1 /*
2 * Copyright (c) 2014, 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_implementation/g1/g1Allocator.hpp"
27 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
28 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
29 #include "gc_implementation/g1/heapRegion.inline.hpp"
30 #include "gc_implementation/g1/heapRegionSet.inline.hpp"
31
32 size_t G1Allocator::desired_plab_size(InCSetState dest) {
33 size_t gclab_word_size = evac_stats(dest)->desired_plab_sz();
34 // Prevent humongous PLAB sizes for two reasons:
35 // * PLABs are allocated using a similar paths as oops, but should
36 // never be in a humongous region
37 // * Allowing humongous PLABs needlessly churns the region free lists
38 return MIN2(G1CollectedHeap::heap()->humongous_object_threshold_in_words(), gclab_word_size);
39 }
40
41 HeapWord* G1Allocator::survivor_attempt_allocation(size_t min_word_size,
42 size_t& word_size,
43 AllocationContext_t context) {
44 assert(!G1CollectedHeap::heap()->is_humongous(word_size),
45 "we should not be seeing humongous-size allocations in this path");
46
47 HeapWord* result = survivor_gc_alloc_region(context)->attempt_allocation(min_word_size,
48 word_size,
49 false /* bot_updates */);
50 if (result == NULL) {
51 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
52 result = survivor_gc_alloc_region(context)->attempt_allocation_locked(min_word_size,
53 word_size,
54 false /* bot_updates */);
55 }
56 if (result != NULL) {
57 _g1h->dirty_young_block(result, word_size);
58 }
59 return result;
60 }
61
62 HeapWord* G1Allocator::old_attempt_allocation(size_t min_word_size,
63 size_t& word_size,
64 AllocationContext_t context) {
65 assert(!G1CollectedHeap::heap()->is_humongous(word_size),
66 "we should not be seeing humongous-size allocations in this path");
67
68 HeapWord* result = old_gc_alloc_region(context)->attempt_allocation(min_word_size,
69 word_size,
70 true /* bot_updates */);
71 if (result == NULL) {
72 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
73 result = old_gc_alloc_region(context)->attempt_allocation_locked(min_word_size,
74 word_size,
75 true /* bot_updates */);
76 }
77 return result;
78 }
79
80
81 HeapWord* G1Allocator::par_allocate_during_gc(InCSetState dest,
82 size_t min_word_size,
83 size_t& word_size,
84 AllocationContext_t context) {
85 switch (dest.value()) {
86 case InCSetState::Young:
87 return survivor_attempt_allocation(min_word_size, word_size, context);
88 case InCSetState::Old:
89 return old_attempt_allocation(min_word_size, word_size, context);
90 default:
91 ShouldNotReachHere();
92 return NULL; // Keep some compilers happy
93 }
94 }
95
96 size_t G1Allocator::unsafe_max_tlab_alloc() {
97 // Return the remaining space in the cur alloc region, but not less than
98 // the min TLAB size.
99
100 // Also, this value can be at most the humongous object threshold,
101 // since we can't allow tlabs to grow big enough to accommodate
102 // humongous objects.
