1 /* -----------------------------------------------------------------------------
2 * $Id: GC.c,v 1.133 2002/04/13 05:16:25 sof 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"
48 /* STATIC OBJECT LIST.
51 * We maintain a linked list of static objects that are still live.
52 * The requirements for this list are:
54 * - we need to scan the list while adding to it, in order to
55 * scavenge all the static objects (in the same way that
56 * breadth-first scavenging works for dynamic objects).
58 * - we need to be able to tell whether an object is already on
59 * the list, to break loops.
61 * Each static object has a "static link field", which we use for
62 * linking objects on to the list. We use a stack-type list, consing
63 * objects on the front as they are added (this means that the
64 * scavenge phase is depth-first, not breadth-first, but that
67 * A separate list is kept for objects that have been scavenged
68 * already - this is so that we can zero all the marks afterwards.
70 * An object is on the list if its static link field is non-zero; this
71 * means that we have to mark the end of the list with '1', not NULL.
73 * Extra notes for generational GC:
75 * Each generation has a static object list associated with it. When
76 * collecting generations up to N, we treat the static object lists
77 * from generations > N as roots.
79 * We build up a static object list while collecting generations 0..N,
80 * which is then appended to the static object list of generation N+1.
82 StgClosure* static_objects; // live static objects
83 StgClosure* scavenged_static_objects; // static objects scavenged so far
85 /* N is the oldest generation being collected, where the generations
86 * are numbered starting at 0. A major GC (indicated by the major_gc
87 * flag) is when we're collecting all generations. We only attempt to
88 * deal with static objects and GC CAFs when doing a major GC.
91 static rtsBool major_gc;
93 /* Youngest generation that objects should be evacuated to in
94 * evacuate(). (Logically an argument to evacuate, but it's static
95 * a lot of the time so we optimise it into a global variable).
101 StgWeak *old_weak_ptr_list; // also pending finaliser list
103 /* Which stage of processing various kinds of weak pointer are we at?
104 * (see traverse_weak_ptr_list() below for discussion).
106 typedef enum { WeakPtrs, WeakThreads, WeakDone } WeakStage;
107 static WeakStage weak_stage;
109 /* List of all threads during GC
111 static StgTSO *old_all_threads;
112 StgTSO *resurrected_threads;
114 /* Flag indicating failure to evacuate an object to the desired
117 static rtsBool failed_to_evac;
119 /* Old to-space (used for two-space collector only)
121 bdescr *old_to_blocks;
123 /* Data used for allocation area sizing.
125 lnat new_blocks; // blocks allocated during this GC
126 lnat g0s0_pcnt_kept = 30; // percentage of g0s0 live at last minor GC
128 /* Used to avoid long recursion due to selector thunks
130 lnat thunk_selector_depth = 0;
131 #define MAX_THUNK_SELECTOR_DEPTH 256
133 /* -----------------------------------------------------------------------------
134 Static function declarations
135 -------------------------------------------------------------------------- */
137 static void mark_root ( StgClosure **root );
138 static StgClosure * evacuate ( StgClosure *q );
139 static void zero_static_object_list ( StgClosure* first_static );
140 static void zero_mutable_list ( StgMutClosure *first );
142 static rtsBool traverse_weak_ptr_list ( void );
143 static void mark_weak_ptr_list ( StgWeak **list );
145 static void scavenge ( step * );
146 static void scavenge_mark_stack ( void );
147 static void scavenge_stack ( StgPtr p, StgPtr stack_end );
148 static rtsBool scavenge_one ( StgPtr p );
149 static void scavenge_large ( step * );
150 static void scavenge_static ( void );
151 static void scavenge_mutable_list ( generation *g );
152 static void scavenge_mut_once_list ( generation *g );
154 #if 0 && defined(DEBUG)
155 static void gcCAFs ( void );
158 /* -----------------------------------------------------------------------------
159 inline functions etc. for dealing with the mark bitmap & stack.
160 -------------------------------------------------------------------------- */
162 #define MARK_STACK_BLOCKS 4
164 static bdescr *mark_stack_bdescr;
165 static StgPtr *mark_stack;
166 static StgPtr *mark_sp;
167 static StgPtr *mark_splim;
169 // Flag and pointers used for falling back to a linear scan when the
170 // mark stack overflows.
171 static rtsBool mark_stack_overflowed;
172 static bdescr *oldgen_scan_bd;
173 static StgPtr oldgen_scan;
175 static inline rtsBool
176 mark_stack_empty(void)
178 return mark_sp == mark_stack;
181 static inline rtsBool
182 mark_stack_full(void)
184 return mark_sp >= mark_splim;
188 reset_mark_stack(void)
190 mark_sp = mark_stack;
194 push_mark_stack(StgPtr p)
205 /* -----------------------------------------------------------------------------
208 For garbage collecting generation N (and all younger generations):
210 - follow all pointers in the root set. the root set includes all
211 mutable objects in all steps in all generations.
213 - for each pointer, evacuate the object it points to into either
214 + to-space in the next higher step in that generation, if one exists,
215 + if the object's generation == N, then evacuate it to the next
216 generation if one exists, or else to-space in the current
218 + if the object's generation < N, then evacuate it to to-space
219 in the next generation.
221 - repeatedly scavenge to-space from each step in each generation
222 being collected until no more objects can be evacuated.
224 - free from-space in each step, and set from-space = to-space.
226 Locks held: sched_mutex
228 -------------------------------------------------------------------------- */
231 GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc )
235 lnat live, allocated, collected = 0, copied = 0;
236 lnat oldgen_saved_blocks = 0;
240 CostCentreStack *prev_CCS;
243 #if defined(DEBUG) && defined(GRAN)
244 IF_DEBUG(gc, belch("@@ Starting garbage collection at %ld (%lx)\n",
248 // tell the stats department that we've started a GC
251 // Init stats and print par specific (timing) info
252 PAR_TICKY_PAR_START();
254 // attribute any costs to CCS_GC
260 /* Approximate how much we allocated.
261 * Todo: only when generating stats?
263 allocated = calcAllocated();
265 /* Figure out which generation to collect
267 if (force_major_gc) {
268 N = RtsFlags.GcFlags.generations - 1;
272 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
273 if (generations[g].steps[0].n_blocks +
274 generations[g].steps[0].n_large_blocks
275 >= generations[g].max_blocks) {
279 major_gc = (N == RtsFlags.GcFlags.generations-1);
282 #ifdef RTS_GTK_FRONTPANEL
283 if (RtsFlags.GcFlags.frontpanel) {
284 updateFrontPanelBeforeGC(N);
288 // check stack sanity *before* GC (ToDo: check all threads)
290 // ToDo!: check sanity IF_DEBUG(sanity, checkTSOsSanity());
292 IF_DEBUG(sanity, checkFreeListSanity());
294 /* Initialise the static object lists
296 static_objects = END_OF_STATIC_LIST;
297 scavenged_static_objects = END_OF_STATIC_LIST;
299 /* zero the mutable list for the oldest generation (see comment by
300 * zero_mutable_list below).
303 zero_mutable_list(generations[RtsFlags.GcFlags.generations-1].mut_once_list);
306 /* Save the old to-space if we're doing a two-space collection
308 if (RtsFlags.GcFlags.generations == 1) {
309 old_to_blocks = g0s0->to_blocks;
310 g0s0->to_blocks = NULL;
313 /* Keep a count of how many new blocks we allocated during this GC
314 * (used for resizing the allocation area, later).
318 /* Initialise to-space in all the generations/steps that we're
321 for (g = 0; g <= N; g++) {
322 generations[g].mut_once_list = END_MUT_LIST;
323 generations[g].mut_list = END_MUT_LIST;
325 for (s = 0; s < generations[g].n_steps; s++) {
327 // generation 0, step 0 doesn't need to-space
328 if (g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1) {
332 /* Get a free block for to-space. Extra blocks will be chained on
336 stp = &generations[g].steps[s];
337 ASSERT(stp->gen_no == g);
338 ASSERT(stp->hp ? Bdescr(stp->hp)->step == stp : rtsTrue);
342 bd->flags = BF_EVACUATED; // it's a to-space block
344 stp->hpLim = stp->hp + BLOCK_SIZE_W;
347 stp->n_to_blocks = 1;
348 stp->scan = bd->start;
350 stp->new_large_objects = NULL;
351 stp->scavenged_large_objects = NULL;
352 stp->n_scavenged_large_blocks = 0;
354 // mark the large objects as not evacuated yet
355 for (bd = stp->large_objects; bd; bd = bd->link) {
356 bd->flags = BF_LARGE;
359 // for a compacted step, we need to allocate the bitmap
360 if (stp->is_compacted) {
361 nat bitmap_size; // in bytes
362 bdescr *bitmap_bdescr;
365 bitmap_size = stp->n_blocks * BLOCK_SIZE / (sizeof(W_)*BITS_PER_BYTE);
367 if (bitmap_size > 0) {
368 bitmap_bdescr = allocGroup((nat)BLOCK_ROUND_UP(bitmap_size)
370 stp->bitmap = bitmap_bdescr;
371 bitmap = bitmap_bdescr->start;
373 IF_DEBUG(gc, belch("bitmap_size: %d, bitmap: %p",
374 bitmap_size, bitmap););
376 // don't forget to fill it with zeros!
377 memset(bitmap, 0, bitmap_size);
379 // for each block in this step, point to its bitmap from the
381 for (bd=stp->blocks; bd != NULL; bd = bd->link) {
382 bd->u.bitmap = bitmap;
383 bitmap += BLOCK_SIZE_W / (sizeof(W_)*BITS_PER_BYTE);
390 /* make sure the older generations have at least one block to
391 * allocate into (this makes things easier for copy(), see below.
393 for (g = N+1; g < RtsFlags.GcFlags.generations; g++) {
394 for (s = 0; s < generations[g].n_steps; s++) {
395 stp = &generations[g].steps[s];
396 if (stp->hp_bd == NULL) {
397 ASSERT(stp->blocks == NULL);
402 bd->flags = 0; // *not* a to-space block or a large object
404 stp->hpLim = stp->hp + BLOCK_SIZE_W;
410 /* Set the scan pointer for older generations: remember we
411 * still have to scavenge objects that have been promoted. */
413 stp->scan_bd = stp->hp_bd;
414 stp->to_blocks = NULL;
415 stp->n_to_blocks = 0;
416 stp->new_large_objects = NULL;
417 stp->scavenged_large_objects = NULL;
418 stp->n_scavenged_large_blocks = 0;
422 /* Allocate a mark stack if we're doing a major collection.
425 mark_stack_bdescr = allocGroup(MARK_STACK_BLOCKS);
426 mark_stack = (StgPtr *)mark_stack_bdescr->start;
427 mark_sp = mark_stack;
428 mark_splim = mark_stack + (MARK_STACK_BLOCKS * BLOCK_SIZE_W);
430 mark_stack_bdescr = NULL;
433 /* -----------------------------------------------------------------------
434 * follow all the roots that we know about:
435 * - mutable lists from each generation > N
436 * we want to *scavenge* these roots, not evacuate them: they're not
437 * going to move in this GC.
438 * Also: do them in reverse generation order. This is because we
439 * often want to promote objects that are pointed to by older
440 * generations early, so we don't have to repeatedly copy them.
441 * Doing the generations in reverse order ensures that we don't end
442 * up in the situation where we want to evac an object to gen 3 and
443 * it has already been evaced to gen 2.
447 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
448 generations[g].saved_mut_list = generations[g].mut_list;
449 generations[g].mut_list = END_MUT_LIST;
452 // Do the mut-once lists first
453 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
454 IF_PAR_DEBUG(verbose,
455 printMutOnceList(&generations[g]));
456 scavenge_mut_once_list(&generations[g]);
458 for (st = generations[g].n_steps-1; st >= 0; st--) {
459 scavenge(&generations[g].steps[st]);
463 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
464 IF_PAR_DEBUG(verbose,
465 printMutableList(&generations[g]));
466 scavenge_mutable_list(&generations[g]);
468 for (st = generations[g].n_steps-1; st >= 0; st--) {
469 scavenge(&generations[g].steps[st]);
474 /* follow roots from the CAF list (used by GHCi)
479 /* follow all the roots that the application knows about.
482 get_roots(mark_root);
485 /* And don't forget to mark the TSO if we got here direct from
487 /* Not needed in a seq version?
