1 /*
2 * Copyright (c) 2018, Red Hat, Inc. and/or its affiliates.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation.
7 *
8 * This code is distributed in the hope that it will be useful, but WITHOUT
9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
11 * version 2 for more details (a copy is included in the LICENSE file that
12 * accompanied this code).
13 *
14 * You should have received a copy of the GNU General Public License version
15 * 2 along with this work; if not, write to the Free Software Foundation,
16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
17 *
18 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
19 * or visit www.oracle.com if you need additional information or have any
20 * questions.
21 *
22 */
23
24 #include "precompiled.hpp"
25 #include "gc_implementation/shenandoah/brooksPointer.hpp"
26 #include "gc_implementation/shenandoah/shenandoahCollectorPolicy.hpp"
27 #include "gc_implementation/shenandoah/shenandoahHeap.inline.hpp"
28 #include "gc_implementation/shenandoah/shenandoahHeapRegion.hpp"
29 #include "gc_implementation/shenandoah/shenandoahHeuristics.hpp"
30
31 int ShenandoahHeuristics::compare_by_garbage(RegionData a, RegionData b) {
32 if (a._garbage > b._garbage)
33 return -1;
34 else if (a._garbage < b._garbage)
35 return 1;
36 else return 0;
37 }
38
39 int ShenandoahHeuristics::compare_by_alloc_seq_ascending(RegionData a, RegionData b) {
40 if (a._seqnum_last_alloc == b._seqnum_last_alloc)
41 return 0;
42 else if (a._seqnum_last_alloc < b._seqnum_last_alloc)
43 return -1;
44 else return 1;
45 }
46
47 int ShenandoahHeuristics::compare_by_alloc_seq_descending(RegionData a, RegionData b) {
48 return -compare_by_alloc_seq_ascending(a, b);
49 }
50
51 int ShenandoahHeuristics::compare_by_connects(RegionConnections a, RegionConnections b) {
52 if (a._connections == b._connections)
53 return 0;
54 else if (a._connections < b._connections)
55 return -1;
56 else return 1;
57 }
58
59 ShenandoahHeuristics::ShenandoahHeuristics() :
60 _bytes_in_cset(0),
61 _degenerated_cycles_in_a_row(0),
62 _successful_cycles_in_a_row(0),
63 _region_data(NULL),
64 _region_data_size(0),
65 _region_connects(NULL),
66 _region_connects_size(0),
67 _update_refs_early(false),
68 _update_refs_adaptive(false),
69 _last_cycle_end(0)
70 {
71 if (strcmp(ShenandoahUpdateRefsEarly, "on") == 0 ||
72 strcmp(ShenandoahUpdateRefsEarly, "true") == 0 ) {
73 _update_refs_early = true;
74 } else if (strcmp(ShenandoahUpdateRefsEarly, "off") == 0 ||
75 strcmp(ShenandoahUpdateRefsEarly, "false") == 0 ) {
76 _update_refs_early = false;
77 } else if (strcmp(ShenandoahUpdateRefsEarly, "adaptive") == 0) {
78 _update_refs_adaptive = true;
79 _update_refs_early = true;
80 } else {
81 vm_exit_during_initialization("Unknown -XX:ShenandoahUpdateRefsEarly option: %s", ShenandoahUpdateRefsEarly);
82 }
83 }
84
85 ShenandoahHeuristics::~ShenandoahHeuristics() {
86 if (_region_data != NULL) {
87 FREE_C_HEAP_ARRAY(RegionGarbage, _region_data, mtGC);
88 }
89 }
90
91 ShenandoahHeuristics::RegionData* ShenandoahHeuristics::get_region_data_cache(size_t num) {
92 RegionData* res = _region_data;
93 if (res == NULL) {
94 res = NEW_C_HEAP_ARRAY(RegionData, num, mtGC);
95 _region_data = res;
96 _region_data_size = num;
97 } else if (_region_data_size < num) {
98 res = REALLOC_C_HEAP_ARRAY(RegionData, _region_data, num, mtGC);
99 _region_data = res;
100 _region_data_size = num;
101 }
102 return res;
103 }
104
105 ShenandoahHeuristics::RegionConnections* ShenandoahHeuristics::get_region_connects_cache(size_t num) {
106 RegionConnections* res = _region_connects;
107 if (res == NULL) {
108 res = NEW_C_HEAP_ARRAY(RegionConnections, num, mtGC);
109 _region_connects = res;
110 _region_connects_size = num;
111 } else if (_region_connects_size < num) {
112 res = REALLOC_C_HEAP_ARRAY(RegionConnections, _region_connects, num, mtGC);
113 _region_connects = res;
114 _region_connects_size = num;
115 }
116 return res;
117 }
118
119 void ShenandoahHeuristics::choose_collection_set(ShenandoahCollectionSet* collection_set) {
120 assert(collection_set->count() == 0, "Must be empty");
121 start_choose_collection_set();
122
123 ShenandoahHeap* heap = ShenandoahHeap::heap();
124
125 // Step 1. Build up the region candidates we care about, rejecting losers and accepting winners right away.
