1 /* -----------------------------------------------------------------------------
2 * $Id: GC.c,v 1.76 2000/03/30 16:07:53 simonmar Exp $
4 * (c) The GHC Team 1998-1999
6 * Generational garbage collector
8 * ---------------------------------------------------------------------------*/
12 //* STATIC OBJECT LIST::
13 //* Static function declarations::
19 //* Sanity code for CAF garbage collection::
20 //* Lazy black holing::
22 //* Pausing a thread::
26 //@node Includes, STATIC OBJECT LIST
27 //@subsection Includes
33 #include "StoragePriv.h"
36 #include "SchedAPI.h" /* for ReverCAFs prototype */
39 #include "BlockAlloc.h"
44 #include "StablePriv.h"
46 #if defined(GRAN) || defined(PAR)
47 # include "GranSimRts.h"
48 # include "ParallelRts.h"
52 # include "ParallelDebug.h"
58 //@node STATIC OBJECT LIST, Static function declarations, Includes
59 //@subsection STATIC OBJECT LIST
61 /* STATIC OBJECT LIST.
64 * We maintain a linked list of static objects that are still live.
65 * The requirements for this list are:
67 * - we need to scan the list while adding to it, in order to
68 * scavenge all the static objects (in the same way that
69 * breadth-first scavenging works for dynamic objects).
71 * - we need to be able to tell whether an object is already on
72 * the list, to break loops.
74 * Each static object has a "static link field", which we use for
75 * linking objects on to the list. We use a stack-type list, consing
76 * objects on the front as they are added (this means that the
77 * scavenge phase is depth-first, not breadth-first, but that
80 * A separate list is kept for objects that have been scavenged
81 * already - this is so that we can zero all the marks afterwards.
83 * An object is on the list if its static link field is non-zero; this
84 * means that we have to mark the end of the list with '1', not NULL.
86 * Extra notes for generational GC:
88 * Each generation has a static object list associated with it. When
89 * collecting generations up to N, we treat the static object lists
90 * from generations > N as roots.
92 * We build up a static object list while collecting generations 0..N,
93 * which is then appended to the static object list of generation N+1.
95 StgClosure* static_objects; /* live static objects */
96 StgClosure* scavenged_static_objects; /* static objects scavenged so far */
98 /* N is the oldest generation being collected, where the generations
99 * are numbered starting at 0. A major GC (indicated by the major_gc
100 * flag) is when we're collecting all generations. We only attempt to
101 * deal with static objects and GC CAFs when doing a major GC.
104 static rtsBool major_gc;
106 /* Youngest generation that objects should be evacuated to in
107 * evacuate(). (Logically an argument to evacuate, but it's static
108 * a lot of the time so we optimise it into a global variable).
114 static StgWeak *old_weak_ptr_list; /* also pending finaliser list */
115 static rtsBool weak_done; /* all done for this pass */
117 /* List of all threads during GC
119 static StgTSO *old_all_threads;
120 static StgTSO *resurrected_threads;
122 /* Flag indicating failure to evacuate an object to the desired
125 static rtsBool failed_to_evac;
127 /* Old to-space (used for two-space collector only)
129 bdescr *old_to_space;
132 /* Data used for allocation area sizing.
134 lnat new_blocks; /* blocks allocated during this GC */
135 lnat g0s0_pcnt_kept = 30; /* percentage of g0s0 live at last minor GC */
137 //@node Static function declarations, Garbage Collect, STATIC OBJECT LIST
138 //@subsection Static function declarations
140 /* -----------------------------------------------------------------------------
141 Static function declarations
142 -------------------------------------------------------------------------- */
144 static StgClosure * evacuate ( StgClosure *q );
145 static void zero_static_object_list ( StgClosure* first_static );
146 static void zero_mutable_list ( StgMutClosure *first );
147 static void revert_dead_CAFs ( void );
149 static rtsBool traverse_weak_ptr_list ( void );
150 static void cleanup_weak_ptr_list ( StgWeak **list );
152 static void scavenge_stack ( StgPtr p, StgPtr stack_end );
153 static void scavenge_large ( step *step );
154 static void scavenge ( step *step );
155 static void scavenge_static ( void );
156 static void scavenge_mutable_list ( generation *g );
157 static void scavenge_mut_once_list ( generation *g );
160 static void gcCAFs ( void );
163 //@node Garbage Collect, Weak Pointers, Static function declarations
164 //@subsection Garbage Collect
166 /* -----------------------------------------------------------------------------
169 For garbage collecting generation N (and all younger generations):
171 - follow all pointers in the root set. the root set includes all
172 mutable objects in all steps in all generations.
174 - for each pointer, evacuate the object it points to into either
175 + to-space in the next higher step in that generation, if one exists,
176 + if the object's generation == N, then evacuate it to the next
177 generation if one exists, or else to-space in the current
179 + if the object's generation < N, then evacuate it to to-space
180 in the next generation.
182 - repeatedly scavenge to-space from each step in each generation
183 being collected until no more objects can be evacuated.
185 - free from-space in each step, and set from-space = to-space.
187 -------------------------------------------------------------------------- */
188 //@cindex GarbageCollect
190 void GarbageCollect(void (*get_roots)(void))
194 lnat live, allocated, collected = 0, copied = 0;
198 CostCentreStack *prev_CCS;
201 #if defined(DEBUG) && defined(GRAN)
202 IF_DEBUG(gc, belch("@@ Starting garbage collection at %ld (%lx)\n",
206 /* tell the stats department that we've started a GC */
209 /* attribute any costs to CCS_GC */
215 /* Approximate how much we allocated */
216 allocated = calcAllocated();
218 /* Figure out which generation to collect
221 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
222 if (generations[g].steps[0].n_blocks >= generations[g].max_blocks) {
226 major_gc = (N == RtsFlags.GcFlags.generations-1);
228 /* check stack sanity *before* GC (ToDo: check all threads) */
230 // ToDo!: check sanity IF_DEBUG(sanity, checkTSOsSanity());
232 IF_DEBUG(sanity, checkFreeListSanity());
234 /* Initialise the static object lists
236 static_objects = END_OF_STATIC_LIST;
237 scavenged_static_objects = END_OF_STATIC_LIST;
239 /* zero the mutable list for the oldest generation (see comment by
240 * zero_mutable_list below).
243 zero_mutable_list(generations[RtsFlags.GcFlags.generations-1].mut_once_list);
246 /* Save the old to-space if we're doing a two-space collection
248 if (RtsFlags.GcFlags.generations == 1) {
249 old_to_space = g0s0->to_space;
250 g0s0->to_space = NULL;
253 /* Keep a count of how many new blocks we allocated during this GC
254 * (used for resizing the allocation area, later).
258 /* Initialise to-space in all the generations/steps that we're
261 for (g = 0; g <= N; g++) {
262 generations[g].mut_once_list = END_MUT_LIST;
263 generations[g].mut_list = END_MUT_LIST;
265 for (s = 0; s < generations[g].n_steps; s++) {
267 /* generation 0, step 0 doesn't need to-space */
268 if (g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1) {
272 /* Get a free block for to-space. Extra blocks will be chained on
276 step = &generations[g].steps[s];
277 ASSERT(step->gen->no == g);
278 ASSERT(step->hp ? Bdescr(step->hp)->step == step : rtsTrue);
279 bd->gen = &generations[g];
282 bd->evacuated = 1; /* it's a to-space block */
283 step->hp = bd->start;
284 step->hpLim = step->hp + BLOCK_SIZE_W;
288 step->scan = bd->start;
290 step->new_large_objects = NULL;
291 step->scavenged_large_objects = NULL;
293 /* mark the large objects as not evacuated yet */
294 for (bd = step->large_objects; bd; bd = bd->link) {
300 /* make sure the older generations have at least one block to
301 * allocate into (this makes things easier for copy(), see below.
303 for (g = N+1; g < RtsFlags.GcFlags.generations; g++) {
304 for (s = 0; s < generations[g].n_steps; s++) {
305 step = &generations[g].steps[s];
306 if (step->hp_bd == NULL) {
308 bd->gen = &generations[g];
311 bd->evacuated = 0; /* *not* a to-space block */
312 step->hp = bd->start;
313 step->hpLim = step->hp + BLOCK_SIZE_W;
319 /* Set the scan pointer for older generations: remember we
320 * still have to scavenge objects that have been promoted. */
321 step->scan = step->hp;
322 step->scan_bd = step->hp_bd;
323 step->to_space = NULL;
325 step->new_large_objects = NULL;
326 step->scavenged_large_objects = NULL;
330 /* -----------------------------------------------------------------------
331 * follow all the roots that we know about:
332 * - mutable lists from each generation > N
333 * we want to *scavenge* these roots, not evacuate them: they're not
334 * going to move in this GC.
335 * Also: do them in reverse generation order. This is because we
336 * often want to promote objects that are pointed to by older
337 * generations early, so we don't have to repeatedly copy them.
338 * Doing the generations in reverse order ensures that we don't end
339 * up in the situation where we want to evac an object to gen 3 and
340 * it has already been evaced to gen 2.
344 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
345 generations[g].saved_mut_list = generations[g].mut_list;
346 generations[g].mut_list = END_MUT_LIST;
349 /* Do the mut-once lists first */
350 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
351 IF_PAR_DEBUG(verbose,
352 printMutOnceList(&generations[g]));
353 scavenge_mut_once_list(&generations[g]);
355 for (st = generations[g].n_steps-1; st >= 0; st--) {
356 scavenge(&generations[g].steps[st]);
360 for (g = RtsFlags.GcFlags.generations-1; g > N; g--) {
361 IF_PAR_DEBUG(verbose,
362 printMutableList(&generations[g]));
363 scavenge_mutable_list(&generations[g]);
365 for (st = generations[g].n_steps-1; st >= 0; st--) {
366 scavenge(&generations[g].steps[st]);
371 /* follow all the roots that the application knows about.
377 /* And don't forget to mark the TSO if we got here direct from
379 /* Not needed in a seq version?
381 CurrentTSO = (StgTSO *)MarkRoot((StgClosure *)CurrentTSO);
385 /* Mark the entries in the GALA table of the parallel system */
386 markLocalGAs(major_gc);
389 /* Mark the weak pointer list, and prepare to detect dead weak
392 old_weak_ptr_list = weak_ptr_list;
393 weak_ptr_list = NULL;
394 weak_done = rtsFalse;
396 /* The all_threads list is like the weak_ptr_list.
397 * See traverse_weak_ptr_list() for the details.
399 old_all_threads = all_threads;
400 all_threads = END_TSO_QUEUE;
401 resurrected_threads = END_TSO_QUEUE;
403 /* Mark the stable pointer table.
405 markStablePtrTable(major_gc);
409 /* ToDo: To fix the caf leak, we need to make the commented out
410 * parts of this code do something sensible - as described in
413 extern void markHugsObjects(void);
418 /* -------------------------------------------------------------------------
419 * Repeatedly scavenge all the areas we know about until there's no
420 * more scavenging to be done.
