ptrs +
2305 info->layout.payload.nptrs));
2307 // Select the right field from the constructor, and check
2308 // that the result isn't in to-space. It might be in
2309 // to-space if, for example, this constructor contains
2310 // pointers to younger-gen objects (and is on the mut-once
2315 q = selectee->payload[field];
2316 if (is_to_space(q)) {
2326 case IND_OLDGEN_PERM:
2328 selectee = ((StgInd *)selectee)->indirectee;
2332 // We don't follow pointers into to-space; the constructor
2333 // has already been evacuated, so we won't save any space
2334 // leaks by evaluating this selector thunk anyhow.
2337 case THUNK_SELECTOR:
2341 // check that we don't recurse too much, re-using the
2342 // depth bound also used in evacuate().
2343 if (thunk_selector_depth >= MAX_THUNK_SELECTOR_DEPTH) {
2346 thunk_selector_depth++;
2348 val = eval_thunk_selector(info->layout.selector_offset,
2349 (StgSelector *)selectee);
2351 thunk_selector_depth--;
2356 // We evaluated this selector thunk, so update it with
2357 // an indirection. NOTE: we don't use UPD_IND here,
2358 // because we are guaranteed that p is in a generation
2359 // that we are collecting, and we never want to put the
2360 // indirection on a mutable list.
2362 // For the purposes of LDV profiling, we have destroyed
2363 // the original selector thunk.
2364 SET_INFO(p, info_ptr);
2365 LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(selectee);
2367 ((StgInd *)selectee)->indirectee = val;
2368 SET_INFO(selectee,&stg_IND_info);
2370 // For the purposes of LDV profiling, we have created an
2372 LDV_RECORD_CREATE(selectee);
2389 case SE_CAF_BLACKHOLE:
2401 // not evaluated yet
2405 barf("eval_thunk_selector: strange selectee %d",
2410 // We didn't manage to evaluate this thunk; restore the old info pointer
2411 SET_INFO(p, info_ptr);
2415 /* -----------------------------------------------------------------------------
2416 move_TSO is called to update the TSO structure after it has been
2417 moved from one place to another.
2418 -------------------------------------------------------------------------- */
2421 move_TSO (StgTSO *src, StgTSO *dest)
2425 // relocate the stack pointer...
2426 diff = (StgPtr)dest - (StgPtr)src; // In *words*
2427 dest->sp = (StgPtr)dest->sp + diff;
2430 /* Similar to scavenge_large_bitmap(), but we don't write back the
2431 * pointers we get back from evacuate().
2434 scavenge_large_srt_bitmap( StgLargeSRT *large_srt )
2441 bitmap = large_srt->l.bitmap[b];
2442 size = (nat)large_srt->l.size;
2443 p = (StgClosure **)large_srt->srt;
2444 for (i = 0; i < size; ) {
2445 if ((bitmap & 1) != 0) {
2450 if (i % BITS_IN(W_) == 0) {
2452 bitmap = large_srt->l.bitmap[b];
2454 bitmap = bitmap >> 1;
2459 /* evacuate the SRT. If srt_bitmap is zero, then there isn't an
2460 * srt field in the info table. That's ok, because we'll
2461 * never dereference it.
2464 scavenge_srt (StgClosure **srt, nat srt_bitmap)
2469 bitmap = srt_bitmap;
2472 if (bitmap == (StgHalfWord)(-1)) {
2473 scavenge_large_srt_bitmap( (StgLargeSRT *)srt );
2477 while (bitmap != 0) {
2478 if ((bitmap & 1) != 0) {
2479 #ifdef ENABLE_WIN32_DLL_SUPPORT
2480 // Special-case to handle references to closures hiding out in DLLs, since
2481 // double indirections required to get at those. The code generator knows
2482 // which is which when generating the SRT, so it stores the (indirect)
2483 // reference to the DLL closure in the table by first adding one to it.
2484 // We check for this here, and undo the addition before evacuating it.
2486 // If the SRT entry hasn't got bit 0 set, the SRT entry points to a
2487 // closure that's fixed at link-time, and no extra magic is required.
2488 if ( (unsigned long)(*srt) & 0x1 ) {
2489 evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
2498 bitmap = bitmap >> 1;
2504 scavenge_thunk_srt(const StgInfoTable *info)
2506 StgThunkInfoTable *thunk_info;
2508 if (!major_gc) return;
2510 thunk_info = itbl_to_thunk_itbl(info);
2511 scavenge_srt((StgClosure **)GET_SRT(thunk_info), thunk_info->i.srt_bitmap);
2515 scavenge_fun_srt(const StgInfoTable *info)
2517 StgFunInfoTable *fun_info;
2519 if (!major_gc) return;
2521 fun_info = itbl_to_fun_itbl(info);
2522 scavenge_srt((StgClosure **)GET_FUN_SRT(fun_info), fun_info->i.srt_bitmap);
2525 /* -----------------------------------------------------------------------------
2527 -------------------------------------------------------------------------- */
2530 scavengeTSO (StgTSO *tso)
2532 if ( tso->why_blocked == BlockedOnMVar
2533 || tso->why_blocked == BlockedOnBlackHole
2534 || tso->why_blocked == BlockedOnException
2536 || tso->why_blocked == BlockedOnGA
2537 || tso->why_blocked == BlockedOnGA_NoSend
2540 tso->block_info.closure = evacuate(tso->block_info.closure);
2542 if ( tso->blocked_exceptions != NULL ) {
2543 tso->blocked_exceptions =
2544 (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
2547 // We don't always chase the link field: TSOs on the blackhole
2548 // queue are not automatically alive, so the link field is a
2549 // "weak" pointer in that case.
