1 /*
2 * Copyright (c) 2016, Oracle and/or its affiliates. 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.
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23 */
24
25 #ifndef SHARE_VM_GC_G1_G1POLICY_HPP
26 #define SHARE_VM_GC_G1_G1POLICY_HPP
27
28 #include "gc/g1/g1CollectorState.hpp"
29 #include "gc/g1/g1GCPhaseTimes.hpp"
30 #include "gc/g1/g1InCSetState.hpp"
31 #include "gc/g1/g1InitialMarkToMixedTimeTracker.hpp"
32 #include "gc/g1/g1MMUTracker.hpp"
33 #include "gc/g1/g1Predictions.hpp"
34 #include "gc/g1/g1YoungGenSizer.hpp"
35 #include "gc/shared/gcCause.hpp"
36 #include "utilities/pair.hpp"
37
38 // A G1Policy makes policy decisions that determine the
39 // characteristics of the collector. Examples include:
40 // * choice of collection set.
41 // * when to collect.
42
43 class HeapRegion;
44 class G1CollectionSet;
45 class CollectionSetChooser;
46 class G1IHOPControl;
47 class G1Analytics;
48 class G1YoungGenSizer;
49 class GCPolicyCounters;
50
51 class G1Policy: public CHeapObj<mtGC> {
52 private:
53 G1IHOPControl* _ihop_control;
54
55 G1IHOPControl* create_ihop_control() const;
56 // Update the IHOP control with necessary statistics.
57 void update_ihop_prediction(double mutator_time_s,
58 size_t mutator_alloc_bytes,
59 size_t young_gen_size);
60 void report_ihop_statistics();
61
62 G1Predictions _predictor;
63 G1Analytics* _analytics;
64 G1MMUTracker* _mmu_tracker;
65
66 GCPolicyCounters* _policy_counters;
67
68 double _full_collection_start_sec;
69
70 uint _young_list_target_length;
71 uint _young_list_fixed_length;
72
73 // The max number of regions we can extend the eden by while the GC
74 // locker is active. This should be >= _young_list_target_length;
75 uint _young_list_max_length;
76
77 SurvRateGroup* _short_lived_surv_rate_group;
78 SurvRateGroup* _survivor_surv_rate_group;
79
80 double _reserve_factor;
81 uint _reserve_regions;
82
83 G1YoungGenSizer _young_gen_sizer;
84
85 uint _free_regions_at_end_of_collection;
86
87 size_t _max_rs_lengths;
88
89 size_t _rs_lengths_prediction;
90
91 #ifndef PRODUCT
92 bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group);
93 #endif // PRODUCT
94
95 double _pause_time_target_ms;
96
97 size_t _pending_cards;
98
99 // The amount of allocated bytes in old gen during the last mutator and the following
100 // young GC phase.
101 size_t _bytes_allocated_in_old_since_last_gc;
102
103 G1InitialMarkToMixedTimeTracker _initial_mark_to_mixed;
104 public:
105 const G1Predictions& predictor() const { return _predictor; }
106 const G1Analytics* analytics() const { return const_cast<const G1Analytics*>(_analytics); }
107
108 // Add the given number of bytes to the total number of allocated bytes in the old gen.
109 void add_bytes_allocated_in_old_since_last_gc(size_t bytes) { _bytes_allocated_in_old_since_last_gc += bytes; }
110
111 // Accessors
112
113 void set_region_eden(HeapRegion* hr, int young_index_in_cset) {
114 hr->set_eden();
115 hr->install_surv_rate_group(_short_lived_surv_rate_group);
116 hr->set_young_index_in_cset(young_index_in_cset);
117 }
118
119 void set_region_survivor(HeapRegion* hr, int young_index_in_cset) {
120 assert(hr->is_survivor(), "pre-condition");
121 hr->install_surv_rate_group(_survivor_surv_rate_group);
122 hr->set_young_index_in_cset(young_index_in_cset);
123 }
124
125 #ifndef PRODUCT
126 bool verify_young_ages();
127 #endif // PRODUCT
128
129 void record_max_rs_lengths(size_t rs_lengths) {
130 _max_rs_lengths = rs_lengths;
131 }
132
133
134 double predict_base_elapsed_time_ms(size_t pending_cards) const;
135 double predict_base_elapsed_time_ms(size_t pending_cards,
136 size_t scanned_cards) const;
137 size_t predict_bytes_to_copy(HeapRegion* hr) const;
138 double predict_region_elapsed_time_ms(HeapRegion* hr, bool for_young_gc) const;
139
140 double predict_survivor_regions_evac_time() const;
141
142 bool should_update_surv_rate_group_predictors() {
143 return collector_state()->last_gc_was_young() && !collector_state()->in_marking_window();
144 }
145
146 void cset_regions_freed() {
147 bool update = should_update_surv_rate_group_predictors();
148
149 _short_lived_surv_rate_group->all_surviving_words_recorded(update);
150 _survivor_surv_rate_group->all_surviving_words_recorded(update);
151 }
152
153 G1MMUTracker* mmu_tracker() {
154 return _mmu_tracker;
155 }
156
157 const G1MMUTracker* mmu_tracker() const {
158 return _mmu_tracker;
159 }
160
161 double max_pause_time_ms() const {
162 return _mmu_tracker->max_gc_time() * 1000.0;
163 }
164
165 // Returns an estimate of the survival rate of the region at yg-age
166 // "yg_age".
