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