1 /* -----------------------------------------------------------------------------
2 * $Id: GC.c,v 1.139 2002/09/05 16:26:33 simonmar Exp $
4 * (c) The GHC Team 1998-1999
6 * Generational garbage collector
8 * ---------------------------------------------------------------------------*/
10 #include "PosixSource.h"
15 #include "StoragePriv.h"
18 #include "SchedAPI.h" // for ReverCAFs prototype
20 #include "BlockAlloc.h"
26 #include "StablePriv.h"
28 #include "ParTicky.h" // ToDo: move into Rts.h
29 #include "GCCompact.h"
30 #if defined(GRAN) || defined(PAR)
31 # include "GranSimRts.h"
32 # include "ParallelRts.h"
36 # include "ParallelDebug.h"
41 #if defined(RTS_GTK_FRONTPANEL)
42 #include "FrontPanel.h"
45 #include "RetainerProfile.h"
46 #include "LdvProfile.h"
50 /* STATIC OBJECT LIST.
53 * We maintain a linked list of static objects that are still live.
54 * The requirements for this list are:
56 * - we need to scan the list while adding to it, in order to
57 * scavenge all the static objects (in the same way that
58 * breadth-first scavenging works for dynamic objects).
60 * - we need to be able to tell whether an object is already on
61 * the list, to break loops.
63 * Each static object has a "static link field", which we use for
64 * linking objects on to the list. We use a stack-type list, consing
65 * objects on the front as they are added (this means that the
66 * scavenge phase is depth-first, not breadth-first, but that
69 * A separate list is kept for objects that have been scavenged
70 * already - this is so that we can zero all the marks afterwards.
72 * An object is on the list if its static link field is non-zero; this
73 * means that we have to mark the end of the list with '1', not NULL.
75 * Extra notes for generational GC:
77 * Each generation has a static object list associated with it. When
78 * collecting generations up to N, we treat the static object lists
79 * from generations > N as roots.
81 * We build up a static object list while collecting generations 0..N,
82 * which is then appended to the static object list of generation N+1.
84 static StgClosure* static_objects; // live static objects
85 StgClosure* scavenged_static_objects; // static objects scavenged so far
87 /* N is the oldest generation being collected, where the generations
88 * are numbered starting at 0. A major GC (indicated by the major_gc
89 * flag) is when we're collecting all generations. We only attempt to
90 * deal with static objects and GC CAFs when doing a major GC.
93 static rtsBool major_gc;
95 /* Youngest generation that objects should be evacuated to in
96 * evacuate(). (Logically an argument to evacuate, but it's static
97 * a lot of the time so we optimise it into a global variable).
103 StgWeak *old_weak_ptr_list; // also pending finaliser list
105 /* Which stage of processing various kinds of weak pointer are we at?
106 * (see traverse_weak_ptr_list() below for discussion).
108 typedef enum { WeakPtrs, WeakThreads, WeakDone } WeakStage;
109 static WeakStage weak_stage;
111 /* List of all threads during GC
113 static StgTSO *old_all_threads;
114 StgTSO *resurrected_threads;
116 /* Flag indicating failure to evacuate an object to the desired
119 static rtsBool failed_to_evac;
121 /* Old to-space (used for two-space collector only)
123 static bdescr *old_to_blocks;
125 /* Data used for allocation area sizing.
127 static lnat new_blocks; // blocks allocated during this GC
128 static lnat g0s0_pcnt_kept = 30; // percentage of g0s0 live at last minor GC
130 /* Used to avoid long recursion due to selector thunks
132 static lnat thunk_selector_depth = 0;
133 #define MAX_THUNK_SELECTOR_DEPTH 256
135 /* -----------------------------------------------------------------------------
136 Static function declarations
137 -------------------------------------------------------------------------- */
139 static void mark_root ( StgClosure **root );
140 static StgClosure * evacuate ( StgClosure *q );
141 static void zero_static_object_list ( StgClosure* first_static );
142 static void zero_mutable_list ( StgMutClosure *first );
144 static rtsBool traverse_weak_ptr_list ( void );
145 static void mark_weak_ptr_list ( StgWeak **list );
147 static void scavenge ( step * );
148 static void scavenge_mark_stack ( void );
149 static void scavenge_stack ( StgPtr p, StgPtr stack_end );
150 static rtsBool scavenge_one ( StgPtr p );
151 static void scavenge_large ( step * );
152 static void scavenge_static ( void );
153 static void scavenge_mutable_list ( generation *g );
154 static void scavenge_mut_once_list ( generation *g );
156 #if 0 && defined(DEBUG)
157 static void gcCAFs ( void );
160 /* -----------------------------------------------------------------------------
161 inline functions etc. for dealing with the mark bitmap & stack.
162 -------------------------------------------------------------------------- */
164 #define MARK_STACK_BLOCKS 4
166 static bdescr *mark_stack_bdescr;
167 static StgPtr *mark_stack;
168 static StgPtr *mark_sp;
169 static StgPtr *mark_splim;
171 // Flag and pointers used for falling back to a linear scan when the
172 // mark stack overflows.
173 static rtsBool mark_stack_overflowed;
174 static bdescr *oldgen_scan_bd;
175 static StgPtr oldgen_scan;
177 static inline rtsBool
178 mark_stack_empty(void)
180 return mark_sp == mark_stack;
183 static inline rtsBool
184 mark_stack_full(void)
186 return mark_sp >= mark_splim;
190 reset_mark_stack(void)
192 mark_sp = mark_stack;
196 push_mark_stack(StgPtr p)
207 /* -----------------------------------------------------------------------------
210 For garbage collecting generation N (and all younger generations):
212 - follow all pointers in the root set. the root set includes all
213 mutable objects in all steps in all generations.
215 - for each pointer, evacuate the object it points to into either
216 + to-space in the next higher step in that generation, if one exists,
217 + if the object's generation == N, then evacuate it to the next
218 generation if one exists, or else to-space in the current
220 + if the object's generation < N, then evacuate it to to-space
221 in the next generation.
223 - repeatedly scavenge to-space from each step in each generation
224 being collected until no more objects can be evacuated.
226 - free from-space in each step, and set from-space = to-space.
228 Locks held: sched_mutex
230 -------------------------------------------------------------------------- */
233 GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc )
237 lnat live, allocated, collected = 0, copied = 0;
238 lnat oldgen_saved_blocks = 0;
242 CostCentreStack *prev_CCS;
245 #if defined(DEBUG) && defined(GRAN)
246 IF_DEBUG(gc, belch("@@ Starting garbage collection at %ld (%lx)\n",
250 // tell the stats department that we've started a GC
253 // Init stats and print par specific (timing) info
254 PAR_TICKY_PAR_START();
256 // attribute any costs to CCS_GC
262 /* Approximate how much we allocated.
263 * Todo: only when generating stats?
265 allocated = calcAllocated();
267 /* Figure out which generation to collect
269 if (force_major_gc) {
270 N = RtsFlags.GcFlags.generations - 1;
274 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
275 if (generations[g].steps[0].n_blocks +
276 generations[g].steps[0].n_large_blocks
277 >= generations[g].max_blocks) {
281 major_gc = (N == RtsFlags.GcFlags.generations-1);
284 #ifdef RTS_GTK_FRONTPANEL
285 if (RtsFlags.GcFlags.frontpanel) {
286 updateFrontPanelBeforeGC(N);
290 // check stack sanity *before* GC (ToDo: check all threads)
292 // ToDo!: check sanity IF_DEBUG(sanity, checkTSOsSanity());
294 IF_DEBUG(sanity, checkFreeListSanity());
296 /* Initialise the static object lists
298 static_objects = END_OF_STATIC_LIST;
299 scavenged_static_objects = END_OF_STATIC_LIST;
301 /* zero the mutable list for the oldest generation (see comment by
302 * zero_mutable_list below).
305 zero_mutable_list(generations[RtsFlags.GcFlags.generations-1].mut_once_list);
308 /* Save the old to-space if we're doing a two-space collection
310 if (RtsFlags.GcFlags.generations == 1) {
311 old_to_blocks = g0s0->to_blocks;
312 g0s0->to_blocks = NULL;
315 /* Keep a count of how many new blocks we allocated during this GC
316 * (used for resizing the allocation area, later).
320 /* Initialise to-space in all the generations/steps that we're
323 for (g = 0; g <= N; g++) {
324 generations[g].mut_once_list = END_MUT_LIST;
325 generations[g].mut_list = END_MUT_LIST;
327 for (s = 0; s < generations[g].n_steps; s++) {
329 // generation 0, step 0 doesn't need to-space
330 if (g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1) {
334 /* Get a free block for to-space. Extra blocks will be chained on
338 stp = &generations[g].steps[s];
339 ASSERT(stp->gen_no == g);
340 ASSERT(stp->hp ? Bdescr(stp->hp)->step == stp : rtsTrue);
344 bd->flags = BF_EVACUATED; // it's a to-space block
346 stp->hpLim = stp->hp + BLOCK_SIZE_W;
349 stp->n_to_blocks = 1;
350 stp->scan = bd->start;
352 stp->new_large_objects = NULL;
353 stp->scavenged_large_objects = NULL;
354 stp->n_scavenged_large_blocks = 0;
356 // mark the large objects as not evacuated yet
357 for (bd = stp->large_objects; bd; bd = bd->link) {
358 bd->flags = BF_LARGE;
361 // for a compacted step, we need to allocate the bitmap
362 if (stp->is_compacted) {
363 nat bitmap_size; // in bytes
364 bdescr *bitmap_bdescr;
367 bitmap_size = stp->n_blocks * BLOCK_SIZE / (sizeof(W_)*BITS_PER_BYTE);
369 if (bitmap_size > 0) {
370 bitmap_bdescr = allocGroup((nat)BLOCK_ROUND_UP(bitmap_size)
372 stp->bitmap = bitmap_bdescr;
373 bitmap = bitmap_bdescr->start;
375 IF_DEBUG(gc, belch("bitmap_size: %d, bitmap: %p",
376 bitmap_size, bitmap););
378 // don't forget to fill it with zeros!
379 memset(bitmap, 0, bitmap_size);
381 // for each block in this step, point to its bitmap from the
383 for (bd=stp->blocks; bd != NULL; bd = bd->link) {
384 bd->u.bitmap = bitmap;
385 bitmap += BLOCK_SIZE_W / (sizeof(W_)*BITS_PER_BYTE);
392 /* make sure the older generations have at least one block to
393 * allocate into (this makes things easier for copy(), see below.
395 for (g = N+1; g < RtsFlags.GcFlags.generations; g++) {
396 for (s = 0; s < generations[g].n_steps; s++) {
397 stp = &generations[g].steps[s];
398 if (stp->hp_bd == NULL) {
399 ASSERT(stp->blocks == NULL);
404 bd->flags = 0; // *not* a to-space block or a large object
406 stp->hpLim = stp->hp + BLOCK_SIZE_W;
412 /* Set the scan pointer for older generations: remember we
413 * still have to scavenge objects that have been promoted. */
415 stp->scan_bd = stp->hp_bd;
416 stp->to_blocks = NULL;
417 stp->n_to_blocks = 0;
418 stp->new_large_objects = NULL;
419 stp->scavenged_large_objects = NULL;
420 stp->n_scavenged_large_blocks = 0;
424 /* Allocate a mark stack if we're doing a major collection.
427 mark_stack_bdescr = allocGroup(MARK_STACK_BLOCKS);
428 mark_stack = (StgPtr *)mark_stack_bdescr->start;
429 mark_sp = mark_stack;
430 mark_splim = mark_stack + (MARK_STACK_BLOCKS * BLOCK_SIZE_W);
432 mark_stack_bdescr = NULL;
435 /* -----------------------------------------------------------------------
436 * follow all the roots that we know about:
437 * - mutable lists from each generation > N
438 * we want to *scavenge* these roots, not evacuate them: they're not
439 * going to move in this GC.
440 * Also: do them in reverse generation order. This is because we
441 * often want to promote objects that are pointed to by older
442 * generations early, so we don't have to repeatedly copy them.
443 * Doing the generations in reverse order ensures that we don't end
444 * up in the situation where we want to evac an object to gen 3 and
445 * it has already been evaced to gen 2.
