1 /* -----------------------------------------------------------------------------
3 * (c) The GHC Team, 1998-2006
5 * Storage manager front end
7 * Documentation on the architecture of the Storage Manager can be
8 * found in the online commentary:
10 * http://hackage.haskell.org/trac/ghc/wiki/Commentary/Rts/Storage
12 * ---------------------------------------------------------------------------*/
14 #include "PosixSource.h"
20 #include "BlockAlloc.h"
25 #include "OSThreads.h"
26 #include "Capability.h"
29 #include "RetainerProfile.h" // for counting memory blocks (memInventory)
37 * All these globals require sm_mutex to access in THREADED_RTS mode.
39 StgClosure *caf_list = NULL;
40 StgClosure *revertible_caf_list = NULL;
43 bdescr *pinned_object_block; /* allocate pinned objects into this block */
44 nat alloc_blocks; /* number of allocate()d blocks since GC */
45 nat alloc_blocks_lim; /* approximate limit on alloc_blocks */
47 generation *generations = NULL; /* all the generations */
48 generation *g0 = NULL; /* generation 0, for convenience */
49 generation *oldest_gen = NULL; /* oldest generation, for convenience */
50 step *g0s0 = NULL; /* generation 0, step 0, for convenience */
52 ullong total_allocated = 0; /* total memory allocated during run */
54 nat n_nurseries = 0; /* == RtsFlags.ParFlags.nNodes, convenience */
55 step *nurseries = NULL; /* array of nurseries, >1 only if THREADED_RTS */
59 * Storage manager mutex: protects all the above state from
60 * simultaneous access by two STG threads.
64 * This mutex is used by atomicModifyMutVar# only
66 Mutex atomic_modify_mutvar_mutex;
73 static void *stgAllocForGMP (size_t size_in_bytes);
74 static void *stgReallocForGMP (void *ptr, size_t old_size, size_t new_size);
75 static void stgDeallocForGMP (void *ptr, size_t size);
78 initStep (step *stp, int g, int s)
83 stp->old_blocks = NULL;
84 stp->n_old_blocks = 0;
85 stp->gen = &generations[g];
91 stp->scavd_hpLim = NULL;
94 stp->large_objects = NULL;
95 stp->n_large_blocks = 0;
96 stp->new_large_objects = NULL;
97 stp->scavenged_large_objects = NULL;
98 stp->n_scavenged_large_blocks = 0;
99 stp->is_compacted = 0;
109 if (generations != NULL) {
110 // multi-init protection
116 /* Sanity check to make sure the LOOKS_LIKE_ macros appear to be
117 * doing something reasonable.
119 ASSERT(LOOKS_LIKE_INFO_PTR(&stg_BLACKHOLE_info));
120 ASSERT(LOOKS_LIKE_CLOSURE_PTR(&stg_dummy_ret_closure));
121 ASSERT(!HEAP_ALLOCED(&stg_dummy_ret_closure));
123 if (RtsFlags.GcFlags.maxHeapSize != 0 &&
124 RtsFlags.GcFlags.heapSizeSuggestion >
125 RtsFlags.GcFlags.maxHeapSize) {
126 RtsFlags.GcFlags.maxHeapSize = RtsFlags.GcFlags.heapSizeSuggestion;
129 if (RtsFlags.GcFlags.maxHeapSize != 0 &&
130 RtsFlags.GcFlags.minAllocAreaSize >
131 RtsFlags.GcFlags.maxHeapSize) {
132 errorBelch("maximum heap size (-M) is smaller than minimum alloc area size (-A)");
133 RtsFlags.GcFlags.minAllocAreaSize = RtsFlags.GcFlags.maxHeapSize;
136 initBlockAllocator();
138 #if defined(THREADED_RTS)
139 initMutex(&sm_mutex);
140 initMutex(&atomic_modify_mutvar_mutex);
145 /* allocate generation info array */
146 generations = (generation *)stgMallocBytes(RtsFlags.GcFlags.generations
147 * sizeof(struct generation_),
148 "initStorage: gens");
150 /* Initialise all generations */
151 for(g = 0; g < RtsFlags.GcFlags.generations; g++) {
152 gen = &generations[g];
154 gen->mut_list = allocBlock();
155 gen->collections = 0;
156 gen->failed_promotions = 0;
160 /* A couple of convenience pointers */
161 g0 = &generations[0];
162 oldest_gen = &generations[RtsFlags.GcFlags.generations-1];
164 /* Allocate step structures in each generation */
