1 /*
2 * Copyright (c) 2018, 2021, 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/shenandoahAllocRequest.hpp"
28 #include "gc/shenandoah/shenandoahCollectionSet.inline.hpp"
29 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
30 #include "gc/shenandoah/shenandoahGeneration.hpp"
31 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
32 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
33 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
34 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
35 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
36 #include "gc/shenandoah/heuristics/shenandoahHeuristics.hpp"
37 #include "gc/shenandoah/mode/shenandoahMode.hpp"
38 #include "logging/log.hpp"
39 #include "logging/logTag.hpp"
40 #include "runtime/globals_extension.hpp"
41
42 int ShenandoahHeuristics::compare_by_garbage(RegionData a, RegionData b) {
43 if (a._garbage > b._garbage)
44 return -1;
45 else if (a._garbage < b._garbage)
46 return 1;
47 else return 0;
48 }
49
50 ShenandoahHeuristics::ShenandoahHeuristics(ShenandoahGeneration* generation) :
51 _generation(generation),
52 _region_data(NULL),
53 _degenerated_cycles_in_a_row(0),
54 _successful_cycles_in_a_row(0),
55 _guaranteed_gc_interval(0),
56 _cycle_start(os::elapsedTime()),
57 _last_cycle_end(0),
58 _gc_times_learned(0),
59 _gc_time_penalties(0),
60 _gc_time_history(new TruncatedSeq(10, ShenandoahAdaptiveDecayFactor)),
61 _live_memory_last_cycle(0),
62 _live_memory_penultimate_cycle(0),
63 _metaspace_oom()
64 {
65 // No unloading during concurrent mark? Communicate that to heuristics
66 if (!ClassUnloadingWithConcurrentMark) {
67 FLAG_SET_DEFAULT(ShenandoahUnloadClassesFrequency, 0);
68 }
69
70 size_t num_regions = ShenandoahHeap::heap()->num_regions();
71 assert(num_regions > 0, "Sanity");
72
73 _region_data = NEW_C_HEAP_ARRAY(RegionData, num_regions, mtGC);
74 }
75
76 ShenandoahHeuristics::~ShenandoahHeuristics() {
77 FREE_C_HEAP_ARRAY(RegionGarbage, _region_data);
78 }
79
80 size_t ShenandoahHeuristics::select_aged_regions(size_t old_available, size_t num_regions, bool preselected_regions[]) {
81 ShenandoahHeap* heap = ShenandoahHeap::heap();
82 size_t old_consumed = 0;
83 if (heap->mode()->is_generational()) {
84 for (size_t i = 0; i < num_regions; i++) {
85 ShenandoahHeapRegion* region = heap->get_region(i);
86 if (in_generation(region) && !region->is_empty() && region->is_regular() && (region->age() >= InitialTenuringThreshold)) {
87 size_t promotion_need = (size_t) (region->get_live_data_bytes() * ShenandoahEvacWaste);
88 if (old_consumed + promotion_need < old_available) {
89 old_consumed += promotion_need;
90 preselected_regions[i] = true;
91 }
92 // Note that we keep going even if one region is excluded from selection. Subsequent regions may be selected
93 // if they have smaller live data.
94 }
95 }
96 }
97 return old_consumed;
98 }
99
100 void ShenandoahHeuristics::choose_collection_set(ShenandoahCollectionSet* collection_set, ShenandoahOldHeuristics* old_heuristics) {
101 ShenandoahHeap* heap = ShenandoahHeap::heap();
102 bool is_generational = heap->mode()->is_generational();
103
104 assert(collection_set->count() == 0, "Must be empty");
105 assert(_generation->generation_mode() != OLD, "Old GC invokes ShenandoahOldHeuristics::choose_collection_set()");
106
107 // Check all pinned regions have updated status before choosing the collection set.
108 heap->assert_pinned_region_status();
109
110 // Step 1. Build up the region candidates we care about, rejecting losers and accepting winners right away.
