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 G1_ALLOC_REGION_ASSERT(_alloc_region != NULL, "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 G1_ALLOC_REGION_ASSERT(!alloc_region->is_empty(),
105 "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 G1_ALLOC_REGION_ASSERT(alloc_region->used() >= _used_bytes_before, "invariant");
112 size_t allocated_bytes = alloc_region->used() - _used_bytes_before;
113 retire_region(alloc_region, allocated_bytes);
114 _used_bytes_before = 0;
115 _alloc_region = _dummy_region;
116 }
117 trace("retired");
118
119 return result;
120 }
121
122 HeapWord* G1AllocRegion::new_alloc_region_and_allocate(size_t word_size,
123 bool force) {
124 G1_ALLOC_REGION_ASSERT(_alloc_region == _dummy_region, "pre-condition");
125 G1_ALLOC_REGION_ASSERT(_used_bytes_before == 0, "pre-condition");
126
127 trace("attempting region allocation");
128 HeapRegion* new_alloc_region = allocate_new_region(word_size, force);
129 if (new_alloc_region != NULL) {
130 new_alloc_region->reset_pre_dummy_top();
131 // Need to do this before the allocation
132 _used_bytes_before = new_alloc_region->used();
133 HeapWord* result = allocate(new_alloc_region, word_size, _bot_updates);
134 G1_ALLOC_REGION_ASSERT(result != NULL, "the allocation should succeeded");
135
136 OrderAccess::storestore();
137 // Note that we first perform the allocation and then we store the
138 // region in _alloc_region. This is the reason why an active region
139 // can never be empty.
140 update_alloc_region(new_alloc_region);
141 trace("region allocation successful");
142 return result;
143 } else {
144 trace("region allocation failed");
145 return NULL;
146 }
147 ShouldNotReachHere();
148 }
149
150 void G1AllocRegion::init() {
151 trace("initializing");
152 G1_ALLOC_REGION_ASSERT(_alloc_region == NULL && _used_bytes_before == 0, "pre-condition");
153 G1_ALLOC_REGION_ASSERT(_dummy_region != NULL, "should have been set");
154 _alloc_region = _dummy_region;
155 _count = 0;
156 trace("initialized");
157 }
158
159 void G1AllocRegion::set(HeapRegion* alloc_region) {
160 trace("setting");
161 // We explicitly check that the region is not empty to make sure we
162 // maintain the "the alloc region cannot be empty" invariant.
163 G1_ALLOC_REGION_ASSERT(alloc_region != NULL && !alloc_region->is_empty(), "pre-condition");
164 G1_ALLOC_REGION_ASSERT(_alloc_region == _dummy_region &&
165 _used_bytes_before == 0 && _count == 0,
166 "pre-condition");
167
168 _used_bytes_before = alloc_region->used();
169 _alloc_region = alloc_region;
170 _count += 1;
171 trace("set");
172 }
173
174 void G1AllocRegion::update_alloc_region(HeapRegion* alloc_region) {
175 trace("update");
176 // We explicitly check that the region is not empty to make sure we
177 // maintain the "the alloc region cannot be empty" invariant.
178 G1_ALLOC_REGION_ASSERT(alloc_region != NULL && !alloc_region->is_empty(), "pre-condition");
179
180 _alloc_region = alloc_region;
181 _alloc_region->set_allocation_context(allocation_context());
182 _count += 1;
183 trace("updated");
184 }
185
186 HeapRegion* G1AllocRegion::release() {
187 trace("releasing");
188 HeapRegion* alloc_region = _alloc_region;
189 retire(false /* fill_up */);
190 G1_ALLOC_REGION_ASSERT(_alloc_region == _dummy_region, "post-condition of retire()");
191 _alloc_region = NULL;
192 trace("released");
193 return (alloc_region == _dummy_region) ? NULL : alloc_region;
194 }
195
196 #if G1_ALLOC_REGION_TRACING
197 void G1AllocRegion::trace(const char* str, size_t min_word_size, size_t desired_word_size, size_t actual_word_size, HeapWord* result) {
198 // All the calls to trace that set either just the size or the size
199 // and the result are considered part of level 2 tracing and are
200 // skipped during level 1 tracing.
