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
1140 scheduleFinalizers(last_free_capability, old_weak_ptr_list);
1142 // send exceptions to any threads which were about to die
1143 resurrectThreads(resurrected_threads);
1145 // Update the stable pointer hash table.
1146 updateStablePtrTable(major_gc);
1148 // check sanity after GC
1149 IF_DEBUG(sanity, checkSanity());
1151 // extra GC trace info
1152 IF_DEBUG(gc, statDescribeGens());
1155 // symbol-table based profiling
1156 /* heapCensus(to_blocks); */ /* ToDo */
1159 // restore enclosing cost centre
1165 // check for memory leaks if DEBUG is on
1169 #ifdef RTS_GTK_FRONTPANEL
1170 if (RtsFlags.GcFlags.frontpanel) {
1171 updateFrontPanelAfterGC( N, live );
1175 // ok, GC over: tell the stats department what happened.
1176 stat_endGC(allocated, collected, live, copied, scavd_copied, N);
1178 #if defined(RTS_USER_SIGNALS)
1179 // unblock signals again
1180 unblockUserSignals();
1189 /* -----------------------------------------------------------------------------
1192 traverse_weak_ptr_list is called possibly many times during garbage
1193 collection. It returns a flag indicating whether it did any work
1194 (i.e. called evacuate on any live pointers).
1196 Invariant: traverse_weak_ptr_list is called when the heap is in an
1197 idempotent state. That means that there are no pending
1198 evacuate/scavenge operations. This invariant helps the weak
1199 pointer code decide which weak pointers are dead - if there are no
1200 new live weak pointers, then all the currently unreachable ones are
1203 For generational GC: we just don't try to finalize weak pointers in
1204 older generations than the one we're collecting. This could
1205 probably be optimised by keeping per-generation lists of weak
1206 pointers, but for a few weak pointers this scheme will work.
1208 There are three distinct stages to processing weak pointers:
1210 - weak_stage == WeakPtrs
1212 We process all the weak pointers whos keys are alive (evacuate
1213 their values and finalizers), and repeat until we can find no new
1214 live keys. If no live keys are found in this pass, then we
1215 evacuate the finalizers of all the dead weak pointers in order to
1218 - weak_stage == WeakThreads
1220 Now, we discover which *threads* are still alive. Pointers to
1221 threads from the all_threads and main thread lists are the
1222 weakest of all: a pointers from the finalizer of a dead weak
1223 pointer can keep a thread alive. Any threads found to be unreachable
1224 are evacuated and placed on the resurrected_threads list so we
1225 can send them a signal later.
1227 - weak_stage == WeakDone
1229 No more evacuation is done.
1231 -------------------------------------------------------------------------- */
1234 traverse_weak_ptr_list(void)
1236 StgWeak *w, **last_w, *next_w;
1238 rtsBool flag = rtsFalse;
1240 switch (weak_stage) {
1246 /* doesn't matter where we evacuate values/finalizers to, since
1247 * these pointers are treated as roots (iff the keys are alive).
1251 last_w = &old_weak_ptr_list;
1252 for (w = old_weak_ptr_list; w != NULL; w = next_w) {
1254 /* There might be a DEAD_WEAK on the list if finalizeWeak# was
1255 * called on a live weak pointer object. Just remove it.
1257 if (w->header.info == &stg_DEAD_WEAK_info) {
1258 next_w = ((StgDeadWeak *)w)->link;
1263 switch (get_itbl(w)->type) {
1266 next_w = (StgWeak *)((StgEvacuated *)w)->evacuee;
1271 /* Now, check whether the key is reachable.
1273 new = isAlive(w->key);
1276 // evacuate the value and finalizer
1277 w->value = evacuate(w->value);
1278 w->finalizer = evacuate(w->finalizer);
1279 // remove this weak ptr from the old_weak_ptr list
1281 // and put it on the new weak ptr list
1283 w->link = weak_ptr_list;
1286 IF_DEBUG(weak, debugBelch("Weak pointer still alive at %p -> %p",
1291 last_w = &(w->link);
1297 barf("traverse_weak_ptr_list: not WEAK");
1301 /* If we didn't make any changes, then we can go round and kill all
1302 * the dead weak pointers. The old_weak_ptr list is used as a list
1303 * of pending finalizers later on.
1305 if (flag == rtsFalse) {
1306 for (w = old_weak_ptr_list; w; w = w->link) {
1307 w->finalizer = evacuate(w->finalizer);
1310 // Next, move to the WeakThreads stage after fully
1311 // scavenging the finalizers we've just evacuated.
1312 weak_stage = WeakThreads;
1318 /* Now deal with the all_threads list, which behaves somewhat like
1319 * the weak ptr list. If we discover any threads that are about to
1320 * become garbage, we wake them up and administer an exception.
1323 StgTSO *t, *tmp, *next, **prev;
1325 prev = &old_all_threads;
1326 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1328 tmp = (StgTSO *)isAlive((StgClosure *)t);
1334 ASSERT(get_itbl(t)->type == TSO);
1335 switch (t->what_next) {
1336 case ThreadRelocated:
1341 case ThreadComplete:
1342 // finshed or died. The thread might still be alive, but we
1343 // don't keep it on the all_threads list. Don't forget to
1344 // stub out its global_link field.
1345 next = t->global_link;
1346 t->global_link = END_TSO_QUEUE;
1353 // Threads blocked on black holes: if the black hole
1354 // is alive, then the thread is alive too.
1355 if (tmp == NULL && t->why_blocked == BlockedOnBlackHole) {
1356 if (isAlive(t->block_info.closure)) {
1357 t = (StgTSO *)evacuate((StgClosure *)t);
1364 // not alive (yet): leave this thread on the
1365 // old_all_threads list.
1366 prev = &(t->global_link);
1367 next = t->global_link;
1370 // alive: move this thread onto the all_threads list.
1371 next = t->global_link;
1372 t->global_link = all_threads;
1379 /* If we evacuated any threads, we need to go back to the scavenger.
1381 if (flag) return rtsTrue;
1383 /* And resurrect any threads which were about to become garbage.
1386 StgTSO *t, *tmp, *next;
1387 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
1388 next = t->global_link;
1389 tmp = (StgTSO *)evacuate((StgClosure *)t);
1390 tmp->global_link = resurrected_threads;
1391 resurrected_threads = tmp;
1395 /* Finally, we can update the blackhole_queue. This queue
1396 * simply strings together TSOs blocked on black holes, it is
1397 * not intended to keep anything alive. Hence, we do not follow
1398 * pointers on the blackhole_queue until now, when we have
1399 * determined which TSOs are otherwise reachable. We know at
1400 * this point that all TSOs have been evacuated, however.
1404 for (pt = &blackhole_queue; *pt != END_TSO_QUEUE; pt = &((*pt)->link)) {
1405 *pt = (StgTSO *)isAlive((StgClosure *)*pt);
1406 ASSERT(*pt != NULL);
1410 weak_stage = WeakDone; // *now* we're done,
1411 return rtsTrue; // but one more round of scavenging, please
1414 barf("traverse_weak_ptr_list");
1420 /* -----------------------------------------------------------------------------
1421 After GC, the live weak pointer list may have forwarding pointers
1422 on it, because a weak pointer object was evacuated after being
1423 moved to the live weak pointer list. We remove those forwarding
1426 Also, we don't consider weak pointer objects to be reachable, but
1427 we must nevertheless consider them to be "live" and retain them.
1428 Therefore any weak pointer objects which haven't as yet been
1429 evacuated need to be evacuated now.
1430 -------------------------------------------------------------------------- */
1434 mark_weak_ptr_list ( StgWeak **list )
1436 StgWeak *w, **last_w;
1439 for (w = *list; w; w = w->link) {
1440 // w might be WEAK, EVACUATED, or DEAD_WEAK (actually CON_STATIC) here
1441 ASSERT(w->header.info == &stg_DEAD_WEAK_info
1442 || get_itbl(w)->type == WEAK || get_itbl(w)->type == EVACUATED);
1443 w = (StgWeak *)evacuate((StgClosure *)w);
1445 last_w = &(w->link);
1449 /* -----------------------------------------------------------------------------
1450 isAlive determines whether the given closure is still alive (after
1451 a garbage collection) or not. It returns the new address of the
1452 closure if it is alive, or NULL otherwise.
1454 NOTE: Use it before compaction only!
1455 -------------------------------------------------------------------------- */
1459 isAlive(StgClosure *p)
1461 const StgInfoTable *info;
1466 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
1469 // ignore static closures
1471 // ToDo: for static closures, check the static link field.
1472 // Problem here is that we sometimes don't set the link field, eg.
1473 // for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
1475 if (!HEAP_ALLOCED(p)) {
1479 // ignore closures in generations that we're not collecting.
1481 if (bd->gen_no > N) {
1485 // if it's a pointer into to-space, then we're done
1486 if (bd->flags & BF_EVACUATED) {
1490 // large objects use the evacuated flag
1491 if (bd->flags & BF_LARGE) {
1495 // check the mark bit for compacted steps
1496 if ((bd->flags & BF_COMPACTED) && is_marked((P_)p,bd)) {
1500 switch (info->type) {
1505 case IND_OLDGEN: // rely on compatible layout with StgInd
1506 case IND_OLDGEN_PERM:
1507 // follow indirections
1508 p = ((StgInd *)p)->indirectee;
1513 return ((StgEvacuated *)p)->evacuee;
1516 if (((StgTSO *)p)->what_next == ThreadRelocated) {
1517 p = (StgClosure *)((StgTSO *)p)->link;
1530 mark_root(StgClosure **root)
1532 *root = evacuate(*root);
1536 upd_evacuee(StgClosure *p, StgClosure *dest)
1538 // not true: (ToDo: perhaps it should be)
1539 // ASSERT(Bdescr((P_)dest)->flags & BF_EVACUATED);
1540 SET_INFO(p, &stg_EVACUATED_info);
1541 ((StgEvacuated *)p)->evacuee = dest;
1545 STATIC_INLINE StgClosure *
1546 copy(StgClosure *src, nat size, step *stp)
1552 nat size_org = size;
1555 TICK_GC_WORDS_COPIED(size);
1556 /* Find out where we're going, using the handy "to" pointer in
1557 * the step of the source object. If it turns out we need to
1558 * evacuate to an older generation, adjust it here (see comment
1561 if (stp->gen_no < evac_gen) {
1562 #ifdef NO_EAGER_PROMOTION
1563 failed_to_evac = rtsTrue;
1565 stp = &generations[evac_gen].steps[0];
1569 /* chain a new block onto the to-space for the destination step if
1572 if (stp->hp + size >= stp->hpLim) {
1573 gc_alloc_block(stp);
1578 stp->hp = to + size;
1579 for (i = 0; i < size; i++) { // unroll for small i
1582 upd_evacuee((StgClosure *)from,(StgClosure *)to);
1585 // We store the size of the just evacuated object in the LDV word so that
1586 // the profiler can guess the position of the next object later.
