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 "logging/log.hpp"
30 #include "logging/logStream.hpp"
31 #include "memory/resourceArea.hpp"
32 #include "runtime/orderAccess.inline.hpp"
33
34 G1CollectedHeap* G1AllocRegion::_g1h = NULL;
35 HeapRegion* G1AllocRegion::_dummy_region = NULL;
36
37 void G1AllocRegion::setup(G1CollectedHeap* g1h, HeapRegion* dummy_region) {
38 assert(_dummy_region == NULL, "should be set once");
39 assert(dummy_region != NULL, "pre-condition");
40 assert(dummy_region->free() == 0, "pre-condition");
41
42 // Make sure that any allocation attempt on this region will fail
43 // and will not trigger any asserts.
44 assert(allocate(dummy_region, 1, false) == NULL, "should fail");
45 assert(par_allocate(dummy_region, 1, false) == NULL, "should fail");
46 assert(allocate(dummy_region, 1, true) == NULL, "should fail");
47 assert(par_allocate(dummy_region, 1, true) == NULL, "should fail");
48
49 _g1h = g1h;
50 _dummy_region = dummy_region;
51 }
52
53 size_t G1AllocRegion::fill_up_remaining_space(HeapRegion* alloc_region,
54 bool bot_updates) {
55 assert(alloc_region != NULL && alloc_region != _dummy_region,
56 "pre-condition");
57 size_t result = 0;
58
59 // Other threads might still be trying to allocate using a CAS out
60 // of the region we are trying to retire, as they can do so without
61 // holding the lock. So, we first have to make sure that noone else
62 // can allocate out of it by doing a maximal allocation. Even if our
63 // CAS attempt fails a few times, we'll succeed sooner or later
64 // given that failed CAS attempts mean that the region is getting
65 // closed to being full.
66 size_t free_word_size = alloc_region->free() / HeapWordSize;
67
68 // This is the minimum free chunk we can turn into a dummy
69 // object. If the free space falls below this, then noone can
70 // allocate in this region anyway (all allocation requests will be
71 // of a size larger than this) so we won't have to perform the dummy
72 // allocation.
73 size_t min_word_size_to_fill = CollectedHeap::min_fill_size();
74
75 while (free_word_size >= min_word_size_to_fill) {
76 HeapWord* dummy = par_allocate(alloc_region, free_word_size, bot_updates);
77 if (dummy != NULL) {
78 // If the allocation was successful we should fill in the space.
79 CollectedHeap::fill_with_object(dummy, free_word_size);
80 alloc_region->set_pre_dummy_top(dummy);
81 result += free_word_size * HeapWordSize;
82 break;
83 }
84
85 free_word_size = alloc_region->free() / HeapWordSize;
86 // It's also possible that someone else beats us to the
87 // allocation and they fill up the region. In that case, we can
88 // just get out of the loop.
89 }
90 result += alloc_region->free();
91
92 assert(alloc_region->free() / HeapWordSize < min_word_size_to_fill,
93 "post-condition");
94 return result;
95 }
96
97 size_t G1AllocRegion::retire(bool fill_up) {
98 assert_alloc_region(_alloc_region != NULL, "not initialized properly");
99
100 size_t result = 0;
101
102 trace("retiring");
103 HeapRegion* alloc_region = _alloc_region;
104 if (alloc_region != _dummy_region) {
105 // We never have to check whether the active region is empty or not,
106 // and potentially free it if it is, given that it's guaranteed that
107 // it will never be empty.
