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 #include "utilities/align.hpp"
34
35 G1CollectedHeap* G1AllocRegion::_g1h = NULL;
36 HeapRegion* G1AllocRegion::_dummy_region = NULL;
37
38 void G1AllocRegion::setup(G1CollectedHeap* g1h, HeapRegion* dummy_region) {
39 assert(_dummy_region == NULL, "should be set once");
40 assert(dummy_region != NULL, "pre-condition");
41 assert(dummy_region->free() == 0, "pre-condition");
42
43 // Make sure that any allocation attempt on this region will fail
44 // and will not trigger any asserts.
45 assert(allocate(dummy_region, 1, false) == NULL, "should fail");
46 assert(par_allocate(dummy_region, 1, false) == NULL, "should fail");
47 assert(allocate(dummy_region, 1, true) == NULL, "should fail");
48 assert(par_allocate(dummy_region, 1, true) == NULL, "should fail");
49
50 _g1h = g1h;
51 _dummy_region = dummy_region;
52 }
53
54 size_t G1AllocRegion::fill_up_remaining_space(HeapRegion* alloc_region,
55 bool bot_updates) {
56 assert(alloc_region != NULL && alloc_region != _dummy_region,
57 "pre-condition");
58 size_t result = 0;
59
60 // Other threads might still be trying to allocate using a CAS out
61 // of the region we are trying to retire, as they can do so without
62 // holding the lock. So, we first have to make sure that noone else
63 // can allocate out of it by doing a maximal allocation. Even if our
64 // CAS attempt fails a few times, we'll succeed sooner or later
65 // given that failed CAS attempts mean that the region is getting
66 // closed to being full.
67 size_t free_word_size = alloc_region->free() / HeapWordSize;
68
69 // This is the minimum free chunk we can turn into a dummy
70 // object. If the free space falls below this, then noone can
71 // allocate in this region anyway (all allocation requests will be
72 // of a size larger than this) so we won't have to perform the dummy
73 // allocation.
74 size_t min_word_size_to_fill = CollectedHeap::min_fill_size();
75
76 while (free_word_size >= min_word_size_to_fill) {
77 HeapWord* dummy = par_allocate(alloc_region, free_word_size, bot_updates);
78 if (dummy != NULL) {
79 // If the allocation was successful we should fill in the space.
80 CollectedHeap::fill_with_object(dummy, free_word_size);
81 alloc_region->set_pre_dummy_top(dummy);
82 result += free_word_size * HeapWordSize;
83 break;
84 }
85
86 free_word_size = alloc_region->free() / HeapWordSize;
87 // It's also possible that someone else beats us to the
88 // allocation and they fill up the region. In that case, we can
89 // just get out of the loop.
90 }
91 result += alloc_region->free();
92
93 assert(alloc_region->free() / HeapWordSize < min_word_size_to_fill,
94 "post-condition");
95 return result;
96 }
97
98 size_t G1AllocRegion::retire(bool fill_up) {
99 assert_alloc_region(_alloc_region != NULL, "not initialized properly");
100
101 size_t result = 0;
102
103 trace("retiring");
104 HeapRegion* alloc_region = _alloc_region;
105 if (alloc_region != _dummy_region) {
106 // We never have to check whether the active region is empty or not,
107 // and potentially free it if it is, given that it's guaranteed that
108 // it will never be empty.
109 assert_alloc_region(!alloc_region->is_empty(),
110 "the alloc region should never be empty");
111
112 if (fill_up) {
113 result = fill_up_remaining_space(alloc_region, _bot_updates);
114 }
115
116 assert_alloc_region(alloc_region->used() >= _used_bytes_before, "invariant");
117 size_t allocated_bytes = alloc_region->used() - _used_bytes_before;
118 retire_region(alloc_region, allocated_bytes);
119 _used_bytes_before = 0;
120 _alloc_region = _dummy_region;
121 }
122 trace("retired");
123
124 return result;
125 }
126
127 HeapWord* G1AllocRegion::new_alloc_region_and_allocate(size_t word_size,
128 bool force) {
129 assert_alloc_region(_alloc_region == _dummy_region, "pre-condition");
130 assert_alloc_region(_used_bytes_before == 0, "pre-condition");
131
132 trace("attempting region allocation");
133 HeapRegion* new_alloc_region = allocate_new_region(word_size, force);
134 if (new_alloc_region != NULL) {
135 new_alloc_region->reset_pre_dummy_top();
136 // Need to do this before the allocation
137 _used_bytes_before = new_alloc_region->used();
138 HeapWord* result = allocate(new_alloc_region, word_size, _bot_updates);
139 assert_alloc_region(result != NULL, "the allocation should succeeded");
140
141 OrderAccess::storestore();
142 // Note that we first perform the allocation and then we store the
143 // region in _alloc_region. This is the reason why an active region
144 // can never be empty.
