提交 01b28013 编写于 作者: Y ysr

6883834: ParNew: assert(!_g->to()->is_in_reserved(obj),"Scanning field...

6883834: ParNew: assert(!_g->to()->is_in_reserved(obj),"Scanning field twice?") with LargeObjects tests
Summary: Fixed process_chunk_boundaries(), used for parallel card scanning when using ParNew/CMS, so as to prevent double-scanning, or worse, non-scanning of imprecisely marked objects exceeding parallel chunk size. Made some sizing parameters for parallel card scanning diagnostic, disabled ParallelGCRetainPLAB, and elaborated and clarified some comments.
Reviewed-by: stefank, johnc
上级 00caa507
......@@ -29,13 +29,14 @@
#include "memory/sharedHeap.hpp"
#include "memory/space.inline.hpp"
#include "memory/universe.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/java.hpp"
#include "runtime/mutexLocker.hpp"
#include "runtime/virtualspace.hpp"
void CardTableModRefBS::non_clean_card_iterate_parallel_work(Space* sp, MemRegion mr,
DirtyCardToOopClosure* dcto_cl,
ClearNoncleanCardWrapper* cl,
OopsInGenClosure* cl,
CardTableRS* ct,
int n_threads) {
assert(n_threads > 0, "Error: expected n_threads > 0");
assert((n_threads == 1 && ParallelGCThreads == 0) ||
......@@ -49,14 +50,14 @@ void CardTableModRefBS::non_clean_card_iterate_parallel_work(Space* sp, MemRegio
lowest_non_clean_base_chunk_index,
lowest_non_clean_chunk_size);
int n_strides = n_threads * StridesPerThread;
int n_strides = n_threads * ParGCStridesPerThread;
SequentialSubTasksDone* pst = sp->par_seq_tasks();
pst->set_n_threads(n_threads);
pst->set_n_tasks(n_strides);
int stride = 0;
while (!pst->is_task_claimed(/* reference */ stride)) {
process_stride(sp, mr, stride, n_strides, dcto_cl, cl,
process_stride(sp, mr, stride, n_strides, cl, ct,
lowest_non_clean,
lowest_non_clean_base_chunk_index,
lowest_non_clean_chunk_size);
......@@ -79,13 +80,13 @@ CardTableModRefBS::
process_stride(Space* sp,
MemRegion used,
jint stride, int n_strides,
DirtyCardToOopClosure* dcto_cl,
ClearNoncleanCardWrapper* cl,
OopsInGenClosure* cl,
CardTableRS* ct,
jbyte** lowest_non_clean,
uintptr_t lowest_non_clean_base_chunk_index,
size_t lowest_non_clean_chunk_size) {
// We don't have to go downwards here; it wouldn't help anyway,
// because of parallelism.
// We go from higher to lower addresses here; it wouldn't help that much
// because of the strided parallelism pattern used here.
// Find the first card address of the first chunk in the stride that is
// at least "bottom" of the used region.
......@@ -98,25 +99,35 @@ process_stride(Space* sp,
if ((uintptr_t)stride >= start_chunk_stride_num) {
chunk_card_start = (jbyte*)(start_card +
(stride - start_chunk_stride_num) *
CardsPerStrideChunk);
ParGCCardsPerStrideChunk);
} else {
// Go ahead to the next chunk group boundary, then to the requested stride.
chunk_card_start = (jbyte*)(start_card +
(n_strides - start_chunk_stride_num + stride) *
CardsPerStrideChunk);
ParGCCardsPerStrideChunk);
}
while (chunk_card_start < end_card) {
// We don't have to go downwards here; it wouldn't help anyway,
// because of parallelism. (We take care with "min_done"; see below.)
