1 /*
2 * Copyright (c) 2001, 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.
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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
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23 */
24
25 #ifndef SHARE_VM_GC_G1_G1COLLECTORPOLICY_HPP
26 #define SHARE_VM_GC_G1_G1COLLECTORPOLICY_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/shared/collectorPolicy.hpp"
35 #include "utilities/pair.hpp"
36
37 // A G1CollectorPolicy makes policy decisions that determine the
38 // characteristics of the collector. Examples include:
39 // * choice of collection set.
40 // * when to collect.
41
42 class HeapRegion;
43 class G1CollectionSet;
44 class CollectionSetChooser;
45 class G1IHOPControl;
46 class G1Analytics;
47 class G1YoungGenSizer;
48
49 class G1CollectorPolicy: public CollectorPolicy {
50 private:
51 G1IHOPControl* _ihop_control;
52
53 G1IHOPControl* create_ihop_control() const;
54 // Update the IHOP control with necessary statistics.
55 void update_ihop_prediction(double mutator_time_s,
56 size_t mutator_alloc_bytes,
57 size_t young_gen_size);
58 void report_ihop_statistics();
59
60 G1Predictions _predictor;
61 G1Analytics* _analytics;
62 G1MMUTracker* _mmu_tracker;
63
64 void initialize_alignments();
65 void initialize_flags();
66
67 double _full_collection_start_sec;
68
69 uint _young_list_target_length;
70 uint _young_list_fixed_length;
71
72 // The max number of regions we can extend the eden by while the GC
73 // locker is active. This should be >= _young_list_target_length;
74 uint _young_list_max_length;
75
76 SurvRateGroup* _short_lived_surv_rate_group;
77 SurvRateGroup* _survivor_surv_rate_group;
78
79 double _reserve_factor;
80 uint _reserve_regions;
81
82 G1YoungGenSizer* _young_gen_sizer;
83
84 uint _free_regions_at_end_of_collection;
85
86 size_t _max_rs_lengths;
87
88 size_t _rs_lengths_prediction;
89
90 #ifndef PRODUCT
91 bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group);
92 #endif // PRODUCT
93
94 void adjust_concurrent_refinement(double update_rs_time,
95 double update_rs_processed_buffers,
96 double goal_ms);
97
98 double _pause_time_target_ms;
99
100 size_t _pending_cards;
101
102 // The amount of allocated bytes in old gen during the last mutator and the following
103 // young GC phase.
104 size_t _bytes_allocated_in_old_since_last_gc;
105
106 G1InitialMarkToMixedTimeTracker _initial_mark_to_mixed;
107 public:
108 const G1Predictions& predictor() const { return _predictor; }
109 const G1Analytics* analytics() const { return const_cast<const G1Analytics*>(_analytics); }
110
111 // Add the given number of bytes to the total number of allocated bytes in the old gen.
112 void add_bytes_allocated_in_old_since_last_gc(size_t bytes) { _bytes_allocated_in_old_since_last_gc += bytes; }
113
114 // Accessors
115
116 void set_region_eden(HeapRegion* hr, int young_index_in_cset) {
117 hr->set_eden();
118 hr->install_surv_rate_group(_short_lived_surv_rate_group);
119 hr->set_young_index_in_cset(young_index_in_cset);
120 }
121
122 void set_region_survivor(HeapRegion* hr, int young_index_in_cset) {
123 assert(hr->is_survivor(), "pre-condition");
124 hr->install_surv_rate_group(_survivor_surv_rate_group);
125 hr->set_young_index_in_cset(young_index_in_cset);
126 }
127
128 #ifndef PRODUCT
129 bool verify_young_ages();
130 #endif // PRODUCT
131
132 void record_max_rs_lengths(size_t rs_lengths) {
133 _max_rs_lengths = rs_lengths;
134 }
135
136
137 double predict_base_elapsed_time_ms(size_t pending_cards) const;
138 double predict_base_elapsed_time_ms(size_t pending_cards,
139 size_t scanned_cards) const;
140 size_t predict_bytes_to_copy(HeapRegion* hr) const;
141 double predict_region_elapsed_time_ms(HeapRegion* hr, bool for_young_gc) const;
142
143 double predict_survivor_regions_evac_time() const;
144
145 bool should_update_surv_rate_group_predictors() {
146 return collector_state()->last_gc_was_young() && !collector_state()->in_marking_window();
147 }
148
149 void cset_regions_freed() {
150 bool update = should_update_surv_rate_group_predictors();
151
152 _short_lived_surv_rate_group->all_surviving_words_recorded(update);
153 _survivor_surv_rate_group->all_surviving_words_recorded(update);
154 }
155
156 G1MMUTracker* mmu_tracker() {
157 return _mmu_tracker;
158 }
159
160 const G1MMUTracker* mmu_tracker() const {
161 return _mmu_tracker;
162 }
163
164 double max_pause_time_ms() const {
165 return _mmu_tracker->max_gc_time() * 1000.0;
166 }
167
168 // Returns an estimate of the survival rate of the region at yg-age
169 // "yg_age".