489 CurrentTSO = (StgTSO *)MarkRoot((StgClosure *)CurrentTSO);
493 // Mark the entries in the GALA table of the parallel system
494 markLocalGAs(major_gc);
495 // Mark all entries on the list of pending fetches
496 markPendingFetches(major_gc);
499 /* Mark the weak pointer list, and prepare to detect dead weak
502 mark_weak_ptr_list(&weak_ptr_list);
503 old_weak_ptr_list = weak_ptr_list;
504 weak_ptr_list = NULL;
505 weak_stage = WeakPtrs;
507 /* The all_threads list is like the weak_ptr_list.
508 * See traverse_weak_ptr_list() for the details.
510 old_all_threads = all_threads;
511 all_threads = END_TSO_QUEUE;
512 resurrected_threads = END_TSO_QUEUE;
514 /* Mark the stable pointer table.
516 markStablePtrTable(mark_root);
520 /* ToDo: To fix the caf leak, we need to make the commented out
521 * parts of this code do something sensible - as described in
524 extern void markHugsObjects(void);
529 /* -------------------------------------------------------------------------
530 * Repeatedly scavenge all the areas we know about until there's no
531 * more scavenging to be done.
538 // scavenge static objects
539 if (major_gc && static_objects != END_OF_STATIC_LIST) {
540 IF_DEBUG(sanity, checkStaticObjects(static_objects));
544 /* When scavenging the older generations: Objects may have been
545 * evacuated from generations <= N into older generations, and we
546 * need to scavenge these objects. We're going to try to ensure that
547 * any evacuations that occur move the objects into at least the
548 * same generation as the object being scavenged, otherwise we
549 * have to create new entries on the mutable list for the older
553 // scavenge each step in generations 0..maxgen
559 // scavenge objects in compacted generation
560 if (mark_stack_overflowed || oldgen_scan_bd != NULL ||
561 (mark_stack_bdescr != NULL && !mark_stack_empty())) {
562 scavenge_mark_stack();
566 for (gen = RtsFlags.GcFlags.generations; --gen >= 0; ) {
567 for (st = generations[gen].n_steps; --st >= 0; ) {
568 if (gen == 0 && st == 0 && RtsFlags.GcFlags.generations > 1) {
571 stp = &generations[gen].steps[st];
573 if (stp->hp_bd != stp->scan_bd || stp->scan < stp->hp) {
578 if (stp->new_large_objects != NULL) {
587 if (flag) { goto loop; }
589 // must be last... invariant is that everything is fully
590 // scavenged at this point.
591 if (traverse_weak_ptr_list()) { // returns rtsTrue if evaced something
596 /* Update the pointers from the "main thread" list - these are
597 * treated as weak pointers because we want to allow a main thread
598 * to get a BlockedOnDeadMVar exception in the same way as any other
599 * thread. Note that the threads should all have been retained by
600 * GC by virtue of being on the all_threads list, we're just
601 * updating pointers here.
606 for (m = main_threads; m != NULL; m = m->link) {
607 tso = (StgTSO *) isAlive((StgClosure *)m->tso);
609 barf("main thread has been GC'd");
616 // Reconstruct the Global Address tables used in GUM
617 rebuildGAtables(major_gc);
618 IF_DEBUG(sanity, checkLAGAtable(rtsTrue/*check closures, too*/));
621 // Now see which stable names are still alive.
624 // Tidy the end of the to-space chains
625 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
626 for (s = 0; s < generations[g].n_steps; s++) {
627 stp = &generations[g].steps[s];
628 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
629 stp->hp_bd->free = stp->hp;
630 stp->hp_bd->link = NULL;
636 // We call processHeapClosureForDead() on every closure destroyed during
637 // the current garbage collection, so we invoke LdvCensusForDead().
638 if (RtsFlags.ProfFlags.doHeapProfile == HEAP_BY_LDV
639 || RtsFlags.ProfFlags.bioSelector != NULL)
643 // NO MORE EVACUATION AFTER THIS POINT!
644 // Finally: compaction of the oldest generation.
645 if (major_gc && oldest_gen->steps[0].is_compacted) {
646 // save number of blocks for stats
647 oldgen_saved_blocks = oldest_gen->steps[0].n_blocks;
651 IF_DEBUG(sanity, checkGlobalTSOList(rtsFalse));
653 /* run through all the generations/steps and tidy up
655 copied = new_blocks * BLOCK_SIZE_W;
656 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
659 generations[g].collections++; // for stats
662 for (s = 0; s < generations[g].n_steps; s++) {
664 stp = &generations[g].steps[s];
666 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
667 // stats information: how much we copied
669 copied -= stp->hp_bd->start + BLOCK_SIZE_W -
674 // for generations we collected...
677 // rough calculation of garbage collected, for stats output
678 if (stp->is_compacted) {
679 collected += (oldgen_saved_blocks - stp->n_blocks) * BLOCK_SIZE_W;
681 collected += stp->n_blocks * BLOCK_SIZE_W;
684 /* free old memory and shift to-space into from-space for all
685 * the collected steps (except the allocation area). These
686 * freed blocks will probaby be quickly recycled.
688 if (!(g == 0 && s == 0)) {
689 if (stp->is_compacted) {
690 // for a compacted step, just shift the new to-space
691 // onto the front of the now-compacted existing blocks.
692 for (bd = stp->to_blocks; bd != NULL; bd = bd->link) {
693 bd->flags &= ~BF_EVACUATED; // now from-space
695 // tack the new blocks on the end of the existing blocks
696 if (stp->blocks == NULL) {
697 stp->blocks = stp->to_blocks;
699 for (bd = stp->blocks; bd != NULL; bd = next) {
702 bd->link = stp->to_blocks;
706 // add the new blocks to the block tally
707 stp->n_blocks += stp->n_to_blocks;
709 freeChain(stp->blocks);
710 stp->blocks = stp->to_blocks;
711 stp->n_blocks = stp->n_to_blocks;
712 for (bd = stp->blocks; bd != NULL; bd = bd->link) {
713 bd->flags &= ~BF_EVACUATED; // now from-space
716 stp->to_blocks = NULL;
717 stp->n_to_blocks = 0;
720 /* LARGE OBJECTS. The current live large objects are chained on
721 * scavenged_large, having been moved during garbage
722 * collection from large_objects. Any objects left on
723 * large_objects list are therefore dead, so we free them here.
725 for (bd = stp->large_objects; bd != NULL; bd = next) {
731 // update the count of blocks used by large objects
732 for (bd = stp->scavenged_large_objects; bd != NULL; bd = bd->link) {
733 bd->flags &= ~BF_EVACUATED;
735 stp->large_objects = stp->scavenged_large_objects;
736 stp->n_large_blocks = stp->n_scavenged_large_blocks;
739 // for older generations...
741 /* For older generations, we need to append the
742 * scavenged_large_object list (i.e. large objects that have been
743 * promoted during this GC) to the large_object list for that step.
745 for (bd = stp->scavenged_large_objects; bd; bd = next) {
747 bd->flags &= ~BF_EVACUATED;
748 dbl_link_onto(bd, &stp->large_objects);
751 // add the new blocks we promoted during this GC
752 stp->n_blocks += stp->n_to_blocks;
753 stp->n_large_blocks += stp->n_scavenged_large_blocks;
758 /* Reset the sizes of the older generations when we do a major
761 * CURRENT STRATEGY: make all generations except zero the same size.
762 * We have to stay within the maximum heap size, and leave a certain
763 * percentage of the maximum heap size available to allocate into.
765 if (major_gc && RtsFlags.GcFlags.generations > 1) {
766 nat live, size, min_alloc;
767 nat max = RtsFlags.GcFlags.maxHeapSize;
768 nat gens = RtsFlags.GcFlags.generations;
770 // live in the oldest generations
771 live = oldest_gen->steps[0].n_blocks +
772 oldest_gen->steps[0].n_large_blocks;
774 // default max size for all generations except zero
775 size = stg_max(live * RtsFlags.GcFlags.oldGenFactor,
776 RtsFlags.GcFlags.minOldGenSize);
778 // minimum size for generation zero
779 min_alloc = stg_max((RtsFlags.GcFlags.pcFreeHeap * max) / 200,
780 RtsFlags.GcFlags.minAllocAreaSize);
782 // Auto-enable compaction when the residency reaches a
783 // certain percentage of the maximum heap size (default: 30%).
784 if (RtsFlags.GcFlags.generations > 1 &&
785 (RtsFlags.GcFlags.compact ||
787 oldest_gen->steps[0].n_blocks >
788 (RtsFlags.GcFlags.compactThreshold * max) / 100))) {
789 oldest_gen->steps[0].is_compacted = 1;
790 // fprintf(stderr,"compaction: on\n", live);
792 oldest_gen->steps[0].is_compacted = 0;
793 // fprintf(stderr,"compaction: off\n", live);
796 // if we're going to go over the maximum heap size, reduce the
797 // size of the generations accordingly. The calculation is
798 // different if compaction is turned on, because we don't need
799 // to double the space required to collect the old generation.
802 // this test is necessary to ensure that the calculations
803 // below don't have any negative results - we're working
804 // with unsigned values here.
805 if (max < min_alloc) {
809 if (oldest_gen->steps[0].is_compacted) {
810 if ( (size + (size - 1) * (gens - 2) * 2) + min_alloc > max ) {
811 size = (max - min_alloc) / ((gens - 1) * 2 - 1);
814 if ( (size * (gens - 1) * 2) + min_alloc > max ) {
815 size = (max - min_alloc) / ((gens - 1) * 2);
825 fprintf(stderr,"live: %d, min_alloc: %d, size : %d, max = %d\n", live,
826 min_alloc, size, max);
829 for (g = 0; g < gens; g++) {
830 generations[g].max_blocks = size;
834 // Guess the amount of live data for stats.
837 /* Free the small objects allocated via allocate(), since this will
838 * all have been copied into G0S1 now.
840 if (small_alloc_list != NULL) {
841 freeChain(small_alloc_list);
843 small_alloc_list = NULL;
847 alloc_blocks_lim = RtsFlags.GcFlags.minAllocAreaSize;
849 // Start a new pinned_object_block
850 pinned_object_block = NULL;
852 /* Free the mark stack.
854 if (mark_stack_bdescr != NULL) {
855 freeGroup(mark_stack_bdescr);
860 for (g = 0; g <= N; g++) {
861 for (s = 0; s < generations[g].n_steps; s++) {
862 stp = &generations[g].steps[s];
863 if (stp->is_compacted && stp->bitmap != NULL) {
864 freeGroup(stp->bitmap);
869 /* Two-space collector:
870 * Free the old to-space, and estimate the amount of live data.
872 if (RtsFlags.GcFlags.generations == 1) {
875 if (old_to_blocks != NULL) {
876 freeChain(old_to_blocks);
878 for (bd = g0s0->to_blocks; bd != NULL; bd = bd->link) {
879 bd->flags = 0; // now from-space
882 /* For a two-space collector, we need to resize the nursery. */
884 /* set up a new nursery. Allocate a nursery size based on a
885 * function of the amount of live data (by default a factor of 2)
886 * Use the blocks from the old nursery if possible, freeing up any
889 * If we get near the maximum heap size, then adjust our nursery
890 * size accordingly. If the nursery is the same size as the live
891 * data (L), then we need 3L bytes. We can reduce the size of the
892 * nursery to bring the required memory down near 2L bytes.
894 * A normal 2-space collector would need 4L bytes to give the same
895 * performance we get from 3L bytes, reducing to the same
896 * performance at 2L bytes.
898 blocks = g0s0->n_to_blocks;
900 if ( RtsFlags.GcFlags.maxHeapSize != 0 &&
901 blocks * RtsFlags.GcFlags.oldGenFactor * 2 >
902 RtsFlags.GcFlags.maxHeapSize ) {
903 long adjusted_blocks; // signed on purpose
906 adjusted_blocks = (RtsFlags.GcFlags.maxHeapSize - 2 * blocks);
907 IF_DEBUG(gc, belch("@@ Near maximum heap size of 0x%x blocks, blocks = %d, adjusted to %ld", RtsFlags.GcFlags.maxHeapSize, blocks, adjusted_blocks));
908 pc_free = adjusted_blocks * 100 / RtsFlags.GcFlags.maxHeapSize;
909 if (pc_free < RtsFlags.GcFlags.pcFreeHeap) /* might even be < 0 */ {
912 blocks = adjusted_blocks;
915 blocks *= RtsFlags.GcFlags.oldGenFactor;
916 if (blocks < RtsFlags.GcFlags.minAllocAreaSize) {
917 blocks = RtsFlags.GcFlags.minAllocAreaSize;
920 resizeNursery(blocks);
923 /* Generational collector:
924 * If the user has given us a suggested heap size, adjust our
925 * allocation area to make best use of the memory available.
