1 /*
2 * Copyright (c) 2011, 2016, 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/g1/g1AllocRegion.inline.hpp"
27 #include "gc/g1/g1EvacStats.inline.hpp"
28 #include "gc/g1/g1CollectedHeap.inline.hpp"
29 #include "memory/resourceArea.hpp"
30 #include "runtime/orderAccess.inline.hpp"
31
32 G1CollectedHeap* G1AllocRegion::_g1h = NULL;
33 HeapRegion* G1AllocRegion::_dummy_region = NULL;
34
35 void G1AllocRegion::setup(G1CollectedHeap* g1h, HeapRegion* dummy_region) {
36 assert(_dummy_region == NULL, "should be set once");
37 assert(dummy_region != NULL, "pre-condition");
38 assert(dummy_region->free() == 0, "pre-condition");
39
40 // Make sure that any allocation attempt on this region will fail
41 // and will not trigger any asserts.
42 assert(allocate(dummy_region, 1, false) == NULL, "should fail");
43 assert(par_allocate(dummy_region, 1, false) == NULL, "should fail");
44 assert(allocate(dummy_region, 1, true) == NULL, "should fail");
45 assert(par_allocate(dummy_region, 1, true) == NULL, "should fail");
46
47 _g1h = g1h;
48 _dummy_region = dummy_region;
49 }
50
51 size_t G1AllocRegion::fill_up_remaining_space(HeapRegion* alloc_region,
52 bool bot_updates) {
53 assert(alloc_region != NULL && alloc_region != _dummy_region,
54 "pre-condition");
55 size_t result = 0;
56
57 // Other threads might still be trying to allocate using a CAS out
58 // of the region we are trying to retire, as they can do so without
59 // holding the lock. So, we first have to make sure that noone else
60 // can allocate out of it by doing a maximal allocation. Even if our
61 // CAS attempt fails a few times, we'll succeed sooner or later
62 // given that failed CAS attempts mean that the region is getting
63 // closed to being full.
64 size_t free_word_size = alloc_region->free() / HeapWordSize;
65
66 // This is the minimum free chunk we can turn into a dummy
67 // object. If the free space falls below this, then noone can
68 // allocate in this region anyway (all allocation requests will be
69 // of a size larger than this) so we won't have to perform the dummy
70 // allocation.
71 size_t min_word_size_to_fill = CollectedHeap::min_fill_size();
72
73 while (free_word_size >= min_word_size_to_fill) {
74 HeapWord* dummy = par_allocate(alloc_region, free_word_size, bot_updates);
75 if (dummy != NULL) {
76 // If the allocation was successful we should fill in the space.
77 CollectedHeap::fill_with_object(dummy, free_word_size);
78 alloc_region->set_pre_dummy_top(dummy);
79 result += free_word_size * HeapWordSize;
80 break;
81 }
82
83 free_word_size = alloc_region->free() / HeapWordSize;
84 // It's also possible that someone else beats us to the
85 // allocation and they fill up the region. In that case, we can
86 // just get out of the loop.
87 }
88 result += alloc_region->free();
89
90 assert(alloc_region->free() / HeapWordSize < min_word_size_to_fill,
91 "post-condition");
92 return result;
93 }
94
95 size_t G1AllocRegion::retire(bool fill_up) {
96 assert_alloc_region(_alloc_region != NULL, "not initialized properly");
97
98 size_t result = 0;
99
100 trace("retiring");
101 HeapRegion* alloc_region = _alloc_region;
102 if (alloc_region != _dummy_region) {
103 // We never have to check whether the active region is empty or not,
104 // and potentially free it if it is, given that it's guaranteed that
105 // it will never be empty.
