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 _start_gc_is_pending(false),
50 _declined_trigger_count(0),
51 _most_recent_declined_trigger_count(0),
52 _space_info(space_info),
53 _region_data(nullptr),
54 _guaranteed_gc_interval(0),
55 _cycle_start(os::elapsedTime()),
56 _last_cycle_end(0),
57 _gc_times_learned(0),
58 _gc_time_penalties(0),
59 _gc_cycle_time_history(new TruncatedSeq(Moving_Average_Samples, ShenandoahAdaptiveDecayFactor)),
60 _metaspace_oom()
61 {
62 size_t num_regions = ShenandoahHeap::heap()->num_regions();
63 assert(num_regions > 0, "Sanity");
64
65 _region_data = NEW_C_HEAP_ARRAY(RegionData, num_regions, mtGC);
66 for (size_t i = 0; i < num_regions; i++) {
67 _region_data[i].clear();
68 }
69 }
70
71 ShenandoahHeuristics::~ShenandoahHeuristics() {
72 FREE_C_HEAP_ARRAY(RegionGarbage, _region_data);
73 }
74
75 void ShenandoahHeuristics::choose_collection_set(ShenandoahCollectionSet* collection_set) {
76 assert(collection_set->is_empty(), "Must be empty");
77
78 ShenandoahHeap* heap = ShenandoahHeap::heap();
79
80 // Check all pinned regions have updated status before choosing the collection set.
81 heap->assert_pinned_region_status();
82
83 // Step 1. Build up the region candidates we care about, rejecting losers and accepting winners right away.
84
85 size_t num_regions = heap->num_regions();
86
87 RegionData* candidates = _region_data;
88
89 size_t cand_idx = 0;
90
91 size_t total_garbage = 0;
92
93 size_t immediate_garbage = 0;
94 size_t immediate_regions = 0;
95
96 size_t free = 0;
97 size_t free_regions = 0;
98
99 ShenandoahMarkingContext* const ctx = heap->complete_marking_context();
100
101 for (size_t i = 0; i < num_regions; i++) {
102 ShenandoahHeapRegion* region = heap->get_region(i);
103
104 size_t garbage = region->garbage();
105 total_garbage += garbage;
106
107 if (region->is_empty()) {
108 free_regions++;
109 free += ShenandoahHeapRegion::region_size_bytes();
110 } else if (region->is_regular()) {
111 if (!region->has_live()) {
112 // We can recycle it right away and put it in the free set.
113 immediate_regions++;
114 immediate_garbage += garbage;
115 region->make_trash_immediate();
116 } else {
117 // This is our candidate for later consideration.
118 candidates[cand_idx].set_region_and_garbage(region, garbage);
119 cand_idx++;
120 }
121 } else if (region->is_humongous_start()) {
122 // Reclaim humongous regions here, and count them as the immediate garbage
123 #ifdef ASSERT
124 bool reg_live = region->has_live();
125 bool bm_live = ctx->is_marked(cast_to_oop(region->bottom()));
126 assert(reg_live == bm_live,
127 "Humongous liveness and marks should agree. Region live: %s; Bitmap live: %s; Region Live Words: " SIZE_FORMAT,
128 BOOL_TO_STR(reg_live), BOOL_TO_STR(bm_live), region->get_live_data_words());
129 #endif
130 if (!region->has_live()) {
131 heap->trash_humongous_region_at(region);
132
133 // Count only the start. Continuations would be counted on "trash" path
134 immediate_regions++;
135 immediate_garbage += garbage;
136 }
137 } else if (region->is_trash()) {
138 // Count in just trashed collection set, during coalesced CM-with-UR
139 immediate_regions++;
140 immediate_garbage += garbage;
141 }
142 }
143
144 // Step 2. Look back at garbage statistics, and decide if we want to collect anything,
145 // given the amount of immediately reclaimable garbage. If we do, figure out the collection set.
