/* -----------------------------------------------------------------------------
- * $Id: GC.c,v 1.2 1998/12/02 13:28:23 simonm Exp $
+ * $Id: GC.c,v 1.3 1999/01/06 11:52:43 simonm Exp $
*
* Two-space garbage collector
*
StgCAF* enteredCAFs;
-static P_ toHp; /* to-space heap pointer */
-static P_ toHpLim; /* end of current to-space block */
-static bdescr *toHp_bd; /* descriptor of current to-space block */
-static nat blocks = 0; /* number of to-space blocks allocated */
-static bdescr *old_to_space = NULL; /* to-space from the last GC */
-static nat old_to_space_blocks = 0; /* size of previous to-space */
-
/* STATIC OBJECT LIST.
*
+ * During GC:
* We maintain a linked list of static objects that are still live.
* The requirements for this list are:
*
*
* An object is on the list if its static link field is non-zero; this
* means that we have to mark the end of the list with '1', not NULL.
+ *
+ * Extra notes for generational GC:
+ *
+ * Each generation has a static object list associated with it. When
+ * collecting generations up to N, we treat the static object lists
+ * from generations > N as roots.
+ *
+ * We build up a static object list while collecting generations 0..N,
+ * which is then appended to the static object list of generation N+1.
*/
-#define END_OF_STATIC_LIST stgCast(StgClosure*,1)
-static StgClosure* static_objects;
-static StgClosure* scavenged_static_objects;
+StgClosure* static_objects; /* live static objects */
+StgClosure* scavenged_static_objects; /* static objects scavenged so far */
+
+/* N is the oldest generation being collected, where the generations
+ * are numbered starting at 0. A major GC (indicated by the major_gc
+ * flag) is when we're collecting all generations. We only attempt to
+ * deal with static objects and GC CAFs when doing a major GC.
+ */
+static nat N;
+static rtsBool major_gc;
+
+/* Youngest generation that objects should be evacuated to in
+ * evacuate(). (Logically an argument to evacuate, but it's static
+ * a lot of the time so we optimise it into a global variable).
+ */
+static nat evac_gen;
/* WEAK POINTERS
*/
static StgWeak *old_weak_ptr_list; /* also pending finaliser list */
static rtsBool weak_done; /* all done for this pass */
-/* LARGE OBJECTS.
- */
-static bdescr *new_large_objects; /* large objects evacuated so far */
-static bdescr *scavenged_large_objects; /* large objects scavenged */
-
/* -----------------------------------------------------------------------------
Static function declarations
-------------------------------------------------------------------------- */
static StgClosure *evacuate(StgClosure *q);
static void zeroStaticObjectList(StgClosure* first_static);
-static void scavenge_stack(StgPtr p, StgPtr stack_end);
-static void scavenge_static(void);
-static void scavenge_large(void);
-static StgPtr scavenge(StgPtr to_scan);
static rtsBool traverse_weak_ptr_list(void);
+static void zeroMutableList(StgMutClosure *first);
static void revertDeadCAFs(void);
+static void scavenge_stack(StgPtr p, StgPtr stack_end);
+static void scavenge_large(step *step);
+static void scavenge(step *step);
+static void scavenge_static(void);
+static StgMutClosure *scavenge_mutable_list(StgMutClosure *p, nat gen);
+
#ifdef DEBUG
static void gcCAFs(void);
#endif
/* -----------------------------------------------------------------------------
GarbageCollect
- This function performs a full copying garbage collection.
+ For garbage collecting generation N (and all younger generations):
+
+ - follow all pointers in the root set. the root set includes all
+ mutable objects in all steps in all generations.
+
+ - for each pointer, evacuate the object it points to into either
+ + to-space in the next higher step in that generation, if one exists,
+ + if the object's generation == N, then evacuate it to the next
+ generation if one exists, or else to-space in the current
+ generation.
+ + if the object's generation < N, then evacuate it to to-space
+ in the next generation.
+
+ - repeatedly scavenge to-space from each step in each generation
+ being collected until no more objects can be evacuated.
+
+ - free from-space in each step, and set from-space = to-space.
+
-------------------------------------------------------------------------- */
void GarbageCollect(void (*get_roots)(void))
{
- bdescr *bd, *scan_bd, *to_space;
- StgPtr scan;
- lnat allocated, live;
- nat old_nursery_blocks = nursery_blocks; /* for stats */
- nat old_live_blocks = old_to_space_blocks; /* ditto */
+ bdescr *bd;
+ step *step;
+ lnat live, allocated;
+ nat g, s;
+
#ifdef PROFILING
CostCentreStack *prev_CCS;
#endif
* which case we need to call threadPaused() because the scheduler
* won't have done it.
*/
- if (CurrentTSO)
- threadPaused(CurrentTSO);
+ if (CurrentTSO) { threadPaused(CurrentTSO); }
/* Approximate how much we allocated: number of blocks in the
* nursery + blocks allocated via allocate() - unused nusery blocks.
for ( bd = current_nursery->link; bd != NULL; bd = bd->link ) {
allocated -= BLOCK_SIZE_W;
}
-
+
+ /* Figure out which generation to collect
+ */
+ for (g = 0; g < RtsFlags.GcFlags.generations; g++) {
+ if (generations[g].steps[0].n_blocks >= generations[g].max_blocks) {
+ N = g;
+ }
+ }
+ major_gc = (N == RtsFlags.GcFlags.generations-1);
+
/* check stack sanity *before* GC (ToDo: check all threads) */
/*IF_DEBUG(sanity, checkTSO(MainTSO,0)); */
IF_DEBUG(sanity, checkFreeListSanity());
+ /* Initialise the static object lists
+ */
static_objects = END_OF_STATIC_LIST;
scavenged_static_objects = END_OF_STATIC_LIST;
- new_large_objects = NULL;
- scavenged_large_objects = NULL;
+ /* zero the mutable list for the oldest generation (see comment by
+ * zeroMutableList below).