1587 SET_EVACUAEE_FOR_LDV(from, size_org);
1589 return (StgClosure *)to;
1592 // Same as copy() above, except the object will be allocated in memory
1593 // that will not be scavenged. Used for object that have no pointer
1595 STATIC_INLINE StgClosure *
1596 copy_noscav(StgClosure *src, nat size, step *stp)
1602 nat size_org = size;
1605 TICK_GC_WORDS_COPIED(size);
1606 /* Find out where we're going, using the handy "to" pointer in
1607 * the step of the source object. If it turns out we need to
1608 * evacuate to an older generation, adjust it here (see comment
1611 if (stp->gen_no < evac_gen) {
1612 #ifdef NO_EAGER_PROMOTION
1613 failed_to_evac = rtsTrue;
1615 stp = &generations[evac_gen].steps[0];
1619 /* chain a new block onto the to-space for the destination step if
1622 if (stp->scavd_hp + size >= stp->scavd_hpLim) {
1623 gc_alloc_scavd_block(stp);
1628 stp->scavd_hp = to + size;
1629 for (i = 0; i < size; i++) { // unroll for small i
1632 upd_evacuee((StgClosure *)from,(StgClosure *)to);
1635 // We store the size of the just evacuated object in the LDV word so that
1636 // the profiler can guess the position of the next object later.
1637 SET_EVACUAEE_FOR_LDV(from, size_org);
1639 return (StgClosure *)to;
1642 /* Special version of copy() for when we only want to copy the info
1643 * pointer of an object, but reserve some padding after it. This is
1644 * used to optimise evacuation of BLACKHOLEs.
1649 copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *stp)
1654 nat size_to_copy_org = size_to_copy;
1657 TICK_GC_WORDS_COPIED(size_to_copy);
1658 if (stp->gen_no < evac_gen) {
1659 #ifdef NO_EAGER_PROMOTION
1660 failed_to_evac = rtsTrue;
1662 stp = &generations[evac_gen].steps[0];
1666 if (stp->hp + size_to_reserve >= stp->hpLim) {
1667 gc_alloc_block(stp);
1670 for(to = stp->hp, from = (P_)src; size_to_copy>0; --size_to_copy) {
1675 stp->hp += size_to_reserve;
1676 upd_evacuee(src,(StgClosure *)dest);
1678 // We store the size of the just evacuated object in the LDV word so that
1679 // the profiler can guess the position of the next object later.
1680 // size_to_copy_org is wrong because the closure already occupies size_to_reserve
1682 SET_EVACUAEE_FOR_LDV(src, size_to_reserve);
1684 if (size_to_reserve - size_to_copy_org > 0)
1685 FILL_SLOP(stp->hp - 1, (int)(size_to_reserve - size_to_copy_org));
1687 return (StgClosure *)dest;
1691 /* -----------------------------------------------------------------------------
1692 Evacuate a large object
1694 This just consists of removing the object from the (doubly-linked)
1695 step->large_objects list, and linking it on to the (singly-linked)
1696 step->new_large_objects list, from where it will be scavenged later.
1698 Convention: bd->flags has BF_EVACUATED set for a large object
1699 that has been evacuated, or unset otherwise.
1700 -------------------------------------------------------------------------- */
1704 evacuate_large(StgPtr p)
1706 bdescr *bd = Bdescr(p);
1709 // object must be at the beginning of the block (or be a ByteArray)
1710 ASSERT(get_itbl((StgClosure *)p)->type == ARR_WORDS ||
1711 (((W_)p & BLOCK_MASK) == 0));
1713 // already evacuated?
1714 if (bd->flags & BF_EVACUATED) {
1715 /* Don't forget to set the failed_to_evac flag if we didn't get
1716 * the desired destination (see comments in evacuate()).
1718 if (bd->gen_no < evac_gen) {
1719 failed_to_evac = rtsTrue;
1720 TICK_GC_FAILED_PROMOTION();
1726 // remove from large_object list
1728 bd->u.back->link = bd->link;
1729 } else { // first object in the list
1730 stp->large_objects = bd->link;
1733 bd->link->u.back = bd->u.back;
1736 /* link it on to the evacuated large object list of the destination step
1739 if (stp->gen_no < evac_gen) {
1740 #ifdef NO_EAGER_PROMOTION
1741 failed_to_evac = rtsTrue;
1743 stp = &generations[evac_gen].steps[0];
1748 bd->gen_no = stp->gen_no;
1749 bd->link = stp->new_large_objects;
1750 stp->new_large_objects = bd;
1751 bd->flags |= BF_EVACUATED;
1754 /* -----------------------------------------------------------------------------
1757 This is called (eventually) for every live object in the system.
1759 The caller to evacuate specifies a desired generation in the
1760 evac_gen global variable. The following conditions apply to
1761 evacuating an object which resides in generation M when we're
1762 collecting up to generation N
1766 else evac to step->to
1768 if M < evac_gen evac to evac_gen, step 0
1770 if the object is already evacuated, then we check which generation
1773 if M >= evac_gen do nothing
1774 if M < evac_gen set failed_to_evac flag to indicate that we
1775 didn't manage to evacuate this object into evac_gen.
1780 evacuate() is the single most important function performance-wise
1781 in the GC. Various things have been tried to speed it up, but as
1782 far as I can tell the code generated by gcc 3.2 with -O2 is about
1783 as good as it's going to get. We pass the argument to evacuate()
1784 in a register using the 'regparm' attribute (see the prototype for
1785 evacuate() near the top of this file).
1787 Changing evacuate() to take an (StgClosure **) rather than
1788 returning the new pointer seems attractive, because we can avoid
1789 writing back the pointer when it hasn't changed (eg. for a static
1790 object, or an object in a generation > N). However, I tried it and
1791 it doesn't help. One reason is that the (StgClosure **) pointer
1792 gets spilled to the stack inside evacuate(), resulting in far more
1793 extra reads/writes than we save.
1794 -------------------------------------------------------------------------- */
1796 REGPARM1 static StgClosure *
1797 evacuate(StgClosure *q)
1804 const StgInfoTable *info;
1807 ASSERT(LOOKS_LIKE_CLOSURE_PTR(q));
1809 if (!HEAP_ALLOCED(q)) {
1811 if (!major_gc) return q;
1814 switch (info->type) {
1817 if (info->srt_bitmap != 0 &&
1818 *THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
1819 *THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
1820 static_objects = (StgClosure *)q;
1825 if (info->srt_bitmap != 0 &&
1826 *FUN_STATIC_LINK((StgClosure *)q) == NULL) {
1827 *FUN_STATIC_LINK((StgClosure *)q) = static_objects;
1828 static_objects = (StgClosure *)q;
1833 /* If q->saved_info != NULL, then it's a revertible CAF - it'll be
1834 * on the CAF list, so don't do anything with it here (we'll
1835 * scavenge it later).
1837 if (((StgIndStatic *)q)->saved_info == NULL
1838 && *IND_STATIC_LINK((StgClosure *)q) == NULL) {
1839 *IND_STATIC_LINK((StgClosure *)q) = static_objects;
1840 static_objects = (StgClosure *)q;
1845 if (*STATIC_LINK(info,(StgClosure *)q) == NULL) {
1846 *STATIC_LINK(info,(StgClosure *)q) = static_objects;
1847 static_objects = (StgClosure *)q;
1851 case CONSTR_INTLIKE:
1852 case CONSTR_CHARLIKE:
1853 case CONSTR_NOCAF_STATIC:
1854 /* no need to put these on the static linked list, they don't need
1860 barf("evacuate(static): strange closure type %d", (int)(info->type));
1866 if (bd->gen_no > N) {
1867 /* Can't evacuate this object, because it's in a generation
1868 * older than the ones we're collecting. Let's hope that it's
1869 * in evac_gen or older, or we will have to arrange to track
1870 * this pointer using the mutable list.
1872 if (bd->gen_no < evac_gen) {
1874 failed_to_evac = rtsTrue;
1875 TICK_GC_FAILED_PROMOTION();
1880 if ((bd->flags & (BF_LARGE | BF_COMPACTED | BF_EVACUATED)) != 0) {
1882 /* pointer into to-space: just return it. This normally
1883 * shouldn't happen, but alllowing it makes certain things
1884 * slightly easier (eg. the mutable list can contain the same
1885 * object twice, for example).
1887 if (bd->flags & BF_EVACUATED) {
1888 if (bd->gen_no < evac_gen) {
1889 failed_to_evac = rtsTrue;
1890 TICK_GC_FAILED_PROMOTION();
1895 /* evacuate large objects by re-linking them onto a different list.
1897 if (bd->flags & BF_LARGE) {
1899 if (info->type == TSO &&
1900 ((StgTSO *)q)->what_next == ThreadRelocated) {
1901 q = (StgClosure *)((StgTSO *)q)->link;
1904 evacuate_large((P_)q);
1908 /* If the object is in a step that we're compacting, then we
1909 * need to use an alternative evacuate procedure.