165 if (RtsFlags.GcFlags.generations > 1) {
166 /* Only for multiple-generations */
168 /* Oldest generation: one step */
169 oldest_gen->n_steps = 1;
171 stgMallocBytes(1 * sizeof(struct step_), "initStorage: last step");
173 /* set up all except the oldest generation with 2 steps */
174 for(g = 0; g < RtsFlags.GcFlags.generations-1; g++) {
175 generations[g].n_steps = RtsFlags.GcFlags.steps;
176 generations[g].steps =
177 stgMallocBytes (RtsFlags.GcFlags.steps * sizeof(struct step_),
178 "initStorage: steps");
182 /* single generation, i.e. a two-space collector */
184 g0->steps = stgMallocBytes (sizeof(struct step_), "initStorage: steps");
188 n_nurseries = n_capabilities;
192 nurseries = stgMallocBytes (n_nurseries * sizeof(struct step_),
193 "initStorage: nurseries");
195 /* Initialise all steps */
196 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
197 for (s = 0; s < generations[g].n_steps; s++) {
198 initStep(&generations[g].steps[s], g, s);
202 for (s = 0; s < n_nurseries; s++) {
203 initStep(&nurseries[s], 0, s);
206 /* Set up the destination pointers in each younger gen. step */
207 for (g = 0; g < RtsFlags.GcFlags.generations-1; g++) {
208 for (s = 0; s < generations[g].n_steps-1; s++) {
209 generations[g].steps[s].to = &generations[g].steps[s+1];
211 generations[g].steps[s].to = &generations[g+1].steps[0];
213 oldest_gen->steps[0].to = &oldest_gen->steps[0];
215 for (s = 0; s < n_nurseries; s++) {
216 nurseries[s].to = generations[0].steps[0].to;
219 /* The oldest generation has one step. */
220 if (RtsFlags.GcFlags.compact) {
221 if (RtsFlags.GcFlags.generations == 1) {
222 errorBelch("WARNING: compaction is incompatible with -G1; disabled");
224 oldest_gen->steps[0].is_compacted = 1;
228 generations[0].max_blocks = 0;
229 g0s0 = &generations[0].steps[0];
231 /* The allocation area. Policy: keep the allocation area
232 * small to begin with, even if we have a large suggested heap
233 * size. Reason: we're going to do a major collection first, and we
234 * don't want it to be a big one. This vague idea is borne out by
235 * rigorous experimental evidence.
239 weak_ptr_list = NULL;
241 revertible_caf_list = NULL;
243 /* initialise the allocate() interface */
245 alloc_blocks_lim = RtsFlags.GcFlags.minAllocAreaSize;
247 /* Tell GNU multi-precision pkg about our custom alloc functions */
248 mp_set_memory_functions(stgAllocForGMP, stgReallocForGMP, stgDeallocForGMP);
250 IF_DEBUG(gc, statDescribeGens());
258 stat_exit(calcAllocated());
266 for(g = 0; g < RtsFlags.GcFlags.generations; g++)
267 stgFree(generations[g].steps);
268 stgFree(generations);
270 #if defined(THREADED_RTS)
271 closeMutex(&sm_mutex);
272 closeMutex(&atomic_modify_mutvar_mutex);
277 /* -----------------------------------------------------------------------------
280 The entry code for every CAF does the following:
282 - builds a CAF_BLACKHOLE in the heap
283 - pushes an update frame pointing to the CAF_BLACKHOLE
284 - invokes UPD_CAF(), which:
285 - calls newCaf, below
286 - updates the CAF with a static indirection to the CAF_BLACKHOLE
288 Why do we build a BLACKHOLE in the heap rather than just updating
289 the thunk directly? It's so that we only need one kind of update
290 frame - otherwise we'd need a static version of the update frame too.
292 newCaf() does the following:
294 - it puts the CAF on the oldest generation's mut-once list.
295 This is so that we can treat the CAF as a root when collecting
298 For GHCI, we have additional requirements when dealing with CAFs:
300 - we must *retain* all dynamically-loaded CAFs ever entered,
301 just in case we need them again.