2550 if (tso->why_blocked != BlockedOnBlackHole) {
2551 tso->link = (StgTSO *)evacuate((StgClosure *)tso->link);
2554 // scavange current transaction record
2555 tso->trec = (StgTRecHeader *)evacuate((StgClosure *)tso->trec);
2557 // scavenge this thread's stack
2558 scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
2561 /* -----------------------------------------------------------------------------
2562 Blocks of function args occur on the stack (at the top) and
2564 -------------------------------------------------------------------------- */
2566 STATIC_INLINE StgPtr
2567 scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
2574 switch (fun_info->f.fun_type) {
2576 bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
2577 size = BITMAP_SIZE(fun_info->f.b.bitmap);
2580 size = GET_FUN_LARGE_BITMAP(fun_info)->size;
2581 scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
2585 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2586 size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->f.fun_type]);
2589 if ((bitmap & 1) == 0) {
2590 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2593 bitmap = bitmap >> 1;
2601 STATIC_INLINE StgPtr
2602 scavenge_PAP_payload (StgClosure *fun, StgClosure **payload, StgWord size)
2606 StgFunInfoTable *fun_info;
2608 fun_info = get_fun_itbl(fun);
2609 ASSERT(fun_info->i.type != PAP);
2610 p = (StgPtr)payload;
2612 switch (fun_info->f.fun_type) {
2614 bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
2617 scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
2621 scavenge_large_bitmap((StgPtr)payload, BCO_BITMAP(fun), size);
2625 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2628 if ((bitmap & 1) == 0) {
2629 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2632 bitmap = bitmap >> 1;
2640 STATIC_INLINE StgPtr
2641 scavenge_PAP (StgPAP *pap)
2643 pap->fun = evacuate(pap->fun);
2644 return scavenge_PAP_payload (pap->fun, pap->payload, pap->n_args);
2647 STATIC_INLINE StgPtr
2648 scavenge_AP (StgAP *ap)
2650 ap->fun = evacuate(ap->fun);
2651 return scavenge_PAP_payload (ap->fun, ap->payload, ap->n_args);
2654 /* -----------------------------------------------------------------------------
2655 Scavenge a given step until there are no more objects in this step
2658 evac_gen is set by the caller to be either zero (for a step in a
2659 generation < N) or G where G is the generation of the step being
2662 We sometimes temporarily change evac_gen back to zero if we're
2663 scavenging a mutable object where early promotion isn't such a good
2665 -------------------------------------------------------------------------- */
2673 nat saved_evac_gen = evac_gen;
2678 failed_to_evac = rtsFalse;
2680 /* scavenge phase - standard breadth-first scavenging of the
2684 while (bd != stp->hp_bd || p < stp->hp) {
2686 // If we're at the end of this block, move on to the next block
2687 if (bd != stp->hp_bd && p == bd->free) {
2693 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2694 info = get_itbl((StgClosure *)p);
2696 ASSERT(thunk_selector_depth == 0);
2699 switch (info->type) {
2703 StgMVar *mvar = ((StgMVar *)p);
2705 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
2706 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
2707 mvar->value = evacuate((StgClosure *)mvar->value);
2708 evac_gen = saved_evac_gen;
2709 failed_to_evac = rtsTrue; // mutable.
2710 p += sizeofW(StgMVar);
2715 scavenge_fun_srt(info);
2716 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2717 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2718 p += sizeofW(StgHeader) + 2;
2722 scavenge_thunk_srt(info);
2723 ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
2724 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2725 p += sizeofW(StgThunk) + 2;
2729 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2730 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2731 p += sizeofW(StgHeader) + 2;
2735 scavenge_thunk_srt(info);
2736 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2737 p += sizeofW(StgThunk) + 1;
2741 scavenge_fun_srt(info);
2743 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2744 p += sizeofW(StgHeader) + 1;
2748 scavenge_thunk_srt(info);
2749 p += sizeofW(StgThunk) + 1;
2753 scavenge_fun_srt(info);
2755 p += sizeofW(StgHeader) + 1;
2759 scavenge_thunk_srt(info);
2760 p += sizeofW(StgThunk) + 2;
2764 scavenge_fun_srt(info);
2766 p += sizeofW(StgHeader) + 2;
2770 scavenge_thunk_srt(info);
2771 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2772 p += sizeofW(StgThunk) + 2;
2776 scavenge_fun_srt(info);
2778 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2779 p += sizeofW(StgHeader) + 2;
2783 scavenge_fun_srt(info);
2790 scavenge_thunk_srt(info);
2791 end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
2792 for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
2793 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2795 p += info->layout.payload.nptrs;
2806 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2807 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2808 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2810 p += info->layout.payload.nptrs;
2815 StgBCO *bco = (StgBCO *)p;
2816 bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
2817 bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
2818 bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
2819 bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
2820 p += bco_sizeW(bco);
2825 if (stp->gen->no != 0) {
2828 // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an
2829 // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
2830 LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
2833 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
2835 SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
2837 // We pretend that p has just been created.
2838 LDV_RECORD_CREATE((StgClosure *)p);
2841 case IND_OLDGEN_PERM:
2842 ((StgInd *)p)->indirectee = evacuate(((StgInd *)p)->indirectee);
2843 p += sizeofW(StgInd);
2848 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2849 evac_gen = saved_evac_gen;
2850 failed_to_evac = rtsTrue; // mutable anyhow
2851 p += sizeofW(StgMutVar);
2855 case SE_CAF_BLACKHOLE:
2858 p += BLACKHOLE_sizeW();
2861 case THUNK_SELECTOR:
2863 StgSelector *s = (StgSelector *)p;
2864 s->selectee = evacuate(s->selectee);
2865 p += THUNK_SELECTOR_sizeW();
2869 // A chunk of stack saved in a heap object
2872 StgAP_STACK *ap = (StgAP_STACK *)p;
2874 ap->fun = evacuate(ap->fun);
2875 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2876 p = (StgPtr)ap->payload + ap->size;
2881 p = scavenge_PAP((StgPAP *)p);
2885 p = scavenge_AP((StgAP *)p);
2889 // nothing to follow
2890 p += arr_words_sizeW((StgArrWords *)p);
2894 // follow everything
2898 evac_gen = 0; // repeatedly mutable
2899 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2900 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2901 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2903 evac_gen = saved_evac_gen;
2904 failed_to_evac = rtsTrue; // mutable anyhow.