1911 if (bd->flags & BF_COMPACTED) {
1912 if (!is_marked((P_)q,bd)) {
1914 if (mark_stack_full()) {
1915 mark_stack_overflowed = rtsTrue;
1918 push_mark_stack((P_)q);
1928 switch (info->type) {
1932 return copy(q,sizeW_fromITBL(info),stp);
1936 StgWord w = (StgWord)q->payload[0];
1937 if (q->header.info == Czh_con_info &&
1938 // unsigned, so always true: (StgChar)w >= MIN_CHARLIKE &&
1939 (StgChar)w <= MAX_CHARLIKE) {
1940 return (StgClosure *)CHARLIKE_CLOSURE((StgChar)w);
1942 if (q->header.info == Izh_con_info &&
1943 (StgInt)w >= MIN_INTLIKE && (StgInt)w <= MAX_INTLIKE) {
1944 return (StgClosure *)INTLIKE_CLOSURE((StgInt)w);
1947 return copy_noscav(q,sizeofW(StgHeader)+1,stp);
1953 return copy(q,sizeofW(StgHeader)+1,stp);
1957 return copy(q,sizeofW(StgThunk)+1,stp);
1962 #ifdef NO_PROMOTE_THUNKS
1963 if (bd->gen_no == 0 &&
1964 bd->step->no != 0 &&
1965 bd->step->no == generations[bd->gen_no].n_steps-1) {
1969 return copy(q,sizeofW(StgThunk)+2,stp);
1976 return copy(q,sizeofW(StgHeader)+2,stp);
1979 return copy_noscav(q,sizeofW(StgHeader)+2,stp);
1982 return copy(q,thunk_sizeW_fromITBL(info),stp);
1987 case IND_OLDGEN_PERM:
1990 return copy(q,sizeW_fromITBL(info),stp);
1993 return copy(q,bco_sizeW((StgBCO *)q),stp);
1996 case SE_CAF_BLACKHOLE:
1999 return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),stp);
2001 case THUNK_SELECTOR:
2005 if (thunk_selector_depth > MAX_THUNK_SELECTOR_DEPTH) {
2006 return copy(q,THUNK_SELECTOR_sizeW(),stp);
2009 p = eval_thunk_selector(info->layout.selector_offset,
2013 return copy(q,THUNK_SELECTOR_sizeW(),stp);
2016 // q is still BLACKHOLE'd.
2017 thunk_selector_depth++;
2019 thunk_selector_depth--;
2021 // Update the THUNK_SELECTOR with an indirection to the
2022 // EVACUATED closure now at p. Why do this rather than
2023 // upd_evacuee(q,p)? Because we have an invariant that an
2024 // EVACUATED closure always points to an object in the
2025 // same or an older generation (required by the short-cut
2026 // test in the EVACUATED case, below).
2027 SET_INFO(q, &stg_IND_info);
2028 ((StgInd *)q)->indirectee = p;
2031 // We store the size of the just evacuated object in the
2032 // LDV word so that the profiler can guess the position of
2033 // the next object later.
2034 SET_EVACUAEE_FOR_LDV(q, THUNK_SELECTOR_sizeW());
2042 // follow chains of indirections, don't evacuate them
2043 q = ((StgInd*)q)->indirectee;
2055 case CATCH_STM_FRAME:
2056 case CATCH_RETRY_FRAME:
2057 case ATOMICALLY_FRAME:
2058 // shouldn't see these
2059 barf("evacuate: stack frame at %p\n", q);
2062 return copy(q,pap_sizeW((StgPAP*)q),stp);
2065 return copy(q,ap_sizeW((StgAP*)q),stp);
2068 return copy(q,ap_stack_sizeW((StgAP_STACK*)q),stp);
2071 /* Already evacuated, just return the forwarding address.
2072 * HOWEVER: if the requested destination generation (evac_gen) is
2073 * older than the actual generation (because the object was
2074 * already evacuated to a younger generation) then we have to
2075 * set the failed_to_evac flag to indicate that we couldn't
2076 * manage to promote the object to the desired generation.
2079 * Optimisation: the check is fairly expensive, but we can often
2080 * shortcut it if either the required generation is 0, or the
2081 * current object (the EVACUATED) is in a high enough generation.
2082 * We know that an EVACUATED always points to an object in the
2083 * same or an older generation. stp is the lowest step that the
2084 * current object would be evacuated to, so we only do the full
2085 * check if stp is too low.
2087 if (evac_gen > 0 && stp->gen_no < evac_gen) { // optimisation
2088 StgClosure *p = ((StgEvacuated*)q)->evacuee;
2089 if (HEAP_ALLOCED(p) && Bdescr((P_)p)->gen_no < evac_gen) {
2090 failed_to_evac = rtsTrue;
2091 TICK_GC_FAILED_PROMOTION();
2094 return ((StgEvacuated*)q)->evacuee;
2097 // just copy the block
2098 return copy_noscav(q,arr_words_sizeW((StgArrWords *)q),stp);
2101 case MUT_ARR_PTRS_FROZEN:
2102 case MUT_ARR_PTRS_FROZEN0:
2103 // just copy the block
2104 return copy(q,mut_arr_ptrs_sizeW((StgMutArrPtrs *)q),stp);
2108 StgTSO *tso = (StgTSO *)q;
2110 /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
2112 if (tso->what_next == ThreadRelocated) {
2113 q = (StgClosure *)tso->link;
2117 /* To evacuate a small TSO, we need to relocate the update frame
2124 new_tso = (StgTSO *)copyPart((StgClosure *)tso,
2126 sizeofW(StgTSO), stp);
2127 move_TSO(tso, new_tso);
2128 for (p = tso->sp, q = new_tso->sp;
2129 p < tso->stack+tso->stack_size;) {
2133 return (StgClosure *)new_tso;
2140 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
2141 to = copy(q,BLACKHOLE_sizeW(),stp);
2142 //ToDo: derive size etc from reverted IP
2143 //to = copy(q,size,stp);
2145 debugBelch("@@ evacuate: RBH %p (%s) to %p (%s)",
2146 q, info_type(q), to, info_type(to)));
2151 ASSERT(sizeofW(StgBlockedFetch) >= MIN_NONUPD_SIZE);
2152 to = copy(q,sizeofW(StgBlockedFetch),stp);
2154 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
2155 q, info_type(q), to, info_type(to)));
2162 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
2163 to = copy(q,sizeofW(StgFetchMe),stp);
2165 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
2166 q, info_type(q), to, info_type(to)));
2170 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
2171 to = copy(q,sizeofW(StgFetchMeBlockingQueue),stp);
2173 debugBelch("@@ evacuate: %p (%s) to %p (%s)",
2174 q, info_type(q), to, info_type(to)));
2179 return copy(q,sizeofW(StgTRecHeader),stp);
2181 case TVAR_WAIT_QUEUE:
2182 return copy(q,sizeofW(StgTVarWaitQueue),stp);
2185 return copy(q,sizeofW(StgTVar),stp);
2188 return copy(q,sizeofW(StgTRecChunk),stp);
2191 barf("evacuate: strange closure type %d", (int)(info->type));
2197 /* -----------------------------------------------------------------------------
2198 Evaluate a THUNK_SELECTOR if possible.
2200 returns: NULL if we couldn't evaluate this THUNK_SELECTOR, or
2201 a closure pointer if we evaluated it and this is the result. Note
2202 that "evaluating" the THUNK_SELECTOR doesn't necessarily mean
2203 reducing it to HNF, just that we have eliminated the selection.
2204 The result might be another thunk, or even another THUNK_SELECTOR.
2206 If the return value is non-NULL, the original selector thunk has
2207 been BLACKHOLE'd, and should be updated with an indirection or a
2208 forwarding pointer. If the return value is NULL, then the selector
2212 ToDo: the treatment of THUNK_SELECTORS could be improved in the
2213 following way (from a suggestion by Ian Lynagh):
2215 We can have a chain like this:
2219 |-----> sel_0 --> (a,b)
2221 |-----> sel_0 --> ...
2223 and the depth limit means we don't go all the way to the end of the
2224 chain, which results in a space leak. This affects the recursive
2225 call to evacuate() in the THUNK_SELECTOR case in evacuate(): *not*
2226 the recursive call to eval_thunk_selector() in
2227 eval_thunk_selector().
2229 We could eliminate the depth bound in this case, in the following
2232 - traverse the chain once to discover the *value* of the
2233 THUNK_SELECTOR. Mark all THUNK_SELECTORS that we
2234 visit on the way as having been visited already (somehow).
2236 - in a second pass, traverse the chain again updating all
2237 THUNK_SEELCTORS that we find on the way with indirections to
2240 - if we encounter a "marked" THUNK_SELECTOR in a normal
2241 evacuate(), we konw it can't be updated so just evac it.
2243 Program that illustrates the problem:
2246 foo (x:xs) = let (ys, zs) = foo xs
2247 in if x >= 0 then (x:ys, zs) else (ys, x:zs)
2249 main = bar [1..(100000000::Int)]
2250 bar xs = (\(ys, zs) -> print ys >> print zs) (foo xs)
2252 -------------------------------------------------------------------------- */
2254 static inline rtsBool
2255 is_to_space ( StgClosure *p )
2259 bd = Bdescr((StgPtr)p);
2260 if (HEAP_ALLOCED(p) &&
2261 ((bd->flags & BF_EVACUATED)
2262 || ((bd->flags & BF_COMPACTED) &&
2263 is_marked((P_)p,bd)))) {
2271 eval_thunk_selector( nat field, StgSelector * p )
2274 const StgInfoTable *info_ptr;
2275 StgClosure *selectee;
2277 selectee = p->selectee;
2279 // Save the real info pointer (NOTE: not the same as get_itbl()).
2280 info_ptr = p->header.info;
2282 // If the THUNK_SELECTOR is in a generation that we are not
2283 // collecting, then bail out early. We won't be able to save any
2284 // space in any case, and updating with an indirection is trickier
2286 if (Bdescr((StgPtr)p)->gen_no > N) {
2290 // BLACKHOLE the selector thunk, since it is now under evaluation.