427 /* scavenge static objects */
428 if (major_gc && static_objects != END_OF_STATIC_LIST) {
432 /* When scavenging the older generations: Objects may have been
433 * evacuated from generations <= N into older generations, and we
434 * need to scavenge these objects. We're going to try to ensure that
435 * any evacuations that occur move the objects into at least the
436 * same generation as the object being scavenged, otherwise we
437 * have to create new entries on the mutable list for the older
441 /* scavenge each step in generations 0..maxgen */
445 for (gen = RtsFlags.GcFlags.generations-1; gen >= 0; gen--) {
446 for (st = generations[gen].n_steps-1; st >= 0 ; st--) {
447 if (gen == 0 && st == 0 && RtsFlags.GcFlags.generations > 1) {
450 step = &generations[gen].steps[st];
452 if (step->hp_bd != step->scan_bd || step->scan < step->hp) {
457 if (step->new_large_objects != NULL) {
458 scavenge_large(step);
465 if (flag) { goto loop; }
467 /* must be last... */
468 if (traverse_weak_ptr_list()) { /* returns rtsTrue if evaced something */
473 /* Final traversal of the weak pointer list (see comment by
474 * cleanUpWeakPtrList below).
476 cleanup_weak_ptr_list(&weak_ptr_list);
478 /* Now see which stable names are still alive.
480 gcStablePtrTable(major_gc);
482 /* revert dead CAFs and update enteredCAFs list */
485 /* Set the maximum blocks for the oldest generation, based on twice
486 * the amount of live data now, adjusted to fit the maximum heap
489 * This is an approximation, since in the worst case we'll need
490 * twice the amount of live data plus whatever space the other
493 if (RtsFlags.GcFlags.generations > 1) {
495 oldest_gen->max_blocks =
496 stg_max(oldest_gen->steps[0].to_blocks * RtsFlags.GcFlags.oldGenFactor,
497 RtsFlags.GcFlags.minOldGenSize);
498 if (oldest_gen->max_blocks > RtsFlags.GcFlags.maxHeapSize / 2) {
499 oldest_gen->max_blocks = RtsFlags.GcFlags.maxHeapSize / 2;
500 if (((int)oldest_gen->max_blocks -
501 (int)oldest_gen->steps[0].to_blocks) <
502 (RtsFlags.GcFlags.pcFreeHeap *
503 RtsFlags.GcFlags.maxHeapSize / 200)) {
510 /* run through all the generations/steps and tidy up
512 copied = new_blocks * BLOCK_SIZE_W;
513 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
516 generations[g].collections++; /* for stats */
519 for (s = 0; s < generations[g].n_steps; s++) {
521 step = &generations[g].steps[s];
523 if (!(g == 0 && s == 0 && RtsFlags.GcFlags.generations > 1)) {
524 /* Tidy the end of the to-space chains */
525 step->hp_bd->free = step->hp;
526 step->hp_bd->link = NULL;
527 /* stats information: how much we copied */
529 copied -= step->hp_bd->start + BLOCK_SIZE_W -
534 /* for generations we collected... */
537 collected += step->n_blocks * BLOCK_SIZE_W; /* for stats */
539 /* free old memory and shift to-space into from-space for all
540 * the collected steps (except the allocation area). These
541 * freed blocks will probaby be quickly recycled.
543 if (!(g == 0 && s == 0)) {
544 freeChain(step->blocks);
545 step->blocks = step->to_space;
546 step->n_blocks = step->to_blocks;
547 step->to_space = NULL;
549 for (bd = step->blocks; bd != NULL; bd = bd->link) {
550 bd->evacuated = 0; /* now from-space */
554 /* LARGE OBJECTS. The current live large objects are chained on
555 * scavenged_large, having been moved during garbage
556 * collection from large_objects. Any objects left on
557 * large_objects list are therefore dead, so we free them here.
559 for (bd = step->large_objects; bd != NULL; bd = next) {
564 for (bd = step->scavenged_large_objects; bd != NULL; bd = bd->link) {
567 step->large_objects = step->scavenged_large_objects;
569 /* Set the maximum blocks for this generation, interpolating
570 * between the maximum size of the oldest and youngest
573 * max_blocks = oldgen_max_blocks * G
574 * ----------------------
579 generations[g].max_blocks = (oldest_gen->max_blocks * g)
580 / (RtsFlags.GcFlags.generations-1);
582 generations[g].max_blocks = oldest_gen->max_blocks;
585 /* for older generations... */
588 /* For older generations, we need to append the
589 * scavenged_large_object list (i.e. large objects that have been
590 * promoted during this GC) to the large_object list for that step.
592 for (bd = step->scavenged_large_objects; bd; bd = next) {
595 dbl_link_onto(bd, &step->large_objects);
598 /* add the new blocks we promoted during this GC */
599 step->n_blocks += step->to_blocks;
604 /* Guess the amount of live data for stats. */
607 /* Free the small objects allocated via allocate(), since this will
608 * all have been copied into G0S1 now.
610 if (small_alloc_list != NULL) {
611 freeChain(small_alloc_list);
613 small_alloc_list = NULL;
617 alloc_blocks_lim = RtsFlags.GcFlags.minAllocAreaSize;
619 /* Two-space collector:
620 * Free the old to-space, and estimate the amount of live data.
622 if (RtsFlags.GcFlags.generations == 1) {
625 if (old_to_space != NULL) {
626 freeChain(old_to_space);
628 for (bd = g0s0->to_space; bd != NULL; bd = bd->link) {
629 bd->evacuated = 0; /* now from-space */
632 /* For a two-space collector, we need to resize the nursery. */
634 /* set up a new nursery. Allocate a nursery size based on a
635 * function of the amount of live data (currently a factor of 2,
636 * should be configurable (ToDo)). Use the blocks from the old
637 * nursery if possible, freeing up any left over blocks.
639 * If we get near the maximum heap size, then adjust our nursery
640 * size accordingly. If the nursery is the same size as the live
641 * data (L), then we need 3L bytes. We can reduce the size of the
642 * nursery to bring the required memory down near 2L bytes.
644 * A normal 2-space collector would need 4L bytes to give the same
645 * performance we get from 3L bytes, reducing to the same
646 * performance at 2L bytes.
648 blocks = g0s0->to_blocks;
650 if ( blocks * RtsFlags.GcFlags.oldGenFactor * 2 >
651 RtsFlags.GcFlags.maxHeapSize ) {
652 int adjusted_blocks; /* signed on purpose */
655 adjusted_blocks = (RtsFlags.GcFlags.maxHeapSize - 2 * blocks);
656 IF_DEBUG(gc, fprintf(stderr, "@@ Near maximum heap size of 0x%x blocks, blocks = %d, adjusted to %d\n", RtsFlags.GcFlags.maxHeapSize, blocks, adjusted_blocks));
657 pc_free = adjusted_blocks * 100 / RtsFlags.GcFlags.maxHeapSize;
658 if (pc_free < RtsFlags.GcFlags.pcFreeHeap) /* might even be < 0 */ {
661 blocks = adjusted_blocks;
664 blocks *= RtsFlags.GcFlags.oldGenFactor;
665 if (blocks < RtsFlags.GcFlags.minAllocAreaSize) {
666 blocks = RtsFlags.GcFlags.minAllocAreaSize;
669 resizeNursery(blocks);
672 /* Generational collector:
673 * If the user has given us a suggested heap size, adjust our
674 * allocation area to make best use of the memory available.
677 if (RtsFlags.GcFlags.heapSizeSuggestion) {
679 nat needed = calcNeeded(); /* approx blocks needed at next GC */
681 /* Guess how much will be live in generation 0 step 0 next time.
682 * A good approximation is the obtained by finding the
683 * percentage of g0s0 that was live at the last minor GC.
686 g0s0_pcnt_kept = (new_blocks * 100) / g0s0->n_blocks;
689 /* Estimate a size for the allocation area based on the
690 * information available. We might end up going slightly under
691 * or over the suggested heap size, but we should be pretty
694 * Formula: suggested - needed
695 * ----------------------------
696 * 1 + g0s0_pcnt_kept/100
698 * where 'needed' is the amount of memory needed at the next
699 * collection for collecting all steps except g0s0.
702 (((int)RtsFlags.GcFlags.heapSizeSuggestion - (int)needed) * 100) /
703 (100 + (int)g0s0_pcnt_kept);
705 if (blocks < (int)RtsFlags.GcFlags.minAllocAreaSize) {
706 blocks = RtsFlags.GcFlags.minAllocAreaSize;
709 resizeNursery((nat)blocks);
713 /* mark the garbage collected CAFs as dead */
715 if (major_gc) { gcCAFs(); }
718 /* zero the scavenged static object list */
720 zero_static_object_list(scavenged_static_objects);
728 /* Reconstruct the Global Address tables used in GUM */
729 RebuildGAtables(major_gc);
732 /* start any pending finalizers */
733 scheduleFinalizers(old_weak_ptr_list);
735 /* send exceptions to any threads which were about to die */
736 resurrectThreads(resurrected_threads);
738 /* check sanity after GC */
739 IF_DEBUG(sanity, checkSanity(N));
741 /* extra GC trace info */
742 IF_DEBUG(gc, stat_describe_gens());
745 /* symbol-table based profiling */
746 /* heapCensus(to_space); */ /* ToDo */
749 /* restore enclosing cost centre */
755 /* check for memory leaks if sanity checking is on */
756 IF_DEBUG(sanity, memInventory());
758 /* ok, GC over: tell the stats department what happened. */
759 stat_endGC(allocated, collected, live, copied, N);
762 //@node Weak Pointers, Evacuation, Garbage Collect
763 //@subsection Weak Pointers
765 /* -----------------------------------------------------------------------------
768 traverse_weak_ptr_list is called possibly many times during garbage
769 collection. It returns a flag indicating whether it did any work
770 (i.e. called evacuate on any live pointers).
772 Invariant: traverse_weak_ptr_list is called when the heap is in an
773 idempotent state. That means that there are no pending
774 evacuate/scavenge operations. This invariant helps the weak
775 pointer code decide which weak pointers are dead - if there are no
776 new live weak pointers, then all the currently unreachable ones are
779 For generational GC: we just don't try to finalize weak pointers in
780 older generations than the one we're collecting. This could
781 probably be optimised by keeping per-generation lists of weak
782 pointers, but for a few weak pointers this scheme will work.
783 -------------------------------------------------------------------------- */
784 //@cindex traverse_weak_ptr_list
787 traverse_weak_ptr_list(void)
789 StgWeak *w, **last_w, *next_w;
791 rtsBool flag = rtsFalse;
793 if (weak_done) { return rtsFalse; }
795 /* doesn't matter where we evacuate values/finalizers to, since
796 * these pointers are treated as roots (iff the keys are alive).
800 last_w = &old_weak_ptr_list;
801 for (w = old_weak_ptr_list; w; w = next_w) {
803 /* First, this weak pointer might have been evacuated. If so,
804 * remove the forwarding pointer from the weak_ptr_list.
806 if (get_itbl(w)->type == EVACUATED) {
807 w = (StgWeak *)((StgEvacuated *)w)->evacuee;
811 /* There might be a DEAD_WEAK on the list if finalizeWeak# was
812 * called on a live weak pointer object. Just remove it.
814 if (w->header.info == &DEAD_WEAK_info) {
815 next_w = ((StgDeadWeak *)w)->link;
820 ASSERT(get_itbl(w)->type == WEAK);
822 /* Now, check whether the key is reachable.