2908 case MUT_ARR_PTRS_FROZEN:
2909 case MUT_ARR_PTRS_FROZEN0:
2910 // follow everything
2914 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2915 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2916 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2918 // it's tempting to recordMutable() if failed_to_evac is
2919 // false, but that breaks some assumptions (eg. every
2920 // closure on the mutable list is supposed to have the MUT
2921 // flag set, and MUT_ARR_PTRS_FROZEN doesn't).
2927 StgTSO *tso = (StgTSO *)p;
2930 evac_gen = saved_evac_gen;
2931 failed_to_evac = rtsTrue; // mutable anyhow.
2932 p += tso_sizeW(tso);
2940 nat size, ptrs, nonptrs, vhs;
2942 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2944 StgRBH *rbh = (StgRBH *)p;
2945 (StgClosure *)rbh->blocking_queue =
2946 evacuate((StgClosure *)rbh->blocking_queue);
2947 failed_to_evac = rtsTrue; // mutable anyhow.
2949 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2950 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2951 // ToDo: use size of reverted closure here!
2952 p += BLACKHOLE_sizeW();
2958 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2959 // follow the pointer to the node which is being demanded
2960 (StgClosure *)bf->node =
2961 evacuate((StgClosure *)bf->node);
2962 // follow the link to the rest of the blocking queue
2963 (StgClosure *)bf->link =
2964 evacuate((StgClosure *)bf->link);
2966 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
2967 bf, info_type((StgClosure *)bf),
2968 bf->node, info_type(bf->node)));
2969 p += sizeofW(StgBlockedFetch);
2977 p += sizeofW(StgFetchMe);
2978 break; // nothing to do in this case
2982 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
2983 (StgClosure *)fmbq->blocking_queue =
2984 evacuate((StgClosure *)fmbq->blocking_queue);
2986 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
2987 p, info_type((StgClosure *)p)));
2988 p += sizeofW(StgFetchMeBlockingQueue);
2993 case TVAR_WAIT_QUEUE:
2995 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
2997 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
2998 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
2999 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3000 evac_gen = saved_evac_gen;
3001 failed_to_evac = rtsTrue; // mutable
3002 p += sizeofW(StgTVarWaitQueue);
3008 StgTVar *tvar = ((StgTVar *) p);
3010 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3011 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3013 tvar->last_update_by = (StgTRecHeader *)evacuate((StgClosure*)tvar->last_update_by);
3015 evac_gen = saved_evac_gen;
3016 failed_to_evac = rtsTrue; // mutable
3017 p += sizeofW(StgTVar);
3023 StgTRecHeader *trec = ((StgTRecHeader *) p);
3025 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3026 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3027 evac_gen = saved_evac_gen;
3028 failed_to_evac = rtsTrue; // mutable
3029 p += sizeofW(StgTRecHeader);
3036 StgTRecChunk *tc = ((StgTRecChunk *) p);
3037 TRecEntry *e = &(tc -> entries[0]);
3039 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3040 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3041 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3042 e->expected_value = evacuate((StgClosure*)e->expected_value);
3043 e->new_value = evacuate((StgClosure*)e->new_value);
3045 evac_gen = saved_evac_gen;
3046 failed_to_evac = rtsTrue; // mutable
3047 p += sizeofW(StgTRecChunk);
3052 barf("scavenge: unimplemented/strange closure type %d @ %p",
3057 * We need to record the current object on the mutable list if
3058 * (a) It is actually mutable, or
3059 * (b) It contains pointers to a younger generation.
3060 * Case (b) arises if we didn't manage to promote everything that
3061 * the current object points to into the current generation.
3063 if (failed_to_evac) {
3064 failed_to_evac = rtsFalse;
3065 recordMutableGen((StgClosure *)q, stp->gen);
3073 /* -----------------------------------------------------------------------------
3074 Scavenge everything on the mark stack.
3076 This is slightly different from scavenge():
3077 - we don't walk linearly through the objects, so the scavenger
3078 doesn't need to advance the pointer on to the next object.
3079 -------------------------------------------------------------------------- */
3082 scavenge_mark_stack(void)
3088 evac_gen = oldest_gen->no;
3089 saved_evac_gen = evac_gen;
3092 while (!mark_stack_empty()) {
3093 p = pop_mark_stack();
3095 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3096 info = get_itbl((StgClosure *)p);
3099 switch (info->type) {
3103 StgMVar *mvar = ((StgMVar *)p);
3105 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
3106 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
3107 mvar->value = evacuate((StgClosure *)mvar->value);
3108 evac_gen = saved_evac_gen;
3109 failed_to_evac = rtsTrue; // mutable.
3114 scavenge_fun_srt(info);
3115 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
3116 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3120 scavenge_thunk_srt(info);
3121 ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
3122 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
3126 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
3127 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3132 scavenge_fun_srt(info);
3133 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3138 scavenge_thunk_srt(info);
3139 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
3144 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3149 scavenge_fun_srt(info);
3154 scavenge_thunk_srt(info);
3162 scavenge_fun_srt(info);
3169 scavenge_thunk_srt(info);
3170 end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
3171 for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
3172 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3184 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3185 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
3186 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3192 StgBCO *bco = (StgBCO *)p;
3193 bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
3194 bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
3195 bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
3196 bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
3201 // don't need to do anything here: the only possible case
3202 // is that we're in a 1-space compacting collector, with
3203 // no "old" generation.
