1 /* -----------------------------------------------------------------------------
3 * (c) The GHC Team 1998-2003
5 * Generational garbage collector
7 * ---------------------------------------------------------------------------*/
9 #include "PosixSource.h"
14 #include "OSThreads.h"
16 #include "LdvProfile.h"
21 #include "BlockAlloc.h"
27 #include "ParTicky.h" // ToDo: move into Rts.h
28 #include "GCCompact.h"
29 #include "RtsSignals.h"
31 #if defined(GRAN) || defined(PAR)
32 # include "GranSimRts.h"
33 # include "ParallelRts.h"
37 # include "ParallelDebug.h"
42 #if defined(RTS_GTK_FRONTPANEL)
43 #include "FrontPanel.h"
46 #include "RetainerProfile.h"
50 // Turn off inlining when debugging - it obfuscates things
53 # define STATIC_INLINE static
56 /* STATIC OBJECT LIST.
59 * We maintain a linked list of static objects that are still live.
60 * The requirements for this list are:
62 * - we need to scan the list while adding to it, in order to
63 * scavenge all the static objects (in the same way that
64 * breadth-first scavenging works for dynamic objects).
66 * - we need to be able to tell whether an object is already on
67 * the list, to break loops.
69 * Each static object has a "static link field", which we use for
70 * linking objects on to the list. We use a stack-type list, consing
71 * objects on the front as they are added (this means that the
72 * scavenge phase is depth-first, not breadth-first, but that
75 * A separate list is kept for objects that have been scavenged
76 * already - this is so that we can zero all the marks afterwards.
78 * An object is on the list if its static link field is non-zero; this
79 * means that we have to mark the end of the list with '1', not NULL.
81 * Extra notes for generational GC:
83 * Each generation has a static object list associated with it. When
84 * collecting generations up to N, we treat the static object lists
85 * from generations > N as roots.
87 * We build up a static object list while collecting generations 0..N,
88 * which is then appended to the static object list of generation N+1.
90 static StgClosure* static_objects; // live static objects
91 StgClosure* scavenged_static_objects; // static objects scavenged so far
93 /* N is the oldest generation being collected, where the generations
94 * are numbered starting at 0. A major GC (indicated by the major_gc
95 * flag) is when we're collecting all generations. We only attempt to
96 * deal with static objects and GC CAFs when doing a major GC.
99 static rtsBool major_gc;
101 /* Youngest generation that objects should be evacuated to in
102 * evacuate(). (Logically an argument to evacuate, but it's static
103 * a lot of the time so we optimise it into a global variable).
109 StgWeak *old_weak_ptr_list; // also pending finaliser list
111 /* Which stage of processing various kinds of weak pointer are we at?
112 * (see traverse_weak_ptr_list() below for discussion).
114 typedef enum { WeakPtrs, WeakThreads, WeakDone } WeakStage;
115 static WeakStage weak_stage;
117 /* List of all threads during GC
119 static StgTSO *old_all_threads;
120 StgTSO *resurrected_threads;
122 /* Flag indicating failure to evacuate an object to the desired
125 static rtsBool failed_to_evac;
127 /* Saved nursery (used for 2-space collector only)
129 static bdescr *saved_nursery;
130 static nat saved_n_blocks;
132 /* Data used for allocation area sizing.
134 static lnat new_blocks; // blocks allocated during this GC
135 static lnat new_scavd_blocks; // ditto, but depth-first blocks
136 static lnat g0s0_pcnt_kept = 30; // percentage of g0s0 live at last minor GC
138 /* Used to avoid long recursion due to selector thunks
140 static lnat thunk_selector_depth = 0;
141 #define MAX_THUNK_SELECTOR_DEPTH 8
143 /* -----------------------------------------------------------------------------
144 Static function declarations
145 -------------------------------------------------------------------------- */
147 static bdescr * gc_alloc_block ( step *stp );
148 static void mark_root ( StgClosure **root );
150 // Use a register argument for evacuate, if available.
152 #define REGPARM1 __attribute__((regparm(1)))
157 REGPARM1 static StgClosure * evacuate (StgClosure *q);
159 static void zero_static_object_list ( StgClosure* first_static );
161 static rtsBool traverse_weak_ptr_list ( void );
162 static void mark_weak_ptr_list ( StgWeak **list );
164 static StgClosure * eval_thunk_selector ( nat field, StgSelector * p );
167 static void scavenge ( step * );
168 static void scavenge_mark_stack ( void );
169 static void scavenge_stack ( StgPtr p, StgPtr stack_end );
170 static rtsBool scavenge_one ( StgPtr p );
171 static void scavenge_large ( step * );
172 static void scavenge_static ( void );
173 static void scavenge_mutable_list ( generation *g );
175 static void scavenge_large_bitmap ( StgPtr p,
176 StgLargeBitmap *large_bitmap,
179 #if 0 && defined(DEBUG)
180 static void gcCAFs ( void );
183 /* -----------------------------------------------------------------------------
184 inline functions etc. for dealing with the mark bitmap & stack.
185 -------------------------------------------------------------------------- */
187 #define MARK_STACK_BLOCKS 4
189 static bdescr *mark_stack_bdescr;
190 static StgPtr *mark_stack;
191 static StgPtr *mark_sp;
192 static StgPtr *mark_splim;
194 // Flag and pointers used for falling back to a linear scan when the
195 // mark stack overflows.
196 static rtsBool mark_stack_overflowed;
197 static bdescr *oldgen_scan_bd;
198 static StgPtr oldgen_scan;
200 STATIC_INLINE rtsBool
201 mark_stack_empty(void)
203 return mark_sp == mark_stack;
206 STATIC_INLINE rtsBool
207 mark_stack_full(void)
209 return mark_sp >= mark_splim;
213 reset_mark_stack(void)
215 mark_sp = mark_stack;
219 push_mark_stack(StgPtr p)
230 /* -----------------------------------------------------------------------------
231 Allocate a new to-space block in the given step.
232 -------------------------------------------------------------------------- */
235 gc_alloc_block(step *stp)
237 bdescr *bd = allocBlock();
238 bd->gen_no = stp->gen_no;
242 // blocks in to-space in generations up to and including N
243 // get the BF_EVACUATED flag.
244 if (stp->gen_no <= N) {
245 bd->flags = BF_EVACUATED;
250 // Start a new to-space block, chain it on after the previous one.
251 if (stp->hp_bd != NULL) {
252 stp->hp_bd->free = stp->hp;
253 stp->hp_bd->link = bd;
258 stp->hpLim = stp->hp + BLOCK_SIZE_W;
267 gc_alloc_scavd_block(step *stp)
269 bdescr *bd = allocBlock();
270 bd->gen_no = stp->gen_no;
273 // blocks in to-space in generations up to and including N
274 // get the BF_EVACUATED flag.
275 if (stp->gen_no <= N) {
276 bd->flags = BF_EVACUATED;
281 bd->link = stp->blocks;
284 if (stp->scavd_hp != NULL) {
285 Bdescr(stp->scavd_hp)->free = stp->scavd_hp;
287 stp->scavd_hp = bd->start;
288 stp->scavd_hpLim = stp->scavd_hp + BLOCK_SIZE_W;
296 /* -----------------------------------------------------------------------------
299 Rough outline of the algorithm: for garbage collecting generation N
300 (and all younger generations):
302 - follow all pointers in the root set. the root set includes all
303 mutable objects in all generations (mutable_list).
305 - for each pointer, evacuate the object it points to into either
307 + to-space of the step given by step->to, which is the next
308 highest step in this generation or the first step in the next
309 generation if this is the last step.
311 + to-space of generations[evac_gen]->steps[0], if evac_gen != 0.
312 When we evacuate an object we attempt to evacuate
313 everything it points to into the same generation - this is
314 achieved by setting evac_gen to the desired generation. If
315 we can't do this, then an entry in the mut list has to
316 be made for the cross-generation pointer.
318 + if the object is already in a generation > N, then leave
321 - repeatedly scavenge to-space from each step in each generation
322 being collected until no more objects can be evacuated.
324 - free from-space in each step, and set from-space = to-space.
326 Locks held: all capabilities are held throughout GarbageCollect().
328 -------------------------------------------------------------------------- */
331 GarbageCollect ( void (*get_roots)(evac_fn), rtsBool force_major_gc )
335 lnat live, allocated, collected = 0, copied = 0, scavd_copied = 0;
336 lnat oldgen_saved_blocks = 0;
342 CostCentreStack *prev_CCS;
345 #if defined(DEBUG) && defined(GRAN)
346 IF_DEBUG(gc, debugBelch("@@ Starting garbage collection at %ld (%lx)\n",
350 #if defined(RTS_USER_SIGNALS)
355 // tell the STM to discard any cached closures its hoping to re-use
358 // tell the stats department that we've started a GC
362 // check for memory leaks if DEBUG is on
366 // Init stats and print par specific (timing) info
367 PAR_TICKY_PAR_START();
369 // attribute any costs to CCS_GC
375 /* Approximate how much we allocated.
376 * Todo: only when generating stats?
378 allocated = calcAllocated();
380 /* Figure out which generation to collect
382 if (force_major_gc) {
383 N = RtsFlags.GcFlags.generations - 1;
387 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
388 if (generations[g].steps[0].n_blocks +
389 generations[g].steps[0].n_large_blocks
390 >= generations[g].max_blocks) {
394 major_gc = (N == RtsFlags.GcFlags.generations-1);
397 #ifdef RTS_GTK_FRONTPANEL
398 if (RtsFlags.GcFlags.frontpanel) {
399 updateFrontPanelBeforeGC(N);
403 // check stack sanity *before* GC (ToDo: check all threads)
405 // ToDo!: check sanity IF_DEBUG(sanity, checkTSOsSanity());
407 IF_DEBUG(sanity, checkFreeListSanity());
409 /* Initialise the static object lists
411 static_objects = END_OF_STATIC_LIST;
412 scavenged_static_objects = END_OF_STATIC_LIST;
414 /* Save the nursery if we're doing a two-space collection.
415 * g0s0->blocks will be used for to-space, so we need to get the
416 * nursery out of the way.
418 if (RtsFlags.GcFlags.generations == 1) {
419 saved_nursery = g0s0->blocks;
420 saved_n_blocks = g0s0->n_blocks;
425 /* Keep a count of how many new blocks we allocated during this GC
426 * (used for resizing the allocation area, later).
429 new_scavd_blocks = 0;
431 // Initialise to-space in all the generations/steps that we're
434 for (g = 0; g <= N; g++) {
436 // throw away the mutable list. Invariant: the mutable list
437 // always has at least one block; this means we can avoid a check for
438 // NULL in recordMutable().
440 freeChain(generations[g].mut_list);
441 generations[g].mut_list = allocBlock();
442 for (i = 0; i < n_capabilities; i++) {
443 freeChain(capabilities[i].mut_lists[g]);
444 capabilities[i].mut_lists[g] = allocBlock();
448 for (s = 0; s < generations[g].n_steps; s++) {
450 // generation 0, step 0 doesn't need to-space
451 if (g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1) {
455 stp = &generations[g].steps[s];
456 ASSERT(stp->gen_no == g);
458 // start a new to-space for this step.
459 stp->old_blocks = stp->blocks;
460 stp->n_old_blocks = stp->n_blocks;
462 // allocate the first to-space block; extra blocks will be
463 // chained on as necessary.
465 bd = gc_alloc_block(stp);
468 stp->scan = bd->start;
471 // allocate a block for "already scavenged" objects. This goes
472 // on the front of the stp->blocks list, so it won't be
473 // traversed by the scavenging sweep.
474 gc_alloc_scavd_block(stp);
476 // initialise the large object queues.
477 stp->new_large_objects = NULL;
478 stp->scavenged_large_objects = NULL;
479 stp->n_scavenged_large_blocks = 0;
481 // mark the large objects as not evacuated yet
482 for (bd = stp->large_objects; bd; bd = bd->link) {
483 bd->flags &= ~BF_EVACUATED;
486 // for a compacted step, we need to allocate the bitmap
487 if (stp->is_compacted) {
488 nat bitmap_size; // in bytes
489 bdescr *bitmap_bdescr;
492 bitmap_size = stp->n_old_blocks * BLOCK_SIZE / (sizeof(W_)*BITS_PER_BYTE);
494 if (bitmap_size > 0) {
495 bitmap_bdescr = allocGroup((lnat)BLOCK_ROUND_UP(bitmap_size)
497 stp->bitmap = bitmap_bdescr;
498 bitmap = bitmap_bdescr->start;
500 IF_DEBUG(gc, debugBelch("bitmap_size: %d, bitmap: %p",
501 bitmap_size, bitmap););
503 // don't forget to fill it with zeros!
504 memset(bitmap, 0, bitmap_size);
506 // For each block in this step, point to its bitmap from the
508 for (bd=stp->old_blocks; bd != NULL; bd = bd->link) {
509 bd->u.bitmap = bitmap;
510 bitmap += BLOCK_SIZE_W / (sizeof(W_)*BITS_PER_BYTE);
512 // Also at this point we set the BF_COMPACTED flag
513 // for this block. The invariant is that
514 // BF_COMPACTED is always unset, except during GC
515 // when it is set on those blocks which will be
517 bd->flags |= BF_COMPACTED;
524 /* make sure the older generations have at least one block to
525 * allocate into (this makes things easier for copy(), see below).