302 - we must be able to *revert* CAFs that have been evaluated, to
303 their pre-evaluated form.
305 To do this, we use an additional CAF list. When newCaf() is
306 called on a dynamically-loaded CAF, we add it to the CAF list
307 instead of the old-generation mutable list, and save away its
308 old info pointer (in caf->saved_info) for later reversion.
310 To revert all the CAFs, we traverse the CAF list and reset the
311 info pointer to caf->saved_info, then throw away the CAF list.
312 (see GC.c:revertCAFs()).
316 -------------------------------------------------------------------------- */
319 newCAF(StgClosure* caf)
326 // If we are in GHCi _and_ we are using dynamic libraries,
327 // then we can't redirect newCAF calls to newDynCAF (see below),
328 // so we make newCAF behave almost like newDynCAF.
329 // The dynamic libraries might be used by both the interpreted
330 // program and GHCi itself, so they must not be reverted.
331 // This also means that in GHCi with dynamic libraries, CAFs are not
332 // garbage collected. If this turns out to be a problem, we could
333 // do another hack here and do an address range test on caf to figure
334 // out whether it is from a dynamic library.
335 ((StgIndStatic *)caf)->saved_info = (StgInfoTable *)caf->header.info;
336 ((StgIndStatic *)caf)->static_link = caf_list;
341 /* Put this CAF on the mutable list for the old generation.
342 * This is a HACK - the IND_STATIC closure doesn't really have
343 * a mut_link field, but we pretend it has - in fact we re-use
344 * the STATIC_LINK field for the time being, because when we
345 * come to do a major GC we won't need the mut_link field
346 * any more and can use it as a STATIC_LINK.
348 ((StgIndStatic *)caf)->saved_info = NULL;
349 recordMutableGen(caf, oldest_gen);
355 // An alternate version of newCaf which is used for dynamically loaded
356 // object code in GHCi. In this case we want to retain *all* CAFs in
357 // the object code, because they might be demanded at any time from an
358 // expression evaluated on the command line.
359 // Also, GHCi might want to revert CAFs, so we add these to the
360 // revertible_caf_list.
362 // The linker hackily arranges that references to newCaf from dynamic
363 // code end up pointing to newDynCAF.
365 newDynCAF(StgClosure *caf)
369 ((StgIndStatic *)caf)->saved_info = (StgInfoTable *)caf->header.info;
370 ((StgIndStatic *)caf)->static_link = revertible_caf_list;
371 revertible_caf_list = caf;
376 /* -----------------------------------------------------------------------------
378 -------------------------------------------------------------------------- */
381 allocNursery (step *stp, bdescr *tail, nat blocks)
386 // Allocate a nursery: we allocate fresh blocks one at a time and
387 // cons them on to the front of the list, not forgetting to update
388 // the back pointer on the tail of the list to point to the new block.
389 for (i=0; i < blocks; i++) {
392 processNursery() in LdvProfile.c assumes that every block group in
393 the nursery contains only a single block. So, if a block group is
394 given multiple blocks, change processNursery() accordingly.
398 // double-link the nursery: we might need to insert blocks
405 bd->free = bd->start;
413 assignNurseriesToCapabilities (void)
418 for (i = 0; i < n_nurseries; i++) {
419 capabilities[i].r.rNursery = &nurseries[i];
420 capabilities[i].r.rCurrentNursery = nurseries[i].blocks;
421 capabilities[i].r.rCurrentAlloc = NULL;
423 #else /* THREADED_RTS */
424 MainCapability.r.rNursery = &nurseries[0];
425 MainCapability.r.rCurrentNursery = nurseries[0].blocks;
426 MainCapability.r.rCurrentAlloc = NULL;
431 allocNurseries( void )
435 for (i = 0; i < n_nurseries; i++) {
436 nurseries[i].blocks =
437 allocNursery(&nurseries[i], NULL,
438 RtsFlags.GcFlags.minAllocAreaSize);
439 nurseries[i].n_blocks = RtsFlags.GcFlags.minAllocAreaSize;
440 nurseries[i].old_blocks = NULL;
441 nurseries[i].n_old_blocks = 0;
443 assignNurseriesToCapabilities();
447 resetNurseries( void )
453 for (i = 0; i < n_nurseries; i++) {
455 for (bd = stp->blocks; bd; bd = bd->link) {
456 bd->free = bd->start;
457 ASSERT(bd->gen_no == 0);
458 ASSERT(bd->step == stp);
459 IF_DEBUG(sanity,memset(bd->start, 0xaa, BLOCK_SIZE));
462 assignNurseriesToCapabilities();
466 countNurseryBlocks (void)
471 for (i = 0; i < n_nurseries; i++) {
472 blocks += nurseries[i].n_blocks;
478 resizeNursery ( step *stp, nat blocks )
483 nursery_blocks = stp->n_blocks;
484 if (nursery_blocks == blocks) return;
486 if (nursery_blocks < blocks) {
487 debugTrace(DEBUG_gc, "increasing size of nursery to %d blocks",
489 stp->blocks = allocNursery(stp, stp->blocks, blocks-nursery_blocks);
494 debugTrace(DEBUG_gc, "decreasing size of nursery to %d blocks",
498 while (nursery_blocks > blocks) {
500 next_bd->u.back = NULL;
501 nursery_blocks -= bd->blocks; // might be a large block
506 // might have gone just under, by freeing a large block, so make
507 // up the difference.