3207 case IND_OLDGEN_PERM:
3208 ((StgInd *)p)->indirectee =
3209 evacuate(((StgInd *)p)->indirectee);
3214 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3215 evac_gen = saved_evac_gen;
3216 failed_to_evac = rtsTrue;
3220 case SE_CAF_BLACKHOLE:
3226 case THUNK_SELECTOR:
3228 StgSelector *s = (StgSelector *)p;
3229 s->selectee = evacuate(s->selectee);
3233 // A chunk of stack saved in a heap object
3236 StgAP_STACK *ap = (StgAP_STACK *)p;
3238 ap->fun = evacuate(ap->fun);
3239 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3244 scavenge_PAP((StgPAP *)p);
3248 scavenge_AP((StgAP *)p);
3252 // follow everything
3256 evac_gen = 0; // repeatedly mutable
3257 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3258 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3259 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3261 evac_gen = saved_evac_gen;
3262 failed_to_evac = rtsTrue; // mutable anyhow.
3266 case MUT_ARR_PTRS_FROZEN:
3267 case MUT_ARR_PTRS_FROZEN0:
3268 // follow everything
3272 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3273 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3274 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3281 StgTSO *tso = (StgTSO *)p;
3284 evac_gen = saved_evac_gen;
3285 failed_to_evac = rtsTrue;
3293 nat size, ptrs, nonptrs, vhs;
3295 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3297 StgRBH *rbh = (StgRBH *)p;
3298 bh->blocking_queue =
3299 (StgTSO *)evacuate((StgClosure *)bh->blocking_queue);
3300 failed_to_evac = rtsTrue; // mutable anyhow.
3302 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3303 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3309 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3310 // follow the pointer to the node which is being demanded
3311 (StgClosure *)bf->node =
3312 evacuate((StgClosure *)bf->node);
3313 // follow the link to the rest of the blocking queue
3314 (StgClosure *)bf->link =
3315 evacuate((StgClosure *)bf->link);
3317 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3318 bf, info_type((StgClosure *)bf),
3319 bf->node, info_type(bf->node)));
3327 break; // nothing to do in this case
3331 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3332 (StgClosure *)fmbq->blocking_queue =
3333 evacuate((StgClosure *)fmbq->blocking_queue);
3335 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3336 p, info_type((StgClosure *)p)));
3341 case TVAR_WAIT_QUEUE:
3343 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3345 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3346 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3347 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3348 evac_gen = saved_evac_gen;
3349 failed_to_evac = rtsTrue; // mutable
3355 StgTVar *tvar = ((StgTVar *) p);
3357 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3358 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3360 tvar->last_update_by = (StgTRecHeader *)evacuate((StgClosure*)tvar->last_update_by);
3362 evac_gen = saved_evac_gen;
3363 failed_to_evac = rtsTrue; // mutable
3370 StgTRecChunk *tc = ((StgTRecChunk *) p);
3371 TRecEntry *e = &(tc -> entries[0]);
3373 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3374 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3375 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3376 e->expected_value = evacuate((StgClosure*)e->expected_value);
3377 e->new_value = evacuate((StgClosure*)e->new_value);
3379 evac_gen = saved_evac_gen;
3380 failed_to_evac = rtsTrue; // mutable
3386 StgTRecHeader *trec = ((StgTRecHeader *) p);
3388 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3389 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3390 evac_gen = saved_evac_gen;
3391 failed_to_evac = rtsTrue; // mutable
3396 barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p",
3400 if (failed_to_evac) {
3401 failed_to_evac = rtsFalse;
3402 recordMutableGen((StgClosure *)q, &generations[evac_gen]);
3405 // mark the next bit to indicate "scavenged"
3406 mark(q+1, Bdescr(q));
3408 } // while (!mark_stack_empty())
3410 // start a new linear scan if the mark stack overflowed at some point
3411 if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
3412 IF_DEBUG(gc, debugBelch("scavenge_mark_stack: starting linear scan"));
3413 mark_stack_overflowed = rtsFalse;
3414 oldgen_scan_bd = oldest_gen->steps[0].blocks;
3415 oldgen_scan = oldgen_scan_bd->start;
3418 if (oldgen_scan_bd) {
3419 // push a new thing on the mark stack
3421 // find a closure that is marked but not scavenged, and start
3423 while (oldgen_scan < oldgen_scan_bd->free
3424 && !is_marked(oldgen_scan,oldgen_scan_bd)) {
3428 if (oldgen_scan < oldgen_scan_bd->free) {
3430 // already scavenged?
3431 if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
3432 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3435 push_mark_stack(oldgen_scan);
3436 // ToDo: bump the linear scan by the actual size of the object
3437 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3441 oldgen_scan_bd = oldgen_scan_bd->link;
3442 if (oldgen_scan_bd != NULL) {
3443 oldgen_scan = oldgen_scan_bd->start;
3449 /* -----------------------------------------------------------------------------
3450 Scavenge one object.
3452 This is used for objects that are temporarily marked as mutable
3453 because they contain old-to-new generation pointers. Only certain
3454 objects can have this property.
3455 -------------------------------------------------------------------------- */
3458 scavenge_one(StgPtr p)
3460 const StgInfoTable *info;
3461 nat saved_evac_gen = evac_gen;
3464 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3465 info = get_itbl((StgClosure *)p);
3467 switch (info->type) {
3471 StgMVar *mvar = ((StgMVar *)p);
3473 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
3474 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
3475 mvar->value = evacuate((StgClosure *)mvar->value);
3476 evac_gen = saved_evac_gen;
3477 failed_to_evac = rtsTrue; // mutable.
