void CardTableRS::younger_refs_in_space_iterate(Space* sp,
OopsInGenClosure* cl) {
const MemRegion urasm = sp->used_region_at_save_marks();
#ifdef ASSERT
// Convert the assertion check to a warning if we are running
// CMS+ParNew until related bug is fixed.
MemRegion ur = sp->used_region();
assert(ur.contains(urasm) || (UseConcMarkSweepGC && UseParNewGC),
err_msg("Did you forget to call save_marks()? "
"[" PTR_FORMAT ", " PTR_FORMAT ") is not contained in "
"[" PTR_FORMAT ", " PTR_FORMAT ")",
urasm.start(), urasm.end(), ur.start(), ur.end()));
// In the case of CMS+ParNew, issue a warning
if (!ur.contains(urasm)) {
assert(UseConcMarkSweepGC && UseParNewGC, "Tautology: see assert above");
warning("CMS+ParNew: Did you forget to call save_marks()? "
"[" PTR_FORMAT ", " PTR_FORMAT ") is not contained in "
"[" PTR_FORMAT ", " PTR_FORMAT ")",
urasm.start(), urasm.end(), ur.start(), ur.end());
MemRegion ur2 = sp->used_region();
MemRegion urasm2 = sp->used_region_at_save_marks();
if (!ur.equals(ur2)) {
warning("CMS+ParNew: Flickering used_region()!!");
}
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, cl, this);
}
void ObjArrayKlass::oop_oop_iterate_elements_bounded(objArrayOop a, OopClosureType* closure, MemRegion mr) {
if (UseCompressedOops) {
oop_oop_iterate_elements_specialized_bounded<nv, narrowOop>(a, closure, mr.start(), mr.end());
} else {
oop_oop_iterate_elements_specialized_bounded<nv, oop>(a, closure, mr.start(), mr.end());
}
}
void SharedHeap::fill_region_with_object(MemRegion mr) {
// Disable allocation events, since this isn't a "real" allocation.
JVMPIAllocEventDisabler dis;
size_t word_size = mr.word_size();
size_t aligned_array_header_size =
align_object_size(typeArrayOopDesc::header_size(T_INT));
if (word_size >= aligned_array_header_size) {
const size_t array_length =
pointer_delta(mr.end(), mr.start()) -
typeArrayOopDesc::header_size(T_INT);
const size_t array_length_words =
array_length * (HeapWordSize/sizeof(jint));
post_allocation_setup_array(Universe::intArrayKlassObj(),
mr.start(),
mr.word_size(),
(int)array_length_words);
#ifdef ASSERT
HeapWord* elt_words = (mr.start() + typeArrayOopDesc::header_size(T_INT));
Memory::set_words(elt_words, array_length, 0xDEAFBABE);
#endif
} else {
assert(word_size == (size_t)oopDesc::header_size(), "Unaligned?");
post_allocation_setup_obj(SystemDictionary::object_klass(),
mr.start(),
mr.word_size());
}
}
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 CardTableRS::clear_MemRegion(MemRegion mr) {
jbyte* cur = byte_for(mr.start());
jbyte* last = byte_after(mr.last());
assert(addr_for(cur) == mr.start(), "region must be card aligned");
while (cur < last) {
*cur = CardTableModRefBS::clean_card;
cur++;
}
}
// The buffer comes with its own BOT, with a shared (obviously) underlying
// BlockOffsetSharedArray. We manipulate this BOT in the normal way
// as we would for any contiguous space. However, on accasion we
// need to do some buffer surgery at the extremities before we
// start using the body of the buffer for allocations. Such surgery
// (as explained elsewhere) is to prevent allocation on a card that
// is in the process of being walked concurrently by another GC thread.