// Even though we go from lower to higher addresses below, the
// strided parallelism can interleave the actual processing of the
// dirty pages in various ways. For a specific chunk within this
// stride, we take care to avoid double scanning or missing a card
// by suitably initializing the "min_done" field in process_chunk_boundaries()
// below, together with the dirty region extension accomplished in
// DirtyCardToOopClosure::do_MemRegion().
jbyte* chunk_card_end = chunk_card_start + ParGCCardsPerStrideChunk;
// Invariant: chunk_mr should be fully contained within the "used" region.
jbyte* chunk_card_end = chunk_card_start + CardsPerStrideChunk;
MemRegion chunk_mr = MemRegion(addr_for(chunk_card_start),
chunk_card_end >= end_card ?
used.end() : addr_for(chunk_card_end));
assert(chunk_mr.word_size() > 0, "[chunk_card_start > used_end)");
assert(used.contains(chunk_mr), "chunk_mr should be subset of used");
DirtyCardToOopClosure* dcto_cl = sp->new_dcto_cl(cl, precision(),
cl->gen_boundary());
ClearNoncleanCardWrapper clear_cl(dcto_cl, ct);
// Process the chunk.
process_chunk_boundaries(sp,
dcto_cl,
......@@ -126,17 +137,30 @@ process_stride(Space* sp,
lowest_non_clean_base_chunk_index,
lowest_non_clean_chunk_size);
// We want the LNC array updates above in process_chunk_boundaries
// to be visible before any of the card table value changes as a
// result of the dirty card iteration below.
OrderAccess::storestore();
// We do not call the non_clean_card_iterate_serial() version because
// we want to clear the cards, and the ClearNoncleanCardWrapper closure
// itself does the work of finding contiguous dirty ranges of cards to
// process (and clear).
cl->do_MemRegion(chunk_mr);
// we want to clear the cards: clear_cl here does the work of finding
// contiguous dirty ranges of cards to process and clear.
clear_cl.do_MemRegion(chunk_mr);
// Find the next chunk of the stride.
chunk_card_start += CardsPerStrideChunk * n_strides;
chunk_card_start += ParGCCardsPerStrideChunk * n_strides;
}
}
// If you want a talkative process_chunk_boundaries,
// then #define NOISY(x) x
#ifdef NOISY
#error "Encountered a global preprocessor flag, NOISY, which might clash with local definition to follow"
#else
#define NOISY(x)
#endif
void
CardTableModRefBS::
process_chunk_boundaries(Space* sp,
......@@ -147,127 +171,233 @@ process_chunk_boundaries(Space* sp,
uintptr_t lowest_non_clean_base_chunk_index,
size_t lowest_non_clean_chunk_size)
{
// We must worry about the chunk boundaries.
// We must worry about non-array objects that cross chunk boundaries,
// because such objects are both precisely and imprecisely marked:
// .. if the head of such an object is dirty, the entire object
// needs to be scanned, under the interpretation that this
// was an imprecise mark
// .. if the head of such an object is not dirty, we can assume
// precise marking and it's efficient to scan just the dirty
// cards.
// In either case, each scanned reference must be scanned precisely
// once so as to avoid cloning of a young referent. For efficiency,
// our closures depend on this property and do not protect against
// double scans.
// First, set our max_to_do:
HeapWord* max_to_do = NULL;
uintptr_t cur_chunk_index = addr_to_chunk_index(chunk_mr.start());
cur_chunk_index = cur_chunk_index - lowest_non_clean_base_chunk_index;
NOISY(tty->print_cr("===========================================================================");)
NOISY(tty->print_cr(" process_chunk_boundary: Called with [" PTR_FORMAT "," PTR_FORMAT ")",
chunk_mr.start(), chunk_mr.end());)
// First, set "our" lowest_non_clean entry, which would be
// used by the thread scanning an adjoining left chunk with
// a non-array object straddling the mutual boundary.
// Find the object that spans our boundary, if one exists.
// first_block is the block possibly straddling our left boundary.
