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comparison src/share/vm/gc_implementation/g1/g1AllocRegion.cpp @ 2433:abdfc822206f

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7023069: G1: Introduce symmetric locking in the slow allocation path 7023151: G1: refactor the code that operates on _cur_alloc_region to be re-used for allocs by the GC threads 7018286: G1: humongous allocation attempts should take the GC locker into account Summary: First, this change replaces the asymmetric locking scheme in the G1 slow alloc path by a summetric one. Second, it factors out the code that operates on _cur_alloc_region so that it can be re-used for allocations by the GC threads in the future. Reviewed-by: stefank, brutisso, johnc
author tonyp
date Wed, 30 Mar 2011 10:26:59 -0400
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children f44782f04dd4
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2432:455328d90876 2433:abdfc822206f
1 /*
2 * Copyright (c) 2011, 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
25 #include "precompiled.hpp"
26 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
27 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
28
29 G1CollectedHeap* G1AllocRegion::_g1h = NULL;
30 HeapRegion* G1AllocRegion::_dummy_region = NULL;
31
32 void G1AllocRegion::setup(G1CollectedHeap* g1h, HeapRegion* dummy_region) {
33 assert(_dummy_region == NULL, "should be set once");
34 assert(dummy_region != NULL, "pre-condition");
35 assert(dummy_region->free() == 0, "pre-condition");
36
37 // Make sure that any allocation attempt on this region will fail
38 // and will not trigger any asserts.
39 assert(allocate(dummy_region, 1, false) == NULL, "should fail");
40 assert(par_allocate(dummy_region, 1, false) == NULL, "should fail");
41 assert(allocate(dummy_region, 1, true) == NULL, "should fail");
42 assert(par_allocate(dummy_region, 1, true) == NULL, "should fail");
43
44 _g1h = g1h;
45 _dummy_region = dummy_region;
46 }
47
48 void G1AllocRegion::fill_up_remaining_space(HeapRegion* alloc_region,
49 bool bot_updates) {
50 assert(alloc_region != NULL && alloc_region != _dummy_region,
51 "pre-condition");
52
53 // Other threads might still be trying to allocate using a CAS out
54 // of the region we are trying to retire, as they can do so without
55 // holding the lock. So, we first have to make sure that noone else
56 // can allocate out of it by doing a maximal allocation. Even if our
57 // CAS attempt fails a few times, we'll succeed sooner or later
58 // given that failed CAS attempts mean that the region is getting
59 // closed to being full.
60 size_t free_word_size = alloc_region->free() / HeapWordSize;
61
62 // This is the minimum free chunk we can turn into a dummy
63 // object. If the free space falls below this, then noone can
64 // allocate in this region anyway (all allocation requests will be
65 // of a size larger than this) so we won't have to perform the dummy
66 // allocation.
67 size_t min_word_size_to_fill = CollectedHeap::min_fill_size();
68
69 while (free_word_size >= min_word_size_to_fill) {
70 HeapWord* dummy = par_allocate(alloc_region, free_word_size, bot_updates);
71 if (dummy != NULL) {
72 // If the allocation was successful we should fill in the space.
73 CollectedHeap::fill_with_object(dummy, free_word_size);
74 alloc_region->set_pre_dummy_top(dummy);
75 break;
76 }
77
78 free_word_size = alloc_region->free() / HeapWordSize;
79 // It's also possible that someone else beats us to the
80 // allocation and they fill up the region. In that case, we can
81 // just get out of the loop.
82 }
83 assert(alloc_region->free() / HeapWordSize < min_word_size_to_fill,
84 "post-condition");
85 }
86
87 void G1AllocRegion::retire(bool fill_up) {
88 assert(_alloc_region != NULL, ar_ext_msg(this, "not initialized properly"));
89
90 trace("retiring");
91 HeapRegion* alloc_region = _alloc_region;
92 if (alloc_region != _dummy_region) {
93 // We never have to check whether the active region is empty or not,
94 // and potentially free it if it is, given that it's guaranteed that
95 // it will never be empty.