126
127 size_t num_regions = heap->num_regions();
128
129 RegionData* candidates = get_region_data_cache(num_regions);
130
131 size_t cand_idx = 0;
132
133 size_t total_garbage = 0;
134
135 size_t immediate_garbage = 0;
136 size_t immediate_regions = 0;
137
138 size_t free = 0;
139 size_t free_regions = 0;
140
141 for (size_t i = 0; i < num_regions; i++) {
142 ShenandoahHeapRegion* region = heap->get_region(i);
143
144 size_t garbage = region->garbage();
145 total_garbage += garbage;
146
147 if (region->is_empty()) {
148 free_regions++;
149 free += ShenandoahHeapRegion::region_size_bytes();
150 } else if (region->is_regular()) {
151 if (!region->has_live()) {
152 // We can recycle it right away and put it in the free set.
153 immediate_regions++;
154 immediate_garbage += garbage;
155 region->make_trash();
156 } else {
157 // This is our candidate for later consideration.
158 candidates[cand_idx]._region = region;
159 candidates[cand_idx]._garbage = garbage;
160 cand_idx++;
161 }
162 } else if (region->is_humongous_start()) {
163 // Reclaim humongous regions here, and count them as the immediate garbage
164 #ifdef ASSERT
165 bool reg_live = region->has_live();
166 bool bm_live = heap->is_marked_complete(oop(region->bottom() + BrooksPointer::word_size()));
167 assert(reg_live == bm_live,
168 err_msg("Humongous liveness and marks should agree. Region live: %s; Bitmap live: %s; Region Live Words: " SIZE_FORMAT,
169 BOOL_TO_STR(reg_live), BOOL_TO_STR(bm_live), region->get_live_data_words()));
170 #endif
171 if (!region->has_live()) {
172 heap->trash_humongous_region_at(region);
173
174 // Count only the start. Continuations would be counted on "trash" path
175 immediate_regions++;
176 immediate_garbage += garbage;
177 }
178 } else if (region->is_trash()) {
179 // Count in just trashed collection set, during coalesced CM-with-UR
180 immediate_regions++;
181 immediate_garbage += garbage;
182 }
183 }
184
185 // Step 2. Look back at garbage statistics, and decide if we want to collect anything,
186 // given the amount of immediately reclaimable garbage. If we do, figure out the collection set.