// When such surgery happens at a point that is far removed (to the
// right of the current allocation point, top), we use the "contig"
// parameter below to directly manipulate the shared array without
// modifying the _next_threshold state in the BOT.
void ParGCAllocBufferWithBOT::fill_region_with_block(MemRegion mr,
bool contig) {
CollectedHeap::fill_with_object(mr);
if (contig) {
_bt.alloc_block(mr.start(), mr.end());
} else {
_bt.BlockOffsetArray::alloc_block(mr.start(), mr.end());
}
}
void CardTableRS::verify_space(Space* s, HeapWord* gen_boundary) {
// We don't need to do young-gen spaces.
if (s->end() <= gen_boundary) return;
MemRegion used = s->used_region();
jbyte* cur_entry = byte_for(used.start());
jbyte* limit = byte_after(used.last());
while (cur_entry < limit) {
if (*cur_entry == CardTableModRefBS::clean_card) {
jbyte* first_dirty = cur_entry+1;
while (first_dirty < limit &&
*first_dirty == CardTableModRefBS::clean_card)
first_dirty++;
// If the first object is a regular object, and it has a
// young-to-old field, that would mark the previous card.
HeapWord* boundary = addr_for(cur_entry);
HeapWord* end = addr_for(first_dirty);
HeapWord* boundary_block = s->block_start(boundary);
HeapWord* begin = boundary; // Until proven otherwise.
HeapWord* start_block = boundary_block; // Until proven otherwise.
if (boundary_block < boundary) {
if (s->block_is_obj(boundary_block)) {
oop boundary_obj = oop(boundary_block);
if (!boundary_obj->is_objArray() &&
!boundary_obj->is_typeArray()) {
guarantee(cur_entry > byte_for(used.start()),
"else boundary would be boundary_block");
if (*byte_for(boundary_block) != CardTableModRefBS::clean_card) {
begin = boundary_block + s->block_size(boundary_block);
start_block = begin;
}
}
}
}
// Now traverse objects until end.
HeapWord* cur = start_block;
VerifyCleanCardClosure verify_blk(gen_boundary, begin, end);
while (cur < end) {
if (s->block_is_obj(cur)) {
oop(cur)->oop_iterate(&verify_blk);
}
cur += s->block_size(cur);
}
cur_entry = first_dirty;
} else {
guarantee(*cur_entry != cur_youngergen_and_prev_nonclean_card,
"Illegal CT value");
// If we're in the parallel case, the cur and prev values are
// different, and we can't have left a prev in the table.
guarantee(cur_youngergen_card_val() == youngergen_card
|| !is_prev_youngergen_card_val(*cur_entry),
"Illegal CT value");
cur_entry++;
}
}
}
void Space::object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl) {
assert(!mr.is_empty(), "Should be non-empty");
// We use MemRegion(bottom(), end()) rather than used_region() below
// because the two are not necessarily equal for some kinds of
// spaces, in particular, certain kinds of free list spaces.
// We could use the more complicated but more precise:
// MemRegion(used_region().start(), round_to(used_region().end(), CardSize))
// but the slight imprecision seems acceptable in the assertion check.
assert(MemRegion(bottom(), end()).contains(mr),
"Should be within used space");
HeapWord* prev = cl->previous(); // max address from last time
if (prev >= mr.end()) { // nothing to do
return;
}
// This assert will not work when we go from cms space to perm
// space, and use same closure. Easy fix deferred for later. XXX YSR
// assert(prev == NULL || contains(prev), "Should be within space");
bool last_was_obj_array = false;
HeapWord *blk_start_addr, *region_start_addr;
if (prev > mr.start()) {
region_start_addr = prev;
blk_start_addr = prev;
// The previous invocation may have pushed "prev" beyond the
// last allocated block yet there may be still be blocks
// in this region due to a particular coalescing policy.
