STATIC_INLINE StgPtr
scavenge_arg_block (StgFunInfoTable *fun_info, StgClosure **args)
{
StgPtr p;
StgWord bitmap;
nat size;
p = (StgPtr)args;
switch (fun_info->f.fun_type) {
case ARG_GEN:
bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
size = BITMAP_SIZE(fun_info->f.b.bitmap);
goto small_bitmap;
case ARG_GEN_BIG:
size = GET_FUN_LARGE_BITMAP(fun_info)->size;
scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
p += size;
break;
default:
bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
size = BITMAP_SIZE(stg_arg_bitmaps[fun_info->f.fun_type]);
small_bitmap:
while (size > 0) {
if ((bitmap & 1) == 0) {
evacuate((StgClosure **)p);
}
p++;
bitmap = bitmap >> 1;
size--;
}
break;
}
return p;
}
// scavenge only the marked areas of a MUT_ARR_PTRS
static StgPtr scavenge_mut_arr_ptrs_marked (StgMutArrPtrs *a)
{
lnat m;
StgPtr p, q;
rtsBool any_failed;
any_failed = rtsFalse;
for (m = 0; m < mutArrPtrsCards(a->ptrs); m++)
{
if (*mutArrPtrsCard(a,m) != 0) {
p = (StgPtr)&a->payload[m << MUT_ARR_PTRS_CARD_BITS];
q = stg_min(p + (1 << MUT_ARR_PTRS_CARD_BITS),
(StgPtr)&a->payload[a->ptrs]);
for (; p < q; p++) {
evacuate((StgClosure**)p);
}
if (gct->failed_to_evac) {
any_failed = rtsTrue;
gct->failed_to_evac = rtsFalse;
} else {
*mutArrPtrsCard(a,m) = 0;
}
}
}
gct->failed_to_evac = any_failed;
return (StgPtr)a + mut_arr_ptrs_sizeW(a);
}
/* Similar to scavenge_large_bitmap(), but we don't write back the
* pointers we get back from evacuate().
*/
static void
scavenge_large_srt_bitmap( StgLargeSRT *large_srt )
{
nat i, b, size;
StgWord bitmap;
StgClosure **p;
b = 0;
bitmap = large_srt->l.bitmap[b];
size = (nat)large_srt->l.size;
p = (StgClosure **)large_srt->srt;
for (i = 0; i < size; ) {
if ((bitmap & 1) != 0) {
evacuate(p);
}
i++;
p++;
if (i % BITS_IN(W_) == 0) {
b++;
bitmap = large_srt->l.bitmap[b];
} else {
bitmap = bitmap >> 1;
}
}
}
void scavenge_small(void *obj, struct s_gc* s_gc){
void** obj_ptr = (void**)obj;
unsigned int nptrs = GET_NPTR(obj);
debug("%s : obj %08x nptr: %d (s:%d n:%d)\n",__FUNCTION__,(unsigned int)(obj),nptrs,GET_SIZE(obj),GET_NPTR(obj));
for(;nptrs > 0;nptrs--){
evacuate(obj_ptr,s_gc);
obj_ptr++;
}
}
void scavenge_big(void *obj, struct s_gc* s_gc){
struct big_bdescr* big_block = (struct big_bdescr*)GET_BLOCK(obj);
unsigned int nptrs = big_block->nptrs;
void** obj_ptr = (void**)obj;
debug("%s : obj %08x\n",__FUNCTION__,(unsigned int)(obj));
for(;nptrs > 0;nptrs--){
evacuate(obj_ptr,s_gc);
obj_ptr++;
}
}
STATIC_INLINE GNUC_ATTR_HOT void
copy_tag(StgClosure **p, const StgInfoTable *info,
StgClosure *src, nat size, nat gen_no, StgWord tag)
{
StgPtr to, from;
nat i;
to = alloc_for_copy(size,gen_no);
from = (StgPtr)src;
to[0] = (W_)info;
for (i = 1; i < size; i++) { // unroll for small i
to[i] = from[i];
}
// if (to+size+2 < bd->start + BLOCK_SIZE_W) {
// __builtin_prefetch(to + size + 2, 1);
// }
#if defined(PARALLEL_GC)
{
const StgInfoTable *new_info;
new_info = (const StgInfoTable *)cas((StgPtr)&src->header.info, (W_)info, MK_FORWARDING_PTR(to));
if (new_info != info) {
#ifdef PROFILING
// We copied this object at the same time as another
// thread. We'll evacuate the object again and the copy
// we just made will be discarded at the next GC, but we
// may have copied it after the other thread called
// SET_EVACUAEE_FOR_LDV(), which would confuse the LDV
// profiler when it encounters this closure in
// processHeapClosureForDead. So we reset the LDVW field
// here.
LDVW(to) = 0;
#endif
return evacuate(p); // does the failed_to_evac stuff
} else {
*p = TAG_CLOSURE(tag,(StgClosure*)to);
}
}
#else
src->header.info = (const StgInfoTable *)MK_FORWARDING_PTR(to);
*p = TAG_CLOSURE(tag,(StgClosure*)to);
#endif
#ifdef PROFILING
// We store the size of the just evacuated object in the LDV word so that
// the profiler can guess the position of the next object later.
// This is safe only if we are sure that no other thread evacuates
// the object again, so we cannot use copy_tag_nolock when PROFILING.
SET_EVACUAEE_FOR_LDV(from, size);
#endif
}
static StgPtr scavenge_mut_arr_ptrs (StgMutArrPtrs *a)
{
lnat m;
rtsBool any_failed;
StgPtr p, q;
any_failed = rtsFalse;
p = (StgPtr)&a->payload[0];
for (m = 0; (int)m < (int)mutArrPtrsCards(a->ptrs) - 1; m++)
{
q = p + (1 << MUT_ARR_PTRS_CARD_BITS);
for (; p < q; p++) {
evacuate((StgClosure**)p);
}
if (gct->failed_to_evac) {
any_failed = rtsTrue;
*mutArrPtrsCard(a,m) = 1;
gct->failed_to_evac = rtsFalse;
} else {
*mutArrPtrsCard(a,m) = 0;
}
}
q = (StgPtr)&a->payload[a->ptrs];
if (p < q) {
for (; p < q; p++) {
evacuate((StgClosure**)p);
}
if (gct->failed_to_evac) {
any_failed = rtsTrue;
*mutArrPtrsCard(a,m) = 1;
gct->failed_to_evac = rtsFalse;
} else {
*mutArrPtrsCard(a,m) = 0;
}
}
gct->failed_to_evac = any_failed;
return (StgPtr)a + mut_arr_ptrs_sizeW(a);
}
STATIC_INLINE StgPtr
scavenge_small_bitmap (StgPtr p, nat size, StgWord bitmap)
{
while (size > 0) {
if ((bitmap & 1) == 0) {
evacuate((StgClosure **)p);
}
p++;
bitmap = bitmap >> 1;
size--;
}
return p;
}
/* evacuate the SRT. If srt_bitmap is zero, then there isn't an
* srt field in the info table. That's ok, because we'll
* never dereference it.