508 if (nursery_blocks < blocks) {
509 stp->blocks = allocNursery(stp, stp->blocks, blocks-nursery_blocks);
513 stp->n_blocks = blocks;
514 ASSERT(countBlocks(stp->blocks) == stp->n_blocks);
518 // Resize each of the nurseries to the specified size.
521 resizeNurseriesFixed (nat blocks)
524 for (i = 0; i < n_nurseries; i++) {
525 resizeNursery(&nurseries[i], blocks);
530 // Resize the nurseries to the total specified size.
533 resizeNurseries (nat blocks)
535 // If there are multiple nurseries, then we just divide the number
536 // of available blocks between them.
537 resizeNurseriesFixed(blocks / n_nurseries);
540 /* -----------------------------------------------------------------------------
541 The allocate() interface
543 allocateInGen() function allocates memory directly into a specific
544 generation. It always succeeds, and returns a chunk of memory n
545 words long. n can be larger than the size of a block if necessary,
546 in which case a contiguous block group will be allocated.
548 allocate(n) is equivalent to allocateInGen(g0).
549 -------------------------------------------------------------------------- */
552 allocateInGen (generation *g, nat n)
560 TICK_ALLOC_HEAP_NOCTR(n);
565 if (n >= LARGE_OBJECT_THRESHOLD/sizeof(W_))
567 nat req_blocks = (lnat)BLOCK_ROUND_UP(n*sizeof(W_)) / BLOCK_SIZE;
568 bd = allocGroup(req_blocks);
569 dbl_link_onto(bd, &stp->large_objects);
570 stp->n_large_blocks += bd->blocks; // might be larger than req_blocks
573 bd->flags = BF_LARGE;
574 bd->free = bd->start + n;
579 // small allocation (<LARGE_OBJECT_THRESHOLD) */
581 if (bd == NULL || bd->free + n > bd->start + BLOCK_SIZE_W) {
586 bd->link = stp->blocks;
603 return allocateInGen(g0,n);
607 allocatedBytes( void )
611 allocated = alloc_blocks * BLOCK_SIZE_W;
612 if (pinned_object_block != NULL) {
613 allocated -= (pinned_object_block->start + BLOCK_SIZE_W) -
614 pinned_object_block->free;
620 /* -----------------------------------------------------------------------------
623 This allocates memory in the current thread - it is intended for
624 use primarily from STG-land where we have a Capability. It is
625 better than allocate() because it doesn't require taking the
626 sm_mutex lock in the common case.
628 Memory is allocated directly from the nursery if possible (but not
629 from the current nursery block, so as not to interfere with
631 -------------------------------------------------------------------------- */
634 allocateLocal (Capability *cap, nat n)
639 if (n >= LARGE_OBJECT_THRESHOLD/sizeof(W_)) {
640 return allocateInGen(g0,n);
643 /* small allocation (<LARGE_OBJECT_THRESHOLD) */
645 TICK_ALLOC_HEAP_NOCTR(n);
648 bd = cap->r.rCurrentAlloc;
649 if (bd == NULL || bd->free + n > bd->start + BLOCK_SIZE_W) {
651 // The CurrentAlloc block is full, we need to find another
652 // one. First, we try taking the next block from the
654 bd = cap->r.rCurrentNursery->link;
656 if (bd == NULL || bd->free + n > bd->start + BLOCK_SIZE_W) {
657 // The nursery is empty, or the next block is already
658 // full: allocate a fresh block (we can't fail here).