103
104 HeapRegion* hr = mutator_alloc_region(AllocationContext::current())->get();
105 size_t max_tlab = G1CollectedHeap::heap()->max_tlab_size() * wordSize;
106 if (hr == NULL) {
107 return max_tlab;
108 } else {
109 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
110 }
111 }
112
113 G1DefaultAllocator::G1DefaultAllocator(G1CollectedHeap* heap) :
114 G1Allocator(heap),
115 _retained_old_gc_alloc_region(NULL),
116 _survivor_plab_stats(YoungPLABSize, PLABWeight),
117 _old_plab_stats(OldPLABSize, PLABWeight),
118 _survivor_gc_alloc_region(evac_stats(InCSetState::Young)),
119 _old_gc_alloc_region(evac_stats(InCSetState::Old)) {
120 }
121
122 void G1DefaultAllocator::init_mutator_alloc_region() {
123 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
124 _mutator_alloc_region.init();
125 }
126
127 void G1DefaultAllocator::release_mutator_alloc_region() {
128 _mutator_alloc_region.release();
129 assert(_mutator_alloc_region.get() == NULL, "post-condition");
130 }
131
132 void G1Allocator::reuse_retained_old_region(EvacuationInfo& evacuation_info,
133 OldGCAllocRegion* old,
134 HeapRegion** retained_old) {
135 HeapRegion* retained_region = *retained_old;
136 *retained_old = NULL;
137
138 // We will discard the current GC alloc region if:
139 // a) it's in the collection set (it can happen!),
140 // b) it's already full (no point in using it),
141 // c) it's empty (this means that it was emptied during
142 // a cleanup and it should be on the free list now), or
143 // d) it's humongous (this means that it was emptied
144 // during a cleanup and was added to the free list, but
145 // has been subsequently used to allocate a humongous
146 // object that may be less than the region size).
147 if (retained_region != NULL &&
148 !retained_region->in_collection_set() &&
149 !(retained_region->top() == retained_region->end()) &&
150 !retained_region->is_empty() &&
151 !retained_region->is_humongous()) {
152 retained_region->record_timestamp();
153 // The retained region was added to the old region set when it was
154 // retired. We have to remove it now, since we don't allow regions
155 // we allocate to in the region sets. We'll re-add it later, when
156 // it's retired again.
157 _g1h->old_set_remove(retained_region);
158 bool during_im = _g1h->g1_policy()->during_initial_mark_pause();
159 retained_region->note_start_of_copying(during_im);
160 old->set(retained_region);
161 _g1h->hr_printer()->reuse(retained_region);
162 evacuation_info.set_alloc_regions_used_before(retained_region->used());
163 }
164 }
165
166 void G1DefaultAllocator::init_gc_alloc_regions(EvacuationInfo& evacuation_info) {
167 assert_at_safepoint(true /* should_be_vm_thread */);
168
169 _survivor_gc_alloc_region.init();
170 _old_gc_alloc_region.init();
171 reuse_retained_old_region(evacuation_info,
172 &_old_gc_alloc_region,
173 &_retained_old_gc_alloc_region);
174 }
175
176 void G1DefaultAllocator::release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info) {
177 AllocationContext_t context = AllocationContext::current();
178 evacuation_info.set_allocation_regions(survivor_gc_alloc_region(context)->count() +
179 old_gc_alloc_region(context)->count());
180 survivor_gc_alloc_region(context)->release();
181 // If we have an old GC alloc region to release, we'll save it in
182 // _retained_old_gc_alloc_region. If we don't
183 // _retained_old_gc_alloc_region will become NULL. This is what we
184 // want either way so no reason to check explicitly for either
185 // condition.
186 _retained_old_gc_alloc_region = old_gc_alloc_region(context)->release();
187 if (_retained_old_gc_alloc_region != NULL) {
188 _retained_old_gc_alloc_region->record_retained_region();
189 }
190
191 evac_stats(InCSetState::Young)->adjust_desired_plab_sz(no_of_gc_workers);
192 evac_stats(InCSetState::Old)->adjust_desired_plab_sz(no_of_gc_workers);
193 }
194
195 void G1DefaultAllocator::abandon_gc_alloc_regions() {
196 assert(survivor_gc_alloc_region(AllocationContext::current())->get() == NULL, "pre-condition");
197 assert(old_gc_alloc_region(AllocationContext::current())->get() == NULL, "pre-condition");
198 _retained_old_gc_alloc_region = NULL;
199 }
200
201 G1EvacStats* G1DefaultAllocator::evac_stats(InCSetState dest) {
202 switch (dest.value()) {
203 case InCSetState::Young:
204 return &_survivor_plab_stats;
205 case InCSetState::Old:
206 return &_old_plab_stats;
207 default:
208 ShouldNotReachHere();
209 return NULL; // Keep some compilers happy
210 }
211 }
212
213 G1PLAB::G1PLAB(size_t gclab_word_size) :
214 ParGCAllocBuffer(gclab_word_size), _retired(true) { }
215
216 HeapWord* PLABAllocator::allocate_direct_or_new_plab(InCSetState dest,
217 size_t word_sz,
218 AllocationContext_t context) {
219 size_t plab_word_size = _allocator->desired_plab_size(dest);
220 size_t required_in_plab = word_sz + ParGCAllocBuffer::AlignmentReserve;
221
222 // Only get a new PLAB if the allocation fits and it would not waste more than
223 // ParallelGCBufferWastePct in the existing buffer.