HeapWord* first_block = sp->block_start(chunk_mr.start());
assert((chunk_mr.start() != used.start()) || (first_block == chunk_mr.start()),
"First chunk should always have a co-initial block");
// Does the block straddle the chunk's left boundary, and is it
// a non-array object?
if (first_block < chunk_mr.start() // first block straddles left bdry
&& sp->block_is_obj(first_block) // first block is an object
&& !(oop(first_block)->is_objArray() // first block is not an array (arrays are precisely dirtied)
|| oop(first_block)->is_typeArray())) {
// Find our least non-clean card, so that a left neighbour
// does not scan an object straddling the mutual boundary
// too far to the right, and attempt to scan a portion of
// that object twice.
jbyte* first_dirty_card = NULL;
jbyte* last_card_of_first_obj =
byte_for(first_block + sp->block_size(first_block) - 1);
jbyte* first_card_of_cur_chunk = byte_for(chunk_mr.start());
jbyte* last_card_of_cur_chunk = byte_for(chunk_mr.last());
jbyte* last_card_to_check =
(jbyte*) MIN2((intptr_t) last_card_of_cur_chunk,
(intptr_t) last_card_of_first_obj);
// Note that this does not need to go beyond our last card
// if our first object completely straddles this chunk.
for (jbyte* cur = first_card_of_cur_chunk;
cur <= last_card_to_check; cur++) {
jbyte val = *cur;
if (card_will_be_scanned(val)) {
first_dirty_card = cur; break;
} else {
assert(!card_may_have_been_dirty(val), "Error");
}
}
if (first_dirty_card != NULL) {
NOISY(tty->print_cr(" LNC: Found a dirty card at " PTR_FORMAT " in current chunk",
first_dirty_card);)
assert(0 <= cur_chunk_index && cur_chunk_index < lowest_non_clean_chunk_size,
"Bounds error.");
assert(lowest_non_clean[cur_chunk_index] == NULL,
"Write exactly once : value should be stable hereafter for this round");
lowest_non_clean[cur_chunk_index] = first_dirty_card;
} NOISY(else {
tty->print_cr(" LNC: Found no dirty card in current chunk; leaving LNC entry NULL");
// In the future, we could have this thread look for a non-NULL value to copy from its
// right neighbour (up to the end of the first object).
if (last_card_of_cur_chunk < last_card_of_first_obj) {
tty->print_cr(" LNC: BEWARE!!! first obj straddles past right end of chunk:\n"
" might be efficient to get value from right neighbour?");
}
})
} else {
// In this case we can help our neighbour by just asking them
// to stop at our first card (even though it may not be dirty).
NOISY(tty->print_cr(" LNC: first block is not a non-array object; setting LNC to first card of current chunk");)
assert(lowest_non_clean[cur_chunk_index] == NULL, "Write once : value should be stable hereafter");
jbyte* first_card_of_cur_chunk = byte_for(chunk_mr.start());
lowest_non_clean[cur_chunk_index] = first_card_of_cur_chunk;
}
NOISY(tty->print_cr(" process_chunk_boundary: lowest_non_clean[" INTPTR_FORMAT "] = " PTR_FORMAT
" which corresponds to the heap address " PTR_FORMAT,
cur_chunk_index, lowest_non_clean[cur_chunk_index],
(lowest_non_clean[cur_chunk_index] != NULL)
? addr_for(lowest_non_clean[cur_chunk_index])
: NULL);)
NOISY(tty->print_cr("---------------------------------------------------------------------------");)
// Next, set our own max_to_do, which will strictly/exclusively bound
// the highest address that we will scan past the right end of our chunk.
HeapWord* max_to_do = NULL;
if (chunk_mr.end() < used.end()) {
// This is not the last chunk in the used region. What is the last
// object?
HeapWord* last_block = sp->block_start(chunk_mr.end());
// This is not the last chunk in the used region.
// What is our last block? We check the first block of
// the next (right) chunk rather than strictly check our last block
// because it's potentially more efficient to do so.
HeapWord* const last_block = sp->block_start(chunk_mr.end());
assert(last_block <= chunk_mr.end(), "In case this property changes.");
if (last_block == chunk_mr.end()
|| !sp->block_is_obj(last_block)) {
if ((last_block == chunk_mr.end()) // our last block does not straddle boundary
|| !sp->block_is_obj(last_block) // last_block isn't an object
|| oop(last_block)->is_objArray() // last_block is an array (precisely marked)
|| oop(last_block)->is_typeArray()) {
max_to_do = chunk_mr.end();
NOISY(tty->print_cr(" process_chunk_boundary: Last block on this card is not a non-array object;\n"
" max_to_do left at " PTR_FORMAT, max_to_do);)
} else {
// It is an object and starts before the end of the current chunk.
assert(last_block < chunk_mr.end(), "Tautology");
// It is a non-array object that straddles the right boundary of this chunk.