824 if ((new = isAlive(w->key))) {
826 /* evacuate the value and finalizer */
827 w->value = evacuate(w->value);
828 w->finalizer = evacuate(w->finalizer);
829 /* remove this weak ptr from the old_weak_ptr list */
831 /* and put it on the new weak ptr list */
833 w->link = weak_ptr_list;
836 IF_DEBUG(weak, fprintf(stderr,"Weak pointer still alive at %p -> %p\n", w, w->key));
846 /* Now deal with the all_threads list, which behaves somewhat like
847 * the weak ptr list. If we discover any threads that are about to
848 * become garbage, we wake them up and administer an exception.
851 StgTSO *t, *tmp, *next, **prev;
853 prev = &old_all_threads;
854 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
856 /* Threads which have finished or died get dropped from
859 switch (t->what_next) {
862 next = t->global_link;
868 /* Threads which have already been determined to be alive are
869 * moved onto the all_threads list.
871 (StgClosure *)tmp = isAlive((StgClosure *)t);
873 next = tmp->global_link;
874 tmp->global_link = all_threads;
878 prev = &(t->global_link);
879 next = t->global_link;
884 /* If we didn't make any changes, then we can go round and kill all
885 * the dead weak pointers. The old_weak_ptr list is used as a list
886 * of pending finalizers later on.
888 if (flag == rtsFalse) {
889 cleanup_weak_ptr_list(&old_weak_ptr_list);
890 for (w = old_weak_ptr_list; w; w = w->link) {
891 w->finalizer = evacuate(w->finalizer);
894 /* And resurrect any threads which were about to become garbage.
897 StgTSO *t, *tmp, *next;
898 for (t = old_all_threads; t != END_TSO_QUEUE; t = next) {
899 next = t->global_link;
900 (StgClosure *)tmp = evacuate((StgClosure *)t);
901 tmp->global_link = resurrected_threads;
902 resurrected_threads = tmp;
912 /* -----------------------------------------------------------------------------
913 After GC, the live weak pointer list may have forwarding pointers
914 on it, because a weak pointer object was evacuated after being
915 moved to the live weak pointer list. We remove those forwarding
918 Also, we don't consider weak pointer objects to be reachable, but
919 we must nevertheless consider them to be "live" and retain them.
920 Therefore any weak pointer objects which haven't as yet been
921 evacuated need to be evacuated now.
922 -------------------------------------------------------------------------- */
924 //@cindex cleanup_weak_ptr_list
927 cleanup_weak_ptr_list ( StgWeak **list )
929 StgWeak *w, **last_w;
932 for (w = *list; w; w = w->link) {
934 if (get_itbl(w)->type == EVACUATED) {
935 w = (StgWeak *)((StgEvacuated *)w)->evacuee;
939 if (Bdescr((P_)w)->evacuated == 0) {
940 (StgClosure *)w = evacuate((StgClosure *)w);
947 /* -----------------------------------------------------------------------------
948 isAlive determines whether the given closure is still alive (after
949 a garbage collection) or not. It returns the new address of the
950 closure if it is alive, or NULL otherwise.
951 -------------------------------------------------------------------------- */
956 isAlive(StgClosure *p)
958 const StgInfoTable *info;
965 /* ToDo: for static closures, check the static link field.
966 * Problem here is that we sometimes don't set the link field, eg.
967 * for static closures with an empty SRT or CONSTR_STATIC_NOCAFs.
970 #if 1 || !defined(PAR)
971 /* ignore closures in generations that we're not collecting. */
972 /* In GUM we use this routine when rebuilding GA tables; for some
973 reason it has problems with the LOOKS_LIKE_STATIC macro -- HWL */
974 if (LOOKS_LIKE_STATIC(p) || Bdescr((P_)p)->gen->no > N) {
979 switch (info->type) {
984 case IND_OLDGEN: /* rely on compatible layout with StgInd */
985 case IND_OLDGEN_PERM:
986 /* follow indirections */
987 p = ((StgInd *)p)->indirectee;
992 return ((StgEvacuated *)p)->evacuee;
995 size = bco_sizeW((StgBCO*)p);
999 size = arr_words_sizeW((StgArrWords *)p);
1003 case MUT_ARR_PTRS_FROZEN:
1004 size = mut_arr_ptrs_sizeW((StgMutArrPtrs *)p);
1008 if (((StgTSO *)p)->what_next == ThreadRelocated) {
1009 p = (StgClosure *)((StgTSO *)p)->link;
1013 size = tso_sizeW((StgTSO *)p);
1015 if (size >= LARGE_OBJECT_THRESHOLD/sizeof(W_)
1016 && Bdescr((P_)p)->evacuated)
1030 MarkRoot(StgClosure *root)
1032 return evacuate(root);
1036 static void addBlock(step *step)
1038 bdescr *bd = allocBlock();
1039 bd->gen = step->gen;
1042 if (step->gen->no <= N) {
1048 step->hp_bd->free = step->hp;
1049 step->hp_bd->link = bd;
1050 step->hp = bd->start;
1051 step->hpLim = step->hp + BLOCK_SIZE_W;
1057 //@cindex upd_evacuee
1059 static __inline__ void
1060 upd_evacuee(StgClosure *p, StgClosure *dest)
1062 p->header.info = &EVACUATED_info;
1063 ((StgEvacuated *)p)->evacuee = dest;
1068 static __inline__ StgClosure *
1069 copy(StgClosure *src, nat size, step *step)
1073 TICK_GC_WORDS_COPIED(size);
1074 /* Find out where we're going, using the handy "to" pointer in
1075 * the step of the source object. If it turns out we need to
1076 * evacuate to an older generation, adjust it here (see comment
1079 if (step->gen->no < evac_gen) {
1080 #ifdef NO_EAGER_PROMOTION
1081 failed_to_evac = rtsTrue;
1083 step = &generations[evac_gen].steps[0];
1087 /* chain a new block onto the to-space for the destination step if
1090 if (step->hp + size >= step->hpLim) {
1094 for(to = step->hp, from = (P_)src; size>0; --size) {
1100 upd_evacuee(src,(StgClosure *)dest);
1101 return (StgClosure *)dest;
1104 /* Special version of copy() for when we only want to copy the info
1105 * pointer of an object, but reserve some padding after it. This is
1106 * used to optimise evacuation of BLACKHOLEs.
1111 static __inline__ StgClosure *
1112 copyPart(StgClosure *src, nat size_to_reserve, nat size_to_copy, step *step)
1116 TICK_GC_WORDS_COPIED(size_to_copy);
1117 if (step->gen->no < evac_gen) {
1118 #ifdef NO_EAGER_PROMOTION
1119 failed_to_evac = rtsTrue;
1121 step = &generations[evac_gen].steps[0];
1125 if (step->hp + size_to_reserve >= step->hpLim) {
1129 for(to = step->hp, from = (P_)src; size_to_copy>0; --size_to_copy) {
1134 step->hp += size_to_reserve;
1135 upd_evacuee(src,(StgClosure *)dest);
1136 return (StgClosure *)dest;
1139 //@node Evacuation, Scavenging, Weak Pointers
1140 //@subsection Evacuation
1142 /* -----------------------------------------------------------------------------
1143 Evacuate a large object
1145 This just consists of removing the object from the (doubly-linked)
1146 large_alloc_list, and linking it on to the (singly-linked)
1147 new_large_objects list, from where it will be scavenged later.
1149 Convention: bd->evacuated is /= 0 for a large object that has been
1150 evacuated, or 0 otherwise.
1151 -------------------------------------------------------------------------- */
1153 //@cindex evacuate_large
1156 evacuate_large(StgPtr p, rtsBool mutable)
1158 bdescr *bd = Bdescr(p);
1161 /* should point to the beginning of the block */
1162 ASSERT(((W_)p & BLOCK_MASK) == 0);
1164 /* already evacuated? */
1165 if (bd->evacuated) {
1166 /* Don't forget to set the failed_to_evac flag if we didn't get
1167 * the desired destination (see comments in evacuate()).
1169 if (bd->gen->no < evac_gen) {
1170 failed_to_evac = rtsTrue;
1171 TICK_GC_FAILED_PROMOTION();
1177 /* remove from large_object list */
1179 bd->back->link = bd->link;
1180 } else { /* first object in the list */
1181 step->large_objects = bd->link;
1184 bd->link->back = bd->back;
1187 /* link it on to the evacuated large object list of the destination step
1189 step = bd->step->to;
1190 if (step->gen->no < evac_gen) {
1191 #ifdef NO_EAGER_PROMOTION
1192 failed_to_evac = rtsTrue;
1194 step = &generations[evac_gen].steps[0];
1199 bd->gen = step->gen;
1200 bd->link = step->new_large_objects;
1201 step->new_large_objects = bd;
1205 recordMutable((StgMutClosure *)p);
1209 /* -----------------------------------------------------------------------------
1210 Adding a MUT_CONS to an older generation.
1212 This is necessary from time to time when we end up with an
1213 old-to-new generation pointer in a non-mutable object. We defer
1214 the promotion until the next GC.
1215 -------------------------------------------------------------------------- */
1220 mkMutCons(StgClosure *ptr, generation *gen)
1225 step = &gen->steps[0];
1227 /* chain a new block onto the to-space for the destination step if
1230 if (step->hp + sizeofW(StgIndOldGen) >= step->hpLim) {
1234 q = (StgMutVar *)step->hp;
1235 step->hp += sizeofW(StgMutVar);
1237 SET_HDR(q,&MUT_CONS_info,CCS_GC);
1239 recordOldToNewPtrs((StgMutClosure *)q);
1241 return (StgClosure *)q;
1244 /* -----------------------------------------------------------------------------
1247 This is called (eventually) for every live object in the system.
1249 The caller to evacuate specifies a desired generation in the
1250 evac_gen global variable. The following conditions apply to
1251 evacuating an object which resides in generation M when we're
1252 collecting up to generation N
1256 else evac to step->to
1258 if M < evac_gen evac to evac_gen, step 0
1260 if the object is already evacuated, then we check which generation
1263 if M >= evac_gen do nothing
1264 if M < evac_gen set failed_to_evac flag to indicate that we
1265 didn't manage to evacuate this object into evac_gen.
1267 -------------------------------------------------------------------------- */
1271 evacuate(StgClosure *q)
1276 const StgInfoTable *info;
1279 if (HEAP_ALLOCED(q)) {
1281 if (bd->gen->no > N) {
1282 /* Can't evacuate this object, because it's in a generation
1283 * older than the ones we're collecting. Let's hope that it's
1284 * in evac_gen or older, or we will have to make an IND_OLDGEN object.