449 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
450 generations[g].saved_mut_list = generations[g].mut_list;
451 generations[g].mut_list = END_MUT_LIST;
454 // Do the mut-once lists first
455 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
456 IF_PAR_DEBUG(verbose,
457 printMutOnceList(&generations[g]));
458 scavenge_mut_once_list(&generations[g]);
460 for (st = generations[g].n_steps-1; st >= 0; st--) {
461 scavenge(&generations[g].steps[st]);
465 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
466 IF_PAR_DEBUG(verbose,
467 printMutableList(&generations[g]));
468 scavenge_mutable_list(&generations[g]);
470 for (st = generations[g].n_steps-1; st >= 0; st--) {
471 scavenge(&generations[g].steps[st]);
476 /* follow roots from the CAF list (used by GHCi)
481 /* follow all the roots that the application knows about.
484 get_roots(mark_root);
487 /* And don't forget to mark the TSO if we got here direct from
489 /* Not needed in a seq version?
491 CurrentTSO = (StgTSO *)MarkRoot((StgClosure *)CurrentTSO);
495 // Mark the entries in the GALA table of the parallel system
496 markLocalGAs(major_gc);
497 // Mark all entries on the list of pending fetches
498 markPendingFetches(major_gc);
501 /* Mark the weak pointer list, and prepare to detect dead weak
504 mark_weak_ptr_list(&weak_ptr_list);
505 old_weak_ptr_list = weak_ptr_list;
506 weak_ptr_list = NULL;
507 weak_stage = WeakPtrs;
509 /* The all_threads list is like the weak_ptr_list.
510 * See traverse_weak_ptr_list() for the details.
512 old_all_threads = all_threads;
513 all_threads = END_TSO_QUEUE;
514 resurrected_threads = END_TSO_QUEUE;
516 /* Mark the stable pointer table.
518 markStablePtrTable(mark_root);
522 /* ToDo: To fix the caf leak, we need to make the commented out
523 * parts of this code do something sensible - as described in
526 extern void markHugsObjects(void);
531 /* -------------------------------------------------------------------------
532 * Repeatedly scavenge all the areas we know about until there's no
533 * more scavenging to be done.
540 // scavenge static objects
541 if (major_gc && static_objects != END_OF_STATIC_LIST) {
542 IF_DEBUG(sanity, checkStaticObjects(static_objects));
546 /* When scavenging the older generations: Objects may have been
547 * evacuated from generations <= N into older generations, and we
548 * need to scavenge these objects. We're going to try to ensure that
549 * any evacuations that occur move the objects into at least the
550 * same generation as the object being scavenged, otherwise we
551 * have to create new entries on the mutable list for the older
555 // scavenge each step in generations 0..maxgen
561 // scavenge objects in compacted generation
562 if (mark_stack_overflowed || oldgen_scan_bd != NULL ||
563 (mark_stack_bdescr != NULL && !mark_stack_empty())) {
564 scavenge_mark_stack();
568 for (gen = RtsFlags.GcFlags.generations; --gen >= 0; ) {
569 for (st = generations[gen].n_steps; --st >= 0; ) {
570 if (gen == 0 && st == 0 && RtsFlags.GcFlags.generations > 1) {
573 stp = &generations[gen].steps[st];
575 if (stp->hp_bd != stp->scan_bd || stp->scan < stp->hp) {
580 if (stp->new_large_objects != NULL) {
589 if (flag) { goto loop; }
591 // must be last... invariant is that everything is fully
592 // scavenged at this point.
593 if (traverse_weak_ptr_list()) { // returns rtsTrue if evaced something
598 /* Update the pointers from the "main thread" list - these are
599 * treated as weak pointers because we want to allow a main thread
600 * to get a BlockedOnDeadMVar exception in the same way as any other
601 * thread. Note that the threads should all have been retained by
602 * GC by virtue of being on the all_threads list, we're just
603 * updating pointers here.
608 for (m = main_threads; m != NULL; m = m->link) {
609 tso = (StgTSO *) isAlive((StgClosure *)m->tso);
611 barf("main thread has been GC'd");
618 // Reconstruct the Global Address tables used in GUM
619 rebuildGAtables(major_gc);
620 IF_DEBUG(sanity, checkLAGAtable(rtsTrue/*check closures, too*/));
623 // Now see which stable names are still alive.
626 // Tidy the end of the to-space chains
627 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
628 for (s = 0; s < generations[g].n_steps; s++) {
629 stp = &generations[g].steps[s];
630 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
631 stp->hp_bd->free = stp->hp;
632 stp->hp_bd->link = NULL;
638 // We call processHeapClosureForDead() on every closure destroyed during
639 // the current garbage collection, so we invoke LdvCensusForDead().
640 if (RtsFlags.ProfFlags.doHeapProfile == HEAP_BY_LDV
641 || RtsFlags.ProfFlags.bioSelector != NULL)
645 // NO MORE EVACUATION AFTER THIS POINT!
646 // Finally: compaction of the oldest generation.
647 if (major_gc && oldest_gen->steps[0].is_compacted) {
648 // save number of blocks for stats
649 oldgen_saved_blocks = oldest_gen->steps[0].n_blocks;
653 IF_DEBUG(sanity, checkGlobalTSOList(rtsFalse));
655 /* run through all the generations/steps and tidy up
657 copied = new_blocks * BLOCK_SIZE_W;
658 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
661 generations[g].collections++; // for stats
664 for (s = 0; s < generations[g].n_steps; s++) {
666 stp = &generations[g].steps[s];
668 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
669 // stats information: how much we copied
671 copied -= stp->hp_bd->start + BLOCK_SIZE_W -
676 // for generations we collected...
679 // rough calculation of garbage collected, for stats output
680 if (stp->is_compacted) {
681 collected += (oldgen_saved_blocks - stp->n_blocks) * BLOCK_SIZE_W;
683 collected += stp->n_blocks * BLOCK_SIZE_W;
686 /* free old memory and shift to-space into from-space for all
687 * the collected steps (except the allocation area). These
688 * freed blocks will probaby be quickly recycled.
690 if (!(g == 0 && s == 0)) {
691 if (stp->is_compacted) {
692 // for a compacted step, just shift the new to-space
693 // onto the front of the now-compacted existing blocks.
694 for (bd = stp->to_blocks; bd != NULL; bd = bd->link) {
695 bd->flags &= ~BF_EVACUATED; // now from-space
697 // tack the new blocks on the end of the existing blocks
698 if (stp->blocks == NULL) {
699 stp->blocks = stp->to_blocks;
701 for (bd = stp->blocks; bd != NULL; bd = next) {
704 bd->link = stp->to_blocks;
708 // add the new blocks to the block tally
709 stp->n_blocks += stp->n_to_blocks;
711 freeChain(stp->blocks);
712 stp->blocks = stp->to_blocks;
713 stp->n_blocks = stp->n_to_blocks;
714 for (bd = stp->blocks; bd != NULL; bd = bd->link) {
715 bd->flags &= ~BF_EVACUATED; // now from-space
718 stp->to_blocks = NULL;
719 stp->n_to_blocks = 0;
722 /* LARGE OBJECTS. The current live large objects are chained on
723 * scavenged_large, having been moved during garbage
724 * collection from large_objects. Any objects left on
725 * large_objects list are therefore dead, so we free them here.
727 for (bd = stp->large_objects; bd != NULL; bd = next) {
733 // update the count of blocks used by large objects
734 for (bd = stp->scavenged_large_objects; bd != NULL; bd = bd->link) {
735 bd->flags &= ~BF_EVACUATED;
737 stp->large_objects = stp->scavenged_large_objects;
738 stp->n_large_blocks = stp->n_scavenged_large_blocks;
741 // for older generations...
743 /* For older generations, we need to append the
744 * scavenged_large_object list (i.e. large objects that have been
745 * promoted during this GC) to the large_object list for that step.
747 for (bd = stp->scavenged_large_objects; bd; bd = next) {
749 bd->flags &= ~BF_EVACUATED;
750 dbl_link_onto(bd, &stp->large_objects);
753 // add the new blocks we promoted during this GC
754 stp->n_blocks += stp->n_to_blocks;
755 stp->n_large_blocks += stp->n_scavenged_large_blocks;
760 /* Reset the sizes of the older generations when we do a major
763 * CURRENT STRATEGY: make all generations except zero the same size.
764 * We have to stay within the maximum heap size, and leave a certain
765 * percentage of the maximum heap size available to allocate into.
767 if (major_gc && RtsFlags.GcFlags.generations > 1) {
768 nat live, size, min_alloc;
769 nat max = RtsFlags.GcFlags.maxHeapSize;
770 nat gens = RtsFlags.GcFlags.generations;
772 // live in the oldest generations
773 live = oldest_gen->steps[0].n_blocks +
774 oldest_gen->steps[0].n_large_blocks;
776 // default max size for all generations except zero
777 size = stg_max(live * RtsFlags.GcFlags.oldGenFactor,
778 RtsFlags.GcFlags.minOldGenSize);
780 // minimum size for generation zero
781 min_alloc = stg_max((RtsFlags.GcFlags.pcFreeHeap * max) / 200,
782 RtsFlags.GcFlags.minAllocAreaSize);
784 // Auto-enable compaction when the residency reaches a
785 // certain percentage of the maximum heap size (default: 30%).
786 if (RtsFlags.GcFlags.generations > 1 &&
787 (RtsFlags.GcFlags.compact ||
789 oldest_gen->steps[0].n_blocks >
790 (RtsFlags.GcFlags.compactThreshold * max) / 100))) {
791 oldest_gen->steps[0].is_compacted = 1;
792 // fprintf(stderr,"compaction: on\n", live);
794 oldest_gen->steps[0].is_compacted = 0;
795 // fprintf(stderr,"compaction: off\n", live);
798 // if we're going to go over the maximum heap size, reduce the
799 // size of the generations accordingly. The calculation is
800 // different if compaction is turned on, because we don't need
801 // to double the space required to collect the old generation.
804 // this test is necessary to ensure that the calculations
805 // below don't have any negative results - we're working
806 // with unsigned values here.
807 if (max < min_alloc) {
811 if (oldest_gen->steps[0].is_compacted) {
812 if ( (size + (size - 1) * (gens - 2) * 2) + min_alloc > max ) {
813 size = (max - min_alloc) / ((gens - 1) * 2 - 1);
816 if ( (size * (gens - 1) * 2) + min_alloc > max ) {
817 size = (max - min_alloc) / ((gens - 1) * 2);
827 fprintf(stderr,"live: %d, min_alloc: %d, size : %d, max = %d\n", live,
828 min_alloc, size, max);
831 for (g = 0; g < gens; g++) {
832 generations[g].max_blocks = size;
836 // Guess the amount of live data for stats.
839 /* Free the small objects allocated via allocate(), since this will
840 * all have been copied into G0S1 now.
842 if (small_alloc_list != NULL) {
843 freeChain(small_alloc_list);
845 small_alloc_list = NULL;
849 alloc_blocks_lim = RtsFlags.GcFlags.minAllocAreaSize;
851 // Start a new pinned_object_block
852 pinned_object_block = NULL;
854 /* Free the mark stack.
856 if (mark_stack_bdescr != NULL) {
857 freeGroup(mark_stack_bdescr);
862 for (g = 0; g <= N; g++) {
863 for (s = 0; s < generations[g].n_steps; s++) {
864 stp = &generations[g].steps[s];
865 if (stp->is_compacted && stp->bitmap != NULL) {
866 freeGroup(stp->bitmap);
871 /* Two-space collector:
872 * Free the old to-space, and estimate the amount of live data.
874 if (RtsFlags.GcFlags.generations == 1) {
877 if (old_to_blocks != NULL) {
878 freeChain(old_to_blocks);
880 for (bd = g0s0->to_blocks; bd != NULL; bd = bd->link) {
881 bd->flags = 0; // now from-space
884 /* For a two-space collector, we need to resize the nursery. */
886 /* set up a new nursery. Allocate a nursery size based on a
887 * function of the amount of live data (by default a factor of 2)
888 * Use the blocks from the old nursery if possible, freeing up any
891 * If we get near the maximum heap size, then adjust our nursery
892 * size accordingly. If the nursery is the same size as the live
893 * data (L), then we need 3L bytes. We can reduce the size of the
894 * nursery to bring the required memory down near 2L bytes.
896 * A normal 2-space collector would need 4L bytes to give the same
897 * performance we get from 3L bytes, reducing to the same
898 * performance at 2L bytes.