+ */
+ if (major_gc) {
+ zeroMutableList(generations[RtsFlags.GcFlags.generations-1].mut_list);
+ }
+
+ /* Initialise to-space in all the generations/steps that we're
+ * collecting.
+ */
+ for (g = 0; g <= N; g++) {
+ generations[g].mut_list = END_MUT_LIST;
+
+ for (s = 0; s < generations[g].n_steps; s++) {
+ /* generation 0, step 0 doesn't need to-space */
+ if (g == 0 && s == 0) { continue; }
+ /* Get a free block for to-space. Extra blocks will be chained on
+ * as necessary.
+ */
+ bd = allocBlock();
+ step = &generations[g].steps[s];
+ ASSERT(step->gen->no == g);
+ ASSERT(step->hp ? Bdescr(step->hp)->step == step : rtsTrue);
+ bd->gen = &generations[g];
+ bd->step = step;
+ bd->link = NULL;
+ step->hp = bd->start;
+ step->hpLim = step->hp + BLOCK_SIZE_W;
+ step->hp_bd = bd;
+ step->to_space = bd;
+ step->to_blocks = 1; /* ???? */
+ step->scan = bd->start;
+ step->scan_bd = bd;
+ step->new_large_objects = NULL;
+ step->scavenged_large_objects = NULL;
+ /* mark the large objects as not evacuated yet */
+ for (bd = step->large_objects; bd; bd = bd->link) {
+ bd->evacuated = 0;
+ }
+ }
+ }
+
+ /* make sure the older generations have at least one block to
+ * allocate into (this makes things easier for copy(), see below.
+ */
+ for (g = N+1; g < RtsFlags.GcFlags.generations; g++) {
+ for (s = 0; s < generations[g].n_steps; s++) {
+ step = &generations[g].steps[s];
+ if (step->hp_bd == NULL) {
+ bd = allocBlock();
+ bd->gen = &generations[g];
+ bd->step = step;
+ bd->link = NULL;
+ step->hp = bd->start;
+ step->hpLim = step->hp + BLOCK_SIZE_W;
+ step->hp_bd = bd;
+ step->blocks = bd;
+ step->n_blocks = 1;
+ }
+ /* Set the scan pointer for older generations: remember we
+ * still have to scavenge objects that have been promoted. */
+ step->scan = step->hp;
+ step->scan_bd = step->hp_bd;
+ step->to_space = NULL;
+ step->to_blocks = 0;
+ step->new_large_objects = NULL;
+ step->scavenged_large_objects = NULL;
+ }
+ }
- /* Get a free block for to-space. Extra blocks will be chained on
- * as necessary.
+ /* -----------------------------------------------------------------------
+ * follow all the roots that the application knows about.
*/
- bd = allocBlock();
- bd->step = 1; /* step 1 identifies to-space */
- toHp = bd->start;
- toHpLim = toHp + BLOCK_SIZE_W;
- toHp_bd = bd;
- to_space = bd;
- blocks = 0;
-
- scan = toHp;
- scan_bd = bd;
-
- /* follow all the roots that the application knows about */
+ evac_gen = 0;
get_roots();
+ /* follow all the roots that we know about:
+ * - mutable lists from each generation > N
+ * we want to *scavenge* these roots, not evacuate them: they're not
+ * going to move in this GC.
+ */
+ for (g = N+1; g < RtsFlags.GcFlags.generations; g++) {
+ generations[g].mut_list =
+ scavenge_mutable_list(generations[g].mut_list, g);
+ }
+
/* And don't forget to mark the TSO if we got here direct from
* Haskell! */
if (CurrentTSO) {
}
#endif
- /* Then scavenge all the objects we picked up on the first pass.
- * We may require multiple passes to find all the static objects,
- * large objects and normal objects.
+ /* -------------------------------------------------------------------------
+ * Repeatedly scavenge all the areas we know about until there's no
+ * more scavenging to be done.
*/
{
+ rtsBool flag;
loop:
- if (static_objects != END_OF_STATIC_LIST) {
+ flag = rtsFalse;
+
+ /* scavenge static objects */
+ if (major_gc && static_objects != END_OF_STATIC_LIST) {
scavenge_static();
}
- if (toHp_bd != scan_bd || scan < toHp) {
- scan = scavenge(scan);
- scan_bd = Bdescr(scan);
- goto loop;
+
+ /* scavenge each step in generations 0..N */
+ evac_gen = 0; /* just evac as normal */
+ for (g = 0; g <= N; g++) {
+ for (s = 0; s < generations[g].n_steps; s++) {
+ step = &generations[g].steps[s];
+ if (step->hp_bd != step->scan_bd || step->scan < step->hp) {
+ scavenge(step);
+ flag = rtsTrue;
+ }
+ if (step->new_large_objects != NULL) {
+ scavenge_large(step);
+ flag = rtsTrue;
+ }
+ }
}
- if (new_large_objects != NULL) {
- scavenge_large();
- goto loop;
+ if (flag) { goto loop; }
+
+ /* Now scavenge all the older generations. Objects may have been
+ * evacuated from generations <= N into older generations, and we
+ * need to scavenge these objects. We're going to make sure that
+ * any evacuations that occur move the objects into at least the
+ * same generation as the object being scavenged.