1286 if (bd->gen->no < evac_gen) {
1288 failed_to_evac = rtsTrue;
1289 TICK_GC_FAILED_PROMOTION();
1293 step = bd->step->to;
1296 else step = NULL; /* make sure copy() will crash if HEAP_ALLOCED is wrong */
1299 /* make sure the info pointer is into text space */
1300 ASSERT(q && (LOOKS_LIKE_GHC_INFO(GET_INFO(q))
1301 || IS_HUGS_CONSTR_INFO(GET_INFO(q))));
1304 if (info->type==RBH) {
1305 info = REVERT_INFOPTR(info);
1307 belch("@_ Trying to evacuate an RBH %p (%s); reverting to IP %p (%s)",
1308 q, info_type(q), info, info_type_by_ip(info)));
1312 switch (info -> type) {
1316 nat size = bco_sizeW((StgBCO*)q);
1318 if (size >= LARGE_OBJECT_THRESHOLD/sizeof(W_)) {
1319 evacuate_large((P_)q, rtsFalse);
1322 /* just copy the block */
1323 to = copy(q,size,step);
1329 ASSERT(q->header.info != &MUT_CONS_info);
1331 to = copy(q,sizeW_fromITBL(info),step);
1332 recordMutable((StgMutClosure *)to);
1339 return copy(q,sizeofW(StgHeader)+1,step);
1341 case THUNK_1_0: /* here because of MIN_UPD_SIZE */
1346 #ifdef NO_PROMOTE_THUNKS
1347 if (bd->gen->no == 0 &&
1348 bd->step->no != 0 &&
1349 bd->step->no == bd->gen->n_steps-1) {
1353 return copy(q,sizeofW(StgHeader)+2,step);
1361 return copy(q,sizeofW(StgHeader)+2,step);
1367 case IND_OLDGEN_PERM:
1373 return copy(q,sizeW_fromITBL(info),step);
1376 case SE_CAF_BLACKHOLE:
1379 return copyPart(q,BLACKHOLE_sizeW(),sizeofW(StgHeader),step);
1382 to = copy(q,BLACKHOLE_sizeW(),step);
1383 recordMutable((StgMutClosure *)to);
1386 case THUNK_SELECTOR:
1388 const StgInfoTable* selectee_info;
1389 StgClosure* selectee = ((StgSelector*)q)->selectee;
1392 selectee_info = get_itbl(selectee);
1393 switch (selectee_info->type) {
1402 StgWord32 offset = info->layout.selector_offset;
1404 /* check that the size is in range */
1406 (StgWord32)(selectee_info->layout.payload.ptrs +
1407 selectee_info->layout.payload.nptrs));
1409 /* perform the selection! */
1410 q = selectee->payload[offset];
1412 /* if we're already in to-space, there's no need to continue
1413 * with the evacuation, just update the source address with
1414 * a pointer to the (evacuated) constructor field.
1416 if (HEAP_ALLOCED(q)) {
1417 bdescr *bd = Bdescr((P_)q);
1418 if (bd->evacuated) {
1419 if (bd->gen->no < evac_gen) {
1420 failed_to_evac = rtsTrue;
1421 TICK_GC_FAILED_PROMOTION();
1427 /* otherwise, carry on and evacuate this constructor field,
1428 * (but not the constructor itself)
1437 case IND_OLDGEN_PERM:
1438 selectee = ((StgInd *)selectee)->indirectee;
1442 selectee = ((StgCAF *)selectee)->value;
1446 selectee = ((StgEvacuated *)selectee)->evacuee;
1456 case THUNK_SELECTOR:
1457 /* aargh - do recursively???? */
1460 case SE_CAF_BLACKHOLE:
1464 /* not evaluated yet */
1468 barf("evacuate: THUNK_SELECTOR: strange selectee %d",
1469 (int)(selectee_info->type));
1472 return copy(q,THUNK_SELECTOR_sizeW(),step);
1476 /* follow chains of indirections, don't evacuate them */
1477 q = ((StgInd*)q)->indirectee;
1481 if (info->srt_len > 0 && major_gc &&
1482 THUNK_STATIC_LINK((StgClosure *)q) == NULL) {
1483 THUNK_STATIC_LINK((StgClosure *)q) = static_objects;
1484 static_objects = (StgClosure *)q;
1489 if (info->srt_len > 0 && major_gc &&
1490 FUN_STATIC_LINK((StgClosure *)q) == NULL) {
1491 FUN_STATIC_LINK((StgClosure *)q) = static_objects;
1492 static_objects = (StgClosure *)q;
1497 if (major_gc && IND_STATIC_LINK((StgClosure *)q) == NULL) {
1498 IND_STATIC_LINK((StgClosure *)q) = static_objects;
1499 static_objects = (StgClosure *)q;
1504 if (major_gc && STATIC_LINK(info,(StgClosure *)q) == NULL) {
1505 STATIC_LINK(info,(StgClosure *)q) = static_objects;
1506 static_objects = (StgClosure *)q;
1510 case CONSTR_INTLIKE:
1511 case CONSTR_CHARLIKE:
1512 case CONSTR_NOCAF_STATIC:
1513 /* no need to put these on the static linked list, they don't need
1528 /* shouldn't see these */
1529 barf("evacuate: stack frame at %p\n", q);
1533 /* PAPs and AP_UPDs are special - the payload is a copy of a chunk
1534 * of stack, tagging and all.
1536 * They can be larger than a block in size. Both are only
1537 * allocated via allocate(), so they should be chained on to the
1538 * large_object list.
1541 nat size = pap_sizeW((StgPAP*)q);
1542 if (size >= LARGE_OBJECT_THRESHOLD/sizeof(W_)) {
1543 evacuate_large((P_)q, rtsFalse);
1546 return copy(q,size,step);
1551 /* Already evacuated, just return the forwarding address.
1552 * HOWEVER: if the requested destination generation (evac_gen) is
1553 * older than the actual generation (because the object was
1554 * already evacuated to a younger generation) then we have to
1555 * set the failed_to_evac flag to indicate that we couldn't
1556 * manage to promote the object to the desired generation.
1558 if (evac_gen > 0) { /* optimisation */
1559 StgClosure *p = ((StgEvacuated*)q)->evacuee;
1560 if (Bdescr((P_)p)->gen->no < evac_gen) {
1561 IF_DEBUG(gc, belch("@@ evacuate: evac of EVACUATED node %p failed!", p));
1562 failed_to_evac = rtsTrue;
1563 TICK_GC_FAILED_PROMOTION();
1566 return ((StgEvacuated*)q)->evacuee;
1570 nat size = arr_words_sizeW((StgArrWords *)q);
1572 if (size >= LARGE_OBJECT_THRESHOLD/sizeof(W_)) {
1573 evacuate_large((P_)q, rtsFalse);
1576 /* just copy the block */
1577 return copy(q,size,step);
1582 case MUT_ARR_PTRS_FROZEN:
1584 nat size = mut_arr_ptrs_sizeW((StgMutArrPtrs *)q);
1586 if (size >= LARGE_OBJECT_THRESHOLD/sizeof(W_)) {
1587 evacuate_large((P_)q, info->type == MUT_ARR_PTRS);
1590 /* just copy the block */
1591 to = copy(q,size,step);
1592 if (info->type == MUT_ARR_PTRS) {
1593 recordMutable((StgMutClosure *)to);
1601 StgTSO *tso = (StgTSO *)q;
1602 nat size = tso_sizeW(tso);
1605 /* Deal with redirected TSOs (a TSO that's had its stack enlarged).
1607 if (tso->what_next == ThreadRelocated) {
1608 q = (StgClosure *)tso->link;
1612 /* Large TSOs don't get moved, so no relocation is required.
1614 if (size >= LARGE_OBJECT_THRESHOLD/sizeof(W_)) {
1615 evacuate_large((P_)q, rtsTrue);
1618 /* To evacuate a small TSO, we need to relocate the update frame
1622 StgTSO *new_tso = (StgTSO *)copy((StgClosure *)tso,tso_sizeW(tso),step);
1624 diff = (StgPtr)new_tso - (StgPtr)tso; /* In *words* */
1626 /* relocate the stack pointers... */
1627 new_tso->su = (StgUpdateFrame *) ((StgPtr)new_tso->su + diff);
1628 new_tso->sp = (StgPtr)new_tso->sp + diff;
1629 new_tso->splim = (StgPtr)new_tso->splim + diff;
1631 relocate_TSO(tso, new_tso);
1633 recordMutable((StgMutClosure *)new_tso);
1634 return (StgClosure *)new_tso;
1639 case RBH: // cf. BLACKHOLE_BQ
1641 //StgInfoTable *rip = get_closure_info(q, &size, &ptrs, &nonptrs, &vhs, str);
1642 to = copy(q,BLACKHOLE_sizeW(),step);
1643 //ToDo: derive size etc from reverted IP
1644 //to = copy(q,size,step);
1645 recordMutable((StgMutClosure *)to);
1647 belch("@@ evacuate: RBH %p (%s) to %p (%s)",
1648 q, info_type(q), to, info_type(to)));
1653 ASSERT(sizeofW(StgBlockedFetch) >= MIN_NONUPD_SIZE);
1654 to = copy(q,sizeofW(StgBlockedFetch),step);
1656 belch("@@ evacuate: %p (%s) to %p (%s)",
1657 q, info_type(q), to, info_type(to)));
1661 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1662 to = copy(q,sizeofW(StgFetchMe),step);
1664 belch("@@ evacuate: %p (%s) to %p (%s)",
1665 q, info_type(q), to, info_type(to)));
1669 ASSERT(sizeofW(StgBlockedFetch) >= MIN_UPD_SIZE);
1670 to = copy(q,sizeofW(StgFetchMeBlockingQueue),step);
1672 belch("@@ evacuate: %p (%s) to %p (%s)",
1673 q, info_type(q), to, info_type(to)));
1678 barf("evacuate: strange closure type %d", (int)(info->type));
1684 /* -----------------------------------------------------------------------------
1685 relocate_TSO is called just after a TSO has been copied from src to
1686 dest. It adjusts the update frame list for the new location.
1687 -------------------------------------------------------------------------- */
1688 //@cindex relocate_TSO
1691 relocate_TSO(StgTSO *src, StgTSO *dest)
1698 diff = (StgPtr)dest->sp - (StgPtr)src->sp; /* In *words* */
1702 while ((P_)su < dest->stack + dest->stack_size) {
1703 switch (get_itbl(su)->type) {
1705 /* GCC actually manages to common up these three cases! */
1708 su->link = (StgUpdateFrame *) ((StgPtr)su->link + diff);
1713 cf = (StgCatchFrame *)su;
1714 cf->link = (StgUpdateFrame *) ((StgPtr)cf->link + diff);
1719 sf = (StgSeqFrame *)su;
1720 sf->link = (StgUpdateFrame *) ((StgPtr)sf->link + diff);
1729 barf("relocate_TSO %d", (int)(get_itbl(su)->type));
1737 //@node Scavenging, Reverting CAFs, Evacuation
1738 //@subsection Scavenging
1740 //@cindex scavenge_srt
1743 scavenge_srt(const StgInfoTable *info)
1745 StgClosure **srt, **srt_end;
1747 /* evacuate the SRT. If srt_len is zero, then there isn't an
1748 * srt field in the info table. That's ok, because we'll
1749 * never dereference it.
1751 srt = (StgClosure **)(info->srt);
1752 srt_end = srt + info->srt_len;
1753 for (; srt < srt_end; srt++) {
1754 /* Special-case to handle references to closures hiding out in DLLs, since
1755 double indirections required to get at those. The code generator knows
1756 which is which when generating the SRT, so it stores the (indirect)
1757 reference to the DLL closure in the table by first adding one to it.
1758 We check for this here, and undo the addition before evacuating it.
1760 If the SRT entry hasn't got bit 0 set, the SRT entry points to a
1761 closure that's fixed at link-time, and no extra magic is required.