167 double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const;
168
169 double predict_yg_surv_rate(int age) const;
170
171 double accum_yg_surv_rate_pred(int age) const;
172
173 protected:
174 G1CollectionSet* _collection_set;
175 virtual double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const;
176 virtual double other_time_ms(double pause_time_ms) const;
177
178 double young_other_time_ms() const;
179 double non_young_other_time_ms() const;
180 double constant_other_time_ms(double pause_time_ms) const;
181
182 CollectionSetChooser* cset_chooser() const;
183 private:
184
185 // The number of bytes copied during the GC.
186 size_t _bytes_copied_during_gc;
187
188 // Stash a pointer to the g1 heap.
189 G1CollectedHeap* _g1;
190
191 G1GCPhaseTimes* _phase_times;
192
193 // This set of variables tracks the collector efficiency, in order to
194 // determine whether we should initiate a new marking.
195 double _mark_remark_start_sec;
196 double _mark_cleanup_start_sec;
197
198 // Updates the internal young list maximum and target lengths. Returns the
199 // unbounded young list target length.
200 uint update_young_list_max_and_target_length();
201 uint update_young_list_max_and_target_length(size_t rs_lengths);
202
203 // Update the young list target length either by setting it to the
204 // desired fixed value or by calculating it using G1's pause
205 // prediction model. If no rs_lengths parameter is passed, predict
206 // the RS lengths using the prediction model, otherwise use the
207 // given rs_lengths as the prediction.
208 // Returns the unbounded young list target length.
209 uint update_young_list_target_length(size_t rs_lengths);
210
211 // Calculate and return the minimum desired young list target
212 // length. This is the minimum desired young list length according
213 // to the user's inputs.
214 uint calculate_young_list_desired_min_length(uint base_min_length) const;
215
216 // Calculate and return the maximum desired young list target
217 // length. This is the maximum desired young list length according
218 // to the user's inputs.
219 uint calculate_young_list_desired_max_length() const;
220
221 // Calculate and return the maximum young list target length that
222 // can fit into the pause time goal. The parameters are: rs_lengths
223 // represent the prediction of how large the young RSet lengths will
224 // be, base_min_length is the already existing number of regions in
225 // the young list, min_length and max_length are the desired min and
226 // max young list length according to the user's inputs.
227 uint calculate_young_list_target_length(size_t rs_lengths,
228 uint base_min_length,
229 uint desired_min_length,
230 uint desired_max_length) const;
231
232 // Result of the bounded_young_list_target_length() method, containing both the
233 // bounded as well as the unbounded young list target lengths in this order.
234 typedef Pair<uint, uint, StackObj> YoungTargetLengths;
235 YoungTargetLengths young_list_target_lengths(size_t rs_lengths) const;
236
237 void update_rs_lengths_prediction();
238 void update_rs_lengths_prediction(size_t prediction);
239
240 // Check whether a given young length (young_length) fits into the
241 // given target pause time and whether the prediction for the amount
242 // of objects to be copied for the given length will fit into the
243 // given free space (expressed by base_free_regions). It is used by
244 // calculate_young_list_target_length().
245 bool predict_will_fit(uint young_length, double base_time_ms,
246 uint base_free_regions, double target_pause_time_ms) const;
247
248 public:
249 size_t pending_cards() const { return _pending_cards; }
250
251 // Calculate the minimum number of old regions we'll add to the CSet
252 // during a mixed GC.
253 uint calc_min_old_cset_length() const;
254
255 // Calculate the maximum number of old regions we'll add to the CSet
256 // during a mixed GC.
257 uint calc_max_old_cset_length() const;
258
259 // Returns the given amount of uncollected reclaimable space
260 // as a percentage of the current heap capacity.
261 double reclaimable_bytes_perc(size_t reclaimable_bytes) const;
262
263 private:
264 // Sets up marking if proper conditions are met.
265 void maybe_start_marking();
266
267 // The kind of STW pause.
268 enum PauseKind {
269 FullGC,
270 YoungOnlyGC,
271 MixedGC,
272 LastYoungGC,
273 InitialMarkGC,
274 Cleanup,
275 Remark
276 };
277
278 // Calculate PauseKind from internal state.
279 PauseKind young_gc_pause_kind() const;
280 // Record the given STW pause with the given start and end times (in s).
281 void record_pause(PauseKind kind, double start, double end);
282 // Indicate that we aborted marking before doing any mixed GCs.