108 assert_alloc_region(!alloc_region->is_empty(),
109 "the alloc region should never be empty");
110
111 if (fill_up) {
112 result = fill_up_remaining_space(alloc_region, _bot_updates);
113 }
114
115 assert_alloc_region(alloc_region->used() >= _used_bytes_before, "invariant");
116 size_t allocated_bytes = alloc_region->used() - _used_bytes_before;
117 retire_region(alloc_region, allocated_bytes);
118 _used_bytes_before = 0;
119 _alloc_region = _dummy_region;
120 }
121 trace("retired");
122
123 return result;
124 }
125
126 HeapWord* G1AllocRegion::new_alloc_region_and_allocate(size_t word_size,
127 bool force) {
128 assert_alloc_region(_alloc_region == _dummy_region, "pre-condition");
129 assert_alloc_region(_used_bytes_before == 0, "pre-condition");
130
131 trace("attempting region allocation");
132 HeapRegion* new_alloc_region = allocate_new_region(word_size, force);
133 if (new_alloc_region != NULL) {
134 new_alloc_region->reset_pre_dummy_top();
135 // Need to do this before the allocation
136 _used_bytes_before = new_alloc_region->used();
137 HeapWord* result = allocate(new_alloc_region, word_size, _bot_updates);
138 assert_alloc_region(result != NULL, "the allocation should succeeded");
139
140 OrderAccess::storestore();
141 // Note that we first perform the allocation and then we store the
142 // region in _alloc_region. This is the reason why an active region
143 // can never be empty.
144 update_alloc_region(new_alloc_region);
145 trace("region allocation successful");
146 return result;
147 } else {
148 trace("region allocation failed");
149 return NULL;
150 }
151 ShouldNotReachHere();
152 }
153
154 void G1AllocRegion::init() {
155 trace("initializing");
156 assert_alloc_region(_alloc_region == NULL && _used_bytes_before == 0, "pre-condition");
157 assert_alloc_region(_dummy_region != NULL, "should have been set");
158 _alloc_region = _dummy_region;
159 _count = 0;
160 trace("initialized");
161 }
162
163 void G1AllocRegion::set(HeapRegion* alloc_region) {
164 trace("setting");
165 // We explicitly check that the region is not empty to make sure we
166 // maintain the "the alloc region cannot be empty" invariant.
167 assert_alloc_region(alloc_region != NULL && !alloc_region->is_empty(), "pre-condition");
168 assert_alloc_region(_alloc_region == _dummy_region &&
169 _used_bytes_before == 0 && _count == 0,
170 "pre-condition");
171
172 _used_bytes_before = alloc_region->used();
173 _alloc_region = alloc_region;
174 _count += 1;
175 trace("set");
176 }
177
178 void G1AllocRegion::update_alloc_region(HeapRegion* alloc_region) {
179 trace("update");
180 // We explicitly check that the region is not empty to make sure we
181 // maintain the "the alloc region cannot be empty" invariant.
182 assert_alloc_region(alloc_region != NULL && !alloc_region->is_empty(), "pre-condition");
183
184 _alloc_region = alloc_region;
185 _alloc_region->set_allocation_context(allocation_context());
186 _count += 1;
187 trace("updated");
188 }
189
190 HeapRegion* G1AllocRegion::release() {
191 trace("releasing");
192 HeapRegion* alloc_region = _alloc_region;
193 retire(false /* fill_up */);
194 assert_alloc_region(_alloc_region == _dummy_region, "post-condition of retire()");
195 _alloc_region = NULL;
196 trace("released");
197 return (alloc_region == _dummy_region) ? NULL : alloc_region;
198 }
199
200 #ifndef PRODUCT
201 void G1AllocRegion::trace(const char* str, size_t min_word_size, size_t desired_word_size, size_t actual_word_size, HeapWord* result) {
202 // All the calls to trace that set either just the size or the size
203 // and the result are considered part of detailed tracing and are
204 // skipped during other tracing.
205
206 Log(gc, alloc, region) log;
207
208 if (!log.is_debug()) {
209 return;
210 }
211
212 bool detailed_info = log.is_trace();
213
214 if ((actual_word_size == 0 && result == NULL) || detailed_info) {
215 ResourceMark rm;
216 LogStream ls_trace(log.trace());
217 LogStream ls_debug(log.debug());
218 outputStream* out = detailed_info ? &ls_trace : &ls_debug;
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 }