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 for (size_t i = 0; i < num_regions; i++) {
64 _region_data[i].clear();
65 }
66 }
67
68 ShenandoahHeuristics::~ShenandoahHeuristics() {
69 FREE_C_HEAP_ARRAY(RegionGarbage, _region_data);
70 }
71
72 void ShenandoahHeuristics::choose_collection_set(ShenandoahCollectionSet* collection_set) {
73 assert(collection_set->is_empty(), "Must be empty");
74
75 ShenandoahHeap* heap = ShenandoahHeap::heap();
76
77 // Check all pinned regions have updated status before choosing the collection set.
78 heap->assert_pinned_region_status();
79
80 // Step 1. Build up the region candidates we care about, rejecting losers and accepting winners right away.
81
82 size_t num_regions = heap->num_regions();
83
84 RegionData* candidates = _region_data;
85
86 size_t cand_idx = 0;
87
88 size_t total_garbage = 0;
89
90 size_t immediate_garbage = 0;
91 size_t immediate_regions = 0;
92
93 size_t free = 0;
94 size_t free_regions = 0;
95
96 ShenandoahMarkingContext* const ctx = heap->complete_marking_context();
97
98 for (size_t i = 0; i < num_regions; i++) {
99 ShenandoahHeapRegion* region = heap->get_region(i);
100
101 size_t garbage = region->garbage();
102 total_garbage += garbage;
103
104 if (region->is_empty()) {
105 free_regions++;
106 free += ShenandoahHeapRegion::region_size_bytes();
107 } else if (region->is_regular()) {
108 if (!region->has_live()) {
109 // We can recycle it right away and put it in the free set.
110 immediate_regions++;
111 immediate_garbage += garbage;
112 region->make_trash_immediate();
113 } else {
114 // This is our candidate for later consideration.
115 candidates[cand_idx].set_region_and_garbage(region, garbage);
116 cand_idx++;
117 }
118 } else if (region->is_humongous_start()) {
119 // Reclaim humongous regions here, and count them as the immediate garbage
120 #ifdef ASSERT
121 bool reg_live = region->has_live();
122 bool bm_live = ctx->is_marked(cast_to_oop(region->bottom()));
123 assert(reg_live == bm_live,
124 "Humongous liveness and marks should agree. Region live: %s; Bitmap live: %s; Region Live Words: " SIZE_FORMAT,
125 BOOL_TO_STR(reg_live), BOOL_TO_STR(bm_live), region->get_live_data_words());
126 #endif
127 if (!region->has_live()) {
128 heap->trash_humongous_region_at(region);
129
130 // Count only the start. Continuations would be counted on "trash" path
131 immediate_regions++;
132 immediate_garbage += garbage;
133 }
134 } else if (region->is_trash()) {
135 // Count in just trashed collection set, during coalesced CM-with-UR
136 immediate_regions++;
137 immediate_garbage += garbage;
138 }
139 }
140
141 // Step 2. Look back at garbage statistics, and decide if we want to collect anything,
142 // given the amount of immediately reclaimable garbage. If we do, figure out the collection set.
143
144 assert (immediate_garbage <= total_garbage,
145 "Cannot have more immediate garbage than total garbage: " SIZE_FORMAT "%s vs " SIZE_FORMAT "%s",
146 byte_size_in_proper_unit(immediate_garbage), proper_unit_for_byte_size(immediate_garbage),
147 byte_size_in_proper_unit(total_garbage), proper_unit_for_byte_size(total_garbage));
148
149 size_t immediate_percent = (total_garbage == 0) ? 0 : (immediate_garbage * 100 / total_garbage);
150
151 if (immediate_percent <= ShenandoahImmediateThreshold) {
152 choose_collection_set_from_regiondata(collection_set, candidates, cand_idx, immediate_garbage + free);
153 }
154
155 size_t cset_percent = (total_garbage == 0) ? 0 : (collection_set->garbage() * 100 / total_garbage);
156 size_t collectable_garbage = collection_set->garbage() + immediate_garbage;
157 size_t collectable_garbage_percent = (total_garbage == 0) ? 0 : (collectable_garbage * 100 / total_garbage);
158
159 log_info(gc, ergo)("Collectable Garbage: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), "