283 void abort_time_to_mixed_tracking();
284 public:
285
286 G1Policy();
287
288 virtual ~G1Policy();
289
290 G1CollectorState* collector_state() const;
291
292 G1GCPhaseTimes* phase_times() const { return _phase_times; }
293
294 // Check the current value of the young list RSet lengths and
295 // compare it against the last prediction. If the current value is
296 // higher, recalculate the young list target length prediction.
297 void revise_young_list_target_length_if_necessary(size_t rs_lengths);
298
299 // This should be called after the heap is resized.
300 void record_new_heap_size(uint new_number_of_regions);
301
302 void init();
303
304 virtual void note_gc_start();
305
306 bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
307
308 bool about_to_start_mixed_phase() const;
309
310 // Record the start and end of an evacuation pause.
311 void record_collection_pause_start(double start_time_sec);
312 void record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc);
313
314 // Record the start and end of a full collection.
315 void record_full_collection_start();
316 void record_full_collection_end();
317
318 // Must currently be called while the world is stopped.
319 void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
320
321 // Record start and end of remark.
322 void record_concurrent_mark_remark_start();
323 void record_concurrent_mark_remark_end();
324
325 // Record start, end, and completion of cleanup.
326 void record_concurrent_mark_cleanup_start();
327 void record_concurrent_mark_cleanup_end();
328 void record_concurrent_mark_cleanup_completed();
329
330 virtual void print_phases();
331
332 // Record how much space we copied during a GC. This is typically
333 // called when a GC alloc region is being retired.
334 void record_bytes_copied_during_gc(size_t bytes) {
335 _bytes_copied_during_gc += bytes;
336 }
337
338 // The amount of space we copied during a GC.
339 size_t bytes_copied_during_gc() const {
340 return _bytes_copied_during_gc;
341 }
342
343 // Determine whether there are candidate regions so that the
344 // next GC should be mixed. The two action strings are used
345 // in the ergo output when the method returns true or false.
346 bool next_gc_should_be_mixed(const char* true_action_str,
347 const char* false_action_str) const;
348
349 virtual void finalize_collection_set(double target_pause_time_ms);
350 private:
351 // Set the state to start a concurrent marking cycle and clear
352 // _initiate_conc_mark_if_possible because it has now been
353 // acted on.
354 void initiate_conc_mark();
355
356 public:
357 // This sets the initiate_conc_mark_if_possible() flag to start a
358 // new cycle, as long as we are not already in one. It's best if it
359 // is called during a safepoint when the test whether a cycle is in
360 // progress or not is stable.
361 bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
362
363 // This is called at the very beginning of an evacuation pause (it
364 // has to be the first thing that the pause does). If
365 // initiate_conc_mark_if_possible() is true, and the concurrent
366 // marking thread has completed its work during the previous cycle,
367 // it will set during_initial_mark_pause() to so that the pause does
368 // the initial-mark work and start a marking cycle.
369 void decide_on_conc_mark_initiation();
370
371 // Print stats on young survival ratio
372 void print_yg_surv_rate_info() const;
373
374 void finished_recalculating_age_indexes(bool is_survivors) {
375 if (is_survivors) {
376 _survivor_surv_rate_group->finished_recalculating_age_indexes();
377 } else {
378 _short_lived_surv_rate_group->finished_recalculating_age_indexes();
379 }
380 }
381
382 size_t young_list_target_length() const { return _young_list_target_length; }
383
384 bool is_young_list_full() const;
385
386 bool can_expand_young_list() const;
387
388 uint young_list_max_length() const {
389 return _young_list_max_length;
390 }
391
392 bool adaptive_young_list_length() const;
393
394 virtual bool should_process_references() const {
395 return true;
396 }
397
398 private:
399 //
400 // Survivor regions policy.
401 //
402
403 // Current tenuring threshold, set to 0 if the collector reaches the
404 // maximum amount of survivors regions.
405 uint _tenuring_threshold;
406
407 // The limit on the number of regions allocated for survivors.
408 uint _max_survivor_regions;
409
410 AgeTable _survivors_age_table;
411
412 public:
413 uint tenuring_threshold() const { return _tenuring_threshold; }
414
415 uint max_survivor_regions() {
416 return _max_survivor_regions;
417 }
418
419 void note_start_adding_survivor_regions() {
420 _survivor_surv_rate_group->start_adding_regions();
421 }
422
423 void note_stop_adding_survivor_regions() {
424 _survivor_surv_rate_group->stop_adding_regions();
425 }
426
427 void record_age_table(AgeTable* age_table) {
428 _survivors_age_table.merge(age_table);
429 }
430
431 void update_max_gc_locker_expansion();
432
433 // Calculates survivor space parameters.
434 void update_survivors_policy();
435 };
436
437 #endif // SHARE_VM_GC_G1_G1POLICY_HPP