527 for (g = N+1; g < RtsFlags.GcFlags.generations; g++) {
528 for (s = 0; s < generations[g].n_steps; s++) {
529 stp = &generations[g].steps[s];
530 if (stp->hp_bd == NULL) {
531 ASSERT(stp->blocks == NULL);
532 bd = gc_alloc_block(stp);
536 if (stp->scavd_hp == NULL) {
537 gc_alloc_scavd_block(stp);
540 /* Set the scan pointer for older generations: remember we
541 * still have to scavenge objects that have been promoted. */
543 stp->scan_bd = stp->hp_bd;
544 stp->new_large_objects = NULL;
545 stp->scavenged_large_objects = NULL;
546 stp->n_scavenged_large_blocks = 0;
549 /* Move the private mutable lists from each capability onto the
550 * main mutable list for the generation.
552 for (i = 0; i < n_capabilities; i++) {
553 for (bd = capabilities[i].mut_lists[g];
554 bd->link != NULL; bd = bd->link) {
557 bd->link = generations[g].mut_list;
558 generations[g].mut_list = capabilities[i].mut_lists[g];
559 capabilities[i].mut_lists[g] = allocBlock();
563 /* Allocate a mark stack if we're doing a major collection.
566 mark_stack_bdescr = allocGroup(MARK_STACK_BLOCKS);
567 mark_stack = (StgPtr *)mark_stack_bdescr->start;
568 mark_sp = mark_stack;
569 mark_splim = mark_stack + (MARK_STACK_BLOCKS * BLOCK_SIZE_W);
571 mark_stack_bdescr = NULL;
574 /* -----------------------------------------------------------------------
575 * follow all the roots that we know about:
576 * - mutable lists from each generation > N
577 * we want to *scavenge* these roots, not evacuate them: they're not
578 * going to move in this GC.
579 * Also: do them in reverse generation order. This is because we
580 * often want to promote objects that are pointed to by older
581 * generations early, so we don't have to repeatedly copy them.
582 * Doing the generations in reverse order ensures that we don't end
583 * up in the situation where we want to evac an object to gen 3 and
584 * it has already been evaced to gen 2.
588 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
589 generations[g].saved_mut_list = generations[g].mut_list;
590 generations[g].mut_list = allocBlock();
591 // mut_list always has at least one block.
594 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
595 IF_PAR_DEBUG(verbose, printMutableList(&generations[g]));
596 scavenge_mutable_list(&generations[g]);
598 for (st = generations[g].n_steps-1; st >= 0; st--) {
599 scavenge(&generations[g].steps[st]);
604 /* follow roots from the CAF list (used by GHCi)
609 /* follow all the roots that the application knows about.
612 get_roots(mark_root);
615 /* And don't forget to mark the TSO if we got here direct from
617 /* Not needed in a seq version?
619 CurrentTSO = (StgTSO *)MarkRoot((StgClosure *)CurrentTSO);
623 // Mark the entries in the GALA table of the parallel system
624 markLocalGAs(major_gc);
625 // Mark all entries on the list of pending fetches
626 markPendingFetches(major_gc);
629 /* Mark the weak pointer list, and prepare to detect dead weak
632 mark_weak_ptr_list(&weak_ptr_list);
633 old_weak_ptr_list = weak_ptr_list;
634 weak_ptr_list = NULL;
635 weak_stage = WeakPtrs;
637 /* The all_threads list is like the weak_ptr_list.
638 * See traverse_weak_ptr_list() for the details.
640 old_all_threads = all_threads;
641 all_threads = END_TSO_QUEUE;
642 resurrected_threads = END_TSO_QUEUE;
644 /* Mark the stable pointer table.
646 markStablePtrTable(mark_root);
648 /* -------------------------------------------------------------------------
649 * Repeatedly scavenge all the areas we know about until there's no
650 * more scavenging to be done.
657 // scavenge static objects
658 if (major_gc && static_objects != END_OF_STATIC_LIST) {
659 IF_DEBUG(sanity, checkStaticObjects(static_objects));
663 /* When scavenging the older generations: Objects may have been
664 * evacuated from generations <= N into older generations, and we
665 * need to scavenge these objects. We're going to try to ensure that
666 * any evacuations that occur move the objects into at least the
667 * same generation as the object being scavenged, otherwise we
668 * have to create new entries on the mutable list for the older
672 // scavenge each step in generations 0..maxgen
678 // scavenge objects in compacted generation
679 if (mark_stack_overflowed || oldgen_scan_bd != NULL ||
680 (mark_stack_bdescr != NULL && !mark_stack_empty())) {
681 scavenge_mark_stack();
685 for (gen = RtsFlags.GcFlags.generations; --gen >= 0; ) {
686 for (st = generations[gen].n_steps; --st >= 0; ) {
687 if (gen == 0 && st == 0 && RtsFlags.GcFlags.generations > 1) {
690 stp = &generations[gen].steps[st];
692 if (stp->hp_bd != stp->scan_bd || stp->scan < stp->hp) {
697 if (stp->new_large_objects != NULL) {
706 if (flag) { goto loop; }
708 // must be last... invariant is that everything is fully
709 // scavenged at this point.
710 if (traverse_weak_ptr_list()) { // returns rtsTrue if evaced something
715 /* Update the pointers from the task list - these are
716 * treated as weak pointers because we want to allow a main thread
717 * to get a BlockedOnDeadMVar exception in the same way as any other
718 * thread. Note that the threads should all have been retained by
719 * GC by virtue of being on the all_threads list, we're just
720 * updating pointers here.
725 for (task = all_tasks; task != NULL; task = task->all_link) {
726 if (!task->stopped && task->tso) {
727 ASSERT(task->tso->bound == task);
728 tso = (StgTSO *) isAlive((StgClosure *)task->tso);
730 barf("task %p: main thread %d has been GC'd",
744 // Reconstruct the Global Address tables used in GUM
745 rebuildGAtables(major_gc);
746 IF_DEBUG(sanity, checkLAGAtable(rtsTrue/*check closures, too*/));
749 // Now see which stable names are still alive.
752 // Tidy the end of the to-space chains
753 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
754 for (s = 0; s < generations[g].n_steps; s++) {
755 stp = &generations[g].steps[s];
756 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
757 ASSERT(Bdescr(stp->hp) == stp->hp_bd);
758 stp->hp_bd->free = stp->hp;
759 Bdescr(stp->scavd_hp)->free = stp->scavd_hp;
765 // We call processHeapClosureForDead() on every closure destroyed during
766 // the current garbage collection, so we invoke LdvCensusForDead().
767 if (RtsFlags.ProfFlags.doHeapProfile == HEAP_BY_LDV
768 || RtsFlags.ProfFlags.bioSelector != NULL)
772 // NO MORE EVACUATION AFTER THIS POINT!
773 // Finally: compaction of the oldest generation.
774 if (major_gc && oldest_gen->steps[0].is_compacted) {
775 // save number of blocks for stats
776 oldgen_saved_blocks = oldest_gen->steps[0].n_old_blocks;
780 IF_DEBUG(sanity, checkGlobalTSOList(rtsFalse));
782 /* run through all the generations/steps and tidy up
784 copied = new_blocks * BLOCK_SIZE_W;
785 scavd_copied = new_scavd_blocks * BLOCK_SIZE_W;
786 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
789 generations[g].collections++; // for stats
792 // Count the mutable list as bytes "copied" for the purposes of
793 // stats. Every mutable list is copied during every GC.
795 for (bd = generations[g].mut_list; bd != NULL; bd = bd->link) {
796 copied += (bd->free - bd->start) * sizeof(StgWord);
800 for (s = 0; s < generations[g].n_steps; s++) {
802 stp = &generations[g].steps[s];
804 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
805 // stats information: how much we copied
807 copied -= stp->hp_bd->start + BLOCK_SIZE_W -
809 scavd_copied -= (P_)(BLOCK_ROUND_UP(stp->scavd_hp)) - stp->scavd_hp;
813 // for generations we collected...
816 // rough calculation of garbage collected, for stats output
817 if (stp->is_compacted) {
818 collected += (oldgen_saved_blocks - stp->n_old_blocks) * BLOCK_SIZE_W;
820 if (g == 0 && s == 0) {
821 collected += countNurseryBlocks() * BLOCK_SIZE_W;
822 collected += alloc_blocks;
824 collected += stp->n_old_blocks * BLOCK_SIZE_W;
828 /* free old memory and shift to-space into from-space for all
829 * the collected steps (except the allocation area). These
830 * freed blocks will probaby be quickly recycled.
832 if (!(g == 0 && s == 0)) {
833 if (stp->is_compacted) {
834 // for a compacted step, just shift the new to-space
835 // onto the front of the now-compacted existing blocks.
836 for (bd = stp->blocks; bd != NULL; bd = bd->link) {
837 bd->flags &= ~BF_EVACUATED; // now from-space
839 // tack the new blocks on the end of the existing blocks
840 if (stp->old_blocks != NULL) {
841 for (bd = stp->old_blocks; bd != NULL; bd = next) {
842 // NB. this step might not be compacted next
843 // time, so reset the BF_COMPACTED flags.
844 // They are set before GC if we're going to
845 // compact. (search for BF_COMPACTED above).
846 bd->flags &= ~BF_COMPACTED;
849 bd->link = stp->blocks;
852 stp->blocks = stp->old_blocks;
854 // add the new blocks to the block tally
855 stp->n_blocks += stp->n_old_blocks;
856 ASSERT(countBlocks(stp->blocks) == stp->n_blocks);
858 freeChain(stp->old_blocks);
859 for (bd = stp->blocks; bd != NULL; bd = bd->link) {
860 bd->flags &= ~BF_EVACUATED; // now from-space
863 stp->old_blocks = NULL;
864 stp->n_old_blocks = 0;
867 /* LARGE OBJECTS. The current live large objects are chained on
868 * scavenged_large, having been moved during garbage
869 * collection from large_objects. Any objects left on
870 * large_objects list are therefore dead, so we free them here.
872 for (bd = stp->large_objects; bd != NULL; bd = next) {
878 // update the count of blocks used by large objects
879 for (bd = stp->scavenged_large_objects; bd != NULL; bd = bd->link) {
880 bd->flags &= ~BF_EVACUATED;
882 stp->large_objects = stp->scavenged_large_objects;
883 stp->n_large_blocks = stp->n_scavenged_large_blocks;
886 // for older generations...
888 /* For older generations, we need to append the
889 * scavenged_large_object list (i.e. large objects that have been
890 * promoted during this GC) to the large_object list for that step.
892 for (bd = stp->scavenged_large_objects; bd; bd = next) {
894 bd->flags &= ~BF_EVACUATED;
895 dbl_link_onto(bd, &stp->large_objects);
898 // add the new blocks we promoted during this GC
899 stp->n_large_blocks += stp->n_scavenged_large_blocks;
904 /* Reset the sizes of the older generations when we do a major
907 * CURRENT STRATEGY: make all generations except zero the same size.
908 * We have to stay within the maximum heap size, and leave a certain
909 * percentage of the maximum heap size available to allocate into.
911 if (major_gc && RtsFlags.GcFlags.generations > 1) {
912 nat live, size, min_alloc;
913 nat max = RtsFlags.GcFlags.maxHeapSize;
914 nat gens = RtsFlags.GcFlags.generations;
916 // live in the oldest generations
917 live = oldest_gen->steps[0].n_blocks +
918 oldest_gen->steps[0].n_large_blocks;
920 // default max size for all generations except zero
921 size = stg_max(live * RtsFlags.GcFlags.oldGenFactor,
922 RtsFlags.GcFlags.minOldGenSize);
924 // minimum size for generation zero
925 min_alloc = stg_max((RtsFlags.GcFlags.pcFreeHeap * max) / 200,
926 RtsFlags.GcFlags.minAllocAreaSize);
928 // Auto-enable compaction when the residency reaches a
929 // certain percentage of the maximum heap size (default: 30%).
930 if (RtsFlags.GcFlags.generations > 1 &&
931 (RtsFlags.GcFlags.compact ||
933 oldest_gen->steps[0].n_blocks >
934 (RtsFlags.GcFlags.compactThreshold * max) / 100))) {
935 oldest_gen->steps[0].is_compacted = 1;
936 // debugBelch("compaction: on\n", live);
938 oldest_gen->steps[0].is_compacted = 0;
939 // debugBelch("compaction: off\n", live);
942 // if we're going to go over the maximum heap size, reduce the
943 // size of the generations accordingly. The calculation is
944 // different if compaction is turned on, because we don't need
945 // to double the space required to collect the old generation.
948 // this test is necessary to ensure that the calculations
949 // below don't have any negative results - we're working
950 // with unsigned values here.
951 if (max < min_alloc) {
955 if (oldest_gen->steps[0].is_compacted) {
956 if ( (size + (size - 1) * (gens - 2) * 2) + min_alloc > max ) {
957 size = (max - min_alloc) / ((gens - 1) * 2 - 1);
960 if ( (size * (gens - 1) * 2) + min_alloc > max ) {
961 size = (max - min_alloc) / ((gens - 1) * 2);
971 debugBelch("live: %d, min_alloc: %d, size : %d, max = %d\n", live,
972 min_alloc, size, max);
975 for (g = 0; g < gens; g++) {
976 generations[g].max_blocks = size;
980 // Guess the amount of live data for stats.
983 /* Free the small objects allocated via allocate(), since this will
984 * all have been copied into G0S1 now.
986 if (small_alloc_list != NULL) {
987 freeChain(small_alloc_list);
989 small_alloc_list = NULL;
993 alloc_blocks_lim = RtsFlags.GcFlags.minAllocAreaSize;
995 // Start a new pinned_object_block
996 pinned_object_block = NULL;
998 /* Free the mark stack.