+ */
+ for (g = N+1; g < RtsFlags.GcFlags.generations; g++) {
+ for (s = 0; s < generations[g].n_steps; s++) {
+ step = &generations[g].steps[s];
+ evac_gen = g; /* evacuate to g at least */
+ old_loop:
+ if (step->hp_bd != step->scan_bd || step->scan < step->hp) {
+ scavenge(step);
+ goto old_loop;
+ }
+ if (step->new_large_objects != NULL) {
+ scavenge_large(step);
+ goto old_loop;
+ }
+ }
}
+
/* must be last... */
if (traverse_weak_ptr_list()) { /* returns rtsTrue if evaced something */
goto loop;
}
}
- /* tidy up the end of the to-space chain */
- toHp_bd->free = toHp;
- toHp_bd->link = NULL;
+ /* run through all the generations/steps and tidy up
+ */
+ for (g = 0; g <= RtsFlags.GcFlags.generations; g++) {
+ for (s = 0; s < generations[g].n_steps; s++) {
+ bdescr *next;
+ step = &generations[g].steps[s];
+
+ if (!(g == 0 && s == 0)) {
+ /* Tidy the end of the to-space chains */
+ step->hp_bd->free = step->hp;
+ step->hp_bd->link = NULL;
+ }
+
+ /* for generations we collected... */
+ if (g <= N) {
+
+ /* free old memory and shift to-space into from-space for all
+ * the collected steps (except the allocation area). These
+ * freed blocks will probaby be quickly recycled.
+ */
+ if (!(g == 0 && s == 0)) {
+ freeChain(step->blocks);
+ step->blocks = step->to_space;
+ step->n_blocks = step->to_blocks;
+ step->to_space = NULL;
+ step->to_blocks = 0;
+ }
+
+ /* LARGE OBJECTS. The current live large objects are chained on
+ * scavenged_large, having been moved during garbage
+ * collection from large_objects. Any objects left on
+ * large_objects list are therefore dead, so we free them here.
+ */
+ for (bd = step->large_objects; bd != NULL; bd = next) {
+ next = bd->link;
+ freeGroup(bd);
+ bd = next;
+ }
+ step->large_objects = step->scavenged_large_objects;
+
+ /* Set the maximum blocks for this generation,
+ * using an arbitrary factor of the no. of blocks in step 0.
+ */
+ if (g != 0) {
+ generations[g].max_blocks =
+ stg_max(generations[g].steps[s].n_blocks * 2,
+ RtsFlags.GcFlags.minAllocAreaSize * 4);
+ }
+
+ /* for older generations... */
+ } else {
+
+ /* For older generations, we need to append the
+ * scavenged_large_object list (i.e. large objects that have been
+ * promoted during this GC) to the large_object list for that step.
+ */
+ for (bd = step->scavenged_large_objects; bd; bd = next) {
+ next = bd->link;
+ dbl_link_onto(bd, &step->large_objects);
+ }
+
+ /* add the new blocks we promoted during this GC */
+ step->n_blocks += step->to_blocks;
+ }
+ }
+ }
/* revert dead CAFs and update enteredCAFs list */
revertDeadCAFs();
/* mark the garbage collected CAFs as dead */
#ifdef DEBUG
- gcCAFs();
+ if (major_gc) { gcCAFs(); }
#endif
- zeroStaticObjectList(scavenged_static_objects);
-
- /* approximate amount of live data (doesn't take into account slop
- * at end of each block). ToDo: this more accurately.
- */
- live = blocks * BLOCK_SIZE_W + ((lnat)toHp_bd->free -
- (lnat)toHp_bd->start) / sizeof(W_);
+ /* zero the scavenged static object list */
+ if (major_gc) {
+ zeroStaticObjectList(scavenged_static_objects);
+ }
- /* Free the to-space from the last GC, as it has now been collected.
- * we may be able to re-use these blocks in creating a new nursery,
- * below. If not, the blocks will probably be re-used for to-space
- * in the next GC.
+ /* Reset the nursery
*/
- if (old_to_space != NULL) {
- freeChain(old_to_space);
+ for (bd = g0s0->blocks; bd; bd = bd->link) {
+ bd->free = bd->start;
+ ASSERT(bd->gen == g0);
+ ASSERT(bd->step == g0s0);
+ }
+ current_nursery = g0s0->blocks;
+
+ live = 0;
+ for (g = 0; g <= RtsFlags.GcFlags.generations; g++) {
+ for (s = 0; s < generations[g].n_steps; s++) {
+ /* approximate amount of live data (doesn't take into account slop
+ * at end of each block). ToDo: this more accurately.
+ */
+ if (g == 0 && s == 0) { continue; }
+ step = &generations[g].steps[s];
+ live += step->n_blocks * BLOCK_SIZE_W +
+ ((lnat)step->hp_bd->free -(lnat)step->hp_bd->start) / sizeof(W_);
+ }
}
- old_to_space = to_space;
- old_to_space_blocks = blocks;
/* Free the small objects allocated via allocate(), since this will
- * all have been copied into to-space now.
+ * all have been copied into G0S1 now.
*/
if (small_alloc_list != NULL) {
freeChain(small_alloc_list);
}
small_alloc_list = NULL;
alloc_blocks = 0;
- alloc_blocks_lim = stg_max(blocks,RtsFlags.GcFlags.minAllocAreaSize);
-
- /* LARGE OBJECTS. The current live large objects are chained on
- * scavenged_large_objects, having been moved during garbage
- * collection from large_alloc_list. Any objects left on
- * large_alloc list are therefore dead, so we free them here.
- */
- {
- bdescr *bd, *next;
- bd = large_alloc_list;
- while (bd != NULL) {
- next = bd->link;
- freeGroup(bd);
- bd = next;
- }
- large_alloc_list = scavenged_large_objects;
- }
-
+ alloc_blocks_lim = RtsFlags.GcFlags.minAllocAreaSize;
/* check sanity after GC */
- IF_DEBUG(sanity, checkHeap(to_space,1));
- /*IF_DEBUG(sanity, checkTSO(MainTSO,1)); */
- IF_DEBUG(sanity, checkFreeListSanity());
-
#ifdef DEBUG
- /* symbol-table based profiling */
- heapCensus(to_space);
-#endif
-
- /* set up a new nursery. Allocate a nursery size based on a
- * function of the amount of live data (currently a factor of 2,
- * should be configurable (ToDo)). Use the blocks from the old
- * nursery if possible, freeing up any left over blocks.
