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, ar_ext_msg(this, "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 ar_ext_msg(this, "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 ar_ext_msg(this, "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, ar_ext_msg(this, "pre-condition"));
126 assert(_used_bytes_before == 0, ar_ext_msg(this, "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, ar_ext_msg(this, "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::fill_in_ext_msg(ar_ext_msg* msg, const char* message) {
152 msg->append("[%s] %s c: %u b: %s r: " PTR_FORMAT " u: " SIZE_FORMAT,
153 _name, message, _count, BOOL_TO_STR(_bot_updates),
154 p2i(_alloc_region), _used_bytes_before);
155 }
156
157 void G1AllocRegion::init() {
158 trace("initializing");
159 assert(_alloc_region == NULL && _used_bytes_before == 0,
160 ar_ext_msg(this, "pre-condition"));
161 assert(_dummy_region != NULL, ar_ext_msg(this, "should have been set"));
162 _alloc_region = _dummy_region;
163 _count = 0;
164 trace("initialized");
165 }
166
167 void G1AllocRegion::set(HeapRegion* alloc_region) {
168 trace("setting");
169 // We explicitly check that the region is not empty to make sure we
170 // maintain the "the alloc region cannot be empty" invariant.
171 assert(alloc_region != NULL && !alloc_region->is_empty(),
172 ar_ext_msg(this, "pre-condition"));
173 assert(_alloc_region == _dummy_region &&
174 _used_bytes_before == 0 && _count == 0,
175 ar_ext_msg(this, "pre-condition"));
176
177 _used_bytes_before = alloc_region->used();
178 _alloc_region = alloc_region;
179 _count += 1;
180 trace("set");
181 }
182
183 void G1AllocRegion::update_alloc_region(HeapRegion* alloc_region) {
184 trace("update");
185 // We explicitly check that the region is not empty to make sure we
186 // maintain the "the alloc region cannot be empty" invariant.
187 assert(alloc_region != NULL && !alloc_region->is_empty(),
188 ar_ext_msg(this, "pre-condition"));
189
190 _alloc_region = alloc_region;
191 _alloc_region->set_allocation_context(allocation_context());
192 _count += 1;
193 trace("updated");
194 }
195
196 HeapRegion* G1AllocRegion::release() {
197 trace("releasing");
198 HeapRegion* alloc_region = _alloc_region;
199 retire(false /* fill_up */);
200 assert(_alloc_region == _dummy_region,
201 ar_ext_msg(this, "post-condition of retire()"));
202 _alloc_region = NULL;
203 trace("released");
204 return (alloc_region == _dummy_region) ? NULL : alloc_region;
205 }
206
207 #if G1_ALLOC_REGION_TRACING
208 void G1AllocRegion::trace(const char* str, size_t word_size, HeapWord* result) {
209 // All the calls to trace that set either just the size or the size
210 // and the result are considered part of level 2 tracing and are
211 // skipped during level 1 tracing.
212 if ((word_size == 0 && result == NULL) || (G1_ALLOC_REGION_TRACING > 1)) {
213 const size_t buffer_length = 128;
214 char hr_buffer[buffer_length];
215 char rest_buffer[buffer_length];
216
217 HeapRegion* alloc_region = _alloc_region;
218 if (alloc_region == NULL) {
219 jio_snprintf(hr_buffer, buffer_length, "NULL");
220 } else if (alloc_region == _dummy_region) {
221 jio_snprintf(hr_buffer, buffer_length, "DUMMY");
222 } else {
223 jio_snprintf(hr_buffer, buffer_length,
224 HR_FORMAT, HR_FORMAT_PARAMS(alloc_region));
225 }
226
227 if (G1_ALLOC_REGION_TRACING > 1) {
228 if (result != NULL) {
229 jio_snprintf(rest_buffer, buffer_length, SIZE_FORMAT " " PTR_FORMAT,
230 word_size, result);
231 } else if (word_size != 0) {
232 jio_snprintf(rest_buffer, buffer_length, SIZE_FORMAT, word_size);
233 } else {
234 jio_snprintf(rest_buffer, buffer_length, "");
235 }
236 } else {
237 jio_snprintf(rest_buffer, buffer_length, "");
238 }
239
240 tty->print_cr("[%s] %u %s : %s %s",
241 _name, _count, hr_buffer, str, rest_buffer);
242 }
243 }
244 #endif // G1_ALLOC_REGION_TRACING
245
246 G1AllocRegion::G1AllocRegion(const char* name,
247 bool bot_updates)
248 : _name(name), _bot_updates(bot_updates),
249 _alloc_region(NULL), _count(0), _used_bytes_before(0),
250 _allocation_context(AllocationContext::system()) { }
251
252
253 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
254 bool force) {
255 return _g1h->new_mutator_alloc_region(word_size, force);
256 }
257
258 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
259 size_t allocated_bytes) {
260 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
261 }
262
263 HeapRegion* G1GCAllocRegion::allocate_new_region(size_t word_size,
264 bool force) {
265 assert(!force, "not supported for GC alloc regions");
266 return _g1h->new_gc_alloc_region(word_size, count(), _purpose);
267 }
268
269 void G1GCAllocRegion::retire_region(HeapRegion* alloc_region,
270 size_t allocated_bytes) {
271 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, _purpose);
272 }
273
274 size_t G1GCAllocRegion::retire(bool fill_up) {
275 HeapRegion* retired = get();
276 size_t end_waste = G1AllocRegion::retire(fill_up);
277 // Do not count retirement of the dummy allocation region.
278 if (retired != NULL) {
279 _stats->add_region_end_waste(end_waste / HeapWordSize);
280 }
281 return end_waste;
282 }
283
284 HeapRegion* OldGCAllocRegion::release() {
285 HeapRegion* cur = get();
286 if (cur != NULL) {
287 // Determine how far we are from the next card boundary. If it is smaller than
288 // the minimum object size we can allocate into, expand into the next card.
289 HeapWord* top = cur->top();
290 HeapWord* aligned_top = (HeapWord*)align_ptr_up(top, G1BlockOffsetSharedArray::N_bytes);
291
292 size_t to_allocate_words = pointer_delta(aligned_top, top, HeapWordSize);
293
294 if (to_allocate_words != 0) {
295 // We are not at a card boundary. Fill up, possibly into the next, taking the
296 // end of the region and the minimum object size into account.
297 to_allocate_words = MIN2(pointer_delta(cur->end(), cur->top(), HeapWordSize),
298 MAX2(to_allocate_words, G1CollectedHeap::min_fill_size()));
299
300 // Skip allocation if there is not enough space to allocate even the smallest
301 // possible object. In this case this region will not be retained, so the
302 // original problem cannot occur.
303 if (to_allocate_words >= G1CollectedHeap::min_fill_size()) {
304 HeapWord* dummy = attempt_allocation(to_allocate_words, true /* bot_updates */);
305 CollectedHeap::fill_with_object(dummy, to_allocate_words);
306 }
307 }
308 }
309 return G1AllocRegion::release();
310 }