// last_obj_card is the card corresponding to the start of the last object
// in the chunk. Note that the last object may not start in
// the chunk.
jbyte* last_obj_card = byte_for(last_block);
if (!card_may_have_been_dirty(*last_obj_card)) {
// The card containing the head is not dirty. Any marks in
jbyte* const last_obj_card = byte_for(last_block);
const jbyte val = *last_obj_card;
if (!card_will_be_scanned(val)) {
assert(!card_may_have_been_dirty(val), "Error");
// The card containing the head is not dirty. Any marks on
// subsequent cards still in this chunk must have been made
// precisely; we can cap processing at the end.
// precisely; we can cap processing at the end of our chunk.
max_to_do = chunk_mr.end();
NOISY(tty->print_cr(" process_chunk_boundary: Head of last object on this card is not dirty;\n"
" max_to_do left at " PTR_FORMAT,
max_to_do);)
} else {
// The last object must be considered dirty, and extends onto the
// following chunk. Look for a dirty card in that chunk that will
// bound our processing.
jbyte* limit_card = NULL;
size_t last_block_size = sp->block_size(last_block);
jbyte* last_card_of_last_obj =
const size_t last_block_size = sp->block_size(last_block);
jbyte* const last_card_of_last_obj =
byte_for(last_block + last_block_size - 1);
jbyte* first_card_of_next_chunk = byte_for(chunk_mr.end());
jbyte* const first_card_of_next_chunk = byte_for(chunk_mr.end());
// This search potentially goes a long distance looking
// for the next card that will be scanned. For example,
// an object that is an array of primitives will not
// have any cards covering regions interior to the array
// that will need to be scanned. The scan can be terminated
// at the last card of the next chunk. That would leave
// limit_card as NULL and would result in "max_to_do"
// being set with the LNC value or with the end
// of the last block.
jbyte* last_card_of_next_chunk = first_card_of_next_chunk +
CardsPerStrideChunk;
assert(byte_for(chunk_mr.end()) - byte_for(chunk_mr.start())
== CardsPerStrideChunk, "last card of next chunk may be wrong");
jbyte* last_card_to_check = (jbyte*) MIN2(last_card_of_last_obj,
last_card_of_next_chunk);
// for the next card that will be scanned, terminating
// at the end of the last_block, if no earlier dirty card
// is found.
assert(byte_for(chunk_mr.end()) - byte_for(chunk_mr.start()) == ParGCCardsPerStrideChunk,
"last card of next chunk may be wrong");
for (jbyte* cur = first_card_of_next_chunk;
cur <= last_card_to_check; cur++) {
if (card_will_be_scanned(*cur)) {
cur <= last_card_of_last_obj; cur++) {
const jbyte val = *cur;
if (card_will_be_scanned(val)) {
NOISY(tty->print_cr(" Found a non-clean card " PTR_FORMAT " with value 0x%x",
cur, (int)val);)
limit_card = cur; break;
} else {
assert(!card_may_have_been_dirty(val), "Error: card can't be skipped");
}
}
assert(0 <= cur_chunk_index+1 &&
cur_chunk_index+1 < lowest_non_clean_chunk_size,
"Bounds error.");
// LNC for the next chunk
jbyte* lnc_card = lowest_non_clean[cur_chunk_index+1];
if (limit_card == NULL) {
limit_card = lnc_card;
}
if (limit_card != NULL) {
if (lnc_card != NULL) {
limit_card = (jbyte*)MIN2((intptr_t)limit_card,
(intptr_t)lnc_card);
}
max_to_do = addr_for(limit_card);
assert(limit_card != NULL && max_to_do != NULL, "Error");
NOISY(tty->print_cr(" process_chunk_boundary: Found a dirty card at " PTR_FORMAT
" max_to_do set at " PTR_FORMAT " which is before end of last block in chunk: "
PTR_FORMAT " + " PTR_FORMAT " = " PTR_FORMAT,
limit_card, max_to_do, last_block, last_block_size, (last_block+last_block_size));)
} else {
// The following is a pessimistic value, because it's possible
// that a dirty card on a subsequent chunk has been cleared by
// the time we get to look at it; we'll correct for that further below,
// using the LNC array which records the least non-clean card
// before cards were cleared in a particular chunk.