- *
- * If we get near the maximum heap size, then adjust our nursery
- * size accordingly. If the nursery is the same size as the live
- * data (L), then we need 3L bytes. We can reduce the size of the
- * nursery to bring the required memory down near 2L bytes.
- *
- * A normal 2-space collector would need 4L bytes to give the same
- * performance we get from 3L bytes, reducing to the same
- * performance at 2L bytes.
- */
- if ( blocks * 4 > RtsFlags.GcFlags.maxHeapSize ) {
- int adjusted_blocks; /* signed on purpose */
- int pc_free;
-
- adjusted_blocks = (RtsFlags.GcFlags.maxHeapSize - 2 * blocks);
- 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));
- pc_free = adjusted_blocks * 100 / RtsFlags.GcFlags.maxHeapSize;
- if (pc_free < RtsFlags.GcFlags.pcFreeHeap) /* might even be < 0 */ {
- heapOverflow();
- }
- blocks = adjusted_blocks;
-
- } else {
- blocks *= 2;
- if (blocks < RtsFlags.GcFlags.minAllocAreaSize) {
- blocks = RtsFlags.GcFlags.minAllocAreaSize;
+ for (g = 0; g <= N; g++) {
+ for (s = 0; s < generations[g].n_steps; s++) {
+ if (g == 0 && s == 0) { continue; }
+ IF_DEBUG(sanity, checkHeap(generations[g].steps[s].blocks));
}
}
-
- if (nursery_blocks < blocks) {
- IF_DEBUG(gc, fprintf(stderr, "Increasing size of nursery to %d blocks\n",
- blocks));
- nursery = allocNursery(nursery,blocks-nursery_blocks);
- } else {
- bdescr *next_bd = nursery;
-
- IF_DEBUG(gc, fprintf(stderr, "Decreasing size of nursery to %d blocks\n",
- blocks));
- for (bd = nursery; nursery_blocks > blocks; nursery_blocks--) {
- next_bd = bd->link;
- freeGroup(bd);
- bd = next_bd;
- }
- nursery = bd;
- }
-
- current_nursery = nursery;
- nursery_blocks = blocks;
+ IF_DEBUG(sanity, checkFreeListSanity());
+#endif
- /* set the step number for each block in the nursery to zero */
- for (bd = nursery; bd != NULL; bd = bd->link) {
- bd->step = 0;
- bd->free = bd->start;
- }
- for (bd = to_space; bd != NULL; bd = bd->link) {
- bd->step = 0;
- }
- for (bd = large_alloc_list; bd != NULL; bd = bd->link) {
- bd->step = 0;
- }
+ IF_DEBUG(gc, stat_describe_gens());
#ifdef DEBUG
- /* check that we really have the right number of blocks in the
- * nursery, or things could really get screwed up.
- */
- {
- nat i = 0;
- for (bd = nursery; bd != NULL; bd = bd->link) {
- ASSERT(bd->free == bd->start);
- ASSERT(bd->step == 0);
- i++;
- }
- ASSERT(i == nursery_blocks);
- }
+ /* symbol-table based profiling */
+ /* heapCensus(to_space); */ /* ToDo */
#endif
/* start any pending finalisers */
#endif
/* ok, GC over: tell the stats department what happened. */
- stat_endGC(allocated,
- (old_nursery_blocks + old_live_blocks) * BLOCK_SIZE_W,
- live, "");
+ {
+ char s[512]; /* bleugh */
+ sprintf(s, "(Gen: %d)", N);
+ stat_endGC(RtsFlags.GcFlags.minAllocAreaSize * BLOCK_SIZE_W,
+ 0, live, s);
+ }
}
/* -----------------------------------------------------------------------------
pointer code decide which weak pointers are dead - if there are no
new live weak pointers, then all the currently unreachable ones are
dead.
+
+ For generational GC: we just don't try to finalise weak pointers in
+ older generations than the one we're collecting. This could
+ probably be optimised by keeping per-generation lists of weak
+ pointers, but for a few weak pointers this scheme will work.
-------------------------------------------------------------------------- */
static rtsBool
if (weak_done) { return rtsFalse; }
+ /* doesn't matter where we evacuate values/finalisers to, since
+ * these pointers are treated as roots (iff the keys are alive).
+ */
+ evac_gen = 0;
+
last_w = &old_weak_ptr_list;
for (w = old_weak_ptr_list; w; w = next_w) {
target = w->key;
loop:
+ /* ignore weak pointers in older generations */
+ if (!LOOKS_LIKE_STATIC(target) && Bdescr((P_)target)->gen->no > N) {
+ next_w = w->link;
+ continue;
+ }
+
info = get_itbl(target);
switch (info->type) {
case IND:
case IND_STATIC:
case IND_PERM:
- case IND_OLDGEN:
+ case IND_OLDGEN: /* rely on compatible layout with StgInd */
case IND_OLDGEN_PERM:
/* follow indirections */
target = ((StgInd *)target)->indirectee;
return rtsTrue;
}
-StgClosure *MarkRoot(StgClosure *root)
+StgClosure *
+MarkRoot(StgClosure *root)
{
root = evacuate(root);
return root;
}
-static __inline__ StgClosure *copy(StgClosure *src, W_ size)
+static __inline__ StgClosure *
+copy(StgClosure *src, W_ size, bdescr *bd)
{
+ step *step;
P_ to, from, dest;
- if (toHp + size >= toHpLim) {
+ /* Find out where we're going, using the handy "to" pointer in
+ * the step of the source object. If it turns out we need to
+ * evacuate to an older generation, adjust it here (see comment
+ * by evacuate()).
+ */
+ step = bd->step->to;
+ if (step->gen->no < evac_gen) {
+ step = &generations[evac_gen].steps[0];
+ }
+
+ /* chain a new block onto the to-space for the destination step if
+ * necessary.