3490 end = (StgPtr)((StgThunk *)p)->payload + info->layout.payload.ptrs;
3491 for (q = (StgPtr)((StgThunk *)p)->payload; q < end; q++) {
3492 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3498 case FUN_1_0: // hardly worth specialising these guys
3514 end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3515 for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
3516 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3523 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3524 evac_gen = saved_evac_gen;
3525 failed_to_evac = rtsTrue; // mutable anyhow
3529 case SE_CAF_BLACKHOLE:
3534 case THUNK_SELECTOR:
3536 StgSelector *s = (StgSelector *)p;
3537 s->selectee = evacuate(s->selectee);
3543 StgAP_STACK *ap = (StgAP_STACK *)p;
3545 ap->fun = evacuate(ap->fun);
3546 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3547 p = (StgPtr)ap->payload + ap->size;
3552 p = scavenge_PAP((StgPAP *)p);
3556 p = scavenge_AP((StgAP *)p);
3560 // nothing to follow
3565 // follow everything
3568 evac_gen = 0; // repeatedly mutable
3569 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3570 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3571 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3573 evac_gen = saved_evac_gen;
3574 failed_to_evac = rtsTrue;
3578 case MUT_ARR_PTRS_FROZEN:
3579 case MUT_ARR_PTRS_FROZEN0:
3581 // follow everything
3584 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3585 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3586 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3593 StgTSO *tso = (StgTSO *)p;
3595 evac_gen = 0; // repeatedly mutable
3597 evac_gen = saved_evac_gen;
3598 failed_to_evac = rtsTrue;
3606 nat size, ptrs, nonptrs, vhs;
3608 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3610 StgRBH *rbh = (StgRBH *)p;
3611 (StgClosure *)rbh->blocking_queue =
3612 evacuate((StgClosure *)rbh->blocking_queue);
3613 failed_to_evac = rtsTrue; // mutable anyhow.
3615 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3616 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3617 // ToDo: use size of reverted closure here!
3623 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3624 // follow the pointer to the node which is being demanded
3625 (StgClosure *)bf->node =
3626 evacuate((StgClosure *)bf->node);
3627 // follow the link to the rest of the blocking queue
3628 (StgClosure *)bf->link =
3629 evacuate((StgClosure *)bf->link);
3631 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3632 bf, info_type((StgClosure *)bf),
3633 bf->node, info_type(bf->node)));
3641 break; // nothing to do in this case
3645 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3646 (StgClosure *)fmbq->blocking_queue =
3647 evacuate((StgClosure *)fmbq->blocking_queue);
3649 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3650 p, info_type((StgClosure *)p)));
3655 case TVAR_WAIT_QUEUE:
3657 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3659 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3660 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3661 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3662 evac_gen = saved_evac_gen;
3663 failed_to_evac = rtsTrue; // mutable
3669 StgTVar *tvar = ((StgTVar *) p);
3671 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3672 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3674 tvar->last_update_by = (StgTRecHeader *)evacuate((StgClosure*)tvar->last_update_by);
3676 evac_gen = saved_evac_gen;
3677 failed_to_evac = rtsTrue; // mutable
3683 StgTRecHeader *trec = ((StgTRecHeader *) p);
3685 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3686 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3687 evac_gen = saved_evac_gen;
3688 failed_to_evac = rtsTrue; // mutable
3695 StgTRecChunk *tc = ((StgTRecChunk *) p);
3696 TRecEntry *e = &(tc -> entries[0]);
3698 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3699 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3700 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3701 e->expected_value = evacuate((StgClosure*)e->expected_value);
3702 e->new_value = evacuate((StgClosure*)e->new_value);
3704 evac_gen = saved_evac_gen;
3705 failed_to_evac = rtsTrue; // mutable
3710 case IND_OLDGEN_PERM:
3713 /* Careful here: a THUNK can be on the mutable list because
3714 * it contains pointers to young gen objects. If such a thunk
3715 * is updated, the IND_OLDGEN will be added to the mutable
3716 * list again, and we'll scavenge it twice. evacuate()
3717 * doesn't check whether the object has already been
3718 * evacuated, so we perform that check here.
3720 StgClosure *q = ((StgInd *)p)->indirectee;
3721 if (HEAP_ALLOCED(q) && Bdescr((StgPtr)q)->flags & BF_EVACUATED) {
3724 ((StgInd *)p)->indirectee = evacuate(q);
3727 #if 0 && defined(DEBUG)
3728 if (RtsFlags.DebugFlags.gc)
3729 /* Debugging code to print out the size of the thing we just
3733 StgPtr start = gen->steps[0].scan;
3734 bdescr *start_bd = gen->steps[0].scan_bd;
3736 scavenge(&gen->steps[0]);
3737 if (start_bd != gen->steps[0].scan_bd) {
3738 size += (P_)BLOCK_ROUND_UP(start) - start;
3739 start_bd = start_bd->link;
3740 while (start_bd != gen->steps[0].scan_bd) {
3741 size += BLOCK_SIZE_W;
3742 start_bd = start_bd->link;
3744 size += gen->steps[0].scan -
3745 (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
3747 size = gen->steps[0].scan - start;
3749 debugBelch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
3755 barf("scavenge_one: strange object %d", (int)(info->type));
3758 no_luck = failed_to_evac;
3759 failed_to_evac = rtsFalse;
3763 /* -----------------------------------------------------------------------------
3764 Scavenging mutable lists.
3766 We treat the mutable list of each generation > N (i.e. all the
3767 generations older than the one being collected) as roots. We also
3768 remove non-mutable objects from the mutable list at this point.