1763 #ifdef ENABLE_WIN32_DLL_SUPPORT
1764 if ( (unsigned long)(*srt) & 0x1 ) {
1765 evacuate(*stgCast(StgClosure**,(stgCast(unsigned long, *srt) & ~0x1)));
1775 /* -----------------------------------------------------------------------------
1777 -------------------------------------------------------------------------- */
1780 scavengeTSO (StgTSO *tso)
1782 /* chase the link field for any TSOs on the same queue */
1783 (StgClosure *)tso->link = evacuate((StgClosure *)tso->link);
1784 if ( tso->why_blocked == BlockedOnMVar
1785 || tso->why_blocked == BlockedOnBlackHole
1786 || tso->why_blocked == BlockedOnException) {
1787 tso->block_info.closure = evacuate(tso->block_info.closure);
1789 if ( tso->blocked_exceptions != NULL ) {
1790 tso->blocked_exceptions =
1791 (StgTSO *)evacuate((StgClosure *)tso->blocked_exceptions);
1793 /* scavenge this thread's stack */
1794 scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
1797 /* -----------------------------------------------------------------------------
1798 Scavenge a given step until there are no more objects in this step
1801 evac_gen is set by the caller to be either zero (for a step in a
1802 generation < N) or G where G is the generation of the step being
1805 We sometimes temporarily change evac_gen back to zero if we're
1806 scavenging a mutable object where early promotion isn't such a good
1808 -------------------------------------------------------------------------- */
1812 scavenge(step *step)
1815 const StgInfoTable *info;
1817 nat saved_evac_gen = evac_gen; /* used for temporarily changing evac_gen */
1822 failed_to_evac = rtsFalse;
1824 /* scavenge phase - standard breadth-first scavenging of the
1828 while (bd != step->hp_bd || p < step->hp) {
1830 /* If we're at the end of this block, move on to the next block */
1831 if (bd != step->hp_bd && p == bd->free) {
1837 q = p; /* save ptr to object */
1839 ASSERT(p && (LOOKS_LIKE_GHC_INFO(GET_INFO((StgClosure *)p))
1840 || IS_HUGS_CONSTR_INFO(GET_INFO((StgClosure *)p))));
1842 info = get_itbl((StgClosure *)p);
1844 if (info->type==RBH)
1845 info = REVERT_INFOPTR(info);
1848 switch (info -> type) {
1852 StgBCO* bco = (StgBCO *)p;
1854 for (i = 0; i < bco->n_ptrs; i++) {
1855 bcoConstCPtr(bco,i) = evacuate(bcoConstCPtr(bco,i));
1857 p += bco_sizeW(bco);
1862 /* treat MVars specially, because we don't want to evacuate the
1863 * mut_link field in the middle of the closure.
1866 StgMVar *mvar = ((StgMVar *)p);
1868 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
1869 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
1870 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
1871 p += sizeofW(StgMVar);
1872 evac_gen = saved_evac_gen;
1880 ((StgClosure *)p)->payload[1] = evacuate(((StgClosure *)p)->payload[1]);
1881 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
1882 p += sizeofW(StgHeader) + 2;
1887 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
1888 p += sizeofW(StgHeader) + 2; /* MIN_UPD_SIZE */
1894 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
1895 p += sizeofW(StgHeader) + 1;
1900 p += sizeofW(StgHeader) + 2; /* MIN_UPD_SIZE */
1906 p += sizeofW(StgHeader) + 1;
1913 p += sizeofW(StgHeader) + 2;
1920 ((StgClosure *)p)->payload[0] = evacuate(((StgClosure *)p)->payload[0]);
1921 p += sizeofW(StgHeader) + 2;
1936 end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
1937 for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
1938 (StgClosure *)*p = evacuate((StgClosure *)*p);
1940 p += info->layout.payload.nptrs;
1945 if (step->gen->no != 0) {
1946 SET_INFO(((StgClosure *)p), &IND_OLDGEN_PERM_info);
1949 case IND_OLDGEN_PERM:
1950 ((StgIndOldGen *)p)->indirectee =
1951 evacuate(((StgIndOldGen *)p)->indirectee);
1952 if (failed_to_evac) {
1953 failed_to_evac = rtsFalse;
1954 recordOldToNewPtrs((StgMutClosure *)p);
1956 p += sizeofW(StgIndOldGen);
1961 StgCAF *caf = (StgCAF *)p;
1963 caf->body = evacuate(caf->body);
1964 if (failed_to_evac) {
1965 failed_to_evac = rtsFalse;
1966 recordOldToNewPtrs((StgMutClosure *)p);
1968 caf->mut_link = NULL;
1970 p += sizeofW(StgCAF);
1976 StgCAF *caf = (StgCAF *)p;
1978 caf->body = evacuate(caf->body);
1979 caf->value = evacuate(caf->value);
1980 if (failed_to_evac) {
1981 failed_to_evac = rtsFalse;
1982 recordOldToNewPtrs((StgMutClosure *)p);
1984 caf->mut_link = NULL;
1986 p += sizeofW(StgCAF);
1991 /* ignore MUT_CONSs */
1992 if (((StgMutVar *)p)->header.info != &MUT_CONS_info) {
1994 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
1995 evac_gen = saved_evac_gen;
1997 p += sizeofW(StgMutVar);
2001 case SE_CAF_BLACKHOLE:
2004 p += BLACKHOLE_sizeW();
2009 StgBlockingQueue *bh = (StgBlockingQueue *)p;
2010 (StgClosure *)bh->blocking_queue =
2011 evacuate((StgClosure *)bh->blocking_queue);
2012 if (failed_to_evac) {
2013 failed_to_evac = rtsFalse;
2014 recordMutable((StgMutClosure *)bh);
2016 p += BLACKHOLE_sizeW();
2020 case THUNK_SELECTOR:
2022 StgSelector *s = (StgSelector *)p;
2023 s->selectee = evacuate(s->selectee);
2024 p += THUNK_SELECTOR_sizeW();
2030 barf("scavenge:IND???\n");
2032 case CONSTR_INTLIKE:
2033 case CONSTR_CHARLIKE:
2035 case CONSTR_NOCAF_STATIC:
2039 /* Shouldn't see a static object here. */
2040 barf("scavenge: STATIC object\n");
2052 /* Shouldn't see stack frames here. */
2053 barf("scavenge: stack frame\n");
2055 case AP_UPD: /* same as PAPs */
2057 /* Treat a PAP just like a section of stack, not forgetting to
2058 * evacuate the function pointer too...
2061 StgPAP* pap = (StgPAP *)p;
2063 pap->fun = evacuate(pap->fun);
2064 scavenge_stack((P_)pap->payload, (P_)pap->payload + pap->n_args);
2065 p += pap_sizeW(pap);
2070 /* nothing to follow */
2071 p += arr_words_sizeW((StgArrWords *)p);
2075 /* follow everything */
2079 evac_gen = 0; /* repeatedly mutable */
2080 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2081 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2082 (StgClosure *)*p = evacuate((StgClosure *)*p);
2084 evac_gen = saved_evac_gen;
2088 case MUT_ARR_PTRS_FROZEN:
2089 /* follow everything */
2091 StgPtr start = p, next;
2093 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2094 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2095 (StgClosure *)*p = evacuate((StgClosure *)*p);
2097 if (failed_to_evac) {
2098 /* we can do this easier... */
2099 recordMutable((StgMutClosure *)start);
2100 failed_to_evac = rtsFalse;
2107 StgTSO *tso = (StgTSO *)p;
2110 evac_gen = saved_evac_gen;
2111 p += tso_sizeW(tso);
2116 case RBH: // cf. BLACKHOLE_BQ
2118 // nat size, ptrs, nonptrs, vhs;
2120 // StgInfoTable *rip = get_closure_info(p, &size, &ptrs, &nonptrs, &vhs, str);
2121 StgRBH *rbh = (StgRBH *)p;
2122 (StgClosure *)rbh->blocking_queue =
2123 evacuate((StgClosure *)rbh->blocking_queue);
2124 if (failed_to_evac) {
2125 failed_to_evac = rtsFalse;
2126 recordMutable((StgMutClosure *)rbh);
2129 belch("@@ scavenge: RBH %p (%s) (new blocking_queue link=%p)",
2130 p, info_type(p), (StgClosure *)rbh->blocking_queue));
2131 // ToDo: use size of reverted closure here!
2132 p += BLACKHOLE_sizeW();
2138 StgBlockedFetch *bf = (StgBlockedFetch *)p;
2139 /* follow the pointer to the node which is being demanded */
2140 (StgClosure *)bf->node =
2141 evacuate((StgClosure *)bf->node);
2142 /* follow the link to the rest of the blocking queue */
2143 (StgClosure *)bf->link =
2144 evacuate((StgClosure *)bf->link);
2145 if (failed_to_evac) {
2146 failed_to_evac = rtsFalse;
2147 recordMutable((StgMutClosure *)bf);
2150 belch("@@ scavenge: %p (%s); node is now %p; exciting, isn't it",
2151 bf, info_type((StgClosure *)bf),
2152 bf->node, info_type(bf->node)));
2153 p += sizeofW(StgBlockedFetch);
2159 belch("@@ scavenge: HWL claims nothing to do for %p (%s)",
2160 p, info_type((StgClosure *)p)));
2161 p += sizeofW(StgFetchMe);
2162 break; // nothing to do in this case
2164 case FETCH_ME_BQ: // cf. BLACKHOLE_BQ
2166 StgFetchMeBlockingQueue *fmbq = (StgFetchMeBlockingQueue *)p;
2167 (StgClosure *)fmbq->blocking_queue =
2168 evacuate((StgClosure *)fmbq->blocking_queue);
2169 if (failed_to_evac) {
2170 failed_to_evac = rtsFalse;
2171 recordMutable((StgMutClosure *)fmbq);
2174 belch("@@ scavenge: %p (%s) exciting, isn't it",
2175 p, info_type((StgClosure *)p)));
2176 p += sizeofW(StgFetchMeBlockingQueue);
2182 barf("scavenge: unimplemented/strange closure type\n");
2188 /* If we didn't manage to promote all the objects pointed to by
2189 * the current object, then we have to designate this object as
2190 * mutable (because it contains old-to-new generation pointers).
2192 if (failed_to_evac) {
2193 mkMutCons((StgClosure *)q, &generations[evac_gen]);
2194 failed_to_evac = rtsFalse;
2202 /* -----------------------------------------------------------------------------
2203 Scavenge one object.
2205 This is used for objects that are temporarily marked as mutable
2206 because they contain old-to-new generation pointers. Only certain
2207 objects can have this property.
2208 -------------------------------------------------------------------------- */
2209 //@cindex scavenge_one
2212 scavenge_one(StgClosure *p)
2214 const StgInfoTable *info;
2217 ASSERT(p && (LOOKS_LIKE_GHC_INFO(GET_INFO(p))
2218 || IS_HUGS_CONSTR_INFO(GET_INFO(p))));
2223 if (info->type==RBH)
2224 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
2227 switch (info -> type) {
2230 case FUN_1_0: /* hardly worth specialising these guys */
2250 case IND_OLDGEN_PERM:
2255 end = (P_)p->payload + info->layout.payload.ptrs;
2256 for (q = (P_)p->payload; q < end; q++) {
2257 (StgClosure *)*q = evacuate((StgClosure *)*q);
2263 case SE_CAF_BLACKHOLE:
2268 case THUNK_SELECTOR:
2270 StgSelector *s = (StgSelector *)p;
2271 s->selectee = evacuate(s->selectee);
2275 case AP_UPD: /* same as PAPs */
2277 /* Treat a PAP just like a section of stack, not forgetting to
2278 * evacuate the function pointer too...
