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 #include "utilities/align.hpp"
32
33 G1CollectedHeap* G1AllocRegion::_g1h = NULL;
34 HeapRegion* G1AllocRegion::_dummy_region = NULL;
35
36 void G1AllocRegion::setup(G1CollectedHeap* g1h, HeapRegion* dummy_region) {
37 assert(_dummy_region == NULL, "should be set once");
38 assert(dummy_region != NULL, "pre-condition");
39 assert(dummy_region->free() == 0, "pre-condition");
40
41 // Make sure that any allocation attempt on this region will fail
42 // and will not trigger any asserts.
43 assert(allocate(dummy_region, 1, false) == NULL, "should fail");
44 assert(par_allocate(dummy_region, 1, false) == NULL, "should fail");
45 assert(allocate(dummy_region, 1, true) == NULL, "should fail");
46 assert(par_allocate(dummy_region, 1, true) == NULL, "should fail");
47
48 _g1h = g1h;
49 _dummy_region = dummy_region;
50 }
51
52 size_t G1AllocRegion::fill_up_remaining_space(HeapRegion* alloc_region,
53 bool bot_updates) {
54 assert(alloc_region != NULL && alloc_region != _dummy_region,
55 "pre-condition");
56 size_t result = 0;
57
58 // Other threads might still be trying to allocate using a CAS out
59 // of the region we are trying to retire, as they can do so without
60 // holding the lock. So, we first have to make sure that noone else
61 // can allocate out of it by doing a maximal allocation. Even if our
62 // CAS attempt fails a few times, we'll succeed sooner or later
63 // given that failed CAS attempts mean that the region is getting
64 // closed to being full.
65 size_t free_word_size = alloc_region->free() / HeapWordSize;
66
67 // This is the minimum free chunk we can turn into a dummy
68 // object. If the free space falls below this, then noone can
69 // allocate in this region anyway (all allocation requests will be
70 // of a size larger than this) so we won't have to perform the dummy
71 // allocation.
72 size_t min_word_size_to_fill = CollectedHeap::min_fill_size();
73
74 while (free_word_size >= min_word_size_to_fill) {
75 HeapWord* dummy = par_allocate(alloc_region, free_word_size, bot_updates);
76 if (dummy != NULL) {
77 // If the allocation was successful we should fill in the space.
78 CollectedHeap::fill_with_object(dummy, free_word_size);
79 alloc_region->set_pre_dummy_top(dummy);
80 result += free_word_size * HeapWordSize;
81 break;
82 }
83
84 free_word_size = alloc_region->free() / HeapWordSize;
85 // It's also possible that someone else beats us to the
86 // allocation and they fill up the region. In that case, we can
87 // just get out of the loop.
88 }
89 result += alloc_region->free();
90
91 assert(alloc_region->free() / HeapWordSize < min_word_size_to_fill,
92 "post-condition");
93 return result;
94 }
95
96 size_t G1AllocRegion::retire(bool fill_up) {
97 assert_alloc_region(_alloc_region != NULL, "not initialized properly");
98
99 size_t result = 0;
100
101 trace("retiring");
102 HeapRegion* alloc_region = _alloc_region;
103 if (alloc_region != _dummy_region) {
104 // We never have to check whether the active region is empty or not,
105 // and potentially free it if it is, given that it's guaranteed that
106 // it will never be empty.
107 assert_alloc_region(!alloc_region->is_empty(),
108 "the alloc region should never be empty");
109
110 if (fill_up) {
111 result = fill_up_remaining_space(alloc_region, _bot_updates);
112 }
113
114 assert_alloc_region(alloc_region->used() >= _used_bytes_before, "invariant");
115 size_t allocated_bytes = alloc_region->used() - _used_bytes_before;
116 retire_region(alloc_region, allocated_bytes);
117 _used_bytes_before = 0;
118 _alloc_region = _dummy_region;
119 }
120 trace("retired");
121
122 return result;
123 }
124
125 HeapWord* G1AllocRegion::new_alloc_region_and_allocate(size_t word_size,
126 bool force) {
127 assert_alloc_region(_alloc_region == _dummy_region, "pre-condition");
128 assert_alloc_region(_used_bytes_before == 0, "pre-condition");
129
130 trace("attempting region allocation");
131 HeapRegion* new_alloc_region = allocate_new_region(word_size, force);
132 if (new_alloc_region != NULL) {
133 new_alloc_region->reset_pre_dummy_top();
134 // Need to do this before the allocation
135 _used_bytes_before = new_alloc_region->used();
136 HeapWord* result = allocate(new_alloc_region, word_size, _bot_updates);
137 assert_alloc_region(result != NULL, "the allocation should succeeded");
138
139 OrderAccess::storestore();
140 // Note that we first perform the allocation and then we store the
141 // region in _alloc_region. This is the reason why an active region
142 // can never be empty.
143 update_alloc_region(new_alloc_region);
144 trace("region allocation successful");
145 return result;
146 } else {
147 trace("region allocation failed");
148 return NULL;
149 }
150 ShouldNotReachHere();
151 }
152
153 void G1AllocRegion::init() {
154 trace("initializing");
155 assert_alloc_region(_alloc_region == NULL && _used_bytes_before == 0, "pre-condition");
156 assert_alloc_region(_dummy_region != NULL, "should have been set");
157 _alloc_region = _dummy_region;
158 _count = 0;
159 trace("initialized");
160 }
161
162 void G1AllocRegion::set(HeapRegion* alloc_region) {
163 trace("setting");
164 // We explicitly check that the region is not empty to make sure we
165 // maintain the "the alloc region cannot be empty" invariant.
