PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
void CardTableModRefBS::non_clean_card_iterate_parallel_work(Space* sp, MemRegion mr,
OopsInGenClosure* cl,
CardTableRS* ct,
int n_threads) {
assert(n_threads > 0, "Error: expected n_threads > 0");
assert((n_threads == 1 && ParallelGCThreads == 0) ||
n_threads <= (int)ParallelGCThreads,
"# worker threads != # requested!");
assert(!Thread::current()->is_VM_thread() || (n_threads == 1), "There is only 1 VM thread");
assert(UseDynamicNumberOfGCThreads ||
!FLAG_IS_DEFAULT(ParallelGCThreads) ||
n_threads == (int)ParallelGCThreads,
"# worker threads != # requested!");
// Make sure the LNC array is valid for the space.
jbyte** lowest_non_clean;
uintptr_t lowest_non_clean_base_chunk_index;
size_t lowest_non_clean_chunk_size;
get_LNC_array_for_space(sp, lowest_non_clean,
lowest_non_clean_base_chunk_index,
lowest_non_clean_chunk_size);
uint n_strides = n_threads * ParGCStridesPerThread;
SequentialSubTasksDone* pst = sp->par_seq_tasks();
// Sets the condition for completion of the subtask (how many threads
// need to finish in order to be done).
pst->set_n_threads(n_threads);
pst->set_n_tasks(n_strides);
uint stride = 0;
while (!pst->is_task_claimed(/* reference */ stride)) {
process_stride(sp, mr, stride, n_strides, cl, ct,
lowest_non_clean,
lowest_non_clean_base_chunk_index,
lowest_non_clean_chunk_size);
}
if (pst->all_tasks_completed()) {
// Clear lowest_non_clean array for next time.
intptr_t first_chunk_index = addr_to_chunk_index(mr.start());
uintptr_t last_chunk_index = addr_to_chunk_index(mr.last());
for (uintptr_t ch = first_chunk_index; ch <= last_chunk_index; ch++) {
intptr_t ind = ch - lowest_non_clean_base_chunk_index;
assert(0 <= ind && ind < (intptr_t)lowest_non_clean_chunk_size,
"Bounds error");
lowest_non_clean[ind] = NULL;
}
}
}
void
CardTableModRefBS::
process_chunk_boundaries(Space* sp,
DirtyCardToOopClosure* dcto_cl,
MemRegion chunk_mr,
MemRegion used,
jbyte** lowest_non_clean,
uintptr_t lowest_non_clean_base_chunk_index,
size_t lowest_non_clean_chunk_size)
{
// 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.
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("===========================================================================");)
void
CardTableModRefBS::
process_stride(Space* sp,
MemRegion used,
jint stride, int n_strides,
DirtyCardToOopClosure* dcto_cl,
MemRegionClosure* cl,
bool clear,
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.
// Find the first card address of the first chunk in the stride that is
// at least "bottom" of the used region.
jbyte* start_card = byte_for(used.start());
jbyte* end_card = byte_after(used.last());
uintptr_t start_chunk = addr_to_chunk_index(used.start());
uintptr_t start_chunk_stride_num = start_chunk % n_strides;
jbyte* chunk_card_start;
if ((uintptr_t)stride >= start_chunk_stride_num) {
chunk_card_start = (jbyte*)(start_card +
(stride - start_chunk_stride_num) *
CardsPerStrideChunk);
} 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);
}
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.)