111
112 size_t num_regions = heap->num_regions();
113
114 RegionData* candidates = _region_data;
115
116 size_t cand_idx = 0;
117
118 size_t total_garbage = 0;
119
120 size_t immediate_garbage = 0;
121 size_t immediate_regions = 0;
122
123 size_t free = 0;
124 size_t free_regions = 0;
125 size_t live_memory = 0;
126
127 for (size_t i = 0; i < num_regions; i++) {
128 ShenandoahHeapRegion* region = heap->get_region(i);
129 if (!in_generation(region)) {
130 continue;
131 }
132
133 size_t garbage = region->garbage();
134 total_garbage += garbage;
135 if (region->is_empty()) {
136 free_regions++;
137 free += ShenandoahHeapRegion::region_size_bytes();
138 } else if (region->is_regular()) {
139 if (!region->has_live()) {
140 // We can recycle it right away and put it in the free set.
141 immediate_regions++;
142 immediate_garbage += garbage;
143 region->make_trash_immediate();
144 } else {
145 assert (_generation->generation_mode() != OLD, "OLD is handled elsewhere");
146 live_memory += region->get_live_data_bytes();
147 // This is our candidate for later consideration.
148 candidates[cand_idx]._region = region;
149 if (is_generational && collection_set->is_preselected(i)) {
150 // If region is preselected, we know mode()->is_generational() and region->age() >= InitialTenuringThreshold)
151 garbage = ShenandoahHeapRegion::region_size_bytes();
152 }
153 candidates[cand_idx]._garbage = garbage;
154 cand_idx++;
155 }
156 } else if (region->is_humongous_start()) {
157
158 // Reclaim humongous regions here, and count them as the immediate garbage
159 #ifdef ASSERT
160 bool reg_live = region->has_live();
161 bool bm_live = heap->complete_marking_context()->is_marked(cast_to_oop(region->bottom()));
162 assert(reg_live == bm_live,
163 "Humongous liveness and marks should agree. Region live: %s; Bitmap live: %s; Region Live Words: " SIZE_FORMAT,
164 BOOL_TO_STR(reg_live), BOOL_TO_STR(bm_live), region->get_live_data_words());
165 #endif
166 if (!region->has_live()) {
167 heap->trash_humongous_region_at(region);
168
169 // Count only the start. Continuations would be counted on "trash" path
170 immediate_regions++;
171 immediate_garbage += garbage;
172 } else {
173 live_memory += region->get_live_data_bytes();
174 }
175 } else if (region->is_trash()) {
176 // Count in just trashed collection set, during coalesced CM-with-UR
177 immediate_regions++;
178 immediate_garbage += garbage;
179 } else { // region->is_humongous_cont() and !region->is_trash()
180 live_memory += region->get_live_data_bytes();
181 }
182 }
183
184 save_last_live_memory(live_memory);
185
186 // Step 2. Look back at garbage statistics, and decide if we want to collect anything,
187 // given the amount of immediately reclaimable garbage. If we do, figure out the collection set.
188
189 assert (immediate_garbage <= total_garbage,
190 "Cannot have more immediate garbage than total garbage: " SIZE_FORMAT "%s vs " SIZE_FORMAT "%s",
191 byte_size_in_proper_unit(immediate_garbage), proper_unit_for_byte_size(immediate_garbage),
192 byte_size_in_proper_unit(total_garbage), proper_unit_for_byte_size(total_garbage));
193
194 size_t immediate_percent = (total_garbage == 0) ? 0 : (immediate_garbage * 100 / total_garbage);
195 collection_set->set_immediate_trash(immediate_garbage);
196
197 if (immediate_percent <= ShenandoahImmediateThreshold) {
198 if (old_heuristics != NULL) {
199 old_heuristics->prime_collection_set(collection_set);
200 }
201 // else, this is global collection and doesn't need to prime_collection_set
202
203 // Add young-gen regions into the collection set. This is a virtual call, implemented differently by each
204 // of the heuristics subclasses.