928 if (RtsFlags.GcFlags.heapSizeSuggestion) {
930 nat needed = calcNeeded(); // approx blocks needed at next GC
932 /* Guess how much will be live in generation 0 step 0 next time.
933 * A good approximation is obtained by finding the
934 * percentage of g0s0 that was live at the last minor GC.
937 g0s0_pcnt_kept = (new_blocks * 100) / g0s0->n_blocks;
940 /* Estimate a size for the allocation area based on the
941 * information available. We might end up going slightly under
942 * or over the suggested heap size, but we should be pretty
945 * Formula: suggested - needed
946 * ----------------------------
947 * 1 + g0s0_pcnt_kept/100
949 * where 'needed' is the amount of memory needed at the next
950 * collection for collecting all steps except g0s0.
953 (((long)RtsFlags.GcFlags.heapSizeSuggestion - (long)needed) * 100) /
954 (100 + (long)g0s0_pcnt_kept);
956 if (blocks < (long)RtsFlags.GcFlags.minAllocAreaSize) {
957 blocks = RtsFlags.GcFlags.minAllocAreaSize;
960 resizeNursery((nat)blocks);
963 // we might have added extra large blocks to the nursery, so
964 // resize back to minAllocAreaSize again.
965 resizeNursery(RtsFlags.GcFlags.minAllocAreaSize);
969 // mark the garbage collected CAFs as dead
970 #if 0 && defined(DEBUG) // doesn't work at the moment
971 if (major_gc) { gcCAFs(); }
975 // resetStaticObjectForRetainerProfiling() must be called before
977 resetStaticObjectForRetainerProfiling();
980 // zero the scavenged static object list
982 zero_static_object_list(scavenged_static_objects);
988 RELEASE_LOCK(&sched_mutex);
990 // start any pending finalizers
991 scheduleFinalizers(old_weak_ptr_list);
993 ACQUIRE_LOCK(&sched_mutex);
995 // send exceptions to any threads which were about to die
996 resurrectThreads(resurrected_threads);
998 // Update the stable pointer hash table.
999 updateStablePtrTable(major_gc);
1001 // check sanity after GC
1002 IF_DEBUG(sanity, checkSanity());
1004 // extra GC trace info
1005 IF_DEBUG(gc, statDescribeGens());
1008 // symbol-table based profiling
1009 /* heapCensus(to_blocks); */ /* ToDo */
1012 // restore enclosing cost centre
1017 // check for memory leaks if sanity checking is on
1018 IF_DEBUG(sanity, memInventory());
1020 #ifdef RTS_GTK_FRONTPANEL
1021 if (RtsFlags.GcFlags.frontpanel) {
1022 updateFrontPanelAfterGC( N, live );
1026 // ok, GC over: tell the stats department what happened.
1027 stat_endGC(allocated, collected, live, copied, N);
1033 /* -----------------------------------------------------------------------------
1036 traverse_weak_ptr_list is called possibly many times during garbage
1037 collection. It returns a flag indicating whether it did any work
1038 (i.e. called evacuate on any live pointers).
1040 Invariant: traverse_weak_ptr_list is called when the heap is in an
1041 idempotent state. That means that there are no pending
1042 evacuate/scavenge operations. This invariant helps the weak
1043 pointer code decide which weak pointers are dead - if there are no
1044 new live weak pointers, then all the currently unreachable ones are
1047 For generational GC: we just don't try to finalize weak pointers in
1048 older generations than the one we're collecting. This could
1049 probably be optimised by keeping per-generation lists of weak
1050 pointers, but for a few weak pointers this scheme will work.
1052 There are three distinct stages to processing weak pointers:
1054 - weak_stage == WeakPtrs
1056 We process all the weak pointers whos keys are alive (evacuate
1057 their values and finalizers), and repeat until we can find no new
1058 live keys. If no live keys are found in this pass, then we
1059 evacuate the finalizers of all the dead weak pointers in order to
1062 - weak_stage == WeakThreads
1064 Now, we discover which *threads* are still alive. Pointers to
1065 threads from the all_threads and main thread lists are the
1066 weakest of all: a pointers from the finalizer of a dead weak
1067 pointer can keep a thread alive. Any threads found to be unreachable
1068 are evacuated and placed on the resurrected_threads list so we
1069 can send them a signal later.
1071 - weak_stage == WeakDone
1073 No more evacuation is done.
1075 -------------------------------------------------------------------------- */
1078 traverse_weak_ptr_list(void)
1080 StgWeak *w, **last_w, *next_w;
1082 rtsBool flag = rtsFalse;
1084 switch (weak_stage) {
1090 /* doesn't matter where we evacuate values/finalizers to, since
1091 * these pointers are treated as roots (iff the keys are alive).
1095 last_w = &old_weak_ptr_list;
1096 for (w = old_weak_ptr_list; w != NULL; w = next_w) {
1098 /* There might be a DEAD_WEAK on the list if finalizeWeak# was
1099 * called on a live weak pointer object. Just remove it.
1101 if (w->header.info == &stg_DEAD_WEAK_info) {
1102 next_w = ((StgDeadWeak *)w)->link;
1107 ASSERT(get_itbl(w)->type == WEAK);
1109 /* Now, check whether the key is reachable.
1111 new = isAlive(w->key);
1114 // evacuate the value and finalizer
1115 w->value = evacuate(w->value);
1116 w->finalizer = evacuate(w->finalizer);
1117 // remove this weak ptr from the old_weak_ptr list
1119 // and put it on the new weak ptr list
1121 w->link = weak_ptr_list;
1124 IF_DEBUG(weak, belch("Weak pointer still alive at %p -> %p",
1129 last_w = &(w->link);
1135 /* If we didn't make any changes, then we can go round and kill all
1136 * the dead weak pointers. The old_weak_ptr list is used as a list
1137 * of pending finalizers later on.
1139 if (flag == rtsFalse) {
1140 for (w = old_weak_ptr_list; w; w = w->link) {
1141 w->finalizer = evacuate(w->finalizer);
1144 // Next, move to the WeakThreads stage after fully
1145 // scavenging the finalizers we've just evacuated.
1146 weak_stage = WeakThreads;
1152 /* Now deal with the all_threads list, which behaves somewhat like
1153 * the weak ptr list. If we discover any threads that are about to
1154 * become garbage, we wake them up and administer an exception.
1157 StgTSO *t, *tmp, *next, **prev;
1159 prev = &old_all_threads;
1160 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1162 (StgClosure *)tmp = isAlive((StgClosure *)t);
1168 ASSERT(get_itbl(t)->type == TSO);
1169 switch (t->what_next) {
1170 case ThreadRelocated:
1175 case ThreadComplete:
1176 // finshed or died. The thread might still be alive, but we
1177 // don't keep it on the all_threads list. Don't forget to
1178 // stub out its global_link field.
1179 next = t->global_link;
1180 t->global_link = END_TSO_QUEUE;
1188 // not alive (yet): leave this thread on the
1189 // old_all_threads list.
1190 prev = &(t->global_link);
1191 next = t->global_link;
1194 // alive: move this thread onto the all_threads list.
1195 next = t->global_link;
1196 t->global_link = all_threads;
1203 /* And resurrect any threads which were about to become garbage.
1206 StgTSO *t, *tmp, *next;
1207 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1208 next = t->global_link;
1209 (StgClosure *)tmp = evacuate((StgClosure *)t);
1210 tmp->global_link = resurrected_threads;
1211 resurrected_threads = tmp;
1215 weak_stage = WeakDone; // *now* we're done,
1216 return rtsTrue; // but one more round of scavenging, please
1219 barf("traverse_weak_ptr_list");
1224 /* -----------------------------------------------------------------------------
1225 After GC, the live weak pointer list may have forwarding pointers
1226 on it, because a weak pointer object was evacuated after being
1227 moved to the live weak pointer list. We remove those forwarding
1230 Also, we don't consider weak pointer objects to be reachable, but
1231 we must nevertheless consider them to be "live" and retain them.
1232 Therefore any weak pointer objects which haven't as yet been
1233 evacuated need to be evacuated now.
1234 -------------------------------------------------------------------------- */
1238 mark_weak_ptr_list ( StgWeak **list )
1240 StgWeak *w, **last_w;
1243 for (w = *list; w; w = w->link) {
1244 (StgClosure *)w = evacuate((StgClosure *)w);
1246 last_w = &(w->link);
1250 /* -----------------------------------------------------------------------------
1251 isAlive determines whether the given closure is still alive (after
1252 a garbage collection) or not. It returns the new address of the
1253 closure if it is alive, or NULL otherwise.
1255 NOTE: Use it before compaction only!
1256 -------------------------------------------------------------------------- */
1260 isAlive(StgClosure *p)
1262 const StgInfoTable *info;
1269 /* ToDo: for static closures, check the static link field.
1270 * Problem here is that we sometimes don't set the link field, eg.
1271 * for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
1276 // ignore closures in generations that we're not collecting.
1277 if (LOOKS_LIKE_STATIC(p) || bd->gen_no > N) {
1280 // large objects have an evacuated flag
1281 if (bd->flags & BF_LARGE) {
1282 if (bd->flags & BF_EVACUATED) {
1288 // check the mark bit for compacted steps
1289 if (bd->step->is_compacted && is_marked((P_)p,bd)) {
1293 switch (info->type) {
1298 case IND_OLDGEN: // rely on compatible layout with StgInd
1299 case IND_OLDGEN_PERM:
1300 // follow indirections
1301 p = ((StgInd *)p)->indirectee;
1306 return ((StgEvacuated *)p)->evacuee;
1309 if (((StgTSO *)p)->what_next == ThreadRelocated) {
1310 p = (StgClosure *)((StgTSO *)p)->link;
1322 mark_root(StgClosure **root)
1324 *root = evacuate(*root);
1330 bdescr *bd = allocBlock();
1331 bd->gen_no = stp->gen_no;
1334 if (stp->gen_no <= N) {
1335 bd->flags = BF_EVACUATED;
1340 stp->hp_bd->free = stp->hp;
1341 stp->hp_bd->link = bd;
1342 stp->hp = bd->start;
1343 stp->hpLim = stp->hp + BLOCK_SIZE_W;
1350 static __inline__ void
1351 upd_evacuee(StgClosure *p, StgClosure *dest)
1353 p->header.info = &stg_EVACUATED_info;
1354 ((StgEvacuated *)p)->evacuee = dest;
1358 static __inline__ StgClosure *
1359 copy(StgClosure *src, nat size, step *stp)
1364 nat size_org = size;
1367 TICK_GC_WORDS_COPIED(size);
1368 /* Find out where we're going, using the handy "to" pointer in
1369 * the step of the source object. If it turns out we need to
1370 * evacuate to an older generation, adjust it here (see comment
1373 if (stp->gen_no < evac_gen) {
1374 #ifdef NO_EAGER_PROMOTION
1375 failed_to_evac = rtsTrue;
1377 stp = &generations[evac_gen].steps[0];
1381 /* chain a new block onto the to-space for the destination step if
1384 if (stp->hp + size >= stp->hpLim) {
1388 for(to = stp->hp, from = (P_)src; size>0; --size) {
1394 upd_evacuee(src,(StgClosure *)dest);
1396 // We store the size of the just evacuated object in the LDV word so that
1397 // the profiler can guess the position of the next object later.
1398 SET_EVACUAEE_FOR_LDV(src, size_org);
1400 return (StgClosure *)dest;
1403 /* Special version of copy() for when we only want to copy the info
1404 * pointer of an object, but reserve some padding after it. This is
1405 * used to optimise evacuation of BLACKHOLEs.
1410 copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *stp)
1415 nat size_to_copy_org = size_to_copy;
1418 TICK_GC_WORDS_COPIED(size_to_copy);
1419 if (stp->gen_no < evac_gen) {
1420 #ifdef NO_EAGER_PROMOTION
1421 failed_to_evac = rtsTrue;
1423 stp = &generations[evac_gen].steps[0];
1427 if (stp->hp + size_to_reserve >= stp->hpLim) {
1431 for(to = stp->hp, from = (P_)src; size_to_copy>0; --size_to_copy) {
1436 stp->hp += size_to_reserve;
1437 upd_evacuee(src,(StgClosure *)dest);
1439 // We store the size of the just evacuated object in the LDV word so that
1440 // the profiler can guess the position of the next object later.