96 assert(!alloc_region->is_empty(),
97 ar_ext_msg(this, "the alloc region should never be empty"));
98
99 if (fill_up) {
100 fill_up_remaining_space(alloc_region, _bot_updates);
101 }
102
103 assert(alloc_region->used() >= _used_bytes_before,
104 ar_ext_msg(this, "invariant"));
105 size_t allocated_bytes = alloc_region->used() - _used_bytes_before;
106 retire_region(alloc_region, allocated_bytes);
107 _used_bytes_before = 0;
108 _alloc_region = _dummy_region;
109 }
110 trace("retired");
111 }
112
113 HeapWord* G1AllocRegion::new_alloc_region_and_allocate(size_t word_size,
114 bool force) {
115 assert(_alloc_region == _dummy_region, ar_ext_msg(this, "pre-condition"));
116 assert(_used_bytes_before == 0, ar_ext_msg(this, "pre-condition"));
117
118 trace("attempting region allocation");
119 HeapRegion* new_alloc_region = allocate_new_region(word_size, force);
120 if (new_alloc_region != NULL) {
121 new_alloc_region->reset_pre_dummy_top();
122 // Need to do this before the allocation
123 _used_bytes_before = new_alloc_region->used();
124 HeapWord* result = allocate(new_alloc_region, word_size, _bot_updates);
125 assert(result != NULL, ar_ext_msg(this, "the allocation should succeeded"));
126
127 OrderAccess::storestore();
128 // Note that we first perform the allocation and then we store the
129 // region in _alloc_region. This is the reason why an active region
130 // can never be empty.
131 _alloc_region = new_alloc_region;
132 trace("region allocation successful");
133 return result;
134 } else {
135 trace("region allocation failed");
136 return NULL;
137 }
138 ShouldNotReachHere();
139 }
140
141 void G1AllocRegion::fill_in_ext_msg(ar_ext_msg* msg, const char* message) {
142 msg->append("[%s] %s b: %s r: "PTR_FORMAT" u: "SIZE_FORMAT,
143 _name, message, BOOL_TO_STR(_bot_updates),
144 _alloc_region, _used_bytes_before);
145 }
146
147 void G1AllocRegion::init() {
148 trace("initializing");
149 assert(_alloc_region == NULL && _used_bytes_before == 0,
150 ar_ext_msg(this, "pre-condition"));
151 assert(_dummy_region != NULL, "should have been set");
152 _alloc_region = _dummy_region;
153 trace("initialized");
154 }
155
156 HeapRegion* G1AllocRegion::release() {
157 trace("releasing");
158 HeapRegion* alloc_region = _alloc_region;
159 retire(false /* fill_up */);
160 assert(_alloc_region == _dummy_region, "post-condition of retire()");
161 _alloc_region = NULL;
162 trace("released");
163 return (alloc_region == _dummy_region) ? NULL : alloc_region;
164 }
165
166 #if G1_ALLOC_REGION_TRACING
167 void G1AllocRegion::trace(const char* str, size_t word_size, HeapWord* result) {
168 // All the calls to trace that set either just the size or the size
169 // and the result are considered part of level 2 tracing and are
170 // skipped during level 1 tracing.
171 if ((word_size == 0 && result == NULL) || (G1_ALLOC_REGION_TRACING > 1)) {
172 const size_t buffer_length = 128;
173 char hr_buffer[buffer_length];
174 char rest_buffer[buffer_length];
175
176 HeapRegion* alloc_region = _alloc_region;
177 if (alloc_region == NULL) {
178 jio_snprintf(hr_buffer, buffer_length, "NULL");
179 } else if (alloc_region == _dummy_region) {
180 jio_snprintf(hr_buffer, buffer_length, "DUMMY");
181 } else {
182 jio_snprintf(hr_buffer, buffer_length,
183 HR_FORMAT, HR_FORMAT_PARAMS(alloc_region));
184 }
185
186 if (G1_ALLOC_REGION_TRACING > 1) {
187 if (result != NULL) {
188 jio_snprintf(rest_buffer, buffer_length, SIZE_FORMAT" "PTR_FORMAT,
189 word_size, result);
190 } else if (word_size != 0) {
191 jio_snprintf(rest_buffer, buffer_length, SIZE_FORMAT, word_size);
192 } else {
193 jio_snprintf(rest_buffer, buffer_length, "");
194 }
195 } else {
196 jio_snprintf(rest_buffer, buffer_length, "");
197 }
198
199 tty->print_cr("[%s] %s : %s %s", _name, hr_buffer, str, rest_buffer);
200 }
201 }
202 #endif // G1_ALLOC_REGION_TRACING
203
204 G1AllocRegion::G1AllocRegion(const char* name,
205 bool bot_updates)
206 : _name(name), _bot_updates(bot_updates),
207 _alloc_region(NULL), _used_bytes_before(0) { }
208