1000 if (mark_stack_bdescr != NULL) {
1001 freeGroup(mark_stack_bdescr);
1004 /* Free any bitmaps.
1006 for (g = 0; g <= N; g++) {
1007 for (s = 0; s < generations[g].n_steps; s++) {
1008 stp = &generations[g].steps[s];
1009 if (stp->bitmap != NULL) {
1010 freeGroup(stp->bitmap);
1016 /* Two-space collector:
1017 * Free the old to-space, and estimate the amount of live data.
1019 if (RtsFlags.GcFlags.generations == 1) {
1022 if (g0s0->old_blocks != NULL) {
1023 freeChain(g0s0->old_blocks);
1025 for (bd = g0s0->blocks; bd != NULL; bd = bd->link) {
1026 bd->flags = 0; // now from-space
1028 g0s0->old_blocks = g0s0->blocks;
1029 g0s0->n_old_blocks = g0s0->n_blocks;
1030 g0s0->blocks = saved_nursery;
1031 g0s0->n_blocks = saved_n_blocks;
1033 /* For a two-space collector, we need to resize the nursery. */
1035 /* set up a new nursery. Allocate a nursery size based on a
1036 * function of the amount of live data (by default a factor of 2)
1037 * Use the blocks from the old nursery if possible, freeing up any
1040 * If we get near the maximum heap size, then adjust our nursery
1041 * size accordingly. If the nursery is the same size as the live
1042 * data (L), then we need 3L bytes. We can reduce the size of the
1043 * nursery to bring the required memory down near 2L bytes.
1045 * A normal 2-space collector would need 4L bytes to give the same
1046 * performance we get from 3L bytes, reducing to the same
1047 * performance at 2L bytes.
1049 blocks = g0s0->n_old_blocks;
1051 if ( RtsFlags.GcFlags.maxHeapSize != 0 &&
1052 blocks * RtsFlags.GcFlags.oldGenFactor * 2 >
1053 RtsFlags.GcFlags.maxHeapSize ) {
1054 long adjusted_blocks; // signed on purpose
1057 adjusted_blocks = (RtsFlags.GcFlags.maxHeapSize - 2 * blocks);
1058 IF_DEBUG(gc, debugBelch("@@ Near maximum heap size of 0x%x blocks, blocks = %d, adjusted to %ld", RtsFlags.GcFlags.maxHeapSize, blocks, adjusted_blocks));
1059 pc_free = adjusted_blocks * 100 / RtsFlags.GcFlags.maxHeapSize;
1060 if (pc_free < RtsFlags.GcFlags.pcFreeHeap) /* might even be < 0 */ {
1063 blocks = adjusted_blocks;
1066 blocks *= RtsFlags.GcFlags.oldGenFactor;
1067 if (blocks < RtsFlags.GcFlags.minAllocAreaSize) {
1068 blocks = RtsFlags.GcFlags.minAllocAreaSize;
1071 resizeNurseries(blocks);
1074 /* Generational collector:
1075 * If the user has given us a suggested heap size, adjust our
1076 * allocation area to make best use of the memory available.
1079 if (RtsFlags.GcFlags.heapSizeSuggestion) {
1081 nat needed = calcNeeded(); // approx blocks needed at next GC
1083 /* Guess how much will be live in generation 0 step 0 next time.
1084 * A good approximation is obtained by finding the
1085 * percentage of g0s0 that was live at the last minor GC.
1088 g0s0_pcnt_kept = (new_blocks * 100) / countNurseryBlocks();
1091 /* Estimate a size for the allocation area based on the
1092 * information available. We might end up going slightly under
1093 * or over the suggested heap size, but we should be pretty
1096 * Formula: suggested - needed
1097 * ----------------------------
1098 * 1 + g0s0_pcnt_kept/100
1100 * where 'needed' is the amount of memory needed at the next
1101 * collection for collecting all steps except g0s0.
1104 (((long)RtsFlags.GcFlags.heapSizeSuggestion - (long)needed) * 100) /
1105 (100 + (long)g0s0_pcnt_kept);
1107 if (blocks < (long)RtsFlags.GcFlags.minAllocAreaSize) {
1108 blocks = RtsFlags.GcFlags.minAllocAreaSize;
1111 resizeNurseries((nat)blocks);
1114 // we might have added extra large blocks to the nursery, so
1115 // resize back to minAllocAreaSize again.
1116 resizeNurseriesFixed(RtsFlags.GcFlags.minAllocAreaSize);
1120 // mark the garbage collected CAFs as dead
1121 #if 0 && defined(DEBUG) // doesn't work at the moment
1122 if (major_gc) { gcCAFs(); }
1126 // resetStaticObjectForRetainerProfiling() must be called before
1128 resetStaticObjectForRetainerProfiling();
1131 // zero the scavenged static object list
1133 zero_static_object_list(scavenged_static_objects);
1136 // Reset the nursery
1139 // start any pending finalizers
1141 scheduleFinalizers(last_free_capability, old_weak_ptr_list);
1144 // send exceptions to any threads which were about to die
1145 resurrectThreads(resurrected_threads);
1147 // Update the stable pointer hash table.
1148 updateStablePtrTable(major_gc);
1150 // check sanity after GC
1151 IF_DEBUG(sanity, checkSanity());
1153 // extra GC trace info
1154 IF_DEBUG(gc, statDescribeGens());
1157 // symbol-table based profiling
1158 /* heapCensus(to_blocks); */ /* ToDo */
1161 // restore enclosing cost centre
1167 // check for memory leaks if DEBUG is on
1171 #ifdef RTS_GTK_FRONTPANEL
1172 if (RtsFlags.GcFlags.frontpanel) {
1173 updateFrontPanelAfterGC( N, live );
1177 // ok, GC over: tell the stats department what happened.
1178 stat_endGC(allocated, collected, live, copied, scavd_copied, N);
1180 #if defined(RTS_USER_SIGNALS)
1181 // unblock signals again
1182 unblockUserSignals();
1191 /* -----------------------------------------------------------------------------
1194 traverse_weak_ptr_list is called possibly many times during garbage
1195 collection. It returns a flag indicating whether it did any work
1196 (i.e. called evacuate on any live pointers).
1198 Invariant: traverse_weak_ptr_list is called when the heap is in an
1199 idempotent state. That means that there are no pending
1200 evacuate/scavenge operations. This invariant helps the weak
1201 pointer code decide which weak pointers are dead - if there are no
1202 new live weak pointers, then all the currently unreachable ones are
1205 For generational GC: we just don't try to finalize weak pointers in
1206 older generations than the one we're collecting. This could
1207 probably be optimised by keeping per-generation lists of weak
1208 pointers, but for a few weak pointers this scheme will work.
1210 There are three distinct stages to processing weak pointers:
1212 - weak_stage == WeakPtrs
1214 We process all the weak pointers whos keys are alive (evacuate
1215 their values and finalizers), and repeat until we can find no new
1216 live keys. If no live keys are found in this pass, then we
1217 evacuate the finalizers of all the dead weak pointers in order to
1220 - weak_stage == WeakThreads
1222 Now, we discover which *threads* are still alive. Pointers to
1223 threads from the all_threads and main thread lists are the
1224 weakest of all: a pointers from the finalizer of a dead weak
1225 pointer can keep a thread alive. Any threads found to be unreachable
1226 are evacuated and placed on the resurrected_threads list so we
1227 can send them a signal later.
1229 - weak_stage == WeakDone
1231 No more evacuation is done.
1233 -------------------------------------------------------------------------- */
1236 traverse_weak_ptr_list(void)
1238 StgWeak *w, **last_w, *next_w;
1240 rtsBool flag = rtsFalse;
1242 switch (weak_stage) {
1248 /* doesn't matter where we evacuate values/finalizers to, since
1249 * these pointers are treated as roots (iff the keys are alive).
1253 last_w = &old_weak_ptr_list;
1254 for (w = old_weak_ptr_list; w != NULL; w = next_w) {
1256 /* There might be a DEAD_WEAK on the list if finalizeWeak# was
1257 * called on a live weak pointer object. Just remove it.
1259 if (w->header.info == &stg_DEAD_WEAK_info) {
1260 next_w = ((StgDeadWeak *)w)->link;
1265 switch (get_itbl(w)->type) {
1268 next_w = (StgWeak *)((StgEvacuated *)w)->evacuee;
1273 /* Now, check whether the key is reachable.
1275 new = isAlive(w->key);
1278 // evacuate the value and finalizer
1279 w->value = evacuate(w->value);
1280 w->finalizer = evacuate(w->finalizer);
1281 // remove this weak ptr from the old_weak_ptr list
1283 // and put it on the new weak ptr list
1285 w->link = weak_ptr_list;
1288 IF_DEBUG(weak, debugBelch("Weak pointer still alive at %p -> %p",
1293 last_w = &(w->link);
1299 barf("traverse_weak_ptr_list: not WEAK");
1303 /* If we didn't make any changes, then we can go round and kill all
1304 * the dead weak pointers. The old_weak_ptr list is used as a list
1305 * of pending finalizers later on.
1307 if (flag == rtsFalse) {
1308 for (w = old_weak_ptr_list; w; w = w->link) {
1309 w->finalizer = evacuate(w->finalizer);
1312 // Next, move to the WeakThreads stage after fully
1313 // scavenging the finalizers we've just evacuated.
1314 weak_stage = WeakThreads;
1320 /* Now deal with the all_threads list, which behaves somewhat like
1321 * the weak ptr list. If we discover any threads that are about to
1322 * become garbage, we wake them up and administer an exception.
1325 StgTSO *t, *tmp, *next, **prev;
1327 prev = &old_all_threads;
1328 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1330 tmp = (StgTSO *)isAlive((StgClosure *)t);
1336 ASSERT(get_itbl(t)->type == TSO);
1337 switch (t->what_next) {
1338 case ThreadRelocated:
1343 case ThreadComplete:
1344 // finshed or died. The thread might still be alive, but we
1345 // don't keep it on the all_threads list. Don't forget to
1346 // stub out its global_link field.
1347 next = t->global_link;
1348 t->global_link = END_TSO_QUEUE;
1355 // Threads blocked on black holes: if the black hole
1356 // is alive, then the thread is alive too.
1357 if (tmp == NULL && t->why_blocked == BlockedOnBlackHole) {
1358 if (isAlive(t->block_info.closure)) {
1359 t = (StgTSO *)evacuate((StgClosure *)t);
1366 // not alive (yet): leave this thread on the
1367 // old_all_threads list.
1368 prev = &(t->global_link);
1369 next = t->global_link;
1372 // alive: move this thread onto the all_threads list.
1373 next = t->global_link;
1374 t->global_link = all_threads;
1381 /* If we evacuated any threads, we need to go back to the scavenger.
1383 if (flag) return rtsTrue;
1385 /* And resurrect any threads which were about to become garbage.
1388 StgTSO *t, *tmp, *next;
1389 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1390 next = t->global_link;
1391 tmp = (StgTSO *)evacuate((StgClosure *)t);
1392 tmp->global_link = resurrected_threads;
1393 resurrected_threads = tmp;
1397 /* Finally, we can update the blackhole_queue. This queue
1398 * simply strings together TSOs blocked on black holes, it is
1399 * not intended to keep anything alive. Hence, we do not follow
1400 * pointers on the blackhole_queue until now, when we have
1401 * determined which TSOs are otherwise reachable. We know at
1402 * this point that all TSOs have been evacuated, however.
1406 for (pt = &blackhole_queue; *pt != END_TSO_QUEUE; pt = &((*pt)->link)) {
1407 *pt = (StgTSO *)isAlive((StgClosure *)*pt);
1408 ASSERT(*pt != NULL);
1412 weak_stage = WeakDone; // *now* we're done,
1413 return rtsTrue; // but one more round of scavenging, please
1416 barf("traverse_weak_ptr_list");
1422 /* -----------------------------------------------------------------------------
1423 After GC, the live weak pointer list may have forwarding pointers
1424 on it, because a weak pointer object was evacuated after being
1425 moved to the live weak pointer list. We remove those forwarding
1428 Also, we don't consider weak pointer objects to be reachable, but
1429 we must nevertheless consider them to be "live" and retain them.
1430 Therefore any weak pointer objects which haven't as yet been
1431 evacuated need to be evacuated now.
1432 -------------------------------------------------------------------------- */
1436 mark_weak_ptr_list ( StgWeak **list )
1438 StgWeak *w, **last_w;
1441 for (w = *list; w; w = w->link) {
1442 // w might be WEAK, EVACUATED, or DEAD_WEAK (actually CON_STATIC) here
1443 ASSERT(w->header.info == &stg_DEAD_WEAK_info
1444 || get_itbl(w)->type == WEAK || get_itbl(w)->type == EVACUATED);
1445 w = (StgWeak *)evacuate((StgClosure *)w);
1447 last_w = &(w->link);
1451 /* -----------------------------------------------------------------------------
1452 isAlive determines whether the given closure is still alive (after
1453 a garbage collection) or not. It returns the new address of the
1454 closure if it is alive, or NULL otherwise.
1456 NOTE: Use it before compaction only!
1457 -------------------------------------------------------------------------- */
1461 isAlive(StgClosure *p)
1463 const StgInfoTable *info;
1468 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
1471 // ignore static closures
1473 // ToDo: for static closures, check the static link field.
1474 // Problem here is that we sometimes don't set the link field, eg.