2291 // This is important to stop us going into an infinite loop if
2292 // this selector thunk eventually refers to itself.
2293 SET_INFO(p,&stg_BLACKHOLE_info);
2297 // We don't want to end up in to-space, because this causes
2298 // problems when the GC later tries to evacuate the result of
2299 // eval_thunk_selector(). There are various ways this could
2302 // 1. following an IND_STATIC
2304 // 2. when the old generation is compacted, the mark phase updates
2305 // from-space pointers to be to-space pointers, and we can't
2306 // reliably tell which we're following (eg. from an IND_STATIC).
2308 // 3. compacting GC again: if we're looking at a constructor in
2309 // the compacted generation, it might point directly to objects
2310 // in to-space. We must bale out here, otherwise doing the selection
2311 // will result in a to-space pointer being returned.
2313 // (1) is dealt with using a BF_EVACUATED test on the
2314 // selectee. (2) and (3): we can tell if we're looking at an
2315 // object in the compacted generation that might point to
2316 // to-space objects by testing that (a) it is BF_COMPACTED, (b)
2317 // the compacted generation is being collected, and (c) the
2318 // object is marked. Only a marked object may have pointers that
2319 // point to to-space objects, because that happens when
2322 // The to-space test is now embodied in the in_to_space() inline
2323 // function, as it is re-used below.
2325 if (is_to_space(selectee)) {
2329 info = get_itbl(selectee);
2330 switch (info->type) {
2338 case CONSTR_NOCAF_STATIC:
2339 // check that the size is in range
2340 ASSERT(field < (StgWord32)(info->layout.payload.ptrs +
2341 info->layout.payload.nptrs));
2343 // Select the right field from the constructor, and check
2344 // that the result isn't in to-space. It might be in
2345 // to-space if, for example, this constructor contains
2346 // pointers to younger-gen objects (and is on the mut-once
2351 q = selectee->payload[field];
2352 if (is_to_space(q)) {
2362 case IND_OLDGEN_PERM:
2364 selectee = ((StgInd *)selectee)->indirectee;
2368 // We don't follow pointers into to-space; the constructor
2369 // has already been evacuated, so we won't save any space
2370 // leaks by evaluating this selector thunk anyhow.
2373 case THUNK_SELECTOR:
2377 // check that we don't recurse too much, re-using the
2378 // depth bound also used in evacuate().
2379 if (thunk_selector_depth >= MAX_THUNK_SELECTOR_DEPTH) {
2382 thunk_selector_depth++;
2384 val = eval_thunk_selector(info->layout.selector_offset,
2385 (StgSelector *)selectee);
2387 thunk_selector_depth--;
2392 // We evaluated this selector thunk, so update it with
2393 // an indirection. NOTE: we don't use UPD_IND here,
2394 // because we are guaranteed that p is in a generation
2395 // that we are collecting, and we never want to put the
2396 // indirection on a mutable list.
2398 // For the purposes of LDV profiling, we have destroyed
2399 // the original selector thunk.
2400 SET_INFO(p, info_ptr);
2401 LDV_RECORD_DEAD_FILL_SLOP_DYNAMIC(selectee);
2403 ((StgInd *)selectee)->indirectee = val;
2404 SET_INFO(selectee,&stg_IND_info);
2406 // For the purposes of LDV profiling, we have created an
2408 LDV_RECORD_CREATE(selectee);
2425 case SE_CAF_BLACKHOLE:
2437 // not evaluated yet
2441 barf("eval_thunk_selector: strange selectee %d",
2446 // We didn't manage to evaluate this thunk; restore the old info pointer
2447 SET_INFO(p, info_ptr);
2451 /* -----------------------------------------------------------------------------
2452 move_TSO is called to update the TSO structure after it has been
2453 moved from one place to another.
2454 -------------------------------------------------------------------------- */
2457 move_TSO (StgTSO *src, StgTSO *dest)
2461 // relocate the stack pointer...
2462 diff = (StgPtr)dest - (StgPtr)src; // In *words*
2463 dest->sp = (StgPtr)dest->sp + diff;
2466 /* Similar to scavenge_large_bitmap(), but we don't write back the
2467 * pointers we get back from evacuate().
2470 scavenge_large_srt_bitmap( StgLargeSRT *large_srt )
2477 bitmap = large_srt->l.bitmap[b];
2478 size = (nat)large_srt->l.size;
2479 p = (StgClosure **)large_srt->srt;
2480 for (i = 0; i < size; ) {
2481 if ((bitmap & 1) != 0) {
2486 if (i % BITS_IN(W_) == 0) {
2488 bitmap = large_srt->l.bitmap[b];
2490 bitmap = bitmap >> 1;
2495 /* evacuate the SRT. If srt_bitmap is zero, then there isn't an
2496 * srt field in the info table. That's ok, because we'll
2497 * never dereference it.
2500 scavenge_srt (StgClosure **srt, nat srt_bitmap)
2505 bitmap = srt_bitmap;
2508 if (bitmap == (StgHalfWord)(-1)) {
2509 scavenge_large_srt_bitmap( (StgLargeSRT *)srt );
2513 while (bitmap != 0) {
2514 if ((bitmap & 1) != 0) {
2515 #ifdef ENABLE_WIN32_DLL_SUPPORT
2516 // Special-case to handle references to closures hiding out in DLLs, since
2517 // double indirections required to get at those. The code generator knows
2518 // which is which when generating the SRT, so it stores the (indirect)
2519 // reference to the DLL closure in the table by first adding one to it.
2520 // We check for this here, and undo the addition before evacuating it.
2522 // If the SRT entry hasn't got bit 0 set, the SRT entry points to a
2523 // closure that's fixed at link-time, and no extra magic is required.
2524 if ( (unsigned long)(*srt) & 0x1 ) {
2525 evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
2534 bitmap = bitmap >> 1;
2540 scavenge_thunk_srt(const StgInfoTable *info)
2542 StgThunkInfoTable *thunk_info;
2544 if (!major_gc) return;
2546 thunk_info = itbl_to_thunk_itbl(info);
2547 scavenge_srt((StgClosure **)GET_SRT(thunk_info), thunk_info->i.srt_bitmap);
2551 scavenge_fun_srt(const StgInfoTable *info)
2553 StgFunInfoTable *fun_info;
2555 if (!major_gc) return;
2557 fun_info = itbl_to_fun_itbl(info);
2558 scavenge_srt((StgClosure **)GET_FUN_SRT(fun_info), fun_info->i.srt_bitmap);
2561 /* -----------------------------------------------------------------------------
2563 -------------------------------------------------------------------------- */
2566 scavengeTSO (StgTSO *tso)
2568 if ( tso->why_blocked == BlockedOnMVar
2569 || tso->why_blocked == BlockedOnBlackHole
2570 || tso->why_blocked == BlockedOnException
2572 || tso->why_blocked == BlockedOnGA
2573 || tso->why_blocked == BlockedOnGA_NoSend
2576 tso->block_info.closure = evacuate(tso->block_info.closure);
2578 if ( tso->blocked_exceptions != NULL ) {
2579 tso->blocked_exceptions =
2580 (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
2583 // We don't always chase the link field: TSOs on the blackhole
2584 // queue are not automatically alive, so the link field is a
2585 // "weak" pointer in that case.
2586 if (tso->why_blocked != BlockedOnBlackHole) {
2587 tso->link = (StgTSO *)evacuate((StgClosure *)tso->link);
2590 // scavange current transaction record
2591 tso->trec = (StgTRecHeader *)evacuate((StgClosure *)tso->trec);
2593 // scavenge this thread's stack
2594 scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
2597 /* -----------------------------------------------------------------------------
2598 Blocks of function args occur on the stack (at the top) and
2600 -------------------------------------------------------------------------- */
2602 STATIC_INLINE StgPtr
2603 scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
2610 switch (fun_info->f.fun_type) {
2612 bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
2613 size = BITMAP_SIZE(fun_info->f.b.bitmap);
2616 size = GET_FUN_LARGE_BITMAP(fun_info)->size;
2617 scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
2621 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2622 size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->f.fun_type]);
2625 if ((bitmap & 1) == 0) {
2626 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2629 bitmap = bitmap >> 1;
2637 STATIC_INLINE StgPtr
2638 scavenge_PAP_payload (StgClosure *fun, StgClosure **payload, StgWord size)
2642 StgFunInfoTable *fun_info;
2644 fun_info = get_fun_itbl(fun);
2645 ASSERT(fun_info->i.type != PAP);
2646 p = (StgPtr)payload;
2648 switch (fun_info->f.fun_type) {
2650 bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
2653 scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
2657 scavenge_large_bitmap((StgPtr)payload, BCO_BITMAP(fun), size);
2661 bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
2664 if ((bitmap & 1) == 0) {
2665 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2668 bitmap = bitmap >> 1;
2676 STATIC_INLINE StgPtr
2677 scavenge_PAP (StgPAP *pap)
2679 pap->fun = evacuate(pap->fun);
2680 return scavenge_PAP_payload (pap->fun, pap->payload, pap->n_args);
2683 STATIC_INLINE StgPtr
2684 scavenge_AP (StgAP *ap)
2686 ap->fun = evacuate(ap->fun);
2687 return scavenge_PAP_payload (ap->fun, ap->payload, ap->n_args);
2690 /* -----------------------------------------------------------------------------
2691 Scavenge a given step until there are no more objects in this step
2694 evac_gen is set by the caller to be either zero (for a step in a
2695 generation < N) or G where G is the generation of the step being
2698 We sometimes temporarily change evac_gen back to zero if we're
2699 scavenging a mutable object where early promotion isn't such a good
2701 -------------------------------------------------------------------------- */
2709 nat saved_evac_gen = evac_gen;
2714 failed_to_evac = rtsFalse;
2716 /* scavenge phase - standard breadth-first scavenging of the
2720 while (bd != stp->hp_bd || p < stp->hp) {
2722 // If we're at the end of this block, move on to the next block
2723 if (bd != stp->hp_bd && p == bd->free) {
2729 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
2730 info = get_itbl((StgClosure *)p);
2732 ASSERT(thunk_selector_depth == 0);
2735 switch (info->type) {
2739 StgMVar *mvar = ((StgMVar *)p);
2741 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
2742 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
2743 mvar->value = evacuate((StgClosure *)mvar->value);
2744 evac_gen = saved_evac_gen;
2745 failed_to_evac = rtsTrue; // mutable.
