1 /*
2 * Copyright (c) 2018, 2020, Red Hat, Inc. All rights reserved.
3 * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 #include "precompiled.hpp"
27 #include "gc/shared/gcCause.hpp"
28 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
29 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
30 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
31 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
32 #include "logging/log.hpp"
33 #include "logging/logTag.hpp"
34 #include "runtime/globals_extension.hpp"
35 #include "utilities/quickSort.hpp"
36
37 // sort by decreasing garbage (so most garbage comes first)
38 int ShenandoahHeuristics::compare_by_garbage(RegionData a, RegionData b) {
39 if (a.get_garbage() > b.get_garbage()) {
40 return -1;
41 } else if (a.get_garbage() < b.get_garbage()) {
42 return 1;
43 } else {
44 return 0;
45 }
46 }
47
48 ShenandoahHeuristics::ShenandoahHeuristics(ShenandoahSpaceInfo* space_info) :
49 _space_info(space_info),
50 _region_data(nullptr),
51 _guaranteed_gc_interval(0),
52 _cycle_start(os::elapsedTime()),
53 _last_cycle_end(0),
54 _gc_times_learned(0),
55 _gc_time_penalties(0),
56 _gc_cycle_time_history(new TruncatedSeq(Moving_Average_Samples, ShenandoahAdaptiveDecayFactor)),
57 _metaspace_oom()
58 {
59 size_t num_regions = ShenandoahHeap::heap()->num_regions();
60 assert(num_regions > 0, "Sanity");
61
62 _region_data = NEW_C_HEAP_ARRAY(RegionData, num_regions, mtGC);
63 #ifdef ASSERT
64 for (size_t i = 0; i < num_regions; i++) {
65 _region_data[i].clear();
66 }
67 #endif
68 }
69
70 ShenandoahHeuristics::~ShenandoahHeuristics() {
71 FREE_C_HEAP_ARRAY(RegionGarbage, _region_data);
72 }
73
74 void ShenandoahHeuristics::choose_collection_set(ShenandoahCollectionSet* collection_set) {
75 assert(collection_set->is_empty(), "Must be empty");
76
77 ShenandoahHeap* heap = ShenandoahHeap::heap();
78
79 // Check all pinned regions have updated status before choosing the collection set.
80 heap->assert_pinned_region_status();
81
82 // Step 1. Build up the region candidates we care about, rejecting losers and accepting winners right away.
83
84 size_t num_regions = heap->num_regions();
85
86 RegionData* candidates = _region_data;
87
88 size_t cand_idx = 0;
89
90 size_t total_garbage = 0;
91
92 size_t immediate_garbage = 0;
93 size_t immediate_regions = 0;
94
95 size_t free = 0;
96 size_t free_regions = 0;
97
98 ShenandoahMarkingContext* const ctx = heap->complete_marking_context();
99
100 for (size_t i = 0; i < num_regions; i++) {
101 ShenandoahHeapRegion* region = heap->get_region(i);
102
103 size_t garbage = region->garbage();
104 total_garbage += garbage;
105
106 if (region->is_empty()) {
107 free_regions++;
108 free += ShenandoahHeapRegion::region_size_bytes();
109 } else if (region->is_regular()) {
110 if (!region->has_live()) {
111 // We can recycle it right away and put it in the free set.
112 immediate_regions++;
113 immediate_garbage += garbage;
114 region->make_trash_immediate();
115 } else {
116 // This is our candidate for later consideration.
117 candidates[cand_idx].set_region_and_garbage(region, garbage);
118 cand_idx++;
119 }
120 } else if (region->is_humongous_start()) {
121 // Reclaim humongous regions here, and count them as the immediate garbage
122 #ifdef ASSERT
123 bool reg_live = region->has_live();
124 bool bm_live = ctx->is_marked(cast_to_oop(region->bottom()));
125 assert(reg_live == bm_live,
126 "Humongous liveness and marks should agree. Region live: %s; Bitmap live: %s; Region Live Words: " SIZE_FORMAT,
127 BOOL_TO_STR(reg_live), BOOL_TO_STR(bm_live), region->get_live_data_words());
128 #endif
129 if (!region->has_live()) {
130 heap->trash_humongous_region_at(region);
131
132 // Count only the start. Continuations would be counted on "trash" path
133 immediate_regions++;
134 immediate_garbage += garbage;
135 }
136 } else if (region->is_trash()) {
137 // Count in just trashed collection set, during coalesced CM-with-UR
138 immediate_regions++;
139 immediate_garbage += garbage;
140 }
141 }
142
143 // Step 2. Look back at garbage statistics, and decide if we want to collect anything,
144 // given the amount of immediately reclaimable garbage. If we do, figure out the collection set.