*/
STATIC_INLINE GNUC_ATTR_HOT void
scavenge_srt (StgClosure **srt, nat srt_bitmap)
{
nat bitmap;
StgClosure **p;
bitmap = srt_bitmap;
p = srt;
if (bitmap == (StgHalfWord)(-1)) {
scavenge_large_srt_bitmap( (StgLargeSRT *)srt );
return;
}
while (bitmap != 0) {
if ((bitmap & 1) != 0) {
#if defined(COMPILING_WINDOWS_DLL)
// Special-case to handle references to closures hiding out in DLLs, since
// double indirections required to get at those. The code generator knows
// which is which when generating the SRT, so it stores the (indirect)
// reference to the DLL closure in the table by first adding one to it.
// We check for this here, and undo the addition before evacuating it.
//
// If the SRT entry hasn't got bit 0 set, the SRT entry points to a
// closure that's fixed at link-time, and no extra magic is required.
if ( (lnat)(*srt) & 0x1 ) {
evacuate( (StgClosure**) ((lnat) (*srt) & ~0x1));
} else {
evacuate(p);
}
#else
evacuate(p);
#endif
}
p++;
bitmap = bitmap >> 1;
}
}
/* Special version of copy() for when we only want to copy the info
* pointer of an object, but reserve some padding after it. This is
* used to optimise evacuation of TSOs.
*/
static bool
copyPart(StgClosure **p, StgClosure *src, uint32_t size_to_reserve,
uint32_t size_to_copy, uint32_t gen_no)
{
StgPtr to, from;
uint32_t i;
StgWord info;
#if defined(PARALLEL_GC)
spin:
info = xchg((StgPtr)&src->header.info, (W_)&stg_WHITEHOLE_info);
if (info == (W_)&stg_WHITEHOLE_info) {
#if defined(PROF_SPIN)
whitehole_gc_spin++;
#endif
busy_wait_nop();
goto spin;
}
if (IS_FORWARDING_PTR(info)) {
src->header.info = (const StgInfoTable *)info;
evacuate(p); // does the failed_to_evac stuff
return false;
}
#else
info = (W_)src->header.info;
#endif
to = alloc_for_copy(size_to_reserve, gen_no);
from = (StgPtr)src;
to[0] = info;
for (i = 1; i < size_to_copy; i++) { // unroll for small i
to[i] = from[i];
}
write_barrier();
src->header.info = (const StgInfoTable*)MK_FORWARDING_PTR(to);
*p = (StgClosure *)to;
#if defined(PROFILING)
// We store the size of the just evacuated object in the LDV word so that
// the profiler can guess the position of the next object later.
SET_EVACUAEE_FOR_LDV(from, size_to_reserve);
// fill the slop
if (size_to_reserve - size_to_copy > 0)
LDV_FILL_SLOP(to + size_to_copy, (int)(size_to_reserve - size_to_copy));
#endif
return true;
}
static void
scavenge_large_bitmap( StgPtr p, StgLargeBitmap *large_bitmap, nat size )
{
nat i, j, b;
StgWord bitmap;
b = 0;
for (i = 0; i < size; b++) {
bitmap = large_bitmap->bitmap[b];
j = stg_min(size-i, BITS_IN(W_));
i += j;
for (; j > 0; j--, p++) {
if ((bitmap & 1) == 0) {
evacuate((StgClosure **)p);
}
bitmap = bitmap >> 1;
}
}
}
STATIC_INLINE GNUC_ATTR_HOT void
copy_tag(StgClosure **p, const StgInfoTable *info,
StgClosure *src, nat size, nat gen_no, StgWord tag)
{
StgPtr to, from;
nat i;
to = alloc_for_copy(size,gen_no);
from = (StgPtr)src;
to[0] = (W_)info;
for (i = 1; i < size; i++) { // unroll for small i
to[i] = from[i];
}
// if (to+size+2 < bd->start + BLOCK_SIZE_W) {
// __builtin_prefetch(to + size + 2, 1);
// }
#if defined(PARALLEL_GC)
{
const StgInfoTable *new_info;
new_info = (const StgInfoTable *)cas((StgPtr)&src->header.info, (W_)info, MK_FORWARDING_PTR(to));
if (new_info != info) {
return evacuate(p); // does the failed_to_evac stuff
} else {
*p = TAG_CLOSURE(tag,(StgClosure*)to);
}
}
#else
src->header.info = (const StgInfoTable *)MK_FORWARDING_PTR(to);
*p = TAG_CLOSURE(tag,(StgClosure*)to);
#endif
#ifdef PROFILING
// We store the size of the just evacuated object in the LDV word so that
// the profiler can guess the position of the next object later.
SET_EVACUAEE_FOR_LDV(from, size);
#endif
}
STATIC_INLINE GNUC_ATTR_HOT StgPtr
scavenge_PAP_payload (StgClosure *fun, StgClosure **payload, StgWord size)
{
StgPtr p;
StgWord bitmap;
StgFunInfoTable *fun_info;
fun_info = get_fun_itbl(UNTAG_CLOSURE(fun));
ASSERT(fun_info->i.type != PAP);
p = (StgPtr)payload;
switch (fun_info->f.fun_type) {
case ARG_GEN:
bitmap = BITMAP_BITS(fun_info->f.b.bitmap);
goto small_bitmap;
case ARG_GEN_BIG:
scavenge_large_bitmap(p, GET_FUN_LARGE_BITMAP(fun_info), size);
p += size;
break;
case ARG_BCO:
scavenge_large_bitmap((StgPtr)payload, BCO_BITMAP(fun), size);
p += size;
break;
default:
bitmap = BITMAP_BITS(stg_arg_bitmaps[fun_info->f.fun_type]);
small_bitmap:
while (size > 0) {
if ((bitmap & 1) == 0) {
evacuate((StgClosure **)p);
}
p++;
bitmap = bitmap >> 1;
size--;
}
break;
}
return p;
}
static void
scavengeTSO (StgTSO *tso)
{
rtsBool saved_eager;
debugTrace(DEBUG_gc,"scavenging thread %d",(int)tso->id);
// update the pointer from the Task.
if (tso->bound != NULL) {
tso->bound->tso = tso;
}
saved_eager = gct->eager_promotion;
gct->eager_promotion = rtsFalse;
evacuate((StgClosure **)&tso->blocked_exceptions);
evacuate((StgClosure **)&tso->bq);
// scavange current transaction record
evacuate((StgClosure **)&tso->trec);
evacuate((StgClosure **)&tso->stackobj);
evacuate((StgClosure **)&tso->_link);
if ( tso->why_blocked == BlockedOnMVar
|| tso->why_blocked == BlockedOnBlackHole
|| tso->why_blocked == BlockedOnMsgThrowTo
|| tso->why_blocked == NotBlocked
) {
evacuate(&tso->block_info.closure);
}
#ifdef THREADED_RTS
// in the THREADED_RTS, block_info.closure must always point to a
// valid closure, because we assume this in throwTo(). In the
// non-threaded RTS it might be a FD (for
// BlockedOnRead/BlockedOnWrite) or a time value (BlockedOnDelay)
else {
tso->block_info.closure = (StgClosure *)END_TSO_QUEUE;
}
#endif
tso->dirty = gct->failed_to_evac;
gct->eager_promotion = saved_eager;
}
static void
eval_thunk_selector (StgClosure **q, StgSelector * p, rtsBool evac)
// NB. for legacy reasons, p & q are swapped around :(
{
nat field;
StgInfoTable *info;
StgWord info_ptr;
StgClosure *selectee;
StgSelector *prev_thunk_selector;
bdescr *bd;
StgClosure *val;
prev_thunk_selector = NULL;
// this is a chain of THUNK_SELECTORs that we are going to update
// to point to the value of the current THUNK_SELECTOR. Each
// closure on the chain is a WHITEHOLE, and points to the next in the
// chain with payload[0].
