1/*
2 * Copyright (c) 2011, 2018, 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.hpp"
33#include "utilities/align.hpp"
34
35G1CollectedHeap* G1AllocRegion::_g1h = NULL;
36HeapRegion* G1AllocRegion::_dummy_region = NULL;
37
38void 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(dummy_region->allocate_no_bot_updates(1) == NULL, "should fail");
46 assert(dummy_region->allocate(1) == NULL, "should fail");
47 DEBUG_ONLY(size_t assert_tmp);
48 assert(dummy_region->par_allocate_no_bot_updates(1, 1, &assert_tmp) == NULL, "should fail");
49 assert(dummy_region->par_allocate(1, 1, &assert_tmp) == NULL, "should fail");
50
51 _g1h = g1h;
52 _dummy_region = dummy_region;
53}
54
55size_t G1AllocRegion::fill_up_remaining_space(HeapRegion* alloc_region) {
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);
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
98size_t G1AllocRegion::retire_internal(HeapRegion* alloc_region, bool fill_up) {
99 // We never have to check whether the active region is empty or not,
100 // and potentially free it if it is, given that it's guaranteed that
101 // it will never be empty.
102 size_t waste = 0;
103 assert_alloc_region(!alloc_region->is_empty(),
104 "the alloc region should never be empty");
105
106 if (fill_up) {
107 waste = fill_up_remaining_space(alloc_region);
108 }
109
110 assert_alloc_region(alloc_region->used() >= _used_bytes_before, "invariant");
111 size_t allocated_bytes = alloc_region->used() - _used_bytes_before;
112 retire_region(alloc_region, allocated_bytes);
113 _used_bytes_before = 0;
114
115 return waste;
116}
117
118size_t G1AllocRegion::retire(bool fill_up) {
119 assert_alloc_region(_alloc_region != NULL, "not initialized properly");
120
121 size_t waste = 0;
122
123 trace("retiring");
124 HeapRegion* alloc_region = _alloc_region;
125 if (alloc_region != _dummy_region) {
126 waste = retire_internal(alloc_region, fill_up);
127 reset_alloc_region();
128 }
129 trace("retired");
130
131 return waste;
132}
133
134HeapWord* G1AllocRegion::new_alloc_region_and_allocate(size_t word_size,
135 bool force) {
136 assert_alloc_region(_alloc_region == _dummy_region, "pre-condition");
137 assert_alloc_region(_used_bytes_before == 0, "pre-condition");
138
139 trace("attempting region allocation");
140 HeapRegion* new_alloc_region = allocate_new_region(word_size, force);
141 if (new_alloc_region != NULL) {
142 new_alloc_region->reset_pre_dummy_top();
143 // Need to do this before the allocation
144 _used_bytes_before = new_alloc_region->used();
145 HeapWord* result = allocate(new_alloc_region, word_size);
146 assert_alloc_region(result != NULL, "the allocation should succeeded");
147
148 OrderAccess::storestore();
149 // Note that we first perform the allocation and then we store the
150 // region in _alloc_region. This is the reason why an active region
151 // can never be empty.
152 update_alloc_region(new_alloc_region);
153 trace("region allocation successful");
154 return result;
155 } else {
156 trace("region allocation failed");
157 return NULL;
158 }
159 ShouldNotReachHere();
160}
161
162void G1AllocRegion::init() {
163 trace("initializing");
164 assert_alloc_region(_alloc_region == NULL && _used_bytes_before == 0, "pre-condition");
165 assert_alloc_region(_dummy_region != NULL, "should have been set");
166 _alloc_region = _dummy_region;
167 _count = 0;
168 trace("initialized");
169}
170
171void G1AllocRegion::set(HeapRegion* alloc_region) {
172 trace("setting");
173 // We explicitly check that the region is not empty to make sure we
174 // maintain the "the alloc region cannot be empty" invariant.