145
146 assert (immediate_garbage <= total_garbage,
147 "Cannot have more immediate garbage than total garbage: " SIZE_FORMAT "%s vs " SIZE_FORMAT "%s",
148 byte_size_in_proper_unit(immediate_garbage), proper_unit_for_byte_size(immediate_garbage),
149 byte_size_in_proper_unit(total_garbage), proper_unit_for_byte_size(total_garbage));
150
151 size_t immediate_percent = (total_garbage == 0) ? 0 : (immediate_garbage * 100 / total_garbage);
152
153 if (immediate_percent <= ShenandoahImmediateThreshold) {
154 choose_collection_set_from_regiondata(collection_set, candidates, cand_idx, immediate_garbage + free);
155 }
156
157 size_t cset_percent = (total_garbage == 0) ? 0 : (collection_set->garbage() * 100 / total_garbage);
158 size_t collectable_garbage = collection_set->garbage() + immediate_garbage;
159 size_t collectable_garbage_percent = (total_garbage == 0) ? 0 : (collectable_garbage * 100 / total_garbage);
160
161 log_info(gc, ergo)("Collectable Garbage: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), "
162 "Immediate: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), " SIZE_FORMAT " regions, "
163 "CSet: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), " SIZE_FORMAT " regions",
164
165 byte_size_in_proper_unit(collectable_garbage),
166 proper_unit_for_byte_size(collectable_garbage),
167 collectable_garbage_percent,
168
169 byte_size_in_proper_unit(immediate_garbage),
170 proper_unit_for_byte_size(immediate_garbage),
171 immediate_percent,
172 immediate_regions,
173
174 byte_size_in_proper_unit(collection_set->garbage()),
175 proper_unit_for_byte_size(collection_set->garbage()),
176 cset_percent,
177 collection_set->count());
178 }
179
180 void ShenandoahHeuristics::record_cycle_start() {
181 _cycle_start = os::elapsedTime();
182 }
183
184 void ShenandoahHeuristics::record_cycle_end() {
185 _last_cycle_end = os::elapsedTime();
186 }
187
188 bool ShenandoahHeuristics::should_start_gc() {
189 // Perform GC to cleanup metaspace
190 if (has_metaspace_oom()) {
191 // Some of vmTestbase/metaspace tests depend on following line to count GC cycles
192 log_info(gc)("Trigger: %s", GCCause::to_string(GCCause::_metadata_GC_threshold));
193 return true;
194 }
195
196 if (_guaranteed_gc_interval > 0) {
197 double last_time_ms = (os::elapsedTime() - _last_cycle_end) * 1000;
198 if (last_time_ms > _guaranteed_gc_interval) {
199 log_info(gc)("Trigger (%s): Time since last GC (%.0f ms) is larger than guaranteed interval (" UINTX_FORMAT " ms)",
200 _space_info->name(), last_time_ms, _guaranteed_gc_interval);
201 return true;
202 }
203 }
204
205 return false;
206 }
207
208 bool ShenandoahHeuristics::should_degenerate_cycle() {
209 return ShenandoahHeap::heap()->shenandoah_policy()->consecutive_degenerated_gc_count() <= ShenandoahFullGCThreshold;
210 }
211
212 void ShenandoahHeuristics::adjust_penalty(intx step) {
213 assert(0 <= _gc_time_penalties && _gc_time_penalties <= 100,
214 "In range before adjustment: " INTX_FORMAT, _gc_time_penalties);
215
216 intx new_val = _gc_time_penalties + step;
217 if (new_val < 0) {
218 new_val = 0;
219 }
220 if (new_val > 100) {
221 new_val = 100;
222 }
223 _gc_time_penalties = new_val;
224
225 assert(0 <= _gc_time_penalties && _gc_time_penalties <= 100,
226 "In range after adjustment: " INTX_FORMAT, _gc_time_penalties);
227 }
228
229 void ShenandoahHeuristics::record_success_concurrent() {
230 _gc_cycle_time_history->add(elapsed_cycle_time());
231 _gc_times_learned++;
232
233 adjust_penalty(Concurrent_Adjust);
234 }
235
236 void ShenandoahHeuristics::record_success_degenerated() {
237 adjust_penalty(Degenerated_Penalty);
238 }
239
240 void ShenandoahHeuristics::record_success_full() {
241 adjust_penalty(Full_Penalty);
242 }
243
244 void ShenandoahHeuristics::record_allocation_failure_gc() {
245 // Do nothing.
246 }
247
248 void ShenandoahHeuristics::record_requested_gc() {
249 // Assume users call System.gc() when external state changes significantly,
250 // which forces us to re-learn the GC timings and allocation rates.
251 _gc_times_learned = 0;
252 }
253
254 bool ShenandoahHeuristics::can_unload_classes() {
255 return ClassUnloading;
256 }
257
258 bool ShenandoahHeuristics::should_unload_classes() {
259 if (!can_unload_classes()) return false;
260 if (has_metaspace_oom()) return true;
261 return ClassUnloadingWithConcurrentMark;
262 }
263
264 void ShenandoahHeuristics::initialize() {
265 // Nothing to do by default.
266 }
267
268 double ShenandoahHeuristics::elapsed_cycle_time() const {
269 return os::elapsedTime() - _cycle_start;
270 }