limit_card = last_card_of_last_obj;
max_to_do = last_block + last_block_size;
assert(limit_card != NULL && max_to_do != NULL, "Error");
NOISY(tty->print_cr(" process_chunk_boundary: Found no dirty card before end of last block in chunk\n"
" Setting limit_card to " PTR_FORMAT
" and max_to_do " PTR_FORMAT " + " PTR_FORMAT " = " PTR_FORMAT,
limit_card, last_block, last_block_size, max_to_do);)
}
assert(0 < cur_chunk_index+1 && cur_chunk_index+1 < lowest_non_clean_chunk_size,
"Bounds error.");
// It is possible that a dirty card for the last object may have been
// cleared before we had a chance to examine it. In that case, the value
// will have been logged in the LNC for that chunk.
// We need to examine as many chunks to the right as this object
// covers.
const uintptr_t last_chunk_index_to_check = addr_to_chunk_index(last_block + last_block_size - 1)
- lowest_non_clean_base_chunk_index;
DEBUG_ONLY(const uintptr_t last_chunk_index = addr_to_chunk_index(used.end())
- lowest_non_clean_base_chunk_index;)
assert(last_chunk_index_to_check <= last_chunk_index,
err_msg("Out of bounds: last_chunk_index_to_check " INTPTR_FORMAT
" exceeds last_chunk_index " INTPTR_FORMAT,
last_chunk_index_to_check, last_chunk_index));
for (uintptr_t lnc_index = cur_chunk_index + 1;
lnc_index <= last_chunk_index_to_check;
lnc_index++) {
jbyte* lnc_card = lowest_non_clean[lnc_index];
if (lnc_card != NULL) {
// we can stop at the first non-NULL entry we find
if (lnc_card <= limit_card) {
NOISY(tty->print_cr(" process_chunk_boundary: LNC card " PTR_FORMAT " is lower than limit_card " PTR_FORMAT,
" max_to_do will be lowered to " PTR_FORMAT " from " PTR_FORMAT,
lnc_card, limit_card, addr_for(lnc_card), max_to_do);)
limit_card = lnc_card;
max_to_do = addr_for(limit_card);
assert(limit_card != NULL && max_to_do != NULL, "Error");
}
// In any case, we break now
break;
} // else continue to look for a non-NULL entry if any
}
assert(limit_card != NULL && max_to_do != NULL, "Error");
}
assert(max_to_do != NULL, "OOPS!");
assert(max_to_do != NULL, "OOPS 1 !");
}
assert(max_to_do != NULL, "OOPS 2!");
} else {
max_to_do = used.end();
NOISY(tty->print_cr(" process_chunk_boundary: Last chunk of this space;\n"
" max_to_do left at " PTR_FORMAT,
max_to_do);)
}
assert(max_to_do != NULL, "OOPS 3!");
// Now we can set the closure we're using so it doesn't to beyond
// max_to_do.
dcto_cl->set_min_done(max_to_do);
#ifndef PRODUCT
dcto_cl->set_last_bottom(max_to_do);
#endif
// Now we set *our" lowest_non_clean entry.
// Find the object that spans our boundary, if one exists.
// Nothing to do on the first chunk.
if (chunk_mr.start() > used.start()) {
// first_block is the block possibly spanning the chunk start
HeapWord* first_block = sp->block_start(chunk_mr.start());
// Does the block span the start of the chunk and is it
// an object?
