1 /*
2 * Copyright (c) 2018, 2020, Red Hat, Inc. 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/shared/gcCause.hpp"
27 #include "gc/shenandoah/shenandoahCollectionSet.inline.hpp"
28 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
29 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
30 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
31 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
32 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
33 #include "logging/log.hpp"
34 #include "logging/logTag.hpp"
35 #include "runtime/globals_extension.hpp"
36
37 int ShenandoahHeuristics::compare_by_garbage(RegionData a, RegionData b) {
38 if (a._garbage > b._garbage)
39 return -1;
40 else if (a._garbage < b._garbage)
41 return 1;
42 else return 0;
43 }
44
45 ShenandoahHeuristics::ShenandoahHeuristics() :
46 _region_data(nullptr),
47 _degenerated_cycles_in_a_row(0),
48 _successful_cycles_in_a_row(0),
49 _cycle_start(os::elapsedTime()),
50 _last_cycle_end(0),
51 _gc_times_learned(0),
52 _gc_time_penalties(0),
53 _gc_time_history(new TruncatedSeq(10, ShenandoahAdaptiveDecayFactor)),
54 _metaspace_oom()
55 {
56 size_t num_regions = ShenandoahHeap::heap()->num_regions();
57 assert(num_regions > 0, "Sanity");
58
59 _region_data = NEW_C_HEAP_ARRAY(RegionData, num_regions, mtGC);
60 }
61
62 ShenandoahHeuristics::~ShenandoahHeuristics() {
63 FREE_C_HEAP_ARRAY(RegionGarbage, _region_data);
64 }
65
66 void ShenandoahHeuristics::choose_collection_set(ShenandoahCollectionSet* collection_set) {
67 assert(collection_set->count() == 0, "Must be empty");
68
69 ShenandoahHeap* heap = ShenandoahHeap::heap();
70
71 // Check all pinned regions have updated status before choosing the collection set.
72 heap->assert_pinned_region_status();
73
74 // Step 1. Build up the region candidates we care about, rejecting losers and accepting winners right away.
75
76 size_t num_regions = heap->num_regions();
77
78 RegionData* candidates = _region_data;
79
80 size_t cand_idx = 0;
81
82 size_t total_garbage = 0;
83
84 size_t immediate_garbage = 0;
85 size_t immediate_regions = 0;
86
87 size_t free = 0;
88 size_t free_regions = 0;
89
90 ShenandoahMarkingContext* const ctx = heap->complete_marking_context();
91
92 for (size_t i = 0; i < num_regions; i++) {
93 ShenandoahHeapRegion* region = heap->get_region(i);
94
95 size_t garbage = region->garbage();
96 total_garbage += garbage;
97
98 if (region->is_empty()) {
99 free_regions++;
100 free += ShenandoahHeapRegion::region_size_bytes();
101 } else if (region->is_regular()) {
102 if (!region->has_live()) {
103 // We can recycle it right away and put it in the free set.
104 immediate_regions++;
105 immediate_garbage += garbage;
106 region->make_trash_immediate();
107 } else {
108 // This is our candidate for later consideration.
109 candidates[cand_idx]._region = region;
110 candidates[cand_idx]._garbage = garbage;
111 cand_idx++;
112 }
113 } else if (region->is_humongous_start()) {
114 // Reclaim humongous regions here, and count them as the immediate garbage
115 #ifdef ASSERT
116 bool reg_live = region->has_live();
117 bool bm_live = ctx->is_marked(cast_to_oop(region->bottom()));
118 assert(reg_live == bm_live,
119 "Humongous liveness and marks should agree. Region live: %s; Bitmap live: %s; Region Live Words: " SIZE_FORMAT,
120 BOOL_TO_STR(reg_live), BOOL_TO_STR(bm_live), region->get_live_data_words());
121 #endif
122 if (!region->has_live()) {
123 heap->trash_humongous_region_at(region);
124
125 // Count only the start. Continuations would be counted on "trash" path
126 immediate_regions++;
127 immediate_garbage += garbage;
128 }
129 } else if (region->is_trash()) {
130 // Count in just trashed collection set, during coalesced CM-with-UR
131 immediate_regions++;
132 immediate_garbage += garbage;
133 }
134 }
135
136 // Step 2. Look back at garbage statistics, and decide if we want to collect anything,
137 // given the amount of immediately reclaimable garbage. If we do, figure out the collection set.