900 blocks = g0s0->n_to_blocks;
902 if ( RtsFlags.GcFlags.maxHeapSize != 0 &&
903 blocks * RtsFlags.GcFlags.oldGenFactor * 2 >
904 RtsFlags.GcFlags.maxHeapSize ) {
905 long adjusted_blocks; // signed on purpose
908 adjusted_blocks = (RtsFlags.GcFlags.maxHeapSize - 2 * blocks);
909 IF_DEBUG(gc, belch("@@ Near maximum heap size of 0x%x blocks, blocks = %d, adjusted to %ld", RtsFlags.GcFlags.maxHeapSize, blocks, adjusted_blocks));
910 pc_free = adjusted_blocks * 100 / RtsFlags.GcFlags.maxHeapSize;
911 if (pc_free < RtsFlags.GcFlags.pcFreeHeap) /* might even be < 0 */ {
914 blocks = adjusted_blocks;
917 blocks *= RtsFlags.GcFlags.oldGenFactor;
918 if (blocks < RtsFlags.GcFlags.minAllocAreaSize) {
919 blocks = RtsFlags.GcFlags.minAllocAreaSize;
922 resizeNursery(blocks);
925 /* Generational collector:
926 * If the user has given us a suggested heap size, adjust our
927 * allocation area to make best use of the memory available.
930 if (RtsFlags.GcFlags.heapSizeSuggestion) {
932 nat needed = calcNeeded(); // approx blocks needed at next GC
934 /* Guess how much will be live in generation 0 step 0 next time.
935 * A good approximation is obtained by finding the
936 * percentage of g0s0 that was live at the last minor GC.
939 g0s0_pcnt_kept = (new_blocks * 100) / g0s0->n_blocks;
942 /* Estimate a size for the allocation area based on the
943 * information available. We might end up going slightly under
944 * or over the suggested heap size, but we should be pretty
947 * Formula: suggested - needed
948 * ----------------------------
949 * 1 + g0s0_pcnt_kept/100
951 * where 'needed' is the amount of memory needed at the next
952 * collection for collecting all steps except g0s0.
955 (((long)RtsFlags.GcFlags.heapSizeSuggestion - (long)needed) * 100) /
956 (100 + (long)g0s0_pcnt_kept);
958 if (blocks < (long)RtsFlags.GcFlags.minAllocAreaSize) {
959 blocks = RtsFlags.GcFlags.minAllocAreaSize;
962 resizeNursery((nat)blocks);
965 // we might have added extra large blocks to the nursery, so
966 // resize back to minAllocAreaSize again.
967 resizeNursery(RtsFlags.GcFlags.minAllocAreaSize);
971 // mark the garbage collected CAFs as dead
972 #if 0 && defined(DEBUG) // doesn't work at the moment
973 if (major_gc) { gcCAFs(); }
977 // resetStaticObjectForRetainerProfiling() must be called before
979 resetStaticObjectForRetainerProfiling();
982 // zero the scavenged static object list
984 zero_static_object_list(scavenged_static_objects);
990 RELEASE_LOCK(&sched_mutex);
992 // start any pending finalizers
993 scheduleFinalizers(old_weak_ptr_list);
995 // send exceptions to any threads which were about to die
996 resurrectThreads(resurrected_threads);
998 ACQUIRE_LOCK(&sched_mutex);
1000 // Update the stable pointer hash table.
1001 updateStablePtrTable(major_gc);
1003 // check sanity after GC
1004 IF_DEBUG(sanity, checkSanity());
1006 // extra GC trace info
1007 IF_DEBUG(gc, statDescribeGens());
1010 // symbol-table based profiling
1011 /* heapCensus(to_blocks); */ /* ToDo */
1014 // restore enclosing cost centre
1019 // check for memory leaks if sanity checking is on
1020 IF_DEBUG(sanity, memInventory());
1022 #ifdef RTS_GTK_FRONTPANEL
1023 if (RtsFlags.GcFlags.frontpanel) {
1024 updateFrontPanelAfterGC( N, live );
1028 // ok, GC over: tell the stats department what happened.
1029 stat_endGC(allocated, collected, live, copied, N);
1035 /* -----------------------------------------------------------------------------
1038 traverse_weak_ptr_list is called possibly many times during garbage
1039 collection. It returns a flag indicating whether it did any work
1040 (i.e. called evacuate on any live pointers).
1042 Invariant: traverse_weak_ptr_list is called when the heap is in an
1043 idempotent state. That means that there are no pending
1044 evacuate/scavenge operations. This invariant helps the weak
1045 pointer code decide which weak pointers are dead - if there are no
1046 new live weak pointers, then all the currently unreachable ones are
1049 For generational GC: we just don't try to finalize weak pointers in
1050 older generations than the one we're collecting. This could
1051 probably be optimised by keeping per-generation lists of weak
1052 pointers, but for a few weak pointers this scheme will work.
1054 There are three distinct stages to processing weak pointers:
1056 - weak_stage == WeakPtrs
1058 We process all the weak pointers whos keys are alive (evacuate
1059 their values and finalizers), and repeat until we can find no new
1060 live keys. If no live keys are found in this pass, then we
1061 evacuate the finalizers of all the dead weak pointers in order to
1064 - weak_stage == WeakThreads
1066 Now, we discover which *threads* are still alive. Pointers to
1067 threads from the all_threads and main thread lists are the
1068 weakest of all: a pointers from the finalizer of a dead weak
1069 pointer can keep a thread alive. Any threads found to be unreachable
1070 are evacuated and placed on the resurrected_threads list so we
1071 can send them a signal later.
1073 - weak_stage == WeakDone
1075 No more evacuation is done.
1077 -------------------------------------------------------------------------- */
1080 traverse_weak_ptr_list(void)
1082 StgWeak *w, **last_w, *next_w;
1084 rtsBool flag = rtsFalse;
1086 switch (weak_stage) {
1092 /* doesn't matter where we evacuate values/finalizers to, since
1093 * these pointers are treated as roots (iff the keys are alive).
1097 last_w = &old_weak_ptr_list;
1098 for (w = old_weak_ptr_list; w != NULL; w = next_w) {
1100 /* There might be a DEAD_WEAK on the list if finalizeWeak# was
1101 * called on a live weak pointer object. Just remove it.
1103 if (w->header.info == &stg_DEAD_WEAK_info) {
1104 next_w = ((StgDeadWeak *)w)->link;
1109 switch (get_itbl(w)->type) {
1112 next_w = (StgWeak *)((StgEvacuated *)w)->evacuee;
1117 /* Now, check whether the key is reachable.
1119 new = isAlive(w->key);
1122 // evacuate the value and finalizer
1123 w->value = evacuate(w->value);
1124 w->finalizer = evacuate(w->finalizer);
1125 // remove this weak ptr from the old_weak_ptr list
1127 // and put it on the new weak ptr list
1129 w->link = weak_ptr_list;
1132 IF_DEBUG(weak, belch("Weak pointer still alive at %p -> %p",
1137 last_w = &(w->link);
1143 barf("traverse_weak_ptr_list: not WEAK");
1147 /* If we didn't make any changes, then we can go round and kill all
1148 * the dead weak pointers. The old_weak_ptr list is used as a list
1149 * of pending finalizers later on.
1151 if (flag == rtsFalse) {
1152 for (w = old_weak_ptr_list; w; w = w->link) {
1153 w->finalizer = evacuate(w->finalizer);
1156 // Next, move to the WeakThreads stage after fully
1157 // scavenging the finalizers we've just evacuated.
1158 weak_stage = WeakThreads;
1164 /* Now deal with the all_threads list, which behaves somewhat like
1165 * the weak ptr list. If we discover any threads that are about to
1166 * become garbage, we wake them up and administer an exception.
1169 StgTSO *t, *tmp, *next, **prev;
1171 prev = &old_all_threads;
1172 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1174 (StgClosure *)tmp = isAlive((StgClosure *)t);
1180 ASSERT(get_itbl(t)->type == TSO);
1181 switch (t->what_next) {
1182 case ThreadRelocated:
1187 case ThreadComplete:
1188 // finshed or died. The thread might still be alive, but we
1189 // don't keep it on the all_threads list. Don't forget to
1190 // stub out its global_link field.
1191 next = t->global_link;
1192 t->global_link = END_TSO_QUEUE;
1200 // not alive (yet): leave this thread on the
1201 // old_all_threads list.
1202 prev = &(t->global_link);
1203 next = t->global_link;
1206 // alive: move this thread onto the all_threads list.
1207 next = t->global_link;
1208 t->global_link = all_threads;
1215 /* And resurrect any threads which were about to become garbage.
1218 StgTSO *t, *tmp, *next;
1219 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1220 next = t->global_link;
1221 (StgClosure *)tmp = evacuate((StgClosure *)t);
1222 tmp->global_link = resurrected_threads;
1223 resurrected_threads = tmp;
1227 weak_stage = WeakDone; // *now* we're done,
1228 return rtsTrue; // but one more round of scavenging, please
1231 barf("traverse_weak_ptr_list");
1236 /* -----------------------------------------------------------------------------
1237 After GC, the live weak pointer list may have forwarding pointers
1238 on it, because a weak pointer object was evacuated after being
1239 moved to the live weak pointer list. We remove those forwarding
1242 Also, we don't consider weak pointer objects to be reachable, but
1243 we must nevertheless consider them to be "live" and retain them.
1244 Therefore any weak pointer objects which haven't as yet been
1245 evacuated need to be evacuated now.
1246 -------------------------------------------------------------------------- */
1250 mark_weak_ptr_list ( StgWeak **list )
1252 StgWeak *w, **last_w;
1255 for (w = *list; w; w = w->link) {
1256 // w might be WEAK, EVACUATED, or DEAD_WEAK (actually CON_STATIC) here
1257 ASSERT(w->header.info == &stg_DEAD_WEAK_info
1258 || get_itbl(w)->type == WEAK || get_itbl(w)->type == EVACUATED);
1259 (StgClosure *)w = evacuate((StgClosure *)w);
1261 last_w = &(w->link);
1265 /* -----------------------------------------------------------------------------
1266 isAlive determines whether the given closure is still alive (after
1267 a garbage collection) or not. It returns the new address of the
1268 closure if it is alive, or NULL otherwise.
1270 NOTE: Use it before compaction only!
1271 -------------------------------------------------------------------------- */
1275 isAlive(StgClosure *p)
1277 const StgInfoTable *info;
1284 /* ToDo: for static closures, check the static link field.
1285 * Problem here is that we sometimes don't set the link field, eg.
1286 * for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
1292 // ignore closures in generations that we're not collecting.
1293 if (LOOKS_LIKE_STATIC(p) || bd->gen_no > N) {
1296 // large objects have an evacuated flag
1297 if (bd->flags & BF_LARGE) {
1298 if (bd->flags & BF_EVACUATED) {
1304 // check the mark bit for compacted steps
1305 if (bd->step->is_compacted && is_marked((P_)p,bd)) {
1309 switch (info->type) {
1314 case IND_OLDGEN: // rely on compatible layout with StgInd
1315 case IND_OLDGEN_PERM:
1316 // follow indirections
1317 p = ((StgInd *)p)->indirectee;
1322 return ((StgEvacuated *)p)->evacuee;
1325 if (((StgTSO *)p)->what_next == ThreadRelocated) {
1326 p = (StgClosure *)((StgTSO *)p)->link;
1338 mark_root(StgClosure **root)
1340 *root = evacuate(*root);
1346 bdescr *bd = allocBlock();
1347 bd->gen_no = stp->gen_no;
1350 if (stp->gen_no <= N) {
1351 bd->flags = BF_EVACUATED;
1356 stp->hp_bd->free = stp->hp;
1357 stp->hp_bd->link = bd;
1358 stp->hp = bd->start;
1359 stp->hpLim = stp->hp + BLOCK_SIZE_W;
1366 static __inline__ void
1367 upd_evacuee(StgClosure *p, StgClosure *dest)
1369 p->header.info = &stg_EVACUATED_info;
1370 ((StgEvacuated *)p)->evacuee = dest;
1374 static __inline__ StgClosure *
1375 copy(StgClosure *src, nat size, step *stp)
1380 nat size_org = size;
1383 TICK_GC_WORDS_COPIED(size);
1384 /* Find out where we're going, using the handy "to" pointer in
1385 * the step of the source object. If it turns out we need to
1386 * evacuate to an older generation, adjust it here (see comment
1389 if (stp->gen_no < evac_gen) {
1390 #ifdef NO_EAGER_PROMOTION
1391 failed_to_evac = rtsTrue;
1393 stp = &generations[evac_gen].steps[0];
1397 /* chain a new block onto the to-space for the destination step if
1400 if (stp->hp + size >= stp->hpLim) {
1404 for(to = stp->hp, from = (P_)src; size>0; --size) {
1410 upd_evacuee(src,(StgClosure *)dest);
1412 // We store the size of the just evacuated object in the LDV word so that
1413 // the profiler can guess the position of the next object later.
1414 SET_EVACUAEE_FOR_LDV(src, size_org);
1416 return (StgClosure *)dest;
1419 /* Special version of copy() for when we only want to copy the info
1420 * pointer of an object, but reserve some padding after it. This is
1421 * used to optimise evacuation of BLACKHOLEs.