145 update_alloc_region(new_alloc_region);
146 trace("region allocation successful");
147 return result;
148 } else {
149 trace("region allocation failed");
150 return NULL;
151 }
152 ShouldNotReachHere();
153 }
154
155 void G1AllocRegion::init() {
156 trace("initializing");
157 assert_alloc_region(_alloc_region == NULL && _used_bytes_before == 0, "pre-condition");
158 assert_alloc_region(_dummy_region != NULL, "should have been set");
159 _alloc_region = _dummy_region;
160 _count = 0;
161 trace("initialized");
162 }
163
164 void G1AllocRegion::set(HeapRegion* alloc_region) {
165 trace("setting");
166 // We explicitly check that the region is not empty to make sure we
167 // maintain the "the alloc region cannot be empty" invariant.
168 assert_alloc_region(alloc_region != NULL && !alloc_region->is_empty(), "pre-condition");
169 assert_alloc_region(_alloc_region == _dummy_region &&
170 _used_bytes_before == 0 && _count == 0,
171 "pre-condition");
172
173 _used_bytes_before = alloc_region->used();
174 _alloc_region = alloc_region;
175 _count += 1;
176 trace("set");
177 }
178
179 void G1AllocRegion::update_alloc_region(HeapRegion* alloc_region) {
180 trace("update");
181 // We explicitly check that the region is not empty to make sure we
182 // maintain the "the alloc region cannot be empty" invariant.
183 assert_alloc_region(alloc_region != NULL && !alloc_region->is_empty(), "pre-condition");
184
185 _alloc_region = alloc_region;
186 _alloc_region->set_allocation_context(allocation_context());
187 _count += 1;
188 trace("updated");
189 }
190
191 HeapRegion* G1AllocRegion::release() {
192 trace("releasing");
193 HeapRegion* alloc_region = _alloc_region;
194 retire(false /* fill_up */);
195 assert_alloc_region(_alloc_region == _dummy_region, "post-condition of retire()");
196 _alloc_region = NULL;
197 trace("released");
198 return (alloc_region == _dummy_region) ? NULL : alloc_region;
199 }
200
201 #ifndef PRODUCT
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 detailed tracing and are
205 // skipped during other tracing.
206
207 Log(gc, alloc, region) log;
208
209 if (!log.is_debug()) {
210 return;
211 }
212
213 bool detailed_info = log.is_trace();
214
215 if ((actual_word_size == 0 && result == NULL) || detailed_info) {
216 ResourceMark rm;
217 LogStream ls_trace(log.trace());
218 LogStream ls_debug(log.debug());
219 outputStream* out = detailed_info ? &ls_trace : &ls_debug;
220
221 out->print("%s: %u ", _name, _count);
222
223 if (_alloc_region == NULL) {
224 out->print("NULL");
225 } else if (_alloc_region == _dummy_region) {
226 out->print("DUMMY");
227 } else {
228 out->print(HR_FORMAT, HR_FORMAT_PARAMS(_alloc_region));
229 }
230
231 out->print(" : %s", str);
232
233 if (detailed_info) {
234 if (result != NULL) {
235 out->print(" min " SIZE_FORMAT " desired " SIZE_FORMAT " actual " SIZE_FORMAT " " PTR_FORMAT,
236 min_word_size, desired_word_size, actual_word_size, p2i(result));
237 } else if (min_word_size != 0) {
238 out->print(" min " SIZE_FORMAT " desired " SIZE_FORMAT, min_word_size, desired_word_size);
239 }
240 }
241 out->cr();
242 }
243 }
244 #endif // PRODUCT
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, _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 = align_up(top, BOTConstants::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 }