selector_chain:
bd = Bdescr((StgPtr)p);
if (HEAP_ALLOCED_GC(p)) {
// If the THUNK_SELECTOR is in to-space or in a generation that we
// are not collecting, then bale out early. We won't be able to
// save any space in any case, and updating with an indirection is
// trickier in a non-collected gen: we would have to update the
// mutable list.
if (bd->flags & BF_EVACUATED) {
unchain_thunk_selectors(prev_thunk_selector, (StgClosure *)p);
*q = (StgClosure *)p;
// shortcut, behave as for: if (evac) evacuate(q);
if (evac && bd->gen_no < gct->evac_gen_no) {
gct->failed_to_evac = rtsTrue;
TICK_GC_FAILED_PROMOTION();
}
return;
}
// we don't update THUNK_SELECTORS in the compacted
// generation, because compaction does not remove the INDs
// that result, this causes confusion later
// (scavenge_mark_stack doesn't deal with IND). BEWARE! This
// bit is very tricky to get right. If you make changes
// around here, test by compiling stage 3 with +RTS -c -RTS.
if (bd->flags & BF_MARKED) {
// must call evacuate() to mark this closure if evac==rtsTrue
*q = (StgClosure *)p;
if (evac) evacuate(q);
unchain_thunk_selectors(prev_thunk_selector, (StgClosure *)p);
return;
}
}
// WHITEHOLE the selector thunk, since it is now under evaluation.
// This is important to stop us going into an infinite loop if
// this selector thunk eventually refers to itself.
#if defined(THREADED_RTS)
// In threaded mode, we'll use WHITEHOLE to lock the selector
// thunk while we evaluate it.
{
do {
info_ptr = xchg((StgPtr)&p->header.info, (W_)&stg_WHITEHOLE_info);
} while (info_ptr == (W_)&stg_WHITEHOLE_info);
// make sure someone else didn't get here first...
if (IS_FORWARDING_PTR(info_ptr) ||
INFO_PTR_TO_STRUCT((StgInfoTable *)info_ptr)->type != THUNK_SELECTOR) {
// v. tricky now. The THUNK_SELECTOR has been evacuated
// by another thread, and is now either a forwarding ptr or IND.
// We need to extract ourselves from the current situation
// as cleanly as possible.
// - unlock the closure
// - update *q, we may have done *some* evaluation
// - if evac, we need to call evacuate(), because we
// need the write-barrier stuff.
// - undo the chain we've built to point to p.
SET_INFO((StgClosure *)p, (const StgInfoTable *)info_ptr);
*q = (StgClosure *)p;
if (evac) evacuate(q);
unchain_thunk_selectors(prev_thunk_selector, (StgClosure *)p);
return;
}
}
#else
// Save the real info pointer (NOTE: not the same as get_itbl()).
info_ptr = (StgWord)p->header.info;
SET_INFO((StgClosure *)p,&stg_WHITEHOLE_info);
#endif
field = INFO_PTR_TO_STRUCT((StgInfoTable *)info_ptr)->layout.selector_offset;
// The selectee might be a constructor closure,
// so we untag the pointer.
selectee = UNTAG_CLOSURE(p->selectee);
selector_loop:
// selectee now points to the closure that we're trying to select
// a field from. It may or may not be in to-space: we try not to
// end up in to-space, but it's impractical to avoid it in
// general. The compacting GC scatters to-space pointers in
// from-space during marking, for example. We rely on the property
// that evacuate() doesn't mind if it gets passed a to-space pointer.
info = (StgInfoTable*)selectee->header.info;
if (IS_FORWARDING_PTR(info)) {
// We don't follow pointers into to-space; the constructor
// has already been evacuated, so we won't save any space
// leaks by evaluating this selector thunk anyhow.
goto bale_out;
}
info = INFO_PTR_TO_STRUCT(info);
switch (info->type) {
case WHITEHOLE:
goto bale_out; // about to be evacuated by another thread (or a loop).
case CONSTR:
case CONSTR_1_0:
case CONSTR_0_1:
case CONSTR_2_0:
case CONSTR_1_1:
case CONSTR_0_2:
case CONSTR_STATIC:
case CONSTR_NOCAF_STATIC:
{
// check that the size is in range
ASSERT(field < (StgWord32)(info->layout.payload.ptrs +
info->layout.payload.nptrs));
// Select the right field from the constructor
val = selectee->payload[field];
#ifdef PROFILING
// For the purposes of LDV profiling, we have destroyed
// the original selector thunk, p.
if (era > 0) {
// Only modify the info pointer when LDV profiling is
// enabled. Note that this is incompatible with parallel GC,
// because it would allow other threads to start evaluating
// the same selector thunk.
SET_INFO((StgClosure*)p, (StgInfoTable *)info_ptr);
OVERWRITING_CLOSURE((StgClosure*)p);
SET_INFO((StgClosure*)p, &stg_WHITEHOLE_info);
}
#endif
// the closure in val is now the "value" of the
// THUNK_SELECTOR in p. However, val may itself be a
// THUNK_SELECTOR, in which case we want to continue
// evaluating until we find the real value, and then
// update the whole chain to point to the value.
val_loop:
info_ptr = (StgWord)UNTAG_CLOSURE(val)->header.info;
if (!IS_FORWARDING_PTR(info_ptr))
{
info = INFO_PTR_TO_STRUCT((StgInfoTable *)info_ptr);
switch (info->type) {
case IND:
case IND_STATIC:
val = ((StgInd *)val)->indirectee;
goto val_loop;
case THUNK_SELECTOR:
((StgClosure*)p)->payload[0] = (StgClosure *)prev_thunk_selector;
prev_thunk_selector = p;
p = (StgSelector*)val;
goto selector_chain;
default:
break;
}
}
((StgClosure*)p)->payload[0] = (StgClosure *)prev_thunk_selector;
prev_thunk_selector = p;
*q = val;
// update the other selectors in the chain *before*
// evacuating the value. This is necessary in the case
// where the value turns out to be one of the selectors
// in the chain (i.e. we have a loop), and evacuating it
// would corrupt the chain.
unchain_thunk_selectors(prev_thunk_selector, val);
// evacuate() cannot recurse through
// eval_thunk_selector(), because we know val is not
// a THUNK_SELECTOR.
if (evac) evacuate(q);
return;
}
case IND:
case IND_STATIC:
// Again, we might need to untag a constructor.
selectee = UNTAG_CLOSURE( ((StgInd *)selectee)->indirectee );
goto selector_loop;
case BLACKHOLE:
{
StgClosure *r;
const StgInfoTable *i;
r = ((StgInd*)selectee)->indirectee;
// establish whether this BH has been updated, and is now an
// indirection, as in evacuate().
if (GET_CLOSURE_TAG(r) == 0) {
i = r->header.info;
if (IS_FORWARDING_PTR(i)) {
r = (StgClosure *)UN_FORWARDING_PTR(i);
i = r->header.info;
}
if (i == &stg_TSO_info
|| i == &stg_WHITEHOLE_info
|| i == &stg_BLOCKING_QUEUE_CLEAN_info
|| i == &stg_BLOCKING_QUEUE_DIRTY_info) {
goto bale_out;
}
ASSERT(i != &stg_IND_info);
}
selectee = UNTAG_CLOSURE( ((StgInd *)selectee)->indirectee );
goto selector_loop;
}
case THUNK_SELECTOR:
{
StgClosure *val;
// recursively evaluate this selector. We don't want to
// recurse indefinitely, so we impose a depth bound.