1441 // size_to_copy_org is wrong because the closure already occupies size_to_reserve
1443 SET_EVACUAEE_FOR_LDV(src, size_to_reserve);
1445 if (size_to_reserve - size_to_copy_org > 0)
1446 FILL_SLOP(stp->hp - 1, (int)(size_to_reserve - size_to_copy_org));
1448 return (StgClosure *)dest;
1452 /* -----------------------------------------------------------------------------
1453 Evacuate a large object
1455 This just consists of removing the object from the (doubly-linked)
1456 large_alloc_list, and linking it on to the (singly-linked)
1457 new_large_objects list, from where it will be scavenged later.
1459 Convention: bd->flags has BF_EVACUATED set for a large object
1460 that has been evacuated, or unset otherwise.
1461 -------------------------------------------------------------------------- */
1465 evacuate_large(StgPtr p)
1467 bdescr *bd = Bdescr(p);
1470 // object must be at the beginning of the block (or be a ByteArray)
1471 ASSERT(get_itbl((StgClosure *)p)->type == ARR_WORDS ||
1472 (((W_)p & BLOCK_MASK) == 0));
1474 // already evacuated?
1475 if (bd->flags & BF_EVACUATED) {
1476 /* Don't forget to set the failed_to_evac flag if we didn't get
1477 * the desired destination (see comments in evacuate()).
1479 if (bd->gen_no < evac_gen) {
1480 failed_to_evac = rtsTrue;
1481 TICK_GC_FAILED_PROMOTION();
1487 // remove from large_object list
1489 bd->u.back->link = bd->link;
1490 } else { // first object in the list
1491 stp->large_objects = bd->link;
1494 bd->link->u.back = bd->u.back;
1497 /* link it on to the evacuated large object list of the destination step
1500 if (stp->gen_no < evac_gen) {
1501 #ifdef NO_EAGER_PROMOTION
1502 failed_to_evac = rtsTrue;
1504 stp = &generations[evac_gen].steps[0];
1509 bd->gen_no = stp->gen_no;
1510 bd->link = stp->new_large_objects;
1511 stp->new_large_objects = bd;
1512 bd->flags |= BF_EVACUATED;
1515 /* -----------------------------------------------------------------------------
1516 Adding a MUT_CONS to an older generation.
1518 This is necessary from time to time when we end up with an
1519 old-to-new generation pointer in a non-mutable object. We defer
1520 the promotion until the next GC.
1521 -------------------------------------------------------------------------- */
1525 mkMutCons(StgClosure *ptr, generation *gen)
1530 stp = &gen->steps[0];
1532 /* chain a new block onto the to-space for the destination step if
1535 if (stp->hp + sizeofW(StgIndOldGen) >= stp->hpLim) {
1539 q = (StgMutVar *)stp->hp;
1540 stp->hp += sizeofW(StgMutVar);
1542 SET_HDR(q,&stg_MUT_CONS_info,CCS_GC);
1544 recordOldToNewPtrs((StgMutClosure *)q);
1546 return (StgClosure *)q;
1549 /* -----------------------------------------------------------------------------
1552 This is called (eventually) for every live object in the system.
1554 The caller to evacuate specifies a desired generation in the
1555 evac_gen global variable. The following conditions apply to
1556 evacuating an object which resides in generation M when we're
1557 collecting up to generation N
1561 else evac to step->to
1563 if M < evac_gen evac to evac_gen, step 0
1565 if the object is already evacuated, then we check which generation
1568 if M >= evac_gen do nothing
1569 if M < evac_gen set failed_to_evac flag to indicate that we
1570 didn't manage to evacuate this object into evac_gen.
1572 -------------------------------------------------------------------------- */
1575 evacuate(StgClosure *q)
1580 const StgInfoTable *info;
1583 if (HEAP_ALLOCED(q)) {
1586 // not a group head: find the group head
1587 if (bd->blocks == 0) { bd = bd->link; }
1589 if (bd->gen_no > N) {
1590 /* Can't evacuate this object, because it's in a generation
1591 * older than the ones we're collecting. Let's hope that it's
1592 * in evac_gen or older, or we will have to arrange to track
1593 * this pointer using the mutable list.
1595 if (bd->gen_no < evac_gen) {
1597 failed_to_evac = rtsTrue;
1598 TICK_GC_FAILED_PROMOTION();
1603 /* evacuate large objects by re-linking them onto a different list.
1605 if (bd->flags & BF_LARGE) {
1607 if (info->type == TSO &&
1608 ((StgTSO *)q)->what_next == ThreadRelocated) {
1609 q = (StgClosure *)((StgTSO *)q)->link;
1612 evacuate_large((P_)q);
1616 /* If the object is in a step that we're compacting, then we
1617 * need to use an alternative evacuate procedure.
1619 if (bd->step->is_compacted) {
1620 if (!is_marked((P_)q,bd)) {
1622 if (mark_stack_full()) {
1623 mark_stack_overflowed = rtsTrue;
1626 push_mark_stack((P_)q);
1634 else stp = NULL; // make sure copy() will crash if HEAP_ALLOCED is wrong
1637 // make sure the info pointer is into text space
1638 ASSERT(q && (LOOKS_LIKE_GHC_INFO(GET_INFO(q))
1639 || IS_HUGS_CONSTR_INFO(GET_INFO(q))));
1642 switch (info -> type) {
1646 to = copy(q,sizeW_fromITBL(info),stp);
1651 StgWord w = (StgWord)q->payload[0];
1652 if (q->header.info == Czh_con_info &&
1653 // unsigned, so always true: (StgChar)w >= MIN_CHARLIKE &&
1654 (StgChar)w <= MAX_CHARLIKE) {
1655 return (StgClosure *)CHARLIKE_CLOSURE((StgChar)w);
1657 if (q->header.info == Izh_con_info &&
1658 (StgInt)w >= MIN_INTLIKE && (StgInt)w <= MAX_INTLIKE) {
1659 return (StgClosure *)INTLIKE_CLOSURE((StgInt)w);
1661 // else, fall through ...
1667 return copy(q,sizeofW(StgHeader)+1,stp);
1669 case THUNK_1_0: // here because of MIN_UPD_SIZE
1674 #ifdef NO_PROMOTE_THUNKS
1675 if (bd->gen_no == 0 &&
1676 bd->step->no != 0 &&
1677 bd->step->no == generations[bd->gen_no].n_steps-1) {
1681 return copy(q,sizeofW(StgHeader)+2,stp);
1689 return copy(q,sizeofW(StgHeader)+2,stp);
1695 case IND_OLDGEN_PERM:
1700 return copy(q,sizeW_fromITBL(info),stp);
1703 case SE_CAF_BLACKHOLE:
1706 return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
1709 to = copy(q,BLACKHOLE_sizeW(),stp);
1712 case THUNK_SELECTOR:
1714 const StgInfoTable* selectee_info;
1715 StgClosure* selectee = ((StgSelector*)q)->selectee;
1718 selectee_info = get_itbl(selectee);
1719 switch (selectee_info->type) {
1727 case CONSTR_NOCAF_STATIC:
1729 StgWord offset = info->layout.selector_offset;
1731 // check that the size is in range
1733 (StgWord32)(selectee_info->layout.payload.ptrs +
1734 selectee_info->layout.payload.nptrs));
1736 // perform the selection!
1737 q = selectee->payload[offset];
1738 if (major_gc==rtsTrue) {TICK_GC_SEL_MAJOR();} else {TICK_GC_SEL_MINOR();}
1740 /* if we're already in to-space, there's no need to continue
1741 * with the evacuation, just update the source address with
1742 * a pointer to the (evacuated) constructor field.
1744 if (HEAP_ALLOCED(q)) {
1745 bdescr *bd = Bdescr((P_)q);
1746 if (bd->flags & BF_EVACUATED) {
1747 if (bd->gen_no < evac_gen) {
1748 failed_to_evac = rtsTrue;
1749 TICK_GC_FAILED_PROMOTION();
1755 /* otherwise, carry on and evacuate this constructor field,
1756 * (but not the constructor itself)
1765 case IND_OLDGEN_PERM:
1766 selectee = ((StgInd *)selectee)->indirectee;
1770 selectee = ((StgEvacuated *)selectee)->evacuee;
1773 case THUNK_SELECTOR:
1775 /* Disabled 03 April 2001 by JRS; it seems to cause the GC (or
1776 something) to go into an infinite loop when the nightly
1777 stage2 compiles PrelTup.lhs. */
1779 /* we can't recurse indefinitely in evacuate(), so set a
1780 * limit on the number of times we can go around this
1783 if (thunk_selector_depth < MAX_THUNK_SELECTOR_DEPTH) {
1785 bd = Bdescr((P_)selectee);
1786 if (!bd->flags & BF_EVACUATED) {
1787 thunk_selector_depth++;
1788 selectee = evacuate(selectee);
1789 thunk_selector_depth--;
1793 TICK_GC_SEL_ABANDONED();
1794 // and fall through...
1807 case SE_CAF_BLACKHOLE:
1811 // not evaluated yet
1815 // a copy of the top-level cases below
1816 case RBH: // cf. BLACKHOLE_BQ
1818 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
1819 to = copy(q,BLACKHOLE_sizeW(),stp);
1820 //ToDo: derive size etc from reverted IP
1821 //to = copy(q,size,stp);
1822 // recordMutable((StgMutClosure *)to);
1827 ASSERT(sizeofW(StgBlockedFetch) >= MIN_NONUPD_SIZE);
1828 to = copy(q,sizeofW(StgBlockedFetch),stp);
1835 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1836 to = copy(q,sizeofW(StgFetchMe),stp);
1840 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1841 to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
1846 barf("evacuate: THUNK_SELECTOR: strange selectee %d",
1847 (int)(selectee_info->type));
1850 return copy(q,THUNK_SELECTOR_sizeW(),stp);
1854 // follow chains of indirections, don't evacuate them
1855 q = ((StgInd*)q)->indirectee;
1859 if (info->srt_len > 0 && major_gc &&
1860 THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
1861 THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
1862 static_objects = (StgClosure *)q;
1867 if (info->srt_len > 0 && major_gc &&
1868 FUN_STATIC_LINK((StgClosure *)q) == NULL) {
1869 FUN_STATIC_LINK((StgClosure *)q) = static_objects;
1870 static_objects = (StgClosure *)q;
1875 /* If q->saved_info != NULL, then it's a revertible CAF - it'll be
1876 * on the CAF list, so don't do anything with it here (we'll
1877 * scavenge it later).
1880 && ((StgIndStatic *)q)->saved_info == NULL
1881 && IND_STATIC_LINK((StgClosure *)q) == NULL) {
1882 IND_STATIC_LINK((StgClosure *)q) = static_objects;
1883 static_objects = (StgClosure *)q;
1888 if (major_gc && STATIC_LINK(info,(StgClosure *)q) == NULL) {
1889 STATIC_LINK(info,(StgClosure *)q) = static_objects;
1890 static_objects = (StgClosure *)q;
1894 case CONSTR_INTLIKE:
1895 case CONSTR_CHARLIKE:
1896 case CONSTR_NOCAF_STATIC:
1897 /* no need to put these on the static linked list, they don't need
1912 // shouldn't see these
1913 barf("evacuate: stack frame at %p\n", q);
1917 /* PAPs and AP_UPDs are special - the payload is a copy of a chunk
1918 * of stack, tagging and all.
1920 return copy(q,pap_sizeW((StgPAP*)q),stp);
1923 /* Already evacuated, just return the forwarding address.
1924 * HOWEVER: if the requested destination generation (evac_gen) is
1925 * older than the actual generation (because the object was
1926 * already evacuated to a younger generation) then we have to
1927 * set the failed_to_evac flag to indicate that we couldn't
1928 * manage to promote the object to the desired generation.