+ */
+ if (step->hp + size >= step->hpLim) {
bdescr *bd = allocBlock();
- toHp_bd->free = toHp;
- toHp_bd->link = bd;
- bd->step = 1; /* step 1 identifies to-space */
- toHp = bd->start;
- toHpLim = toHp + BLOCK_SIZE_W;
- toHp_bd = bd;
- blocks++;
+ bd->gen = step->gen;
+ bd->step = step;
+ step->hp_bd->free = step->hp;
+ step->hp_bd->link = bd;
+ step->hp = bd->start;
+ step->hpLim = step->hp + BLOCK_SIZE_W;
+ step->hp_bd = bd;
+ step->to_blocks++;
}
- dest = toHp;
- toHp += size;
+ dest = step->hp;
+ step->hp += size;
for(to = dest, from = (P_)src; size>0; --size) {
*to++ = *from++;
}
return (StgClosure *)dest;
}
-static __inline__ void upd_evacuee(StgClosure *p, StgClosure *dest)
+static __inline__ void
+upd_evacuee(StgClosure *p, StgClosure *dest)
{
StgEvacuated *q = (StgEvacuated *)p;
This just consists of removing the object from the (doubly-linked)
large_alloc_list, and linking it on to the (singly-linked)
new_large_objects list, from where it will be scavenged later.
+
+ Convention: bd->evacuated is /= 0 for a large object that has been
+ evacuated, or 0 otherwise.
-------------------------------------------------------------------------- */
-static inline void evacuate_large(StgPtr p)
+static inline void
+evacuate_large(StgPtr p)
{
bdescr *bd = Bdescr(p);
+ step *step;
/* should point to the beginning of the block */
ASSERT(((W_)p & BLOCK_MASK) == 0);
/* already evacuated? */
- if (bd->step == 1) {
- return;
- }
+ if (bd->evacuated) { return; }
- /* remove from large_alloc_list */
+ step = bd->step;
+ /* remove from large_object list */
if (bd->back) {
bd->back->link = bd->link;
} else { /* first object in the list */
- large_alloc_list = bd->link;
+ step->large_objects = bd->link;
}
if (bd->link) {
bd->link->back = bd->back;
}
- /* link it on to the evacuated large object list */
- bd->link = new_large_objects;
- new_large_objects = bd;
- bd->step = 1;
-}
+ /* link it on to the evacuated large object list of the destination step
+ */
+ step = bd->step->to;
+ if (step->gen->no < evac_gen) {
+ step = &generations[evac_gen].steps[0];
+ }
+
+ bd->step = step;
+ bd->gen = step->gen;
+ bd->link = step->new_large_objects;
+ step->new_large_objects = bd;
+ bd->evacuated = 1;
+}
+
+/* -----------------------------------------------------------------------------
+ Evacuate a mutable object
+
+ If we evacuate a mutable object to a generation that we're not
+ collecting, cons the object onto the older generation's mutable
+ list.
+ -------------------------------------------------------------------------- */
+
+static inline void
+evacuate_mutable(StgMutClosure *c)
+{
+ bdescr *bd;
+
+ bd = Bdescr((P_)c);
+ if (bd->gen->no > N) {
+ c->mut_link = bd->gen->mut_list;
+ bd->gen->mut_list = c;
+ }
+}
/* -----------------------------------------------------------------------------
Evacuate
This is called (eventually) for every live object in the system.
+
+ The caller to evacuate specifies a desired generation in the
+ evac_gen global variable. The following conditions apply to
+ evacuating an object which resides in generation M when we're
+ collecting up to generation N
+
+ if M >= evac_gen
+ if M > N do nothing
+ else evac to step->to
+
+ if M < evac_gen evac to evac_gen, step 0
+
+ if the object is already evacuated, then we check which generation
+ it now resides in.
+
+ if M >= evac_gen do nothing
+ if M < evac_gen replace object with an indirection and evacuate
+ it to evac_gen.
+
-------------------------------------------------------------------------- */
+
static StgClosure *evacuate(StgClosure *q)
{
StgClosure *to;
+ bdescr *bd = NULL;
const StgInfoTable *info;
loop:
+ if (!LOOKS_LIKE_STATIC(q)) {
+ bd = Bdescr((P_)q);
+ /* generation too old: leave it alone */
+ if (bd->gen->no >= evac_gen && bd->gen->no > N) {
+ return q;
+ }
+ }
+
/* make sure the info pointer is into text space */
ASSERT(q && (LOOKS_LIKE_GHC_INFO(GET_INFO(q))
|| IS_HUGS_CONSTR_INFO(GET_INFO(q))));
switch (info -> type) {
case BCO:
- to = copy(q,bco_sizeW(stgCast(StgBCO*,q)));
+ to = copy(q,bco_sizeW(stgCast(StgBCO*,q)),bd);
+ upd_evacuee(q,to);
+ return to;
+
+ case MUT_VAR:
+ case MVAR:
+ to = copy(q,sizeW_fromITBL(info),bd);
upd_evacuee(q,to);
+ evacuate_mutable((StgMutClosure *)to);
return to;
case FUN:
case CAF_ENTERED:
case WEAK:
case FOREIGN:
- case MUT_VAR:
- case MVAR:
- to = copy(q,sizeW_fromITBL(info));
+ to = copy(q,sizeW_fromITBL(info),bd);
upd_evacuee(q,to);
return to;
case CAF_BLACKHOLE:
case BLACKHOLE:
- to = copy(q,BLACKHOLE_sizeW());
+ to = copy(q,BLACKHOLE_sizeW(),bd);
upd_evacuee(q,to);
return to;
{
const StgInfoTable* selectee_info;
StgClosure* selectee = stgCast(StgSelector*,q)->selectee;
+ rtsBool evaced = rtsFalse;
selector_loop:
selectee_info = get_itbl(selectee);
* with the evacuation, just update the source address with
* a pointer to the (evacuated) constructor field.