if (gct->thunk_selector_depth >= MAX_THUNK_SELECTOR_DEPTH) {
goto bale_out;
}
gct->thunk_selector_depth++;
// rtsFalse says "don't evacuate the result". It will,
// however, update any THUNK_SELECTORs that are evaluated
// along the way.
eval_thunk_selector(&val, (StgSelector*)selectee, rtsFalse);
gct->thunk_selector_depth--;
// did we actually manage to evaluate it?
if (val == selectee) goto bale_out;
// Of course this pointer might be tagged...
selectee = UNTAG_CLOSURE(val);
goto selector_loop;
}
case AP:
case AP_STACK:
case THUNK:
case THUNK_1_0:
case THUNK_0_1:
case THUNK_2_0:
case THUNK_1_1:
case THUNK_0_2:
case THUNK_STATIC:
// not evaluated yet
goto bale_out;
default:
barf("eval_thunk_selector: strange selectee %d",
(int)(info->type));
}
bale_out:
// We didn't manage to evaluate this thunk; restore the old info
// pointer. But don't forget: we still need to evacuate the thunk itself.
SET_INFO((StgClosure *)p, (const StgInfoTable *)info_ptr);
// THREADED_RTS: we just unlocked the thunk, so another thread
// might get in and update it. copy() will lock it again and
// check whether it was updated in the meantime.
*q = (StgClosure *)p;
if (evac) {
copy(q,(const StgInfoTable *)info_ptr,(StgClosure *)p,THUNK_SELECTOR_sizeW(),bd->dest_no);
}
unchain_thunk_selectors(prev_thunk_selector, *q);
return;
}
static void
scavenge_stack(StgPtr p, StgPtr stack_end)
{
const StgRetInfoTable* info;
StgWord bitmap;
nat size;
/*
* Each time around this loop, we are looking at a chunk of stack
* that starts with an activation record.
*/
while (p < stack_end) {
info = get_ret_itbl((StgClosure *)p);
switch (info->i.type) {
case UPDATE_FRAME:
// In SMP, we can get update frames that point to indirections
// when two threads evaluate the same thunk. We do attempt to
// discover this situation in threadPaused(), but it's
// possible that the following sequence occurs:
//
// A B
// enter T
// enter T
// blackhole T
// update T
// GC
//
// Now T is an indirection, and the update frame is already
// marked on A's stack, so we won't traverse it again in
// threadPaused(). We could traverse the whole stack again
// before GC, but that seems like overkill.
//
// Scavenging this update frame as normal would be disastrous;
// the updatee would end up pointing to the value. So we
// check whether the value after evacuation is a BLACKHOLE,
// and if not, we change the update frame to an stg_enter
// frame that simply returns the value. Hence, blackholing is
// compulsory (otherwise we would have to check for thunks
// too).
//
// Note [upd-black-hole]
// One slight hiccup is that the THUNK_SELECTOR machinery can
// overwrite the updatee with an IND. In parallel GC, this
// could even be happening concurrently, so we can't check for
// the IND. Fortunately if we assume that blackholing is
// happening (either lazy or eager), then we can be sure that
// the updatee is never a THUNK_SELECTOR and we're ok.
// NB. this is a new invariant: blackholing is not optional.
{
StgUpdateFrame *frame = (StgUpdateFrame *)p;
StgClosure *v;
evacuate(&frame->updatee);
v = frame->updatee;
if (GET_CLOSURE_TAG(v) != 0 ||
(get_itbl(v)->type != BLACKHOLE)) {
// blackholing is compulsory, see above.
frame->header.info = (const StgInfoTable*)&stg_enter_checkbh_info;
}
ASSERT(v->header.info != &stg_TSO_info);
p += sizeofW(StgUpdateFrame);
continue;
}
// small bitmap (< 32 entries, or 64 on a 64-bit machine)
case CATCH_STM_FRAME:
case CATCH_RETRY_FRAME:
case ATOMICALLY_FRAME:
case UNDERFLOW_FRAME:
case STOP_FRAME:
case CATCH_FRAME:
case RET_SMALL:
bitmap = BITMAP_BITS(info->i.layout.bitmap);
size = BITMAP_SIZE(info->i.layout.bitmap);
// NOTE: the payload starts immediately after the info-ptr, we
// don't have an StgHeader in the same sense as a heap closure.
p++;
p = scavenge_small_bitmap(p, size, bitmap);
follow_srt:
if (major_gc)
scavenge_srt((StgClosure **)GET_SRT(info), info->i.srt_bitmap);
continue;
case RET_BCO: {
StgBCO *bco;
nat size;
p++;
evacuate((StgClosure **)p);
bco = (StgBCO *)*p;
p++;
size = BCO_BITMAP_SIZE(bco);
scavenge_large_bitmap(p, BCO_BITMAP(bco), size);
p += size;
continue;
}
// large bitmap (> 32 entries, or > 64 on a 64-bit machine)
case RET_BIG:
{
nat size;
size = GET_LARGE_BITMAP(&info->i)->size;
p++;
scavenge_large_bitmap(p, GET_LARGE_BITMAP(&info->i), size);
p += size;
// and don't forget to follow the SRT
goto follow_srt;
}
// Dynamic bitmap: the mask is stored on the stack, and
// there are a number of non-pointers followed by a number
// of pointers above the bitmapped area. (see StgMacros.h,
// HEAP_CHK_GEN).
case RET_DYN:
{
StgWord dyn;
dyn = ((StgRetDyn *)p)->liveness;
// traverse the bitmap first
bitmap = RET_DYN_LIVENESS(dyn);
p = (P_)&((StgRetDyn *)p)->payload[0];
size = RET_DYN_BITMAP_SIZE;
p = scavenge_small_bitmap(p, size, bitmap);
// skip over the non-ptr words
p += RET_DYN_NONPTRS(dyn) + RET_DYN_NONPTR_REGS_SIZE;
// follow the ptr words
for (size = RET_DYN_PTRS(dyn); size > 0; size--) {
evacuate((StgClosure **)p);
p++;
}
continue;
}
case RET_FUN:
{
StgRetFun *ret_fun = (StgRetFun *)p;
StgFunInfoTable *fun_info;
evacuate(&ret_fun->fun);
fun_info = get_fun_itbl(UNTAG_CLOSURE(ret_fun->fun));
p = scavenge_arg_block(fun_info, ret_fun->payload);
goto follow_srt;
}
default:
barf("scavenge_stack: weird activation record found on stack: %d", (int)(info->i.type));
}
}
}
STATIC_INLINE GNUC_ATTR_HOT StgPtr
scavenge_PAP (StgPAP *pap)
{
evacuate(&pap->fun);
return scavenge_PAP_payload (pap->fun, pap->payload, pap->n_args);
}
static void
scavenge_static(void)
{
StgClosure* p;
const StgInfoTable *info;
debugTrace(DEBUG_gc, "scavenging static objects");
/* Always evacuate straight to the oldest generation for static
* objects */
gct->evac_gen_no = oldest_gen->no;
/* keep going until we've scavenged all the objects on the linked
list... */
while (1) {
/* get the next static object from the list. Remember, there might
* be more stuff on this list after each evacuation...