// Relax the assertion so that the case where the unallocated
// block is maintained and "prev" is beyond the unallocated
// block does not cause the assertion to fire.
assert((BlockOffsetArrayUseUnallocatedBlock &&
(!is_in(prev))) ||
(blk_start_addr == block_start(region_start_addr)), "invariant");
} else {
region_start_addr = mr.start();
blk_start_addr = block_start(region_start_addr);
}
HeapWord* region_end_addr = mr.end();
MemRegion derived_mr(region_start_addr, region_end_addr);
while (blk_start_addr < region_end_addr) {
const size_t size = block_size(blk_start_addr);
if (block_is_obj(blk_start_addr)) {
last_was_obj_array = cl->do_object_bm(oop(blk_start_addr), derived_mr);
} else {
last_was_obj_array = false;
}
blk_start_addr += size;
}
if (!last_was_obj_array) {
assert((bottom() <= blk_start_addr) && (blk_start_addr <= end()),
"Should be within (closed) used space");
assert(blk_start_addr > prev, "Invariant");
cl->set_previous(blk_start_addr); // min address for next time
}
}
void MutableSpace::initialize(MemRegion mr,
bool clear_space,
bool mangle_space,
bool setup_pages) {
assert(Universe::on_page_boundary(mr.start()) && Universe::on_page_boundary(mr.end()),
"invalid space boundaries");
if (setup_pages && (UseNUMA || AlwaysPreTouch || UseColoredSpaces)) {
// The space may move left and right or expand/shrink.
// We'd like to enforce the desired page placement.
MemRegion head, tail;
if (last_setup_region().is_empty()) {
// If it's the first initialization don't limit the amount of work.
head = mr;
tail = MemRegion(mr.end(), mr.end());
} else {
// Is there an intersection with the address space?
MemRegion intersection = last_setup_region().intersection(mr);
if (intersection.is_empty()) {
intersection = MemRegion(mr.end(), mr.end());
}
// All the sizes below are in words.
size_t head_size = 0, tail_size = 0;
if (mr.start() <= intersection.start()) {
head_size = pointer_delta(intersection.start(), mr.start());
}
if(intersection.end() <= mr.end()) {
tail_size = pointer_delta(mr.end(), intersection.end());
}
// Limit the amount of page manipulation if necessary.
if (UseColoredSpaces) {
if (ColoredSpaceResizeRate > 0 && !AlwaysPreTouch) {
const size_t change_size = head_size + tail_size;
const float setup_rate_words = ColoredSpaceResizeRate >> LogBytesPerWord;
head_size = MIN2((size_t)(setup_rate_words * head_size / change_size),
head_size);
tail_size = MIN2((size_t)(setup_rate_words * tail_size / change_size),
tail_size);
}
} else {
if (NUMASpaceResizeRate > 0 && !AlwaysPreTouch) {
const size_t change_size = head_size + tail_size;
const float setup_rate_words = NUMASpaceResizeRate >> LogBytesPerWord;
head_size = MIN2((size_t)(setup_rate_words * head_size / change_size),
head_size);
tail_size = MIN2((size_t)(setup_rate_words * tail_size / change_size),
tail_size);
}
}
head = MemRegion(intersection.start() - head_size, intersection.start());
tail = MemRegion(intersection.end(), intersection.end() + tail_size);
}
// Simply mangle the MemRegion mr.
void SpaceMangler::mangle_region(MemRegion mr) {
assert(ZapUnusedHeapArea, "Mangling should not be in use");
#ifdef ASSERT
if(TraceZapUnusedHeapArea) {
gclog_or_tty->print("Mangling [" PTR_FORMAT " to " PTR_FORMAT ")", p2i(mr.start()), p2i(mr.end()));
}
Copy::fill_to_words(mr.start(), mr.word_size(), badHeapWord);
if(TraceZapUnusedHeapArea) {
gclog_or_tty->print_cr(" done");
}
#endif
}
void ClearNoncleanCardWrapper::do_MemRegion(MemRegion mr) {
assert(mr.word_size() > 0, "Error");
assert(_ct->is_aligned(mr.start()), "mr.start() should be card aligned");
// mr.end() may not necessarily be card aligned.
