--- a/src/hotspot/share/gc/cms/cmsCardTable.cpp Fri Nov 08 14:54:17 2019 +0000
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,470 +0,0 @@
-/*
- * Copyright (c) 2007, 2018, 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.
- *
- */
-
-#include "precompiled.hpp"
-#include "gc/cms/cmsCardTable.hpp"
-#include "gc/cms/cmsHeap.hpp"
-#include "gc/shared/cardTableBarrierSet.hpp"
-#include "gc/shared/cardTableRS.hpp"
-#include "gc/shared/collectedHeap.hpp"
-#include "gc/shared/space.inline.hpp"
-#include "memory/allocation.inline.hpp"
-#include "memory/virtualspace.hpp"
-#include "oops/oop.inline.hpp"
-#include "runtime/java.hpp"
-#include "runtime/mutexLocker.hpp"
-#include "runtime/orderAccess.hpp"
-#include "runtime/vmThread.hpp"
-
-CMSCardTable::CMSCardTable(MemRegion whole_heap) :
- CardTableRS(whole_heap, CMSPrecleaningEnabled /* scanned_concurrently */) {
-}
-
-// Returns the number of chunks necessary to cover "mr".
-size_t CMSCardTable::chunks_to_cover(MemRegion mr) {
- return (size_t)(addr_to_chunk_index(mr.last()) -
- addr_to_chunk_index(mr.start()) + 1);
-}
-
-// Returns the index of the chunk in a stride which
-// covers the given address.
-uintptr_t CMSCardTable::addr_to_chunk_index(const void* addr) {
- uintptr_t card = (uintptr_t) byte_for(addr);
- return card / ParGCCardsPerStrideChunk;
-}
-
-void CMSCardTable::
-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,
- "n_threads: %u > ParallelGCThreads: %u", n_threads, ParallelGCThreads);
-
- // Make sure the LNC array is valid for the space.
- CardValue** 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->try_claim_task(/* 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
-CMSCardTable::
-process_stride(Space* sp,
- MemRegion used,
- jint stride, int n_strides,
- OopsInGenClosure* cl,
- CardTableRS* ct,
- CardValue** 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.
- CardValue* start_card = byte_for(used.start());
- CardValue* 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;
- CardValue* chunk_card_start;
-
- if ((uintptr_t)stride >= start_chunk_stride_num) {
- chunk_card_start = (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 = (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().
- CardValue* 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");
-
- // This function is used by the parallel card table iteration.
- const bool parallel = true;
-
- DirtyCardToOopClosure* dcto_cl = sp->new_dcto_cl(cl, precision(),
- cl->gen_boundary(),
- parallel);
- ClearNoncleanCardWrapper clear_cl(dcto_cl, ct, parallel);
-
-
- // 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 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
-CMSCardTable::
-process_chunk_boundaries(Space* sp,
- DirtyCardToOopClosure* dcto_cl,
- MemRegion chunk_mr,
- MemRegion used,
- CardValue** 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 start_chunk_index = addr_to_chunk_index(chunk_mr.start());
- assert(start_chunk_index >= lowest_non_clean_base_chunk_index, "Bounds error.");
- uintptr_t cur_chunk_index = start_chunk_index - lowest_non_clean_base_chunk_index;
-
- // 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 neighbor
- // does not scan an object straddling the mutual boundary
- // too far to the right, and attempt to scan a portion of
- // that object twice.
- CardValue* first_dirty_card = NULL;
- CardValue* last_card_of_first_obj =
- byte_for(first_block + sp->block_size(first_block) - 1);
- CardValue* first_card_of_cur_chunk = byte_for(chunk_mr.start());
- CardValue* last_card_of_cur_chunk = byte_for(chunk_mr.last());
- CardValue* last_card_to_check = MIN2(last_card_of_cur_chunk, 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 (CardValue* cur = first_card_of_cur_chunk;
- cur <= last_card_to_check; cur++) {
- CardValue 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) {
- assert(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;
- }
- } else {
- // In this case we can help our neighbor by just asking them
- // to stop at our first card (even though it may not be dirty).
- assert(lowest_non_clean[cur_chunk_index] == NULL, "Write once : value should be stable hereafter");
- CardValue* first_card_of_cur_chunk = byte_for(chunk_mr.start());
- lowest_non_clean[cur_chunk_index] = first_card_of_cur_chunk;
- }
-
- // 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 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()) // 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();
- } else {
- 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.