* (static_objects is a global)
*/
p = gct->static_objects;
if (p == END_OF_STATIC_LIST) {
break;
}
ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
info = get_itbl(p);
/*
if (info->type==RBH)
info = REVERT_INFOPTR(info); // if it's an RBH, look at the orig closure
*/
// make sure the info pointer is into text space
/* Take this object *off* the static_objects list,
* and put it on the scavenged_static_objects list.
*/
gct->static_objects = *STATIC_LINK(info,p);
*STATIC_LINK(info,p) = gct->scavenged_static_objects;
gct->scavenged_static_objects = p;
switch (info -> type) {
case IND_STATIC:
{
StgInd *ind = (StgInd *)p;
evacuate(&ind->indirectee);
/* might fail to evacuate it, in which case we have to pop it
* back on the mutable list of the oldest generation. We
* leave it *on* the scavenged_static_objects list, though,
* in case we visit this object again.
*/
if (gct->failed_to_evac) {
gct->failed_to_evac = rtsFalse;
recordMutableGen_GC((StgClosure *)p,oldest_gen->no);
}
break;
}
case THUNK_STATIC:
scavenge_thunk_srt(info);
break;
case FUN_STATIC:
scavenge_fun_srt(info);
break;
case CONSTR_STATIC:
{
StgPtr q, next;
next = (P_)p->payload + info->layout.payload.ptrs;
// evacuate the pointers
for (q = (P_)p->payload; q < next; q++) {
evacuate((StgClosure **)q);
}
break;
}
default:
barf("scavenge_static: strange closure %d", (int)(info->type));
}
ASSERT(gct->failed_to_evac == rtsFalse);
}
}
void perform_gc(struct s_arena* arena){
struct s_gc s_gc;
init_gc(&s_gc,arena);
/* phase 1 mark or evac root */
evacuate(arena->root,&s_gc);
/* phase 2 process scavenge queue */
do{
void* scav_obj;
scav_obj = find_small_object(&s_gc);
if( scav_obj != NULL){
scavenge_small(scav_obj,&s_gc);
continue;
}
scav_obj = find_big_object(&s_gc);
if( scav_obj != NULL){
scavenge_big(scav_obj,&s_gc);
continue;
}
/* no scavenging object */
break;
}while( 1 );
debug("========================================================\n",NULL);
debug("%s : small %016x(%d) big %016x(%d)\n",__FUNCTION__,s_gc.small_evaced,s_gc.small_evaced,s_gc.big_evaced,s_gc.big_evaced);
debug("========================================================\n",NULL);
/* phase 3 adjust objects */
/* big dead objects : free */
struct bdescr* block;
block = TAILQ_FIRST(&(arena->big_blocks));
while(block){
debug("-",NULL);
struct bdescr* new_block = TAILQ_NEXT(block,link);
debug("%s : %08x dead big\n",__FUNCTION__,(unsigned int)block);
/* finalize */
/* TODO if any finalizer, call here (before small blocks released)*/
free_big_block(arena,(struct big_bdescr*)block);
block = new_block;
}
/* big live objects : clear used bit & move to arena->blocks */
TAILQ_INIT(&(arena->big_blocks));
TAILQ_CONCAT(&(arena->big_blocks),&(s_gc.big_live_queue),link);
block = TAILQ_FIRST(&(arena->big_blocks));
while(block){
debug("+",NULL);
struct bdescr* new_block = TAILQ_NEXT(block,link);
debug("%s : %08x live big\n",__FUNCTION__,(unsigned int)block);
((struct big_bdescr*)block)-> used = 0;
block = new_block;
}
/* free old spaces */
block = TAILQ_FIRST(&(arena->blocks));
while(block){
debug("-",NULL);
struct bdescr* next_block = TAILQ_NEXT(block,link);
free_single_block(arena,(struct single_bdescr*)block);
debug("%s : %08x dead small\n",__FUNCTION__,(unsigned int)block);
block = next_block;
}
/* move live small area */
TAILQ_INIT(&(arena->blocks));
TAILQ_CONCAT(&(arena->blocks),&(s_gc.to_space_queue),link);
#ifdef CGC_DEBUG
block = TAILQ_FIRST(&(arena->blocks));
while(block){
debug("+",NULL);
struct bdescr* next_block = TAILQ_NEXT(block,link);
debug("%s : %08x live small\n",__FUNCTION__,(unsigned int)block);
block = next_block;
}
#endif
debug("========================================================\n",NULL);
debug("%s : end\n",__FUNCTION__);
debug("========================================================\n",NULL);
}
STATIC_INLINE StgPtr
scavenge_AP (StgAP *ap)
{
evacuate(&ap->fun);
return scavenge_PAP_payload (ap->fun, ap->payload, ap->n_args);
}
static rtsBool
scavenge_one(StgPtr p)
{
const StgInfoTable *info;
rtsBool no_luck;
rtsBool saved_eager_promotion;
saved_eager_promotion = gct->eager_promotion;
ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
info = get_itbl((StgClosure *)p);
switch (info->type) {
case MVAR_CLEAN:
case MVAR_DIRTY:
{
StgMVar *mvar = ((StgMVar *)p);
gct->eager_promotion = rtsFalse;
evacuate((StgClosure **)&mvar->head);
evacuate((StgClosure **)&mvar->tail);
evacuate((StgClosure **)&mvar->value);
gct->eager_promotion = saved_eager_promotion;
if (gct->failed_to_evac) {
mvar->header.info = &stg_MVAR_DIRTY_info;
} else {
mvar->header.info = &stg_MVAR_CLEAN_info;
}
break;
}
case THUNK:
case THUNK_1_0:
case THUNK_0_1:
case THUNK_1_1:
case THUNK_0_2:
case THUNK_2_0:
{
StgPtr q, end;
end = (StgPtr)((StgThunk *)p)->payload + info->layout.payload.ptrs;
for (q = (StgPtr)((StgThunk *)p)->payload; q < end; q++) {
evacuate((StgClosure **)q);
}
break;
}
case FUN:
case FUN_1_0: // hardly worth specialising these guys
case FUN_0_1:
case FUN_1_1:
case FUN_0_2:
case FUN_2_0:
case CONSTR:
case CONSTR_1_0:
case CONSTR_0_1:
case CONSTR_1_1:
case CONSTR_0_2:
case CONSTR_2_0:
case WEAK:
case PRIM:
case IND_PERM:
{
StgPtr q, end;
end = (StgPtr)((StgClosure *)p)->payload + info->layout.payload.ptrs;
for (q = (StgPtr)((StgClosure *)p)->payload; q < end; q++) {
evacuate((StgClosure **)q);
}
break;
}
case MUT_VAR_CLEAN:
case MUT_VAR_DIRTY: {
StgPtr q = p;
gct->eager_promotion = rtsFalse;
evacuate(&((StgMutVar *)p)->var);
gct->eager_promotion = saved_eager_promotion;
if (gct->failed_to_evac) {
((StgClosure *)q)->header.info = &stg_MUT_VAR_DIRTY_info;
} else {
((StgClosure *)q)->header.info = &stg_MUT_VAR_CLEAN_info;
}
break;
}
case BLOCKING_QUEUE:
{
StgBlockingQueue *bq = (StgBlockingQueue *)p;
gct->eager_promotion = rtsFalse;
evacuate(&bq->bh);
evacuate((StgClosure**)&bq->owner);
evacuate((StgClosure**)&bq->queue);
evacuate((StgClosure**)&bq->link);
gct->eager_promotion = saved_eager_promotion;
if (gct->failed_to_evac) {
bq->header.info = &stg_BLOCKING_QUEUE_DIRTY_info;
} else {
bq->header.info = &stg_BLOCKING_QUEUE_CLEAN_info;
}
break;
}
case THUNK_SELECTOR:
{
StgSelector *s = (StgSelector *)p;
evacuate(&s->selectee);
break;
}
case AP_STACK:
{
StgAP_STACK *ap = (StgAP_STACK *)p;
evacuate(&ap->fun);
scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
p = (StgPtr)ap->payload + ap->size;
break;
}
case PAP:
p = scavenge_PAP((StgPAP *)p);
break;
case AP:
p = scavenge_AP((StgAP *)p);
break;
case ARR_WORDS:
// nothing to follow
break;
case MUT_ARR_PTRS_CLEAN:
case MUT_ARR_PTRS_DIRTY:
{
// We don't eagerly promote objects pointed to by a mutable
// array, but if we find the array only points to objects in
// the same or an older generation, we mark it "clean" and
// avoid traversing it during minor GCs.