2746 p += sizeofW(StgMVar);
2751 scavenge_fun_srt(info);
2752 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2753 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2754 p += sizeofW(StgHeader) + 2;
2758 scavenge_thunk_srt(info);
2759 ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
2760 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2761 p += sizeofW(StgThunk) + 2;
2765 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
2766 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2767 p += sizeofW(StgHeader) + 2;
2771 scavenge_thunk_srt(info);
2772 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2773 p += sizeofW(StgThunk) + 1;
2777 scavenge_fun_srt(info);
2779 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2780 p += sizeofW(StgHeader) + 1;
2784 scavenge_thunk_srt(info);
2785 p += sizeofW(StgThunk) + 1;
2789 scavenge_fun_srt(info);
2791 p += sizeofW(StgHeader) + 1;
2795 scavenge_thunk_srt(info);
2796 p += sizeofW(StgThunk) + 2;
2800 scavenge_fun_srt(info);
2802 p += sizeofW(StgHeader) + 2;
2806 scavenge_thunk_srt(info);
2807 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
2808 p += sizeofW(StgThunk) + 2;
2812 scavenge_fun_srt(info);
2814 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
2815 p += sizeofW(StgHeader) + 2;
2819 scavenge_fun_srt(info);
2826 scavenge_thunk_srt(info);
2827 end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
2828 for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
2829 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2831 p += info->layout.payload.nptrs;
2842 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
2843 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
2844 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2846 p += info->layout.payload.nptrs;
2851 StgBCO *bco = (StgBCO *)p;
2852 bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
2853 bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
2854 bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
2855 bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
2856 p += bco_sizeW(bco);
2861 if (stp->gen->no != 0) {
2864 // No need to call LDV_recordDead_FILL_SLOP_DYNAMIC() because an
2865 // IND_OLDGEN_PERM closure is larger than an IND_PERM closure.
2866 LDV_recordDead((StgClosure *)p, sizeofW(StgInd));
2869 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
2871 SET_INFO(((StgClosure *)p), &stg_IND_OLDGEN_PERM_info);
2873 // We pretend that p has just been created.
2874 LDV_RECORD_CREATE((StgClosure *)p);
2877 case IND_OLDGEN_PERM:
2878 ((StgInd *)p)->indirectee = evacuate(((StgInd *)p)->indirectee);
2879 p += sizeofW(StgInd);
2884 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2885 evac_gen = saved_evac_gen;
2886 failed_to_evac = rtsTrue; // mutable anyhow
2887 p += sizeofW(StgMutVar);
2891 case SE_CAF_BLACKHOLE:
2894 p += BLACKHOLE_sizeW();
2897 case THUNK_SELECTOR:
2899 StgSelector *s = (StgSelector *)p;
2900 s->selectee = evacuate(s->selectee);
2901 p += THUNK_SELECTOR_sizeW();
2905 // A chunk of stack saved in a heap object
2908 StgAP_STACK *ap = (StgAP_STACK *)p;
2910 ap->fun = evacuate(ap->fun);
2911 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
2912 p = (StgPtr)ap->payload + ap->size;
2917 p = scavenge_PAP((StgPAP *)p);
2921 p = scavenge_AP((StgAP *)p);
2925 // nothing to follow
2926 p += arr_words_sizeW((StgArrWords *)p);
2930 // follow everything
2934 evac_gen = 0; // repeatedly mutable
2935 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2936 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2937 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2939 evac_gen = saved_evac_gen;
2940 failed_to_evac = rtsTrue; // mutable anyhow.
2944 case MUT_ARR_PTRS_FROZEN:
2945 case MUT_ARR_PTRS_FROZEN0:
2946 // follow everything
2950 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2951 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2952 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
2954 // it's tempting to recordMutable() if failed_to_evac is
2955 // false, but that breaks some assumptions (eg. every
2956 // closure on the mutable list is supposed to have the MUT
2957 // flag set, and MUT_ARR_PTRS_FROZEN doesn't).
2963 StgTSO *tso = (StgTSO *)p;
2966 evac_gen = saved_evac_gen;
2967 failed_to_evac = rtsTrue; // mutable anyhow.
2968 p += tso_sizeW(tso);
2976 nat size, ptrs, nonptrs, vhs;
2978 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2980 StgRBH *rbh = (StgRBH *)p;
2981 (StgClosure *)rbh->blocking_queue =
2982 evacuate((StgClosure *)rbh->blocking_queue);
2983 failed_to_evac = rtsTrue; // mutable anyhow.
2985 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2986 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2987 // ToDo: use size of reverted closure here!
2988 p += BLACKHOLE_sizeW();
2994 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2995 // follow the pointer to the node which is being demanded
2996 (StgClosure *)bf->node =
2997 evacuate((StgClosure *)bf->node);
2998 // follow the link to the rest of the blocking queue
2999 (StgClosure *)bf->link =
3000 evacuate((StgClosure *)bf->link);
3002 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3003 bf, info_type((StgClosure *)bf),
3004 bf->node, info_type(bf->node)));
3005 p += sizeofW(StgBlockedFetch);
3013 p += sizeofW(StgFetchMe);
3014 break; // nothing to do in this case
3018 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3019 (StgClosure *)fmbq->blocking_queue =
3020 evacuate((StgClosure *)fmbq->blocking_queue);
3022 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3023 p, info_type((StgClosure *)p)));
3024 p += sizeofW(StgFetchMeBlockingQueue);
3029 case TVAR_WAIT_QUEUE:
3031 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3033 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3034 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3035 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3036 evac_gen = saved_evac_gen;
3037 failed_to_evac = rtsTrue; // mutable
3038 p += sizeofW(StgTVarWaitQueue);
3044 StgTVar *tvar = ((StgTVar *) p);
3046 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3047 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3049 tvar->last_update_by = (StgTRecHeader *)evacuate((StgClosure*)tvar->last_update_by);
3051 evac_gen = saved_evac_gen;
3052 failed_to_evac = rtsTrue; // mutable
3053 p += sizeofW(StgTVar);
3059 StgTRecHeader *trec = ((StgTRecHeader *) p);
3061 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3062 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3063 evac_gen = saved_evac_gen;
3064 failed_to_evac = rtsTrue; // mutable
3065 p += sizeofW(StgTRecHeader);
3072 StgTRecChunk *tc = ((StgTRecChunk *) p);
3073 TRecEntry *e = &(tc -> entries[0]);
3075 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3076 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3077 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3078 e->expected_value = evacuate((StgClosure*)e->expected_value);
3079 e->new_value = evacuate((StgClosure*)e->new_value);
3081 evac_gen = saved_evac_gen;
3082 failed_to_evac = rtsTrue; // mutable
3083 p += sizeofW(StgTRecChunk);
3088 barf("scavenge: unimplemented/strange closure type %d @ %p",
3093 * We need to record the current object on the mutable list if
3094 * (a) It is actually mutable, or
3095 * (b) It contains pointers to a younger generation.
3096 * Case (b) arises if we didn't manage to promote everything that
3097 * the current object points to into the current generation.
3099 if (failed_to_evac) {
3100 failed_to_evac = rtsFalse;
3101 if (stp->gen_no > 0) {
3102 recordMutableGen((StgClosure *)q, stp->gen);
3111 /* -----------------------------------------------------------------------------
3112 Scavenge everything on the mark stack.
3114 This is slightly different from scavenge():
3115 - we don't walk linearly through the objects, so the scavenger
3116 doesn't need to advance the pointer on to the next object.
3117 -------------------------------------------------------------------------- */
3120 scavenge_mark_stack(void)
3126 evac_gen = oldest_gen->no;
3127 saved_evac_gen = evac_gen;
3130 while (!mark_stack_empty()) {
3131 p = pop_mark_stack();
3133 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3134 info = get_itbl((StgClosure *)p);
3137 switch (info->type) {
3141 StgMVar *mvar = ((StgMVar *)p);
3143 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
3144 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
3145 mvar->value = evacuate((StgClosure *)mvar->value);
3146 evac_gen = saved_evac_gen;
3147 failed_to_evac = rtsTrue; // mutable.
3152 scavenge_fun_srt(info);
3153 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
3154 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3158 scavenge_thunk_srt(info);
3159 ((StgThunk *)p)->payload[1] = evacuate(((StgThunk *)p)->payload[1]);
3160 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
3164 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
3165 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3170 scavenge_fun_srt(info);
3171 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3176 scavenge_thunk_srt(info);
3177 ((StgThunk *)p)->payload[0] = evacuate(((StgThunk *)p)->payload[0]);
3182 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
3187 scavenge_fun_srt(info);
3192 scavenge_thunk_srt(info);
3200 scavenge_fun_srt(info);
3207 scavenge_thunk_srt(info);
3208 end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
3209 for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
3210 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3222 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3223 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
3224 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3230 StgBCO *bco = (StgBCO *)p;
3231 bco->instrs = (StgArrWords *)evacuate((StgClosure *)bco->instrs);
3232 bco->literals = (StgArrWords *)evacuate((StgClosure *)bco->literals);
3233 bco->ptrs = (StgMutArrPtrs *)evacuate((StgClosure *)bco->ptrs);
3234 bco->itbls = (StgArrWords *)evacuate((StgClosure *)bco->itbls);
3239 // don't need to do anything here: the only possible case
3240 // is that we're in a 1-space compacting collector, with
3241 // no "old" generation.