jbyte* cur_entry = _ct->byte_for(mr.last());
const jbyte* limit = _ct->byte_for(mr.start());
HeapWord* end_of_non_clean = mr.end();
HeapWord* start_of_non_clean = end_of_non_clean;
while (cur_entry >= limit) {
HeapWord* cur_hw = _ct->addr_for(cur_entry);
if ((*cur_entry != CardTableRS::clean_card_val()) && clear_card(cur_entry)) {
// Continue the dirty range by opening the
// dirty window one card to the left.
start_of_non_clean = cur_hw;
} else {
// We hit a "clean" card; process any non-empty
// "dirty" range accumulated so far.
if (start_of_non_clean < end_of_non_clean) {
const MemRegion mrd(start_of_non_clean, end_of_non_clean);
_dirty_card_closure->do_MemRegion(mrd);
}
// fast forward through potential continuous whole-word range of clean cards beginning at a word-boundary
if (is_word_aligned(cur_entry)) {
jbyte* cur_row = cur_entry - BytesPerWord;
while (cur_row >= limit && *((intptr_t*)cur_row) == CardTableRS::clean_card_row()) {
cur_row -= BytesPerWord;
}
cur_entry = cur_row + BytesPerWord;
cur_hw = _ct->addr_for(cur_entry);
}
// Reset the dirty window, while continuing to look
// for the next dirty card that will start a
// new dirty window.
end_of_non_clean = cur_hw;
start_of_non_clean = cur_hw;
}
// Note that "cur_entry" leads "start_of_non_clean" in
// its leftward excursion after this point
// in the loop and, when we hit the left end of "mr",
// will point off of the left end of the card-table
// for "mr".
cur_entry--;
}
// If the first card of "mr" was dirty, we will have
// been left with a dirty window, co-initial with "mr",
// which we now process.
if (start_of_non_clean < end_of_non_clean) {
const MemRegion mrd(start_of_non_clean, end_of_non_clean);
_dirty_card_closure->do_MemRegion(mrd);
}
}
G1BlockOffsetArray::G1BlockOffsetArray(G1BlockOffsetSharedArray* array,
MemRegion mr, bool init_to_zero) :
G1BlockOffsetTable(mr.start(), mr.end()),
_unallocated_block(_bottom),
_array(array), _csp(NULL),
_init_to_zero(init_to_zero) {
assert(_bottom <= _end, "arguments out of order");
if (!_init_to_zero) {
// initialize cards to point back to mr.start()
set_remainder_to_point_to_start(mr.start() + N_words, mr.end());
_array->set_offset_array(0, 0); // set first card to 0
}
}
BlockOffsetArray::BlockOffsetArray(BlockOffsetSharedArray* array,
MemRegion mr, bool init_to_zero_) :
BlockOffsetTable(mr.start(), mr.end()),
_array(array)
{
assert(_bottom <= _end, "arguments out of order");
set_init_to_zero(init_to_zero_);
if (!init_to_zero_) {
// initialize cards to point back to mr.start()
set_remainder_to_point_to_start(mr.start() + N_words, mr.end());
_array->set_offset_array(0, 0); // set first card to 0
}
}
G1BlockOffsetArray::G1BlockOffsetArray(G1BlockOffsetSharedArray* array,
MemRegion mr) :
G1BlockOffsetTable(mr.start(), mr.end()),
_unallocated_block(_bottom),
_array(array), _gsp(NULL) {
assert(_bottom <= _end, "arguments out of order");
}
MemRegion MemRegion::_union(const MemRegion mr2) const {
// If one region is empty, return the other
if (is_empty()) return mr2;
if (mr2.is_empty()) return MemRegion(start(), end());
// Otherwise, regions must overlap or be adjacent
assert(((start() <= mr2.start()) && (end() >= mr2.start())) ||
((mr2.start() <= start()) && (mr2.end() >= start())),
"non-adjacent or overlapping regions");
MemRegion res;
HeapWord* res_start = MIN2(start(), mr2.start());
HeapWord* res_end = MAX2(end(), mr2.end());
res.set_start(res_start);
res.set_end(res_end);
return res;
}
// This is the shared initialization code. It sets up the basic pointers,
// and allows enough extra space for a filler object. We call a virtual
// method, "lab_is_valid()" to handle the different asserts the old/young
// labs require.