gct->eager_promotion = rtsFalse;
scavenge_mut_arr_ptrs((StgMutArrPtrs *)p);
if (gct->failed_to_evac) {
((StgClosure *)p)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
} else {
((StgClosure *)p)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
}
gct->eager_promotion = saved_eager_promotion;
gct->failed_to_evac = rtsTrue;
break;
}
case MUT_ARR_PTRS_FROZEN:
case MUT_ARR_PTRS_FROZEN0:
{
// follow everything
scavenge_mut_arr_ptrs((StgMutArrPtrs *)p);
// If we're going to put this object on the mutable list, then
// set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that.
if (gct->failed_to_evac) {
((StgClosure *)p)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info;
} else {
((StgClosure *)p)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info;
}
break;
}
case TSO:
{
scavengeTSO((StgTSO*)p);
break;
}
case STACK:
{
StgStack *stack = (StgStack*)p;
gct->eager_promotion = rtsFalse;
scavenge_stack(stack->sp, stack->stack + stack->stack_size);
stack->dirty = gct->failed_to_evac;
gct->eager_promotion = saved_eager_promotion;
break;
}
case MUT_PRIM:
{
StgPtr end;
gct->eager_promotion = rtsFalse;
end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
evacuate((StgClosure **)p);
}
gct->eager_promotion = saved_eager_promotion;
gct->failed_to_evac = rtsTrue; // mutable
break;
}
case TREC_CHUNK:
{
StgWord i;
StgTRecChunk *tc = ((StgTRecChunk *) p);
TRecEntry *e = &(tc -> entries[0]);
gct->eager_promotion = rtsFalse;
evacuate((StgClosure **)&tc->prev_chunk);
for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
evacuate((StgClosure **)&e->tvar);
evacuate((StgClosure **)&e->expected_value);
evacuate((StgClosure **)&e->new_value);
}
gct->eager_promotion = saved_eager_promotion;
gct->failed_to_evac = rtsTrue; // mutable
break;
}
case IND:
// IND can happen, for example, when the interpreter allocates
// a gigantic AP closure (more than one block), which ends up
// on the large-object list and then gets updated. See #3424.
case BLACKHOLE:
case IND_STATIC:
evacuate(&((StgInd *)p)->indirectee);
#if 0 && defined(DEBUG)
if (RtsFlags.DebugFlags.gc)
/* Debugging code to print out the size of the thing we just
* promoted
*/
{
StgPtr start = gen->scan;
bdescr *start_bd = gen->scan_bd;
nat size = 0;
scavenge(&gen);
if (start_bd != gen->scan_bd) {
size += (P_)BLOCK_ROUND_UP(start) - start;
start_bd = start_bd->link;
while (start_bd != gen->scan_bd) {
size += BLOCK_SIZE_W;
start_bd = start_bd->link;
}
size += gen->scan -
(P_)BLOCK_ROUND_DOWN(gen->scan);
} else {
size = gen->scan - start;
}
debugBelch("evac IND_OLDGEN: %ld bytes", size * sizeof(W_));
}
#endif
break;
default:
barf("scavenge_one: strange object %d", (int)(info->type));
}
no_luck = gct->failed_to_evac;
gct->failed_to_evac = rtsFalse;
return (no_luck);
}
static void
scavenge_mark_stack(void)
{
StgPtr p, q;
StgInfoTable *info;
rtsBool saved_eager_promotion;
gct->evac_gen_no = oldest_gen->no;
saved_eager_promotion = gct->eager_promotion;
while ((p = pop_mark_stack())) {
ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
info = get_itbl((StgClosure *)p);
q = p;
switch (info->type) {
case MVAR_CLEAN:
case MVAR_DIRTY:
{
StgMVar *mvar = ((StgMVar *)p);
gct->eager_promotion = rtsFalse;
evacuate((StgClosure **)&mvar->head);
evacuate((StgClosure **)&mvar->tail);
evacuate((StgClosure **)&mvar->value);
gct->eager_promotion = saved_eager_promotion;
if (gct->failed_to_evac) {
mvar->header.info = &stg_MVAR_DIRTY_info;
} else {
mvar->header.info = &stg_MVAR_CLEAN_info;
}
break;
}
case FUN_2_0:
scavenge_fun_srt(info);
evacuate(&((StgClosure *)p)->payload[1]);
evacuate(&((StgClosure *)p)->payload[0]);
break;
case THUNK_2_0:
scavenge_thunk_srt(info);
evacuate(&((StgThunk *)p)->payload[1]);
evacuate(&((StgThunk *)p)->payload[0]);
break;
case CONSTR_2_0:
evacuate(&((StgClosure *)p)->payload[1]);
evacuate(&((StgClosure *)p)->payload[0]);
break;
case FUN_1_0:
case FUN_1_1:
scavenge_fun_srt(info);
evacuate(&((StgClosure *)p)->payload[0]);
break;
case THUNK_1_0:
case THUNK_1_1:
scavenge_thunk_srt(info);
evacuate(&((StgThunk *)p)->payload[0]);
break;
case CONSTR_1_0:
case CONSTR_1_1:
evacuate(&((StgClosure *)p)->payload[0]);
break;
case FUN_0_1:
case FUN_0_2:
scavenge_fun_srt(info);
break;
case THUNK_0_1:
case THUNK_0_2:
scavenge_thunk_srt(info);
break;
case CONSTR_0_1:
case CONSTR_0_2:
break;
case FUN:
scavenge_fun_srt(info);
goto gen_obj;
case THUNK:
{
StgPtr end;
scavenge_thunk_srt(info);
end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
evacuate((StgClosure **)p);
}
break;
}
gen_obj:
case CONSTR:
case WEAK:
case PRIM:
{
StgPtr end;
end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
evacuate((StgClosure **)p);
}
break;
}
case BCO: {
StgBCO *bco = (StgBCO *)p;
evacuate((StgClosure **)&bco->instrs);
evacuate((StgClosure **)&bco->literals);
evacuate((StgClosure **)&bco->ptrs);
break;
}
case IND_PERM:
// don't need to do anything here: the only possible case
// is that we're in a 1-space compacting collector, with
// no "old" generation.
