1 /*
2 * Copyright (c) 2015, 2019, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23
24 #include "precompiled.hpp"
25 #include "gc/z/zHeap.inline.hpp"
26 #include "gc/z/zLiveMap.inline.hpp"
27 #include "gc/z/zStat.hpp"
28 #include "gc/z/zThread.inline.hpp"
29 #include "logging/log.hpp"
30 #include "runtime/atomic.hpp"
31 #include "utilities/debug.hpp"
32 #include "utilities/powerOfTwo.hpp"
33
34 static const ZStatCounter ZCounterMarkSeqNumResetContention("Contention", "Mark SeqNum Reset Contention", ZStatUnitOpsPerSecond);
35 static const ZStatCounter ZCounterMarkSegmentResetContention("Contention", "Mark Segment Reset Contention", ZStatUnitOpsPerSecond);
36
bitmap_size(uint32_t size,size_t nsegments)37 static size_t bitmap_size(uint32_t size, size_t nsegments) {
38 // We need at least one bit per segment
39 return MAX2<size_t>(size, nsegments) * 2;
40 }
41
ZLiveMap(uint32_t size)42 ZLiveMap::ZLiveMap(uint32_t size) :
43 _seqnum(0),
44 _live_objects(0),
45 _live_bytes(0),
46 _segment_live_bits(0),
47 _segment_claim_bits(0),
48 _bitmap(bitmap_size(size, nsegments)),
49 _segment_shift(exact_log2(segment_size())) {}
50
reset(size_t index)51 void ZLiveMap::reset(size_t index) {
52 const uint32_t seqnum_initializing = (uint32_t)-1;
53 bool contention = false;
54
55 // Multiple threads can enter here, make sure only one of them
56 // resets the marking information while the others busy wait.
57 for (uint32_t seqnum = Atomic::load_acquire(&_seqnum);
58 seqnum != ZGlobalSeqNum;
59 seqnum = Atomic::load_acquire(&_seqnum)) {
60 if ((seqnum != seqnum_initializing) &&
61 (Atomic::cmpxchg(&_seqnum, seqnum, seqnum_initializing) == seqnum)) {
62 // Reset marking information
63 _live_bytes = 0;
64 _live_objects = 0;
65
66 // Clear segment claimed/live bits
67 segment_live_bits().clear();
68 segment_claim_bits().clear();
69
70 assert(_seqnum == seqnum_initializing, "Invalid");
71
72 // Make sure the newly reset marking information is ordered
73 // before the update of the page seqnum, such that when the
74 // up-to-date seqnum is load acquired, the bit maps will not
75 // contain stale information.
76 Atomic::release_store(&_seqnum, ZGlobalSeqNum);
77 break;
78 }
79
80 // Mark reset contention
81 if (!contention) {
82 // Count contention once
83 ZStatInc(ZCounterMarkSeqNumResetContention);
84 contention = true;
85
86 log_trace(gc)("Mark seqnum reset contention, thread: " PTR_FORMAT " (%s), map: " PTR_FORMAT ", bit: " SIZE_FORMAT,
87 ZThread::id(), ZThread::name(), p2i(this), index);
88 }
89 }
90 }
91
reset_segment(BitMap::idx_t segment)92 void ZLiveMap::reset_segment(BitMap::idx_t segment) {
93 bool contention = false;
94
95 if (!claim_segment(segment)) {
96 // Already claimed, wait for live bit to be set
97 while (!is_segment_live(segment)) {
98 // Mark reset contention
99 if (!contention) {
100 // Count contention once
101 ZStatInc(ZCounterMarkSegmentResetContention);
102 contention = true;
103
104 log_trace(gc)("Mark segment reset contention, thread: " PTR_FORMAT " (%s), map: " PTR_FORMAT ", segment: " SIZE_FORMAT,
105 ZThread::id(), ZThread::name(), p2i(this), segment);
106 }
107 }
108
109 // Segment is live
110 return;
111 }
112
113 // Segment claimed, clear it
114 const BitMap::idx_t start_index = segment_start(segment);
115 const BitMap::idx_t end_index = segment_end(segment);
116 if (segment_size() / BitsPerWord >= 32) {
117 _bitmap.clear_large_range(start_index, end_index);
118 } else {
119 _bitmap.clear_range(start_index, end_index);
120 }
121
122 // Set live bit
123 const bool success = set_segment_live(segment);
124 assert(success, "Should never fail");
125 }
126
resize(uint32_t size)127 void ZLiveMap::resize(uint32_t size) {
128 const size_t new_bitmap_size = bitmap_size(size, nsegments);
129 if (_bitmap.size() != new_bitmap_size) {
130 _bitmap.reinitialize(new_bitmap_size, false /* clear */);
131 _segment_shift = exact_log2(segment_size());
132 }
133 }
134