138
139 assert (immediate_garbage <= total_garbage,
140 "Cannot have more immediate garbage than total garbage: " SIZE_FORMAT "%s vs " SIZE_FORMAT "%s",
141 byte_size_in_proper_unit(immediate_garbage), proper_unit_for_byte_size(immediate_garbage),
142 byte_size_in_proper_unit(total_garbage), proper_unit_for_byte_size(total_garbage));
143
144 size_t immediate_percent = (total_garbage == 0) ? 0 : (immediate_garbage * 100 / total_garbage);
145
146 if (immediate_percent <= ShenandoahImmediateThreshold) {
147 choose_collection_set_from_regiondata(collection_set, candidates, cand_idx, immediate_garbage + free);
148 }
149
150 size_t cset_percent = (total_garbage == 0) ? 0 : (collection_set->garbage() * 100 / total_garbage);
151
152 size_t collectable_garbage = collection_set->garbage() + immediate_garbage;
153 size_t collectable_garbage_percent = (total_garbage == 0) ? 0 : (collectable_garbage * 100 / total_garbage);
154
155 log_info(gc, ergo)("Collectable Garbage: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), "
156 "Immediate: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), "
157 "CSet: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%)",
158
159 byte_size_in_proper_unit(collectable_garbage),
160 proper_unit_for_byte_size(collectable_garbage),
161 collectable_garbage_percent,
162
163 byte_size_in_proper_unit(immediate_garbage),
164 proper_unit_for_byte_size(immediate_garbage),
165 immediate_percent,
166
167 byte_size_in_proper_unit(collection_set->garbage()),
168 proper_unit_for_byte_size(collection_set->garbage()),
169 cset_percent);
170 }
171
172 void ShenandoahHeuristics::record_cycle_start() {
173 _cycle_start = os::elapsedTime();
174 }
175
176 void ShenandoahHeuristics::record_cycle_end() {
177 _last_cycle_end = os::elapsedTime();
178 }
179
180 bool ShenandoahHeuristics::should_start_gc() {
181 // Perform GC to cleanup metaspace
182 if (has_metaspace_oom()) {
183 // Some of vmTestbase/metaspace tests depend on following line to count GC cycles
184 log_info(gc)("Trigger: %s", GCCause::to_string(GCCause::_metadata_GC_threshold));
185 return true;
186 }
187
188 if (ShenandoahGuaranteedGCInterval > 0) {
189 double last_time_ms = (os::elapsedTime() - _last_cycle_end) * 1000;
190 if (last_time_ms > ShenandoahGuaranteedGCInterval) {
191 log_info(gc)("Trigger: Time since last GC (%.0f ms) is larger than guaranteed interval (" UINTX_FORMAT " ms)",
192 last_time_ms, ShenandoahGuaranteedGCInterval);
193 return true;
194 }
195 }
196
197 return false;
198 }
199
200 bool ShenandoahHeuristics::should_degenerate_cycle() {
201 return _degenerated_cycles_in_a_row <= ShenandoahFullGCThreshold;
202 }
203
204 void ShenandoahHeuristics::adjust_penalty(intx step) {
205 assert(0 <= _gc_time_penalties && _gc_time_penalties <= 100,
206 "In range before adjustment: " INTX_FORMAT, _gc_time_penalties);
207
208 intx new_val = _gc_time_penalties + step;
209 if (new_val < 0) {
210 new_val = 0;
211 }
212 if (new_val > 100) {
213 new_val = 100;
214 }
215 _gc_time_penalties = new_val;
216
217 assert(0 <= _gc_time_penalties && _gc_time_penalties <= 100,
218 "In range after adjustment: " INTX_FORMAT, _gc_time_penalties);
219 }
220
221 void ShenandoahHeuristics::record_success_concurrent() {
222 _degenerated_cycles_in_a_row = 0;
223 _successful_cycles_in_a_row++;
224
225 _gc_time_history->add(time_since_last_gc());
226 _gc_times_learned++;
227
228 adjust_penalty(Concurrent_Adjust);
229 }
230
231 void ShenandoahHeuristics::record_success_degenerated() {
232 _degenerated_cycles_in_a_row++;
233 _successful_cycles_in_a_row = 0;
234
235 adjust_penalty(Degenerated_Penalty);
236 }
237
238 void ShenandoahHeuristics::record_success_full() {
239 _degenerated_cycles_in_a_row = 0;
240 _successful_cycles_in_a_row++;
241
242 adjust_penalty(Full_Penalty);
243 }
244
245 void ShenandoahHeuristics::record_allocation_failure_gc() {
246 // Do nothing.
247 }
248
249 void ShenandoahHeuristics::record_requested_gc() {
250 // Assume users call System.gc() when external state changes significantly,
251 // which forces us to re-learn the GC timings and allocation rates.
252 _gc_times_learned = 0;
253 }
254
255 bool ShenandoahHeuristics::can_unload_classes() {
256 if (!ClassUnloading) return false;
257 return true;
258 }
259
260 bool ShenandoahHeuristics::should_unload_classes() {
261 if (!can_unload_classes()) return false;
262 if (has_metaspace_oom()) return true;
263 return ClassUnloadingWithConcurrentMark;
264 }
265
266 void ShenandoahHeuristics::initialize() {
267 // Nothing to do by default.
268 }
269
270 double ShenandoahHeuristics::time_since_last_gc() const {
271 return os::elapsedTime() - _cycle_start;
272 }