break;
case IND:
case BLACKHOLE:
evacuate(&((StgInd *)p)->indirectee);
break;
case MUT_VAR_CLEAN:
case MUT_VAR_DIRTY: {
gct->eager_promotion = rtsFalse;
evacuate(&((StgMutVar *)p)->var);
gct->eager_promotion = saved_eager_promotion;
if (gct->failed_to_evac) {
((StgClosure *)q)->header.info = &stg_MUT_VAR_DIRTY_info;
} else {
((StgClosure *)q)->header.info = &stg_MUT_VAR_CLEAN_info;
}
break;
}
case BLOCKING_QUEUE:
{
StgBlockingQueue *bq = (StgBlockingQueue *)p;
gct->eager_promotion = rtsFalse;
evacuate(&bq->bh);
evacuate((StgClosure**)&bq->owner);
evacuate((StgClosure**)&bq->queue);
evacuate((StgClosure**)&bq->link);
gct->eager_promotion = saved_eager_promotion;
if (gct->failed_to_evac) {
bq->header.info = &stg_BLOCKING_QUEUE_DIRTY_info;
} else {
bq->header.info = &stg_BLOCKING_QUEUE_CLEAN_info;
}
break;
}
case ARR_WORDS:
break;
case THUNK_SELECTOR:
{
StgSelector *s = (StgSelector *)p;
evacuate(&s->selectee);
break;
}
// A chunk of stack saved in a heap object
case AP_STACK:
{
StgAP_STACK *ap = (StgAP_STACK *)p;
evacuate(&ap->fun);
scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
break;
}
case PAP:
scavenge_PAP((StgPAP *)p);
break;
case AP:
scavenge_AP((StgAP *)p);
break;
case MUT_ARR_PTRS_CLEAN:
case MUT_ARR_PTRS_DIRTY:
// follow everything
{
// We don't eagerly promote objects pointed to by a mutable
// array, but if we find the array only points to objects in
// the same or an older generation, we mark it "clean" and
// avoid traversing it during minor GCs.
gct->eager_promotion = rtsFalse;
scavenge_mut_arr_ptrs((StgMutArrPtrs *)p);
if (gct->failed_to_evac) {
((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
} else {
((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
}
gct->eager_promotion = saved_eager_promotion;
gct->failed_to_evac = rtsTrue; // mutable anyhow.
break;
}
case MUT_ARR_PTRS_FROZEN:
case MUT_ARR_PTRS_FROZEN0:
// follow everything
{
StgPtr q = p;
scavenge_mut_arr_ptrs((StgMutArrPtrs *)p);
// If we're going to put this object on the mutable list, then
// set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that.
if (gct->failed_to_evac) {
((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info;
} else {
((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info;
}
break;
}
case TSO:
{
scavengeTSO((StgTSO*)p);
break;
}
case STACK:
{
StgStack *stack = (StgStack*)p;
gct->eager_promotion = rtsFalse;
scavenge_stack(stack->sp, stack->stack + stack->stack_size);
stack->dirty = gct->failed_to_evac;
gct->eager_promotion = saved_eager_promotion;
break;
}
case MUT_PRIM:
{
StgPtr end;
gct->eager_promotion = rtsFalse;
end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
evacuate((StgClosure **)p);
}
gct->eager_promotion = saved_eager_promotion;
gct->failed_to_evac = rtsTrue; // mutable
break;
}
case TREC_CHUNK:
{
StgWord i;
StgTRecChunk *tc = ((StgTRecChunk *) p);
TRecEntry *e = &(tc -> entries[0]);
gct->eager_promotion = rtsFalse;
evacuate((StgClosure **)&tc->prev_chunk);
for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
evacuate((StgClosure **)&e->tvar);
evacuate((StgClosure **)&e->expected_value);
evacuate((StgClosure **)&e->new_value);
}
gct->eager_promotion = saved_eager_promotion;
gct->failed_to_evac = rtsTrue; // mutable
break;
}
default:
barf("scavenge_mark_stack: unimplemented/strange closure type %d @ %p",
info->type, p);
}
if (gct->failed_to_evac) {
gct->failed_to_evac = rtsFalse;
if (gct->evac_gen_no) {
recordMutableGen_GC((StgClosure *)q, gct->evac_gen_no);
}
}
} // while (p = pop_mark_stack())
}
static GNUC_ATTR_HOT void
scavenge_block (bdescr *bd)
{
StgPtr p, q;
StgInfoTable *info;
rtsBool saved_eager_promotion;
gen_workspace *ws;
debugTrace(DEBUG_gc, "scavenging block %p (gen %d) @ %p",
bd->start, bd->gen_no, bd->u.scan);
gct->scan_bd = bd;
gct->evac_gen_no = bd->gen_no;
saved_eager_promotion = gct->eager_promotion;
gct->failed_to_evac = rtsFalse;
ws = &gct->gens[bd->gen->no];
p = bd->u.scan;
// we might be evacuating into the very object that we're
// scavenging, so we have to check the real bd->free pointer each
// time around the loop.
while (p < bd->free || (bd == ws->todo_bd && p < ws->todo_free)) {
ASSERT(bd->link == NULL);
ASSERT(LOOKS_LIKE_CLOSURE_PTR(p));
info = get_itbl((StgClosure *)p);
ASSERT(gct->thunk_selector_depth == 0);
q = p;
switch (info->type) {
case MVAR_CLEAN:
case MVAR_DIRTY:
{
StgMVar *mvar = ((StgMVar *)p);
gct->eager_promotion = rtsFalse;
evacuate((StgClosure **)&mvar->head);
evacuate((StgClosure **)&mvar->tail);
evacuate((StgClosure **)&mvar->value);
gct->eager_promotion = saved_eager_promotion;
if (gct->failed_to_evac) {
mvar->header.info = &stg_MVAR_DIRTY_info;
} else {
mvar->header.info = &stg_MVAR_CLEAN_info;
}
p += sizeofW(StgMVar);
break;
}
case FUN_2_0:
scavenge_fun_srt(info);
evacuate(&((StgClosure *)p)->payload[1]);
evacuate(&((StgClosure *)p)->payload[0]);
p += sizeofW(StgHeader) + 2;
break;
case THUNK_2_0:
scavenge_thunk_srt(info);
evacuate(&((StgThunk *)p)->payload[1]);
evacuate(&((StgThunk *)p)->payload[0]);
p += sizeofW(StgThunk) + 2;
break;
case CONSTR_2_0:
evacuate(&((StgClosure *)p)->payload[1]);
evacuate(&((StgClosure *)p)->payload[0]);
p += sizeofW(StgHeader) + 2;
break;
case THUNK_1_0:
scavenge_thunk_srt(info);
evacuate(&((StgThunk *)p)->payload[0]);
p += sizeofW(StgThunk) + 1;
break;
case FUN_1_0:
scavenge_fun_srt(info);
case CONSTR_1_0:
evacuate(&((StgClosure *)p)->payload[0]);
p += sizeofW(StgHeader) + 1;
break;
case THUNK_0_1:
scavenge_thunk_srt(info);
p += sizeofW(StgThunk) + 1;
break;
case FUN_0_1:
scavenge_fun_srt(info);
case CONSTR_0_1:
p += sizeofW(StgHeader) + 1;
break;
case THUNK_0_2:
scavenge_thunk_srt(info);