if (first_block < chunk_mr.start() &&
sp->block_is_obj(first_block)) {
jbyte* first_dirty_card = NULL;
jbyte* last_card_of_first_obj =
byte_for(first_block + sp->block_size(first_block) - 1);
jbyte* first_card_of_cur_chunk = byte_for(chunk_mr.start());
jbyte* last_card_of_cur_chunk = byte_for(chunk_mr.last());
jbyte* last_card_to_check =
(jbyte*) MIN2((intptr_t) last_card_of_cur_chunk,
(intptr_t) last_card_of_first_obj);
for (jbyte* cur = first_card_of_cur_chunk;
cur <= last_card_to_check; cur++) {
if (card_will_be_scanned(*cur)) {
first_dirty_card = cur; break;
}
}
if (first_dirty_card != NULL) {
assert(0 <= cur_chunk_index &&
cur_chunk_index < lowest_non_clean_chunk_size,
"Bounds error.");
lowest_non_clean[cur_chunk_index] = first_dirty_card;
}
}
}
NOISY(tty->print_cr("===========================================================================\n");)
}
#undef NOISY
void
CardTableModRefBS::
get_LNC_array_for_space(Space* sp,
......@@ -283,8 +413,8 @@ get_LNC_array_for_space(Space* sp,
// LNC array for the covered region. Any later expansion can't affect
// the used_at_save_marks region.
// (I observed a bug in which the first thread to execute this would
// resize, and then it would cause "expand_and_allocates" that would
// Increase the number of chunks in the covered region. Then a second
// resize, and then it would cause "expand_and_allocate" that would
// increase the number of chunks in the covered region. Then a second
// thread would come and execute this, see that the size didn't match,
// and free and allocate again. So the first thread would be using a
// freed "_lowest_non_clean" array.)
......
......@@ -77,7 +77,23 @@ inline void ParScanClosure::do_oop_work(T* p,
if (!oopDesc::is_null(heap_oop)) {
oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
if ((HeapWord*)obj < _boundary) {
assert(!_g->to()->is_in_reserved(obj), "Scanning field twice?");
#ifndef PRODUCT
if (_g->to()->is_in_reserved(obj)) {
tty->print_cr("Scanning field (" PTR_FORMAT ") twice?", p);
GenCollectedHeap* gch = (GenCollectedHeap*)Universe::heap();
Space* sp = gch->space_containing(p);
oop obj = oop(sp->block_start(p));
assert((HeapWord*)obj < (HeapWord*)p, "Error");
tty->print_cr("Object: " PTR_FORMAT, obj);
tty->print_cr("-------");
obj->print();
tty->print_cr("-----");
tty->print_cr("Heap:");
tty->print_cr("-----");
gch->print();
ShouldNotReachHere();
}
#endif
// OK, we need to ensure that it is copied.
// We read the klass and mark in this order, so that we can reliably
// get the size of the object: if the mark we read is not a
......
......@@ -455,25 +455,29 @@ bool CardTableModRefBS::mark_card_deferred(size_t card_index) {
return true;
}
void CardTableModRefBS::non_clean_card_iterate_possibly_parallel(Space* sp,
MemRegion mr,
DirtyCardToOopClosure* dcto_cl,
ClearNoncleanCardWrapper* cl) {
OopsInGenClosure* cl,
CardTableRS* ct) {
if (!mr.is_empty()) {
int n_threads = SharedHeap::heap()->n_par_threads();
if (n_threads > 0) {
#ifndef SERIALGC
non_clean_card_iterate_parallel_work(sp, mr, dcto_cl, cl, n_threads);
non_clean_card_iterate_parallel_work(sp, mr, cl, ct, n_threads);
#else // SERIALGC
fatal("Parallel gc not supported here.");
#endif // SERIALGC
} else {
// We do not call the non_clean_card_iterate_serial() version below because
// we want to clear the cards (which non_clean_card_iterate_serial() does not
// do for us), and the ClearNoncleanCardWrapper closure itself does the work
// of finding contiguous dirty ranges of cards to process (and clear).
cl->do_MemRegion(mr);
// do for us): clear_cl here does the work of finding contiguous dirty ranges
// of cards to process and clear.
DirtyCardToOopClosure* dcto_cl = sp->new_dcto_cl(cl, precision(),
cl->gen_boundary());
ClearNoncleanCardWrapper clear_cl(dcto_cl, ct);
clear_cl.do_MemRegion(mr);
}
}
}
......
......@@ -173,18 +173,17 @@ class CardTableModRefBS: public ModRefBarrierSet {
// A variant of the above that will operate in a parallel mode if
// worker threads are available, and clear the dirty cards as it
// processes them.