1930 if (evac_gen > 0) { // optimisation
1931 StgClosure *p = ((StgEvacuated*)q)->evacuee;
1932 if (Bdescr((P_)p)->gen_no < evac_gen) {
1933 failed_to_evac = rtsTrue;
1934 TICK_GC_FAILED_PROMOTION();
1937 return ((StgEvacuated*)q)->evacuee;
1940 // just copy the block
1941 return copy(q,arr_words_sizeW((StgArrWords *)q),stp);
1944 case MUT_ARR_PTRS_FROZEN:
1945 // just copy the block
1946 return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
1950 StgTSO *tso = (StgTSO *)q;
1952 /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
1954 if (tso->what_next == ThreadRelocated) {
1955 q = (StgClosure *)tso->link;
1959 /* To evacuate a small TSO, we need to relocate the update frame
1963 StgTSO *new_tso = (StgTSO *)copy((StgClosure *)tso,tso_sizeW(tso),stp);
1964 move_TSO(tso, new_tso);
1965 return (StgClosure *)new_tso;
1970 case RBH: // cf. BLACKHOLE_BQ
1972 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
1973 to = copy(q,BLACKHOLE_sizeW(),stp);
1974 //ToDo: derive size etc from reverted IP
1975 //to = copy(q,size,stp);
1977 belch("@@ evacuate: RBH %p (%s) to %p (%s)",
1978 q, info_type(q), to, info_type(to)));
1983 ASSERT(sizeofW(StgBlockedFetch) >= MIN_NONUPD_SIZE);
1984 to = copy(q,sizeofW(StgBlockedFetch),stp);
1986 belch("@@ evacuate: %p (%s) to %p (%s)",
1987 q, info_type(q), to, info_type(to)));
1994 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1995 to = copy(q,sizeofW(StgFetchMe),stp);
1997 belch("@@ evacuate: %p (%s) to %p (%s)",
1998 q, info_type(q), to, info_type(to)));
2002 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
2003 to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
2005 belch("@@ evacuate: %p (%s) to %p (%s)",
2006 q, info_type(q), to, info_type(to)));
2011 barf("evacuate: strange closure type %d", (int)(info->type));
2017 /* -----------------------------------------------------------------------------
2018 move_TSO is called to update the TSO structure after it has been
2019 moved from one place to another.
2020 -------------------------------------------------------------------------- */
2023 move_TSO(StgTSO *src, StgTSO *dest)
2027 // relocate the stack pointers...
2028 diff = (StgPtr)dest - (StgPtr)src; // In *words*
2029 dest->sp = (StgPtr)dest->sp + diff;
2030 dest->su = (StgUpdateFrame *) ((P_)dest->su + diff);
2032 relocate_stack(dest, diff);
2035 /* -----------------------------------------------------------------------------
2036 relocate_stack is called to update the linkage between
2037 UPDATE_FRAMEs (and SEQ_FRAMEs etc.) when a stack is moved from one
2039 -------------------------------------------------------------------------- */
2042 relocate_stack(StgTSO *dest, ptrdiff_t diff)
2050 while ((P_)su < dest->stack + dest->stack_size) {
2051 switch (get_itbl(su)->type) {
2053 // GCC actually manages to common up these three cases!
2056 su->link = (StgUpdateFrame *) ((StgPtr)su->link + diff);
2061 cf = (StgCatchFrame *)su;
2062 cf->link = (StgUpdateFrame *) ((StgPtr)cf->link + diff);
2067 sf = (StgSeqFrame *)su;
2068 sf->link = (StgUpdateFrame *) ((StgPtr)sf->link + diff);
2077 barf("relocate_stack %d", (int)(get_itbl(su)->type));
2088 scavenge_srt(const StgInfoTable *info)
2090 StgClosure **srt, **srt_end;
2092 /* evacuate the SRT. If srt_len is zero, then there isn't an
2093 * srt field in the info table. That's ok, because we'll
2094 * never dereference it.
2096 srt = (StgClosure **)(info->srt);
2097 srt_end = srt + info->srt_len;
2098 for (; srt < srt_end; srt++) {
2099 /* Special-case to handle references to closures hiding out in DLLs, since
2100 double indirections required to get at those. The code generator knows
2101 which is which when generating the SRT, so it stores the (indirect)
2102 reference to the DLL closure in the table by first adding one to it.
2103 We check for this here, and undo the addition before evacuating it.
2105 If the SRT entry hasn't got bit 0 set, the SRT entry points to a
2106 closure that's fixed at link-time, and no extra magic is required.
2108 #ifdef ENABLE_WIN32_DLL_SUPPORT
2109 if ( (unsigned long)(*srt) & 0x1 ) {
2110 evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
2120 /* -----------------------------------------------------------------------------
2122 -------------------------------------------------------------------------- */
2125 scavengeTSO (StgTSO *tso)
2127 // chase the link field for any TSOs on the same queue
2128 (StgClosure *)tso->link = evacuate((StgClosure *)tso->link);
2129 if ( tso->why_blocked == BlockedOnMVar
2130 || tso->why_blocked == BlockedOnBlackHole
2131 || tso->why_blocked == BlockedOnException
2133 || tso->why_blocked == BlockedOnGA
2134 || tso->why_blocked == BlockedOnGA_NoSend
2137 tso->block_info.closure = evacuate(tso->block_info.closure);
2139 if ( tso->blocked_exceptions != NULL ) {
2140 tso->blocked_exceptions =
2141 (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
2143 // scavenge this thread's stack
2144 scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
2147 /* -----------------------------------------------------------------------------
2148 Scavenge a given step until there are no more objects in this step
2151 evac_gen is set by the caller to be either zero (for a step in a
2152 generation < N) or G where G is the generation of the step being
2155 We sometimes temporarily change evac_gen back to zero if we're
2156 scavenging a mutable object where early promotion isn't such a good
2158 -------------------------------------------------------------------------- */
2166 nat saved_evac_gen = evac_gen;
2171 failed_to_evac = rtsFalse;
2173 /* scavenge phase - standard breadth-first scavenging of the
2177 while (bd != stp->hp_bd || p < stp->hp) {
2179 // If we're at the end of this block, move on to the next block
2180 if (bd != stp->hp_bd && p == bd->free) {
2186 info = get_itbl((StgClosure *)p);
2187 ASSERT(p && (LOOKS_LIKE_GHC_INFO(info) || IS_HUGS_CONSTR_INFO(info)));
2190 switch (info->type) {
2193 /* treat MVars specially, because we don't want to evacuate the
2194 * mut_link field in the middle of the closure.
2197 StgMVar *mvar = ((StgMVar *)p);
2199 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
2200 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
2201 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
2202 evac_gen = saved_evac_gen;
2203 recordMutable((StgMutClosure *)mvar);
2204 failed_to_evac = rtsFalse; // mutable.
2205 p += sizeofW(StgMVar);
2213 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2214 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2215 p += sizeofW(StgHeader) + 2;
2220 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2221 p += sizeofW(StgHeader) + 2; // MIN_UPD_SIZE
2227 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2228 p += sizeofW(StgHeader) + 1;
2233 p += sizeofW(StgHeader) + 2; // MIN_UPD_SIZE
2239 p += sizeofW(StgHeader) + 1;
2246 p += sizeofW(StgHeader) + 2;
2253 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2254 p += sizeofW(StgHeader) + 2;
2270 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2271 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2272 (StgClosure *)*p = evacuate((StgClosure *)*p);
2274 p += info->layout.payload.nptrs;
2279 if (stp->gen->no != 0) {
2282 // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an
2283 // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
2284 LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
2287 // Todo: maybe use SET_HDR() and remove LDV_recordCreate()?
2289 SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
2292 // We pretend that p has just been created.
2293 LDV_recordCreate((StgClosure *)p);
2297 case IND_OLDGEN_PERM:
2298 ((StgIndOldGen *)p)->indirectee =
2299 evacuate(((StgIndOldGen *)p)->indirectee);
2300 if (failed_to_evac) {
2301 failed_to_evac = rtsFalse;
2302 recordOldToNewPtrs((StgMutClosure *)p);
2304 p += sizeofW(StgIndOldGen);
2309 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2310 evac_gen = saved_evac_gen;
2311 recordMutable((StgMutClosure *)p);
2312 failed_to_evac = rtsFalse; // mutable anyhow
2313 p += sizeofW(StgMutVar);
2318 failed_to_evac = rtsFalse; // mutable anyhow
2319 p += sizeofW(StgMutVar);
2323 case SE_CAF_BLACKHOLE:
2326 p += BLACKHOLE_sizeW();
2331 StgBlockingQueue *bh = (StgBlockingQueue *)p;
2332 (StgClosure *)bh->blocking_queue =
2333 evacuate((StgClosure *)bh->blocking_queue);
2334 recordMutable((StgMutClosure *)bh);
2335 failed_to_evac = rtsFalse;
2336 p += BLACKHOLE_sizeW();
2340 case THUNK_SELECTOR:
2342 StgSelector *s = (StgSelector *)p;
2343 s->selectee = evacuate(s->selectee);
2344 p += THUNK_SELECTOR_sizeW();
2348 case AP_UPD: // same as PAPs
2350 /* Treat a PAP just like a section of stack, not forgetting to
2351 * evacuate the function pointer too...
2354 StgPAP* pap = (StgPAP *)p;
2356 pap->fun = evacuate(pap->fun);
2357 scavenge_stack((P_)pap->payload, (P_)pap->payload + pap->n_args);
2358 p += pap_sizeW(pap);
2363 // nothing to follow
2364 p += arr_words_sizeW((StgArrWords *)p);
2368 // follow everything
2372 evac_gen = 0; // repeatedly mutable
2373 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2374 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2375 (StgClosure *)*p = evacuate((StgClosure *)*p);
2377 evac_gen = saved_evac_gen;
2378 recordMutable((StgMutClosure *)q);
2379 failed_to_evac = rtsFalse; // mutable anyhow.
2383 case MUT_ARR_PTRS_FROZEN:
2384 // follow everything
2388 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2389 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2390 (StgClosure *)*p = evacuate((StgClosure *)*p);
2392 // it's tempting to recordMutable() if failed_to_evac is
2393 // false, but that breaks some assumptions (eg. every
2394 // closure on the mutable list is supposed to have the MUT
2395 // flag set, and MUT_ARR_PTRS_FROZEN doesn't).
2401 StgTSO *tso = (StgTSO *)p;
2404 evac_gen = saved_evac_gen;
2405 recordMutable((StgMutClosure *)tso);
2406 failed_to_evac = rtsFalse; // mutable anyhow.
2407 p += tso_sizeW(tso);
2412 case RBH: // cf. BLACKHOLE_BQ
2415 nat size, ptrs, nonptrs, vhs;
2417 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2419 StgRBH *rbh = (StgRBH *)p;
2420 (StgClosure *)rbh->blocking_queue =
2421 evacuate((StgClosure *)rbh->blocking_queue);
2422 recordMutable((StgMutClosure *)to);
2423 failed_to_evac = rtsFalse; // mutable anyhow.
2425 belch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2426 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2427 // ToDo: use size of reverted closure here!
2428 p += BLACKHOLE_sizeW();
2434 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2435 // follow the pointer to the node which is being demanded
2436 (StgClosure *)bf->node =
2437 evacuate((StgClosure *)bf->node);
2438 // follow the link to the rest of the blocking queue
2439 (StgClosure *)bf->link =
2440 evacuate((StgClosure *)bf->link);
2441 if (failed_to_evac) {
2442 failed_to_evac = rtsFalse;
2443 recordMutable((StgMutClosure *)bf);
2446 belch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
2447 bf, info_type((StgClosure *)bf),
2448 bf->node, info_type(bf->node)));
2449 p += sizeofW(StgBlockedFetch);
2457 p += sizeofW(StgFetchMe);
2458 break; // nothing to do in this case
2460 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
2462 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
2463 (StgClosure *)fmbq->blocking_queue =
2464 evacuate((StgClosure *)fmbq->blocking_queue);
2465 if (failed_to_evac) {
2466 failed_to_evac = rtsFalse;
2467 recordMutable((StgMutClosure *)fmbq);
2470 belch("@@ scavenge: %p (%s) exciting, isn't it",
2471 p, info_type((StgClosure *)p)));
2472 p += sizeofW(StgFetchMeBlockingQueue);
2478 barf("scavenge: unimplemented/strange closure type %d @ %p",
2482 /* If we didn't manage to promote all the objects pointed to by
2483 * the current object, then we have to designate this object as
2484 * mutable (because it contains old-to-new generation pointers).
2486 if (failed_to_evac) {
2487 failed_to_evac = rtsFalse;
2488 mkMutCons((StgClosure *)q, &generations[evac_gen]);
2496 /* -----------------------------------------------------------------------------
2497 Scavenge everything on the mark stack.
2499 This is slightly different from scavenge():
2500 - we don't walk linearly through the objects, so the scavenger
2501 doesn't need to advance the pointer on to the next object.