p += sizeofW(StgThunk) + 2;
break;
case FUN_0_2:
scavenge_fun_srt(info);
case CONSTR_0_2:
p += sizeofW(StgHeader) + 2;
break;
case THUNK_1_1:
scavenge_thunk_srt(info);
evacuate(&((StgThunk *)p)->payload[0]);
p += sizeofW(StgThunk) + 2;
break;
case FUN_1_1:
scavenge_fun_srt(info);
case CONSTR_1_1:
evacuate(&((StgClosure *)p)->payload[0]);
p += sizeofW(StgHeader) + 2;
break;
case FUN:
scavenge_fun_srt(info);
goto gen_obj;
case THUNK:
{
StgPtr end;
scavenge_thunk_srt(info);
end = (P_)((StgThunk *)p)->payload + info->layout.payload.ptrs;
for (p = (P_)((StgThunk *)p)->payload; p < end; p++) {
evacuate((StgClosure **)p);
}
p += info->layout.payload.nptrs;
break;
}
gen_obj:
case CONSTR:
case WEAK:
case PRIM:
{
StgPtr end;
end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
evacuate((StgClosure **)p);
}
p += info->layout.payload.nptrs;
break;
}
case BCO: {
StgBCO *bco = (StgBCO *)p;
evacuate((StgClosure **)&bco->instrs);
evacuate((StgClosure **)&bco->literals);
evacuate((StgClosure **)&bco->ptrs);
p += bco_sizeW(bco);
break;
}
case IND_PERM:
case BLACKHOLE:
evacuate(&((StgInd *)p)->indirectee);
p += sizeofW(StgInd);
break;
case MUT_VAR_CLEAN:
case MUT_VAR_DIRTY:
gct->eager_promotion = rtsFalse;
evacuate(&((StgMutVar *)p)->var);
gct->eager_promotion = saved_eager_promotion;
if (gct->failed_to_evac) {
((StgClosure *)q)->header.info = &stg_MUT_VAR_DIRTY_info;
} else {
((StgClosure *)q)->header.info = &stg_MUT_VAR_CLEAN_info;
}
p += sizeofW(StgMutVar);
break;
case BLOCKING_QUEUE:
{
StgBlockingQueue *bq = (StgBlockingQueue *)p;
gct->eager_promotion = rtsFalse;
evacuate(&bq->bh);
evacuate((StgClosure**)&bq->owner);
evacuate((StgClosure**)&bq->queue);
evacuate((StgClosure**)&bq->link);
gct->eager_promotion = saved_eager_promotion;
if (gct->failed_to_evac) {
bq->header.info = &stg_BLOCKING_QUEUE_DIRTY_info;
} else {
bq->header.info = &stg_BLOCKING_QUEUE_CLEAN_info;
}
p += sizeofW(StgBlockingQueue);
break;
}
case THUNK_SELECTOR:
{
StgSelector *s = (StgSelector *)p;
evacuate(&s->selectee);
p += THUNK_SELECTOR_sizeW();
break;
}
// A chunk of stack saved in a heap object
case AP_STACK:
{
StgAP_STACK *ap = (StgAP_STACK *)p;
evacuate(&ap->fun);
scavenge_stack((StgPtr)ap->payload, (StgPtr)ap->payload + ap->size);
p = (StgPtr)ap->payload + ap->size;
break;
}
case PAP:
p = scavenge_PAP((StgPAP *)p);
break;
case AP:
p = scavenge_AP((StgAP *)p);
break;
case ARR_WORDS:
// nothing to follow
p += arr_words_sizeW((StgArrWords *)p);
break;
case MUT_ARR_PTRS_CLEAN:
case MUT_ARR_PTRS_DIRTY:
{
// We don't eagerly promote objects pointed to by a mutable
// array, but if we find the array only points to objects in
// the same or an older generation, we mark it "clean" and
// avoid traversing it during minor GCs.
gct->eager_promotion = rtsFalse;
p = scavenge_mut_arr_ptrs((StgMutArrPtrs*)p);
if (gct->failed_to_evac) {
((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_DIRTY_info;
} else {
((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_CLEAN_info;
}
gct->eager_promotion = saved_eager_promotion;
gct->failed_to_evac = rtsTrue; // always put it on the mutable list.
break;
}
case MUT_ARR_PTRS_FROZEN:
case MUT_ARR_PTRS_FROZEN0:
// follow everything
{
p = scavenge_mut_arr_ptrs((StgMutArrPtrs*)p);
// If we're going to put this object on the mutable list, then
// set its info ptr to MUT_ARR_PTRS_FROZEN0 to indicate that.
if (gct->failed_to_evac) {
((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN0_info;
} else {
((StgClosure *)q)->header.info = &stg_MUT_ARR_PTRS_FROZEN_info;
}
break;
}
case TSO:
{
scavengeTSO((StgTSO *)p);
p += sizeofW(StgTSO);
break;
}
case STACK:
{
StgStack *stack = (StgStack*)p;
gct->eager_promotion = rtsFalse;
scavenge_stack(stack->sp, stack->stack + stack->stack_size);
stack->dirty = gct->failed_to_evac;
p += stack_sizeW(stack);
gct->eager_promotion = saved_eager_promotion;
break;
}
case MUT_PRIM:
{
StgPtr end;
gct->eager_promotion = rtsFalse;
end = (P_)((StgClosure *)p)->payload + info->layout.payload.ptrs;
for (p = (P_)((StgClosure *)p)->payload; p < end; p++) {
evacuate((StgClosure **)p);
}
p += info->layout.payload.nptrs;
gct->eager_promotion = saved_eager_promotion;
gct->failed_to_evac = rtsTrue; // mutable
break;
}
case TREC_CHUNK:
{
StgWord i;
StgTRecChunk *tc = ((StgTRecChunk *) p);
TRecEntry *e = &(tc -> entries[0]);
gct->eager_promotion = rtsFalse;
evacuate((StgClosure **)&tc->prev_chunk);
for (i = 0; i < tc -> next_entry_idx; i ++, e++ ) {
evacuate((StgClosure **)&e->tvar);
evacuate((StgClosure **)&e->expected_value);
evacuate((StgClosure **)&e->new_value);
}
gct->eager_promotion = saved_eager_promotion;
gct->failed_to_evac = rtsTrue; // mutable
p += sizeofW(StgTRecChunk);
break;
}
default:
barf("scavenge: unimplemented/strange closure type %d @ %p",
info->type, p);
}
/*
* We need to record the current object on the mutable list if
* (a) It is actually mutable, or
* (b) It contains pointers to a younger generation.
* Case (b) arises if we didn't manage to promote everything that
* the current object points to into the current generation.
*/
if (gct->failed_to_evac) {
gct->failed_to_evac = rtsFalse;
if (bd->gen_no > 0) {
recordMutableGen_GC((StgClosure *)q, bd->gen_no);
}
}
}
if (p > bd->free) {
gct->copied += ws->todo_free - bd->free;
bd->free = p;
}
debugTrace(DEBUG_gc, " scavenged %ld bytes",
(unsigned long)((bd->free - bd->u.scan) * sizeof(W_)));
// update stats: this is a block that has been scavenged
gct->scanned += bd->free - bd->u.scan;
bd->u.scan = bd->free;
if (bd != ws->todo_bd) {
// we're not going to evac any more objects into
// this block, so push it now.
push_scanned_block(bd, ws);
}
gct->scan_bd = NULL;
}