1426 copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *stp)
1431 nat size_to_copy_org = size_to_copy;
1434 TICK_GC_WORDS_COPIED(size_to_copy);
1435 if (stp->gen_no < evac_gen) {
1436 #ifdef NO_EAGER_PROMOTION
1437 failed_to_evac = rtsTrue;
1439 stp = &generations[evac_gen].steps[0];
1443 if (stp->hp + size_to_reserve >= stp->hpLim) {
1447 for(to = stp->hp, from = (P_)src; size_to_copy>0; --size_to_copy) {
1452 stp->hp += size_to_reserve;
1453 upd_evacuee(src,(StgClosure *)dest);
1455 // We store the size of the just evacuated object in the LDV word so that
1456 // the profiler can guess the position of the next object later.
1457 // size_to_copy_org is wrong because the closure already occupies size_to_reserve
1459 SET_EVACUAEE_FOR_LDV(src, size_to_reserve);
1461 if (size_to_reserve - size_to_copy_org > 0)
1462 FILL_SLOP(stp->hp - 1, (int)(size_to_reserve - size_to_copy_org));
1464 return (StgClosure *)dest;
1468 /* -----------------------------------------------------------------------------
1469 Evacuate a large object
1471 This just consists of removing the object from the (doubly-linked)
1472 step->large_objects list, and linking it on to the (singly-linked)
1473 step->new_large_objects list, from where it will be scavenged later.
1475 Convention: bd->flags has BF_EVACUATED set for a large object
1476 that has been evacuated, or unset otherwise.
1477 -------------------------------------------------------------------------- */
1481 evacuate_large(StgPtr p)
1483 bdescr *bd = Bdescr(p);
1486 // object must be at the beginning of the block (or be a ByteArray)
1487 ASSERT(get_itbl((StgClosure *)p)->type == ARR_WORDS ||
1488 (((W_)p & BLOCK_MASK) == 0));
1490 // already evacuated?
1491 if (bd->flags & BF_EVACUATED) {
1492 /* Don't forget to set the failed_to_evac flag if we didn't get
1493 * the desired destination (see comments in evacuate()).
1495 if (bd->gen_no < evac_gen) {
1496 failed_to_evac = rtsTrue;
1497 TICK_GC_FAILED_PROMOTION();
1503 // remove from large_object list
1505 bd->u.back->link = bd->link;
1506 } else { // first object in the list
1507 stp->large_objects = bd->link;
1510 bd->link->u.back = bd->u.back;
1513 /* link it on to the evacuated large object list of the destination step
1516 if (stp->gen_no < evac_gen) {
1517 #ifdef NO_EAGER_PROMOTION
1518 failed_to_evac = rtsTrue;
1520 stp = &generations[evac_gen].steps[0];
1525 bd->gen_no = stp->gen_no;
1526 bd->link = stp->new_large_objects;
1527 stp->new_large_objects = bd;
1528 bd->flags |= BF_EVACUATED;
1531 /* -----------------------------------------------------------------------------
1532 Adding a MUT_CONS to an older generation.
1534 This is necessary from time to time when we end up with an
1535 old-to-new generation pointer in a non-mutable object. We defer
1536 the promotion until the next GC.
1537 -------------------------------------------------------------------------- */
1541 mkMutCons(StgClosure *ptr, generation *gen)
1546 stp = &gen->steps[0];
1548 /* chain a new block onto the to-space for the destination step if
1551 if (stp->hp + sizeofW(StgIndOldGen) >= stp->hpLim) {
1555 q = (StgMutVar *)stp->hp;
1556 stp->hp += sizeofW(StgMutVar);
1558 SET_HDR(q,&stg_MUT_CONS_info,CCS_GC);
1560 recordOldToNewPtrs((StgMutClosure *)q);
1562 return (StgClosure *)q;
1565 /* -----------------------------------------------------------------------------
1568 This is called (eventually) for every live object in the system.
1570 The caller to evacuate specifies a desired generation in the
1571 evac_gen global variable. The following conditions apply to
1572 evacuating an object which resides in generation M when we're
1573 collecting up to generation N
1577 else evac to step->to
1579 if M < evac_gen evac to evac_gen, step 0
1581 if the object is already evacuated, then we check which generation
1584 if M >= evac_gen do nothing
1585 if M < evac_gen set failed_to_evac flag to indicate that we
1586 didn't manage to evacuate this object into evac_gen.
1588 -------------------------------------------------------------------------- */
1591 evacuate(StgClosure *q)
1596 const StgInfoTable *info;
1599 if (HEAP_ALLOCED(q)) {
1602 if (bd->gen_no > N) {
1603 /* Can't evacuate this object, because it's in a generation
1604 * older than the ones we're collecting. Let's hope that it's
1605 * in evac_gen or older, or we will have to arrange to track
1606 * this pointer using the mutable list.
1608 if (bd->gen_no < evac_gen) {
1610 failed_to_evac = rtsTrue;
1611 TICK_GC_FAILED_PROMOTION();
1616 /* evacuate large objects by re-linking them onto a different list.
1618 if (bd->flags & BF_LARGE) {
1620 if (info->type == TSO &&
1621 ((StgTSO *)q)->what_next == ThreadRelocated) {
1622 q = (StgClosure *)((StgTSO *)q)->link;
1625 evacuate_large((P_)q);
1629 /* If the object is in a step that we're compacting, then we
1630 * need to use an alternative evacuate procedure.
1632 if (bd->step->is_compacted) {
1633 if (!is_marked((P_)q,bd)) {
1635 if (mark_stack_full()) {
1636 mark_stack_overflowed = rtsTrue;
1639 push_mark_stack((P_)q);
1647 else stp = NULL; // make sure copy() will crash if HEAP_ALLOCED is wrong
1650 // make sure the info pointer is into text space
1651 ASSERT(q && (LOOKS_LIKE_GHC_INFO(GET_INFO(q))
1652 || IS_HUGS_CONSTR_INFO(GET_INFO(q))));
1655 switch (info -> type) {
1659 to = copy(q,sizeW_fromITBL(info),stp);
1664 StgWord w = (StgWord)q->payload[0];
1665 if (q->header.info == Czh_con_info &&
1666 // unsigned, so always true: (StgChar)w >= MIN_CHARLIKE &&
1667 (StgChar)w <= MAX_CHARLIKE) {
1668 return (StgClosure *)CHARLIKE_CLOSURE((StgChar)w);
1670 if (q->header.info == Izh_con_info &&
1671 (StgInt)w >= MIN_INTLIKE && (StgInt)w <= MAX_INTLIKE) {
1672 return (StgClosure *)INTLIKE_CLOSURE((StgInt)w);
1674 // else, fall through ...
1680 return copy(q,sizeofW(StgHeader)+1,stp);
1682 case THUNK_1_0: // here because of MIN_UPD_SIZE
1687 #ifdef NO_PROMOTE_THUNKS
1688 if (bd->gen_no == 0 &&
1689 bd->step->no != 0 &&
1690 bd->step->no == generations[bd->gen_no].n_steps-1) {
1694 return copy(q,sizeofW(StgHeader)+2,stp);
1702 return copy(q,sizeofW(StgHeader)+2,stp);
1708 case IND_OLDGEN_PERM:
1713 return copy(q,sizeW_fromITBL(info),stp);
1716 case SE_CAF_BLACKHOLE:
1719 return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
1722 to = copy(q,BLACKHOLE_sizeW(),stp);
1725 case THUNK_SELECTOR:
1727 const StgInfoTable* selectee_info;
1728 StgClosure* selectee = ((StgSelector*)q)->selectee;
1730 // We only recurse a certain depth through selector thunks.
1731 // NOTE: the depth is maintained manually, and we must be very
1732 // careful to always decrement it before returning.
1734 thunk_selector_depth++;
1735 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
1736 goto selector_abandon;
1740 selectee_info = get_itbl(selectee);
1741 switch (selectee_info->type) {
1749 case CONSTR_NOCAF_STATIC:
1751 StgWord offset = info->layout.selector_offset;
1753 // check that the size is in range
1755 (StgWord32)(selectee_info->layout.payload.ptrs +
1756 selectee_info->layout.payload.nptrs));
1758 // The thunk is now under evaluation, so we overwrite it
1759 // with a BLACKHOLE. This has a beneficial effect if the
1760 // selector thunk eventually refers to itself: we won't
1761 // recurse indefinitely, and the object which eventually
1762 // gets evacuated will be a BLACKHOLE (as it should be: a
1763 // selector thunk which refers to itself can only have value
1765 SET_INFO(q,&stg_BLACKHOLE_info);
1767 // perform the selection!
1768 selectee = selectee->payload[offset];
1769 if (major_gc==rtsTrue) {TICK_GC_SEL_MAJOR();} else {TICK_GC_SEL_MINOR();}
1770 // Carry on and evacuate this constructor field,
1771 // (but not the constructor itself)
1773 // It is tempting to just 'goto loop;' at this point, but
1774 // that doesn't give us a way to decrement
1775 // thunk_selector_depth later. So we recurse (boundedly)
1778 selectee = evacuate(selectee);
1779 upd_evacuee(q,selectee);
1780 thunk_selector_depth--;
1788 case IND_OLDGEN_PERM:
1789 selectee = ((StgInd *)selectee)->indirectee;
1793 // We could follow forwarding pointers here too, but we don't
1795 // * If the constructor has already been evacuated, then
1796 // we're only doing the evaluation early, not fixing a
1798 // * When we finally reach the destination, we have to
1799 // figure out whether we are in to-space or not, and this
1800 // is somewhat awkward.
1802 // selectee = ((StgEvacuated *)selectee)->evacuee;
1803 // goto selector_loop;
1806 case THUNK_SELECTOR:
1807 /* we can't recurse indefinitely in evacuate(), so set a
1808 * limit on the number of times we can go around this
1811 q = evacuate(selectee);
1812 thunk_selector_depth--;
1824 case SE_CAF_BLACKHOLE:
1828 // not evaluated yet
1832 // a copy of the top-level cases below
1833 case RBH: // cf. BLACKHOLE_BQ
1835 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
1836 to = copy(q,BLACKHOLE_sizeW(),stp);
1837 //ToDo: derive size etc from reverted IP
1838 //to = copy(q,size,stp);
1839 // recordMutable((StgMutClosure *)to);
1840 thunk_selector_depth--;
1845 ASSERT(sizeofW(StgBlockedFetch) >= MIN_NONUPD_SIZE);
1846 to = copy(q,sizeofW(StgBlockedFetch),stp);
1847 thunk_selector_depth--;
1854 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1855 to = copy(q,sizeofW(StgFetchMe),stp);
1856 thunk_selector_depth--;
1860 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1861 to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
1862 thunk_selector_depth--;
1867 barf("evacuate: THUNK_SELECTOR: strange selectee %d",
1868 (int)(selectee_info->type));
1872 thunk_selector_depth--;
1873 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1877 // follow chains of indirections, don't evacuate them
1878 q = ((StgInd*)q)->indirectee;
1882 if (info->srt_len > 0 && major_gc &&
1883 THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
1884 THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
1885 static_objects = (StgClosure *)q;
1890 if (info->srt_len > 0 && major_gc &&
1891 FUN_STATIC_LINK((StgClosure *)q) == NULL) {
1892 FUN_STATIC_LINK((StgClosure *)q) = static_objects;
1893 static_objects = (StgClosure *)q;
1898 /* If q->saved_info != NULL, then it's a revertible CAF - it'll be
1899 * on the CAF list, so don't do anything with it here (we'll
1900 * scavenge it later).
1903 && ((StgIndStatic *)q)->saved_info == NULL
1904 && IND_STATIC_LINK((StgClosure *)q) == NULL) {
1905 IND_STATIC_LINK((StgClosure *)q) = static_objects;
1906 static_objects = (StgClosure *)q;
1911 if (major_gc && STATIC_LINK(info,(StgClosure *)q) == NULL) {
1912 STATIC_LINK(info,(StgClosure *)q) = static_objects;
1913 static_objects = (StgClosure *)q;
1917 case CONSTR_INTLIKE:
1918 case CONSTR_CHARLIKE:
1919 case CONSTR_NOCAF_STATIC:
1920 /* no need to put these on the static linked list, they don't need
1935 // shouldn't see these
1936 barf("evacuate: stack frame at %p\n", q);
1940 /* PAPs and AP_UPDs are special - the payload is a copy of a chunk
1941 * of stack, tagging and all.