170 double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const;
171
172 double predict_yg_surv_rate(int age) const;
173
174 double accum_yg_surv_rate_pred(int age) const;
175
176 protected:
177 G1CollectionSet* _collection_set;
178 virtual double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const;
179 virtual double other_time_ms(double pause_time_ms) const;
180
181 double young_other_time_ms() const;
182 double non_young_other_time_ms() const;
183 double constant_other_time_ms(double pause_time_ms) const;
184
185 CollectionSetChooser* cset_chooser() const;
186 private:
187
188 // The number of bytes copied during the GC.
189 size_t _bytes_copied_during_gc;
190
191 // Stash a pointer to the g1 heap.
192 G1CollectedHeap* _g1;
193
194 G1GCPhaseTimes* _phase_times;
195
196 // This set of variables tracks the collector efficiency, in order to
197 // determine whether we should initiate a new marking.
198 double _mark_remark_start_sec;
199 double _mark_cleanup_start_sec;
200
201 // Updates the internal young list maximum and target lengths. Returns the
202 // unbounded young list target length.
203 uint update_young_list_max_and_target_length();
204 uint update_young_list_max_and_target_length(size_t rs_lengths);
205
206 // Update the young list target length either by setting it to the
207 // desired fixed value or by calculating it using G1's pause
208 // prediction model. If no rs_lengths parameter is passed, predict
209 // the RS lengths using the prediction model, otherwise use the
210 // given rs_lengths as the prediction.
211 // Returns the unbounded young list target length.
212 uint update_young_list_target_length(size_t rs_lengths);
213
214 // Calculate and return the minimum desired young list target
215 // length. This is the minimum desired young list length according
216 // to the user's inputs.
217 uint calculate_young_list_desired_min_length(uint base_min_length) const;
218
219 // Calculate and return the maximum desired young list target
220 // length. This is the maximum desired young list length according
221 // to the user's inputs.
222 uint calculate_young_list_desired_max_length() const;
223
224 // Calculate and return the maximum young list target length that
225 // can fit into the pause time goal. The parameters are: rs_lengths
226 // represent the prediction of how large the young RSet lengths will
227 // be, base_min_length is the already existing number of regions in
228 // the young list, min_length and max_length are the desired min and
229 // max young list length according to the user's inputs.
230 uint calculate_young_list_target_length(size_t rs_lengths,
231 uint base_min_length,
232 uint desired_min_length,
233 uint desired_max_length) const;
234
235 // Result of the bounded_young_list_target_length() method, containing both the
236 // bounded as well as the unbounded young list target lengths in this order.
237 typedef Pair<uint, uint, StackObj> YoungTargetLengths;
238 YoungTargetLengths young_list_target_lengths(size_t rs_lengths) const;
239
240 void update_rs_lengths_prediction();
241 void update_rs_lengths_prediction(size_t prediction);
242
243 // Check whether a given young length (young_length) fits into the
244 // given target pause time and whether the prediction for the amount
245 // of objects to be copied for the given length will fit into the
246 // given free space (expressed by base_free_regions). It is used by
247 // calculate_young_list_target_length().
248 bool predict_will_fit(uint young_length, double base_time_ms,
249 uint base_free_regions, double target_pause_time_ms) const;
250
251 public:
252 size_t pending_cards() const { return _pending_cards; }
253
254 // Calculate the minimum number of old regions we'll add to the CSet
255 // during a mixed GC.
256 uint calc_min_old_cset_length() const;
257
258 // Calculate the maximum number of old regions we'll add to the CSet
259 // during a mixed GC.
260 uint calc_max_old_cset_length() const;
261
262 // Returns the given amount of uncollected reclaimable space
263 // as a percentage of the current heap capacity.
264 double reclaimable_bytes_perc(size_t reclaimable_bytes) const;
265
266 private:
267 // Sets up marking if proper conditions are met.
268 void maybe_start_marking();
269
270 // The kind of STW pause.
271 enum PauseKind {
272 FullGC,
273 YoungOnlyGC,
274 MixedGC,
275 LastYoungGC,
276 InitialMarkGC,
277 Cleanup,
278 Remark
279 };
280
281 // Calculate PauseKind from internal state.
282 PauseKind young_gc_pause_kind() const;
283 // Record the given STW pause with the given start and end times (in s).
284 void record_pause(PauseKind kind, double start, double end);
285 // Indicate that we aborted marking before doing any mixed GCs.
286 void abort_time_to_mixed_tracking();
287 public:
288
289 G1CollectorPolicy();
290
291 virtual ~G1CollectorPolicy();
292
293 virtual G1CollectorPolicy* as_g1_policy() { return this; }
294
295 G1CollectorState* collector_state() const;
296
297 G1GCPhaseTimes* phase_times() const { return _phase_times; }
298
299 // Check the current value of the young list RSet lengths and
300 // compare it against the last prediction. If the current value is
301 // higher, recalculate the young list target length prediction.