1475 // for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
1477 if (!HEAP_ALLOCED(p)) {
1481 // ignore closures in generations that we're not collecting.
1483 if (bd->gen_no > N) {
1487 // if it's a pointer into to-space, then we're done
1488 if (bd->flags & BF_EVACUATED) {
1492 // large objects use the evacuated flag
1493 if (bd->flags & BF_LARGE) {
1497 // check the mark bit for compacted steps
1498 if ((bd->flags & BF_COMPACTED) && is_marked((P_)p,bd)) {
1502 switch (info->type) {
1507 case IND_OLDGEN: // rely on compatible layout with StgInd
1508 case IND_OLDGEN_PERM:
1509 // follow indirections
1510 p = ((StgInd *)p)->indirectee;
1515 return ((StgEvacuated *)p)->evacuee;
1518 if (((StgTSO *)p)->what_next == ThreadRelocated) {
1519 p = (StgClosure *)((StgTSO *)p)->link;
1532 mark_root(StgClosure **root)
1534 *root = evacuate(*root);
1538 upd_evacuee(StgClosure *p, StgClosure *dest)
1540 // not true: (ToDo: perhaps it should be)
1541 // ASSERT(Bdescr((P_)dest)->flags & BF_EVACUATED);
1542 SET_INFO(p, &stg_EVACUATED_info);
1543 ((StgEvacuated *)p)->evacuee = dest;
1547 STATIC_INLINE StgClosure *
1548 copy(StgClosure *src, nat size, step *stp)
1554 nat size_org = size;
1557 TICK_GC_WORDS_COPIED(size);
1558 /* Find out where we're going, using the handy "to" pointer in
1559 * the step of the source object. If it turns out we need to
1560 * evacuate to an older generation, adjust it here (see comment
1563 if (stp->gen_no < evac_gen) {
1564 #ifdef NO_EAGER_PROMOTION
1565 failed_to_evac = rtsTrue;
1567 stp = &generations[evac_gen].steps[0];
1571 /* chain a new block onto the to-space for the destination step if
1574 if (stp->hp + size >= stp->hpLim) {
1575 gc_alloc_block(stp);
1580 stp->hp = to + size;
1581 for (i = 0; i < size; i++) { // unroll for small i
1584 upd_evacuee((StgClosure *)from,(StgClosure *)to);
1587 // We store the size of the just evacuated object in the LDV word so that
1588 // the profiler can guess the position of the next object later.
1589 SET_EVACUAEE_FOR_LDV(from, size_org);
1591 return (StgClosure *)to;
1594 // Same as copy() above, except the object will be allocated in memory
1595 // that will not be scavenged. Used for object that have no pointer
1597 STATIC_INLINE StgClosure *
1598 copy_noscav(StgClosure *src, nat size, step *stp)
1604 nat size_org = size;
1607 TICK_GC_WORDS_COPIED(size);
1608 /* Find out where we're going, using the handy "to" pointer in
1609 * the step of the source object. If it turns out we need to
1610 * evacuate to an older generation, adjust it here (see comment
1613 if (stp->gen_no < evac_gen) {
1614 #ifdef NO_EAGER_PROMOTION
1615 failed_to_evac = rtsTrue;
1617 stp = &generations[evac_gen].steps[0];
1621 /* chain a new block onto the to-space for the destination step if
1624 if (stp->scavd_hp + size >= stp->scavd_hpLim) {
1625 gc_alloc_scavd_block(stp);
1630 stp->scavd_hp = to + size;
1631 for (i = 0; i < size; i++) { // unroll for small i
1634 upd_evacuee((StgClosure *)from,(StgClosure *)to);
1637 // We store the size of the just evacuated object in the LDV word so that
1638 // the profiler can guess the position of the next object later.
1639 SET_EVACUAEE_FOR_LDV(from, size_org);
1641 return (StgClosure *)to;
1644 /* Special version of copy() for when we only want to copy the info
1645 * pointer of an object, but reserve some padding after it. This is
1646 * used to optimise evacuation of BLACKHOLEs.
1651 copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *stp)
1656 nat size_to_copy_org = size_to_copy;
1659 TICK_GC_WORDS_COPIED(size_to_copy);
1660 if (stp->gen_no < evac_gen) {
1661 #ifdef NO_EAGER_PROMOTION
1662 failed_to_evac = rtsTrue;
1664 stp = &generations[evac_gen].steps[0];
1668 if (stp->hp + size_to_reserve >= stp->hpLim) {
1669 gc_alloc_block(stp);
1672 for(to = stp->hp, from = (P_)src; size_to_copy>0; --size_to_copy) {
1677 stp->hp += size_to_reserve;
1678 upd_evacuee(src,(StgClosure *)dest);
1680 // We store the size of the just evacuated object in the LDV word so that
1681 // the profiler can guess the position of the next object later.
1682 // size_to_copy_org is wrong because the closure already occupies size_to_reserve
1684 SET_EVACUAEE_FOR_LDV(src, size_to_reserve);
1686 if (size_to_reserve - size_to_copy_org > 0)
1687 FILL_SLOP(stp->hp - 1, (int)(size_to_reserve - size_to_copy_org));
1689 return (StgClosure *)dest;
1693 /* -----------------------------------------------------------------------------
1694 Evacuate a large object
1696 This just consists of removing the object from the (doubly-linked)
1697 step->large_objects list, and linking it on to the (singly-linked)
1698 step->new_large_objects list, from where it will be scavenged later.
1700 Convention: bd->flags has BF_EVACUATED set for a large object
1701 that has been evacuated, or unset otherwise.
1702 -------------------------------------------------------------------------- */
1706 evacuate_large(StgPtr p)
1708 bdescr *bd = Bdescr(p);
1711 // object must be at the beginning of the block (or be a ByteArray)
1712 ASSERT(get_itbl((StgClosure *)p)->type == ARR_WORDS ||
1713 (((W_)p & BLOCK_MASK) == 0));
1715 // already evacuated?
1716 if (bd->flags & BF_EVACUATED) {
1717 /* Don't forget to set the failed_to_evac flag if we didn't get
1718 * the desired destination (see comments in evacuate()).
1720 if (bd->gen_no < evac_gen) {
1721 failed_to_evac = rtsTrue;
1722 TICK_GC_FAILED_PROMOTION();
1728 // remove from large_object list
1730 bd->u.back->link = bd->link;
1731 } else { // first object in the list
1732 stp->large_objects = bd->link;
1735 bd->link->u.back = bd->u.back;
1738 /* link it on to the evacuated large object list of the destination step
1741 if (stp->gen_no < evac_gen) {
1742 #ifdef NO_EAGER_PROMOTION
1743 failed_to_evac = rtsTrue;
1745 stp = &generations[evac_gen].steps[0];
1750 bd->gen_no = stp->gen_no;
1751 bd->link = stp->new_large_objects;
1752 stp->new_large_objects = bd;
1753 bd->flags |= BF_EVACUATED;
1756 /* -----------------------------------------------------------------------------
1759 This is called (eventually) for every live object in the system.
1761 The caller to evacuate specifies a desired generation in the
1762 evac_gen global variable. The following conditions apply to
1763 evacuating an object which resides in generation M when we're
1764 collecting up to generation N
1768 else evac to step->to
1770 if M < evac_gen evac to evac_gen, step 0
1772 if the object is already evacuated, then we check which generation
1775 if M >= evac_gen do nothing
1776 if M < evac_gen set failed_to_evac flag to indicate that we
1777 didn't manage to evacuate this object into evac_gen.
1782 evacuate() is the single most important function performance-wise
1783 in the GC. Various things have been tried to speed it up, but as
1784 far as I can tell the code generated by gcc 3.2 with -O2 is about
1785 as good as it's going to get. We pass the argument to evacuate()
1786 in a register using the 'regparm' attribute (see the prototype for
1787 evacuate() near the top of this file).
1789 Changing evacuate() to take an (StgClosure **) rather than
1790 returning the new pointer seems attractive, because we can avoid
1791 writing back the pointer when it hasn't changed (eg. for a static
1792 object, or an object in a generation > N). However, I tried it and
1793 it doesn't help. One reason is that the (StgClosure **) pointer
1794 gets spilled to the stack inside evacuate(), resulting in far more
1795 extra reads/writes than we save.
1796 -------------------------------------------------------------------------- */
1798 REGPARM1 static StgClosure *
1799 evacuate(StgClosure *q)
1806 const StgInfoTable *info;
1809 ASSERT(LOOKS_LIKE_CLOSURE_PTR(q));
1811 if (!HEAP_ALLOCED(q)) {
1813 if (!major_gc) return q;
1816 switch (info->type) {
1819 if (info->srt_bitmap != 0 &&
1820 *THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
1821 *THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
1822 static_objects = (StgClosure *)q;
1827 if (info->srt_bitmap != 0 &&
1828 *FUN_STATIC_LINK((StgClosure *)q) == NULL) {
1829 *FUN_STATIC_LINK((StgClosure *)q) = static_objects;
1830 static_objects = (StgClosure *)q;
1835 /* If q->saved_info != NULL, then it's a revertible CAF - it'll be
1836 * on the CAF list, so don't do anything with it here (we'll
1837 * scavenge it later).
1839 if (((StgIndStatic *)q)->saved_info == NULL
1840 && *IND_STATIC_LINK((StgClosure *)q) == NULL) {
1841 *IND_STATIC_LINK((StgClosure *)q) = static_objects;
1842 static_objects = (StgClosure *)q;
1847 if (*STATIC_LINK(info,(StgClosure *)q) == NULL) {
1848 *STATIC_LINK(info,(StgClosure *)q) = static_objects;
1849 static_objects = (StgClosure *)q;
1853 case CONSTR_INTLIKE:
1854 case CONSTR_CHARLIKE:
1855 case CONSTR_NOCAF_STATIC:
1856 /* no need to put these on the static linked list, they don't need
1862 barf("evacuate(static): strange closure type %d", (int)(info->type));
1868 if (bd->gen_no > N) {
1869 /* Can't evacuate this object, because it's in a generation
1870 * older than the ones we're collecting. Let's hope that it's
1871 * in evac_gen or older, or we will have to arrange to track
1872 * this pointer using the mutable list.
1874 if (bd->gen_no < evac_gen) {
1876 failed_to_evac = rtsTrue;
1877 TICK_GC_FAILED_PROMOTION();
1882 if ((bd->flags & (BF_LARGE | BF_COMPACTED | BF_EVACUATED)) != 0) {
1884 /* pointer into to-space: just return it. This normally
1885 * shouldn't happen, but alllowing it makes certain things
1886 * slightly easier (eg. the mutable list can contain the same
1887 * object twice, for example).
1889 if (bd->flags & BF_EVACUATED) {
1890 if (bd->gen_no < evac_gen) {
1891 failed_to_evac = rtsTrue;
1892 TICK_GC_FAILED_PROMOTION();
1897 /* evacuate large objects by re-linking them onto a different list.
1899 if (bd->flags & BF_LARGE) {
1901 if (info->type == TSO &&
1902 ((StgTSO *)q)->what_next == ThreadRelocated) {
1903 q = (StgClosure *)((StgTSO *)q)->link;
1906 evacuate_large((P_)q);
1910 /* If the object is in a step that we're compacting, then we
1911 * need to use an alternative evacuate procedure.
1913 if (bd->flags & BF_COMPACTED) {
1914 if (!is_marked((P_)q,bd)) {
1916 if (mark_stack_full()) {
1917 mark_stack_overflowed = rtsTrue;
1920 push_mark_stack((P_)q);
1930 switch (info->type) {
1934 return copy(q,sizeW_fromITBL(info),stp);
1938 StgWord w = (StgWord)q->payload[0];
1939 if (q->header.info == Czh_con_info &&
1940 // unsigned, so always true: (StgChar)w >= MIN_CHARLIKE &&
1941 (StgChar)w <= MAX_CHARLIKE) {
1942 return (StgClosure *)CHARLIKE_CLOSURE((StgChar)w);
1944 if (q->header.info == Izh_con_info &&
1945 (StgInt)w >= MIN_INTLIKE && (StgInt)w <= MAX_INTLIKE) {
1946 return (StgClosure *)INTLIKE_CLOSURE((StgInt)w);
1949 return copy_noscav(q,sizeofW(StgHeader)+1,stp);
1955 return copy(q,sizeofW(StgHeader)+1,stp);
1959 return copy(q,sizeofW(StgThunk)+1,stp);
1964 #ifdef NO_PROMOTE_THUNKS
1965 if (bd->gen_no == 0 &&
1966 bd->step->no != 0 &&
1967 bd->step->no == generations[bd->gen_no].n_steps-1) {
1971 return copy(q,sizeofW(StgThunk)+2,stp);
1978 return copy(q,sizeofW(StgHeader)+2,stp);
1981 return copy_noscav(q,sizeofW(StgHeader)+2,stp);
1984 return copy(q,thunk_sizeW_fromITBL(info),stp);
1989 case IND_OLDGEN_PERM:
1992 return copy(q,sizeW_fromITBL(info),stp);
1995 return copy(q,bco_sizeW((StgBCO *)q),stp);
1998 case SE_CAF_BLACKHOLE:
2001 return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
2003 case THUNK_SELECTOR:
2007 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
2008 return copy(q,THUNK_SELECTOR_sizeW(),stp);
2011 p = eval_thunk_selector(info->layout.selector_offset,
2015 return copy(q,THUNK_SELECTOR_sizeW(),stp);
2018 // q is still BLACKHOLE'd.