1943 return copy(q,pap_sizeW((StgPAP*)q),stp);
1946 /* Already evacuated, just return the forwarding address.
1947 * HOWEVER: if the requested destination generation (evac_gen) is
1948 * older than the actual generation (because the object was
1949 * already evacuated to a younger generation) then we have to
1950 * set the failed_to_evac flag to indicate that we couldn't
1951 * manage to promote the object to the desired generation.
1953 if (evac_gen > 0) { // optimisation
1954 StgClosure *p = ((StgEvacuated*)q)->evacuee;
1955 if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < evac_gen) {
1956 failed_to_evac = rtsTrue;
1957 TICK_GC_FAILED_PROMOTION();
1960 return ((StgEvacuated*)q)->evacuee;
1963 // just copy the block
1964 return copy(q,arr_words_sizeW((StgArrWords *)q),stp);
1967 case MUT_ARR_PTRS_FROZEN:
1968 // just copy the block
1969 return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
1973 StgTSO *tso = (StgTSO *)q;
1975 /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
1977 if (tso->what_next == ThreadRelocated) {
1978 q = (StgClosure *)tso->link;
1982 /* To evacuate a small TSO, we need to relocate the update frame
1986 StgTSO *new_tso = (StgTSO *)copy((StgClosure *)tso,tso_sizeW(tso),stp);
1987 move_TSO(tso, new_tso);
1988 return (StgClosure *)new_tso;
1993 case RBH: // cf. BLACKHOLE_BQ
1995 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
1996 to = copy(q,BLACKHOLE_sizeW(),stp);
1997 //ToDo: derive size etc from reverted IP
1998 //to = copy(q,size,stp);
2000 belch("@@ evacuate: RBH %p (%s) to %p (%s)",
2001 q, info_type(q), to, info_type(to)));
2006 ASSERT(sizeofW(StgBlockedFetch) >= MIN_NONUPD_SIZE);
2007 to = copy(q,sizeofW(StgBlockedFetch),stp);
2009 belch("@@ evacuate: %p (%s) to %p (%s)",
2010 q, info_type(q), to, info_type(to)));
2017 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
2018 to = copy(q,sizeofW(StgFetchMe),stp);
2020 belch("@@ evacuate: %p (%s) to %p (%s)",
2021 q, info_type(q), to, info_type(to)));
2025 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
2026 to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
2028 belch("@@ evacuate: %p (%s) to %p (%s)",
2029 q, info_type(q), to, info_type(to)));
2034 barf("evacuate: strange closure type %d", (int)(info->type));
2040 /* -----------------------------------------------------------------------------
2041 move_TSO is called to update the TSO structure after it has been
2042 moved from one place to another.
2043 -------------------------------------------------------------------------- */
2046 move_TSO(StgTSO *src, StgTSO *dest)
2050 // relocate the stack pointers...
2051 diff = (StgPtr)dest - (StgPtr)src; // In *words*
2052 dest->sp = (StgPtr)dest->sp + diff;
2053 dest->su = (StgUpdateFrame *) ((P_)dest->su + diff);
2055 relocate_stack(dest, diff);
2058 /* -----------------------------------------------------------------------------
2059 relocate_stack is called to update the linkage between
2060 UPDATE_FRAMEs (and SEQ_FRAMEs etc.) when a stack is moved from one
2062 -------------------------------------------------------------------------- */
2065 relocate_stack(StgTSO *dest, ptrdiff_t diff)
2073 while ((P_)su < dest->stack + dest->stack_size) {
2074 switch (get_itbl(su)->type) {
2076 // GCC actually manages to common up these three cases!
2079 su->link = (StgUpdateFrame *) ((StgPtr)su->link + diff);
2084 cf = (StgCatchFrame *)su;
2085 cf->link = (StgUpdateFrame *) ((StgPtr)cf->link + diff);
2090 sf = (StgSeqFrame *)su;
2091 sf->link = (StgUpdateFrame *) ((StgPtr)sf->link + diff);
2100 barf("relocate_stack %d", (int)(get_itbl(su)->type));
2111 scavenge_srt(const StgInfoTable *info)
2113 StgClosure **srt, **srt_end;
2115 /* evacuate the SRT. If srt_len is zero, then there isn't an
2116 * srt field in the info table. That's ok, because we'll
2117 * never dereference it.
2119 srt = (StgClosure **)(info->srt);
2120 srt_end = srt + info->srt_len;
2121 for (; srt < srt_end; srt++) {
2122 /* Special-case to handle references to closures hiding out in DLLs, since
2123 double indirections required to get at those. The code generator knows
2124 which is which when generating the SRT, so it stores the (indirect)
2125 reference to the DLL closure in the table by first adding one to it.
2126 We check for this here, and undo the addition before evacuating it.
2128 If the SRT entry hasn't got bit 0 set, the SRT entry points to a
2129 closure that's fixed at link-time, and no extra magic is required.
2131 #ifdef ENABLE_WIN32_DLL_SUPPORT
2132 if ( (unsigned long)(*srt) & 0x1 ) {
2133 evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
2143 /* -----------------------------------------------------------------------------
2145 -------------------------------------------------------------------------- */
2148 scavengeTSO (StgTSO *tso)
2150 // chase the link field for any TSOs on the same queue
2151 (StgClosure *)tso->link = evacuate((StgClosure *)tso->link);
2152 if ( tso->why_blocked == BlockedOnMVar
2153 || tso->why_blocked == BlockedOnBlackHole
2154 || tso->why_blocked == BlockedOnException
2156 || tso->why_blocked == BlockedOnGA
2157 || tso->why_blocked == BlockedOnGA_NoSend
2160 tso->block_info.closure = evacuate(tso->block_info.closure);
2162 if ( tso->blocked_exceptions != NULL ) {
2163 tso->blocked_exceptions =
2164 (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
2166 // scavenge this thread's stack
2167 scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
2170 /* -----------------------------------------------------------------------------
2171 Scavenge a given step until there are no more objects in this step
2174 evac_gen is set by the caller to be either zero (for a step in a
2175 generation < N) or G where G is the generation of the step being
2178 We sometimes temporarily change evac_gen back to zero if we're
2179 scavenging a mutable object where early promotion isn't such a good
2181 -------------------------------------------------------------------------- */
2189 nat saved_evac_gen = evac_gen;
2194 failed_to_evac = rtsFalse;
2196 /* scavenge phase - standard breadth-first scavenging of the
2200 while (bd != stp->hp_bd || p < stp->hp) {
2202 // If we're at the end of this block, move on to the next block
2203 if (bd != stp->hp_bd && p == bd->free) {
2209 info = get_itbl((StgClosure *)p);
2210 ASSERT(p && (LOOKS_LIKE_GHC_INFO(info) || IS_HUGS_CONSTR_INFO(info)));
2212 ASSERT(thunk_selector_depth == 0);
2215 switch (info->type) {
2218 /* treat MVars specially, because we don't want to evacuate the
2219 * mut_link field in the middle of the closure.
2222 StgMVar *mvar = ((StgMVar *)p);
2224 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
2225 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
2226 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
2227 evac_gen = saved_evac_gen;
2228 recordMutable((StgMutClosure *)mvar);
2229 failed_to_evac = rtsFalse; // mutable.
2230 p += sizeofW(StgMVar);
2238 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2239 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2240 p += sizeofW(StgHeader) + 2;
2245 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2246 p += sizeofW(StgHeader) + 2; // MIN_UPD_SIZE
2252 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2253 p += sizeofW(StgHeader) + 1;
2258 p += sizeofW(StgHeader) + 2; // MIN_UPD_SIZE
2264 p += sizeofW(StgHeader) + 1;
2271 p += sizeofW(StgHeader) + 2;
2278 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2279 p += sizeofW(StgHeader) + 2;
2295 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2296 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2297 (StgClosure *)*p = evacuate((StgClosure *)*p);
2299 p += info->layout.payload.nptrs;
2304 if (stp->gen->no != 0) {
2307 // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an
2308 // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
2309 LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
2312 // Todo: maybe use SET_HDR() and remove LDV_recordCreate()?
2314 SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
2317 // We pretend that p has just been created.
2318 LDV_recordCreate((StgClosure *)p);
2322 case IND_OLDGEN_PERM:
2323 ((StgIndOldGen *)p)->indirectee =
2324 evacuate(((StgIndOldGen *)p)->indirectee);
2325 if (failed_to_evac) {
2326 failed_to_evac = rtsFalse;
2327 recordOldToNewPtrs((StgMutClosure *)p);
2329 p += sizeofW(StgIndOldGen);
2334 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2335 evac_gen = saved_evac_gen;
2336 recordMutable((StgMutClosure *)p);
2337 failed_to_evac = rtsFalse; // mutable anyhow
2338 p += sizeofW(StgMutVar);
2343 failed_to_evac = rtsFalse; // mutable anyhow
2344 p += sizeofW(StgMutVar);
2348 case SE_CAF_BLACKHOLE:
2351 p += BLACKHOLE_sizeW();
2356 StgBlockingQueue *bh = (StgBlockingQueue *)p;
2357 (StgClosure *)bh->blocking_queue =
2358 evacuate((StgClosure *)bh->blocking_queue);
2359 recordMutable((StgMutClosure *)bh);
2360 failed_to_evac = rtsFalse;
2361 p += BLACKHOLE_sizeW();
2365 case THUNK_SELECTOR:
2367 StgSelector *s = (StgSelector *)p;
2368 s->selectee = evacuate(s->selectee);
2369 p += THUNK_SELECTOR_sizeW();
2373 case AP_UPD: // same as PAPs
2375 /* Treat a PAP just like a section of stack, not forgetting to
2376 * evacuate the function pointer too...
2379 StgPAP* pap = (StgPAP *)p;
2381 pap->fun = evacuate(pap->fun);
2382 scavenge_stack((P_)pap->payload, (P_)pap->payload + pap->n_args);
2383 p += pap_sizeW(pap);
2388 // nothing to follow
2389 p += arr_words_sizeW((StgArrWords *)p);
2393 // follow everything
2397 evac_gen = 0; // repeatedly mutable
2398 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2399 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2400 (StgClosure *)*p = evacuate((StgClosure *)*p);
2402 evac_gen = saved_evac_gen;
2403 recordMutable((StgMutClosure *)q);
2404 failed_to_evac = rtsFalse; // mutable anyhow.
2408 case MUT_ARR_PTRS_FROZEN:
2409 // follow everything
2413 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2414 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2415 (StgClosure *)*p = evacuate((StgClosure *)*p);
2417 // it's tempting to recordMutable() if failed_to_evac is
2418 // false, but that breaks some assumptions (eg. every
2419 // closure on the mutable list is supposed to have the MUT
2420 // flag set, and MUT_ARR_PTRS_FROZEN doesn't).
2426 StgTSO *tso = (StgTSO *)p;
2429 evac_gen = saved_evac_gen;
2430 recordMutable((StgMutClosure *)tso);
2431 failed_to_evac = rtsFalse; // mutable anyhow.
2432 p += tso_sizeW(tso);
2437 case RBH: // cf. BLACKHOLE_BQ
2440 nat size, ptrs, nonptrs, vhs;
2442 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2444 StgRBH *rbh = (StgRBH *)p;
2445 (StgClosure *)rbh->blocking_queue =
2446 evacuate((StgClosure *)rbh->blocking_queue);
2447 recordMutable((StgMutClosure *)to);
2448 failed_to_evac = rtsFalse; // mutable anyhow.
2450 belch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2451 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2452 // ToDo: use size of reverted closure here!
2453 p += BLACKHOLE_sizeW();
2459 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2460 // follow the pointer to the node which is being demanded
2461 (StgClosure *)bf->node =
2462 evacuate((StgClosure *)bf->node);
2463 // follow the link to the rest of the blocking queue
2464 (StgClosure *)bf->link =
2465 evacuate((StgClosure *)bf->link);
2466 if (failed_to_evac) {
2467 failed_to_evac = rtsFalse;
2468 recordMutable((StgMutClosure *)bf);
2471 belch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
2472 bf, info_type((StgClosure *)bf),
2473 bf->node, info_type(bf->node)));
2474 p += sizeofW(StgBlockedFetch);
2482 p += sizeofW(StgFetchMe);
2483 break; // nothing to do in this case
2485 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
2487 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
2488 (StgClosure *)fmbq->blocking_queue =
2489 evacuate((StgClosure *)fmbq->blocking_queue);
2490 if (failed_to_evac) {
2491 failed_to_evac = rtsFalse;
2492 recordMutable((StgMutClosure *)fmbq);
2495 belch("@@ scavenge: %p (%s) exciting, isn't it",
2496 p, info_type((StgClosure *)p)));
2497 p += sizeofW(StgFetchMeBlockingQueue);
2503 barf("scavenge: unimplemented/strange closure type %d @ %p",
2507 /* If we didn't manage to promote all the objects pointed to by
2508 * the current object, then we have to designate this object as
2509 * mutable (because it contains old-to-new generation pointers).
