/* * Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. *
*/
void CardTable::initialize_card_size() {
assert(UseG1GC || UseParallelGC || UseSerialGC, "Initialize card size should only be called by card based collectors.");
os::trace_page_sizes("Card Table", num_bytes, num_bytes,
_page_size, heap_rs.base(), heap_rs.size()); if (!heap_rs.is_reserved()) {
vm_exit_during_initialization("Could not reserve enough space for the " "card marking array");
}
// The assembler store_check code will do an unsigned shift of the oop, // then add it to _byte_map_base, i.e. // // _byte_map = _byte_map_base + (uintptr_t(low_bound) >> card_shift)
_byte_map = (CardValue*) heap_rs.base();
_byte_map_base = _byte_map - (uintptr_t(low_bound) >> _card_shift);
assert(byte_for(low_bound) == &_byte_map[0], "Checking start of map");
assert(byte_for(high_bound-1) <= &_byte_map[last_valid_index()], "Checking end of map");
CardValue* guard_card = &_byte_map[num_cards];
assert(is_aligned(guard_card, _page_size), "must be on its own OS page");
_guard_region = MemRegion((HeapWord*)guard_card, _page_size);
MemRegion CardTable::committed_unique_to_self(int self, MemRegion mr) const {
assert(mr.intersection(_guard_region).is_empty(), "precondition");
MemRegion result = mr; for (int r = 0; r < _cur_covered_regions; r += 1) { if (r != self) {
result = result.minus(_committed[r]);
}
} return result;
}
void CardTable::resize_covered_region(MemRegion new_region) { // We don't change the start of a region, only the end.
assert(_whole_heap.contains(new_region), "attempt to cover area not in reserved area"); // collided is true if the expansion would push into another committed region
debug_only(bool collided = false;) intconst ind = find_covering_region_by_base(new_region.start());
MemRegion const old_region = _covered[ind];
assert(old_region.start() == new_region.start(), "just checking"); if (new_region.word_size() != old_region.word_size()) { // Commit new or uncommit old pages, if necessary.
MemRegion cur_committed = _committed[ind]; // Extend the end of this _committed region // to cover the end of any lower _committed regions. // This forms overlapping regions, but never interior regions.
HeapWord* const max_prev_end = largest_prev_committed_end(ind); if (max_prev_end > cur_committed.end()) {
cur_committed.set_end(max_prev_end);
} // Align the end up to a page size (starts are already aligned).
HeapWord* new_end = (HeapWord*) byte_after(new_region.last());
HeapWord* new_end_aligned = align_up(new_end, _page_size);
assert(new_end_aligned >= new_end, "align up, but less"); // Check the other regions (excludes "ind") to ensure that // the new_end_aligned does not intrude onto the committed // space of another region. int ri = 0; for (ri = ind + 1; ri < _cur_covered_regions; ri++) { if (new_end_aligned > _committed[ri].start()) {
assert(new_end_aligned <= _committed[ri].end(), "An earlier committed region can't cover a later committed region"); // Any region containing the new end // should start at or beyond the region found (ind) // for the new end (committed regions are not expected to // be proper subsets of other committed regions).
assert(_committed[ri].start() >= _committed[ind].start(), "New end of committed region is inconsistent");
new_end_aligned = _committed[ri].start(); // new_end_aligned can be equal to the start of its // committed region (i.e., of "ind") if a second // region following "ind" also start at the same location // as "ind".
assert(new_end_aligned >= _committed[ind].start(), "New end of committed region is before start");
debug_only(collided = true;) // Should only collide with 1 region break;
}
} #ifdef ASSERT for (++ri; ri < _cur_covered_regions; ri++) {
assert(!_committed[ri].contains(new_end_aligned), "New end of committed region is in a second committed region");
} #endif // The guard page is always committed and should not be committed over. // "guarded" is used for assertion checking below and recalls the fact // that the would-be end of the new committed region would have // penetrated the guard page.
HeapWord* new_end_for_commit = new_end_aligned;
if (new_end_for_commit > cur_committed.end()) { // Must commit new pages.
MemRegion const new_committed =
MemRegion(cur_committed.end(), new_end_for_commit);
assert(!new_committed.is_empty(), "Region should not be empty here");
os::commit_memory_or_exit((char*)new_committed.start(),
new_committed.byte_size(), _page_size,
!ExecMem, "card table expansion"); // Use new_end_aligned (as opposed to new_end_for_commit) because // the cur_committed region may include the guard region.