- CardValue* const last_obj_card = byte_for(last_block);
- const CardValue 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 of our chunk.
- 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.
- CardValue* limit_card = NULL;
- const size_t last_block_size = sp->block_size(last_block);
- CardValue* const last_card_of_last_obj =
- byte_for(last_block + last_block_size - 1);
- CardValue* 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, 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 (CardValue* cur = first_card_of_next_chunk;
- cur <= last_card_of_last_obj; cur++) {
- const CardValue val = *cur;
- if (card_will_be_scanned(val)) {
- limit_card = cur; break;
- } else {
- assert(!card_may_have_been_dirty(val), "Error: card can't be skipped");
- }
- }
- if (limit_card != NULL) {
- max_to_do = addr_for(limit_card);
- assert(limit_card != NULL && max_to_do != NULL, "Error");
- } 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");
- }
- 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. However, we need to bound this checking to the largest
- // entry in the LNC array: this is because the heap may expand
- // after the LNC array has been created but before we reach this point,
- // and the last block in our chunk may have been expanded to include
- // the expansion delta (and possibly subsequently allocated from, so
- // it wouldn't be sufficient to check whether that last block was
- // or was not an object at this point).
- uintptr_t last_chunk_index_to_check = addr_to_chunk_index(last_block + last_block_size - 1)
- - lowest_non_clean_base_chunk_index;
- const uintptr_t last_chunk_index = addr_to_chunk_index(used.last())
- - lowest_non_clean_base_chunk_index;
- if (last_chunk_index_to_check > last_chunk_index) {
- assert(last_block + last_block_size > used.end(),
- "Inconsistency detected: last_block [" PTR_FORMAT "," PTR_FORMAT "]"
- " does not exceed used.end() = " PTR_FORMAT ","
- " yet last_chunk_index_to_check " INTPTR_FORMAT
- " exceeds last_chunk_index " INTPTR_FORMAT,
- p2i(last_block), p2i(last_block + last_block_size),
- p2i(used.end()),
- last_chunk_index_to_check, last_chunk_index);
- assert(sp->used_region().end() > used.end(),
- "Expansion did not happen: "
- "[" PTR_FORMAT "," PTR_FORMAT ") -> [" PTR_FORMAT "," PTR_FORMAT ")",
- p2i(sp->used_region().start()), p2i(sp->used_region().end()),
- p2i(used.start()), p2i(used.end()));
- 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++) {
- CardValue* 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) {
- 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 1 !");
- }
- assert(max_to_do != NULL, "OOPS 2!");
- } else {
- max_to_do = used.end();
- }
- 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
-}
-
-void
-CMSCardTable::
-get_LNC_array_for_space(Space* sp,
- CardValue**& 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_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.)
-
- // 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 = CMSHeap::heap()->total_collections();
- // Updated _last_LNC_resizing_collection[i] must not be visible before
- // _lowest_non_clean and friends are visible. Therefore use acquire/release
- // to guarantee this on non TSO architecures.
- if (OrderAccess::load_acquire(&_last_LNC_resizing_collection[i]) != cur_collection) {
- MutexLocker x(ParGCRareEvent_lock);
- // This load_acquire is here for clarity only. The MutexLocker already fences.
- if (OrderAccess::load_acquire(&_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, mtGC);
- _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;
- }
- }
- // Make sure this gets visible only after _lowest_non_clean* was initialized
- OrderAccess::release_store(&_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];
-}
-
-#ifdef ASSERT
-void CMSCardTable::verify_used_region_at_save_marks(Space* sp) const {
- MemRegion ur = sp->used_region();
- MemRegion urasm = sp->used_region_at_save_marks();
-
- if (!ur.contains(urasm)) {
- log_warning(gc)("CMS+ParNew: Did you forget to call save_marks()? "
- "[" PTR_FORMAT ", " PTR_FORMAT ") is not contained in "
- "[" PTR_FORMAT ", " PTR_FORMAT ")",
- p2i(urasm.start()), p2i(urasm.end()), p2i(ur.start()), p2i(ur.end()));
- MemRegion ur2 = sp->used_region();
- MemRegion urasm2 = sp->used_region_at_save_marks();
- if (!ur.equals(ur2)) {
- log_warning(gc)("CMS+ParNew: Flickering used_region()!!");
- }
- if (!urasm.equals(urasm2)) {
- log_warning(gc)("CMS+ParNew: Flickering used_region_at_save_marks()!!");
- }
- ShouldNotReachHere();
- }
-}
-#endif // ASSERT