2019 thunk_selector_depth++;
2021 thunk_selector_depth--;
2023 // Update the THUNK_SELECTOR with an indirection to the
2024 // EVACUATED closure now at p. Why do this rather than
2025 // upd_evacuee(q,p)? Because we have an invariant that an
2026 // EVACUATED closure always points to an object in the
2027 // same or an older generation (required by the short-cut
2028 // test in the EVACUATED case, below).
2029 SET_INFO(q, &stg_IND_info);
2030 ((StgInd *)q)->indirectee = p;
2033 // We store the size of the just evacuated object in the
2034 // LDV word so that the profiler can guess the position of
2035 // the next object later.
2036 SET_EVACUAEE_FOR_LDV(q, THUNK_SELECTOR_sizeW());
2044 // follow chains of indirections, don't evacuate them
2045 q = ((StgInd*)q)->indirectee;
2057 case CATCH_STM_FRAME:
2058 case CATCH_RETRY_FRAME:
2059 case ATOMICALLY_FRAME:
2060 // shouldn't see these
2061 barf("evacuate: stack frame at %p\n", q);
2064 return copy(q,pap_sizeW((StgPAP*)q),stp);
2067 return copy(q,ap_sizeW((StgAP*)q),stp);
2070 return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp);
2073 /* Already evacuated, just return the forwarding address.
2074 * HOWEVER: if the requested destination generation (evac_gen) is
2075 * older than the actual generation (because the object was
2076 * already evacuated to a younger generation) then we have to
2077 * set the failed_to_evac flag to indicate that we couldn't
2078 * manage to promote the object to the desired generation.
2081 * Optimisation: the check is fairly expensive, but we can often
2082 * shortcut it if either the required generation is 0, or the
2083 * current object (the EVACUATED) is in a high enough generation.
2084 * We know that an EVACUATED always points to an object in the
2085 * same or an older generation. stp is the lowest step that the
2086 * current object would be evacuated to, so we only do the full
2087 * check if stp is too low.
2089 if (evac_gen > 0 && stp->gen_no < evac_gen) { // optimisation
2090 StgClosure *p = ((StgEvacuated*)q)->evacuee;
2091 if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < evac_gen) {
2092 failed_to_evac = rtsTrue;
2093 TICK_GC_FAILED_PROMOTION();
2096 return ((StgEvacuated*)q)->evacuee;
2099 // just copy the block
2100 return copy_noscav(q,arr_words_sizeW((StgArrWords *)q),stp);
2103 case MUT_ARR_PTRS_FROZEN:
2104 case MUT_ARR_PTRS_FROZEN0:
2105 // just copy the block
2106 return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
2110 StgTSO *tso = (StgTSO *)q;
2112 /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
2114 if (tso->what_next == ThreadRelocated) {
2115 q = (StgClosure *)tso->link;
2119 /* To evacuate a small TSO, we need to relocate the update frame
2126 new_tso = (StgTSO *)copyPart((StgClosure *)tso,
2128 sizeofW(StgTSO), stp);
2129 move_TSO(tso, new_tso);
2130 for (p = tso->sp, q = new_tso->sp;
2131 p < tso->stack+tso->stack_size;) {
2135 return (StgClosure *)new_tso;
2142 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
2143 to = copy(q,BLACKHOLE_sizeW(),stp);
2144 //ToDo: derive size etc from reverted IP
2145 //to = copy(q,size,stp);
2147 debugBelch("@@ evacuate: RBH %p (%s) to %p (%s)",
2148 q, info_type(q), to, info_type(to)));
2153 ASSERT(sizeofW(StgBlockedFetch) >= MIN_NONUPD_SIZE);
2154 to = copy(q,sizeofW(StgBlockedFetch),stp);
2156 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
2157 q, info_type(q), to, info_type(to)));
2164 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
2165 to = copy(q,sizeofW(StgFetchMe),stp);
2167 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
2168 q, info_type(q), to, info_type(to)));
2172 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
2173 to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
2175 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
2176 q, info_type(q), to, info_type(to)));
2181 return copy(q,sizeofW(StgTRecHeader),stp);
2183 case TVAR_WAIT_QUEUE:
2184 return copy(q,sizeofW(StgTVarWaitQueue),stp);
2187 return copy(q,sizeofW(StgTVar),stp);
2190 return copy(q,sizeofW(StgTRecChunk),stp);
2193 barf("evacuate: strange closure type %d", (int)(info->type));
2199 /* -----------------------------------------------------------------------------
2200 Evaluate a THUNK_SELECTOR if possible.
2202 returns: NULL if we couldn't evaluate this THUNK_SELECTOR, or
2203 a closure pointer if we evaluated it and this is the result. Note
2204 that "evaluating" the THUNK_SELECTOR doesn't necessarily mean
2205 reducing it to HNF, just that we have eliminated the selection.
2206 The result might be another thunk, or even another THUNK_SELECTOR.
2208 If the return value is non-NULL, the original selector thunk has
2209 been BLACKHOLE'd, and should be updated with an indirection or a
2210 forwarding pointer. If the return value is NULL, then the selector
2214 ToDo: the treatment of THUNK_SELECTORS could be improved in the
2215 following way (from a suggestion by Ian Lynagh):
2217 We can have a chain like this:
2221 |-----> sel_0 --> (a,b)
2223 |-----> sel_0 --> ...
2225 and the depth limit means we don't go all the way to the end of the
2226 chain, which results in a space leak. This affects the recursive
2227 call to evacuate() in the THUNK_SELECTOR case in evacuate(): *not*
2228 the recursive call to eval_thunk_selector() in
2229 eval_thunk_selector().
2231 We could eliminate the depth bound in this case, in the following
2234 - traverse the chain once to discover the *value* of the
2235 THUNK_SELECTOR. Mark all THUNK_SELECTORS that we
2236 visit on the way as having been visited already (somehow).
2238 - in a second pass, traverse the chain again updating all
2239 THUNK_SEELCTORS that we find on the way with indirections to
2242 - if we encounter a "marked" THUNK_SELECTOR in a normal
2243 evacuate(), we konw it can't be updated so just evac it.
2245 Program that illustrates the problem:
2248 foo (x:xs) = let (ys, zs) = foo xs
2249 in if x >= 0 then (x:ys, zs) else (ys, x:zs)
2251 main = bar [1..(100000000::Int)]
2252 bar xs = (\(ys, zs) -> print ys >> print zs) (foo xs)
2254 -------------------------------------------------------------------------- */
2256 static inline rtsBool
2257 is_to_space ( StgClosure *p )
2261 bd = Bdescr((StgPtr)p);
2262 if (HEAP_ALLOCED(p) &&
2263 ((bd->flags & BF_EVACUATED)
2264 || ((bd->flags & BF_COMPACTED) &&
2265 is_marked((P_)p,bd)))) {
2273 eval_thunk_selector( nat field, StgSelector * p )
2276 const StgInfoTable *info_ptr;
2277 StgClosure *selectee;
2279 selectee = p->selectee;
2281 // Save the real info pointer (NOTE: not the same as get_itbl()).
2282 info_ptr = p->header.info;
2284 // If the THUNK_SELECTOR is in a generation that we are not
2285 // collecting, then bail out early. We won't be able to save any
2286 // space in any case, and updating with an indirection is trickier
2288 if (Bdescr((StgPtr)p)->gen_no > N) {
2292 // BLACKHOLE the selector thunk, since it is now under evaluation.
2293 // This is important to stop us going into an infinite loop if
2294 // this selector thunk eventually refers to itself.
2295 SET_INFO(p,&stg_BLACKHOLE_info);
2299 // We don't want to end up in to-space, because this causes
2300 // problems when the GC later tries to evacuate the result of
2301 // eval_thunk_selector(). There are various ways this could
2304 // 1. following an IND_STATIC
2306 // 2. when the old generation is compacted, the mark phase updates
2307 // from-space pointers to be to-space pointers, and we can't
2308 // reliably tell which we're following (eg. from an IND_STATIC).
2310 // 3. compacting GC again: if we're looking at a constructor in
2311 // the compacted generation, it might point directly to objects
2312 // in to-space. We must bale out here, otherwise doing the selection
2313 // will result in a to-space pointer being returned.
2315 // (1) is dealt with using a BF_EVACUATED test on the
2316 // selectee. (2) and (3): we can tell if we're looking at an
2317 // object in the compacted generation that might point to
2318 // to-space objects by testing that (a) it is BF_COMPACTED, (b)
2319 // the compacted generation is being collected, and (c) the
2320 // object is marked. Only a marked object may have pointers that
2321 // point to to-space objects, because that happens when
2324 // The to-space test is now embodied in the in_to_space() inline
2325 // function, as it is re-used below.
2327 if (is_to_space(selectee)) {
2331 info = get_itbl(selectee);
2332 switch (info->type) {
2340 case CONSTR_NOCAF_STATIC:
2341 // check that the size is in range
2342 ASSERT(field < (StgWord32)(info->layout.payload.ptrs +
2343 info->layout.payload.nptrs));
2345 // Select the right field from the constructor, and check
2346 // that the result isn't in to-space. It might be in
2347 // to-space if, for example, this constructor contains
2348 // pointers to younger-gen objects (and is on the mut-once
2353 q = selectee->payload[field];
2354 if (is_to_space(q)) {
2364 case IND_OLDGEN_PERM:
2366 selectee = ((StgInd *)selectee)->indirectee;
2370 // We don't follow pointers into to-space; the constructor
2371 // has already been evacuated, so we won't save any space
2372 // leaks by evaluating this selector thunk anyhow.
2375 case THUNK_SELECTOR:
2379 // check that we don't recurse too much, re-using the
2380 // depth bound also used in evacuate().
2381 if (thunk_selector_depth >= MAX_THUNK_SELECTOR_DEPTH) {
2384 thunk_selector_depth++;
2386 val = eval_thunk_selector(info->layout.selector_offset,
2387 (StgSelector *)selectee);
2389 thunk_selector_depth--;
2394 // We evaluated this selector thunk, so update it with
2395 // an indirection. NOTE: we don't use UPD_IND here,
2396 // because we are guaranteed that p is in a generation
2397 // that we are collecting, and we never want to put the
2398 // indirection on a mutable list.
2400 // For the purposes of LDV profiling, we have destroyed
2401 // the original selector thunk.
2402 SET_INFO(p, info_ptr);
2403 LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(selectee);
2405 ((StgInd *)selectee)->indirectee = val;
2406 SET_INFO(selectee,&stg_IND_info);
2408 // For the purposes of LDV profiling, we have created an
2410 LDV_RECORD_CREATE(selectee);
2427 case SE_CAF_BLACKHOLE:
2439 // not evaluated yet
2443 barf("eval_thunk_selector: strange selectee %d",
2448 // We didn't manage to evaluate this thunk; restore the old info pointer
2449 SET_INFO(p, info_ptr);
2453 /* -----------------------------------------------------------------------------
2454 move_TSO is called to update the TSO structure after it has been
2455 moved from one place to another.
2456 -------------------------------------------------------------------------- */
2459 move_TSO (StgTSO *src, StgTSO *dest)
2463 // relocate the stack pointer...
2464 diff = (StgPtr)dest - (StgPtr)src; // In *words*
2465 dest->sp = (StgPtr)dest->sp + diff;
2468 /* Similar to scavenge_large_bitmap(), but we don't write back the
2469 * pointers we get back from evacuate().
2472 scavenge_large_srt_bitmap( StgLargeSRT *large_srt )
2479 bitmap = large_srt->l.bitmap[b];
2480 size = (nat)large_srt->l.size;
2481 p = (StgClosure **)large_srt->srt;
2482 for (i = 0; i < size; ) {
2483 if ((bitmap & 1) != 0) {
2488 if (i % BITS_IN(W_) == 0) {
2490 bitmap = large_srt->l.bitmap[b];
2492 bitmap = bitmap >> 1;
2497 /* evacuate the SRT. If srt_bitmap is zero, then there isn't an
2498 * srt field in the info table. That's ok, because we'll
2499 * never dereference it.
2502 scavenge_srt (StgClosure **srt, nat srt_bitmap)
2507 bitmap = srt_bitmap;
2510 if (bitmap == (StgHalfWord)(-1)) {
2511 scavenge_large_srt_bitmap( (StgLargeSRT *)srt );
2515 while (bitmap != 0) {
2516 if ((bitmap & 1) != 0) {
2517 #ifdef ENABLE_WIN32_DLL_SUPPORT
2518 // Special-case to handle references to closures hiding out in DLLs, since
2519 // double indirections required to get at those. The code generator knows
2520 // which is which when generating the SRT, so it stores the (indirect)
2521 // reference to the DLL closure in the table by first adding one to it.
2522 // We check for this here, and undo the addition before evacuating it.
2524 // If the SRT entry hasn't got bit 0 set, the SRT entry points to a
2525 // closure that's fixed at link-time, and no extra magic is required.