2511 if (failed_to_evac) {
2512 failed_to_evac = rtsFalse;
2513 mkMutCons((StgClosure *)q, &generations[evac_gen]);
2521 /* -----------------------------------------------------------------------------
2522 Scavenge everything on the mark stack.
2524 This is slightly different from scavenge():
2525 - we don't walk linearly through the objects, so the scavenger
2526 doesn't need to advance the pointer on to the next object.
2527 -------------------------------------------------------------------------- */
2530 scavenge_mark_stack(void)
2536 evac_gen = oldest_gen->no;
2537 saved_evac_gen = evac_gen;
2540 while (!mark_stack_empty()) {
2541 p = pop_mark_stack();
2543 info = get_itbl((StgClosure *)p);
2544 ASSERT(p && (LOOKS_LIKE_GHC_INFO(info) || IS_HUGS_CONSTR_INFO(info)));
2547 switch (info->type) {
2550 /* treat MVars specially, because we don't want to evacuate the
2551 * mut_link field in the middle of the closure.
2554 StgMVar *mvar = ((StgMVar *)p);
2556 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
2557 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
2558 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
2559 evac_gen = saved_evac_gen;
2560 failed_to_evac = rtsFalse; // mutable.
2568 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2569 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2579 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2604 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2605 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2606 (StgClosure *)*p = evacuate((StgClosure *)*p);
2612 // don't need to do anything here: the only possible case
2613 // is that we're in a 1-space compacting collector, with
2614 // no "old" generation.
2618 case IND_OLDGEN_PERM:
2619 ((StgIndOldGen *)p)->indirectee =
2620 evacuate(((StgIndOldGen *)p)->indirectee);
2621 if (failed_to_evac) {
2622 recordOldToNewPtrs((StgMutClosure *)p);
2624 failed_to_evac = rtsFalse;
2629 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2630 evac_gen = saved_evac_gen;
2631 failed_to_evac = rtsFalse;
2636 failed_to_evac = rtsFalse;
2640 case SE_CAF_BLACKHOLE:
2648 StgBlockingQueue *bh = (StgBlockingQueue *)p;
2649 (StgClosure *)bh->blocking_queue =
2650 evacuate((StgClosure *)bh->blocking_queue);
2651 failed_to_evac = rtsFalse;
2655 case THUNK_SELECTOR:
2657 StgSelector *s = (StgSelector *)p;
2658 s->selectee = evacuate(s->selectee);
2662 case AP_UPD: // same as PAPs
2664 /* Treat a PAP just like a section of stack, not forgetting to
2665 * evacuate the function pointer too...
2668 StgPAP* pap = (StgPAP *)p;
2670 pap->fun = evacuate(pap->fun);
2671 scavenge_stack((P_)pap->payload, (P_)pap->payload + pap->n_args);
2676 // follow everything
2680 evac_gen = 0; // repeatedly mutable
2681 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2682 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2683 (StgClosure *)*p = evacuate((StgClosure *)*p);
2685 evac_gen = saved_evac_gen;
2686 failed_to_evac = rtsFalse; // mutable anyhow.
2690 case MUT_ARR_PTRS_FROZEN:
2691 // follow everything
2695 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2696 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2697 (StgClosure *)*p = evacuate((StgClosure *)*p);
2704 StgTSO *tso = (StgTSO *)p;
2707 evac_gen = saved_evac_gen;
2708 failed_to_evac = rtsFalse;
2713 case RBH: // cf. BLACKHOLE_BQ
2716 nat size, ptrs, nonptrs, vhs;
2718 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2720 StgRBH *rbh = (StgRBH *)p;
2721 (StgClosure *)rbh->blocking_queue =
2722 evacuate((StgClosure *)rbh->blocking_queue);
2723 recordMutable((StgMutClosure *)rbh);
2724 failed_to_evac = rtsFalse; // mutable anyhow.
2726 belch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2727 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2733 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2734 // follow the pointer to the node which is being demanded
2735 (StgClosure *)bf->node =
2736 evacuate((StgClosure *)bf->node);
2737 // follow the link to the rest of the blocking queue
2738 (StgClosure *)bf->link =
2739 evacuate((StgClosure *)bf->link);
2740 if (failed_to_evac) {
2741 failed_to_evac = rtsFalse;
2742 recordMutable((StgMutClosure *)bf);
2745 belch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
2746 bf, info_type((StgClosure *)bf),
2747 bf->node, info_type(bf->node)));
2755 break; // nothing to do in this case
2757 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
2759 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
2760 (StgClosure *)fmbq->blocking_queue =
2761 evacuate((StgClosure *)fmbq->blocking_queue);
2762 if (failed_to_evac) {
2763 failed_to_evac = rtsFalse;
2764 recordMutable((StgMutClosure *)fmbq);
2767 belch("@@ scavenge: %p (%s) exciting, isn't it",
2768 p, info_type((StgClosure *)p)));
2774 barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p",
2778 if (failed_to_evac) {
2779 failed_to_evac = rtsFalse;
2780 mkMutCons((StgClosure *)q, &generations[evac_gen]);
2783 // mark the next bit to indicate "scavenged"
2784 mark(q+1, Bdescr(q));
2786 } // while (!mark_stack_empty())
2788 // start a new linear scan if the mark stack overflowed at some point
2789 if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
2790 IF_DEBUG(gc, belch("scavenge_mark_stack: starting linear scan"));
2791 mark_stack_overflowed = rtsFalse;
2792 oldgen_scan_bd = oldest_gen->steps[0].blocks;
2793 oldgen_scan = oldgen_scan_bd->start;
2796 if (oldgen_scan_bd) {
2797 // push a new thing on the mark stack
2799 // find a closure that is marked but not scavenged, and start
2801 while (oldgen_scan < oldgen_scan_bd->free
2802 && !is_marked(oldgen_scan,oldgen_scan_bd)) {
2806 if (oldgen_scan < oldgen_scan_bd->free) {
2808 // already scavenged?
2809 if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
2810 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
2813 push_mark_stack(oldgen_scan);
2814 // ToDo: bump the linear scan by the actual size of the object
2815 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
2819 oldgen_scan_bd = oldgen_scan_bd->link;
2820 if (oldgen_scan_bd != NULL) {
2821 oldgen_scan = oldgen_scan_bd->start;
2827 /* -----------------------------------------------------------------------------
2828 Scavenge one object.
2830 This is used for objects that are temporarily marked as mutable
2831 because they contain old-to-new generation pointers. Only certain
2832 objects can have this property.
2833 -------------------------------------------------------------------------- */
2836 scavenge_one(StgPtr p)
2838 const StgInfoTable *info;
2839 nat saved_evac_gen = evac_gen;
2842 ASSERT(p && (LOOKS_LIKE_GHC_INFO(GET_INFO((StgClosure *)p))
2843 || IS_HUGS_CONSTR_INFO(GET_INFO((StgClosure *)p))));
2845 info = get_itbl((StgClosure *)p);
2847 switch (info->type) {
2850 case FUN_1_0: // hardly worth specialising these guys
2870 case IND_OLDGEN_PERM:
2874 end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2875 for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
2876 (StgClosure *)*q = evacuate((StgClosure *)*q);
2882 case SE_CAF_BLACKHOLE:
2887 case THUNK_SELECTOR:
2889 StgSelector *s = (StgSelector *)p;
2890 s->selectee = evacuate(s->selectee);
2895 // nothing to follow
2900 // follow everything
2903 evac_gen = 0; // repeatedly mutable
2904 recordMutable((StgMutClosure *)p);
2905 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2906 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2907 (StgClosure *)*p = evacuate((StgClosure *)*p);
2909 evac_gen = saved_evac_gen;
2910 failed_to_evac = rtsFalse;
2914 case MUT_ARR_PTRS_FROZEN:
2916 // follow everything
2919 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2920 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2921 (StgClosure *)*p = evacuate((StgClosure *)*p);
2928 StgTSO *tso = (StgTSO *)p;
2930 evac_gen = 0; // repeatedly mutable
2932 recordMutable((StgMutClosure *)tso);
2933 evac_gen = saved_evac_gen;
2934 failed_to_evac = rtsFalse;
2941 StgPAP* pap = (StgPAP *)p;
2942 pap->fun = evacuate(pap->fun);
2943 scavenge_stack((P_)pap->payload, (P_)pap->payload + pap->n_args);
2948 // This might happen if for instance a MUT_CONS was pointing to a
2949 // THUNK which has since been updated. The IND_OLDGEN will
2950 // be on the mutable list anyway, so we don't need to do anything
2955 barf("scavenge_one: strange object %d", (int)(info->type));
2958 no_luck = failed_to_evac;
2959 failed_to_evac = rtsFalse;
2963 /* -----------------------------------------------------------------------------
2964 Scavenging mutable lists.
2966 We treat the mutable list of each generation > N (i.e. all the
2967 generations older than the one being collected) as roots. We also
2968 remove non-mutable objects from the mutable list at this point.
2969 -------------------------------------------------------------------------- */
2972 scavenge_mut_once_list(generation *gen)
2974 const StgInfoTable *info;
2975 StgMutClosure *p, *next, *new_list;
2977 p = gen->mut_once_list;
2978 new_list = END_MUT_LIST;
2982 failed_to_evac = rtsFalse;
2984 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
2986 // make sure the info pointer is into text space
2987 ASSERT(p && (LOOKS_LIKE_GHC_INFO(GET_INFO(p))
2988 || IS_HUGS_CONSTR_INFO(GET_INFO(p))));
2992 if (info->type==RBH)
2993 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
2995 switch(info->type) {
2998 case IND_OLDGEN_PERM:
3000 /* Try to pull the indirectee into this generation, so we can
3001 * remove the indirection from the mutable list.
3003 ((StgIndOldGen *)p)->indirectee =
3004 evacuate(((StgIndOldGen *)p)->indirectee);
3006 #if 0 && defined(DEBUG)
3007 if (RtsFlags.DebugFlags.gc)
3008 /* Debugging code to print out the size of the thing we just
3012 StgPtr start = gen->steps[0].scan;
3013 bdescr *start_bd = gen->steps[0].scan_bd;
3015 scavenge(&gen->steps[0]);
3016 if (start_bd != gen->steps[0].scan_bd) {
3017 size += (P_)BLOCK_ROUND_UP(start) - start;
3018 start_bd = start_bd->link;
3019 while (start_bd != gen->steps[0].scan_bd) {
3020 size += BLOCK_SIZE_W;
3021 start_bd = start_bd->link;
3023 size += gen->steps[0].scan -
3024 (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
3026 size = gen->steps[0].scan - start;
3028 belch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
3032 /* failed_to_evac might happen if we've got more than two
3033 * generations, we're collecting only generation 0, the
3034 * indirection resides in generation 2 and the indirectee is
3037 if (failed_to_evac) {
3038 failed_to_evac = rtsFalse;
3039 p->mut_link = new_list;
3042 /* the mut_link field of an IND_STATIC is overloaded as the
3043 * static link field too (it just so happens that we don't need
3044 * both at the same time), so we need to NULL it out when
3045 * removing this object from the mutable list because the static
3046 * link fields are all assumed to be NULL before doing a major
3054 /* MUT_CONS is a kind of MUT_VAR, except it that we try to remove
3055 * it from the mutable list if possible by promoting whatever it
3058 if (scavenge_one((StgPtr)((StgMutVar *)p)->var)) {
3059 /* didn't manage to promote everything, so put the
3060 * MUT_CONS back on the list.
