1 /*
2 * Copyright (c) 2011, 2015, 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/g1CollectedHeap.inline.hpp"
28 #include "runtime/orderAccess.inline.hpp"
29
30 G1CollectedHeap* G1AllocRegion::_g1h = NULL;
31 HeapRegion* G1AllocRegion::_dummy_region = NULL;
32
33 void G1AllocRegion::setup(G1CollectedHeap* g1h, HeapRegion* dummy_region) {
34 assert(_dummy_region == NULL, "should be set once");
35 assert(dummy_region != NULL, "pre-condition");
36 assert(dummy_region->free() == 0, "pre-condition");
37
38 // Make sure that any allocation attempt on this region will fail
39 // and will not trigger any asserts.
40 assert(allocate(dummy_region, 1, false) == NULL, "should fail");
41 assert(par_allocate(dummy_region, 1, false) == NULL, "should fail");
42 assert(allocate(dummy_region, 1, true) == NULL, "should fail");
43 assert(par_allocate(dummy_region, 1, true) == NULL, "should fail");
44
45 _g1h = g1h;
46 _dummy_region = dummy_region;
47 }
48
49 size_t G1AllocRegion::fill_up_remaining_space(HeapRegion* alloc_region,
50 bool bot_updates) {
51 assert(alloc_region != NULL && alloc_region != _dummy_region,
52 "pre-condition");
53 size_t result = 0;
54
55 // Other threads might still be trying to allocate using a CAS out
56 // of the region we are trying to retire, as they can do so without
57 // holding the lock. So, we first have to make sure that noone else
58 // can allocate out of it by doing a maximal allocation. Even if our
59 // CAS attempt fails a few times, we'll succeed sooner or later
60 // given that failed CAS attempts mean that the region is getting
61 // closed to being full.
62 size_t free_word_size = alloc_region->free() / HeapWordSize;
63
64 // This is the minimum free chunk we can turn into a dummy
65 // object. If the free space falls below this, then noone can
66 // allocate in this region anyway (all allocation requests will be
67 // of a size larger than this) so we won't have to perform the dummy
68 // allocation.
69 size_t min_word_size_to_fill = CollectedHeap::min_fill_size();
70
71 while (free_word_size >= min_word_size_to_fill) {
72 HeapWord* dummy = par_allocate(alloc_region, free_word_size, bot_updates);
73 if (dummy != NULL) {
74 // If the allocation was successful we should fill in the space.
75 CollectedHeap::fill_with_object(dummy, free_word_size);
76 alloc_region->set_pre_dummy_top(dummy);
77 result += free_word_size * HeapWordSize;
78 break;
79 }
80
81 free_word_size = alloc_region->free() / HeapWordSize;
82 // It's also possible that someone else beats us to the
83 // allocation and they fill up the region. In that case, we can
84 // just get out of the loop.
85 }
86 result += alloc_region->free();
87
88 assert(alloc_region->free() / HeapWordSize < min_word_size_to_fill,
89 "post-condition");
90 return result;
91 }
92
93 size_t G1AllocRegion::retire(bool fill_up) {
94 assert(_alloc_region != NULL, G1_ALLOC_REGION_MSG("not initialized properly"));
95
96 size_t result = 0;
97
98 trace("retiring");
99 HeapRegion* alloc_region = _alloc_region;
100 if (alloc_region != _dummy_region) {
101 // We never have to check whether the active region is empty or not,
102 // and potentially free it if it is, given that it's guaranteed that
103 // it will never be empty.
104 assert(!alloc_region->is_empty(),
105 G1_ALLOC_REGION_MSG("the alloc region should never be empty"));
106
107 if (fill_up) {
108 result = fill_up_remaining_space(alloc_region, _bot_updates);
109 }
110
111 assert(alloc_region->used() >= _used_bytes_before,
112 G1_ALLOC_REGION_MSG("invariant"));
113 size_t allocated_bytes = alloc_region->used() - _used_bytes_before;
114 retire_region(alloc_region, allocated_bytes);
115 _used_bytes_before = 0;
116 _alloc_region = _dummy_region;
117 }
118 trace("retired");
119
120 return result;
121 }
122
123 HeapWord* G1AllocRegion::new_alloc_region_and_allocate(size_t word_size,
124 bool force) {
125 assert(_alloc_region == _dummy_region, G1_ALLOC_REGION_MSG("pre-condition"));
126 assert(_used_bytes_before == 0, G1_ALLOC_REGION_MSG("pre-condition"));
127
128 trace("attempting region allocation");
129 HeapRegion* new_alloc_region = allocate_new_region(word_size, force);
130 if (new_alloc_region != NULL) {
131 new_alloc_region->reset_pre_dummy_top();
132 // Need to do this before the allocation
133 _used_bytes_before = new_alloc_region->used();
134 HeapWord* result = allocate(new_alloc_region, word_size, _bot_updates);
135 assert(result != NULL, G1_ALLOC_REGION_MSG("the allocation should succeeded"));
136
137 OrderAccess::storestore();
138 // Note that we first perform the allocation and then we store the
139 // region in _alloc_region. This is the reason why an active region
140 // can never be empty.