106 assert_alloc_region(!alloc_region->is_empty(),
107 "the alloc region should never be empty");
108
109 if (fill_up) {
110 result = fill_up_remaining_space(alloc_region, _bot_updates);
111 }
112
113 assert_alloc_region(alloc_region->used() >= _used_bytes_before, "invariant");
114 size_t allocated_bytes = alloc_region->used() - _used_bytes_before;
115 retire_region(alloc_region, allocated_bytes);
116 _used_bytes_before = 0;
117 _alloc_region = _dummy_region;
118 }
119 trace("retired");
120
121 return result;
122 }
123
124 HeapWord* G1AllocRegion::new_alloc_region_and_allocate(size_t word_size,
125 bool force) {
126 assert_alloc_region(_alloc_region == _dummy_region, "pre-condition");
127 assert_alloc_region(_used_bytes_before == 0, "pre-condition");
128
129 trace("attempting region allocation");
130 HeapRegion* new_alloc_region = allocate_new_region(word_size, force);
131 if (new_alloc_region != NULL) {
132 new_alloc_region->reset_pre_dummy_top();
133 // Need to do this before the allocation
134 _used_bytes_before = new_alloc_region->used();
135 HeapWord* result = allocate(new_alloc_region, word_size, _bot_updates);
136 assert_alloc_region(result != NULL, "the allocation should succeeded");
137
138 OrderAccess::storestore();
139 // Note that we first perform the allocation and then we store the
140 // region in _alloc_region. This is the reason why an active region
141 // can never be empty.
142 update_alloc_region(new_alloc_region);
143 trace("region allocation successful");
144 return result;
145 } else {
146 trace("region allocation failed");
147 return NULL;
148 }
149 ShouldNotReachHere();
150 }
151
152 void G1AllocRegion::init() {
153 trace("initializing");
154 assert_alloc_region(_alloc_region == NULL && _used_bytes_before == 0, "pre-condition");
155 assert_alloc_region(_dummy_region != NULL, "should have been set");
156 _alloc_region = _dummy_region;
157 _count = 0;
158 trace("initialized");
159 }
160
161 void G1AllocRegion::set(HeapRegion* alloc_region) {
162 trace("setting");
163 // We explicitly check that the region is not empty to make sure we
164 // maintain the "the alloc region cannot be empty" invariant.
165 assert_alloc_region(alloc_region != NULL && !alloc_region->is_empty(), "pre-condition");
166 assert_alloc_region(_alloc_region == _dummy_region &&
167 _used_bytes_before == 0 && _count == 0,
168 "pre-condition");
169
170 _used_bytes_before = alloc_region->used();
171 _alloc_region = alloc_region;
172 _count += 1;
173 trace("set");
174 }
175
176 void G1AllocRegion::update_alloc_region(HeapRegion* alloc_region) {
177 trace("update");
178 // We explicitly check that the region is not empty to make sure we
179 // maintain the "the alloc region cannot be empty" invariant.
180 assert_alloc_region(alloc_region != NULL && !alloc_region->is_empty(), "pre-condition");
181
182 _alloc_region = alloc_region;
183 _alloc_region->set_allocation_context(allocation_context());
184 _count += 1;
185 trace("updated");
186 }
187
188 HeapRegion* G1AllocRegion::release() {
189 trace("releasing");
190 HeapRegion* alloc_region = _alloc_region;
191 retire(false /* fill_up */);
192 assert_alloc_region(_alloc_region == _dummy_region, "post-condition of retire()");
193 _alloc_region = NULL;
194 trace("released");
195 return (alloc_region == _dummy_region) ? NULL : alloc_region;
196 }
197
198 #ifndef PRODUCT
199 void G1AllocRegion::trace(const char* str, size_t min_word_size, size_t desired_word_size, size_t actual_word_size, HeapWord* result) {
200 // All the calls to trace that set either just the size or the size
201 // and the result are considered part of detailed tracing and are
202 // skipped during other tracing.