3062 p->mut_link = new_list;
3068 // shouldn't have anything else on the mutables list
3069 barf("scavenge_mut_once_list: strange object? %d", (int)(info->type));
3073 gen->mut_once_list = new_list;
3078 scavenge_mutable_list(generation *gen)
3080 const StgInfoTable *info;
3081 StgMutClosure *p, *next;
3083 p = gen->saved_mut_list;
3087 failed_to_evac = rtsFalse;
3089 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
3091 // make sure the info pointer is into text space
3092 ASSERT(p && (LOOKS_LIKE_GHC_INFO(GET_INFO(p))
3093 || IS_HUGS_CONSTR_INFO(GET_INFO(p))));
3097 if (info->type==RBH)
3098 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3100 switch(info->type) {
3103 // follow everything
3104 p->mut_link = gen->mut_list;
3109 end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3110 for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
3111 (StgClosure *)*q = evacuate((StgClosure *)*q);
3116 // Happens if a MUT_ARR_PTRS in the old generation is frozen
3117 case MUT_ARR_PTRS_FROZEN:
3122 end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3123 for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
3124 (StgClosure *)*q = evacuate((StgClosure *)*q);
3128 if (failed_to_evac) {
3129 failed_to_evac = rtsFalse;
3130 mkMutCons((StgClosure *)p, gen);
3136 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3137 p->mut_link = gen->mut_list;
3143 StgMVar *mvar = (StgMVar *)p;
3144 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
3145 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
3146 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
3147 p->mut_link = gen->mut_list;
3154 StgTSO *tso = (StgTSO *)p;
3158 /* Don't take this TSO off the mutable list - it might still
3159 * point to some younger objects (because we set evac_gen to 0
3162 tso->mut_link = gen->mut_list;
3163 gen->mut_list = (StgMutClosure *)tso;
3169 StgBlockingQueue *bh = (StgBlockingQueue *)p;
3170 (StgClosure *)bh->blocking_queue =
3171 evacuate((StgClosure *)bh->blocking_queue);
3172 p->mut_link = gen->mut_list;
3177 /* Happens if a BLACKHOLE_BQ in the old generation is updated:
3180 case IND_OLDGEN_PERM:
3181 /* Try to pull the indirectee into this generation, so we can
3182 * remove the indirection from the mutable list.
3185 ((StgIndOldGen *)p)->indirectee =
3186 evacuate(((StgIndOldGen *)p)->indirectee);
3189 if (failed_to_evac) {
3190 failed_to_evac = rtsFalse;
3191 p->mut_link = gen->mut_once_list;
3192 gen->mut_once_list = p;
3199 // HWL: check whether all of these are necessary
3201 case RBH: // cf. BLACKHOLE_BQ
3203 // nat size, ptrs, nonptrs, vhs;
3205 // StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3206 StgRBH *rbh = (StgRBH *)p;
3207 (StgClosure *)rbh->blocking_queue =
3208 evacuate((StgClosure *)rbh->blocking_queue);
3209 if (failed_to_evac) {
3210 failed_to_evac = rtsFalse;
3211 recordMutable((StgMutClosure *)rbh);
3213 // ToDo: use size of reverted closure here!
3214 p += BLACKHOLE_sizeW();
3220 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3221 // follow the pointer to the node which is being demanded
3222 (StgClosure *)bf->node =
3223 evacuate((StgClosure *)bf->node);
3224 // follow the link to the rest of the blocking queue
3225 (StgClosure *)bf->link =
3226 evacuate((StgClosure *)bf->link);
3227 if (failed_to_evac) {
3228 failed_to_evac = rtsFalse;
3229 recordMutable((StgMutClosure *)bf);
3231 p += sizeofW(StgBlockedFetch);
3237 barf("scavenge_mutable_list: REMOTE_REF %d", (int)(info->type));
3240 p += sizeofW(StgFetchMe);
3241 break; // nothing to do in this case
3243 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
3245 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3246 (StgClosure *)fmbq->blocking_queue =
3247 evacuate((StgClosure *)fmbq->blocking_queue);
3248 if (failed_to_evac) {
3249 failed_to_evac = rtsFalse;
3250 recordMutable((StgMutClosure *)fmbq);
3252 p += sizeofW(StgFetchMeBlockingQueue);
3258 // shouldn't have anything else on the mutables list
3259 barf("scavenge_mutable_list: strange object? %d", (int)(info->type));
3266 scavenge_static(void)
3268 StgClosure* p = static_objects;
3269 const StgInfoTable *info;
3271 /* Always evacuate straight to the oldest generation for static
3273 evac_gen = oldest_gen->no;
3275 /* keep going until we've scavenged all the objects on the linked
3277 while (p != END_OF_STATIC_LIST) {
3281 if (info->type==RBH)
3282 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3284 // make sure the info pointer is into text space
3285 ASSERT(p && (LOOKS_LIKE_GHC_INFO(GET_INFO(p))
3286 || IS_HUGS_CONSTR_INFO(GET_INFO(p))));
3288 /* Take this object *off* the static_objects list,
3289 * and put it on the scavenged_static_objects list.
3291 static_objects = STATIC_LINK(info,p);
3292 STATIC_LINK(info,p) = scavenged_static_objects;
3293 scavenged_static_objects = p;
3295 switch (info -> type) {
3299 StgInd *ind = (StgInd *)p;
3300 ind->indirectee = evacuate(ind->indirectee);
3302 /* might fail to evacuate it, in which case we have to pop it
3303 * back on the mutable list (and take it off the
3304 * scavenged_static list because the static link and mut link
3305 * pointers are one and the same).
3307 if (failed_to_evac) {
3308 failed_to_evac = rtsFalse;
3309 scavenged_static_objects = IND_STATIC_LINK(p);
3310 ((StgMutClosure *)ind)->mut_link = oldest_gen->mut_once_list;
3311 oldest_gen->mut_once_list = (StgMutClosure *)ind;
3325 next = (P_)p->payload + info->layout.payload.ptrs;
3326 // evacuate the pointers
3327 for (q = (P_)p->payload; q < next; q++) {
3328 (StgClosure *)*q = evacuate((StgClosure *)*q);
3334 barf("scavenge_static: strange closure %d", (int)(info->type));
3337 ASSERT(failed_to_evac == rtsFalse);
3339 /* get the next static object from the list. Remember, there might
3340 * be more stuff on this list now that we've done some evacuating!
3341 * (static_objects is a global)
3347 /* -----------------------------------------------------------------------------
3348 scavenge_stack walks over a section of stack and evacuates all the
3349 objects pointed to by it. We can use the same code for walking
3350 PAPs, since these are just sections of copied stack.
3351 -------------------------------------------------------------------------- */
3354 scavenge_stack(StgPtr p, StgPtr stack_end)
3357 const StgInfoTable* info;
3360 //IF_DEBUG(sanity, belch(" scavenging stack between %p and %p", p, stack_end));
3363 * Each time around this loop, we are looking at a chunk of stack
3364 * that starts with either a pending argument section or an
3365 * activation record.
3368 while (p < stack_end) {
3371 // If we've got a tag, skip over that many words on the stack
3372 if (IS_ARG_TAG((W_)q)) {
3377 /* Is q a pointer to a closure?
3379 if (! LOOKS_LIKE_GHC_INFO(q) ) {
3381 if ( 0 && LOOKS_LIKE_STATIC_CLOSURE(q) ) { // Is it a static closure?
3382 ASSERT(closure_STATIC((StgClosure *)q));
3384 // otherwise, must be a pointer into the allocation space.
3387 (StgClosure *)*p = evacuate((StgClosure *)q);
3393 * Otherwise, q must be the info pointer of an activation
3394 * record. All activation records have 'bitmap' style layout
3397 info = get_itbl((StgClosure *)p);
3399 switch (info->type) {
3401 // Dynamic bitmap: the mask is stored on the stack
3403 bitmap = ((StgRetDyn *)p)->liveness;
3404 p = (P_)&((StgRetDyn *)p)->payload[0];
3407 // probably a slow-entry point return address:
3415 belch("HWL: scavenge_stack: FUN(_STATIC) adjusting p from %p to %p (instead of %p)",
3416 old_p, p, old_p+1));
3418 p++; // what if FHS!=1 !? -- HWL
3423 /* Specialised code for update frames, since they're so common.
3424 * We *know* the updatee points to a BLACKHOLE, CAF_BLACKHOLE,
3425 * or BLACKHOLE_BQ, so just inline the code to evacuate it here.
3429 StgUpdateFrame *frame = (StgUpdateFrame *)p;
3431 p += sizeofW(StgUpdateFrame);
3434 frame->updatee = evacuate(frame->updatee);
3436 #else // specialised code for update frames, not sure if it's worth it.
3438 nat type = get_itbl(frame->updatee)->type;
3440 if (type == EVACUATED) {
3441 frame->updatee = evacuate(frame->updatee);
3444 bdescr *bd = Bdescr((P_)frame->updatee);
3446 if (bd->gen_no > N) {
3447 if (bd->gen_no < evac_gen) {
3448 failed_to_evac = rtsTrue;
3453 // Don't promote blackholes
3455 if (!(stp->gen_no == 0 &&
3457 stp->no == stp->gen->n_steps-1)) {
3464 to = copyPart(frame->updatee, BLACKHOLE_sizeW(),
3465 sizeofW(StgHeader), stp);
3466 frame->updatee = to;
3469 to = copy(frame->updatee, BLACKHOLE_sizeW(), stp);
3470 frame->updatee = to;
3471 recordMutable((StgMutClosure *)to);
3474 /* will never be SE_{,CAF_}BLACKHOLE, since we
3475 don't push an update frame for single-entry thunks. KSW 1999-01. */
3476 barf("scavenge_stack: UPDATE_FRAME updatee");
3482 // small bitmap (< 32 entries, or 64 on a 64-bit machine)
3489 bitmap = info->layout.bitmap;
3491 // this assumes that the payload starts immediately after the info-ptr
3493 while (bitmap != 0) {
3494 if ((bitmap & 1) == 0) {
3495 (StgClosure *)*p = evacuate((StgClosure *)*p);
3498 bitmap = bitmap >> 1;
3505 // large bitmap (> 32 entries, or > 64 on a 64-bit machine)
3510 StgLargeBitmap *large_bitmap;
3513 large_bitmap = info->layout.large_bitmap;
3516 for (i=0; i<large_bitmap->size; i++) {
3517 bitmap = large_bitmap->bitmap[i];
3518 q = p + BITS_IN(W_);
3519 while (bitmap != 0) {
3520 if ((bitmap & 1) == 0) {
3521 (StgClosure *)*p = evacuate((StgClosure *)*p);
3524 bitmap = bitmap >> 1;
3526 if (i+1 < large_bitmap->size) {
3528 (StgClosure *)*p = evacuate((StgClosure *)*p);
3534 // and don't forget to follow the SRT
3539 barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->type));
3544 /*-----------------------------------------------------------------------------
3545 scavenge the large object list.
3547 evac_gen set by caller; similar games played with evac_gen as with
3548 scavenge() - see comment at the top of scavenge(). Most large
3549 objects are (repeatedly) mutable, so most of the time evac_gen will
3551 --------------------------------------------------------------------------- */
3554 scavenge_large(step *stp)
3559 bd = stp->new_large_objects;
3561 for (; bd != NULL; bd = stp->new_large_objects) {
3563 /* take this object *off* the large objects list and put it on
3564 * the scavenged large objects list. This is so that we can
3565 * treat new_large_objects as a stack and push new objects on
3566 * the front when evacuating.
3568 stp->new_large_objects = bd->link;
3569 dbl_link_onto(bd, &stp->scavenged_large_objects);
3571 // update the block count in this step.
3572 stp->n_scavenged_large_blocks += bd->blocks;
3575 if (scavenge_one(p)) {
3576 mkMutCons((StgClosure *)p, stp->gen);
3581 /* -----------------------------------------------------------------------------
3582 Initialising the static object & mutable lists
3583 -------------------------------------------------------------------------- */
3586 zero_static_object_list(StgClosure* first_static)
3590 const StgInfoTable *info;
3592 for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
3594 link = STATIC_LINK(info, p);
3595 STATIC_LINK(info,p) = NULL;
3599 /* This function is only needed because we share the mutable link
3600 * field with the static link field in an IND_STATIC, so we have to
3601 * zero the mut_link field before doing a major GC, which needs the
3602 * static link field.
3604 * It doesn't do any harm to zero all the mutable link fields on the
3609 zero_mutable_list( StgMutClosure *first )
3611 StgMutClosure *next, *c;
3613 for (c = first; c != END_MUT_LIST; c = next) {
3619 /* -----------------------------------------------------------------------------
3621 -------------------------------------------------------------------------- */
3628 for (c = (StgIndStatic *)caf_list; c != NULL;
3629 c = (StgIndStatic *)c->static_link)
3631 c->header.info = c->saved_info;
3632 c->saved_info = NULL;
3633 // could, but not necessary: c->static_link = NULL;
3639 markCAFs( evac_fn evac )
3643 for (c = (StgIndStatic *)caf_list; c != NULL;
3644 c = (StgIndStatic *)c->static_link)
3646 evac(&c->indirectee);
3650 /* -----------------------------------------------------------------------------
3651 Sanity code for CAF garbage collection.
3653 With DEBUG turned on, we manage a CAF list in addition to the SRT
3654 mechanism. After GC, we run down the CAF list and blackhole any
3655 CAFs which have been garbage collected. This means we get an error
3656 whenever the program tries to enter a garbage collected CAF.