// ClearNoncleanCardWrapper cl must wrap the DirtyCardToOopClosure dcto_cl,
// which may itself be modified by the method.
// XXX ??? MemRegionClosure above vs OopsInGenClosure below XXX
// XXX some new_dcto_cl's take OopClosure's, plus as above there are
// some MemRegionClosures. Clean this up everywhere. XXX
void non_clean_card_iterate_possibly_parallel(Space* sp, MemRegion mr,
DirtyCardToOopClosure* dcto_cl,
ClearNoncleanCardWrapper* cl);
OopsInGenClosure* cl, CardTableRS* ct);
private:
// Work method used to implement non_clean_card_iterate_possibly_parallel()
// above in the parallel case.
void non_clean_card_iterate_parallel_work(Space* sp, MemRegion mr,
DirtyCardToOopClosure* dcto_cl,
ClearNoncleanCardWrapper* cl,
OopsInGenClosure* cl, CardTableRS* ct,
int n_threads);
protected:
......@@ -198,11 +197,6 @@ class CardTableModRefBS: public ModRefBarrierSet {
// *** Support for parallel card scanning.
enum SomeConstantsForParallelism {
StridesPerThread = 2,
CardsPerStrideChunk = 256
};
// This is an array, one element per covered region of the card table.
// Each entry is itself an array, with one element per chunk in the
// covered region. Each entry of these arrays is the lowest non-clean
......@@ -235,7 +229,7 @@ class CardTableModRefBS: public ModRefBarrierSet {
// covers the given address.
uintptr_t addr_to_chunk_index(const void* addr) {
uintptr_t card = (uintptr_t) byte_for(addr);
return card / CardsPerStrideChunk;
return card / ParGCCardsPerStrideChunk;
}
// Apply cl, which must either itself apply dcto_cl or be dcto_cl,
......@@ -243,8 +237,8 @@ class CardTableModRefBS: public ModRefBarrierSet {
void process_stride(Space* sp,
MemRegion used,
jint stride, int n_strides,
DirtyCardToOopClosure* dcto_cl,
ClearNoncleanCardWrapper* cl,
OopsInGenClosure* cl,
CardTableRS* ct,
jbyte** lowest_non_clean,
uintptr_t lowest_non_clean_base_chunk_index,
size_t lowest_non_clean_chunk_size);
......@@ -482,7 +476,7 @@ public:
void verify_dirty_region(MemRegion mr) PRODUCT_RETURN;
static size_t par_chunk_heapword_alignment() {
return CardsPerStrideChunk * card_size_in_words;
return ParGCCardsPerStrideChunk * card_size_in_words;
}
};
......
......@@ -162,7 +162,7 @@ inline bool ClearNoncleanCardWrapper::clear_card_serial(jbyte* entry) {
}
ClearNoncleanCardWrapper::ClearNoncleanCardWrapper(
MemRegionClosure* dirty_card_closure, CardTableRS* ct) :
DirtyCardToOopClosure* dirty_card_closure, CardTableRS* ct) :
_dirty_card_closure(dirty_card_closure), _ct(ct) {
_is_par = (SharedHeap::heap()->n_par_threads() > 0);
}
......@@ -246,10 +246,6 @@ void CardTableRS::write_ref_field_gc_par(void* field, oop new_val) {
void CardTableRS::younger_refs_in_space_iterate(Space* sp,
OopsInGenClosure* cl) {
DirtyCardToOopClosure* dcto_cl = sp->new_dcto_cl(cl, _ct_bs->precision(),
cl->gen_boundary());
ClearNoncleanCardWrapper clear_cl(dcto_cl, this);
const MemRegion urasm = sp->used_region_at_save_marks();
#ifdef ASSERT
// Convert the assertion check to a warning if we are running
......@@ -275,10 +271,10 @@ void CardTableRS::younger_refs_in_space_iterate(Space* sp,
if (!urasm.equals(urasm2)) {
warning("CMS+ParNew: Flickering used_region_at_save_marks()!!");
}
ShouldNotReachHere();
}
#endif
_ct_bs->non_clean_card_iterate_possibly_parallel(sp, urasm,
dcto_cl, &clear_cl);
_ct_bs->non_clean_card_iterate_possibly_parallel(sp, urasm, cl, this);
}
void CardTableRS::clear_into_younger(Generation* gen, bool clear_perm) {
......