// 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");
// Process the chunk.
process_chunk_boundaries(sp,
dcto_cl,
chunk_mr,
used,
lowest_non_clean,
lowest_non_clean_base_chunk_index,
lowest_non_clean_chunk_size);
non_clean_card_iterate_work(chunk_mr, cl, clear);
// Find the next chunk of the stride.
chunk_card_start += CardsPerStrideChunk * n_strides;
}
}
void CardTableModRefBSForCTRS::
non_clean_card_iterate_parallel_work(Space* sp, MemRegion mr,
OopsInGenClosure* cl,
CardTableRS* ct,
uint n_threads) {
assert(n_threads > 0, "expected n_threads > 0");
assert(n_threads <= ParallelGCThreads,
err_msg("n_threads: %u > ParallelGCThreads: %u", n_threads, ParallelGCThreads));
// Make sure the LNC array is valid for the space.
jbyte** lowest_non_clean;
uintptr_t lowest_non_clean_base_chunk_index;
size_t lowest_non_clean_chunk_size;
get_LNC_array_for_space(sp, lowest_non_clean,
lowest_non_clean_base_chunk_index,
lowest_non_clean_chunk_size);
uint n_strides = n_threads * ParGCStridesPerThread;
SequentialSubTasksDone* pst = sp->par_seq_tasks();
// Sets the condition for completion of the subtask (how many threads
// need to finish in order to be done).
pst->set_n_threads(n_threads);
pst->set_n_tasks(n_strides);
uint stride = 0;
while (!pst->is_task_claimed(/* reference */ stride)) {
process_stride(sp, mr, stride, n_strides,
cl, ct,
lowest_non_clean,
lowest_non_clean_base_chunk_index,
lowest_non_clean_chunk_size);
}
if (pst->all_tasks_completed()) {
// Clear lowest_non_clean array for next time.
intptr_t first_chunk_index = addr_to_chunk_index(mr.start());
uintptr_t last_chunk_index = addr_to_chunk_index(mr.last());
for (uintptr_t ch = first_chunk_index; ch <= last_chunk_index; ch++) {
intptr_t ind = ch - lowest_non_clean_base_chunk_index;
assert(0 <= ind && ind < (intptr_t)lowest_non_clean_chunk_size,
"Bounds error");
lowest_non_clean[ind] = NULL;
}
}
}
void
CardTableModRefBS::
get_LNC_array_for_space(Space* sp,
jbyte**& lowest_non_clean,
uintptr_t& lowest_non_clean_base_chunk_index,
size_t& lowest_non_clean_chunk_size) {
int i = find_covering_region_containing(sp->bottom());
MemRegion covered = _covered[i];
size_t n_chunks = chunks_to_cover(covered);
// Only the first thread to obtain the lock will resize the
// 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
// 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.)
// Do a dirty read here. If we pass the conditional then take the rare
// event lock and do the read again in case some other thread had already
// succeeded and done the resize.
int cur_collection = Universe::heap()->total_collections();
if (_last_LNC_resizing_collection[i] != cur_collection) {
MutexLocker x(ParGCRareEvent_lock);
if (_last_LNC_resizing_collection[i] != cur_collection) {
if (_lowest_non_clean[i] == NULL ||
n_chunks != _lowest_non_clean_chunk_size[i]) {
// Should we delete the old?
if (_lowest_non_clean[i] != NULL) {
assert(n_chunks != _lowest_non_clean_chunk_size[i],
"logical consequence");
FREE_C_HEAP_ARRAY(CardPtr, _lowest_non_clean[i]);
_lowest_non_clean[i] = NULL;
}
// Now allocate a new one if necessary.
if (_lowest_non_clean[i] == NULL) {
_lowest_non_clean[i] = NEW_C_HEAP_ARRAY(CardPtr, n_chunks);
_lowest_non_clean_chunk_size[i] = n_chunks;
_lowest_non_clean_base_chunk_index[i] = addr_to_chunk_index(covered.start());
for (int j = 0; j < (int)n_chunks; j++)
_lowest_non_clean[i][j] = NULL;
}
}
_last_LNC_resizing_collection[i] = cur_collection;
}
}
// In any case, now do the initialization.