3658 Any garbage collected CAFs are taken off the CAF list at the same
3660 -------------------------------------------------------------------------- */
3662 #if 0 && defined(DEBUG)
3669 const StgInfoTable *info;
3680 ASSERT(info->type == IND_STATIC);
3682 if (STATIC_LINK(info,p) == NULL) {
3683 IF_DEBUG(gccafs, belch("CAF gc'd at 0x%04lx", (long)p));
3685 SET_INFO(p,&stg_BLACKHOLE_info);
3686 p = STATIC_LINK2(info,p);
3690 pp = &STATIC_LINK2(info,p);
3697 // belch("%d CAFs live", i);
3702 /* -----------------------------------------------------------------------------
3705 Whenever a thread returns to the scheduler after possibly doing
3706 some work, we have to run down the stack and black-hole all the
3707 closures referred to by update frames.
3708 -------------------------------------------------------------------------- */
3711 threadLazyBlackHole(StgTSO *tso)
3713 StgUpdateFrame *update_frame;
3714 StgBlockingQueue *bh;
3717 stack_end = &tso->stack[tso->stack_size];
3718 update_frame = tso->su;
3721 switch (get_itbl(update_frame)->type) {
3724 update_frame = ((StgCatchFrame *)update_frame)->link;
3728 bh = (StgBlockingQueue *)update_frame->updatee;
3730 /* if the thunk is already blackholed, it means we've also
3731 * already blackholed the rest of the thunks on this stack,
3732 * so we can stop early.
3734 * The blackhole made for a CAF is a CAF_BLACKHOLE, so they
3735 * don't interfere with this optimisation.
3737 if (bh->header.info == &stg_BLACKHOLE_info) {
3741 if (bh->header.info != &stg_BLACKHOLE_BQ_info &&
3742 bh->header.info != &stg_CAF_BLACKHOLE_info) {
3743 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
3744 belch("Unexpected lazy BHing required at 0x%04x",(int)bh);
3748 // We pretend that bh is now dead.
3749 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
3751 SET_INFO(bh,&stg_BLACKHOLE_info);
3754 // We pretend that bh has just been created.
3755 LDV_recordCreate(bh);
3759 update_frame = update_frame->link;
3763 update_frame = ((StgSeqFrame *)update_frame)->link;
3769 barf("threadPaused");
3775 /* -----------------------------------------------------------------------------
3778 * Code largely pinched from old RTS, then hacked to bits. We also do
3779 * lazy black holing here.
3781 * -------------------------------------------------------------------------- */
3784 threadSqueezeStack(StgTSO *tso)
3786 lnat displacement = 0;
3787 StgUpdateFrame *frame;
3788 StgUpdateFrame *next_frame; // Temporally next
3789 StgUpdateFrame *prev_frame; // Temporally previous
3791 rtsBool prev_was_update_frame;
3793 StgUpdateFrame *top_frame;
3794 nat upd_frames=0, stop_frames=0, catch_frames=0, seq_frames=0,
3796 void printObj( StgClosure *obj ); // from Printer.c
3798 top_frame = tso->su;
3801 bottom = &(tso->stack[tso->stack_size]);
3804 /* There must be at least one frame, namely the STOP_FRAME.
3806 ASSERT((P_)frame < bottom);
3808 /* Walk down the stack, reversing the links between frames so that
3809 * we can walk back up as we squeeze from the bottom. Note that
3810 * next_frame and prev_frame refer to next and previous as they were
3811 * added to the stack, rather than the way we see them in this
3812 * walk. (It makes the next loop less confusing.)
3814 * Stop if we find an update frame pointing to a black hole
3815 * (see comment in threadLazyBlackHole()).
3819 // bottom - sizeof(StgStopFrame) is the STOP_FRAME
3820 while ((P_)frame < bottom - sizeofW(StgStopFrame)) {
3821 prev_frame = frame->link;
3822 frame->link = next_frame;
3827 if (!(frame>=top_frame && frame<=(StgUpdateFrame *)bottom)) {
3828 printObj((StgClosure *)prev_frame);
3829 barf("threadSqueezeStack: current frame is rubbish %p; previous was %p\n",
3832 switch (get_itbl(frame)->type) {
3835 if (frame->updatee->header.info == &stg_BLACKHOLE_info)
3848 barf("Found non-frame during stack squeezing at %p (prev frame was %p)\n",
3850 printObj((StgClosure *)prev_frame);
3853 if (get_itbl(frame)->type == UPDATE_FRAME
3854 && frame->updatee->header.info == &stg_BLACKHOLE_info) {
3859 /* Now, we're at the bottom. Frame points to the lowest update
3860 * frame on the stack, and its link actually points to the frame
3861 * above. We have to walk back up the stack, squeezing out empty
3862 * update frames and turning the pointers back around on the way
3865 * The bottom-most frame (the STOP_FRAME) has not been altered, and
3866 * we never want to eliminate it anyway. Just walk one step up
3867 * before starting to squeeze. When you get to the topmost frame,
3868 * remember that there are still some words above it that might have
3875 prev_was_update_frame = (get_itbl(prev_frame)->type == UPDATE_FRAME);
3878 * Loop through all of the frames (everything except the very
3879 * bottom). Things are complicated by the fact that we have
3880 * CATCH_FRAMEs and SEQ_FRAMEs interspersed with the update frames.
3881 * We can only squeeze when there are two consecutive UPDATE_FRAMEs.
3883 while (frame != NULL) {
3885 StgPtr frame_bottom = (P_)frame + sizeofW(StgUpdateFrame);
3886 rtsBool is_update_frame;
3888 next_frame = frame->link;
3889 is_update_frame = (get_itbl(frame)->type == UPDATE_FRAME);
3892 * 1. both the previous and current frame are update frames
3893 * 2. the current frame is empty
3895 if (prev_was_update_frame && is_update_frame &&
3896 (P_)prev_frame == frame_bottom + displacement) {
3898 // Now squeeze out the current frame
3899 StgClosure *updatee_keep = prev_frame->updatee;
3900 StgClosure *updatee_bypass = frame->updatee;
3903 IF_DEBUG(gc, belch("@@ squeezing frame at %p", frame));
3907 /* Deal with blocking queues. If both updatees have blocked
3908 * threads, then we should merge the queues into the update
3909 * frame that we're keeping.
3911 * Alternatively, we could just wake them up: they'll just go
3912 * straight to sleep on the proper blackhole! This is less code
3913 * and probably less bug prone, although it's probably much
3916 #if 0 // do it properly...
3917 # if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
3918 # error Unimplemented lazy BH warning. (KSW 1999-01)
3920 if (GET_INFO(updatee_bypass) == stg_BLACKHOLE_BQ_info
3921 || GET_INFO(updatee_bypass) == stg_CAF_BLACKHOLE_info
3923 // Sigh. It has one. Don't lose those threads!
3924 if (GET_INFO(updatee_keep) == stg_BLACKHOLE_BQ_info) {
3925 // Urgh. Two queues. Merge them.
3926 P_ keep_tso = ((StgBlockingQueue *)updatee_keep)->blocking_queue;
3928 while (keep_tso->link != END_TSO_QUEUE) {
3929 keep_tso = keep_tso->link;
3931 keep_tso->link = ((StgBlockingQueue *)updatee_bypass)->blocking_queue;
3934 // For simplicity, just swap the BQ for the BH
3935 P_ temp = updatee_keep;
3937 updatee_keep = updatee_bypass;
3938 updatee_bypass = temp;
3940 // Record the swap in the kept frame (below)
3941 prev_frame->updatee = updatee_keep;
3946 TICK_UPD_SQUEEZED();
3947 /* wasn't there something about update squeezing and ticky to be
3948 * sorted out? oh yes: we aren't counting each enter properly
3949 * in this case. See the log somewhere. KSW 1999-04-21
3951 * Check two things: that the two update frames don't point to
3952 * the same object, and that the updatee_bypass isn't already an
3953 * indirection. Both of these cases only happen when we're in a
3954 * block hole-style loop (and there are multiple update frames
3955 * on the stack pointing to the same closure), but they can both
3956 * screw us up if we don't check.
3958 if (updatee_bypass != updatee_keep && !closure_IND(updatee_bypass)) {
3959 // this wakes the threads up
3960 UPD_IND_NOLOCK(updatee_bypass, updatee_keep);
3963 sp = (P_)frame - 1; // sp = stuff to slide
3964 displacement += sizeofW(StgUpdateFrame);
3967 // No squeeze for this frame
3968 sp = frame_bottom - 1; // Keep the current frame
3970 /* Do lazy black-holing.
3972 if (is_update_frame) {
3973 StgBlockingQueue *bh = (StgBlockingQueue *)frame->updatee;
3974 if (bh->header.info != &stg_BLACKHOLE_info &&
3975 bh->header.info != &stg_BLACKHOLE_BQ_info &&
3976 bh->header.info != &stg_CAF_BLACKHOLE_info) {
3977 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
3978 belch("Unexpected lazy BHing required at 0x%04x",(int)bh);
3981 /* zero out the slop so that the sanity checker can tell
3982 * where the next closure is.
3985 StgInfoTable *info = get_itbl(bh);
3986 nat np = info->layout.payload.ptrs, nw = info->layout.payload.nptrs, i;
3987 /* don't zero out slop for a THUNK_SELECTOR, because its layout
3988 * info is used for a different purpose, and it's exactly the
3989 * same size as a BLACKHOLE in any case.
3991 if (info->type != THUNK_SELECTOR) {
3992 for (i = np; i < np + nw; i++) {
3993 ((StgClosure *)bh)->payload[i] = 0;
4000 // We pretend that bh is now dead.
4001 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4004 // Todo: maybe use SET_HDR() and remove LDV_recordCreate()?
4006 SET_INFO(bh,&stg_BLACKHOLE_info);
4009 // We pretend that bh has just been created.
4010 LDV_recordCreate(bh);
4015 // Fix the link in the current frame (should point to the frame below)
4016 frame->link = prev_frame;
4017 prev_was_update_frame = is_update_frame;
4020 // Now slide all words from sp up to the next frame
4022 if (displacement > 0) {
4023 P_ next_frame_bottom;
4025 if (next_frame != NULL)
4026 next_frame_bottom = (P_)next_frame + sizeofW(StgUpdateFrame);
4028 next_frame_bottom = tso->sp - 1;
4032 belch("sliding [%p, %p] by %ld", sp, next_frame_bottom,
4036 while (sp >= next_frame_bottom) {
4037 sp[displacement] = *sp;
4041 (P_)prev_frame = (P_)frame + displacement;
4045 tso->sp += displacement;
4046 tso->su = prev_frame;
4049 belch("@@ threadSqueezeStack: squeezed %d update-frames; found %d BHs; found %d update-, %d stop-, %d catch, %d seq-frames",
4050 squeezes, bhs, upd_frames, stop_frames, catch_frames, seq_frames))
4055 /* -----------------------------------------------------------------------------
4058 * We have to prepare for GC - this means doing lazy black holing
4059 * here. We also take the opportunity to do stack squeezing if it's
4061 * -------------------------------------------------------------------------- */
4063 threadPaused(StgTSO *tso)
4065 if ( RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue )
4066 threadSqueezeStack(tso); // does black holing too
4068 threadLazyBlackHole(tso);
4071 /* -----------------------------------------------------------------------------
4073 * -------------------------------------------------------------------------- */
4077 printMutOnceList(generation *gen)
4079 StgMutClosure *p, *next;
4081 p = gen->mut_once_list;
4084 fprintf(stderr, "@@ Mut once list %p: ", gen->mut_once_list);
4085 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
4086 fprintf(stderr, "%p (%s), ",
4087 p, info_type((StgClosure *)p));
4089 fputc('\n', stderr);
4093 printMutableList(generation *gen)
4095 StgMutClosure *p, *next;
4100 fprintf(stderr, "@@ Mutable list %p: ", gen->mut_list);
4101 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
4102 fprintf(stderr, "%p (%s), ",
4103 p, info_type((StgClosure *)p));
4105 fputc('\n', stderr);
4108 static inline rtsBool
4109 maybeLarge(StgClosure *closure)
4111 StgInfoTable *info = get_itbl(closure);
4113 /* closure types that may be found on the new_large_objects list;
4114 see scavenge_large */
4115 return (info->type == MUT_ARR_PTRS ||
4116 info->type == MUT_ARR_PTRS_FROZEN ||
4117 info->type == TSO ||
4118 info->type == ARR_WORDS);