224 if ((required_in_plab <= plab_word_size) &&
225 (required_in_plab * 100 < plab_word_size * ParallelGCBufferWastePct)) {
226 G1PLAB* alloc_buf = alloc_buffer(dest, context);
227 alloc_buf->retire();
228
229 HeapWord* buf = _allocator->par_allocate_during_gc(dest,
230 required_in_plab,
231 plab_word_size,
232 context);
233 if (buf == NULL) {
234 return NULL; // Let caller handle allocation failure.
235 }
236 // Otherwise.
237 alloc_buf->set_word_size(plab_word_size);
238 alloc_buf->set_buf(buf);
239
240 HeapWord* const obj = alloc_buf->allocate(word_sz);
241 assert(obj != NULL, err_msg("PLAB should have been big enough, tried to allocate "
242 SIZE_FORMAT" with alignment reserve " SIZE_FORMAT" PLAB size "SIZE_FORMAT,
243 word_sz, ParGCAllocBuffer::AlignmentReserve, plab_word_size));
244 return obj;
245 } else {
246 HeapWord* result = _allocator->par_allocate_during_gc(dest, word_sz, context);
247 if (result != NULL) {
248 _inline_allocated[dest.value()] += word_sz;
249 }
250 return result;
251 }
252 }
253
254 void PLABAllocator::undo_allocation(InCSetState dest, HeapWord* obj, size_t word_sz, AllocationContext_t context) {
255 if (alloc_buffer(dest, context)->contains(obj)) {
256 assert(alloc_buffer(dest, context)->contains(obj + word_sz - 1),
257 "should contain whole object");
258 alloc_buffer(dest, context)->undo_allocation(obj, word_sz);
259 } else {
260 CollectedHeap::fill_with_object(obj, word_sz);
261 _undo_waste[dest.value()] += word_sz;
262 }
263 }
264
265 DefaultPLABAllocator::DefaultPLABAllocator(G1Allocator* allocator) :
266 PLABAllocator(allocator),
267 _surviving_alloc_buffer(allocator->desired_plab_size(InCSetState::Young)),
268 _tenured_alloc_buffer(allocator->desired_plab_size(InCSetState::Old)) {
269 for (uint state = 0; state < InCSetState::Num; state++) {
270 _alloc_buffers[state] = NULL;
271 }
272 _alloc_buffers[InCSetState::Young] = &_surviving_alloc_buffer;
273 _alloc_buffers[InCSetState::Old] = &_tenured_alloc_buffer;
274 }
275
276 size_t DefaultPLABAllocator::lab_waste(InCSetState value) const {
277 assert(value.is_valid_gen(), err_msg("Given CSetState " CSETSTATE_FORMAT" value must represent a generation", value.value()));
278 return _alloc_buffers[value.value()]->wasted();
279 }
280
281 void DefaultPLABAllocator::flush_stats_and_retire() {
282 for (uint state = 0; state < InCSetState::Num; state++) {
283 G1PLAB* const buf = _alloc_buffers[state];
284 if (buf != NULL) {
285 G1EvacStats* stats = _allocator->evac_stats(state);
286 buf->flush_and_retire_stats(stats);
287 stats->add_inline_allocated(_inline_allocated[state]);
288 stats->add_undo_waste(_undo_waste[state]);
289 _inline_allocated[state] = 0;
290 _undo_waste[state] = 0;
291 }
292 }
293 }