3769 -------------------------------------------------------------------------- */
3772 scavenge_mutable_list(generation *gen)
3777 bd = gen->saved_mut_list;
3780 for (; bd != NULL; bd = bd->link) {
3781 for (q = bd->start; q < bd->free; q++) {
3783 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3784 if (scavenge_one(p)) {
3785 /* didn't manage to promote everything, so put the
3786 * object back on the list.
3788 recordMutableGen((StgClosure *)p,gen);
3793 // free the old mut_list
3794 freeChain(gen->saved_mut_list);
3795 gen->saved_mut_list = NULL;
3800 scavenge_static(void)
3802 StgClosure* p = static_objects;
3803 const StgInfoTable *info;
3805 /* Always evacuate straight to the oldest generation for static
3807 evac_gen = oldest_gen->no;
3809 /* keep going until we've scavenged all the objects on the linked
3811 while (p != END_OF_STATIC_LIST) {
3813 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3816 if (info->type==RBH)
3817 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3819 // make sure the info pointer is into text space
3821 /* Take this object *off* the static_objects list,
3822 * and put it on the scavenged_static_objects list.
3824 static_objects = *STATIC_LINK(info,p);
3825 *STATIC_LINK(info,p) = scavenged_static_objects;
3826 scavenged_static_objects = p;
3828 switch (info -> type) {
3832 StgInd *ind = (StgInd *)p;
3833 ind->indirectee = evacuate(ind->indirectee);
3835 /* might fail to evacuate it, in which case we have to pop it
3836 * back on the mutable list of the oldest generation. We
3837 * leave it *on* the scavenged_static_objects list, though,
3838 * in case we visit this object again.
3840 if (failed_to_evac) {
3841 failed_to_evac = rtsFalse;
3842 recordMutableGen((StgClosure *)p,oldest_gen);
3848 scavenge_thunk_srt(info);
3852 scavenge_fun_srt(info);
3859 next = (P_)p->payload + info->layout.payload.ptrs;
3860 // evacuate the pointers
3861 for (q = (P_)p->payload; q < next; q++) {
3862 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3868 barf("scavenge_static: strange closure %d", (int)(info->type));
3871 ASSERT(failed_to_evac == rtsFalse);
3873 /* get the next static object from the list. Remember, there might
3874 * be more stuff on this list now that we've done some evacuating!
3875 * (static_objects is a global)
3881 /* -----------------------------------------------------------------------------
3882 scavenge a chunk of memory described by a bitmap
3883 -------------------------------------------------------------------------- */
3886 scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
3892 bitmap = large_bitmap->bitmap[b];
3893 for (i = 0; i < size; ) {
3894 if ((bitmap & 1) == 0) {
3895 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3899 if (i % BITS_IN(W_) == 0) {
3901 bitmap = large_bitmap->bitmap[b];
3903 bitmap = bitmap >> 1;
3908 STATIC_INLINE StgPtr
3909 scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap)
3912 if ((bitmap & 1) == 0) {
3913 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3916 bitmap = bitmap >> 1;
3922 /* -----------------------------------------------------------------------------
3923 scavenge_stack walks over a section of stack and evacuates all the
3924 objects pointed to by it. We can use the same code for walking
3925 AP_STACK_UPDs, since these are just sections of copied stack.
3926 -------------------------------------------------------------------------- */
3930 scavenge_stack(StgPtr p, StgPtr stack_end)
3932 const StgRetInfoTable* info;
3936 //IF_DEBUG(sanity, debugBelch(" scavenging stack between %p and %p", p, stack_end));
3939 * Each time around this loop, we are looking at a chunk of stack
3940 * that starts with an activation record.
3943 while (p < stack_end) {
3944 info = get_ret_itbl((StgClosure *)p);
3946 switch (info->i.type) {
3949 ((StgUpdateFrame *)p)->updatee
3950 = evacuate(((StgUpdateFrame *)p)->updatee);
3951 p += sizeofW(StgUpdateFrame);
3954 // small bitmap (< 32 entries, or 64 on a 64-bit machine)
3955 case CATCH_STM_FRAME:
3956 case CATCH_RETRY_FRAME:
3957 case ATOMICALLY_FRAME:
3962 bitmap = BITMAP_BITS(info->i.layout.bitmap);
3963 size = BITMAP_SIZE(info->i.layout.bitmap);
3964 // NOTE: the payload starts immediately after the info-ptr, we
3965 // don't have an StgHeader in the same sense as a heap closure.
3967 p = scavenge_small_bitmap(p, size, bitmap);
3971 scavenge_srt((StgClosure **)GET_SRT(info), info->i.srt_bitmap);
3979 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3982 size = BCO_BITMAP_SIZE(bco);
3983 scavenge_large_bitmap(p, BCO_BITMAP(bco), size);
3988 // large bitmap (> 32 entries, or > 64 on a 64-bit machine)
3994 size = GET_LARGE_BITMAP(&info->i)->size;
3996 scavenge_large_bitmap(p, GET_LARGE_BITMAP(&info->i), size);
3998 // and don't forget to follow the SRT
4002 // Dynamic bitmap: the mask is stored on the stack, and
4003 // there are a number of non-pointers followed by a number
4004 // of pointers above the bitmapped area. (see StgMacros.h,
4009 dyn = ((StgRetDyn *)p)->liveness;
4011 // traverse the bitmap first
4012 bitmap = RET_DYN_LIVENESS(dyn);
4013 p = (P_)&((StgRetDyn *)p)->payload[0];
4014 size = RET_DYN_BITMAP_SIZE;
4015 p = scavenge_small_bitmap(p, size, bitmap);
4017 // skip over the non-ptr words
4018 p += RET_DYN_NONPTRS(dyn) + RET_DYN_NONPTR_REGS_SIZE;
4020 // follow the ptr words
4021 for (size = RET_DYN_PTRS(dyn); size > 0; size--) {
4022 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
4030 StgRetFun *ret_fun = (StgRetFun *)p;
4031 StgFunInfoTable *fun_info;
4033 ret_fun->fun = evacuate(ret_fun->fun);
4034 fun_info = get_fun_itbl(ret_fun->fun);
4035 p = scavenge_arg_block(fun_info, ret_fun->payload);
4040 barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->i.type));
4045 /*-----------------------------------------------------------------------------
4046 scavenge the large object list.