201 if ((actual_word_size == 0 && result == NULL) || (G1_ALLOC_REGION_TRACING > 1)) {
202 const size_t buffer_length = 128;
203 char hr_buffer[buffer_length];
204 char rest_buffer[buffer_length];
205
206 HeapRegion* alloc_region = _alloc_region;
207 if (alloc_region == NULL) {
208 jio_snprintf(hr_buffer, buffer_length, "NULL");
209 } else if (alloc_region == _dummy_region) {
210 jio_snprintf(hr_buffer, buffer_length, "DUMMY");
211 } else {
212 jio_snprintf(hr_buffer, buffer_length,
213 HR_FORMAT, HR_FORMAT_PARAMS(alloc_region));
214 }
215
216 if (G1_ALLOC_REGION_TRACING > 1) {
217 if (result != NULL) {
218 jio_snprintf(rest_buffer, buffer_length, "min " SIZE_FORMAT " desired " SIZE_FORMAT " actual " SIZE_FORMAT " " PTR_FORMAT,
219 min_word_size, desired_word_size, actual_word_size, result);
220 } else if (min_word_size != 0) {
221 jio_snprintf(rest_buffer, buffer_length, "min " SIZE_FORMAT " desired " SIZE_FORMAT, min_word_size, desired_word_size);
222 } else {
223 jio_snprintf(rest_buffer, buffer_length, "");
224 }
225 } else {
226 jio_snprintf(rest_buffer, buffer_length, "");
227 }
228
229 tty->print_cr("[%s] %u %s : %s %s",
230 _name, _count, hr_buffer, str, rest_buffer);
231 }
232 }
233 #endif // G1_ALLOC_REGION_TRACING
234
235 G1AllocRegion::G1AllocRegion(const char* name,
236 bool bot_updates)
237 : _name(name), _bot_updates(bot_updates),
238 _alloc_region(NULL), _count(0), _used_bytes_before(0),
239 _allocation_context(AllocationContext::system()) { }
240
241
242 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
243 bool force) {
244 return _g1h->new_mutator_alloc_region(word_size, force);
245 }
246
247 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
248 size_t allocated_bytes) {
249 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
250 }
251
252 HeapRegion* G1GCAllocRegion::allocate_new_region(size_t word_size,
253 bool force) {
254 assert(!force, "not supported for GC alloc regions");
255 return _g1h->new_gc_alloc_region(word_size, count(), _purpose);
256 }
257
258 void G1GCAllocRegion::retire_region(HeapRegion* alloc_region,
259 size_t allocated_bytes) {
260 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, _purpose);
261 }
262
263 size_t G1GCAllocRegion::retire(bool fill_up) {
264 HeapRegion* retired = get();
265 size_t end_waste = G1AllocRegion::retire(fill_up);
266 // Do not count retirement of the dummy allocation region.
267 if (retired != NULL) {
268 _stats->add_region_end_waste(end_waste / HeapWordSize);
269 }
270 return end_waste;
271 }
272
273 HeapRegion* OldGCAllocRegion::release() {
274 HeapRegion* cur = get();
275 if (cur != NULL) {
276 // Determine how far we are from the next card boundary. If it is smaller than
277 // the minimum object size we can allocate into, expand into the next card.
278 HeapWord* top = cur->top();
279 HeapWord* aligned_top = (HeapWord*)align_ptr_up(top, G1BlockOffsetSharedArray::N_bytes);
280
281 size_t to_allocate_words = pointer_delta(aligned_top, top, HeapWordSize);
282
283 if (to_allocate_words != 0) {
284 // We are not at a card boundary. Fill up, possibly into the next, taking the
285 // end of the region and the minimum object size into account.
286 to_allocate_words = MIN2(pointer_delta(cur->end(), cur->top(), HeapWordSize),
287 MAX2(to_allocate_words, G1CollectedHeap::min_fill_size()));
288
289 // Skip allocation if there is not enough space to allocate even the smallest
290 // possible object. In this case this region will not be retained, so the
291 // original problem cannot occur.
292 if (to_allocate_words >= G1CollectedHeap::min_fill_size()) {
293 HeapWord* dummy = attempt_allocation(to_allocate_words, true /* bot_updates */);
294 CollectedHeap::fill_with_object(dummy, to_allocate_words);
295 }
296 }
297 }
298 return G1AllocRegion::release();
299 }