661 cap->r.rNursery->n_blocks++;
664 bd->step = cap->r.rNursery;
668 // we have a block in the nursery: take it and put
669 // it at the *front* of the nursery list, and use it
670 // to allocate() from.
671 cap->r.rCurrentNursery->link = bd->link;
672 if (bd->link != NULL) {
673 bd->link->u.back = cap->r.rCurrentNursery;
676 dbl_link_onto(bd, &cap->r.rNursery->blocks);
677 cap->r.rCurrentAlloc = bd;
678 IF_DEBUG(sanity, checkNurserySanity(cap->r.rNursery));
685 /* ---------------------------------------------------------------------------
686 Allocate a fixed/pinned object.
688 We allocate small pinned objects into a single block, allocating a
689 new block when the current one overflows. The block is chained
690 onto the large_object_list of generation 0 step 0.
692 NOTE: The GC can't in general handle pinned objects. This
693 interface is only safe to use for ByteArrays, which have no
694 pointers and don't require scavenging. It works because the
695 block's descriptor has the BF_LARGE flag set, so the block is
696 treated as a large object and chained onto various lists, rather
697 than the individual objects being copied. However, when it comes
698 to scavenge the block, the GC will only scavenge the first object.
699 The reason is that the GC can't linearly scan a block of pinned
700 objects at the moment (doing so would require using the
701 mostly-copying techniques). But since we're restricting ourselves
702 to pinned ByteArrays, not scavenging is ok.
704 This function is called by newPinnedByteArray# which immediately
705 fills the allocated memory with a MutableByteArray#.
706 ------------------------------------------------------------------------- */
709 allocatePinned( nat n )
712 bdescr *bd = pinned_object_block;
714 // If the request is for a large object, then allocate()
715 // will give us a pinned object anyway.
716 if (n >= LARGE_OBJECT_THRESHOLD/sizeof(W_)) {
722 TICK_ALLOC_HEAP_NOCTR(n);
725 // we always return 8-byte aligned memory. bd->free must be
726 // 8-byte aligned to begin with, so we just round up n to
727 // the nearest multiple of 8 bytes.
728 if (sizeof(StgWord) == 4) {
732 // If we don't have a block of pinned objects yet, or the current
733 // one isn't large enough to hold the new object, allocate a new one.
734 if (bd == NULL || (bd->free + n) > (bd->start + BLOCK_SIZE_W)) {
735 pinned_object_block = bd = allocBlock();
736 dbl_link_onto(bd, &g0s0->large_objects);
737 g0s0->n_large_blocks++;
740 bd->flags = BF_PINNED | BF_LARGE;
741 bd->free = bd->start;
751 /* -----------------------------------------------------------------------------
753 -------------------------------------------------------------------------- */
756 This is the write barrier for MUT_VARs, a.k.a. IORefs. A
757 MUT_VAR_CLEAN object is not on the mutable list; a MUT_VAR_DIRTY
758 is. When written to, a MUT_VAR_CLEAN turns into a MUT_VAR_DIRTY
759 and is put on the mutable list.
762 dirty_MUT_VAR(StgRegTable *reg, StgClosure *p)
764 Capability *cap = regTableToCapability(reg);
766 if (p->header.info == &stg_MUT_VAR_CLEAN_info) {
767 p->header.info = &stg_MUT_VAR_DIRTY_info;
768 bd = Bdescr((StgPtr)p);
769 if (bd->gen_no > 0) recordMutableCap(p,cap,bd->gen_no);
774 This is the write barrier for MVARs. An MVAR_CLEAN objects is not
775 on the mutable list; a MVAR_DIRTY is. When written to, a
776 MVAR_CLEAN turns into a MVAR_DIRTY and is put on the mutable list.
777 The check for MVAR_CLEAN is inlined at the call site for speed,
778 this really does make a difference on concurrency-heavy benchmarks
779 such as Chaneneos and cheap-concurrency.