3245 case IND_OLDGEN_PERM:
3246 ((StgInd *)p)->indirectee =
3247 evacuate(((StgInd *)p)->indirectee);
3252 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3253 evac_gen = saved_evac_gen;
3254 failed_to_evac = rtsTrue;
3258 case SE_CAF_BLACKHOLE:
3264 case THUNK_SELECTOR:
3266 StgSelector *s = (StgSelector *)p;
3267 s->selectee = evacuate(s->selectee);
3271 // A chunk of stack saved in a heap object
3274 StgAP_STACK *ap = (StgAP_STACK *)p;
3276 ap->fun = evacuate(ap->fun);
3277 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3282 scavenge_PAP((StgPAP *)p);
3286 scavenge_AP((StgAP *)p);
3290 // follow everything
3294 evac_gen = 0; // repeatedly mutable
3295 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3296 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3297 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3299 evac_gen = saved_evac_gen;
3300 failed_to_evac = rtsTrue; // mutable anyhow.
3304 case MUT_ARR_PTRS_FROZEN:
3305 case MUT_ARR_PTRS_FROZEN0:
3306 // follow everything
3310 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3311 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3312 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3319 StgTSO *tso = (StgTSO *)p;
3322 evac_gen = saved_evac_gen;
3323 failed_to_evac = rtsTrue;
3331 nat size, ptrs, nonptrs, vhs;
3333 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3335 StgRBH *rbh = (StgRBH *)p;
3336 bh->blocking_queue =
3337 (StgTSO *)evacuate((StgClosure *)bh->blocking_queue);
3338 failed_to_evac = rtsTrue; // mutable anyhow.
3340 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3341 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3347 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3348 // follow the pointer to the node which is being demanded
3349 (StgClosure *)bf->node =
3350 evacuate((StgClosure *)bf->node);
3351 // follow the link to the rest of the blocking queue
3352 (StgClosure *)bf->link =
3353 evacuate((StgClosure *)bf->link);
3355 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3356 bf, info_type((StgClosure *)bf),
3357 bf->node, info_type(bf->node)));
3365 break; // nothing to do in this case
3369 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3370 (StgClosure *)fmbq->blocking_queue =
3371 evacuate((StgClosure *)fmbq->blocking_queue);
3373 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3374 p, info_type((StgClosure *)p)));
3379 case TVAR_WAIT_QUEUE:
3381 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3383 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3384 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3385 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3386 evac_gen = saved_evac_gen;
3387 failed_to_evac = rtsTrue; // mutable
3393 StgTVar *tvar = ((StgTVar *) p);
3395 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3396 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3398 tvar->last_update_by = (StgTRecHeader *)evacuate((StgClosure*)tvar->last_update_by);
3400 evac_gen = saved_evac_gen;
3401 failed_to_evac = rtsTrue; // mutable
3408 StgTRecChunk *tc = ((StgTRecChunk *) p);
3409 TRecEntry *e = &(tc -> entries[0]);
3411 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3412 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3413 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3414 e->expected_value = evacuate((StgClosure*)e->expected_value);
3415 e->new_value = evacuate((StgClosure*)e->new_value);
3417 evac_gen = saved_evac_gen;
3418 failed_to_evac = rtsTrue; // mutable
3424 StgTRecHeader *trec = ((StgTRecHeader *) p);
3426 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3427 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3428 evac_gen = saved_evac_gen;
3429 failed_to_evac = rtsTrue; // mutable
3434 barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p",
3438 if (failed_to_evac) {
3439 failed_to_evac = rtsFalse;
3441 recordMutableGen((StgClosure *)q, &generations[evac_gen]);
3445 // mark the next bit to indicate "scavenged"
3446 mark(q+1, Bdescr(q));
3448 } // while (!mark_stack_empty())
3450 // start a new linear scan if the mark stack overflowed at some point
3451 if (mark_stack_overflowed && oldgen_scan_bd == NULL) {
3452 IF_DEBUG(gc, debugBelch("scavenge_mark_stack: starting linear scan"));
3453 mark_stack_overflowed = rtsFalse;
3454 oldgen_scan_bd = oldest_gen->steps[0].old_blocks;
3455 oldgen_scan = oldgen_scan_bd->start;
3458 if (oldgen_scan_bd) {
3459 // push a new thing on the mark stack
3461 // find a closure that is marked but not scavenged, and start
3463 while (oldgen_scan < oldgen_scan_bd->free
3464 && !is_marked(oldgen_scan,oldgen_scan_bd)) {
3468 if (oldgen_scan < oldgen_scan_bd->free) {
3470 // already scavenged?
3471 if (is_marked(oldgen_scan+1,oldgen_scan_bd)) {
3472 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3475 push_mark_stack(oldgen_scan);
3476 // ToDo: bump the linear scan by the actual size of the object
3477 oldgen_scan += sizeofW(StgHeader) + MIN_NONUPD_SIZE;
3481 oldgen_scan_bd = oldgen_scan_bd->link;
3482 if (oldgen_scan_bd != NULL) {
3483 oldgen_scan = oldgen_scan_bd->start;
3489 /* -----------------------------------------------------------------------------
3490 Scavenge one object.
3492 This is used for objects that are temporarily marked as mutable
3493 because they contain old-to-new generation pointers. Only certain
3494 objects can have this property.
3495 -------------------------------------------------------------------------- */
3498 scavenge_one(StgPtr p)
3500 const StgInfoTable *info;
3501 nat saved_evac_gen = evac_gen;
3504 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3505 info = get_itbl((StgClosure *)p);
3507 switch (info->type) {
3511 StgMVar *mvar = ((StgMVar *)p);
3513 mvar->head = (StgTSO *)evacuate((StgClosure *)mvar->head);
3514 mvar->tail = (StgTSO *)evacuate((StgClosure *)mvar->tail);
3515 mvar->value = evacuate((StgClosure *)mvar->value);
3516 evac_gen = saved_evac_gen;
3517 failed_to_evac = rtsTrue; // mutable.
3530 end = (StgPtr)((StgThunk *)p)->payload + info->layout.payload.ptrs;
3531 for (q = (StgPtr)((StgThunk *)p)->payload; q < end; q++) {
3532 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3538 case FUN_1_0: // hardly worth specialising these guys
3554 end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
3555 for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
3556 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3563 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
3564 evac_gen = saved_evac_gen;
3565 failed_to_evac = rtsTrue; // mutable anyhow
3569 case SE_CAF_BLACKHOLE:
3574 case THUNK_SELECTOR:
3576 StgSelector *s = (StgSelector *)p;
3577 s->selectee = evacuate(s->selectee);
3583 StgAP_STACK *ap = (StgAP_STACK *)p;
3585 ap->fun = evacuate(ap->fun);
3586 scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
3587 p = (StgPtr)ap->payload + ap->size;
3592 p = scavenge_PAP((StgPAP *)p);
3596 p = scavenge_AP((StgAP *)p);
3600 // nothing to follow
3605 // follow everything
3608 evac_gen = 0; // repeatedly mutable
3609 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3610 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3611 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3613 evac_gen = saved_evac_gen;
3614 failed_to_evac = rtsTrue;
3618 case MUT_ARR_PTRS_FROZEN:
3619 case MUT_ARR_PTRS_FROZEN0:
3621 // follow everything
3624 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
3625 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
3626 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3633 StgTSO *tso = (StgTSO *)p;
3635 evac_gen = 0; // repeatedly mutable
3637 evac_gen = saved_evac_gen;
3638 failed_to_evac = rtsTrue;
3646 nat size, ptrs, nonptrs, vhs;
3648 StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
3650 StgRBH *rbh = (StgRBH *)p;
3651 (StgClosure *)rbh->blocking_queue =
3652 evacuate((StgClosure *)rbh->blocking_queue);
3653 failed_to_evac = rtsTrue; // mutable anyhow.
3655 debugBelch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
3656 p, info_type(p), (StgClosure *)rbh->blocking_queue));
3657 // ToDo: use size of reverted closure here!
3663 StgBlockedFetch *bf = (StgBlockedFetch *)p;
3664 // follow the pointer to the node which is being demanded
3665 (StgClosure *)bf->node =
3666 evacuate((StgClosure *)bf->node);
3667 // follow the link to the rest of the blocking queue
3668 (StgClosure *)bf->link =
3669 evacuate((StgClosure *)bf->link);
3671 debugBelch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
3672 bf, info_type((StgClosure *)bf),
3673 bf->node, info_type(bf->node)));
3681 break; // nothing to do in this case
3685 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
3686 (StgClosure *)fmbq->blocking_queue =
3687 evacuate((StgClosure *)fmbq->blocking_queue);
3689 debugBelch("@@ scavenge: %p (%s) exciting, isn't it",
3690 p, info_type((StgClosure *)p)));
3695 case TVAR_WAIT_QUEUE:
3697 StgTVarWaitQueue *wq = ((StgTVarWaitQueue *) p);
3699 wq->waiting_tso = (StgTSO *)evacuate((StgClosure*)wq->waiting_tso);
3700 wq->next_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->next_queue_entry);
3701 wq->prev_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)wq->prev_queue_entry);
3702 evac_gen = saved_evac_gen;
3703 failed_to_evac = rtsTrue; // mutable
3709 StgTVar *tvar = ((StgTVar *) p);
3711 tvar->current_value = evacuate((StgClosure*)tvar->current_value);
3712 tvar->first_wait_queue_entry = (StgTVarWaitQueue *)evacuate((StgClosure*)tvar->first_wait_queue_entry);
3714 tvar->last_update_by = (StgTRecHeader *)evacuate((StgClosure*)tvar->last_update_by);
3716 evac_gen = saved_evac_gen;
3717 failed_to_evac = rtsTrue; // mutable
3723 StgTRecHeader *trec = ((StgTRecHeader *) p);
3725 trec->enclosing_trec = (StgTRecHeader *)evacuate((StgClosure*)trec->enclosing_trec);
3726 trec->current_chunk = (StgTRecChunk *)evacuate((StgClosure*)trec->current_chunk);
3727 evac_gen = saved_evac_gen;
3728 failed_to_evac = rtsTrue; // mutable
3735 StgTRecChunk *tc = ((StgTRecChunk *) p);
3736 TRecEntry *e = &(tc -> entries[0]);
3738 tc->prev_chunk = (StgTRecChunk *)evacuate((StgClosure*)tc->prev_chunk);
3739 for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
3740 e->tvar = (StgTVar *)evacuate((StgClosure*)e->tvar);
3741 e->expected_value = evacuate((StgClosure*)e->expected_value);
3742 e->new_value = evacuate((StgClosure*)e->new_value);
3744 evac_gen = saved_evac_gen;
3745 failed_to_evac = rtsTrue; // mutable
3750 case IND_OLDGEN_PERM:
3753 /* Careful here: a THUNK can be on the mutable list because
3754 * it contains pointers to young gen objects. If such a thunk
3755 * is updated, the IND_OLDGEN will be added to the mutable
3756 * list again, and we'll scavenge it twice. evacuate()
3757 * doesn't check whether the object has already been
3758 * evacuated, so we perform that check here.