175 assert_alloc_region(alloc_region != NULL && !alloc_region->is_empty(), "pre-condition");
176 assert_alloc_region(_alloc_region == _dummy_region &&
177 _used_bytes_before == 0 && _count == 0,
178 "pre-condition");
179
180 _used_bytes_before = alloc_region->used();
181 _alloc_region = alloc_region;
182 _count += 1;
183 trace("set");
184}
185
186void G1AllocRegion::update_alloc_region(HeapRegion* alloc_region) {
187 trace("update");
188 // We explicitly check that the region is not empty to make sure we
189 // maintain the "the alloc region cannot be empty" invariant.
190 assert_alloc_region(alloc_region != NULL && !alloc_region->is_empty(), "pre-condition");
191
192 _alloc_region = alloc_region;
193 _count += 1;
194 trace("updated");
195}
196
197HeapRegion* G1AllocRegion::release() {
198 trace("releasing");
199 HeapRegion* alloc_region = _alloc_region;
200 retire(false /* fill_up */);
201 assert_alloc_region(_alloc_region == _dummy_region, "post-condition of retire()");
202 _alloc_region = NULL;
203 trace("released");
204 return (alloc_region == _dummy_region) ? NULL : alloc_region;
205}
206
207#ifndef PRODUCT
208void G1AllocRegion::trace(const char* str, size_t min_word_size, size_t desired_word_size, size_t actual_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 detailed tracing and are
211 // skipped during other tracing.
212
213 Log(gc, alloc, region) log;
214
215 if (!log.is_debug()) {
216 return;
217 }
218
219 bool detailed_info = log.is_trace();
220
221 if ((actual_word_size == 0 && result == NULL) || detailed_info) {
222 ResourceMark rm;
223 LogStream ls_trace(log.trace());
224 LogStream ls_debug(log.debug());
225 outputStream* out = detailed_info ? &ls_trace : &ls_debug;
226
227 out->print("%s: %u ", _name, _count);
228
229 if (_alloc_region == NULL) {
230 out->print("NULL");
231 } else if (_alloc_region == _dummy_region) {
232 out->print("DUMMY");
233 } else {
234 out->print(HR_FORMAT, HR_FORMAT_PARAMS(_alloc_region));
235 }
236
237 out->print(" : %s", str);
238
239 if (detailed_info) {
240 if (result != NULL) {
241 out->print(" min " SIZE_FORMAT " desired " SIZE_FORMAT " actual " SIZE_FORMAT " " PTR_FORMAT,
242 min_word_size, desired_word_size, actual_word_size, p2i(result));
243 } else if (min_word_size != 0) {
244 out->print(" min " SIZE_FORMAT " desired " SIZE_FORMAT, min_word_size, desired_word_size);
245 }
246 }
247 out->cr();
248 }
249}
250#endif // PRODUCT
251
252G1AllocRegion::G1AllocRegion(const char* name,
253 bool bot_updates)
254 : _alloc_region(NULL),
255 _count(0),
256 _used_bytes_before(0),
257 _bot_updates(bot_updates),
258 _name(name)
259 { }
260
261HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
262 bool force) {
263 return _g1h->new_mutator_alloc_region(word_size, force);
264}
265
266void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
267 size_t allocated_bytes) {
268 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
269}
270
271void MutatorAllocRegion::init() {
272 assert(_retained_alloc_region == NULL, "Pre-condition");
273 G1AllocRegion::init();
274 _wasted_bytes = 0;
275}
276
277bool MutatorAllocRegion::should_retain(HeapRegion* region) {
278 size_t free_bytes = region->free();
279 if (free_bytes < MinTLABSize) {
280 return false;
281 }
282
283 if (_retained_alloc_region != NULL &&
284 free_bytes < _retained_alloc_region->free()) {
285 return false;
286 }
287
288 return true;
289}
290
291size_t MutatorAllocRegion::retire(bool fill_up) {
292 size_t waste = 0;
293 trace("retiring");
294 HeapRegion* current_region = get();
295 if (current_region != NULL) {
296 // Retain the current region if it fits a TLAB and has more
297 // free than the currently retained region.