2502 -------------------------------------------------------------------------- */
2505 scavenge_mark_stack(void)
2511 evac_gen = oldest_gen->no;
2512 saved_evac_gen = evac_gen;
2515 while (!mark_stack_empty()) {
2516 p = pop_mark_stack();
2518 info = get_itbl((StgClosure *)p);
2519 ASSERT(p && (LOOKS_LIKE_GHC_INFO(info) || IS_HUGS_CONSTR_INFO(info)));
2522 switch (info->type) {
2525 /* treat MVars specially, because we don't want to evacuate the
2526 * mut_link field in the middle of the closure.
2529 StgMVar *mvar = ((StgMVar *)p);
2531 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
2532 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
2533 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
2534 evac_gen = saved_evac_gen;
2535 failed_to_evac = rtsFalse; // mutable.
2543 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2544 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2554 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2579 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2580 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2581 (StgClosure *)*p = evacuate((StgClosure *)*p);
2587 // don't need to do anything here: the only possible case
2588 // is that we're in a 1-space compacting collector, with
2589 // no "old" generation.
2593 case IND_OLDGEN_PERM:
2594 ((StgIndOldGen *)p)->indirectee =
2595 evacuate(((StgIndOldGen *)p)->indirectee);
2596 if (failed_to_evac) {
2597 recordOldToNewPtrs((StgMutClosure *)p);
2599 failed_to_evac = rtsFalse;
2604 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2605 evac_gen = saved_evac_gen;
2606 failed_to_evac = rtsFalse;
2611 failed_to_evac = rtsFalse;
2615 case SE_CAF_BLACKHOLE:
2623 StgBlockingQueue *bh = (StgBlockingQueue *)p;
2624 (StgClosure *)bh->blocking_queue =
2625 evacuate((StgClosure *)bh->blocking_queue);
2626 failed_to_evac = rtsFalse;
2630 case THUNK_SELECTOR:
2632 StgSelector *s = (StgSelector *)p;
2633 s->selectee = evacuate(s->selectee);
2637 case AP_UPD: // same as PAPs
2639 /* Treat a PAP just like a section of stack, not forgetting to
2640 * evacuate the function pointer too...
2643 StgPAP* pap = (StgPAP *)p;
2645 pap->fun = evacuate(pap->fun);
2646 scavenge_stack((P_)pap->payload, (P_)pap->payload + pap->n_args);
2651 // follow everything
2655 evac_gen = 0; // repeatedly mutable
2656 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2657 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2658 (StgClosure *)*p = evacuate((StgClosure *)*p);
2660 evac_gen = saved_evac_gen;
2661 failed_to_evac = rtsFalse; // mutable anyhow.
2665 case MUT_ARR_PTRS_FROZEN:
2666 // follow everything
2670 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2671 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2672 (StgClosure *)*p = evacuate((StgClosure *)*p);
2679 StgTSO *tso = (StgTSO *)p;
2682 evac_gen = saved_evac_gen;
2683 failed_to_evac = rtsFalse;
2688 case RBH: // cf. BLACKHOLE_BQ
2691 nat size, ptrs, nonptrs, vhs;
2693 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2695 StgRBH *rbh = (StgRBH *)p;
2696 (StgClosure *)rbh->blocking_queue =
2697 evacuate((StgClosure *)rbh->blocking_queue);
2698 recordMutable((StgMutClosure *)rbh);
2699 failed_to_evac = rtsFalse; // mutable anyhow.
2701 belch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2702 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2708 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2709 // follow the pointer to the node which is being demanded
2710 (StgClosure *)bf->node =
2711 evacuate((StgClosure *)bf->node);
2712 // follow the link to the rest of the blocking queue
2713 (StgClosure *)bf->link =
2714 evacuate((StgClosure *)bf->link);
2715 if (failed_to_evac) {
2716 failed_to_evac = rtsFalse;
2717 recordMutable((StgMutClosure *)bf);
2720 belch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
2721 bf, info_type((StgClosure *)bf),
2722 bf->node, info_type(bf->node)));
2730 break; // nothing to do in this case
2732 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
2734 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
2735 (StgClosure *)fmbq->blocking_queue =
2736 evacuate((StgClosure *)fmbq->blocking_queue);
2737 if (failed_to_evac) {
2738 failed_to_evac = rtsFalse;
2739 recordMutable((StgMutClosure *)fmbq);
2742 belch("@@ scavenge: %p (%s) exciting, isn't it",
2743 p, info_type((StgClosure *)p)));
2749 barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p",
2753 if (failed_to_evac) {
2754 failed_to_evac = rtsFalse;
2755 mkMutCons((StgClosure *)q, &generations[evac_gen]);
2758 // mark the next bit to indicate "scavenged"
2759 mark(q+1, Bdescr(q));
2761 } // while (!mark_stack_empty())
2763 // start a new linear scan if the mark stack overflowed at some point
2764 if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
2765 IF_DEBUG(gc, belch("scavenge_mark_stack: starting linear scan"));
2766 mark_stack_overflowed = rtsFalse;
2767 oldgen_scan_bd = oldest_gen->steps[0].blocks;
2768 oldgen_scan = oldgen_scan_bd->start;
2771 if (oldgen_scan_bd) {
2772 // push a new thing on the mark stack
2774 // find a closure that is marked but not scavenged, and start
2776 while (oldgen_scan < oldgen_scan_bd->free
2777 && !is_marked(oldgen_scan,oldgen_scan_bd)) {
2781 if (oldgen_scan < oldgen_scan_bd->free) {
2783 // already scavenged?
2784 if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
2785 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
2788 push_mark_stack(oldgen_scan);
2789 // ToDo: bump the linear scan by the actual size of the object
2790 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
2794 oldgen_scan_bd = oldgen_scan_bd->link;
2795 if (oldgen_scan_bd != NULL) {
2796 oldgen_scan = oldgen_scan_bd->start;
2802 /* -----------------------------------------------------------------------------
2803 Scavenge one object.
2805 This is used for objects that are temporarily marked as mutable
2806 because they contain old-to-new generation pointers. Only certain
2807 objects can have this property.
2808 -------------------------------------------------------------------------- */
2811 scavenge_one(StgPtr p)
2813 const StgInfoTable *info;
2814 nat saved_evac_gen = evac_gen;
2817 ASSERT(p && (LOOKS_LIKE_GHC_INFO(GET_INFO((StgClosure *)p))
2818 || IS_HUGS_CONSTR_INFO(GET_INFO((StgClosure *)p))));
2820 info = get_itbl((StgClosure *)p);
2822 switch (info->type) {
2825 case FUN_1_0: // hardly worth specialising these guys
2845 case IND_OLDGEN_PERM:
2849 end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2850 for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
2851 (StgClosure *)*q = evacuate((StgClosure *)*q);
2857 case SE_CAF_BLACKHOLE:
2862 case THUNK_SELECTOR:
2864 StgSelector *s = (StgSelector *)p;
2865 s->selectee = evacuate(s->selectee);
2870 // nothing to follow
2875 // follow everything
2878 evac_gen = 0; // repeatedly mutable
2879 recordMutable((StgMutClosure *)p);
2880 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2881 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2882 (StgClosure *)*p = evacuate((StgClosure *)*p);
2884 evac_gen = saved_evac_gen;
2885 failed_to_evac = rtsFalse;
2889 case MUT_ARR_PTRS_FROZEN:
2891 // follow everything
2894 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2895 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2896 (StgClosure *)*p = evacuate((StgClosure *)*p);
2903 StgTSO *tso = (StgTSO *)p;
2905 evac_gen = 0; // repeatedly mutable
2907 recordMutable((StgMutClosure *)tso);
2908 evac_gen = saved_evac_gen;
2909 failed_to_evac = rtsFalse;
2916 StgPAP* pap = (StgPAP *)p;
2917 pap->fun = evacuate(pap->fun);
2918 scavenge_stack((P_)pap->payload, (P_)pap->payload + pap->n_args);
2923 // This might happen if for instance a MUT_CONS was pointing to a
2924 // THUNK which has since been updated. The IND_OLDGEN will
2925 // be on the mutable list anyway, so we don't need to do anything
2930 barf("scavenge_one: strange object %d", (int)(info->type));
2933 no_luck = failed_to_evac;
2934 failed_to_evac = rtsFalse;
2938 /* -----------------------------------------------------------------------------
2939 Scavenging mutable lists.
2941 We treat the mutable list of each generation > N (i.e. all the
2942 generations older than the one being collected) as roots. We also
2943 remove non-mutable objects from the mutable list at this point.
2944 -------------------------------------------------------------------------- */
2947 scavenge_mut_once_list(generation *gen)
2949 const StgInfoTable *info;
2950 StgMutClosure *p, *next, *new_list;
2952 p = gen->mut_once_list;
2953 new_list = END_MUT_LIST;
2957 failed_to_evac = rtsFalse;
2959 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
2961 // make sure the info pointer is into text space
2962 ASSERT(p && (LOOKS_LIKE_GHC_INFO(GET_INFO(p))
2963 || IS_HUGS_CONSTR_INFO(GET_INFO(p))));
2967 if (info->type==RBH)
2968 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
2970 switch(info->type) {
2973 case IND_OLDGEN_PERM:
2975 /* Try to pull the indirectee into this generation, so we can
2976 * remove the indirection from the mutable list.
2978 ((StgIndOldGen *)p)->indirectee =
2979 evacuate(((StgIndOldGen *)p)->indirectee);
2981 #if 0 && defined(DEBUG)
2982 if (RtsFlags.DebugFlags.gc)
2983 /* Debugging code to print out the size of the thing we just
2987 StgPtr start = gen->steps[0].scan;
2988 bdescr *start_bd = gen->steps[0].scan_bd;
2990 scavenge(&gen->steps[0]);
2991 if (start_bd != gen->steps[0].scan_bd) {
2992 size += (P_)BLOCK_ROUND_UP(start) - start;
2993 start_bd = start_bd->link;
2994 while (start_bd != gen->steps[0].scan_bd) {
2995 size += BLOCK_SIZE_W;
2996 start_bd = start_bd->link;
2998 size += gen->steps[0].scan -
2999 (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
3001 size = gen->steps[0].scan - start;
3003 belch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
3007 /* failed_to_evac might happen if we've got more than two
3008 * generations, we're collecting only generation 0, the
3009 * indirection resides in generation 2 and the indirectee is
3012 if (failed_to_evac) {
3013 failed_to_evac = rtsFalse;
3014 p->mut_link = new_list;
3017 /* the mut_link field of an IND_STATIC is overloaded as the
3018 * static link field too (it just so happens that we don't need
3019 * both at the same time), so we need to NULL it out when
3020 * removing this object from the mutable list because the static
3021 * link fields are all assumed to be NULL before doing a major
3029 /* MUT_CONS is a kind of MUT_VAR, except it that we try to remove
3030 * it from the mutable list if possible by promoting whatever it
3033 if (scavenge_one((StgPtr)((StgMutVar *)p)->var)) {
3034 /* didn't manage to promote everything, so put the
3035 * MUT_CONS back on the list.
3037 p->mut_link = new_list;
3043 // shouldn't have anything else on the mutables list
3044 barf("scavenge_mut_once_list: strange object? %d", (int)(info->type));
3048 gen->mut_once_list = new_list;
3053 scavenge_mutable_list(generation *gen)
3055 const StgInfoTable *info;
3056 StgMutClosure *p, *next;
3058 p = gen->saved_mut_list;
3062 failed_to_evac = rtsFalse;
3064 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
3066 // make sure the info pointer is into text space
3067 ASSERT(p && (LOOKS_LIKE_GHC_INFO(GET_INFO(p))
3068 || IS_HUGS_CONSTR_INFO(GET_INFO(p))));
3072 if (info->type==RBH)
3073 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3075 switch(info->type) {
3078 // follow everything
3079 p->mut_link = gen->mut_list;
3084 end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3085 for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
3086 (StgClosure *)*q = evacuate((StgClosure *)*q);
3091 // Happens if a MUT_ARR_PTRS in the old generation is frozen
3092 case MUT_ARR_PTRS_FROZEN:
3097 end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3098 for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
3099 (StgClosure *)*q = evacuate((StgClosure *)*q);
3103 if (failed_to_evac) {
3104 failed_to_evac = rtsFalse;
3105 mkMutCons((StgClosure *)p, gen);
3111 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3112 p->mut_link = gen->mut_list;
3118 StgMVar *mvar = (StgMVar *)p;
3119 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
3120 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
3121 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
3122 p->mut_link = gen->mut_list;
3129 StgTSO *tso = (StgTSO *)p;
3133 /* Don't take this TSO off the mutable list - it might still
3134 * point to some younger objects (because we set evac_gen to 0
3137 tso->mut_link = gen->mut_list;
3138 gen->mut_list = (StgMutClosure *)tso;
3144 StgBlockingQueue *bh = (StgBlockingQueue *)p;
3145 (StgClosure *)bh->blocking_queue =
3146 evacuate((StgClosure *)bh->blocking_queue);
3147 p->mut_link = gen->mut_list;
3152 /* Happens if a BLACKHOLE_BQ in the old generation is updated:
3155 case IND_OLDGEN_PERM:
3156 /* Try to pull the indirectee into this generation, so we can
3157 * remove the indirection from the mutable list.