*/
- if (IS_USER_PTR(q) && Bdescr((P_)q)->step == 1) {
+ if (IS_USER_PTR(q) && evaced) {
return q;
}
goto selector_loop;
case EVACUATED:
+ evaced = rtsTrue;
selectee = stgCast(StgEvacuated*,selectee)->evacuee;
goto selector_loop;
barf("evacuate: THUNK_SELECTOR: strange selectee");
}
}
- to = copy(q,THUNK_SELECTOR_sizeW());
+ to = copy(q,THUNK_SELECTOR_sizeW(),bd);
upd_evacuee(q,to);
return to;
case IND:
case IND_OLDGEN:
/* follow chains of indirections, don't evacuate them */
- q = stgCast(StgInd*,q)->indirectee;
+ q = ((StgInd*)q)->indirectee;
goto loop;
- case CONSTR_STATIC:
+ /* ToDo: optimise STATIC_LINK for known cases.
+ - FUN_STATIC : payload[0]
+ - THUNK_STATIC : payload[1]
+ - IND_STATIC : payload[1]
+ */
case THUNK_STATIC:
case FUN_STATIC:
+ if (info->srt_len == 0) { /* small optimisation */
+ return q;
+ }
+ /* fall through */
+ case CONSTR_STATIC:
case IND_STATIC:
/* don't want to evacuate these, but we do want to follow pointers
* from SRTs - see scavenge_static.
/* put the object on the static list, if necessary.
*/
- if (STATIC_LINK(info,(StgClosure *)q) == NULL) {
+ if (major_gc && STATIC_LINK(info,(StgClosure *)q) == NULL) {
STATIC_LINK(info,(StgClosure *)q) = static_objects;
static_objects = (StgClosure *)q;
}
case PAP:
/* these are special - the payload is a copy of a chunk of stack,
tagging and all. */
- to = copy(q,pap_sizeW(stgCast(StgPAP*,q)));
+ to = copy(q,pap_sizeW(stgCast(StgPAP*,q)),bd);
upd_evacuee(q,to);
return to;
case EVACUATED:
- /* Already evacuated, just return the forwarding address */
- return stgCast(StgEvacuated*,q)->evacuee;
+ /* Already evacuated, just return the forwarding address.
+ * HOWEVER: if the requested destination generation (evac_gen) is
+ * older than the actual generation (because the object was
+ * already evacuated to a younger generation) then we have to
+ * re-evacuate it, replacing the old evacuated copy with an
+ * indirection to the new copy.
+ */
+ if (evac_gen > 0) { /* optimisation */
+ StgClosure *p = ((StgEvacuated*)q)->evacuee;
+ if (Bdescr((P_)p)->gen->no >= evac_gen) {
+ return p;
+ } else {
+ nat padding_wds = sizeW_fromITBL(get_itbl(p)) - sizeofW(StgInd);
+ StgClosure *new_p = evacuate(p); /* naughty recursive call */
+ IF_DEBUG(gc, fprintf(stderr,"ouch! double evacuation\n"));
+ ((StgEvacuated*)q)->evacuee = new_p;
+ p->header.info = &IND_info;
+ memset((P_)p + sizeofW(StgInd), 0, padding_wds * sizeof(W_));
+ return new_p;
+ }
+ }
+ return ((StgEvacuated*)q)->evacuee;
case MUT_ARR_WORDS:
case ARR_WORDS:
- case MUT_ARR_PTRS:
- case MUT_ARR_PTRS_FROZEN:
case ARR_PTRS:
{
nat size = arr_words_sizeW(stgCast(StgArrWords*,q));
return q;
} else {
/* just copy the block */
- to = copy(q,size);
+ to = copy(q,size,bd);
upd_evacuee(q,to);
return to;
}
}
+ case MUT_ARR_PTRS:
+ case MUT_ARR_PTRS_FROZEN:
+ {
+ nat size = mut_arr_ptrs_sizeW(stgCast(StgMutArrPtrs*,q));
+
+ if (size >= LARGE_OBJECT_THRESHOLD/sizeof(W_)) {
+ evacuate_large((P_)q);
+ to = q;
+ } else {
+ /* just copy the block */
+ to = copy(q,size,bd);
+ upd_evacuee(q,to);
+ }
+ if (info->type == MUT_ARR_PTRS) {
+ evacuate_mutable((StgMutClosure *)to);
+ }
+ return to;
+ }
+
case TSO:
{
StgTSO *tso = stgCast(StgTSO *,q);
*/
if (size >= LARGE_OBJECT_THRESHOLD/sizeof(W_)) {
evacuate_large((P_)q);
+ tso->mut_link = NULL; /* see below */
return q;
/* To evacuate a small TSO, we need to relocate the update frame
* list it contains.
*/
} else {
- StgTSO *new_tso = (StgTSO *)copy((StgClosure *)tso,tso_sizeW(tso));
+ StgTSO *new_tso = (StgTSO *)copy((StgClosure *)tso,tso_sizeW(tso),bd);
diff = (StgPtr)new_tso - (StgPtr)tso; /* In *words* */
relocate_TSO(tso, new_tso);
upd_evacuee(q,(StgClosure *)new_tso);
+
+ /* don't evac_mutable - these things are marked mutable as
+ * required. We *do* need to zero the mut_link field, though:
+ * this TSO might have been on the mutable list for this
+ * generation, but we're collecting this generation anyway so
+ * we didn't follow the mutable list.