782 dirty_MVAR(StgRegTable *reg, StgClosure *p)
784 Capability *cap = regTableToCapability(reg);
786 bd = Bdescr((StgPtr)p);
787 if (bd->gen_no > 0) recordMutableCap(p,cap,bd->gen_no);
790 /* -----------------------------------------------------------------------------
791 Allocation functions for GMP.
793 These all use the allocate() interface - we can't have any garbage
794 collection going on during a gmp operation, so we use allocate()
795 which always succeeds. The gmp operations which might need to
796 allocate will ask the storage manager (via doYouWantToGC()) whether
797 a garbage collection is required, in case we get into a loop doing
798 only allocate() style allocation.
799 -------------------------------------------------------------------------- */
802 stgAllocForGMP (size_t size_in_bytes)
805 nat data_size_in_words, total_size_in_words;
807 /* round up to a whole number of words */
808 data_size_in_words = (size_in_bytes + sizeof(W_) + 1) / sizeof(W_);
809 total_size_in_words = sizeofW(StgArrWords) + data_size_in_words;
811 /* allocate and fill it in. */
812 #if defined(THREADED_RTS)
813 arr = (StgArrWords *)allocateLocal(myTask()->cap, total_size_in_words);
815 arr = (StgArrWords *)allocateLocal(&MainCapability, total_size_in_words);
817 SET_ARR_HDR(arr, &stg_ARR_WORDS_info, CCCS, data_size_in_words);
819 /* and return a ptr to the goods inside the array */
824 stgReallocForGMP (void *ptr, size_t old_size, size_t new_size)
826 void *new_stuff_ptr = stgAllocForGMP(new_size);
828 char *p = (char *) ptr;
829 char *q = (char *) new_stuff_ptr;
831 for (; i < old_size; i++, p++, q++) {
835 return(new_stuff_ptr);
839 stgDeallocForGMP (void *ptr STG_UNUSED,
840 size_t size STG_UNUSED)
842 /* easy for us: the garbage collector does the dealloc'n */
845 /* -----------------------------------------------------------------------------
847 * -------------------------------------------------------------------------- */
849 /* -----------------------------------------------------------------------------
852 * Approximate how much we've allocated: number of blocks in the
853 * nursery + blocks allocated via allocate() - unused nusery blocks.
854 * This leaves a little slop at the end of each block, and doesn't
855 * take into account large objects (ToDo).
856 * -------------------------------------------------------------------------- */
859 calcAllocated( void )
864 allocated = allocatedBytes();
865 allocated += countNurseryBlocks() * BLOCK_SIZE_W;
870 for (i = 0; i < n_nurseries; i++) {
872 for ( bd = capabilities[i].r.rCurrentNursery->link;
873 bd != NULL; bd = bd->link ) {
874 allocated -= BLOCK_SIZE_W;
876 cap = &capabilities[i];
877 if (cap->r.rCurrentNursery->free <
878 cap->r.rCurrentNursery->start + BLOCK_SIZE_W) {
879 allocated -= (cap->r.rCurrentNursery->start + BLOCK_SIZE_W)
880 - cap->r.rCurrentNursery->free;
884 bdescr *current_nursery = MainCapability.r.rCurrentNursery;
886 for ( bd = current_nursery->link; bd != NULL; bd = bd->link ) {
887 allocated -= BLOCK_SIZE_W;
889 if (current_nursery->free < current_nursery->start + BLOCK_SIZE_W) {
890 allocated -= (current_nursery->start + BLOCK_SIZE_W)
891 - current_nursery->free;
896 total_allocated += allocated;
900 /* Approximate the amount of live data in the heap. To be called just
901 * after garbage collection (see GarbageCollect()).
910 if (RtsFlags.GcFlags.generations == 1) {
911 return (g0s0->n_large_blocks + g0s0->n_blocks) * BLOCK_SIZE_W;
914 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
915 for (s = 0; s < generations[g].n_steps; s++) {
916 /* approximate amount of live data (doesn't take into account slop
917 * at end of each block).
919 if (g == 0 && s == 0) {
922 stp = &generations[g].steps[s];
923 live += (stp->n_large_blocks + stp->n_blocks) * BLOCK_SIZE_W;
929 /* Approximate the number of blocks that will be needed at the next
930 * garbage collection.