203
204 if (!log_develop_is_enabled(Debug, gc, alloc, region)) {
205 return;
206 }
207
208 bool detailed_info = log_develop_is_enabled(Trace, gc, alloc, region);
209
210 if ((actual_word_size == 0 && result == NULL) || detailed_info) {
211 LogHandle(gc, alloc, region) log;
212 ResourceMark rm;
213 outputStream* out;
214 if (detailed_info) {
215 out = log.trace_stream();
216 } else {
217 out = log.debug_stream();
218 }
219
220 out->print("%s: %u ", _name, _count);
221
222 if (_alloc_region == NULL) {
223 out->print("NULL");
224 } else if (_alloc_region == _dummy_region) {
225 out->print("DUMMY");
226 } else {
227 out->print(HR_FORMAT, HR_FORMAT_PARAMS(_alloc_region));
228 }
229
230 out->print(" : %s", str);
231
232 if (detailed_info) {
233 if (result != NULL) {
234 out->print(" min " SIZE_FORMAT " desired " SIZE_FORMAT " actual " SIZE_FORMAT " " PTR_FORMAT,
235 min_word_size, desired_word_size, actual_word_size, p2i(result));
236 } else if (min_word_size != 0) {
237 out->print(" min " SIZE_FORMAT " desired " SIZE_FORMAT, min_word_size, desired_word_size);
238 }
239 }
240 out->cr();
241 }
242 }
243 #endif // PRODUCT
244
245 G1AllocRegion::G1AllocRegion(const char* name,
246 bool bot_updates)
247 : _name(name), _bot_updates(bot_updates),
248 _alloc_region(NULL), _count(0), _used_bytes_before(0),
249 _allocation_context(AllocationContext::system()) { }
250
251
252 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
253 bool force) {
254 return _g1h->new_mutator_alloc_region(word_size, force);
255 }
256
257 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
258 size_t allocated_bytes) {
259 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
260 }
261
262 HeapRegion* G1GCAllocRegion::allocate_new_region(size_t word_size,
263 bool force) {
264 assert(!force, "not supported for GC alloc regions");
265 return _g1h->new_gc_alloc_region(word_size, _purpose);
266 }
267
268 void G1GCAllocRegion::retire_region(HeapRegion* alloc_region,
269 size_t allocated_bytes) {
270 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, _purpose);
271 }
272
273 size_t G1GCAllocRegion::retire(bool fill_up) {
274 HeapRegion* retired = get();
275 size_t end_waste = G1AllocRegion::retire(fill_up);
276 // Do not count retirement of the dummy allocation region.
277 if (retired != NULL) {
278 _stats->add_region_end_waste(end_waste / HeapWordSize);
279 }
280 return end_waste;
281 }
282
283 HeapRegion* OldGCAllocRegion::release() {
284 HeapRegion* cur = get();
285 if (cur != NULL) {
286 // Determine how far we are from the next card boundary. If it is smaller than
287 // the minimum object size we can allocate into, expand into the next card.
288 HeapWord* top = cur->top();
289 HeapWord* aligned_top = (HeapWord*)align_ptr_up(top, BOTConstants::N_bytes);
290
291 size_t to_allocate_words = pointer_delta(aligned_top, top, HeapWordSize);
292
293 if (to_allocate_words != 0) {
294 // We are not at a card boundary. Fill up, possibly into the next, taking the
295 // end of the region and the minimum object size into account.
296 to_allocate_words = MIN2(pointer_delta(cur->end(), cur->top(), HeapWordSize),
297 MAX2(to_allocate_words, G1CollectedHeap::min_fill_size()));
298
299 // Skip allocation if there is not enough space to allocate even the smallest
300 // possible object. In this case this region will not be retained, so the
301 // original problem cannot occur.
302 if (to_allocate_words >= G1CollectedHeap::min_fill_size()) {
303 HeapWord* dummy = attempt_allocation(to_allocate_words, true /* bot_updates */);
304 CollectedHeap::fill_with_object(dummy, to_allocate_words);
305 }
306 }
307 }
308 return G1AllocRegion::release();
309 }