160 "Immediate: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), " SIZE_FORMAT " regions, "
161 "CSet: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), " SIZE_FORMAT " regions",
162
163 byte_size_in_proper_unit(collectable_garbage),
164 proper_unit_for_byte_size(collectable_garbage),
165 collectable_garbage_percent,
166
167 byte_size_in_proper_unit(immediate_garbage),
168 proper_unit_for_byte_size(immediate_garbage),
169 immediate_percent,
170 immediate_regions,
171
172 byte_size_in_proper_unit(collection_set->garbage()),
173 proper_unit_for_byte_size(collection_set->garbage()),
174 cset_percent,
175 collection_set->count());
176 }
177
178 void ShenandoahHeuristics::record_cycle_start() {
179 _cycle_start = os::elapsedTime();
180 }
181
182 void ShenandoahHeuristics::record_cycle_end() {
183 _last_cycle_end = os::elapsedTime();
184 }
185
186 bool ShenandoahHeuristics::should_start_gc() {
187 // Perform GC to cleanup metaspace
188 if (has_metaspace_oom()) {
189 // Some of vmTestbase/metaspace tests depend on following line to count GC cycles
190 log_trigger("%s", GCCause::to_string(GCCause::_metadata_GC_threshold));
191 return true;
192 }
193
194 if (_guaranteed_gc_interval > 0) {
195 double last_time_ms = (os::elapsedTime() - _last_cycle_end) * 1000;
196 if (last_time_ms > _guaranteed_gc_interval) {
197 log_trigger("Time since last GC (%.0f ms) is larger than guaranteed interval (" UINTX_FORMAT " ms)",
198 last_time_ms, _guaranteed_gc_interval);
199 return true;
200 }
201 }
202
203 return false;
204 }
205
206 bool ShenandoahHeuristics::should_degenerate_cycle() {
207 return ShenandoahHeap::heap()->shenandoah_policy()->consecutive_degenerated_gc_count() <= ShenandoahFullGCThreshold;
208 }
209
210 void ShenandoahHeuristics::adjust_penalty(intx step) {
211 assert(0 <= _gc_time_penalties && _gc_time_penalties <= 100,
212 "In range before adjustment: " INTX_FORMAT, _gc_time_penalties);
213
214 intx new_val = _gc_time_penalties + step;
215 if (new_val < 0) {
216 new_val = 0;
217 }
218 if (new_val > 100) {
219 new_val = 100;
220 }
221 _gc_time_penalties = new_val;
222
223 assert(0 <= _gc_time_penalties && _gc_time_penalties <= 100,
224 "In range after adjustment: " INTX_FORMAT, _gc_time_penalties);
225 }
226
227 void ShenandoahHeuristics::log_trigger(const char* fmt, ...) {
228 LogTarget(Info, gc) lt;
229 if (lt.is_enabled()) {
230 ResourceMark rm;
231 LogStream ls(lt);
232 ls.print_raw("Trigger", 7);
233 if (ShenandoahHeap::heap()->mode()->is_generational()) {
234 ls.print(" (%s)", _space_info->name());
235 }
236 ls.print_raw(": ", 2);
237 va_list va;
238 va_start(va, fmt);
239 ls.vprint(fmt, va);
240 va_end(va);
241 ls.cr();
242 }
243 }
244
245 void ShenandoahHeuristics::record_success_concurrent() {
246 _gc_cycle_time_history->add(elapsed_cycle_time());
247 _gc_times_learned++;
248
249 adjust_penalty(Concurrent_Adjust);
250 }
251
252 void ShenandoahHeuristics::record_success_degenerated() {
253 adjust_penalty(Degenerated_Penalty);
254 }
255
256 void ShenandoahHeuristics::record_success_full() {
257 adjust_penalty(Full_Penalty);
258 }
259
260 void ShenandoahHeuristics::record_allocation_failure_gc() {
261 // Do nothing.
262 }
263
264 void ShenandoahHeuristics::record_requested_gc() {
265 // Assume users call System.gc() when external state changes significantly,
266 // which forces us to re-learn the GC timings and allocation rates.
267 _gc_times_learned = 0;
268 }
269
270 bool ShenandoahHeuristics::can_unload_classes() {
271 return ClassUnloading;
272 }
273
274 bool ShenandoahHeuristics::should_unload_classes() {
275 if (!can_unload_classes()) return false;
276 if (has_metaspace_oom()) return true;
277 return ClassUnloadingWithConcurrentMark;
278 }
279
280 void ShenandoahHeuristics::initialize() {
281 // Nothing to do by default.
282 }
283
284 double ShenandoahHeuristics::elapsed_cycle_time() const {
285 return os::elapsedTime() - _cycle_start;
286 }