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.hpp"
29 #include "logging/log.hpp"
30 #include "runtime/atomic.hpp"
31 #include "runtime/orderAccess.hpp"
32 #include "utilities/debug.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
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
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
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 = _seqnum; seqnum != ZGlobalSeqNum; seqnum = _seqnum) {
58 if ((seqnum != seqnum_initializing) &&
59 (Atomic::cmpxchg(seqnum_initializing, &_seqnum, seqnum) == seqnum)) {
60 // Reset marking information
61 _live_bytes = 0;
62 _live_objects = 0;
63
64 // Clear segment claimed/live bits
65 segment_live_bits().clear();
66 segment_claim_bits().clear();
67
68 // Make sure the newly reset marking information is
69 // globally visible before updating the page seqnum.
70 OrderAccess::storestore();
71
72 // Update seqnum
73 assert(_seqnum == seqnum_initializing, "Invalid");
74 _seqnum = ZGlobalSeqNum;
75 break;
76 }
77
78 // Mark reset contention
79 if (!contention) {
80 // Count contention once
81 ZStatInc(ZCounterMarkSeqNumResetContention);
82 contention = true;
83
84 log_trace(gc)("Mark seqnum reset contention, thread: " PTR_FORMAT " (%s), map: " PTR_FORMAT ", bit: " SIZE_FORMAT,
85 ZThread::id(), ZThread::name(), p2i(this), index);
86 }
87 }
88 }
89
90 void ZLiveMap::reset_segment(BitMap::idx_t segment) {
91 bool contention = false;
92
93 if (!claim_segment(segment)) {
94 // Already claimed, wait for live bit to be set
95 while (!is_segment_live(segment)) {
96 // Busy wait. The loadload barrier is needed to make
97 // sure we re-read the live bit every time we loop.
98 OrderAccess::loadload();
99
100 // Mark reset contention
101 if (!contention) {
102 // Count contention once
103 ZStatInc(ZCounterMarkSegmentResetContention);
104 contention = true;
105
106 log_trace(gc)("Mark segment reset contention, thread: " PTR_FORMAT " (%s), map: " PTR_FORMAT ", segment: " SIZE_FORMAT,
107 ZThread::id(), ZThread::name(), p2i(this), segment);
108 }
109 }
110
111 // Segment is live
112 return;
113 }
114
115 // Segment claimed, clear it
116 const BitMap::idx_t start_index = segment_start(segment);
117 const BitMap::idx_t end_index = segment_end(segment);
118 if (segment_size() / BitsPerWord >= 32) {
119 _bitmap.clear_large_range(start_index, end_index);
120 } else {
121 _bitmap.clear_range(start_index, end_index);
122 }
123
124 // Set live bit
125 const bool success = set_segment_live_atomic(segment);
126 assert(success, "Should never fail");
127 }
128
129 void ZLiveMap::resize(uint32_t size) {
130 const size_t new_bitmap_size = bitmap_size(size, nsegments);
131 if (_bitmap.size() != new_bitmap_size) {
132 _bitmap.reinitialize(new_bitmap_size, false /* clear */);
133 _segment_shift = exact_log2(segment_size());
134 }
135 }