2281 StgPAP* pap = (StgPAP *)p;
2283 pap->fun = evacuate(pap->fun);
2284 scavenge_stack((P_)pap->payload, (P_)pap->payload + pap->n_args);
2289 /* This might happen if for instance a MUT_CONS was pointing to a
2290 * THUNK which has since been updated. The IND_OLDGEN will
2291 * be on the mutable list anyway, so we don't need to do anything
2297 barf("scavenge_one: strange object");
2300 no_luck = failed_to_evac;
2301 failed_to_evac = rtsFalse;
2306 /* -----------------------------------------------------------------------------
2307 Scavenging mutable lists.
2309 We treat the mutable list of each generation > N (i.e. all the
2310 generations older than the one being collected) as roots. We also
2311 remove non-mutable objects from the mutable list at this point.
2312 -------------------------------------------------------------------------- */
2313 //@cindex scavenge_mut_once_list
2316 scavenge_mut_once_list(generation *gen)
2318 const StgInfoTable *info;
2319 StgMutClosure *p, *next, *new_list;
2321 p = gen->mut_once_list;
2322 new_list = END_MUT_LIST;
2326 failed_to_evac = rtsFalse;
2328 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
2330 /* make sure the info pointer is into text space */
2331 ASSERT(p && (LOOKS_LIKE_GHC_INFO(GET_INFO(p))
2332 || IS_HUGS_CONSTR_INFO(GET_INFO(p))));
2336 if (info->type==RBH)
2337 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
2339 switch(info->type) {
2342 case IND_OLDGEN_PERM:
2344 /* Try to pull the indirectee into this generation, so we can
2345 * remove the indirection from the mutable list.
2347 ((StgIndOldGen *)p)->indirectee =
2348 evacuate(((StgIndOldGen *)p)->indirectee);
2351 if (RtsFlags.DebugFlags.gc)
2352 /* Debugging code to print out the size of the thing we just
2356 StgPtr start = gen->steps[0].scan;
2357 bdescr *start_bd = gen->steps[0].scan_bd;
2359 scavenge(&gen->steps[0]);
2360 if (start_bd != gen->steps[0].scan_bd) {
2361 size += (P_)BLOCK_ROUND_UP(start) - start;
2362 start_bd = start_bd->link;
2363 while (start_bd != gen->steps[0].scan_bd) {
2364 size += BLOCK_SIZE_W;
2365 start_bd = start_bd->link;
2367 size += gen->steps[0].scan -
2368 (P_)BLOCK_ROUND_DOWN(gen->steps[0].scan);
2370 size = gen->steps[0].scan - start;
2372 fprintf(stderr,"evac IND_OLDGEN: %d bytes\n", size * sizeof(W_));
2376 /* failed_to_evac might happen if we've got more than two
2377 * generations, we're collecting only generation 0, the
2378 * indirection resides in generation 2 and the indirectee is
2381 if (failed_to_evac) {
2382 failed_to_evac = rtsFalse;
2383 p->mut_link = new_list;
2386 /* the mut_link field of an IND_STATIC is overloaded as the
2387 * static link field too (it just so happens that we don't need
2388 * both at the same time), so we need to NULL it out when
2389 * removing this object from the mutable list because the static
2390 * link fields are all assumed to be NULL before doing a major
2398 /* MUT_CONS is a kind of MUT_VAR, except it that we try to remove
2399 * it from the mutable list if possible by promoting whatever it
2402 ASSERT(p->header.info == &MUT_CONS_info);
2403 if (scavenge_one(((StgMutVar *)p)->var) == rtsTrue) {
2404 /* didn't manage to promote everything, so put the
2405 * MUT_CONS back on the list.
2407 p->mut_link = new_list;
2414 StgCAF *caf = (StgCAF *)p;
2415 caf->body = evacuate(caf->body);
2416 caf->value = evacuate(caf->value);
2417 if (failed_to_evac) {
2418 failed_to_evac = rtsFalse;
2419 p->mut_link = new_list;
2429 StgCAF *caf = (StgCAF *)p;
2430 caf->body = evacuate(caf->body);
2431 if (failed_to_evac) {
2432 failed_to_evac = rtsFalse;
2433 p->mut_link = new_list;
2442 /* shouldn't have anything else on the mutables list */
2443 barf("scavenge_mut_once_list: strange object? %d", (int)(info->type));
2447 gen->mut_once_list = new_list;
2450 //@cindex scavenge_mutable_list
2453 scavenge_mutable_list(generation *gen)
2455 const StgInfoTable *info;
2456 StgMutClosure *p, *next;
2458 p = gen->saved_mut_list;
2462 failed_to_evac = rtsFalse;
2464 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
2466 /* make sure the info pointer is into text space */
2467 ASSERT(p && (LOOKS_LIKE_GHC_INFO(GET_INFO(p))
2468 || IS_HUGS_CONSTR_INFO(GET_INFO(p))));
2472 if (info->type==RBH)
2473 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
2475 switch(info->type) {
2477 case MUT_ARR_PTRS_FROZEN:
2478 /* remove this guy from the mutable list, but follow the ptrs
2479 * anyway (and make sure they get promoted to this gen).
2485 belch("@@ scavenge_mut_list: scavenging MUT_ARR_PTRS_FROZEN %p; size: %#x ; next: %p",
2486 p, mut_arr_ptrs_sizeW((StgMutArrPtrs*)p), p->mut_link));
2488 end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2490 for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
2491 (StgClosure *)*q = evacuate((StgClosure *)*q);
2495 if (failed_to_evac) {
2496 failed_to_evac = rtsFalse;
2497 p->mut_link = gen->mut_list;
2504 /* follow everything */
2505 p->mut_link = gen->mut_list;
2511 belch("@@ scavenge_mut_list: scavenging MUT_ARR_PTRS %p; size: %#x ; next: %p",
2512 p, mut_arr_ptrs_sizeW((StgMutArrPtrs*)p), p->mut_link));
2514 end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2515 for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
2516 (StgClosure *)*q = evacuate((StgClosure *)*q);
2522 /* MUT_CONS is a kind of MUT_VAR, except that we try to remove
2523 * it from the mutable list if possible by promoting whatever it
2527 belch("@@ scavenge_mut_list: scavenging MUT_VAR %p; var: %p ; next: %p",
2528 p, ((StgMutVar *)p)->var, p->mut_link));
2530 ASSERT(p->header.info != &MUT_CONS_info);
2531 ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
2532 p->mut_link = gen->mut_list;
2538 StgMVar *mvar = (StgMVar *)p;
2541 belch("@@ scavenge_mut_list: scavenging MAVR %p; head: %p; tail: %p; value: %p ; next: %p",
2542 mvar, mvar->head, mvar->tail, mvar->value, p->mut_link));
2544 (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
2545 (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
2546 (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
2547 p->mut_link = gen->mut_list;
2554 StgTSO *tso = (StgTSO *)p;
2558 /* Don't take this TSO off the mutable list - it might still
2559 * point to some younger objects (because we set evac_gen to 0
2562 tso->mut_link = gen->mut_list;
2563 gen->mut_list = (StgMutClosure *)tso;
2569 StgBlockingQueue *bh = (StgBlockingQueue *)p;
2572 belch("@@ scavenge_mut_list: scavenging BLACKHOLE_BQ (%p); next: %p",
2575 (StgClosure *)bh->blocking_queue =
2576 evacuate((StgClosure *)bh->blocking_queue);
2577 p->mut_link = gen->mut_list;
2582 /* Happens if a BLACKHOLE_BQ in the old generation is updated:
2585 case IND_OLDGEN_PERM:
2586 /* Try to pull the indirectee into this generation, so we can
2587 * remove the indirection from the mutable list.
2590 ((StgIndOldGen *)p)->indirectee =
2591 evacuate(((StgIndOldGen *)p)->indirectee);
2594 if (failed_to_evac) {
2595 failed_to_evac = rtsFalse;
2596 p->mut_link = gen->mut_once_list;
2597 gen->mut_once_list = p;
2603 // HWL: old PAR code deleted here
2606 /* shouldn't have anything else on the mutables list */
2607 barf("scavenge_mutable_list: strange object? %d", (int)(info->type));
2612 //@cindex scavenge_static
2615 scavenge_static(void)
2617 StgClosure* p = static_objects;
2618 const StgInfoTable *info;
2620 /* Always evacuate straight to the oldest generation for static
2622 evac_gen = oldest_gen->no;
2624 /* keep going until we've scavenged all the objects on the linked
2626 while (p != END_OF_STATIC_LIST) {
2630 if (info->type==RBH)
2631 info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
2633 /* make sure the info pointer is into text space */
2634 ASSERT(p && (LOOKS_LIKE_GHC_INFO(GET_INFO(p))
2635 || IS_HUGS_CONSTR_INFO(GET_INFO(p))));
2637 /* Take this object *off* the static_objects list,
2638 * and put it on the scavenged_static_objects list.
2640 static_objects = STATIC_LINK(info,p);
2641 STATIC_LINK(info,p) = scavenged_static_objects;
2642 scavenged_static_objects = p;
2644 switch (info -> type) {
2648 StgInd *ind = (StgInd *)p;
2649 ind->indirectee = evacuate(ind->indirectee);
2651 /* might fail to evacuate it, in which case we have to pop it
2652 * back on the mutable list (and take it off the
2653 * scavenged_static list because the static link and mut link
2654 * pointers are one and the same).
2656 if (failed_to_evac) {
2657 failed_to_evac = rtsFalse;
2658 scavenged_static_objects = STATIC_LINK(info,p);
2659 ((StgMutClosure *)ind)->mut_link = oldest_gen->mut_once_list;
2660 oldest_gen->mut_once_list = (StgMutClosure *)ind;
2674 next = (P_)p->payload + info->layout.payload.ptrs;
2675 /* evacuate the pointers */
2676 for (q = (P_)p->payload; q < next; q++) {
2677 (StgClosure *)*q = evacuate((StgClosure *)*q);
2683 barf("scavenge_static");
2686 ASSERT(failed_to_evac == rtsFalse);
2688 /* get the next static object from the list. Remeber, there might
2689 * be more stuff on this list now that we've done some evacuating!
2690 * (static_objects is a global)
2696 /* -----------------------------------------------------------------------------
2697 scavenge_stack walks over a section of stack and evacuates all the
2698 objects pointed to by it. We can use the same code for walking
2699 PAPs, since these are just sections of copied stack.
2700 -------------------------------------------------------------------------- */
2701 //@cindex scavenge_stack
2704 scavenge_stack(StgPtr p, StgPtr stack_end)
2707 const StgInfoTable* info;
2710 IF_DEBUG(sanity, belch(" scavenging stack between %p and %p", p, stack_end));
2713 * Each time around this loop, we are looking at a chunk of stack
2714 * that starts with either a pending argument section or an
2715 * activation record.
2718 while (p < stack_end) {
2721 /* If we've got a tag, skip over that many words on the stack */
2722 if (IS_ARG_TAG((W_)q)) {
2727 /* Is q a pointer to a closure?