+ */
+ new_tso->mut_link = NULL;
+
return (StgClosure *)new_tso;
}
}
}
static inline void
-evacuate_srt(const StgInfoTable *info)
+scavenge_srt(const StgInfoTable *info)
{
StgClosure **srt, **srt_end;
}
}
-static StgPtr
-scavenge(StgPtr to_scan)
+static void
+scavenge(step *step)
{
StgPtr p;
const StgInfoTable *info;
bdescr *bd;
- p = to_scan;
- bd = Bdescr((P_)p);
+ p = step->scan;
+ bd = step->scan_bd;
/* scavenge phase - standard breadth-first scavenging of the
* evacuated objects
*/
- while (bd != toHp_bd || p < toHp) {
+ while (bd != step->hp_bd || p < step->hp) {
/* If we're at the end of this block, move on to the next block */
- if (bd != toHp_bd && p == bd->free) {
+ if (bd != step->hp_bd && p == bd->free) {
bd = bd->link;
p = bd->start;
continue;
continue;
}
+ case MVAR:
+ /* treat MVars specially, because we don't want to evacuate the
+ * mut_link field in the middle of the closure.
+ */
+ {
+ StgMVar *mvar = ((StgMVar *)p);
+ (StgClosure *)mvar->head = evacuate((StgClosure *)mvar->head);
+ (StgClosure *)mvar->tail = evacuate((StgClosure *)mvar->tail);
+ (StgClosure *)mvar->value = evacuate((StgClosure *)mvar->value);
+ p += sizeofW(StgMVar);
+ continue;
+ }
+
case FUN:
case THUNK:
- evacuate_srt(info);
+ scavenge_srt(info);
/* fall through */
case CONSTR:
case WEAK:
case FOREIGN:
- case MVAR:
case MUT_VAR:
case IND_PERM:
case IND_OLDGEN_PERM:
continue;
case ARR_PTRS:
- case MUT_ARR_PTRS:
- case MUT_ARR_PTRS_FROZEN:
/* follow everything */
{
StgPtr next;
continue;
}
+ case MUT_ARR_PTRS:
+ case MUT_ARR_PTRS_FROZEN:
+ /* follow everything */
+ {
+ StgPtr next;
+
+ next = p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
+ for (p = (P_)((StgMutArrPtrs *)p)->payload; p < next; p++) {
+ (StgClosure *)*p = evacuate((StgClosure *)*p);
+ }
+ continue;
+ }
+
case TSO:
{
StgTSO *tso;
barf("scavenge");
}
}
- return (P_)p;
+
+ step->scan_bd = bd;
+ step->scan = p;
}
-/* scavenge_static is the scavenge code for a static closure.
- */
+/* -----------------------------------------------------------------------------
+ Scavenging mutable lists.
+
+ We treat the mutable list of each generation > N (i.e. all the
+ generations older than the one being collected) as roots. We also
+ remove non-mutable objects from the mutable list at this point.
+ -------------------------------------------------------------------------- */
+
+static StgMutClosure *
+scavenge_mutable_list(StgMutClosure *p, nat gen)
+{
+ StgInfoTable *info;
+ StgMutClosure *start;
+ StgMutClosure **prev;
+
+ evac_gen = 0;
+
+ prev = &start;
+ start = p;
+
+ for (; p != END_MUT_LIST; p = *prev) {
+
+ /* make sure the info pointer is into text space */
+ ASSERT(p && (LOOKS_LIKE_GHC_INFO(GET_INFO(p))
+ || IS_HUGS_CONSTR_INFO(GET_INFO(p))));
+
+ info = get_itbl(p);
+ switch(info->type) {
+
+ case MUT_ARR_PTRS_FROZEN:
+ /* remove this guy from the mutable list, but follow the ptrs
+ * anyway.
+ */
+ *prev = p->mut_link;
+ goto do_array;
+
+ case MUT_ARR_PTRS:
+ /* follow everything */
+ prev = &p->mut_link;
+ do_array:
+ {
+ StgPtr end, q;
+
+ end = (P_)p + mut_arr_ptrs_sizeW((StgMutArrPtrs*)p);
+ for (q = (P_)((StgMutArrPtrs *)p)->payload; q < end; q++) {
+ (StgClosure *)*q = evacuate((StgClosure *)*q);
+ }
+ continue;
+ }
+
+ case MUT_VAR:
+ ((StgMutVar *)p)->var = evacuate(((StgMutVar *)p)->var);
+ prev = &p->mut_link;
+ continue;
+
+ case TSO:
+ /* follow ptrs and remove this from the mutable list */
+ {
+ StgTSO *tso = (StgTSO *)p;
+
+ /* Don't bother scavenging if this thread is dead
+ */
+ if (!(tso->whatNext == ThreadComplete ||
+ tso->whatNext == ThreadKilled)) {
+ /* Don't need to chase the link field for any TSOs on the
+ * same queue. Just scavenge this thread's stack
+ */
+ scavenge_stack(tso->sp, &(tso->stack[tso->stack_size]));
+ }
+
+ /* Don't take this TSO off the mutable list - it might still
+ * point to some younger objects (because we set evac_gen to 0
+ * above).
+ */
+ prev = &tso->mut_link;
+ continue;
+ }
+
+ case IND_OLDGEN:
+ case IND_OLDGEN_PERM:
+ case IND_STATIC:
+ /* Remove these from the mutable list - we can be sure that the
+ * objects they point to now reside in this generation because
+ * we set evac_gen here ->
+ */
+ evac_gen = gen;
+ ((StgIndOldGen *)p)->indirectee =
+ evacuate(((StgIndOldGen *)p)->indirectee);
+ evac_gen = 0;
+ *prev = p->mut_link;
+ p->mut_link = NULL; /* paranoia? */
+ continue;
+
+ default:
+ /* shouldn't have anything else on the mutables list */
+ barf("scavenge_mutable_object: non-mutable object?");
+ }
+ }
+ return start;
+}
static void
scavenge_static(void)
StgClosure* p = static_objects;
const StgInfoTable *info;
+ /* Always evacuate straight to the oldest generation for static
+ * objects */
+ evac_gen = oldest_gen->no;
+
/* keep going until we've scavenged all the objects on the linked
list... */
while (p != END_OF_STATIC_LIST) {
+ info = get_itbl(p);
+
/* make sure the info pointer is into text space */
- ASSERT(p && LOOKS_LIKE_GHC_INFO(GET_INFO(p)));
ASSERT(p && (LOOKS_LIKE_GHC_INFO(GET_INFO(p))
|| IS_HUGS_CONSTR_INFO(GET_INFO(p))));
-
- info = get_itbl(p);
-
+
/* Take this object *off* the static_objects list,
* and put it on the scavenged_static_objects list.
