136 lines
4.6 KiB
C++
136 lines
4.6 KiB
C++
/*
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* Copyright (c) 2015, 2019, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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#include "precompiled.hpp"
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#include "gc/z/zHeap.inline.hpp"
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#include "gc/z/zLiveMap.inline.hpp"
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#include "gc/z/zStat.hpp"
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#include "gc/z/zThread.hpp"
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#include "logging/log.hpp"
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#include "runtime/atomic.hpp"
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#include "runtime/orderAccess.hpp"
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#include "utilities/debug.hpp"
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static const ZStatCounter ZCounterMarkSeqNumResetContention("Contention", "Mark SeqNum Reset Contention", ZStatUnitOpsPerSecond);
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static const ZStatCounter ZCounterMarkSegmentResetContention("Contention", "Mark Segment Reset Contention", ZStatUnitOpsPerSecond);
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static size_t bitmap_size(uint32_t size, size_t nsegments) {
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// We need at least one bit per segment
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return MAX2<size_t>(size, nsegments) * 2;
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}
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ZLiveMap::ZLiveMap(uint32_t size) :
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_seqnum(0),
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_live_objects(0),
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_live_bytes(0),
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_segment_live_bits(0),
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_segment_claim_bits(0),
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_bitmap(bitmap_size(size, nsegments)),
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_segment_shift(exact_log2(segment_size())) {}
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void ZLiveMap::reset(size_t index) {
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const uint32_t seqnum_initializing = (uint32_t)-1;
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bool contention = false;
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// Multiple threads can enter here, make sure only one of them
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// resets the marking information while the others busy wait.
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for (uint32_t seqnum = _seqnum; seqnum != ZGlobalSeqNum; seqnum = _seqnum) {
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if ((seqnum != seqnum_initializing) &&
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(Atomic::cmpxchg(seqnum_initializing, &_seqnum, seqnum) == seqnum)) {
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// Reset marking information
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_live_bytes = 0;
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_live_objects = 0;
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// Clear segment claimed/live bits
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segment_live_bits().clear();
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segment_claim_bits().clear();
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// Make sure the newly reset marking information is
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// globally visible before updating the page seqnum.
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OrderAccess::storestore();
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// Update seqnum
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assert(_seqnum == seqnum_initializing, "Invalid");
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_seqnum = ZGlobalSeqNum;
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break;
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}
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// Mark reset contention
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if (!contention) {
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// Count contention once
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ZStatInc(ZCounterMarkSeqNumResetContention);
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contention = true;
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log_trace(gc)("Mark seqnum reset contention, thread: " PTR_FORMAT " (%s), map: " PTR_FORMAT ", bit: " SIZE_FORMAT,
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ZThread::id(), ZThread::name(), p2i(this), index);
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}
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}
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}
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void ZLiveMap::reset_segment(BitMap::idx_t segment) {
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bool contention = false;
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if (!claim_segment(segment)) {
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// Already claimed, wait for live bit to be set
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while (!is_segment_live(segment)) {
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// Busy wait. The loadload barrier is needed to make
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// sure we re-read the live bit every time we loop.
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OrderAccess::loadload();
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// Mark reset contention
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if (!contention) {
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// Count contention once
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ZStatInc(ZCounterMarkSegmentResetContention);
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contention = true;
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log_trace(gc)("Mark segment reset contention, thread: " PTR_FORMAT " (%s), map: " PTR_FORMAT ", segment: " SIZE_FORMAT,
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ZThread::id(), ZThread::name(), p2i(this), segment);
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}
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}
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// Segment is live
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return;
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}
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// Segment claimed, clear it
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const BitMap::idx_t start_index = segment_start(segment);
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const BitMap::idx_t end_index = segment_end(segment);
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if (segment_size() / BitsPerWord >= 32) {
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_bitmap.clear_large_range(start_index, end_index);
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} else {
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_bitmap.clear_range(start_index, end_index);
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}
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// Set live bit
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const bool success = set_segment_live_atomic(segment);
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assert(success, "Should never fail");
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}
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void ZLiveMap::resize(uint32_t size) {
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const size_t new_bitmap_size = bitmap_size(size, nsegments);
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if (_bitmap.size() != new_bitmap_size) {
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_bitmap.reinitialize(new_bitmap_size, false /* clear */);
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_segment_shift = exact_log2(segment_size());
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}
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}
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