2729 if (! LOOKS_LIKE_GHC_INFO(q) ) {
2731 if ( 0 && LOOKS_LIKE_STATIC_CLOSURE(q) ) { /* Is it a static closure? */
2732 ASSERT(closure_STATIC((StgClosure *)q));
2734 /* otherwise, must be a pointer into the allocation space. */
2737 (StgClosure *)*p = evacuate((StgClosure *)q);
2743 * Otherwise, q must be the info pointer of an activation
2744 * record. All activation records have 'bitmap' style layout
2747 info = get_itbl((StgClosure *)p);
2749 switch (info->type) {
2751 /* Dynamic bitmap: the mask is stored on the stack */
2753 bitmap = ((StgRetDyn *)p)->liveness;
2754 p = (P_)&((StgRetDyn *)p)->payload[0];
2757 /* probably a slow-entry point return address: */
2765 belch("HWL: scavenge_stack: FUN(_STATIC) adjusting p from %p to %p (instead of %p)",
2766 old_p, p, old_p+1));
2768 p++; /* what if FHS!=1 !? -- HWL */
2773 /* Specialised code for update frames, since they're so common.
2774 * We *know* the updatee points to a BLACKHOLE, CAF_BLACKHOLE,
2775 * or BLACKHOLE_BQ, so just inline the code to evacuate it here.
2779 StgUpdateFrame *frame = (StgUpdateFrame *)p;
2781 nat type = get_itbl(frame->updatee)->type;
2783 p += sizeofW(StgUpdateFrame);
2784 if (type == EVACUATED) {
2785 frame->updatee = evacuate(frame->updatee);
2788 bdescr *bd = Bdescr((P_)frame->updatee);
2790 if (bd->gen->no > N) {
2791 if (bd->gen->no < evac_gen) {
2792 failed_to_evac = rtsTrue;
2797 /* Don't promote blackholes */
2799 if (!(step->gen->no == 0 &&
2801 step->no == step->gen->n_steps-1)) {
2808 to = copyPart(frame->updatee, BLACKHOLE_sizeW(),
2809 sizeofW(StgHeader), step);
2810 frame->updatee = to;
2813 to = copy(frame->updatee, BLACKHOLE_sizeW(), step);
2814 frame->updatee = to;
2815 recordMutable((StgMutClosure *)to);
2818 /* will never be SE_{,CAF_}BLACKHOLE, since we
2819 don't push an update frame for single-entry thunks. KSW 1999-01. */
2820 barf("scavenge_stack: UPDATE_FRAME updatee");
2825 /* small bitmap (< 32 entries, or 64 on a 64-bit machine) */
2832 bitmap = info->layout.bitmap;
2834 /* this assumes that the payload starts immediately after the info-ptr */
2836 while (bitmap != 0) {
2837 if ((bitmap & 1) == 0) {
2838 (StgClosure *)*p = evacuate((StgClosure *)*p);
2841 bitmap = bitmap >> 1;
2848 /* large bitmap (> 32 entries) */
2853 StgLargeBitmap *large_bitmap;
2856 large_bitmap = info->layout.large_bitmap;
2859 for (i=0; i<large_bitmap->size; i++) {
2860 bitmap = large_bitmap->bitmap[i];
2861 q = p + sizeof(W_) * 8;
2862 while (bitmap != 0) {
2863 if ((bitmap & 1) == 0) {
2864 (StgClosure *)*p = evacuate((StgClosure *)*p);
2867 bitmap = bitmap >> 1;
2869 if (i+1 < large_bitmap->size) {
2871 (StgClosure *)*p = evacuate((StgClosure *)*p);
2877 /* and don't forget to follow the SRT */
2882 barf("scavenge_stack: weird activation record found on stack.\n");
2887 /*-----------------------------------------------------------------------------
2888 scavenge the large object list.
2890 evac_gen set by caller; similar games played with evac_gen as with
2891 scavenge() - see comment at the top of scavenge(). Most large
2892 objects are (repeatedly) mutable, so most of the time evac_gen will
2894 --------------------------------------------------------------------------- */
2895 //@cindex scavenge_large
2898 scavenge_large(step *step)
2902 const StgInfoTable* info;
2903 nat saved_evac_gen = evac_gen; /* used for temporarily changing evac_gen */
2905 evac_gen = 0; /* most objects are mutable */
2906 bd = step->new_large_objects;
2908 for (; bd != NULL; bd = step->new_large_objects) {
2910 /* take this object *off* the large objects list and put it on
2911 * the scavenged large objects list. This is so that we can
2912 * treat new_large_objects as a stack and push new objects on
2913 * the front when evacuating.
2915 step->new_large_objects = bd->link;
2916 dbl_link_onto(bd, &step->scavenged_large_objects);
2919 info = get_itbl((StgClosure *)p);
2921 switch (info->type) {
2923 /* only certain objects can be "large"... */
2926 /* nothing to follow */
2930 /* follow everything */
2934 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2935 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2936 (StgClosure *)*p = evacuate((StgClosure *)*p);
2941 case MUT_ARR_PTRS_FROZEN:
2942 /* follow everything */
2944 StgPtr start = p, next;
2946 evac_gen = saved_evac_gen; /* not really mutable */
2947 next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
2948 for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
2949 (StgClosure *)*p = evacuate((StgClosure *)*p);
2952 if (failed_to_evac) {
2953 recordMutable((StgMutClosure *)start);
2960 StgBCO* bco = (StgBCO *)p;
2962 evac_gen = saved_evac_gen;
2963 for (i = 0; i < bco->n_ptrs; i++) {
2964 bcoConstCPtr(bco,i) = evacuate(bcoConstCPtr(bco,i));
2971 scavengeTSO((StgTSO *)p);
2977 StgPAP* pap = (StgPAP *)p;
2979 evac_gen = saved_evac_gen; /* not really mutable */
2980 pap->fun = evacuate(pap->fun);
2981 scavenge_stack((P_)pap->payload, (P_)pap->payload + pap->n_args);
2987 barf("scavenge_large: unknown/strange object");
2992 //@cindex zero_static_object_list
2995 zero_static_object_list(StgClosure* first_static)
2999 const StgInfoTable *info;
3001 for (p = first_static; p != END_OF_STATIC_LIST; p = link) {
3003 link = STATIC_LINK(info, p);
3004 STATIC_LINK(info,p) = NULL;
3008 /* This function is only needed because we share the mutable link
3009 * field with the static link field in an IND_STATIC, so we have to
3010 * zero the mut_link field before doing a major GC, which needs the
3011 * static link field.
3013 * It doesn't do any harm to zero all the mutable link fields on the
3016 //@cindex zero_mutable_list
3019 zero_mutable_list( StgMutClosure *first )
3021 StgMutClosure *next, *c;
3023 for (c = first; c != END_MUT_LIST; c = next) {
3029 //@node Reverting CAFs, Sanity code for CAF garbage collection, Scavenging
3030 //@subsection Reverting CAFs
3032 /* -----------------------------------------------------------------------------
3034 -------------------------------------------------------------------------- */
3035 //@cindex RevertCAFs
3037 void RevertCAFs(void)
3039 while (enteredCAFs != END_CAF_LIST) {
3040 StgCAF* caf = enteredCAFs;
3042 enteredCAFs = caf->link;
3043 ASSERT(get_itbl(caf)->type == CAF_ENTERED);
3044 SET_INFO(caf,&CAF_UNENTERED_info);
3045 caf->value = (StgClosure *)0xdeadbeef;
3046 caf->link = (StgCAF *)0xdeadbeef;
3048 enteredCAFs = END_CAF_LIST;
3051 //@cindex revert_dead_CAFs
3053 void revert_dead_CAFs(void)
3055 StgCAF* caf = enteredCAFs;
3056 enteredCAFs = END_CAF_LIST;
3057 while (caf != END_CAF_LIST) {
3060 new = (StgCAF*)isAlive((StgClosure*)caf);
3062 new->link = enteredCAFs;
3066 SET_INFO(caf,&CAF_UNENTERED_info);
3067 caf->value = (StgClosure*)0xdeadbeef;
3068 caf->link = (StgCAF*)0xdeadbeef;
3074 //@node Sanity code for CAF garbage collection, Lazy black holing, Reverting CAFs
3075 //@subsection Sanity code for CAF garbage collection
3077 /* -----------------------------------------------------------------------------
3078 Sanity code for CAF garbage collection.
3080 With DEBUG turned on, we manage a CAF list in addition to the SRT
3081 mechanism. After GC, we run down the CAF list and blackhole any
3082 CAFs which have been garbage collected. This means we get an error
3083 whenever the program tries to enter a garbage collected CAF.
3085 Any garbage collected CAFs are taken off the CAF list at the same
3087 -------------------------------------------------------------------------- */
3097 const StgInfoTable *info;
3108 ASSERT(info->type == IND_STATIC);
3110 if (STATIC_LINK(info,p) == NULL) {
3111 IF_DEBUG(gccafs, fprintf(stderr, "CAF gc'd at 0x%04x\n", (int)p));
3113 SET_INFO(p,&BLACKHOLE_info);
3114 p = STATIC_LINK2(info,p);
3118 pp = &STATIC_LINK2(info,p);
3125 /* fprintf(stderr, "%d CAFs live\n", i); */
3129 //@node Lazy black holing, Stack squeezing, Sanity code for CAF garbage collection
3130 //@subsection Lazy black holing
3132 /* -----------------------------------------------------------------------------
3135 Whenever a thread returns to the scheduler after possibly doing
3136 some work, we have to run down the stack and black-hole all the
3137 closures referred to by update frames.
3138 -------------------------------------------------------------------------- */
3139 //@cindex threadLazyBlackHole
3142 threadLazyBlackHole(StgTSO *tso)
3144 StgUpdateFrame *update_frame;
3145 StgBlockingQueue *bh;
3148 stack_end = &tso->stack[tso->stack_size];
3149 update_frame = tso->su;
3152 switch (get_itbl(update_frame)->type) {
3155 update_frame = ((StgCatchFrame *)update_frame)->link;
3159 bh = (StgBlockingQueue *)update_frame->updatee;
3161 /* if the thunk is already blackholed, it means we've also
3162 * already blackholed the rest of the thunks on this stack,
3163 * so we can stop early.
3165 * The blackhole made for a CAF is a CAF_BLACKHOLE, so they
3166 * don't interfere with this optimisation.
3168 if (bh->header.info == &BLACKHOLE_info) {
3172 if (bh->header.info != &BLACKHOLE_BQ_info &&
3173 bh->header.info != &CAF_BLACKHOLE_info) {
3174 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
3175 fprintf(stderr,"Unexpected lazy BHing required at 0x%04x\n",(int)bh);
3177 SET_INFO(bh,&BLACKHOLE_info);
3180 update_frame = update_frame->link;
3184 update_frame = ((StgSeqFrame *)update_frame)->link;
3190 barf("threadPaused");
3195 //@node Stack squeezing, Pausing a thread, Lazy black holing
3196 //@subsection Stack squeezing
3198 /* -----------------------------------------------------------------------------
3201 * Code largely pinched from old RTS, then hacked to bits. We also do
3202 * lazy black holing here.