932 * Assume: all data currently live will remain live. Steps that will
933 * be collected next time will therefore need twice as many blocks
934 * since all the data will be copied.
943 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
944 for (s = 0; s < generations[g].n_steps; s++) {
945 if (g == 0 && s == 0) { continue; }
946 stp = &generations[g].steps[s];
947 if (generations[g].steps[0].n_blocks +
948 generations[g].steps[0].n_large_blocks
949 > generations[g].max_blocks
950 && stp->is_compacted == 0) {
951 needed += 2 * stp->n_blocks;
953 needed += stp->n_blocks;
960 /* ----------------------------------------------------------------------------
963 Executable memory must be managed separately from non-executable
964 memory. Most OSs these days require you to jump through hoops to
965 dynamically allocate executable memory, due to various security
968 Here we provide a small memory allocator for executable memory.
969 Memory is managed with a page granularity; we allocate linearly
970 in the page, and when the page is emptied (all objects on the page
971 are free) we free the page again, not forgetting to make it
974 TODO: The inability to handle objects bigger than BLOCK_SIZE_W means that
975 the linker cannot use allocateExec for loading object code files
976 on Windows. Once allocateExec can handle larger objects, the linker
977 should be modified to use allocateExec instead of VirtualAlloc.
978 ------------------------------------------------------------------------- */
980 static bdescr *exec_block;
982 void *allocateExec (nat bytes)
989 // round up to words.
990 n = (bytes + sizeof(W_) + 1) / sizeof(W_);
992 if (n+1 > BLOCK_SIZE_W) {
993 barf("allocateExec: can't handle large objects");
996 if (exec_block == NULL ||
997 exec_block->free + n + 1 > exec_block->start + BLOCK_SIZE_W) {
999 lnat pagesize = getPageSize();
1000 bd = allocGroup(stg_max(1, pagesize / BLOCK_SIZE));
1001 debugTrace(DEBUG_gc, "allocate exec block %p", bd->start);
1003 bd->flags = BF_EXEC;
1004 bd->link = exec_block;
1005 if (exec_block != NULL) {
1006 exec_block->u.back = bd;
1009 setExecutable(bd->start, bd->blocks * BLOCK_SIZE, rtsTrue);
1012 *(exec_block->free) = n; // store the size of this chunk
1013 exec_block->gen_no += n; // gen_no stores the number of words allocated
1014 ret = exec_block->free + 1;
1015 exec_block->free += n + 1;
1021 void freeExec (void *addr)
1023 StgPtr p = (StgPtr)addr - 1;
1024 bdescr *bd = Bdescr((StgPtr)p);
1026 if ((bd->flags & BF_EXEC) == 0) {
1027 barf("freeExec: not executable");
1030 if (*(StgPtr)p == 0) {
1031 barf("freeExec: already free?");
1036 bd->gen_no -= *(StgPtr)p;
1039 if (bd->gen_no == 0) {
1040 // Free the block if it is empty, but not if it is the block at
1041 // the head of the queue.
1042 if (bd != exec_block) {
1043 debugTrace(DEBUG_gc, "free exec block %p", bd->start);
1044 dbl_link_remove(bd, &exec_block);
1045 setExecutable(bd->start, bd->blocks * BLOCK_SIZE, rtsFalse);
1048 bd->free = bd->start;
1055 /* -----------------------------------------------------------------------------
1058 memInventory() checks for memory leaks by counting up all the
1059 blocks we know about and comparing that to the number of blocks
1060 allegedly floating around in the system.
1061 -------------------------------------------------------------------------- */
1066 countBlocks(bdescr *bd)
1069 for (n=0; bd != NULL; bd=bd->link) {
1075 // (*1) Just like countBlocks, except that we adjust the count for a
1076 // megablock group so that it doesn't include the extra few blocks
1077 // that would be taken up by block descriptors in the second and
1078 // subsequent megablock. This is so we can tally the count with the
1079 // number of blocks allocated in the system, for memInventory().