2526 if ( (unsigned long)(*srt) & 0x1 ) {
2527 evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
2536 bitmap = bitmap >> 1;
2542 scavenge_thunk_srt(const StgInfoTable *info)
2544 StgThunkInfoTable *thunk_info;
2546 if (!major_gc) return;
2548 thunk_info = itbl_to_thunk_itbl(info);
2549 scavenge_srt((StgClosure **)GET_SRT(thunk_info), thunk_info->i.srt_bitmap);
2553 scavenge_fun_srt(const StgInfoTable *info)
2555 StgFunInfoTable *fun_info;
2557 if (!major_gc) return;
2559 fun_info = itbl_to_fun_itbl(info);
2560 scavenge_srt((StgClosure **)GET_FUN_SRT(fun_info), fun_info->i.srt_bitmap);
2563 /* -----------------------------------------------------------------------------
2565 -------------------------------------------------------------------------- */
2568 scavengeTSO (StgTSO *tso)
2570 if ( tso->why_blocked == BlockedOnMVar
2571 || tso->why_blocked == BlockedOnBlackHole
2572 || tso->why_blocked == BlockedOnException
2574 || tso->why_blocked == BlockedOnGA
2575 || tso->why_blocked == BlockedOnGA_NoSend
2578 tso->block_info.closure = evacuate(tso->block_info.closure);
2580 if ( tso->blocked_exceptions != NULL ) {
2581 tso->blocked_exceptions =
2582 (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
2585 // We don't always chase the link field: TSOs on the blackhole
2586 // queue are not automatically alive, so the link field is a
2587 // "weak" pointer in that case.
2588 if (tso->why_blocked != BlockedOnBlackHole) {
2589 tso->link = (StgTSO *)evacuate((StgClosure *)tso->link);
2592 // scavange current transaction record
2593 tso->trec = (StgTRecHeader *)evacuate((StgClosure *)tso->trec);
2595 // scavenge this thread's stack
2596 scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
2599 /* -----------------------------------------------------------------------------
2600 Blocks of function args occur on the stack (at the top) and
2602 -------------------------------------------------------------------------- */
2604 STATIC_INLINE StgPtr
2605 scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
2612 switch (fun_info->f.fun_type) {
2614 bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
2615 size = BITMAP_SIZE(fun_info->f.b.bitmap);
2618 size = GET_FUN_LARGE_BITMAP(fun_info)->size;
2619 scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
2623 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2624 size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->f.fun_type]);
2627 if ((bitmap & 1) == 0) {
2628 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2631 bitmap = bitmap >> 1;
2639 STATIC_INLINE StgPtr
2640 scavenge_PAP_payload (StgClosure *fun, StgClosure **payload, StgWord size)
2644 StgFunInfoTable *fun_info;
2646 fun_info = get_fun_itbl(fun);
2647 ASSERT(fun_info->i.type != PAP);
2648 p = (StgPtr)payload;
2650 switch (fun_info->f.fun_type) {
2652 bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
2655 scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
2659 scavenge_large_bitmap((StgPtr)payload, BCO_BITMAP(fun), size);
2663 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2666 if ((bitmap & 1) == 0) {
2667 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2670 bitmap = bitmap >> 1;
2678 STATIC_INLINE StgPtr
2679 scavenge_PAP (StgPAP *pap)
2681 pap->fun = evacuate(pap->fun);
2682 return scavenge_PAP_payload (pap->fun, pap->payload, pap->n_args);
2685 STATIC_INLINE StgPtr
2686 scavenge_AP (StgAP *ap)
2688 ap->fun = evacuate(ap->fun);
2689 return scavenge_PAP_payload (ap->fun, ap->payload, ap->n_args);
2692 /* -----------------------------------------------------------------------------
2693 Scavenge a given step until there are no more objects in this step
2696 evac_gen is set by the caller to be either zero (for a step in a
2697 generation < N) or G where G is the generation of the step being
2700 We sometimes temporarily change evac_gen back to zero if we're
2701 scavenging a mutable object where early promotion isn't such a good
2703 -------------------------------------------------------------------------- */
2711 nat saved_evac_gen = evac_gen;
2716 failed_to_evac = rtsFalse;
2718 /* scavenge phase - standard breadth-first scavenging of the
2722 while (bd != stp->hp_bd || p < stp->hp) {
2724 // If we're at the end of this block, move on to the next block
2725 if (bd != stp->hp_bd && p == bd->free) {
2731 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2732 info = get_itbl((StgClosure *)p);
2734 ASSERT(thunk_selector_depth == 0);
2737 switch (info->type) {
2741 StgMVar *mvar = ((StgMVar *)p);
2743 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
2744 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
2745 mvar->value = evacuate((StgClosure *)mvar->value);
2746 evac_gen = saved_evac_gen;
2747 failed_to_evac = rtsTrue; // mutable.
2748 p += sizeofW(StgMVar);
2753 scavenge_fun_srt(info);
2754 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2755 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2756 p += sizeofW(StgHeader) + 2;
2760 scavenge_thunk_srt(info);
2761 ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
2762 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2763 p += sizeofW(StgThunk) + 2;
2767 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2768 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2769 p += sizeofW(StgHeader) + 2;
2773 scavenge_thunk_srt(info);
2774 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2775 p += sizeofW(StgThunk) + 1;
2779 scavenge_fun_srt(info);
2781 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2782 p += sizeofW(StgHeader) + 1;
2786 scavenge_thunk_srt(info);
2787 p += sizeofW(StgThunk) + 1;
2791 scavenge_fun_srt(info);
2793 p += sizeofW(StgHeader) + 1;
2797 scavenge_thunk_srt(info);
2798 p += sizeofW(StgThunk) + 2;
2802 scavenge_fun_srt(info);
2804 p += sizeofW(StgHeader) + 2;
2808 scavenge_thunk_srt(info);
2809 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2810 p += sizeofW(StgThunk) + 2;
2814 scavenge_fun_srt(info);
2816 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2817 p += sizeofW(StgHeader) + 2;
2821 scavenge_fun_srt(info);
2828 scavenge_thunk_srt(info);
2829 end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
2830 for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
2831 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2833 p += info->layout.payload.nptrs;
2844 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2845 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2846 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2848 p += info->layout.payload.nptrs;
2853 StgBCO *bco = (StgBCO *)p;
2854 bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
2855 bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
2856 bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
2857 bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
2858 p += bco_sizeW(bco);
2863 if (stp->gen->no != 0) {
2866 // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an
2867 // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
2868 LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
2871 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
2873 SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
2875 // We pretend that p has just been created.
2876 LDV_RECORD_CREATE((StgClosure *)p);
2879 case IND_OLDGEN_PERM:
2880 ((StgInd *)p)->indirectee = evacuate(((StgInd *)p)->indirectee);
2881 p += sizeofW(StgInd);
2886 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2887 evac_gen = saved_evac_gen;
2888 failed_to_evac = rtsTrue; // mutable anyhow
2889 p += sizeofW(StgMutVar);
2893 case SE_CAF_BLACKHOLE:
2896 p += BLACKHOLE_sizeW();
2899 case THUNK_SELECTOR:
2901 StgSelector *s = (StgSelector *)p;
2902 s->selectee = evacuate(s->selectee);
2903 p += THUNK_SELECTOR_sizeW();
2907 // A chunk of stack saved in a heap object
2910 StgAP_STACK *ap = (StgAP_STACK *)p;
2912 ap->fun = evacuate(ap->fun);
2913 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2914 p = (StgPtr)ap->payload + ap->size;
2919 p = scavenge_PAP((StgPAP *)p);
2923 p = scavenge_AP((StgAP *)p);
2927 // nothing to follow
2928 p += arr_words_sizeW((StgArrWords *)p);
2932 // follow everything
2936 evac_gen = 0; // repeatedly mutable
2937 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2938 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2939 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2941 evac_gen = saved_evac_gen;
2942 failed_to_evac = rtsTrue; // mutable anyhow.
2946 case MUT_ARR_PTRS_FROZEN:
2947 case MUT_ARR_PTRS_FROZEN0:
2948 // follow everything
2952 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2953 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2954 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2956 // it's tempting to recordMutable() if failed_to_evac is
2957 // false, but that breaks some assumptions (eg. every
2958 // closure on the mutable list is supposed to have the MUT
2959 // flag set, and MUT_ARR_PTRS_FROZEN doesn't).
2965 StgTSO *tso = (StgTSO *)p;
2968 evac_gen = saved_evac_gen;
2969 failed_to_evac = rtsTrue; // mutable anyhow.
2970 p += tso_sizeW(tso);
2978 nat size, ptrs, nonptrs, vhs;
2980 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2982 StgRBH *rbh = (StgRBH *)p;
2983 (StgClosure *)rbh->blocking_queue =
2984 evacuate((StgClosure *)rbh->blocking_queue);
2985 failed_to_evac = rtsTrue; // mutable anyhow.
2987 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2988 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2989 // ToDo: use size of reverted closure here!
2990 p += BLACKHOLE_sizeW();
2996 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2997 // follow the pointer to the node which is being demanded
2998 (StgClosure *)bf->node =
2999 evacuate((StgClosure *)bf->node);
3000 // follow the link to the rest of the blocking queue
3001 (StgClosure *)bf->link =
3002 evacuate((StgClosure *)bf->link);
3004 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3005 bf, info_type((StgClosure *)bf),
3006 bf->node, info_type(bf->node)));
3007 p += sizeofW(StgBlockedFetch);
3015 p += sizeofW(StgFetchMe);
3016 break; // nothing to do in this case
3020 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3021 (StgClosure *)fmbq->blocking_queue =
3022 evacuate((StgClosure *)fmbq->blocking_queue);
3024 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3025 p, info_type((StgClosure *)p)));
3026 p += sizeofW(StgFetchMeBlockingQueue);
3031 case TVAR_WAIT_QUEUE:
3033 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3035 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3036 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3037 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3038 evac_gen = saved_evac_gen;
3039 failed_to_evac = rtsTrue; // mutable
3040 p += sizeofW(StgTVarWaitQueue);
3046 StgTVar *tvar = ((StgTVar *) p);
3048 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3049 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3051 tvar->last_update_by = (StgTRecHeader *)evacuate((StgClosure*)tvar->last_update_by);
3053 evac_gen = saved_evac_gen;
3054 failed_to_evac = rtsTrue; // mutable
3055 p += sizeofW(StgTVar);
3061 StgTRecHeader *trec = ((StgTRecHeader *) p);
3063 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3064 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3065 evac_gen = saved_evac_gen;
3066 failed_to_evac = rtsTrue; // mutable
3067 p += sizeofW(StgTRecHeader);
3074 StgTRecChunk *tc = ((StgTRecChunk *) p);
3075 TRecEntry *e = &(tc -> entries[0]);
3077 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3078 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3079 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3080 e->expected_value = evacuate((StgClosure*)e->expected_value);
3081 e->new_value = evacuate((StgClosure*)e->new_value);
3083 evac_gen = saved_evac_gen;
3084 failed_to_evac = rtsTrue; // mutable
3085 p += sizeofW(StgTRecChunk);
3090 barf("scavenge: unimplemented/strange closure type %d @ %p",
3095 * We need to record the current object on the mutable list if
3096 * (a) It is actually mutable, or
3097 * (b) It contains pointers to a younger generation.
3098 * Case (b) arises if we didn't manage to promote everything that
3099 * the current object points to into the current generation.
3101 if (failed_to_evac) {
3102 failed_to_evac = rtsFalse;
3103 if (stp->gen_no > 0) {
3104 recordMutableGen((StgClosure *)q, stp->gen);
3113 /* -----------------------------------------------------------------------------
3114 Scavenge everything on the mark stack.
3116 This is slightly different from scavenge():
3117 - we don't walk linearly through the objects, so the scavenger
3118 doesn't need to advance the pointer on to the next object.
3119 -------------------------------------------------------------------------- */
3122 scavenge_mark_stack(void)
3128 evac_gen = oldest_gen->no;
3129 saved_evac_gen = evac_gen;
3132 while (!mark_stack_empty()) {
3133 p = pop_mark_stack();
3135 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3136 info = get_itbl((StgClosure *)p);
3139 switch (info->type) {
3143 StgMVar *mvar = ((StgMVar *)p);
3145 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
3146 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
3147 mvar->value = evacuate((StgClosure *)mvar->value);
3148 evac_gen = saved_evac_gen;
3149 failed_to_evac = rtsTrue; // mutable.
3154 scavenge_fun_srt(info);
3155 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
3156 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3160 scavenge_thunk_srt(info);
3161 ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
3162 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
3166 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
3167 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3172 scavenge_fun_srt(info);
3173 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3178 scavenge_thunk_srt(info);
3179 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
3184 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3189 scavenge_fun_srt(info);
3194 scavenge_thunk_srt(info);
3202 scavenge_fun_srt(info);
3209 scavenge_thunk_srt(info);
3210 end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
3211 for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
3212 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3224 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3225 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
3226 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3232 StgBCO *bco = (StgBCO *)p;
3233 bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
3234 bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
3235 bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
3236 bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
3241 // don't need to do anything here: the only possible case
3242 // is that we're in a 1-space compacting collector, with
3243 // no "old" generation.
3247 case IND_OLDGEN_PERM:
3248 ((StgInd *)p)->indirectee =
3249 evacuate(((StgInd *)p)->indirectee);
3254 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3255 evac_gen = saved_evac_gen;
3256 failed_to_evac = rtsTrue;
3260 case SE_CAF_BLACKHOLE:
3266 case THUNK_SELECTOR:
3268 StgSelector *s = (StgSelector *)p;
3269 s->selectee = evacuate(s->selectee);
3273 // A chunk of stack saved in a heap object
3276 StgAP_STACK *ap = (StgAP_STACK *)p;
3278 ap->fun = evacuate(ap->fun);
3279 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3284 scavenge_PAP((StgPAP *)p);
3288 scavenge_AP((StgAP *)p);
3292 // follow everything
3296 evac_gen = 0; // repeatedly mutable
3297 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3298 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3299 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3301 evac_gen = saved_evac_gen;
3302 failed_to_evac = rtsTrue; // mutable anyhow.