*/
static_objects = STATIC_LINK(info,p);
STATIC_LINK(info,p) = scavenged_static_objects;
scavenged_static_objects = p;
-
+
switch (info -> type) {
-
+
case IND_STATIC:
{
StgInd *ind = (StgInd *)p;
case THUNK_STATIC:
case FUN_STATIC:
- evacuate_srt(info);
+ scavenge_srt(info);
/* fall through */
-
+
case CONSTR_STATIC:
{
StgPtr q, next;
StgClosure *to;
StgClosureType type = get_itbl(frame->updatee)->type;
+ p += sizeofW(StgUpdateFrame);
if (type == EVACUATED) {
frame->updatee = evacuate(frame->updatee);
- p += sizeofW(StgUpdateFrame);
continue;
} else {
+ bdescr *bd = Bdescr((P_)frame->updatee);
ASSERT(type == BLACKHOLE || type == CAF_BLACKHOLE);
- to = copy(frame->updatee, BLACKHOLE_sizeW());
+ if (bd->gen->no >= evac_gen && bd->gen->no > N) { continue; }
+ to = copy(frame->updatee, BLACKHOLE_sizeW(), bd);
upd_evacuee(frame->updatee,to);
frame->updatee = to;
- p += sizeofW(StgUpdateFrame);
continue;
}
}
- /* small bitmap (< 32 entries) */
+ /* small bitmap (< 32 entries, or 64 on a 64-bit machine) */
case RET_BCO:
case RET_SMALL:
case RET_VEC_SMALL:
}
follow_srt:
- evacuate_srt(info);
+ scavenge_srt(info);
continue;
/* large bitmap (> 32 entries) */
--------------------------------------------------------------------------- */
static void
-scavenge_large(void)
+scavenge_large(step *step)
{
bdescr *bd;
StgPtr p;
const StgInfoTable* info;
- bd = new_large_objects;
+ bd = step->new_large_objects;
+ evac_gen = step->gen->no;
- for (; bd != NULL; bd = new_large_objects) {
+ for (; bd != NULL; bd = step->new_large_objects) {
/* take this object *off* the large objects list and put it on
* the scavenged large objects list. This is so that we can
* treat new_large_objects as a stack and push new objects on
* the front when evacuating.
*/
- new_large_objects = bd->link;
- /* scavenged_large_objects is doubly linked */
- bd->link = scavenged_large_objects;
- bd->back = NULL;
- if (scavenged_large_objects) {
- scavenged_large_objects->back = bd;
- }
- scavenged_large_objects = bd;
+ step->new_large_objects = bd->link;
+ dbl_link_onto(bd, &step->scavenged_large_objects);
+ bd->evacuated = 0; /* ready for next GC */
p = bd->start;
info = get_itbl(stgCast(StgClosure*,p));
}
}
}
+
static void
zeroStaticObjectList(StgClosure* first_static)
{
}
}
+/* This function is only needed because we share the mutable link
+ * field with the static link field in an IND_STATIC, so we have to
+ * zero the mut_link field before doing a major GC, which needs the
+ * static link field.
+ *
+ * It doesn't do any harm to zero all the mutable link fields on the
+ * mutable list.
+ */
+static void
+zeroMutableList(StgMutClosure *first)
+{
+ StgMutClosure *next, *c;
+
+ for (c = first; c; c = next) {
+ next = c->mut_link;
+ c->mut_link = NULL;
+ }
+}
+
/* -----------------------------------------------------------------------------
Reverting CAFs
-
-------------------------------------------------------------------------- */
void RevertCAFs(void)
{
- while (enteredCAFs != END_CAF_LIST) {
- StgCAF* caf = enteredCAFs;
- const StgInfoTable *info = get_itbl(caf);
-
- enteredCAFs = caf->link;
- ASSERT(get_itbl(caf)->type == CAF_ENTERED);
- SET_INFO(caf,&CAF_UNENTERED_info);
- caf->value = stgCast(StgClosure*,0xdeadbeef);
- caf->link = stgCast(StgCAF*,0xdeadbeef);
- }
+ while (enteredCAFs != END_CAF_LIST) {
+ StgCAF* caf = enteredCAFs;
+
+ enteredCAFs = caf->link;
+ ASSERT(get_itbl(caf)->type == CAF_ENTERED);
+ SET_INFO(caf,&CAF_UNENTERED_info);
+ caf->value = stgCast(StgClosure*,0xdeadbeef);
+ caf->link = stgCast(StgCAF*,0xdeadbeef);
+ }
}
void revertDeadCAFs(void)
if (bh->header.info != &BLACKHOLE_info
&& bh->header.info != &CAF_BLACKHOLE_info) {
SET_INFO(bh,&BLACKHOLE_info);
- bh->blocking_queue = stgCast(StgTSO*,&END_TSO_QUEUE_closure);
+ bh->blocking_queue = END_TSO_QUEUE;
}
update_frame = update_frame->link;
&& bh->header.info != &CAF_BLACKHOLE_info
) {
SET_INFO(bh,&BLACKHOLE_info);
- bh->blocking_queue = stgCast(StgTSO*,&END_TSO_QUEUE_closure);
+ bh->blocking_queue = END_TSO_QUEUE;
}
}
projects / ghc-hetmet.git / commitdiff