4048 evac_gen set by caller; similar games played with evac_gen as with
4049 scavenge() - see comment at the top of scavenge(). Most large
4050 objects are (repeatedly) mutable, so most of the time evac_gen will
4052 --------------------------------------------------------------------------- */
4055 scavenge_large(step *stp)
4060 bd = stp->new_large_objects;
4062 for (; bd != NULL; bd = stp->new_large_objects) {
4064 /* take this object *off* the large objects list and put it on
4065 * the scavenged large objects list. This is so that we can
4066 * treat new_large_objects as a stack and push new objects on
4067 * the front when evacuating.
4069 stp->new_large_objects = bd->link;
4070 dbl_link_onto(bd, &stp->scavenged_large_objects);
4072 // update the block count in this step.
4073 stp->n_scavenged_large_blocks += bd->blocks;
4076 if (scavenge_one(p)) {
4077 recordMutableGen((StgClosure *)p, stp->gen);
4082 /* -----------------------------------------------------------------------------
4083 Initialising the static object & mutable lists
4084 -------------------------------------------------------------------------- */
4087 zero_static_object_list(StgClosure* first_static)
4091 const StgInfoTable *info;
4093 for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
4095 link = *STATIC_LINK(info, p);
4096 *STATIC_LINK(info,p) = NULL;
4100 /* -----------------------------------------------------------------------------
4102 -------------------------------------------------------------------------- */
4109 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
4110 c = (StgIndStatic *)c->static_link)
4112 SET_INFO(c, c->saved_info);
4113 c->saved_info = NULL;
4114 // could, but not necessary: c->static_link = NULL;
4116 revertible_caf_list = NULL;
4120 markCAFs( evac_fn evac )
4124 for (c = (StgIndStatic *)caf_list; c != NULL;
4125 c = (StgIndStatic *)c->static_link)
4127 evac(&c->indirectee);
4129 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
4130 c = (StgIndStatic *)c->static_link)
4132 evac(&c->indirectee);
4136 /* -----------------------------------------------------------------------------
4137 Sanity code for CAF garbage collection.
4139 With DEBUG turned on, we manage a CAF list in addition to the SRT
4140 mechanism. After GC, we run down the CAF list and blackhole any
4141 CAFs which have been garbage collected. This means we get an error
4142 whenever the program tries to enter a garbage collected CAF.
4144 Any garbage collected CAFs are taken off the CAF list at the same
4146 -------------------------------------------------------------------------- */
4148 #if 0 && defined(DEBUG)
4155 const StgInfoTable *info;
4166 ASSERT(info->type == IND_STATIC);
4168 if (STATIC_LINK(info,p) == NULL) {
4169 IF_DEBUG(gccafs, debugBelch("CAF gc'd at 0x%04lx", (long)p));
4171 SET_INFO(p,&stg_BLACKHOLE_info);
4172 p = STATIC_LINK2(info,p);
4176 pp = &STATIC_LINK2(info,p);
4183 // debugBelch("%d CAFs live", i);
4188 /* -----------------------------------------------------------------------------
4191 Whenever a thread returns to the scheduler after possibly doing
4192 some work, we have to run down the stack and black-hole all the
4193 closures referred to by update frames.
4194 -------------------------------------------------------------------------- */
4197 threadLazyBlackHole(StgTSO *tso)
4200 StgRetInfoTable *info;
4204 stack_end = &tso->stack[tso->stack_size];
4206 frame = (StgClosure *)tso->sp;
4209 info = get_ret_itbl(frame);
4211 switch (info->i.type) {
4214 bh = ((StgUpdateFrame *)frame)->updatee;
4216 /* if the thunk is already blackholed, it means we've also
4217 * already blackholed the rest of the thunks on this stack,
4218 * so we can stop early.
4220 * The blackhole made for a CAF is a CAF_BLACKHOLE, so they
4221 * don't interfere with this optimisation.
4223 if (bh->header.info == &stg_BLACKHOLE_info) {
4227 if (bh->header.info != &stg_CAF_BLACKHOLE_info) {
4228 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4229 debugBelch("Unexpected lazy BHing required at 0x%04x\n",(int)bh);
4233 // We pretend that bh is now dead.
4234 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4236 SET_INFO(bh,&stg_BLACKHOLE_info);
4238 // We pretend that bh has just been created.
4239 LDV_RECORD_CREATE(bh);
4242 frame = (StgClosure *) ((StgUpdateFrame *)frame + 1);
4248 // normal stack frames; do nothing except advance the pointer
4250 frame = (StgClosure *)((StgPtr)frame + stack_frame_sizeW(frame));
4256 /* -----------------------------------------------------------------------------
4259 * Code largely pinched from old RTS, then hacked to bits. We also do
4260 * lazy black holing here.
4262 * -------------------------------------------------------------------------- */
4264 struct stack_gap { StgWord gap_size; struct stack_gap *next_gap; };
4267 threadSqueezeStack(StgTSO *tso)
4270 rtsBool prev_was_update_frame;
4271 StgClosure *updatee = NULL;
4273 StgRetInfoTable *info;
4274 StgWord current_gap_size;
4275 struct stack_gap *gap;
4278 // Traverse the stack upwards, replacing adjacent update frames
4279 // with a single update frame and a "stack gap". A stack gap
4280 // contains two values: the size of the gap, and the distance
4281 // to the next gap (or the stack top).