lowest_non_clean = _lowest_non_clean[i];
lowest_non_clean_base_chunk_index = _lowest_non_clean_base_chunk_index[i];
lowest_non_clean_chunk_size = _lowest_non_clean_chunk_size[i];
}
void CardTableModRefBS::par_non_clean_card_iterate_work(Space* sp, MemRegion mr,
DirtyCardToOopClosure* dcto_cl,
MemRegionClosure* cl,
bool clear,
int n_threads) {
if (n_threads > 0) {
assert((n_threads == 1 && ParallelGCThreads == 0) ||
n_threads <= (int)ParallelGCThreads,
"# worker threads != # requested!");
// Make sure the LNC array is valid for the space.
jbyte** lowest_non_clean;
uintptr_t lowest_non_clean_base_chunk_index;
size_t lowest_non_clean_chunk_size;
get_LNC_array_for_space(sp, lowest_non_clean,
lowest_non_clean_base_chunk_index,
lowest_non_clean_chunk_size);
int n_strides = n_threads * StridesPerThread;
SequentialSubTasksDone* pst = sp->par_seq_tasks();
pst->set_par_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, clear,
lowest_non_clean,
lowest_non_clean_base_chunk_index,
lowest_non_clean_chunk_size);
}
if (pst->all_tasks_completed()) {
// Clear lowest_non_clean array for next time.
intptr_t first_chunk_index = addr_to_chunk_index(mr.start());
uintptr_t last_chunk_index = addr_to_chunk_index(mr.last());
for (uintptr_t ch = first_chunk_index; ch <= last_chunk_index; ch++) {
intptr_t ind = ch - lowest_non_clean_base_chunk_index;
assert(0 <= ind && ind < (intptr_t)lowest_non_clean_chunk_size,
"Bounds error");
lowest_non_clean[ind] = NULL;
}
}
}
}
void
CardTableModRefBS::
process_stride(Space* sp,
MemRegion used,
jint stride, int n_strides,
OopsInGenClosure* cl,
CardTableRS* ct,
jbyte** lowest_non_clean,
uintptr_t lowest_non_clean_base_chunk_index,
size_t lowest_non_clean_chunk_size) {
// 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.
jbyte* start_card = byte_for(used.start());
jbyte* end_card = byte_after(used.last());
uintptr_t start_chunk = addr_to_chunk_index(used.start());
uintptr_t start_chunk_stride_num = start_chunk % n_strides;
jbyte* chunk_card_start;
if ((uintptr_t)stride >= start_chunk_stride_num) {
chunk_card_start = (jbyte*)(start_card +
(stride - start_chunk_stride_num) *
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) *
ParGCCardsPerStrideChunk);
}
while (chunk_card_start < end_card) {
// 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.
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,
chunk_mr,
used,
lowest_non_clean,
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: 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 += ParGCCardsPerStrideChunk * n_strides;
}
}
void
CardTableModRefBS::
process_chunk_boundaries(Space* sp,
DirtyCardToOopClosure* dcto_cl,
MemRegion chunk_mr,
MemRegion used,
jbyte** lowest_non_clean,
uintptr_t lowest_non_clean_base_chunk_index,
size_t lowest_non_clean_chunk_size)
{
// We must worry about the chunk boundaries.
// 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;
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());
assert(last_block <= chunk_mr.end(), "In case this property changes.");
if (last_block == chunk_mr.end()
|| !sp->block_is_obj(last_block)) {
max_to_do = chunk_mr.end();
} else {
// It is an object and starts before the end of the current 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
// subsequent cards still in this chunk must have been made
// precisely; we can cap processing at the end.
max_to_do = chunk_mr.end();
} 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 =
byte_for(last_block + last_block_size - 1);
jbyte* 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 (jbyte* cur = first_card_of_next_chunk;
cur <= last_card_to_check; cur++) {
if (card_will_be_scanned(*cur)) {
limit_card = cur; break;
}
}
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);
} else {
max_to_do = last_block + last_block_size;
}
}
}
assert(max_to_do != NULL, "OOPS!");
} else {
max_to_do = used.end();
}
// 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;
}
}
}
}