void PSPromotionLAB::initialize(MemRegion lab) {
assert(lab_is_valid(lab), "Sanity");
HeapWord* bottom = lab.start();
HeapWord* end = lab.end();
set_bottom(bottom);
set_end(end);
set_top(bottom);
// We can be initialized to a zero size!
if (free() > 0) {
if (ZapUnusedHeapArea) {
debug_only(Memory::set_words(top(), free()/HeapWordSize, badHeapWord));
}
// NOTE! We need to allow space for a filler object.
assert(lab.word_size() >= filler_header_size, "lab is too small");
end = end - filler_header_size;
set_end(end);
_state = needs_flush;
} else {
_state = zero_size;
}
assert(this->top() <= this->end(), "pointers out of order");
}
void
G1SATBCardTableLoggingModRefBS::invalidate(MemRegion mr, bool whole_heap) {
jbyte* byte = byte_for(mr.start());
jbyte* last_byte = byte_for(mr.last());
Thread* thr = Thread::current();
if (whole_heap) {
while (byte <= last_byte) {
*byte = dirty_card;
byte++;
}
} else {
// Enqueue if necessary.
if (thr->is_Java_thread()) {
JavaThread* jt = (JavaThread*)thr;
while (byte <= last_byte) {
if (*byte != dirty_card) {
*byte = dirty_card;
jt->dirty_card_queue().enqueue(byte);
}
byte++;
}
} else {
MutexLockerEx x(Shared_DirtyCardQ_lock,
Mutex::_no_safepoint_check_flag);
while (byte <= last_byte) {
if (*byte != dirty_card) {
*byte = dirty_card;
_dcqs.shared_dirty_card_queue()->enqueue(byte);
}
byte++;
}
}
}
}
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 CardTableRS::verify_aligned_region_empty(MemRegion mr) {
if (!mr.is_empty()) {
jbyte* cur_entry = byte_for(mr.start());
jbyte* limit = byte_after(mr.last());
// The region mr may not start on a card boundary so
// the first card may reflect a write to the space
// just prior to mr.
if (!is_aligned(mr.start())) {
cur_entry++;
}
for (;cur_entry < limit; cur_entry++) {
guarantee(*cur_entry == CardTableModRefBS::clean_card,
"Unexpected dirty card found");
}
}
}
// This is the shared initialization code. It sets up the basic pointers,
// and allows enough extra space for a filler object. We call a virtual
// method, "lab_is_valid()" to handle the different asserts the old/young
// labs require.
void PSPromotionLAB::initialize(MemRegion lab) {
assert(lab_is_valid(lab), "Sanity");
HeapWord* bottom = lab.start();
HeapWord* end = lab.end();
set_bottom(bottom);
set_end(end);
set_top(bottom);
// Initialize after VM starts up because header_size depends on compressed
// oops.
filler_header_size = align_object_size(typeArrayOopDesc::header_size(T_INT));
// We can be initialized to a zero size!
if (free() > 0) {
if (ZapUnusedHeapArea) {
debug_only(Copy::fill_to_words(top(), free()/HeapWordSize, badHeapWord));
}
// NOTE! We need to allow space for a filler object.
assert(lab.word_size() >= filler_header_size, "lab is too small");
end = end - filler_header_size;
set_end(end);
_state = needs_flush;
} else {
_state = zero_size;
}
assert(this->top() <= this->end(), "pointers out of order");
}
inline void ModUnionClosurePar::do_MemRegion(MemRegion mr) {
// Align the end of mr so it's at a card boundary.