3204 * -------------------------------------------------------------------------- */
3205 //@cindex threadSqueezeStack
3208 threadSqueezeStack(StgTSO *tso)
3210 lnat displacement = 0;
3211 StgUpdateFrame *frame;
3212 StgUpdateFrame *next_frame; /* Temporally next */
3213 StgUpdateFrame *prev_frame; /* Temporally previous */
3215 rtsBool prev_was_update_frame;
3217 StgUpdateFrame *top_frame;
3218 nat upd_frames=0, stop_frames=0, catch_frames=0, seq_frames=0,
3220 void printObj( StgClosure *obj ); // from Printer.c
3222 top_frame = tso->su;
3225 bottom = &(tso->stack[tso->stack_size]);
3228 /* There must be at least one frame, namely the STOP_FRAME.
3230 ASSERT((P_)frame < bottom);
3232 /* Walk down the stack, reversing the links between frames so that
3233 * we can walk back up as we squeeze from the bottom. Note that
3234 * next_frame and prev_frame refer to next and previous as they were
3235 * added to the stack, rather than the way we see them in this
3236 * walk. (It makes the next loop less confusing.)
3238 * Stop if we find an update frame pointing to a black hole
3239 * (see comment in threadLazyBlackHole()).
3243 /* bottom - sizeof(StgStopFrame) is the STOP_FRAME */
3244 while ((P_)frame < bottom - sizeofW(StgStopFrame)) {
3245 prev_frame = frame->link;
3246 frame->link = next_frame;
3251 if (!(frame>=top_frame && frame<=(StgUpdateFrame *)bottom)) {
3252 printObj((StgClosure *)prev_frame);
3253 barf("threadSqueezeStack: current frame is rubbish %p; previous was %p\n",
3256 switch (get_itbl(frame)->type) {
3257 case UPDATE_FRAME: upd_frames++;
3258 if (frame->updatee->header.info == &BLACKHOLE_info)
3261 case STOP_FRAME: stop_frames++;
3263 case CATCH_FRAME: catch_frames++;
3265 case SEQ_FRAME: seq_frames++;
3268 barf("Found non-frame during stack squeezing at %p (prev frame was %p)\n",
3270 printObj((StgClosure *)prev_frame);
3273 if (get_itbl(frame)->type == UPDATE_FRAME
3274 && frame->updatee->header.info == &BLACKHOLE_info) {
3279 /* Now, we're at the bottom. Frame points to the lowest update
3280 * frame on the stack, and its link actually points to the frame
3281 * above. We have to walk back up the stack, squeezing out empty
3282 * update frames and turning the pointers back around on the way
3285 * The bottom-most frame (the STOP_FRAME) has not been altered, and
3286 * we never want to eliminate it anyway. Just walk one step up
3287 * before starting to squeeze. When you get to the topmost frame,
3288 * remember that there are still some words above it that might have
3295 prev_was_update_frame = (get_itbl(prev_frame)->type == UPDATE_FRAME);
3298 * Loop through all of the frames (everything except the very
3299 * bottom). Things are complicated by the fact that we have
3300 * CATCH_FRAMEs and SEQ_FRAMEs interspersed with the update frames.
3301 * We can only squeeze when there are two consecutive UPDATE_FRAMEs.
3303 while (frame != NULL) {
3305 StgPtr frame_bottom = (P_)frame + sizeofW(StgUpdateFrame);
3306 rtsBool is_update_frame;
3308 next_frame = frame->link;
3309 is_update_frame = (get_itbl(frame)->type == UPDATE_FRAME);
3312 * 1. both the previous and current frame are update frames
3313 * 2. the current frame is empty
3315 if (prev_was_update_frame && is_update_frame &&
3316 (P_)prev_frame == frame_bottom + displacement) {
3318 /* Now squeeze out the current frame */
3319 StgClosure *updatee_keep = prev_frame->updatee;
3320 StgClosure *updatee_bypass = frame->updatee;
3323 IF_DEBUG(gc, fprintf(stderr, "@@ squeezing frame at %p\n", frame));
3327 /* Deal with blocking queues. If both updatees have blocked
3328 * threads, then we should merge the queues into the update
3329 * frame that we're keeping.
3331 * Alternatively, we could just wake them up: they'll just go
3332 * straight to sleep on the proper blackhole! This is less code
3333 * and probably less bug prone, although it's probably much
3336 #if 0 /* do it properly... */
3337 # if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
3338 # error Unimplemented lazy BH warning. (KSW 1999-01)
3340 if (GET_INFO(updatee_bypass) == BLACKHOLE_BQ_info
3341 || GET_INFO(updatee_bypass) == CAF_BLACKHOLE_info
3343 /* Sigh. It has one. Don't lose those threads! */
3344 if (GET_INFO(updatee_keep) == BLACKHOLE_BQ_info) {
3345 /* Urgh. Two queues. Merge them. */
3346 P_ keep_tso = ((StgBlockingQueue *)updatee_keep)->blocking_queue;
3348 while (keep_tso->link != END_TSO_QUEUE) {
3349 keep_tso = keep_tso->link;
3351 keep_tso->link = ((StgBlockingQueue *)updatee_bypass)->blocking_queue;
3354 /* For simplicity, just swap the BQ for the BH */
3355 P_ temp = updatee_keep;
3357 updatee_keep = updatee_bypass;
3358 updatee_bypass = temp;
3360 /* Record the swap in the kept frame (below) */
3361 prev_frame->updatee = updatee_keep;
3366 TICK_UPD_SQUEEZED();
3367 /* wasn't there something about update squeezing and ticky to be
3368 * sorted out? oh yes: we aren't counting each enter properly
3369 * in this case. See the log somewhere. KSW 1999-04-21
3371 UPD_IND_NOLOCK(updatee_bypass, updatee_keep); /* this wakes the threads up */
3373 sp = (P_)frame - 1; /* sp = stuff to slide */
3374 displacement += sizeofW(StgUpdateFrame);
3377 /* No squeeze for this frame */
3378 sp = frame_bottom - 1; /* Keep the current frame */
3380 /* Do lazy black-holing.
3382 if (is_update_frame) {
3383 StgBlockingQueue *bh = (StgBlockingQueue *)frame->updatee;
3384 if (bh->header.info != &BLACKHOLE_info &&
3385 bh->header.info != &BLACKHOLE_BQ_info &&
3386 bh->header.info != &CAF_BLACKHOLE_info) {
3387 #if (!defined(LAZY_BLACKHOLING)) && defined(DEBUG)
3388 fprintf(stderr,"Unexpected lazy BHing required at 0x%04x\n",(int)bh);
3390 SET_INFO(bh,&BLACKHOLE_info);
3394 /* Fix the link in the current frame (should point to the frame below) */
3395 frame->link = prev_frame;
3396 prev_was_update_frame = is_update_frame;
3399 /* Now slide all words from sp up to the next frame */
3401 if (displacement > 0) {
3402 P_ next_frame_bottom;
3404 if (next_frame != NULL)
3405 next_frame_bottom = (P_)next_frame + sizeofW(StgUpdateFrame);
3407 next_frame_bottom = tso->sp - 1;
3411 fprintf(stderr, "sliding [%p, %p] by %ld\n", sp, next_frame_bottom,
3415 while (sp >= next_frame_bottom) {
3416 sp[displacement] = *sp;
3420 (P_)prev_frame = (P_)frame + displacement;
3424 tso->sp += displacement;
3425 tso->su = prev_frame;
3428 fprintf(stderr, "@@ threadSqueezeStack: squeezed %d update-frames; found %d BHs; found %d update-, %d stop-, %d catch, %d seq-frames\n",
3429 squeezes, bhs, upd_frames, stop_frames, catch_frames, seq_frames))
3433 //@node Pausing a thread, Index, Stack squeezing
3434 //@subsection Pausing a thread
3436 /* -----------------------------------------------------------------------------
3439 * We have to prepare for GC - this means doing lazy black holing
3440 * here. We also take the opportunity to do stack squeezing if it's
3442 * -------------------------------------------------------------------------- */
3443 //@cindex threadPaused
3446 threadPaused(StgTSO *tso)
3448 if ( RtsFlags.GcFlags.squeezeUpdFrames == rtsTrue )
3449 threadSqueezeStack(tso); /* does black holing too */
3451 threadLazyBlackHole(tso);
3454 /* -----------------------------------------------------------------------------
3456 * -------------------------------------------------------------------------- */
3459 //@cindex printMutOnceList
3461 printMutOnceList(generation *gen)
3463 StgMutClosure *p, *next;
3465 p = gen->mut_once_list;
3468 fprintf(stderr, "@@ Mut once list %p: ", gen->mut_once_list);
3469 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
3470 fprintf(stderr, "%p (%s), ",
3471 p, info_type((StgClosure *)p));
3473 fputc('\n', stderr);
3476 //@cindex printMutableList
3478 printMutableList(generation *gen)
3480 StgMutClosure *p, *next;
3482 p = gen->saved_mut_list;
3485 fprintf(stderr, "@@ Mutable list %p: ", gen->saved_mut_list);
3486 for (; p != END_MUT_LIST; p = next, next = p->mut_link) {
3487 fprintf(stderr, "%p (%s), ",
3488 p, info_type((StgClosure *)p));
3490 fputc('\n', stderr);
3494 //@node Index, , Pausing a thread
3498 //* GarbageCollect:: @cindex\s-+GarbageCollect
3499 //* MarkRoot:: @cindex\s-+MarkRoot
3500 //* RevertCAFs:: @cindex\s-+RevertCAFs
3501 //* addBlock:: @cindex\s-+addBlock
3502 //* cleanup_weak_ptr_list:: @cindex\s-+cleanup_weak_ptr_list
3503 //* copy:: @cindex\s-+copy
3504 //* copyPart:: @cindex\s-+copyPart
3505 //* evacuate:: @cindex\s-+evacuate
3506 //* evacuate_large:: @cindex\s-+evacuate_large
3507 //* gcCAFs:: @cindex\s-+gcCAFs
3508 //* isAlive:: @cindex\s-+isAlive
3509 //* mkMutCons:: @cindex\s-+mkMutCons
3510 //* relocate_TSO:: @cindex\s-+relocate_TSO
3511 //* revert_dead_CAFs:: @cindex\s-+revert_dead_CAFs
3512 //* scavenge:: @cindex\s-+scavenge
3513 //* scavenge_large:: @cindex\s-+scavenge_large
3514 //* scavenge_mut_once_list:: @cindex\s-+scavenge_mut_once_list
3515 //* scavenge_mutable_list:: @cindex\s-+scavenge_mutable_list
3516 //* scavenge_one:: @cindex\s-+scavenge_one
3517 //* scavenge_srt:: @cindex\s-+scavenge_srt
3518 //* scavenge_stack:: @cindex\s-+scavenge_stack
3519 //* scavenge_static:: @cindex\s-+scavenge_static
3520 //* threadLazyBlackHole:: @cindex\s-+threadLazyBlackHole
3521 //* threadPaused:: @cindex\s-+threadPaused
3522 //* threadSqueezeStack:: @cindex\s-+threadSqueezeStack
3523 //* traverse_weak_ptr_list:: @cindex\s-+traverse_weak_ptr_list
3524 //* upd_evacuee:: @cindex\s-+upd_evacuee
3525 //* zero_mutable_list:: @cindex\s-+zero_mutable_list
3526 //* zero_static_object_list:: @cindex\s-+zero_static_object_list