1081 countAllocdBlocks(bdescr *bd)
1084 for (n=0; bd != NULL; bd=bd->link) {
1086 // hack for megablock groups: see (*1) above
1087 if (bd->blocks > BLOCKS_PER_MBLOCK) {
1088 n -= (MBLOCK_SIZE / BLOCK_SIZE - BLOCKS_PER_MBLOCK)
1089 * (bd->blocks/(MBLOCK_SIZE/BLOCK_SIZE));
1096 stepBlocks (step *stp)
1098 ASSERT(countBlocks(stp->blocks) == stp->n_blocks);
1099 ASSERT(countBlocks(stp->large_objects) == stp->n_large_blocks);
1100 return stp->n_blocks + stp->n_old_blocks +
1101 countAllocdBlocks(stp->large_objects);
1109 lnat gen_blocks[RtsFlags.GcFlags.generations];
1110 lnat nursery_blocks, retainer_blocks,
1111 arena_blocks, exec_blocks;
1112 lnat live_blocks = 0, free_blocks = 0;
1114 // count the blocks we current have
1116 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
1118 for (i = 0; i < n_capabilities; i++) {
1119 gen_blocks[g] += countBlocks(capabilities[i].mut_lists[g]);
1121 gen_blocks[g] += countAllocdBlocks(generations[g].mut_list);
1122 for (s = 0; s < generations[g].n_steps; s++) {
1123 stp = &generations[g].steps[s];
1124 gen_blocks[g] += stepBlocks(stp);
1129 for (i = 0; i < n_nurseries; i++) {
1130 nursery_blocks += stepBlocks(&nurseries[i]);
1133 retainer_blocks = 0;
1135 if (RtsFlags.ProfFlags.doHeapProfile == HEAP_BY_RETAINER) {
1136 retainer_blocks = retainerStackBlocks();
1140 // count the blocks allocated by the arena allocator
1141 arena_blocks = arenaBlocks();
1143 // count the blocks containing executable memory
1144 exec_blocks = countAllocdBlocks(exec_block);
1146 /* count the blocks on the free list */
1147 free_blocks = countFreeList();
1150 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
1151 live_blocks += gen_blocks[g];
1153 live_blocks += nursery_blocks +
1154 + retainer_blocks + arena_blocks + exec_blocks;
1156 if (live_blocks + free_blocks != mblocks_allocated * BLOCKS_PER_MBLOCK)
1158 debugBelch("Memory leak detected\n");
1159 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
1160 debugBelch(" gen %d blocks : %4lu\n", g, gen_blocks[g]);
1162 debugBelch(" nursery : %4lu\n", nursery_blocks);
1163 debugBelch(" retainer : %4lu\n", retainer_blocks);
1164 debugBelch(" arena blocks : %4lu\n", arena_blocks);
1165 debugBelch(" exec : %4lu\n", exec_blocks);
1166 debugBelch(" free : %4lu\n", free_blocks);
1167 debugBelch(" total : %4lu\n\n", live_blocks + free_blocks);
1168 debugBelch(" in system : %4lu\n", mblocks_allocated * BLOCKS_PER_MBLOCK);
1174 /* Full heap sanity check. */
1180 if (RtsFlags.GcFlags.generations == 1) {
1181 checkHeap(g0s0->blocks);
1182 checkChain(g0s0->large_objects);
1185 for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
1186 for (s = 0; s < generations[g].n_steps; s++) {
1187 if (g == 0 && s == 0) { continue; }
1188 ASSERT(countBlocks(generations[g].steps[s].blocks)
1189 == generations[g].steps[s].n_blocks);
1190 ASSERT(countBlocks(generations[g].steps[s].large_objects)
1191 == generations[g].steps[s].n_large_blocks);
1192 checkHeap(generations[g].steps[s].blocks);
1193 checkChain(generations[g].steps[s].large_objects);
1195 checkMutableList(generations[g].mut_list, g);
1200 for (s = 0; s < n_nurseries; s++) {
1201 ASSERT(countBlocks(nurseries[s].blocks)
1202 == nurseries[s].n_blocks);
1203 ASSERT(countBlocks(nurseries[s].large_objects)
1204 == nurseries[s].n_large_blocks);
1207 checkFreeListSanity();
1211 /* Nursery sanity check */
1213 checkNurserySanity( step *stp )
1219 for (bd = stp->blocks; bd != NULL; bd = bd->link) {
1220 ASSERT(bd->u.back == prev);
1222 blocks += bd->blocks;
1224 ASSERT(blocks == stp->n_blocks);
1227 // handy function for use in gdb, because Bdescr() is inlined.
1228 extern bdescr *_bdescr( StgPtr p );