3306 case MUT_ARR_PTRS_FROZEN:
3307 case MUT_ARR_PTRS_FROZEN0:
3308 // follow everything
3312 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3313 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3314 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3321 StgTSO *tso = (StgTSO *)p;
3324 evac_gen = saved_evac_gen;
3325 failed_to_evac = rtsTrue;
3333 nat size, ptrs, nonptrs, vhs;
3335 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3337 StgRBH *rbh = (StgRBH *)p;
3338 bh->blocking_queue =
3339 (StgTSO *)evacuate((StgClosure *)bh->blocking_queue);
3340 failed_to_evac = rtsTrue; // mutable anyhow.
3342 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3343 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3349 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3350 // follow the pointer to the node which is being demanded
3351 (StgClosure *)bf->node =
3352 evacuate((StgClosure *)bf->node);
3353 // follow the link to the rest of the blocking queue
3354 (StgClosure *)bf->link =
3355 evacuate((StgClosure *)bf->link);
3357 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3358 bf, info_type((StgClosure *)bf),
3359 bf->node, info_type(bf->node)));
3367 break; // nothing to do in this case
3371 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3372 (StgClosure *)fmbq->blocking_queue =
3373 evacuate((StgClosure *)fmbq->blocking_queue);
3375 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3376 p, info_type((StgClosure *)p)));
3381 case TVAR_WAIT_QUEUE:
3383 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3385 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3386 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3387 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3388 evac_gen = saved_evac_gen;
3389 failed_to_evac = rtsTrue; // mutable
3395 StgTVar *tvar = ((StgTVar *) p);
3397 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3398 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3400 tvar->last_update_by = (StgTRecHeader *)evacuate((StgClosure*)tvar->last_update_by);
3402 evac_gen = saved_evac_gen;
3403 failed_to_evac = rtsTrue; // mutable
3410 StgTRecChunk *tc = ((StgTRecChunk *) p);
3411 TRecEntry *e = &(tc -> entries[0]);
3413 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3414 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3415 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3416 e->expected_value = evacuate((StgClosure*)e->expected_value);
3417 e->new_value = evacuate((StgClosure*)e->new_value);
3419 evac_gen = saved_evac_gen;
3420 failed_to_evac = rtsTrue; // mutable
3426 StgTRecHeader *trec = ((StgTRecHeader *) p);
3428 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3429 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3430 evac_gen = saved_evac_gen;
3431 failed_to_evac = rtsTrue; // mutable
3436 barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p",
3440 if (failed_to_evac) {
3441 failed_to_evac = rtsFalse;
3443 recordMutableGen((StgClosure *)q, &generations[evac_gen]);
3447 // mark the next bit to indicate "scavenged"
3448 mark(q+1, Bdescr(q));
3450 } // while (!mark_stack_empty())
3452 // start a new linear scan if the mark stack overflowed at some point
3453 if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
3454 IF_DEBUG(gc, debugBelch("scavenge_mark_stack: starting linear scan"));
3455 mark_stack_overflowed = rtsFalse;
3456 oldgen_scan_bd = oldest_gen->steps[0].old_blocks;
3457 oldgen_scan = oldgen_scan_bd->start;
3460 if (oldgen_scan_bd) {
3461 // push a new thing on the mark stack
3463 // find a closure that is marked but not scavenged, and start
3465 while (oldgen_scan < oldgen_scan_bd->free
3466 && !is_marked(oldgen_scan,oldgen_scan_bd)) {
3470 if (oldgen_scan < oldgen_scan_bd->free) {
3472 // already scavenged?
3473 if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
3474 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3477 push_mark_stack(oldgen_scan);
3478 // ToDo: bump the linear scan by the actual size of the object
3479 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3483 oldgen_scan_bd = oldgen_scan_bd->link;
3484 if (oldgen_scan_bd != NULL) {
3485 oldgen_scan = oldgen_scan_bd->start;
3491 /* -----------------------------------------------------------------------------
3492 Scavenge one object.
3494 This is used for objects that are temporarily marked as mutable
3495 because they contain old-to-new generation pointers. Only certain
3496 objects can have this property.
3497 -------------------------------------------------------------------------- */
3500 scavenge_one(StgPtr p)
3502 const StgInfoTable *info;
3503 nat saved_evac_gen = evac_gen;
3506 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3507 info = get_itbl((StgClosure *)p);
3509 switch (info->type) {
3513 StgMVar *mvar = ((StgMVar *)p);
3515 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
3516 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
3517 mvar->value = evacuate((StgClosure *)mvar->value);
3518 evac_gen = saved_evac_gen;
3519 failed_to_evac = rtsTrue; // mutable.
3532 end = (StgPtr)((StgThunk *)p)->payload + info->layout.payload.ptrs;
3533 for (q = (StgPtr)((StgThunk *)p)->payload; q < end; q++) {
3534 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3540 case FUN_1_0: // hardly worth specialising these guys
3556 end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3557 for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
3558 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3565 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3566 evac_gen = saved_evac_gen;
3567 failed_to_evac = rtsTrue; // mutable anyhow
3571 case SE_CAF_BLACKHOLE:
3576 case THUNK_SELECTOR:
3578 StgSelector *s = (StgSelector *)p;
3579 s->selectee = evacuate(s->selectee);
3585 StgAP_STACK *ap = (StgAP_STACK *)p;
3587 ap->fun = evacuate(ap->fun);
3588 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3589 p = (StgPtr)ap->payload + ap->size;
3594 p = scavenge_PAP((StgPAP *)p);
3598 p = scavenge_AP((StgAP *)p);
3602 // nothing to follow
3607 // follow everything
3610 evac_gen = 0; // repeatedly mutable
3611 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3612 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3613 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3615 evac_gen = saved_evac_gen;
3616 failed_to_evac = rtsTrue;
3620 case MUT_ARR_PTRS_FROZEN:
3621 case MUT_ARR_PTRS_FROZEN0:
3623 // follow everything
3626 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3627 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3628 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3635 StgTSO *tso = (StgTSO *)p;
3637 evac_gen = 0; // repeatedly mutable
3639 evac_gen = saved_evac_gen;
3640 failed_to_evac = rtsTrue;
3648 nat size, ptrs, nonptrs, vhs;
3650 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3652 StgRBH *rbh = (StgRBH *)p;
3653 (StgClosure *)rbh->blocking_queue =
3654 evacuate((StgClosure *)rbh->blocking_queue);
3655 failed_to_evac = rtsTrue; // mutable anyhow.
3657 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3658 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3659 // ToDo: use size of reverted closure here!
3665 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3666 // follow the pointer to the node which is being demanded
3667 (StgClosure *)bf->node =
3668 evacuate((StgClosure *)bf->node);
3669 // follow the link to the rest of the blocking queue
3670 (StgClosure *)bf->link =
3671 evacuate((StgClosure *)bf->link);
3673 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3674 bf, info_type((StgClosure *)bf),
3675 bf->node, info_type(bf->node)));
3683 break; // nothing to do in this case
3687 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3688 (StgClosure *)fmbq->blocking_queue =
3689 evacuate((StgClosure *)fmbq->blocking_queue);
3691 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3692 p, info_type((StgClosure *)p)));
3697 case TVAR_WAIT_QUEUE:
3699 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3701 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3702 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3703 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3704 evac_gen = saved_evac_gen;
3705 failed_to_evac = rtsTrue; // mutable
3711 StgTVar *tvar = ((StgTVar *) p);
3713 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3714 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3716 tvar->last_update_by = (StgTRecHeader *)evacuate((StgClosure*)tvar->last_update_by);
3718 evac_gen = saved_evac_gen;
3719 failed_to_evac = rtsTrue; // mutable
3725 StgTRecHeader *trec = ((StgTRecHeader *) p);
3727 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3728 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3729 evac_gen = saved_evac_gen;
3730 failed_to_evac = rtsTrue; // mutable
3737 StgTRecChunk *tc = ((StgTRecChunk *) p);
3738 TRecEntry *e = &(tc -> entries[0]);
3740 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3741 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3742 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3743 e->expected_value = evacuate((StgClosure*)e->expected_value);
3744 e->new_value = evacuate((StgClosure*)e->new_value);
3746 evac_gen = saved_evac_gen;
3747 failed_to_evac = rtsTrue; // mutable
3752 case IND_OLDGEN_PERM:
3755 /* Careful here: a THUNK can be on the mutable list because
3756 * it contains pointers to young gen objects. If such a thunk
3757 * is updated, the IND_OLDGEN will be added to the mutable
3758 * list again, and we'll scavenge it twice. evacuate()
3759 * doesn't check whether the object has already been
3760 * evacuated, so we perform that check here.
3762 StgClosure *q = ((StgInd *)p)->indirectee;
3763 if (HEAP_ALLOCED(q) && Bdescr((StgPtr)q)->flags & BF_EVACUATED) {
3766 ((StgInd *)p)->indirectee = evacuate(q);
3769 #if 0 && defined(DEBUG)
3770 if (RtsFlags.DebugFlags.gc)
3771 /* Debugging code to print out the size of the thing we just
3775 StgPtr start = gen->steps[0].scan;
3776 bdescr *start_bd = gen->steps[0].scan_bd;
3778 scavenge(&gen->steps[0]);
3779 if (start_bd != gen->steps[0].scan_bd) {
3780 size += (P_)BLOCK_ROUND_UP(start) - start;
3781 start_bd = start_bd->link;
3782 while (start_bd != gen->steps[0].scan_bd) {
3783 size += BLOCK_SIZE_W;
3784 start_bd = start_bd->link;
3786 size += gen->steps[0].scan -
3787 (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
3789 size = gen->steps[0].scan - start;
3791 debugBelch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
3797 barf("scavenge_one: strange object %d", (int)(info->type));
3800 no_luck = failed_to_evac;
3801 failed_to_evac = rtsFalse;
3805 /* -----------------------------------------------------------------------------
3806 Scavenging mutable lists.
3808 We treat the mutable list of each generation > N (i.e. all the
3809 generations older than the one being collected) as roots. We also
3810 remove non-mutable objects from the mutable list at this point.
3811 -------------------------------------------------------------------------- */
3814 scavenge_mutable_list(generation *gen)
3819 bd = gen->saved_mut_list;
3822 for (; bd != NULL; bd = bd->link) {
3823 for (q = bd->start; q < bd->free; q++) {
3825 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3826 if (scavenge_one(p)) {
3827 /* didn't manage to promote everything, so put the
3828 * object back on the list.
3830 recordMutableGen((StgClosure *)p,gen);
3835 // free the old mut_list
3836 freeChain(gen->saved_mut_list);
3837 gen->saved_mut_list = NULL;
3842 scavenge_static(void)
3844 StgClosure* p = static_objects;
3845 const StgInfoTable *info;
3847 /* Always evacuate straight to the oldest generation for static
3849 evac_gen = oldest_gen->no;
3851 /* keep going until we've scavenged all the objects on the linked
3853 while (p != END_OF_STATIC_LIST) {
3855 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3858 if (info->type==RBH)
3859 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3861 // make sure the info pointer is into text space
3863 /* Take this object *off* the static_objects list,
3864 * and put it on the scavenged_static_objects list.
3866 static_objects = *STATIC_LINK(info,p);
3867 *STATIC_LINK(info,p) = scavenged_static_objects;
3868 scavenged_static_objects = p;
3870 switch (info -> type) {
3874 StgInd *ind = (StgInd *)p;
3875 ind->indirectee = evacuate(ind->indirectee);
3877 /* might fail to evacuate it, in which case we have to pop it
3878 * back on the mutable list of the oldest generation. We
3879 * leave it *on* the scavenged_static_objects list, though,
3880 * in case we visit this object again.
3882 if (failed_to_evac) {
3883 failed_to_evac = rtsFalse;
3884 recordMutableGen((StgClosure *)p,oldest_gen);
3890 scavenge_thunk_srt(info);
3894 scavenge_fun_srt(info);
3901 next = (P_)p->payload + info->layout.payload.ptrs;
3902 // evacuate the pointers
3903 for (q = (P_)p->payload; q < next; q++) {
3904 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3910 barf("scavenge_static: strange closure %d", (int)(info->type));
3913 ASSERT(failed_to_evac == rtsFalse);
3915 /* get the next static object from the list. Remember, there might
3916 * be more stuff on this list now that we've done some evacuating!
3917 * (static_objects is a global)
3923 /* -----------------------------------------------------------------------------
3924 scavenge a chunk of memory described by a bitmap
3925 -------------------------------------------------------------------------- */
3928 scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
3934 bitmap = large_bitmap->bitmap[b];
3935 for (i = 0; i < size; ) {
3936 if ((bitmap & 1) == 0) {
3937 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3941 if (i % BITS_IN(W_) == 0) {
3943 bitmap = large_bitmap->bitmap[b];
3945 bitmap = bitmap >> 1;
3950 STATIC_INLINE StgPtr
3951 scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap)
3954 if ((bitmap & 1) == 0) {
3955 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3958 bitmap = bitmap >> 1;
3964 /* -----------------------------------------------------------------------------
3965 scavenge_stack walks over a section of stack and evacuates all the
3966 objects pointed to by it. We can use the same code for walking
3967 AP_STACK_UPDs, since these are just sections of copied stack.
3968 -------------------------------------------------------------------------- */
3972 scavenge_stack(StgPtr p, StgPtr stack_end)
3974 const StgRetInfoTable* info;
3978 //IF_DEBUG(sanity, debugBelch(" scavenging stack between %p and %p", p, stack_end));
3981 * Each time around this loop, we are looking at a chunk of stack
3982 * that starts with an activation record.