} elseif (new_end_aligned < cur_committed.end()) { // Must uncommit pages.
MemRegion const uncommit_region =
committed_unique_to_self(ind, MemRegion(new_end_aligned,
cur_committed.end())); if (!uncommit_region.is_empty()) { if (!os::uncommit_memory((char*)uncommit_region.start(),
uncommit_region.byte_size())) {
assert(false, "Card table contraction failed"); // The call failed so don't change the end of the // committed region. This is better than taking the // VM down.
new_end_aligned = _committed[ind].end();
}
}
} // In any case, we can reset the end of the current committed entry.
_committed[ind].set_end(new_end_aligned);
#ifdef ASSERT // Check that the last card in the new region is committed according // to the tables. bool covered = false; for (int cr = 0; cr < _cur_covered_regions; cr++) { if (_committed[cr].contains(new_end - 1)) {
covered = true; break;
}
}
assert(covered, "Card for end of new region not committed"); #endif
// The default of 0 is not necessarily clean cards.
CardValue* entry; if (old_region.last() < _whole_heap.start()) {
entry = byte_for(_whole_heap.start());
} else {
entry = byte_after(old_region.last());
}
assert(index_for(new_region.last()) <= last_valid_index(), "The guard card will be overwritten"); // This line commented out cleans the newly expanded region and // not the aligned up expanded region. // CardValue* const end = byte_after(new_region.last());
CardValue* const end = (CardValue*) new_end_for_commit;
assert((end >= byte_after(new_region.last())) || collided || guarded, "Expect to be beyond new region unless impacting another region"); // do nothing if we resized downward. #ifdef ASSERT for (int ri = 0; ri < _cur_covered_regions; ri++) { if (ri != ind) { // The end of the new committed region should not // be in any existing region unless it matches // the start of the next region.
assert(!_committed[ri].contains(end) ||
(_committed[ri].start() == (HeapWord*) end), "Overlapping committed regions");
}
} #endif if (entry < end) {
memset(entry, clean_card, pointer_delta(end, entry, sizeof(CardValue)));
}
} // In any case, the covered size changes.
_covered[ind].set_word_size(new_region.word_size());
// Touch the last card of the covered region to show that it // is committed (or SEGV).
debug_only((void) (*byte_for(_covered[ind].last()));)
}
// Note that these versions are precise! The scanning code has to handle the // fact that the write barrier may be either precise or imprecise. void CardTable::dirty_MemRegion(MemRegion mr) {
assert(align_down(mr.start(), HeapWordSize) == mr.start(), "Unaligned start");
assert(align_up (mr.end(), HeapWordSize) == mr.end(), "Unaligned end" );
CardValue* cur = byte_for(mr.start());
CardValue* last = byte_after(mr.last()); while (cur < last) {
*cur = dirty_card;
cur++;
}
}
void CardTable::clear_MemRegion(MemRegion mr) { // Be conservative: only clean cards entirely contained within the // region.
CardValue* cur; if (mr.start() == _whole_heap.start()) {
cur = byte_for(mr.start());
} else {
assert(mr.start() > _whole_heap.start(), "mr is not covered.");
cur = byte_after(mr.start() - 1);
}
CardValue* last = byte_after(mr.last());
memset(cur, clean_card, pointer_delta(last, cur, sizeof(CardValue)));
}
void CardTable::clear(MemRegion mr) { for (int i = 0; i < _cur_covered_regions; i++) {
MemRegion mri = mr.intersection(_covered[i]); if (!mri.is_empty()) clear_MemRegion(mri);
}
}
uintx CardTable::ct_max_alignment_constraint() { // Calculate maximum alignment using GCCardSizeInBytes as card_size hasn't been set yet return GCCardSizeInBytes * os::vm_page_size();
}
void CardTable::invalidate(MemRegion mr) {
assert(align_down(mr.start(), HeapWordSize) == mr.start(), "Unaligned start");
assert(align_up (mr.end(), HeapWordSize) == mr.end(), "Unaligned end" ); for (int i = 0; i < _cur_covered_regions; i++) {
MemRegion mri = mr.intersection(_covered[i]); if (!mri.is_empty()) dirty_MemRegion(mri);
}
}
Die Informationen auf dieser Webseite wurden
nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit,
noch Qualität der bereit gestellten Informationen zugesichert.
Bemerkung:
Die farbliche Syntaxdarstellung ist noch experimentell.