3760 StgClosure *q = ((StgInd *)p)->indirectee;
3761 if (HEAP_ALLOCED(q) && Bdescr((StgPtr)q)->flags & BF_EVACUATED) {
3764 ((StgInd *)p)->indirectee = evacuate(q);
3767 #if 0 && defined(DEBUG)
3768 if (RtsFlags.DebugFlags.gc)
3769 /* Debugging code to print out the size of the thing we just
3773 StgPtr start = gen->steps[0].scan;
3774 bdescr *start_bd = gen->steps[0].scan_bd;
3776 scavenge(&gen->steps[0]);
3777 if (start_bd != gen->steps[0].scan_bd) {
3778 size += (P_)BLOCK_ROUND_UP(start) - start;
3779 start_bd = start_bd->link;
3780 while (start_bd != gen->steps[0].scan_bd) {
3781 size += BLOCK_SIZE_W;
3782 start_bd = start_bd->link;
3784 size += gen->steps[0].scan -
3785 (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
3787 size = gen->steps[0].scan - start;
3789 debugBelch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
3795 barf("scavenge_one: strange object %d", (int)(info->type));
3798 no_luck = failed_to_evac;
3799 failed_to_evac = rtsFalse;
3803 /* -----------------------------------------------------------------------------
3804 Scavenging mutable lists.
3806 We treat the mutable list of each generation > N (i.e. all the
3807 generations older than the one being collected) as roots. We also
3808 remove non-mutable objects from the mutable list at this point.
3809 -------------------------------------------------------------------------- */
3812 scavenge_mutable_list(generation *gen)
3817 bd = gen->saved_mut_list;
3820 for (; bd != NULL; bd = bd->link) {
3821 for (q = bd->start; q < bd->free; q++) {
3823 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3824 if (scavenge_one(p)) {
3825 /* didn't manage to promote everything, so put the
3826 * object back on the list.
3828 recordMutableGen((StgClosure *)p,gen);
3833 // free the old mut_list
3834 freeChain(gen->saved_mut_list);
3835 gen->saved_mut_list = NULL;
3840 scavenge_static(void)
3842 StgClosure* p = static_objects;
3843 const StgInfoTable *info;
3845 /* Always evacuate straight to the oldest generation for static
3847 evac_gen = oldest_gen->no;
3849 /* keep going until we've scavenged all the objects on the linked
3851 while (p != END_OF_STATIC_LIST) {
3853 ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
3856 if (info->type==RBH)
3857 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
3859 // make sure the info pointer is into text space
3861 /* Take this object *off* the static_objects list,
3862 * and put it on the scavenged_static_objects list.
3864 static_objects = *STATIC_LINK(info,p);
3865 *STATIC_LINK(info,p) = scavenged_static_objects;
3866 scavenged_static_objects = p;
3868 switch (info -> type) {
3872 StgInd *ind = (StgInd *)p;
3873 ind->indirectee = evacuate(ind->indirectee);
3875 /* might fail to evacuate it, in which case we have to pop it
3876 * back on the mutable list of the oldest generation. We
3877 * leave it *on* the scavenged_static_objects list, though,
3878 * in case we visit this object again.
3880 if (failed_to_evac) {
3881 failed_to_evac = rtsFalse;
3882 recordMutableGen((StgClosure *)p,oldest_gen);
3888 scavenge_thunk_srt(info);
3892 scavenge_fun_srt(info);
3899 next = (P_)p->payload + info->layout.payload.ptrs;
3900 // evacuate the pointers
3901 for (q = (P_)p->payload; q < next; q++) {
3902 *q = (StgWord)(StgPtr)evacuate((StgClosure *)*q);
3908 barf("scavenge_static: strange closure %d", (int)(info->type));
3911 ASSERT(failed_to_evac == rtsFalse);
3913 /* get the next static object from the list. Remember, there might
3914 * be more stuff on this list now that we've done some evacuating!
3915 * (static_objects is a global)
3921 /* -----------------------------------------------------------------------------
3922 scavenge a chunk of memory described by a bitmap
3923 -------------------------------------------------------------------------- */
3926 scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
3932 bitmap = large_bitmap->bitmap[b];
3933 for (i = 0; i < size; ) {
3934 if ((bitmap & 1) == 0) {
3935 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3939 if (i % BITS_IN(W_) == 0) {
3941 bitmap = large_bitmap->bitmap[b];
3943 bitmap = bitmap >> 1;
3948 STATIC_INLINE StgPtr
3949 scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap)
3952 if ((bitmap & 1) == 0) {
3953 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
3956 bitmap = bitmap >> 1;
3962 /* -----------------------------------------------------------------------------
3963 scavenge_stack walks over a section of stack and evacuates all the
3964 objects pointed to by it. We can use the same code for walking
3965 AP_STACK_UPDs, since these are just sections of copied stack.
3966 -------------------------------------------------------------------------- */
3970 scavenge_stack(StgPtr p, StgPtr stack_end)
3972 const StgRetInfoTable* info;
3976 //IF_DEBUG(sanity, debugBelch(" scavenging stack between %p and %p", p, stack_end));
3979 * Each time around this loop, we are looking at a chunk of stack
3980 * that starts with an activation record.
3983 while (p < stack_end) {
3984 info = get_ret_itbl((StgClosure *)p);
3986 switch (info->i.type) {
3989 ((StgUpdateFrame *)p)->updatee
3990 = evacuate(((StgUpdateFrame *)p)->updatee);
3991 p += sizeofW(StgUpdateFrame);
3994 // small bitmap (< 32 entries, or 64 on a 64-bit machine)
3995 case CATCH_STM_FRAME:
3996 case CATCH_RETRY_FRAME:
3997 case ATOMICALLY_FRAME:
4002 bitmap = BITMAP_BITS(info->i.layout.bitmap);
4003 size = BITMAP_SIZE(info->i.layout.bitmap);
4004 // NOTE: the payload starts immediately after the info-ptr, we
4005 // don't have an StgHeader in the same sense as a heap closure.
4007 p = scavenge_small_bitmap(p, size, bitmap);
4011 scavenge_srt((StgClosure **)GET_SRT(info), info->i.srt_bitmap);
4019 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
4022 size = BCO_BITMAP_SIZE(bco);
4023 scavenge_large_bitmap(p, BCO_BITMAP(bco), size);
4028 // large bitmap (> 32 entries, or > 64 on a 64-bit machine)
4034 size = GET_LARGE_BITMAP(&info->i)->size;
4036 scavenge_large_bitmap(p, GET_LARGE_BITMAP(&info->i), size);
4038 // and don't forget to follow the SRT
4042 // Dynamic bitmap: the mask is stored on the stack, and
4043 // there are a number of non-pointers followed by a number
4044 // of pointers above the bitmapped area. (see StgMacros.h,
4049 dyn = ((StgRetDyn *)p)->liveness;
4051 // traverse the bitmap first
4052 bitmap = RET_DYN_LIVENESS(dyn);
4053 p = (P_)&((StgRetDyn *)p)->payload[0];
4054 size = RET_DYN_BITMAP_SIZE;
4055 p = scavenge_small_bitmap(p, size, bitmap);
4057 // skip over the non-ptr words
4058 p += RET_DYN_NONPTRS(dyn) + RET_DYN_NONPTR_REGS_SIZE;
4060 // follow the ptr words
4061 for (size = RET_DYN_PTRS(dyn); size > 0; size--) {
4062 *p = (StgWord)(StgPtr)evacuate((StgClosure *)*p);
4070 StgRetFun *ret_fun = (StgRetFun *)p;
4071 StgFunInfoTable *fun_info;
4073 ret_fun->fun = evacuate(ret_fun->fun);
4074 fun_info = get_fun_itbl(ret_fun->fun);
4075 p = scavenge_arg_block(fun_info, ret_fun->payload);
4080 barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->i.type));
4085 /*-----------------------------------------------------------------------------
4086 scavenge the large object list.
4088 evac_gen set by caller; similar games played with evac_gen as with
4089 scavenge() - see comment at the top of scavenge(). Most large
4090 objects are (repeatedly) mutable, so most of the time evac_gen will
4092 --------------------------------------------------------------------------- */
4095 scavenge_large(step *stp)
4100 bd = stp->new_large_objects;
4102 for (; bd != NULL; bd = stp->new_large_objects) {
4104 /* take this object *off* the large objects list and put it on
4105 * the scavenged large objects list. This is so that we can
4106 * treat new_large_objects as a stack and push new objects on
4107 * the front when evacuating.
4109 stp->new_large_objects = bd->link;
4110 dbl_link_onto(bd, &stp->scavenged_large_objects);
4112 // update the block count in this step.