3160 ((StgIndOldGen *)p)->indirectee =
3161 evacuate(((StgIndOldGen *)p)->indirectee);
3164 if (failed_to_evac) {
3165 failed_to_evac = rtsFalse;
3166 p->mut_link = gen->mut_once_list;
3167 gen->mut_once_list = p;
3174 // HWL: check whether all of these are necessary
3176 case RBH: // cf. BLACKHOLE_BQ
3178 // nat size, ptrs, nonptrs, vhs;
3180 // StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3181 StgRBH *rbh = (StgRBH *)p;
3182 (StgClosure *)rbh->blocking_queue =
3183 evacuate((StgClosure *)rbh->blocking_queue);
3184 if (failed_to_evac) {
3185 failed_to_evac = rtsFalse;
3186 recordMutable((StgMutClosure *)rbh);
3188 // ToDo: use size of reverted closure here!
3189 p += BLACKHOLE_sizeW();
3195 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3196 // follow the pointer to the node which is being demanded
3197 (StgClosure *)bf->node =
3198 evacuate((StgClosure *)bf->node);
3199 // follow the link to the rest of the blocking queue
3200 (StgClosure *)bf->link =
3201 evacuate((StgClosure *)bf->link);
3202 if (failed_to_evac) {
3203 failed_to_evac = rtsFalse;
3204 recordMutable((StgMutClosure *)bf);
3206 p += sizeofW(StgBlockedFetch);
3212 barf("scavenge_mutable_list: REMOTE_REF %d", (int)(info->type));
3215 p += sizeofW(StgFetchMe);
3216 break; // nothing to do in this case
3218 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
3220 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3221 (StgClosure *)fmbq->blocking_queue =
3222 evacuate((StgClosure *)fmbq->blocking_queue);
3223 if (failed_to_evac) {
3224 failed_to_evac = rtsFalse;
3225 recordMutable((StgMutClosure *)fmbq);
3227 p += sizeofW(StgFetchMeBlockingQueue);
3233 // shouldn't have anything else on the mutables list
3234 barf("scavenge_mutable_list: strange object? %d", (int)(info->type));
3241 scavenge_static(void)
3243 StgClosure* p = static_objects;
3244 const StgInfoTable *info;
3246 /* Always evacuate straight to the oldest generation for static
3248 evac_gen = oldest_gen->no;
3250 /* keep going until we've scavenged all the objects on the linked
3252 while (p != END_OF_STATIC_LIST) {
3256 if (info->type==RBH)
3257 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3259 // make sure the info pointer is into text space
3260 ASSERT(p && (LOOKS_LIKE_GHC_INFO(GET_INFO(p))
3261 || IS_HUGS_CONSTR_INFO(GET_INFO(p))));
3263 /* Take this object *off* the static_objects list,
3264 * and put it on the scavenged_static_objects list.
3266 static_objects = STATIC_LINK(info,p);
3267 STATIC_LINK(info,p) = scavenged_static_objects;
3268 scavenged_static_objects = p;
3270 switch (info -> type) {
3274 StgInd *ind = (StgInd *)p;
3275 ind->indirectee = evacuate(ind->indirectee);
3277 /* might fail to evacuate it, in which case we have to pop it
3278 * back on the mutable list (and take it off the
3279 * scavenged_static list because the static link and mut link
3280 * pointers are one and the same).
3282 if (failed_to_evac) {
3283 failed_to_evac = rtsFalse;
3284 scavenged_static_objects = IND_STATIC_LINK(p);
3285 ((StgMutClosure *)ind)->mut_link = oldest_gen->mut_once_list;
3286 oldest_gen->mut_once_list = (StgMutClosure *)ind;
3300 next = (P_)p->payload + info->layout.payload.ptrs;
3301 // evacuate the pointers
3302 for (q = (P_)p->payload; q < next; q++) {
3303 (StgClosure *)*q = evacuate((StgClosure *)*q);
3309 barf("scavenge_static: strange closure %d", (int)(info->type));
3312 ASSERT(failed_to_evac == rtsFalse);
3314 /* get the next static object from the list. Remember, there might
3315 * be more stuff on this list now that we've done some evacuating!
3316 * (static_objects is a global)
3322 /* -----------------------------------------------------------------------------
3323 scavenge_stack walks over a section of stack and evacuates all the
3324 objects pointed to by it. We can use the same code for walking
3325 PAPs, since these are just sections of copied stack.
3326 -------------------------------------------------------------------------- */
3329 scavenge_stack(StgPtr p, StgPtr stack_end)
3332 const StgInfoTable* info;
3335 //IF_DEBUG(sanity, belch(" scavenging stack between %p and %p", p, stack_end));
3338 * Each time around this loop, we are looking at a chunk of stack
3339 * that starts with either a pending argument section or an
3340 * activation record.
3343 while (p < stack_end) {
3346 // If we've got a tag, skip over that many words on the stack
3347 if (IS_ARG_TAG((W_)q)) {
3352 /* Is q a pointer to a closure?
3354 if (! LOOKS_LIKE_GHC_INFO(q) ) {
3356 if ( 0 && LOOKS_LIKE_STATIC_CLOSURE(q) ) { // Is it a static closure?
3357 ASSERT(closure_STATIC((StgClosure *)q));
3359 // otherwise, must be a pointer into the allocation space.
3362 (StgClosure *)*p = evacuate((StgClosure *)q);
3368 * Otherwise, q must be the info pointer of an activation
3369 * record. All activation records have 'bitmap' style layout
3372 info = get_itbl((StgClosure *)p);
3374 switch (info->type) {
3376 // Dynamic bitmap: the mask is stored on the stack
3378 bitmap = ((StgRetDyn *)p)->liveness;
3379 p = (P_)&((StgRetDyn *)p)->payload[0];
3382 // probably a slow-entry point return address:
3390 belch("HWL: scavenge_stack: FUN(_STATIC) adjusting p from %p to %p (instead of %p)",
3391 old_p, p, old_p+1));
3393 p++; // what if FHS!=1 !? -- HWL
3398 /* Specialised code for update frames, since they're so common.
3399 * We *know* the updatee points to a BLACKHOLE, CAF_BLACKHOLE,
3400 * or BLACKHOLE_BQ, so just inline the code to evacuate it here.
3404 StgUpdateFrame *frame = (StgUpdateFrame *)p;
3406 p += sizeofW(StgUpdateFrame);
3409 frame->updatee = evacuate(frame->updatee);
3411 #else // specialised code for update frames, not sure if it's worth it.
3413 nat type = get_itbl(frame->updatee)->type;
3415 if (type == EVACUATED) {
3416 frame->updatee = evacuate(frame->updatee);
3419 bdescr *bd = Bdescr((P_)frame->updatee);
3421 if (bd->gen_no > N) {
3422 if (bd->gen_no < evac_gen) {
3423 failed_to_evac = rtsTrue;
3428 // Don't promote blackholes
3430 if (!(stp->gen_no == 0 &&
3432 stp->no == stp->gen->n_steps-1)) {
3439 to = copyPart(frame->updatee, BLACKHOLE_sizeW(),
3440 sizeofW(StgHeader), stp);
3441 frame->updatee = to;
3444 to = copy(frame->updatee, BLACKHOLE_sizeW(), stp);
3445 frame->updatee = to;
3446 recordMutable((StgMutClosure *)to);
3449 /* will never be SE_{,CAF_}BLACKHOLE, since we
3450 don't push an update frame for single-entry thunks. KSW 1999-01. */
3451 barf("scavenge_stack: UPDATE_FRAME updatee");
3457 // small bitmap (< 32 entries, or 64 on a 64-bit machine)
3464 bitmap = info->layout.bitmap;
3466 // this assumes that the payload starts immediately after the info-ptr
3468 while (bitmap != 0) {
3469 if ((bitmap & 1) == 0) {
3470 (StgClosure *)*p = evacuate((StgClosure *)*p);
3473 bitmap = bitmap >> 1;
3480 // large bitmap (> 32 entries, or > 64 on a 64-bit machine)
3485 StgLargeBitmap *large_bitmap;
3488 large_bitmap = info->layout.large_bitmap;
3491 for (i=0; i<large_bitmap->size; i++) {
3492 bitmap = large_bitmap->bitmap[i];
3493 q = p + BITS_IN(W_);
3494 while (bitmap != 0) {
3495 if ((bitmap & 1) == 0) {
3496 (StgClosure *)*p = evacuate((StgClosure *)*p);
3499 bitmap = bitmap >> 1;
3501 if (i+1 < large_bitmap->size) {
3503 (StgClosure *)*p = evacuate((StgClosure *)*p);
3509 // and don't forget to follow the SRT
3514 barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->type));
3519 /*-----------------------------------------------------------------------------
3520 scavenge the large object list.
3522 evac_gen set by caller; similar games played with evac_gen as with
3523 scavenge() - see comment at the top of scavenge(). Most large
3524 objects are (repeatedly) mutable, so most of the time evac_gen will
3526 --------------------------------------------------------------------------- */
3529 scavenge_large(step *stp)
3534 bd = stp->new_large_objects;
3536 for (; bd != NULL; bd = stp->new_large_objects) {
3538 /* take this object *off* the large objects list and put it on
3539 * the scavenged large objects list. This is so that we can
3540 * treat new_large_objects as a stack and push new objects on
3541 * the front when evacuating.
3543 stp->new_large_objects = bd->link;
3544 dbl_link_onto(bd, &stp->scavenged_large_objects);
3546 // update the block count in this step.
3547 stp->n_scavenged_large_blocks += bd->blocks;
3550 if (scavenge_one(p)) {
3551 mkMutCons((StgClosure *)p, stp->gen);
3556 /* -----------------------------------------------------------------------------
3557 Initialising the static object & mutable lists
3558 -------------------------------------------------------------------------- */
3561 zero_static_object_list(StgClosure* first_static)
3565 const StgInfoTable *info;
3567 for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
3569 link = STATIC_LINK(info, p);
3570 STATIC_LINK(info,p) = NULL;
3574 /* This function is only needed because we share the mutable link
3575 * field with the static link field in an IND_STATIC, so we have to
3576 * zero the mut_link field before doing a major GC, which needs the
3577 * static link field.
3579 * It doesn't do any harm to zero all the mutable link fields on the
3584 zero_mutable_list( StgMutClosure *first )
3586 StgMutClosure *next, *c;
3588 for (c = first; c != END_MUT_LIST; c = next) {
3594 /* -----------------------------------------------------------------------------
3596 -------------------------------------------------------------------------- */
3603 for (c = (StgIndStatic *)caf_list; c != NULL;
3604 c = (StgIndStatic *)c->static_link)
3606 c->header.info = c->saved_info;
3607 c->saved_info = NULL;
3608 // could, but not necessary: c->static_link = NULL;
3614 markCAFs( evac_fn evac )
3618 for (c = (StgIndStatic *)caf_list; c != NULL;
3619 c = (StgIndStatic *)c->static_link)
3621 evac(&c->indirectee);
3625 /* -----------------------------------------------------------------------------
3626 Sanity code for CAF garbage collection.
3628 With DEBUG turned on, we manage a CAF list in addition to the SRT
3629 mechanism. After GC, we run down the CAF list and blackhole any
3630 CAFs which have been garbage collected. This means we get an error
3631 whenever the program tries to enter a garbage collected CAF.