205 choose_collection_set_from_regiondata(collection_set, candidates, cand_idx, immediate_garbage + free);
206 } else {
207 // we're going to skip evacuation and update refs because we reclaimed sufficient amounts of immediate garbage.
208 heap->shenandoah_policy()->record_abbreviated_cycle();
209 }
210
211 if (collection_set->has_old_regions()) {
212 heap->shenandoah_policy()->record_mixed_cycle();
213 }
214
215 size_t cset_percent = (total_garbage == 0) ? 0 : (collection_set->garbage() * 100 / total_garbage);
216 size_t collectable_garbage = collection_set->garbage() + immediate_garbage;
217 size_t collectable_garbage_percent = (total_garbage == 0) ? 0 : (collectable_garbage * 100 / total_garbage);
218
219 log_info(gc, ergo)("Collectable Garbage: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), "
220 "Immediate: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%), "
221 "CSet: " SIZE_FORMAT "%s (" SIZE_FORMAT "%%)",
222
223 byte_size_in_proper_unit(collectable_garbage),
224 proper_unit_for_byte_size(collectable_garbage),
225 collectable_garbage_percent,
226
227 byte_size_in_proper_unit(immediate_garbage),
228 proper_unit_for_byte_size(immediate_garbage),
229 immediate_percent,
230
231 byte_size_in_proper_unit(collection_set->garbage()),
232 proper_unit_for_byte_size(collection_set->garbage()),
233 cset_percent);
234
235 size_t bytes_evacuated = collection_set->get_bytes_reserved_for_evacuation();
236 log_info(gc, ergo)("Total Evacuation: " SIZE_FORMAT "%s",
237 byte_size_in_proper_unit(bytes_evacuated), proper_unit_for_byte_size(bytes_evacuated));
238 }
239
240 void ShenandoahHeuristics::record_cycle_start() {
241 _cycle_start = os::elapsedTime();
242 }
243
244 void ShenandoahHeuristics::record_cycle_end() {
245 _last_cycle_end = os::elapsedTime();
246 }
247
248 bool ShenandoahHeuristics::should_start_gc() {
249 // Perform GC to cleanup metaspace
250 if (has_metaspace_oom()) {
251 // Some of vmTestbase/metaspace tests depend on following line to count GC cycles
252 log_info(gc)("Trigger: %s", GCCause::to_string(GCCause::_metadata_GC_threshold));
253 return true;
254 }
255
256 if (_guaranteed_gc_interval > 0) {
257 double last_time_ms = (os::elapsedTime() - _last_cycle_end) * 1000;
258 if (last_time_ms > _guaranteed_gc_interval) {
259 log_info(gc)("Trigger (%s): Time since last GC (%.0f ms) is larger than guaranteed interval (" UINTX_FORMAT " ms)",
260 _generation->name(), last_time_ms, _guaranteed_gc_interval);
261 return true;
262 }
263 }
264
265 return false;
266 }
267
268 bool ShenandoahHeuristics::should_degenerate_cycle() {
269 return _degenerated_cycles_in_a_row <= ShenandoahFullGCThreshold;
270 }
271
272 void ShenandoahHeuristics::adjust_penalty(intx step) {
273 assert(0 <= _gc_time_penalties && _gc_time_penalties <= 100,
274 "In range before adjustment: " INTX_FORMAT, _gc_time_penalties);
275
276 intx new_val = _gc_time_penalties + step;
277 if (new_val < 0) {
278 new_val = 0;
279 }
280 if (new_val > 100) {
281 new_val = 100;
282 }
283 _gc_time_penalties = new_val;
284
285 assert(0 <= _gc_time_penalties && _gc_time_penalties <= 100,
286 "In range after adjustment: " INTX_FORMAT, _gc_time_penalties);
287 }
288
289 void ShenandoahHeuristics::record_success_concurrent(bool abbreviated) {
290 _degenerated_cycles_in_a_row = 0;
291 _successful_cycles_in_a_row++;
292
293 if (!(abbreviated && ShenandoahAdaptiveIgnoreShortCycles)) {
294 _gc_time_history->add(time_since_last_gc());
295 _gc_times_learned++;
296 }
297
298 adjust_penalty(Concurrent_Adjust);
299 }
300
301 void ShenandoahHeuristics::record_success_degenerated() {
302 _degenerated_cycles_in_a_row++;
303 _successful_cycles_in_a_row = 0;
304
305 adjust_penalty(Degenerated_Penalty);
306 }
307
308 void ShenandoahHeuristics::record_success_full() {
309 _degenerated_cycles_in_a_row = 0;
310 _successful_cycles_in_a_row++;
311
312 adjust_penalty(Full_Penalty);
313 }
314
315 void ShenandoahHeuristics::record_allocation_failure_gc() {
316 // Do nothing.