4283 bottom = &(tso->stack[tso->stack_size]);
4287 ASSERT(frame < bottom);
4289 prev_was_update_frame = rtsFalse;
4290 current_gap_size = 0;
4291 gap = (struct stack_gap *) (tso->sp - sizeofW(StgUpdateFrame));
4293 while (frame < bottom) {
4295 info = get_ret_itbl((StgClosure *)frame);
4296 switch (info->i.type) {
4300 StgUpdateFrame *upd = (StgUpdateFrame *)frame;
4302 if (upd->updatee->header.info == &stg_BLACKHOLE_info) {
4304 // found a BLACKHOLE'd update frame; we've been here
4305 // before, in a previous GC, so just break out.
4307 // Mark the end of the gap, if we're in one.
4308 if (current_gap_size != 0) {
4309 gap = (struct stack_gap *)(frame-sizeofW(StgUpdateFrame));
4312 frame += sizeofW(StgUpdateFrame);
4313 goto done_traversing;
4316 if (prev_was_update_frame) {
4318 TICK_UPD_SQUEEZED();
4319 /* wasn't there something about update squeezing and ticky to be
4320 * sorted out? oh yes: we aren't counting each enter properly
4321 * in this case. See the log somewhere. KSW 1999-04-21
4323 * Check two things: that the two update frames don't point to
4324 * the same object, and that the updatee_bypass isn't already an
4325 * indirection. Both of these cases only happen when we're in a
4326 * block hole-style loop (and there are multiple update frames
4327 * on the stack pointing to the same closure), but they can both
4328 * screw us up if we don't check.
4330 if (upd->updatee != updatee && !closure_IND(upd->updatee)) {
4331 UPD_IND_NOLOCK(upd->updatee, updatee);
4334 // now mark this update frame as a stack gap. The gap
4335 // marker resides in the bottom-most update frame of
4336 // the series of adjacent frames, and covers all the
4337 // frames in this series.
4338 current_gap_size += sizeofW(StgUpdateFrame);
4339 ((struct stack_gap *)frame)->gap_size = current_gap_size;
4340 ((struct stack_gap *)frame)->next_gap = gap;
4342 frame += sizeofW(StgUpdateFrame);
4346 // single update frame, or the topmost update frame in a series
4348 StgClosure *bh = upd->updatee;
4350 // Do lazy black-holing
4351 if (bh->header.info != &stg_BLACKHOLE_info &&
4352 bh->header.info != &stg_CAF_BLACKHOLE_info) {
4353 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4354 debugBelch("Unexpected lazy BHing required at 0x%04x",(int)bh);
4357 // zero out the slop so that the sanity checker can tell
4358 // where the next closure is.
4359 DEBUG_FILL_SLOP(bh);
4362 // We pretend that bh is now dead.
4363 // ToDo: is the slop filling the same as DEBUG_FILL_SLOP?
4364 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4366 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
4367 SET_INFO(bh,&stg_BLACKHOLE_info);
4369 // We pretend that bh has just been created.
4370 LDV_RECORD_CREATE(bh);
4373 prev_was_update_frame = rtsTrue;
4374 updatee = upd->updatee;
4375 frame += sizeofW(StgUpdateFrame);
4381 prev_was_update_frame = rtsFalse;
4383 // we're not in a gap... check whether this is the end of a gap
4384 // (an update frame can't be the end of a gap).
4385 if (current_gap_size != 0) {
4386 gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
4388 current_gap_size = 0;
4390 frame += stack_frame_sizeW((StgClosure *)frame);
4397 // Now we have a stack with gaps in it, and we have to walk down
4398 // shoving the stack up to fill in the gaps. A diagram might
4402 // | ********* | <- sp
4406 // | stack_gap | <- gap | chunk_size
4408 // | ......... | <- gap_end v
4414 // 'sp' points the the current top-of-stack
4415 // 'gap' points to the stack_gap structure inside the gap
4416 // ***** indicates real stack data
4417 // ..... indicates gap
4418 // <empty> indicates unused
4422 void *gap_start, *next_gap_start, *gap_end;
4425 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4426 sp = next_gap_start;
4428 while ((StgPtr)gap > tso->sp) {
4430 // we're working in *bytes* now...
4431 gap_start = next_gap_start;
4432 gap_end = (void*) ((unsigned char*)gap_start - gap->gap_size * sizeof(W_));
4434 gap = gap->next_gap;
4435 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4437 chunk_size = (unsigned char*)gap_end - (unsigned char*)next_gap_start;
4439 memmove(sp, next_gap_start, chunk_size);
4442 tso->sp = (StgPtr)sp;
4446 /* -----------------------------------------------------------------------------
4449 * We have to prepare for GC - this means doing lazy black holing
4450 * here. We also take the opportunity to do stack squeezing if it's
4452 * -------------------------------------------------------------------------- */
4454 threadPaused(StgTSO *tso)
4456 if ( RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue )
4457 threadSqueezeStack(tso); // does black holing too
4459 threadLazyBlackHole(tso);
4462 /* -----------------------------------------------------------------------------
4464 * -------------------------------------------------------------------------- */
4468 printMutableList(generation *gen)
4473 debugBelch("@@ Mutable list %p: ", gen->mut_list);
4475 for (bd = gen->mut_list; bd != NULL; bd = bd->link) {
4476 for (p = bd->start; p < bd->free; p++) {
4477 debugBelch("%p (%s), ", (void *)*p, info_type((StgClosure *)*p));