166 assert_alloc_region(alloc_region != NULL && !alloc_region->is_empty(), "pre-condition");
167 assert_alloc_region(_alloc_region == _dummy_region &&
168 _used_bytes_before == 0 && _count == 0,
169 "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(alloc_region != NULL && !alloc_region->is_empty(), "pre-condition");
182
183 _alloc_region = alloc_region;
184 _alloc_region->set_allocation_context(allocation_context());
185 _count += 1;
186 trace("updated");
187 }
188
189 HeapRegion* G1AllocRegion::release() {
190 trace("releasing");
191 HeapRegion* alloc_region = _alloc_region;
192 retire(false /* fill_up */);
193 assert_alloc_region(_alloc_region == _dummy_region, "post-condition of retire()");
194 _alloc_region = NULL;
195 trace("released");
196 return (alloc_region == _dummy_region) ? NULL : alloc_region;
197 }
198
199 #ifndef PRODUCT
200 void G1AllocRegion::trace(const char* str, size_t min_word_size, size_t desired_word_size, size_t actual_word_size, HeapWord* result) {
201 // All the calls to trace that set either just the size or the size
202 // and the result are considered part of detailed tracing and are
203 // skipped during other tracing.
204
205 Log(gc, alloc, region) log;
206
207 if (!log.is_debug()) {
208 return;
209 }
210
211 bool detailed_info = log.is_trace();
212
213 if ((actual_word_size == 0 && result == NULL) || detailed_info) {
214 ResourceMark rm;
215 outputStream* out;
216 if (detailed_info) {
217 out = log.trace_stream();
218 } else {
219 out = log.debug_stream();
220 }
221
222 out->print("%s: %u ", _name, _count);
223
224 if (_alloc_region == NULL) {
225 out->print("NULL");
226 } else if (_alloc_region == _dummy_region) {
227 out->print("DUMMY");
228 } else {
229 out->print(HR_FORMAT, HR_FORMAT_PARAMS(_alloc_region));
230 }
231
232 out->print(" : %s", str);
233
234 if (detailed_info) {
235 if (result != NULL) {
236 out->print(" min " SIZE_FORMAT " desired " SIZE_FORMAT " actual " SIZE_FORMAT " " PTR_FORMAT,
237 min_word_size, desired_word_size, actual_word_size, p2i(result));
238 } else if (min_word_size != 0) {
239 out->print(" min " SIZE_FORMAT " desired " SIZE_FORMAT, min_word_size, desired_word_size);
240 }
241 }
242 out->cr();
243 }
244 }
245 #endif // PRODUCT
246
247 G1AllocRegion::G1AllocRegion(const char* name,
248 bool bot_updates)
249 : _name(name), _bot_updates(bot_updates),
250 _alloc_region(NULL), _count(0), _used_bytes_before(0),
251 _allocation_context(AllocationContext::system()) { }
252
253
254 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
255 bool force) {
256 return _g1h->new_mutator_alloc_region(word_size, force);
257 }
258
259 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
260 size_t allocated_bytes) {
261 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
262 }
263
264 HeapRegion* G1GCAllocRegion::allocate_new_region(size_t word_size,
265 bool force) {
266 assert(!force, "not supported for GC alloc regions");
267 return _g1h->new_gc_alloc_region(word_size, _purpose);
268 }
269
270 void G1GCAllocRegion::retire_region(HeapRegion* alloc_region,
271 size_t allocated_bytes) {
272 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, _purpose);
273 }
274
275 size_t G1GCAllocRegion::retire(bool fill_up) {
276 HeapRegion* retired = get();
277 size_t end_waste = G1AllocRegion::retire(fill_up);
278 // Do not count retirement of the dummy allocation region.
279 if (retired != NULL) {
280 _stats->add_region_end_waste(end_waste / HeapWordSize);
281 }
282 return end_waste;
283 }
284
285 HeapRegion* OldGCAllocRegion::release() {
286 HeapRegion* cur = get();
287 if (cur != NULL) {
288 // Determine how far we are from the next card boundary. If it is smaller than
289 // the minimum object size we can allocate into, expand into the next card.
290 HeapWord* top = cur->top();
291 HeapWord* aligned_top = align_up(top, BOTConstants::N_bytes);
292
293 size_t to_allocate_words = pointer_delta(aligned_top, top, HeapWordSize);
294
295 if (to_allocate_words != 0) {
296 // We are not at a card boundary. Fill up, possibly into the next, taking the
297 // end of the region and the minimum object size into account.
298 to_allocate_words = MIN2(pointer_delta(cur->end(), cur->top(), HeapWordSize),
299 MAX2(to_allocate_words, G1CollectedHeap::min_fill_size()));
300
301 // Skip allocation if there is not enough space to allocate even the smallest
302 // possible object. In this case this region will not be retained, so the
303 // original problem cannot occur.
304 if (to_allocate_words >= G1CollectedHeap::min_fill_size()) {
305 HeapWord* dummy = attempt_allocation(to_allocate_words, true /* bot_updates */);
306 CollectedHeap::fill_with_object(dummy, to_allocate_words);
307 }
308 }
309 }
310 return G1AllocRegion::release();
311 }