302 void revise_young_list_target_length_if_necessary(size_t rs_lengths);
303
304 // This should be called after the heap is resized.
305 void record_new_heap_size(uint new_number_of_regions);
306
307 void init();
308
309 virtual void note_gc_start(uint num_active_workers);
310
311 // Create jstat counters for the policy.
312 virtual void initialize_gc_policy_counters();
313
314 bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
315
316 bool about_to_start_mixed_phase() const;
317
318 // Record the start and end of an evacuation pause.
319 void record_collection_pause_start(double start_time_sec);
320 void record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc);
321
322 // Record the start and end of a full collection.
323 void record_full_collection_start();
324 void record_full_collection_end();
325
326 // Must currently be called while the world is stopped.
327 void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
328
329 // Record start and end of remark.
330 void record_concurrent_mark_remark_start();
331 void record_concurrent_mark_remark_end();
332
333 // Record start, end, and completion of cleanup.
334 void record_concurrent_mark_cleanup_start();
335 void record_concurrent_mark_cleanup_end();
336 void record_concurrent_mark_cleanup_completed();
337
338 virtual void print_phases();
339
340 // Record how much space we copied during a GC. This is typically
341 // called when a GC alloc region is being retired.
342 void record_bytes_copied_during_gc(size_t bytes) {
343 _bytes_copied_during_gc += bytes;
344 }
345
346 // The amount of space we copied during a GC.
347 size_t bytes_copied_during_gc() const {
348 return _bytes_copied_during_gc;
349 }
350
351 // Determine whether there are candidate regions so that the
352 // next GC should be mixed. The two action strings are used
353 // in the ergo output when the method returns true or false.
354 bool next_gc_should_be_mixed(const char* true_action_str,
355 const char* false_action_str) const;
356
357 virtual void finalize_collection_set(double target_pause_time_ms);
358 private:
359 // Set the state to start a concurrent marking cycle and clear
360 // _initiate_conc_mark_if_possible because it has now been
361 // acted on.
362 void initiate_conc_mark();
363
364 public:
365 // This sets the initiate_conc_mark_if_possible() flag to start a
366 // new cycle, as long as we are not already in one. It's best if it
367 // is called during a safepoint when the test whether a cycle is in
368 // progress or not is stable.
369 bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
370
371 // This is called at the very beginning of an evacuation pause (it
372 // has to be the first thing that the pause does). If
373 // initiate_conc_mark_if_possible() is true, and the concurrent
374 // marking thread has completed its work during the previous cycle,
375 // it will set during_initial_mark_pause() to so that the pause does
376 // the initial-mark work and start a marking cycle.
377 void decide_on_conc_mark_initiation();
378
379 // Print stats on young survival ratio
380 void print_yg_surv_rate_info() const;
381
382 void finished_recalculating_age_indexes(bool is_survivors) {
383 if (is_survivors) {
384 _survivor_surv_rate_group->finished_recalculating_age_indexes();
385 } else {
386 _short_lived_surv_rate_group->finished_recalculating_age_indexes();
387 }
388 }
389
390 size_t young_list_target_length() const { return _young_list_target_length; }
391
392 bool is_young_list_full() const;
393
394 bool can_expand_young_list() const;
395
396 uint young_list_max_length() const {
397 return _young_list_max_length;
398 }
399
400 bool adaptive_young_list_length() const;
401
402 virtual bool should_process_references() const {
403 return true;
404 }
405
406 private:
407 //
408 // Survivor regions policy.
409 //
410
411 // Current tenuring threshold, set to 0 if the collector reaches the
412 // maximum amount of survivors regions.
413 uint _tenuring_threshold;
414
415 // The limit on the number of regions allocated for survivors.
416 uint _max_survivor_regions;
417
418 AgeTable _survivors_age_table;
419
420 public:
421 uint tenuring_threshold() const { return _tenuring_threshold; }
422
423 uint max_survivor_regions() {
424 return _max_survivor_regions;
425 }
426
427 static const uint REGIONS_UNLIMITED = (uint) -1;
428
429 uint max_regions(InCSetState dest) const {
430 switch (dest.value()) {
431 case InCSetState::Young:
432 return _max_survivor_regions;
433 case InCSetState::Old:
434 return REGIONS_UNLIMITED;
435 default:
436 assert(false, "Unknown dest state: " CSETSTATE_FORMAT, dest.value());
437 break;
438 }
439 // keep some compilers happy
440 return 0;
441 }
442
443 void note_start_adding_survivor_regions() {
444 _survivor_surv_rate_group->start_adding_regions();
445 }
446
447 void note_stop_adding_survivor_regions() {
448 _survivor_surv_rate_group->stop_adding_regions();
449 }
450
451 void record_age_table(AgeTable* age_table) {
452 _survivors_age_table.merge(age_table);
453 }
454
455 void update_max_gc_locker_expansion();
456
457 // Calculates survivor space parameters.
458 void update_survivors_policy();
459
460 virtual void post_heap_initialize();
461 };
462
463 #endif // SHARE_VM_GC_G1_G1COLLECTORPOLICY_HPP