141 update_alloc_region(new_alloc_region);
142 trace("region allocation successful");
143 return result;
144 } else {
145 trace("region allocation failed");
146 return NULL;
147 }
148 ShouldNotReachHere();
149 }
150
151 void G1AllocRegion::init() {
152 trace("initializing");
153 assert(_alloc_region == NULL && _used_bytes_before == 0,
154 G1_ALLOC_REGION_MSG("pre-condition"));
155 assert(_dummy_region != NULL, G1_ALLOC_REGION_MSG("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 != NULL && !alloc_region->is_empty(),
166 G1_ALLOC_REGION_MSG("pre-condition"));
167 assert(_alloc_region == _dummy_region &&
168 _used_bytes_before == 0 && _count == 0,
169 G1_ALLOC_REGION_MSG("pre-condition"));
170
171 _used_bytes_before = alloc_region->used();
172 _alloc_region = alloc_region;
173 _count += 1;
174 trace("set");
175 }
176
177 void G1AllocRegion::update_alloc_region(HeapRegion* alloc_region) {
178 trace("update");
179 // We explicitly check that the region is not empty to make sure we
180 // maintain the "the alloc region cannot be empty" invariant.
181 assert(alloc_region != NULL && !alloc_region->is_empty(),
182 G1_ALLOC_REGION_MSG("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 == _dummy_region,
195 G1_ALLOC_REGION_MSG("post-condition of retire()"));
196 _alloc_region = NULL;
197 trace("released");
198 return (alloc_region == _dummy_region) ? NULL : alloc_region;
199 }
200
201 #if G1_ALLOC_REGION_TRACING
202 void G1AllocRegion::trace(const char* str, size_t min_word_size, size_t desired_word_size, size_t actual_word_size, HeapWord* result) {
203 // All the calls to trace that set either just the size or the size
204 // and the result are considered part of level 2 tracing and are
205 // skipped during level 1 tracing.
206 if ((actual_word_size == 0 && result == NULL) || (G1_ALLOC_REGION_TRACING > 1)) {
207 const size_t buffer_length = 128;
208 char hr_buffer[buffer_length];
209 char rest_buffer[buffer_length];
210
211 HeapRegion* alloc_region = _alloc_region;
212 if (alloc_region == NULL) {
213 jio_snprintf(hr_buffer, buffer_length, "NULL");
214 } else if (alloc_region == _dummy_region) {
215 jio_snprintf(hr_buffer, buffer_length, "DUMMY");
216 } else {
217 jio_snprintf(hr_buffer, buffer_length,
218 HR_FORMAT, HR_FORMAT_PARAMS(alloc_region));
219 }
220
221 if (G1_ALLOC_REGION_TRACING > 1) {
222 if (result != NULL) {
223 jio_snprintf(rest_buffer, buffer_length, "min " SIZE_FORMAT " desired " SIZE_FORMAT " actual " SIZE_FORMAT " " PTR_FORMAT,
224 min_word_size, desired_word_size, actual_word_size, result);
225 } else if (min_word_size != 0) {
226 jio_snprintf(rest_buffer, buffer_length, "min " SIZE_FORMAT " desired " SIZE_FORMAT, min_word_size, desired_word_size);
227 } else {
228 jio_snprintf(rest_buffer, buffer_length, "");
229 }
230 } else {
231 jio_snprintf(rest_buffer, buffer_length, "");
232 }
233
234 tty->print_cr("[%s] %u %s : %s %s",
235 _name, _count, hr_buffer, str, rest_buffer);
236 }
237 }
238 #endif // G1_ALLOC_REGION_TRACING
239
240 G1AllocRegion::G1AllocRegion(const char* name,
241 bool bot_updates)
242 : _name(name), _bot_updates(bot_updates),
243 _alloc_region(NULL), _count(0), _used_bytes_before(0),
244 _allocation_context(AllocationContext::system()) { }
245
246
247 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
248 bool force) {
249 return _g1h->new_mutator_alloc_region(word_size, force);
250 }
251
252 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
253 size_t allocated_bytes) {
254 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
255 }
256
257 HeapRegion* G1GCAllocRegion::allocate_new_region(size_t word_size,
258 bool force) {
259 assert(!force, "not supported for GC alloc regions");
260 return _g1h->new_gc_alloc_region(word_size, count(), _purpose);
261 }
262
263 void G1GCAllocRegion::retire_region(HeapRegion* alloc_region,
264 size_t allocated_bytes) {
265 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, _purpose);
266 }
267
268 size_t G1GCAllocRegion::retire(bool fill_up) {
269 HeapRegion* retired = get();
270 size_t end_waste = G1AllocRegion::retire(fill_up);
271 // Do not count retirement of the dummy allocation region.
272 if (retired != NULL) {
273 _stats->add_region_end_waste(end_waste / HeapWordSize);
274 }
275 return end_waste;
276 }
277
278 HeapRegion* OldGCAllocRegion::release() {
279 HeapRegion* cur = get();
280 if (cur != NULL) {
281 // Determine how far we are from the next card boundary. If it is smaller than
282 // the minimum object size we can allocate into, expand into the next card.
283 HeapWord* top = cur->top();
284 HeapWord* aligned_top = (HeapWord*)align_ptr_up(top, G1BlockOffsetSharedArray::N_bytes);
285
286 size_t to_allocate_words = pointer_delta(aligned_top, top, HeapWordSize);
287
288 if (to_allocate_words != 0) {
289 // We are not at a card boundary. Fill up, possibly into the next, taking the
290 // end of the region and the minimum object size into account.
291 to_allocate_words = MIN2(pointer_delta(cur->end(), cur->top(), HeapWordSize),
292 MAX2(to_allocate_words, G1CollectedHeap::min_fill_size()));
293
294 // Skip allocation if there is not enough space to allocate even the smallest
295 // possible object. In this case this region will not be retained, so the
296 // original problem cannot occur.
297 if (to_allocate_words >= G1CollectedHeap::min_fill_size()) {
298 HeapWord* dummy = attempt_allocation(to_allocate_words, true /* bot_updates */);
299 CollectedHeap::fill_with_object(dummy, to_allocate_words);
300 }
301 }
302 }
303 return G1AllocRegion::release();
304 }