187
188 assert (immediate_garbage <= total_garbage,
189 err_msg("Cannot have more immediate garbage than total garbage: " SIZE_FORMAT "M vs " SIZE_FORMAT "M",
190 immediate_garbage / M, total_garbage / M));
191
192 size_t immediate_percent = total_garbage == 0 ? 0 : (immediate_garbage * 100 / total_garbage);
193
194 if (immediate_percent <= ShenandoahImmediateThreshold) {
195 choose_collection_set_from_regiondata(collection_set, candidates, cand_idx, immediate_garbage + free);
196 collection_set->update_region_status();
197
198 size_t cset_percent = total_garbage == 0 ? 0 : (collection_set->garbage() * 100 / total_garbage);
199 log_info(gc, ergo)("Collectable Garbage: "SIZE_FORMAT"M ("SIZE_FORMAT"%% of total), "SIZE_FORMAT"M CSet, "SIZE_FORMAT" CSet regions",
200 collection_set->garbage() / M, cset_percent, collection_set->live_data() / M, collection_set->count());
201 }
202 end_choose_collection_set();
203
204 log_info(gc, ergo)("Immediate Garbage: "SIZE_FORMAT"M ("SIZE_FORMAT"%% of total), "SIZE_FORMAT" regions",
205 immediate_garbage / M, immediate_percent, immediate_regions);
206 }
207
208 void ShenandoahHeuristics::record_gc_start() {
209 // Do nothing
210 }
211
212 void ShenandoahHeuristics::record_gc_end() {
213 // Do nothing
214 }
215
216 void ShenandoahHeuristics::record_cycle_start() {
217 // Do nothing
218 }
219
220 void ShenandoahHeuristics::record_cycle_end() {
221 _last_cycle_end = os::elapsedTime();
222 }
223
224 void ShenandoahHeuristics::record_phase_time(ShenandoahPhaseTimings::Phase phase, double secs) {
225 // Do nothing
226 }
227
228 void ShenandoahHeuristics::print_thresholds() {
229 // Do nothing
230 }
231
232 bool ShenandoahHeuristics::should_start_update_refs() {
233 return _update_refs_early;
234 }
235
236 bool ShenandoahHeuristics::update_refs() const {
237 return _update_refs_early;
238 }
239
240 bool ShenandoahHeuristics::should_degenerate_cycle() {
241 return _degenerated_cycles_in_a_row <= ShenandoahFullGCThreshold;
242 }
243
244 void ShenandoahHeuristics::record_success_concurrent() {
245 _degenerated_cycles_in_a_row = 0;
246 _successful_cycles_in_a_row++;
247 }
248
249 void ShenandoahHeuristics::record_success_degenerated() {
250 _degenerated_cycles_in_a_row++;
251 _successful_cycles_in_a_row = 0;
252 }
253
254 void ShenandoahHeuristics::record_success_full() {
255 _degenerated_cycles_in_a_row = 0;
256 _successful_cycles_in_a_row++;
257 }
258
259 void ShenandoahHeuristics::record_allocation_failure_gc() {
260 _bytes_in_cset = 0;
261 }
262
263 void ShenandoahHeuristics::record_explicit_gc() {
264 _bytes_in_cset = 0;
265 }
266
267 void ShenandoahHeuristics::record_peak_occupancy() {
268 // Nothing to do by default.
269 }
270
271 bool ShenandoahHeuristics::should_process_references() {
272 if (ShenandoahRefProcFrequency == 0) return false;
273 size_t cycle = ShenandoahHeap::heap()->shenandoahPolicy()->cycle_counter();
274 // Process references every Nth GC cycle.
275 return cycle % ShenandoahRefProcFrequency == 0;
276 }
277
278 bool ShenandoahHeuristics::should_unload_classes() {
279 if (ShenandoahUnloadClassesFrequency == 0) return false;
280 size_t cycle = ShenandoahHeap::heap()->shenandoahPolicy()->cycle_counter();
281 // Unload classes every Nth GC cycle.
282 // This should not happen in the same cycle as process_references to amortize costs.
283 // Offsetting by one is enough to break the rendezvous when periods are equal.
284 // When periods are not equal, offsetting by one is just as good as any other guess.
285 return (cycle + 1) % ShenandoahUnloadClassesFrequency == 0;
286 }
287
288 void ShenandoahHeuristics::initialize() {
289 // Nothing to do by default.
290 }