......@@ -31,7 +31,6 @@
class Space;
class OopsInGenClosure;
class DirtyCardToOopClosure;
// This kind of "GenRemSet" uses a card table both as shared data structure
// for a mod ref barrier set and for the rem set information.
......@@ -167,7 +166,7 @@ public:
};
class ClearNoncleanCardWrapper: public MemRegionClosure {
MemRegionClosure* _dirty_card_closure;
DirtyCardToOopClosure* _dirty_card_closure;
CardTableRS* _ct;
bool _is_par;
private:
......@@ -179,7 +178,7 @@ private:
inline bool clear_card_parallel(jbyte* entry);
public:
ClearNoncleanCardWrapper(MemRegionClosure* dirty_card_closure, CardTableRS* ct);
ClearNoncleanCardWrapper(DirtyCardToOopClosure* dirty_card_closure, CardTableRS* ct);
void do_MemRegion(MemRegion mr);
};
......
......@@ -97,6 +97,14 @@ void DirtyCardToOopClosure::walk_mem_region(MemRegion mr,
}
}
// We get called with "mr" representing the dirty region
// that we want to process. Because of imprecise marking,
// we may need to extend the incoming "mr" to the right,
// and scan more. However, because we may already have
// scanned some of that extended region, we may need to
// trim its right-end back some so we do not scan what
// we (or another worker thread) may already have scanned
// or planning to scan.
void DirtyCardToOopClosure::do_MemRegion(MemRegion mr) {
// Some collectors need to do special things whenever their dirty
......@@ -148,7 +156,7 @@ void DirtyCardToOopClosure::do_MemRegion(MemRegion mr) {
// e.g. the dirty card region is entirely in a now free object
// -- something that could happen with a concurrent sweeper.
bottom = MIN2(bottom, top);
mr = MemRegion(bottom, top);
MemRegion extended_mr = MemRegion(bottom, top);
assert(bottom <= top &&
(_precision != CardTableModRefBS::ObjHeadPreciseArray ||
_min_done == NULL ||
......@@ -156,8 +164,8 @@ void DirtyCardToOopClosure::do_MemRegion(MemRegion mr) {
"overlap!");
// Walk the region if it is not empty; otherwise there is nothing to do.
if (!mr.is_empty()) {
walk_mem_region(mr, bottom_obj, top);
if (!extended_mr.is_empty()) {
walk_mem_region(extended_mr, bottom_obj, top);
}
// An idempotent closure might be applied in any order, so we don't
......
......@@ -1460,8 +1460,10 @@ class CommandLineFlags {
product(intx, ParallelGCBufferWastePct, 10, \
"wasted fraction of parallel allocation buffer.") \
\
product(bool, ParallelGCRetainPLAB, true, \
"Retain parallel allocation buffers across scavenges.") \
diagnostic(bool, ParallelGCRetainPLAB, false, \
"Retain parallel allocation buffers across scavenges; " \
" -- disabled because this currently conflicts with " \
" parallel card scanning under certain conditions ") \
\
product(intx, TargetPLABWastePct, 10, \
"target wasted space in last buffer as pct of overall allocation")\
......@@ -1495,6 +1497,14 @@ class CommandLineFlags {
product(uintx, ParGCDesiredObjsFromOverflowList, 20, \
"The desired number of objects to claim from the overflow list") \
\
diagnostic(intx, ParGCStridesPerThread, 2, \
"The number of strides per worker thread that we divide up the " \
"card table scanning work into") \
\
diagnostic(intx, ParGCCardsPerStrideChunk, 256, \
"The number of cards in each chunk of the parallel chunks used " \
"during card table scanning") \
\
product(uintx, CMSParPromoteBlocksToClaim, 16, \
"Number of blocks to attempt to claim when refilling CMS LAB for "\
"parallel GC.") \
......
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