298 if (should_retain(current_region)) {
299 trace("mutator retained");
300 if (_retained_alloc_region != NULL) {
301 waste = retire_internal(_retained_alloc_region, true);
302 }
303 _retained_alloc_region = current_region;
304 } else {
305 waste = retire_internal(current_region, fill_up);
306 }
307 reset_alloc_region();
308 }
309
310 _wasted_bytes += waste;
311 trace("retired");
312 return waste;
313}
314
315size_t MutatorAllocRegion::used_in_alloc_regions() {
316 size_t used = 0;
317 HeapRegion* hr = get();
318 if (hr != NULL) {
319 used += hr->used();
320 }
321
322 hr = _retained_alloc_region;
323 if (hr != NULL) {
324 used += hr->used();
325 }
326 return used;
327}
328
329HeapRegion* MutatorAllocRegion::release() {
330 HeapRegion* ret = G1AllocRegion::release();
331
332 // The retained alloc region must be retired and this must be
333 // done after the above call to release the mutator alloc region,
334 // since it might update the _retained_alloc_region member.
335 if (_retained_alloc_region != NULL) {
336 _wasted_bytes += retire_internal(_retained_alloc_region, false);
337 _retained_alloc_region = NULL;
338 }
339 log_debug(gc, alloc, region)("Mutator Allocation stats, regions: %u, wasted size: " SIZE_FORMAT "%s (%4.1f%%)",
340 count(),
341 byte_size_in_proper_unit(_wasted_bytes),
342 proper_unit_for_byte_size(_wasted_bytes),
343 percent_of(_wasted_bytes, count() * HeapRegion::GrainBytes));
344 return ret;
345}
346
347HeapRegion* G1GCAllocRegion::allocate_new_region(size_t word_size,
348 bool force) {
349 assert(!force, "not supported for GC alloc regions");
350 return _g1h->new_gc_alloc_region(word_size, _purpose);
351}
352
353void G1GCAllocRegion::retire_region(HeapRegion* alloc_region,
354 size_t allocated_bytes) {
355 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, _purpose);
356}
357
358size_t G1GCAllocRegion::retire(bool fill_up) {
359 HeapRegion* retired = get();
360 size_t end_waste = G1AllocRegion::retire(fill_up);
361 // Do not count retirement of the dummy allocation region.
362 if (retired != NULL) {
363 _stats->add_region_end_waste(end_waste / HeapWordSize);
364 }
365 return end_waste;
366}
367
368HeapRegion* OldGCAllocRegion::release() {
369 HeapRegion* cur = get();
370 if (cur != NULL) {
371 // Determine how far we are from the next card boundary. If it is smaller than
372 // the minimum object size we can allocate into, expand into the next card.
373 HeapWord* top = cur->top();
374 HeapWord* aligned_top = align_up(top, BOTConstants::N_bytes);
375
376 size_t to_allocate_words = pointer_delta(aligned_top, top, HeapWordSize);
377
378 if (to_allocate_words != 0) {
379 // We are not at a card boundary. Fill up, possibly into the next, taking the
380 // end of the region and the minimum object size into account.
381 to_allocate_words = MIN2(pointer_delta(cur->end(), cur->top(), HeapWordSize),
382 MAX2(to_allocate_words, G1CollectedHeap::min_fill_size()));
383
384 // Skip allocation if there is not enough space to allocate even the smallest
385 // possible object. In this case this region will not be retained, so the
386 // original problem cannot occur.
387 if (to_allocate_words >= G1CollectedHeap::min_fill_size()) {
388 HeapWord* dummy = attempt_allocation(to_allocate_words);
389 CollectedHeap::fill_with_object(dummy, to_allocate_words);
390 }
391 }
392 }
393 return G1AllocRegion::release();
394}
395