// This is superfluous except at the end of the space;
// we should do better than this XXX
MemRegion mr2(mr.start(), (HeapWord*)round_to((intptr_t)mr.end(),
CardTableModRefBS::card_size /* bytes */));
_t->par_mark_range(mr2);
}
void Space::initialize(MemRegion mr, bool clear_space) {
HeapWord* bottom = mr.start();
HeapWord* end = mr.end();
assert(Universe::on_page_boundary(bottom) && Universe::on_page_boundary(end),
"invalid space boundaries");
set_bottom(bottom);
set_end(end);
if (clear_space) clear();
}
void HeapRegion::oops_in_mr_iterate(MemRegion mr, OopClosure* cl) {
HeapWord* p = mr.start();
HeapWord* e = mr.end();
oop obj;
while (p < e) {
obj = oop(p);
p += obj->oop_iterate(cl);
}
assert(p == e, "bad memregion: doesn't end on obj boundary");
}
inline void CMSBitMap::par_markRange(MemRegion mr) {
assert_locked();
mr = mr.intersection(MemRegion(_bmStartWord, _bmWordSize));
assert(!mr.is_empty(), "unexpected empty region");
// convert address range into offset range
size_t start_ofs = heapWordToOffset(mr.start());
size_t end_ofs = heapWordToOffset(mr.end());
// Range size is usually just 1 bit.
_bm.par_set_range(start_ofs, end_ofs, BitMap::small_range);
}
void ImmutableSpace::initialize(MemRegion mr) {
HeapWord* bottom = mr.start();
HeapWord* end = mr.end();
assert(Universe::on_page_boundary(bottom) && Universe::on_page_boundary(end),
"invalid space boundaries");
_bottom = bottom;
_end = end;
}
MemRegion MemRegion::intersection(const MemRegion mr2) const {
MemRegion res;
HeapWord* res_start = MAX2(start(), mr2.start());
HeapWord* res_end = MIN2(end(), mr2.end());
if (res_start < res_end) {
res.set_start(res_start);
res.set_end(res_end);
}
return res;
}
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 G1SATBCardTableModRefBS::g1_mark_as_young(const MemRegion& mr) {
jbyte *const first = byte_for(mr.start());
jbyte *const last = byte_after(mr.last());
// Below we may use an explicit loop instead of memset() because on
// certain platforms memset() can give concurrent readers phantom zeros.
if (UseMemSetInBOT) {
memset(first, g1_young_gen, last - first);
} else {
for (jbyte* i = first; i < last; i++) {
*i = g1_young_gen;
}
}
}
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 ContiguousSpace::object_iterate_mem(MemRegion mr, UpwardsObjectClosure* cl) {
assert(!mr.is_empty(), "Should be non-empty");
assert(used_region().contains(mr), "Should be within used space");
HeapWord* prev = cl->previous(); // max address from last time
if (prev >= mr.end()) { // nothing to do
return;
}
// See comment above (in more general method above) in case you
// happen to use this method.
assert(prev == NULL || is_in_reserved(prev), "Should be within space");
bool last_was_obj_array = false;
HeapWord *obj_start_addr, *region_start_addr;
if (prev > mr.start()) {
region_start_addr = prev;
obj_start_addr = prev;
assert(obj_start_addr == block_start(region_start_addr), "invariant");
} else {
region_start_addr = mr.start();
obj_start_addr = block_start(region_start_addr);
}
HeapWord* region_end_addr = mr.end();
MemRegion derived_mr(region_start_addr, region_end_addr);
while (obj_start_addr < region_end_addr) {
oop obj = oop(obj_start_addr);
const size_t size = obj->size();
last_was_obj_array = cl->do_object_bm(obj, derived_mr);
obj_start_addr += size;
}
if (!last_was_obj_array) {
assert((bottom() <= obj_start_addr) && (obj_start_addr <= end()),
"Should be within (closed) used space");
assert(obj_start_addr > prev, "Invariant");
cl->set_previous(obj_start_addr); // min address for next time
}
}