3985 while (p < stack_end) {
3986 info = get_ret_itbl((StgClosure *)p);
3988 switch (info->i.type) {
3991 ((StgUpdateFrame *)p)->updatee
3992 = evacuate(((StgUpdateFrame *)p)->updatee);
3993 p += sizeofW(StgUpdateFrame);
3996 // small bitmap (< 32 entries, or 64 on a 64-bit machine)
3997 case CATCH_STM_FRAME:
3998 case CATCH_RETRY_FRAME:
3999 case ATOMICALLY_FRAME:
4004 bitmap = BITMAP_BITS(info->i.layout.bitmap);
4005 size = BITMAP_SIZE(info->i.layout.bitmap);
4006 // NOTE: the payload starts immediately after the info-ptr, we
4007 // don't have an StgHeader in the same sense as a heap closure.
4009 p = scavenge_small_bitmap(p, size, bitmap);
4013 scavenge_srt((StgClosure **)GET_SRT(info), info->i.srt_bitmap);
4021 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
4024 size = BCO_BITMAP_SIZE(bco);
4025 scavenge_large_bitmap(p, BCO_BITMAP(bco), size);
4030 // large bitmap (> 32 entries, or > 64 on a 64-bit machine)
4036 size = GET_LARGE_BITMAP(&info->i)->size;
4038 scavenge_large_bitmap(p, GET_LARGE_BITMAP(&info->i), size);
4040 // and don't forget to follow the SRT
4044 // Dynamic bitmap: the mask is stored on the stack, and
4045 // there are a number of non-pointers followed by a number
4046 // of pointers above the bitmapped area. (see StgMacros.h,
4051 dyn = ((StgRetDyn *)p)->liveness;
4053 // traverse the bitmap first
4054 bitmap = RET_DYN_LIVENESS(dyn);
4055 p = (P_)&((StgRetDyn *)p)->payload[0];
4056 size = RET_DYN_BITMAP_SIZE;
4057 p = scavenge_small_bitmap(p, size, bitmap);
4059 // skip over the non-ptr words
4060 p += RET_DYN_NONPTRS(dyn) + RET_DYN_NONPTR_REGS_SIZE;
4062 // follow the ptr words
4063 for (size = RET_DYN_PTRS(dyn); size > 0; size--) {
4064 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
4072 StgRetFun *ret_fun = (StgRetFun *)p;
4073 StgFunInfoTable *fun_info;
4075 ret_fun->fun = evacuate(ret_fun->fun);
4076 fun_info = get_fun_itbl(ret_fun->fun);
4077 p = scavenge_arg_block(fun_info, ret_fun->payload);
4082 barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->i.type));
4087 /*-----------------------------------------------------------------------------
4088 scavenge the large object list.
4090 evac_gen set by caller; similar games played with evac_gen as with
4091 scavenge() - see comment at the top of scavenge(). Most large
4092 objects are (repeatedly) mutable, so most of the time evac_gen will
4094 --------------------------------------------------------------------------- */
4097 scavenge_large(step *stp)
4102 bd = stp->new_large_objects;
4104 for (; bd != NULL; bd = stp->new_large_objects) {
4106 /* take this object *off* the large objects list and put it on
4107 * the scavenged large objects list. This is so that we can
4108 * treat new_large_objects as a stack and push new objects on
4109 * the front when evacuating.
4111 stp->new_large_objects = bd->link;
4112 dbl_link_onto(bd, &stp->scavenged_large_objects);
4114 // update the block count in this step.
4115 stp->n_scavenged_large_blocks += bd->blocks;
4118 if (scavenge_one(p)) {
4119 if (stp->gen_no > 0) {
4120 recordMutableGen((StgClosure *)p, stp->gen);
4126 /* -----------------------------------------------------------------------------
4127 Initialising the static object & mutable lists
4128 -------------------------------------------------------------------------- */
4131 zero_static_object_list(StgClosure* first_static)
4135 const StgInfoTable *info;
4137 for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
4139 link = *STATIC_LINK(info, p);
4140 *STATIC_LINK(info,p) = NULL;
4144 /* -----------------------------------------------------------------------------
4146 -------------------------------------------------------------------------- */
4153 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
4154 c = (StgIndStatic *)c->static_link)
4156 SET_INFO(c, c->saved_info);
4157 c->saved_info = NULL;
4158 // could, but not necessary: c->static_link = NULL;
4160 revertible_caf_list = NULL;
4164 markCAFs( evac_fn evac )
4168 for (c = (StgIndStatic *)caf_list; c != NULL;
4169 c = (StgIndStatic *)c->static_link)
4171 evac(&c->indirectee);
4173 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
4174 c = (StgIndStatic *)c->static_link)
4176 evac(&c->indirectee);
4180 /* -----------------------------------------------------------------------------
4181 Sanity code for CAF garbage collection.
4183 With DEBUG turned on, we manage a CAF list in addition to the SRT
4184 mechanism. After GC, we run down the CAF list and blackhole any
4185 CAFs which have been garbage collected. This means we get an error
4186 whenever the program tries to enter a garbage collected CAF.
4188 Any garbage collected CAFs are taken off the CAF list at the same
4190 -------------------------------------------------------------------------- */
4192 #if 0 && defined(DEBUG)
4199 const StgInfoTable *info;
4210 ASSERT(info->type == IND_STATIC);
4212 if (STATIC_LINK(info,p) == NULL) {
4213 IF_DEBUG(gccafs, debugBelch("CAF gc'd at 0x%04lx", (long)p));
4215 SET_INFO(p,&stg_BLACKHOLE_info);
4216 p = STATIC_LINK2(info,p);
4220 pp = &STATIC_LINK2(info,p);
4227 // debugBelch("%d CAFs live", i);
4232 /* -----------------------------------------------------------------------------
4235 Whenever a thread returns to the scheduler after possibly doing
4236 some work, we have to run down the stack and black-hole all the
4237 closures referred to by update frames.
4238 -------------------------------------------------------------------------- */
4241 threadLazyBlackHole(StgTSO *tso)
4244 StgRetInfoTable *info;
4248 stack_end = &tso->stack[tso->stack_size];
4250 frame = (StgClosure *)tso->sp;
4253 info = get_ret_itbl(frame);
4255 switch (info->i.type) {
4258 bh = ((StgUpdateFrame *)frame)->updatee;
4260 /* if the thunk is already blackholed, it means we've also
4261 * already blackholed the rest of the thunks on this stack,
4262 * so we can stop early.
4264 * The blackhole made for a CAF is a CAF_BLACKHOLE, so they
4265 * don't interfere with this optimisation.
4267 if (bh->header.info == &stg_BLACKHOLE_info) {
4271 if (bh->header.info != &stg_CAF_BLACKHOLE_info) {
4272 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4273 debugBelch("Unexpected lazy BHing required at 0x%04lx\n",(long)bh);
4277 // We pretend that bh is now dead.
4278 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4280 SET_INFO(bh,&stg_BLACKHOLE_info);
4282 // We pretend that bh has just been created.
4283 LDV_RECORD_CREATE(bh);
4286 frame = (StgClosure *) ((StgUpdateFrame *)frame + 1);
4292 // normal stack frames; do nothing except advance the pointer
4294 frame = (StgClosure *)((StgPtr)frame + stack_frame_sizeW(frame));
4300 /* -----------------------------------------------------------------------------
4303 * Code largely pinched from old RTS, then hacked to bits. We also do
4304 * lazy black holing here.
4306 * -------------------------------------------------------------------------- */
4308 struct stack_gap { StgWord gap_size; struct stack_gap *next_gap; };
4311 threadSqueezeStack(StgTSO *tso)
4314 rtsBool prev_was_update_frame;
4315 StgClosure *updatee = NULL;
4317 StgRetInfoTable *info;
4318 StgWord current_gap_size;
4319 struct stack_gap *gap;
4322 // Traverse the stack upwards, replacing adjacent update frames
4323 // with a single update frame and a "stack gap". A stack gap
4324 // contains two values: the size of the gap, and the distance
4325 // to the next gap (or the stack top).
4327 bottom = &(tso->stack[tso->stack_size]);
4331 ASSERT(frame < bottom);
4333 prev_was_update_frame = rtsFalse;
4334 current_gap_size = 0;
4335 gap = (struct stack_gap *) (tso->sp - sizeofW(StgUpdateFrame));
4337 while (frame < bottom) {
4339 info = get_ret_itbl((StgClosure *)frame);
4340 switch (info->i.type) {
4344 StgUpdateFrame *upd = (StgUpdateFrame *)frame;
4346 if (upd->updatee->header.info == &stg_BLACKHOLE_info) {
4348 // found a BLACKHOLE'd update frame; we've been here
4349 // before, in a previous GC, so just break out.
4351 // Mark the end of the gap, if we're in one.
4352 if (current_gap_size != 0) {
4353 gap = (struct stack_gap *)(frame-sizeofW(StgUpdateFrame));
4356 frame += sizeofW(StgUpdateFrame);
4357 goto done_traversing;
4360 if (prev_was_update_frame) {
4362 TICK_UPD_SQUEEZED();
4363 /* wasn't there something about update squeezing and ticky to be
4364 * sorted out? oh yes: we aren't counting each enter properly
4365 * in this case. See the log somewhere. KSW 1999-04-21
4367 * Check two things: that the two update frames don't point to
4368 * the same object, and that the updatee_bypass isn't already an
4369 * indirection. Both of these cases only happen when we're in a
4370 * block hole-style loop (and there are multiple update frames
4371 * on the stack pointing to the same closure), but they can both
4372 * screw us up if we don't check.
4374 if (upd->updatee != updatee && !closure_IND(upd->updatee)) {
4375 UPD_IND_NOLOCK(upd->updatee, updatee);
4378 // now mark this update frame as a stack gap. The gap
4379 // marker resides in the bottom-most update frame of
4380 // the series of adjacent frames, and covers all the
4381 // frames in this series.
4382 current_gap_size += sizeofW(StgUpdateFrame);
4383 ((struct stack_gap *)frame)->gap_size = current_gap_size;
4384 ((struct stack_gap *)frame)->next_gap = gap;
4386 frame += sizeofW(StgUpdateFrame);
4390 // single update frame, or the topmost update frame in a series
4392 StgClosure *bh = upd->updatee;
4394 // Do lazy black-holing
4395 if (bh->header.info != &stg_BLACKHOLE_info &&
4396 bh->header.info != &stg_CAF_BLACKHOLE_info) {
4397 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4398 debugBelch("Unexpected lazy BHing required at 0x%04lx",(long)bh);
4401 // zero out the slop so that the sanity checker can tell
4402 // where the next closure is.
4403 DEBUG_FILL_SLOP(bh);
4406 // We pretend that bh is now dead.
4407 // ToDo: is the slop filling the same as DEBUG_FILL_SLOP?
4408 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4410 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
4411 SET_INFO(bh,&stg_BLACKHOLE_info);
4413 // We pretend that bh has just been created.
4414 LDV_RECORD_CREATE(bh);
4417 prev_was_update_frame = rtsTrue;
4418 updatee = upd->updatee;
4419 frame += sizeofW(StgUpdateFrame);
4425 prev_was_update_frame = rtsFalse;
4427 // we're not in a gap... check whether this is the end of a gap
4428 // (an update frame can't be the end of a gap).
4429 if (current_gap_size != 0) {
4430 gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
4432 current_gap_size = 0;
4434 frame += stack_frame_sizeW((StgClosure *)frame);
4441 // Now we have a stack with gaps in it, and we have to walk down
4442 // shoving the stack up to fill in the gaps. A diagram might
4446 // | ********* | <- sp
4450 // | stack_gap | <- gap | chunk_size
4452 // | ......... | <- gap_end v
4458 // 'sp' points the the current top-of-stack
4459 // 'gap' points to the stack_gap structure inside the gap
4460 // ***** indicates real stack data
4461 // ..... indicates gap
4462 // <empty> indicates unused
4466 void *gap_start, *next_gap_start, *gap_end;
4469 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4470 sp = next_gap_start;
4472 while ((StgPtr)gap > tso->sp) {
4474 // we're working in *bytes* now...
4475 gap_start = next_gap_start;
4476 gap_end = (void*) ((unsigned char*)gap_start - gap->gap_size * sizeof(W_));
4478 gap = gap->next_gap;
4479 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4481 chunk_size = (unsigned char*)gap_end - (unsigned char*)next_gap_start;
4483 memmove(sp, next_gap_start, chunk_size);
4486 tso->sp = (StgPtr)sp;
4490 /* -----------------------------------------------------------------------------
4493 * We have to prepare for GC - this means doing lazy black holing
4494 * here. We also take the opportunity to do stack squeezing if it's
4496 * -------------------------------------------------------------------------- */
4498 threadPaused(StgTSO *tso)
4500 if ( RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue )
4501 threadSqueezeStack(tso); // does black holing too
4503 threadLazyBlackHole(tso);
4506 /* -----------------------------------------------------------------------------
4508 * -------------------------------------------------------------------------- */
4512 printMutableList(generation *gen)
4517 debugBelch("@@ Mutable list %p: ", gen->mut_list);
4519 for (bd = gen->mut_list; bd != NULL; bd = bd->link) {
4520 for (p = bd->start; p < bd->free; p++) {
4521 debugBelch("%p (%s), ", (void *)*p, info_type((StgClosure *)*p));