146
147 assert (immediate_garbage <= total_garbage,
148 "Cannot have more immediate garbage than total garbage: " SIZE_FORMAT "%s vs " SIZE_FORMAT "%s",
149 byte_size_in_proper_unit(immediate_garbage), proper_unit_for_byte_size(immediate_garbage),
150 byte_size_in_proper_unit(total_garbage), proper_unit_for_byte_size(total_garbage));
151
152 size_t immediate_percent = (total_garbage == 0) ? 0 : (immediate_garbage * 100 / total_garbage);
153
154 if (immediate_percent <= ShenandoahImmediateThreshold) {
155 choose_collection_set_from_regiondata(collection_set, candidates, cand_idx, immediate_garbage + free);
156 }
157
158 size_t cset_percent = (total_garbage == 0) ? 0 : (collection_set->garbage() * 100 / total_garbage);
159 size_t collectable_garbage = collection_set->garbage() + immediate_garbage;
160 size_t collectable_garbage_percent = (total_garbage == 0) ? 0 : (collectable_garbage * 100 / total_garbage);
161
162 log_info(gc, ergo)("Collectable Garbage: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), "
163 "Immediate: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), " SIZE_FORMAT " regions, "
164 "CSet: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), " SIZE_FORMAT " regions",
165
166 byte_size_in_proper_unit(collectable_garbage),
167 proper_unit_for_byte_size(collectable_garbage),
168 collectable_garbage_percent,
169
170 byte_size_in_proper_unit(immediate_garbage),
171 proper_unit_for_byte_size(immediate_garbage),
172 immediate_percent,
173 immediate_regions,
174
175 byte_size_in_proper_unit(collection_set->garbage()),
176 proper_unit_for_byte_size(collection_set->garbage()),
177 cset_percent,
178 collection_set->count());
179 }
180
181 void ShenandoahHeuristics::record_cycle_start() {
182 _cycle_start = os::elapsedTime();
183 }
184
185 void ShenandoahHeuristics::record_cycle_end() {
186 _last_cycle_end = os::elapsedTime();
187 }
188
189 bool ShenandoahHeuristics::should_start_gc() {
190 if (_start_gc_is_pending) {
191 log_trigger("GC start is already pending");
192 return true;
193 }
194 // Perform GC to cleanup metaspace
195 if (has_metaspace_oom()) {
196 // Some of vmTestbase/metaspace tests depend on following line to count GC cycles
197 log_trigger("%s", GCCause::to_string(GCCause::_metadata_GC_threshold));
198 accept_trigger();
199 return true;
200 }
201
202 if (_guaranteed_gc_interval > 0) {
203 double last_time_ms = (os::elapsedTime() - _last_cycle_end) * 1000;
204 if (last_time_ms > _guaranteed_gc_interval) {
205 log_trigger("Time since last GC (%.0f ms) is larger than guaranteed interval (" UINTX_FORMAT " ms)",
206 last_time_ms, _guaranteed_gc_interval);
207 accept_trigger();
208 return true;
209 }
210 }
211 decline_trigger();
212 return false;
213 }
214
215 bool ShenandoahHeuristics::should_degenerate_cycle() {
216 return ShenandoahHeap::heap()->shenandoah_policy()->consecutive_degenerated_gc_count() <= ShenandoahFullGCThreshold;
217 }
218
219 void ShenandoahHeuristics::adjust_penalty(intx step) {
220 assert(0 <= _gc_time_penalties && _gc_time_penalties <= 100,
221 "In range before adjustment: " INTX_FORMAT, _gc_time_penalties);
222
223 if ((_most_recent_declined_trigger_count <= Penalty_Free_Declinations) && (step > 0)) {
224 // Don't penalize if heuristics are not responsible for a negative outcome. Allow Penalty_Free_Declinations following
225 // previous GC for self calibration without penalty.
226 step = 0;
227 }
228
229 intx new_val = _gc_time_penalties + step;
230 if (new_val < 0) {
231 new_val = 0;
232 }
233 if (new_val > 100) {
234 new_val = 100;
235 }
236 _gc_time_penalties = new_val;
237
238 assert(0 <= _gc_time_penalties && _gc_time_penalties <= 100,
239 "In range after adjustment: " INTX_FORMAT, _gc_time_penalties);
240 }
241
242 void ShenandoahHeuristics::log_trigger(const char* fmt, ...) {
243 LogTarget(Info, gc) lt;
244 if (lt.is_enabled()) {
245 ResourceMark rm;
246 LogStream ls(lt);
247 ls.print_raw("Trigger", 7);
248 if (ShenandoahHeap::heap()->mode()->is_generational()) {
249 ls.print(" (%s)", _space_info->name());
250 }
251 ls.print_raw(": ", 2);
252 va_list va;
253 va_start(va, fmt);
254 ls.vprint(fmt, va);
255 va_end(va);
256 ls.cr();
257 }
258 }
259
260 void ShenandoahHeuristics::record_success_concurrent() {
261 _gc_cycle_time_history->add(elapsed_cycle_time());
262 _gc_times_learned++;
263
264 adjust_penalty(Concurrent_Adjust);
265 }
266
267 void ShenandoahHeuristics::record_success_degenerated() {
268 adjust_penalty(Degenerated_Penalty);
269 }
270
271 void ShenandoahHeuristics::record_success_full() {
272 adjust_penalty(Full_Penalty);
273 }
274
275 void ShenandoahHeuristics::record_allocation_failure_gc() {
276 // Do nothing.
277 }
278
279 void ShenandoahHeuristics::record_requested_gc() {
280 // Assume users call System.gc() when external state changes significantly,
281 // which forces us to re-learn the GC timings and allocation rates.
282 _gc_times_learned = 0;
283 }
284
285 bool ShenandoahHeuristics::can_unload_classes() {
286 return ClassUnloading;
287 }
288
289 bool ShenandoahHeuristics::should_unload_classes() {
290 if (!can_unload_classes()) return false;
291 if (has_metaspace_oom()) return true;
292 return ClassUnloadingWithConcurrentMark;
293 }
294
295 void ShenandoahHeuristics::initialize() {
296 // Nothing to do by default.
297 }
298
299 double ShenandoahHeuristics::elapsed_cycle_time() const {
300 return os::elapsedTime() - _cycle_start;
301 }