317 }
318
319 void ShenandoahHeuristics::record_requested_gc() {
320 // Assume users call System.gc() when external state changes significantly,
321 // which forces us to re-learn the GC timings and allocation rates.
322 _gc_times_learned = 0;
323 }
324
325 bool ShenandoahHeuristics::can_unload_classes() {
326 if (!ClassUnloading) return false;
327 return true;
328 }
329
330 bool ShenandoahHeuristics::can_unload_classes_normal() {
331 if (!can_unload_classes()) return false;
332 if (has_metaspace_oom()) return true;
333 if (!ClassUnloadingWithConcurrentMark) return false;
334 if (ShenandoahUnloadClassesFrequency == 0) return false;
335 return true;
336 }
337
338 bool ShenandoahHeuristics::should_unload_classes() {
339 if (!can_unload_classes_normal()) return false;
340 if (has_metaspace_oom()) return true;
341 size_t cycle = ShenandoahHeap::heap()->shenandoah_policy()->cycle_counter();
342 // Unload classes every Nth GC cycle.
343 // This should not happen in the same cycle as process_references to amortize costs.
344 // Offsetting by one is enough to break the rendezvous when periods are equal.
345 // When periods are not equal, offsetting by one is just as good as any other guess.
346 return (cycle + 1) % ShenandoahUnloadClassesFrequency == 0;
347 }
348
349 void ShenandoahHeuristics::initialize() {
350 // Nothing to do by default.
351 }
352
353 double ShenandoahHeuristics::time_since_last_gc() const {
354 return os::elapsedTime() - _cycle_start;
355 }
356
357 bool ShenandoahHeuristics::in_generation(ShenandoahHeapRegion* region) {
358 return ((_generation->generation_mode() == GLOBAL)
359 || (_generation->generation_mode() == YOUNG && region->affiliation() == YOUNG_GENERATION)
360 || (_generation->generation_mode() == OLD && region->affiliation() == OLD_GENERATION));
361 }
362
363 size_t ShenandoahHeuristics::min_free_threshold() {
364 size_t min_free_threshold =
365 _generation->generation_mode() == GenerationMode::OLD
366 ? ShenandoahOldMinFreeThreshold
367 : ShenandoahMinFreeThreshold;
368 return _generation->soft_max_capacity() / 100 * min_free_threshold;
369 }
370
371 void ShenandoahHeuristics::save_last_live_memory(size_t live_memory) {
372 _live_memory_penultimate_cycle = _live_memory_last_cycle;
373 _live_memory_last_cycle = live_memory;
374 }
375
376 size_t ShenandoahHeuristics::get_last_live_memory() {
377 return _live_memory_last_cycle;
378 }
379
380 size_t ShenandoahHeuristics::get_penultimate_live_memory() {
381 return _live_memory_penultimate_cycle;
382 }