4113 stp->n_scavenged_large_blocks += bd->blocks;
4116 if (scavenge_one(p)) {
4117 if (stp->gen_no > 0) {
4118 recordMutableGen((StgClosure *)p, stp->gen);
4124 /* -----------------------------------------------------------------------------
4125 Initialising the static object & mutable lists
4126 -------------------------------------------------------------------------- */
4129 zero_static_object_list(StgClosure* first_static)
4133 const StgInfoTable *info;
4135 for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
4137 link = *STATIC_LINK(info, p);
4138 *STATIC_LINK(info,p) = NULL;
4142 /* -----------------------------------------------------------------------------
4144 -------------------------------------------------------------------------- */
4151 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
4152 c = (StgIndStatic *)c->static_link)
4154 SET_INFO(c, c->saved_info);
4155 c->saved_info = NULL;
4156 // could, but not necessary: c->static_link = NULL;
4158 revertible_caf_list = NULL;
4162 markCAFs( evac_fn evac )
4166 for (c = (StgIndStatic *)caf_list; c != NULL;
4167 c = (StgIndStatic *)c->static_link)
4169 evac(&c->indirectee);
4171 for (c = (StgIndStatic *)revertible_caf_list; c != NULL;
4172 c = (StgIndStatic *)c->static_link)
4174 evac(&c->indirectee);
4178 /* -----------------------------------------------------------------------------
4179 Sanity code for CAF garbage collection.
4181 With DEBUG turned on, we manage a CAF list in addition to the SRT
4182 mechanism. After GC, we run down the CAF list and blackhole any
4183 CAFs which have been garbage collected. This means we get an error
4184 whenever the program tries to enter a garbage collected CAF.
4186 Any garbage collected CAFs are taken off the CAF list at the same
4188 -------------------------------------------------------------------------- */
4190 #if 0 && defined(DEBUG)
4197 const StgInfoTable *info;
4208 ASSERT(info->type == IND_STATIC);
4210 if (STATIC_LINK(info,p) == NULL) {
4211 IF_DEBUG(gccafs, debugBelch("CAF gc'd at 0x%04lx", (long)p));
4213 SET_INFO(p,&stg_BLACKHOLE_info);
4214 p = STATIC_LINK2(info,p);
4218 pp = &STATIC_LINK2(info,p);
4225 // debugBelch("%d CAFs live", i);
4230 /* -----------------------------------------------------------------------------
4233 Whenever a thread returns to the scheduler after possibly doing
4234 some work, we have to run down the stack and black-hole all the
4235 closures referred to by update frames.
4236 -------------------------------------------------------------------------- */
4239 threadLazyBlackHole(StgTSO *tso)
4242 StgRetInfoTable *info;
4246 stack_end = &tso->stack[tso->stack_size];
4248 frame = (StgClosure *)tso->sp;
4251 info = get_ret_itbl(frame);
4253 switch (info->i.type) {
4256 bh = ((StgUpdateFrame *)frame)->updatee;
4258 /* if the thunk is already blackholed, it means we've also
4259 * already blackholed the rest of the thunks on this stack,
4260 * so we can stop early.
4262 * The blackhole made for a CAF is a CAF_BLACKHOLE, so they
4263 * don't interfere with this optimisation.
4265 if (bh->header.info == &stg_BLACKHOLE_info) {
4269 if (bh->header.info != &stg_CAF_BLACKHOLE_info) {
4270 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4271 debugBelch("Unexpected lazy BHing required at 0x%04lx\n",(long)bh);
4275 // We pretend that bh is now dead.
4276 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4278 SET_INFO(bh,&stg_BLACKHOLE_info);
4280 // We pretend that bh has just been created.
4281 LDV_RECORD_CREATE(bh);
4284 frame = (StgClosure *) ((StgUpdateFrame *)frame + 1);
4290 // normal stack frames; do nothing except advance the pointer
4292 frame = (StgClosure *)((StgPtr)frame + stack_frame_sizeW(frame));
4298 /* -----------------------------------------------------------------------------
4301 * Code largely pinched from old RTS, then hacked to bits. We also do
4302 * lazy black holing here.
4304 * -------------------------------------------------------------------------- */
4306 struct stack_gap { StgWord gap_size; struct stack_gap *next_gap; };
4309 threadSqueezeStack(StgTSO *tso)
4312 rtsBool prev_was_update_frame;
4313 StgClosure *updatee = NULL;
4315 StgRetInfoTable *info;
4316 StgWord current_gap_size;
4317 struct stack_gap *gap;
4320 // Traverse the stack upwards, replacing adjacent update frames
4321 // with a single update frame and a "stack gap". A stack gap
4322 // contains two values: the size of the gap, and the distance
4323 // to the next gap (or the stack top).
4325 bottom = &(tso->stack[tso->stack_size]);
4329 ASSERT(frame < bottom);
4331 prev_was_update_frame = rtsFalse;
4332 current_gap_size = 0;
4333 gap = (struct stack_gap *) (tso->sp - sizeofW(StgUpdateFrame));
4335 while (frame < bottom) {
4337 info = get_ret_itbl((StgClosure *)frame);
4338 switch (info->i.type) {
4342 StgUpdateFrame *upd = (StgUpdateFrame *)frame;
4344 if (upd->updatee->header.info == &stg_BLACKHOLE_info) {
4346 // found a BLACKHOLE'd update frame; we've been here
4347 // before, in a previous GC, so just break out.
4349 // Mark the end of the gap, if we're in one.
4350 if (current_gap_size != 0) {
4351 gap = (struct stack_gap *)(frame-sizeofW(StgUpdateFrame));
4354 frame += sizeofW(StgUpdateFrame);
4355 goto done_traversing;
4358 if (prev_was_update_frame) {
4360 TICK_UPD_SQUEEZED();
4361 /* wasn't there something about update squeezing and ticky to be
4362 * sorted out? oh yes: we aren't counting each enter properly
4363 * in this case. See the log somewhere. KSW 1999-04-21
4365 * Check two things: that the two update frames don't point to
4366 * the same object, and that the updatee_bypass isn't already an
4367 * indirection. Both of these cases only happen when we're in a
4368 * block hole-style loop (and there are multiple update frames
4369 * on the stack pointing to the same closure), but they can both
4370 * screw us up if we don't check.
4372 if (upd->updatee != updatee && !closure_IND(upd->updatee)) {
4373 UPD_IND_NOLOCK(upd->updatee, updatee);
4376 // now mark this update frame as a stack gap. The gap
4377 // marker resides in the bottom-most update frame of
4378 // the series of adjacent frames, and covers all the
4379 // frames in this series.
4380 current_gap_size += sizeofW(StgUpdateFrame);
4381 ((struct stack_gap *)frame)->gap_size = current_gap_size;
4382 ((struct stack_gap *)frame)->next_gap = gap;
4384 frame += sizeofW(StgUpdateFrame);
4388 // single update frame, or the topmost update frame in a series
4390 StgClosure *bh = upd->updatee;
4392 // Do lazy black-holing
4393 if (bh->header.info != &stg_BLACKHOLE_info &&
4394 bh->header.info != &stg_CAF_BLACKHOLE_info) {
4395 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
4396 debugBelch("Unexpected lazy BHing required at 0x%04lx",(long)bh);
4399 // zero out the slop so that the sanity checker can tell
4400 // where the next closure is.
4401 DEBUG_FILL_SLOP(bh);
4404 // We pretend that bh is now dead.
4405 // ToDo: is the slop filling the same as DEBUG_FILL_SLOP?
4406 LDV_recordDead_FILL_SLOP_DYNAMIC((StgClosure *)bh);
4408 // Todo: maybe use SET_HDR() and remove LDV_RECORD_CREATE()?
4409 SET_INFO(bh,&stg_BLACKHOLE_info);
4411 // We pretend that bh has just been created.
4412 LDV_RECORD_CREATE(bh);
4415 prev_was_update_frame = rtsTrue;
4416 updatee = upd->updatee;
4417 frame += sizeofW(StgUpdateFrame);
4423 prev_was_update_frame = rtsFalse;
4425 // we're not in a gap... check whether this is the end of a gap
4426 // (an update frame can't be the end of a gap).
4427 if (current_gap_size != 0) {
4428 gap = (struct stack_gap *) (frame - sizeofW(StgUpdateFrame));
4430 current_gap_size = 0;
4432 frame += stack_frame_sizeW((StgClosure *)frame);
4439 // Now we have a stack with gaps in it, and we have to walk down
4440 // shoving the stack up to fill in the gaps. A diagram might
4444 // | ********* | <- sp
4448 // | stack_gap | <- gap | chunk_size
4450 // | ......... | <- gap_end v
4456 // 'sp' points the the current top-of-stack
4457 // 'gap' points to the stack_gap structure inside the gap
4458 // ***** indicates real stack data
4459 // ..... indicates gap
4460 // <empty> indicates unused
4464 void *gap_start, *next_gap_start, *gap_end;
4467 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4468 sp = next_gap_start;
4470 while ((StgPtr)gap > tso->sp) {
4472 // we're working in *bytes* now...
4473 gap_start = next_gap_start;
4474 gap_end = (void*) ((unsigned char*)gap_start - gap->gap_size * sizeof(W_));
4476 gap = gap->next_gap;
4477 next_gap_start = (void *)((unsigned char*)gap + sizeof(StgUpdateFrame));
4479 chunk_size = (unsigned char*)gap_end - (unsigned char*)next_gap_start;
4481 memmove(sp, next_gap_start, chunk_size);
4484 tso->sp = (StgPtr)sp;
4488 /* -----------------------------------------------------------------------------
4491 * We have to prepare for GC - this means doing lazy black holing
4492 * here. We also take the opportunity to do stack squeezing if it's
4494 * -------------------------------------------------------------------------- */
4496 threadPaused(StgTSO *tso)
4498 if ( RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue )
4499 threadSqueezeStack(tso); // does black holing too
4501 threadLazyBlackHole(tso);
4504 /* -----------------------------------------------------------------------------
4506 * -------------------------------------------------------------------------- */
4510 printMutableList(generation *gen)
4515 debugBelch("@@ Mutable list %p: ", gen->mut_list);
4517 for (bd = gen->mut_list; bd != NULL; bd = bd->link) {
4518 for (p = bd->start; p < bd->free; p++) {
4519 debugBelch("%p (%s), ", (void *)*p, info_type((StgClosure *)*p));