3633 Any garbage collected CAFs are taken off the CAF list at the same
3635 -------------------------------------------------------------------------- */
3637 #if 0 && defined(DEBUG)
3644 const StgInfoTable *info;
3655 ASSERT(info->type == IND_STATIC);
3657 if (STATIC_LINK(info,p) == NULL) {
3658 IF_DEBUG(gccafs, belch("CAF gc'd at 0x%04lx", (long)p));
3660 SET_INFO(p,&stg_BLACKHOLE_info);
3661 p = STATIC_LINK2(info,p);
3665 pp = &STATIC_LINK2(info,p);
3672 // belch("%d CAFs live", i);
3677 /* -----------------------------------------------------------------------------
3680 Whenever a thread returns to the scheduler after possibly doing
3681 some work, we have to run down the stack and black-hole all the
3682 closures referred to by update frames.
3683 -------------------------------------------------------------------------- */
3686 threadLazyBlackHole(StgTSO *tso)
3688 StgUpdateFrame *update_frame;
3689 StgBlockingQueue *bh;
3692 stack_end = &tso->stack[tso->stack_size];
3693 update_frame = tso->su;
3696 switch (get_itbl(update_frame)->type) {
3699 update_frame = ((StgCatchFrame *)update_frame)->link;
3703 bh = (StgBlockingQueue *)update_frame->updatee;
3705 /* if the thunk is already blackholed, it means we've also
3706 * already blackholed the rest of the thunks on this stack,
3707 * so we can stop early.
3709 * The blackhole made for a CAF is a CAF_BLACKHOLE, so they
3710 * don't interfere with this optimisation.
3712 if (bh->header.info == &stg_BLACKHOLE_info) {
3716 if (bh->header.info != &stg_BLACKHOLE_BQ_info &&
3717 bh->header.info != &stg_CAF_BLACKHOLE_info) {
3718 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
3719 belch("Unexpected lazy BHing required at 0x%04x",(int)bh);
3723 // We pretend that bh is now dead.
3724 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
3726 SET_INFO(bh,&stg_BLACKHOLE_info);
3729 // We pretend that bh has just been created.
3730 LDV_recordCreate(bh);
3734 update_frame = update_frame->link;
3738 update_frame = ((StgSeqFrame *)update_frame)->link;
3744 barf("threadPaused");
3750 /* -----------------------------------------------------------------------------
3753 * Code largely pinched from old RTS, then hacked to bits. We also do
3754 * lazy black holing here.
3756 * -------------------------------------------------------------------------- */
3759 threadSqueezeStack(StgTSO *tso)
3761 lnat displacement = 0;
3762 StgUpdateFrame *frame;
3763 StgUpdateFrame *next_frame; // Temporally next
3764 StgUpdateFrame *prev_frame; // Temporally previous
3766 rtsBool prev_was_update_frame;
3768 StgUpdateFrame *top_frame;
3769 nat upd_frames=0, stop_frames=0, catch_frames=0, seq_frames=0,
3771 void printObj( StgClosure *obj ); // from Printer.c
3773 top_frame = tso->su;
3776 bottom = &(tso->stack[tso->stack_size]);
3779 /* There must be at least one frame, namely the STOP_FRAME.
3781 ASSERT((P_)frame < bottom);
3783 /* Walk down the stack, reversing the links between frames so that
3784 * we can walk back up as we squeeze from the bottom. Note that
3785 * next_frame and prev_frame refer to next and previous as they were
3786 * added to the stack, rather than the way we see them in this
3787 * walk. (It makes the next loop less confusing.)
3789 * Stop if we find an update frame pointing to a black hole
3790 * (see comment in threadLazyBlackHole()).
3794 // bottom - sizeof(StgStopFrame) is the STOP_FRAME
3795 while ((P_)frame < bottom - sizeofW(StgStopFrame)) {
3796 prev_frame = frame->link;
3797 frame->link = next_frame;
3802 if (!(frame>=top_frame && frame<=(StgUpdateFrame *)bottom)) {
3803 printObj((StgClosure *)prev_frame);
3804 barf("threadSqueezeStack: current frame is rubbish %p; previous was %p\n",
3807 switch (get_itbl(frame)->type) {
3810 if (frame->updatee->header.info == &stg_BLACKHOLE_info)
3823 barf("Found non-frame during stack squeezing at %p (prev frame was %p)\n",
3825 printObj((StgClosure *)prev_frame);
3828 if (get_itbl(frame)->type == UPDATE_FRAME
3829 && frame->updatee->header.info == &stg_BLACKHOLE_info) {
3834 /* Now, we're at the bottom. Frame points to the lowest update
3835 * frame on the stack, and its link actually points to the frame
3836 * above. We have to walk back up the stack, squeezing out empty
3837 * update frames and turning the pointers back around on the way
3840 * The bottom-most frame (the STOP_FRAME) has not been altered, and
3841 * we never want to eliminate it anyway. Just walk one step up
3842 * before starting to squeeze. When you get to the topmost frame,
3843 * remember that there are still some words above it that might have
3850 prev_was_update_frame = (get_itbl(prev_frame)->type == UPDATE_FRAME);
3853 * Loop through all of the frames (everything except the very
3854 * bottom). Things are complicated by the fact that we have
3855 * CATCH_FRAMEs and SEQ_FRAMEs interspersed with the update frames.
3856 * We can only squeeze when there are two consecutive UPDATE_FRAMEs.
3858 while (frame != NULL) {
3860 StgPtr frame_bottom = (P_)frame + sizeofW(StgUpdateFrame);
3861 rtsBool is_update_frame;
3863 next_frame = frame->link;
3864 is_update_frame = (get_itbl(frame)->type == UPDATE_FRAME);
3867 * 1. both the previous and current frame are update frames
3868 * 2. the current frame is empty
3870 if (prev_was_update_frame && is_update_frame &&
3871 (P_)prev_frame == frame_bottom + displacement) {
3873 // Now squeeze out the current frame
3874 StgClosure *updatee_keep = prev_frame->updatee;
3875 StgClosure *updatee_bypass = frame->updatee;
3878 IF_DEBUG(gc, belch("@@ squeezing frame at %p", frame));
3882 /* Deal with blocking queues. If both updatees have blocked
3883 * threads, then we should merge the queues into the update
3884 * frame that we're keeping.
3886 * Alternatively, we could just wake them up: they'll just go
3887 * straight to sleep on the proper blackhole! This is less code
3888 * and probably less bug prone, although it's probably much
3891 #if 0 // do it properly...
3892 # if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
3893 # error Unimplemented lazy BH warning. (KSW 1999-01)
3895 if (GET_INFO(updatee_bypass) == stg_BLACKHOLE_BQ_info
3896 || GET_INFO(updatee_bypass) == stg_CAF_BLACKHOLE_info
3898 // Sigh. It has one. Don't lose those threads!
3899 if (GET_INFO(updatee_keep) == stg_BLACKHOLE_BQ_info) {
3900 // Urgh. Two queues. Merge them.
3901 P_ keep_tso = ((StgBlockingQueue *)updatee_keep)->blocking_queue;
3903 while (keep_tso->link != END_TSO_QUEUE) {
3904 keep_tso = keep_tso->link;
3906 keep_tso->link = ((StgBlockingQueue *)updatee_bypass)->blocking_queue;
3909 // For simplicity, just swap the BQ for the BH
3910 P_ temp = updatee_keep;
3912 updatee_keep = updatee_bypass;
3913 updatee_bypass = temp;
3915 // Record the swap in the kept frame (below)
3916 prev_frame->updatee = updatee_keep;
3921 TICK_UPD_SQUEEZED();
3922 /* wasn't there something about update squeezing and ticky to be
3923 * sorted out? oh yes: we aren't counting each enter properly
3924 * in this case. See the log somewhere. KSW 1999-04-21
3926 * Check two things: that the two update frames don't point to
3927 * the same object, and that the updatee_bypass isn't already an
3928 * indirection. Both of these cases only happen when we're in a
3929 * block hole-style loop (and there are multiple update frames
3930 * on the stack pointing to the same closure), but they can both
3931 * screw us up if we don't check.
3933 if (updatee_bypass != updatee_keep && !closure_IND(updatee_bypass)) {
3934 // this wakes the threads up
3935 UPD_IND_NOLOCK(updatee_bypass, updatee_keep);
3938 sp = (P_)frame - 1; // sp = stuff to slide
3939 displacement += sizeofW(StgUpdateFrame);
3942 // No squeeze for this frame
3943 sp = frame_bottom - 1; // Keep the current frame
3945 /* Do lazy black-holing.
3947 if (is_update_frame) {
3948 StgBlockingQueue *bh = (StgBlockingQueue *)frame->updatee;
3949 if (bh->header.info != &stg_BLACKHOLE_info &&
3950 bh->header.info != &stg_BLACKHOLE_BQ_info &&
3951 bh->header.info != &stg_CAF_BLACKHOLE_info) {
3952 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
3953 belch("Unexpected lazy BHing required at 0x%04x",(int)bh);
3956 /* zero out the slop so that the sanity checker can tell
3957 * where the next closure is.
3960 StgInfoTable *info = get_itbl(bh);
3961 nat np = info->layout.payload.ptrs, nw = info->layout.payload.nptrs, i;
3962 /* don't zero out slop for a THUNK_SELECTOR, because its layout
3963 * info is used for a different purpose, and it's exactly the
3964 * same size as a BLACKHOLE in any case.
3966 if (info->type != THUNK_SELECTOR) {
3967 for (i = np; i < np + nw; i++) {
3968 ((StgClosure *)bh)->payload[i] = 0;
3975 // We pretend that bh is now dead.
3976 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
3979 // Todo: maybe use SET_HDR() and remove LDV_recordCreate()?
3981 SET_INFO(bh,&stg_BLACKHOLE_info);
3984 // We pretend that bh has just been created.
3985 LDV_recordCreate(bh);
3990 // Fix the link in the current frame (should point to the frame below)
3991 frame->link = prev_frame;
3992 prev_was_update_frame = is_update_frame;
3995 // Now slide all words from sp up to the next frame
3997 if (displacement > 0) {
3998 P_ next_frame_bottom;
4000 if (next_frame != NULL)
4001 next_frame_bottom = (P_)next_frame + sizeofW(StgUpdateFrame);
4003 next_frame_bottom = tso->sp - 1;
4007 belch("sliding [%p, %p] by %ld", sp, next_frame_bottom,
4011 while (sp >= next_frame_bottom) {
4012 sp[displacement] = *sp;
4016 (P_)prev_frame = (P_)frame + displacement;
4020 tso->sp += displacement;
4021 tso->su = prev_frame;
4024 belch("@@ threadSqueezeStack: squeezed %d update-frames; found %d BHs; found %d update-, %d stop-, %d catch, %d seq-frames",
4025 squeezes, bhs, upd_frames, stop_frames, catch_frames, seq_frames))
4030 /* -----------------------------------------------------------------------------
4033 * We have to prepare for GC - this means doing lazy black holing
4034 * here. We also take the opportunity to do stack squeezing if it's
4036 * -------------------------------------------------------------------------- */
4038 threadPaused(StgTSO *tso)
4040 if ( RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue )
4041 threadSqueezeStack(tso); // does black holing too
4043 threadLazyBlackHole(tso);
4046 /* -----------------------------------------------------------------------------
4048 * -------------------------------------------------------------------------- */
4052 printMutOnceList(generation *gen)
4054 StgMutClosure *p, *next;
4056 p = gen->mut_once_list;
4059 fprintf(stderr, "@@ Mut once list %p: ", gen->mut_once_list);
4060 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
4061 fprintf(stderr, "%p (%s), ",
4062 p, info_type((StgClosure *)p));
4064 fputc('\n', stderr);
4068 printMutableList(generation *gen)
4070 StgMutClosure *p, *next;
4075 fprintf(stderr, "@@ Mutable list %p: ", gen->mut_list);
4076 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
4077 fprintf(stderr, "%p (%s), ",
4078 p, info_type((StgClosure *)p));
4080 fputc('\n', stderr);
4083 static inline rtsBool
4084 maybeLarge(StgClosure *closure)
4086 StgInfoTable *info = get_itbl(closure);
4088 /* closure types that may be found on the new_large_objects list;
4089 see scavenge_large */
4090 return (info->type == MUT_ARR_PTRS ||
4091 info->type == MUT_ARR_PTRS_FROZEN ||
4092 info->type == TSO ||
4093 info->type == ARR_WORDS);