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 double _pause_time_target_ms;
95
96 size_t _pending_cards;
97
98 // The amount of allocated bytes in old gen during the last mutator and the following
99 // young GC phase.
100 size_t _bytes_allocated_in_old_since_last_gc;
101
102 G1InitialMarkToMixedTimeTracker _initial_mark_to_mixed;
103 public:
104 const G1Predictions& predictor() const { return _predictor; }
105 const G1Analytics* analytics() const { return const_cast<const G1Analytics*>(_analytics); }
106
107 // Add the given number of bytes to the total number of allocated bytes in the old gen.
108 void add_bytes_allocated_in_old_since_last_gc(size_t bytes) { _bytes_allocated_in_old_since_last_gc += bytes; }
109
110 // Accessors
111
112 void set_region_eden(HeapRegion* hr, int young_index_in_cset) {
113 hr->set_eden();
114 hr->install_surv_rate_group(_short_lived_surv_rate_group);
115 hr->set_young_index_in_cset(young_index_in_cset);
116 }
117
118 void set_region_survivor(HeapRegion* hr, int young_index_in_cset) {
119 assert(hr->is_survivor(), "pre-condition");
120 hr->install_surv_rate_group(_survivor_surv_rate_group);
121 hr->set_young_index_in_cset(young_index_in_cset);
122 }
123
124 #ifndef PRODUCT
125 bool verify_young_ages();
126 #endif // PRODUCT
127
128 void record_max_rs_lengths(size_t rs_lengths) {
129 _max_rs_lengths = rs_lengths;
130 }
131
132
133 double predict_base_elapsed_time_ms(size_t pending_cards) const;
134 double predict_base_elapsed_time_ms(size_t pending_cards,
135 size_t scanned_cards) const;
136 size_t predict_bytes_to_copy(HeapRegion* hr) const;
137 double predict_region_elapsed_time_ms(HeapRegion* hr, bool for_young_gc) const;
138
139 double predict_survivor_regions_evac_time() const;
140
141 bool should_update_surv_rate_group_predictors() {
142 return collector_state()->last_gc_was_young() && !collector_state()->in_marking_window();
143 }
144
145 void cset_regions_freed() {
146 bool update = should_update_surv_rate_group_predictors();
147
148 _short_lived_surv_rate_group->all_surviving_words_recorded(update);
149 _survivor_surv_rate_group->all_surviving_words_recorded(update);
150 }
151
152 G1MMUTracker* mmu_tracker() {
153 return _mmu_tracker;
154 }
155
156 const G1MMUTracker* mmu_tracker() const {
157 return _mmu_tracker;
158 }
159
160 double max_pause_time_ms() const {
161 return _mmu_tracker->max_gc_time() * 1000.0;
162 }
163
164 // Returns an estimate of the survival rate of the region at yg-age
165 // "yg_age".
166 double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const;
167
168 double predict_yg_surv_rate(int age) const;
169
170 double accum_yg_surv_rate_pred(int age) const;
171
172 // When copying, we will likely need more bytes free than is live in the region.
173 // Add some safety margin to factor in the confidence of our guess, and the
174 // natural expected waste.
175 // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
176 // of the calculation: the lower the confidence, the more headroom.
177 // (100 + TargetPLABWastePct) represents the increase in expected bytes during
178 // copying due to anticipated waste in the PLABs.
179 double safety_factor() const {
180 return (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
181 }
182
183 // Returns an estimate of the available bytes at end of collection, adjusted by
184 // the safety factor.
185 size_t available_bytes_estimate();
186
187 protected:
188 G1CollectionSet* _collection_set;
189 virtual double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const;
190 virtual double other_time_ms(double pause_time_ms) const;
191
192 double young_other_time_ms() const;
193 double non_young_other_time_ms() const;
194 double constant_other_time_ms(double pause_time_ms) const;
195
196 CollectionSetChooser* cset_chooser() const;
197 private:
198
199 // The number of bytes copied during the GC.
200 size_t _bytes_copied_during_gc;
201
202 // Stash a pointer to the g1 heap.
203 G1CollectedHeap* _g1;
204
205 G1GCPhaseTimes* _phase_times;
206
207 // This set of variables tracks the collector efficiency, in order to
208 // determine whether we should initiate a new marking.
209 double _mark_remark_start_sec;
210 double _mark_cleanup_start_sec;
211
212 // Updates the internal young list maximum and target lengths. Returns the
213 // unbounded young list target length.
214 uint update_young_list_max_and_target_length();
215 uint update_young_list_max_and_target_length(size_t rs_lengths);
216
217 // Update the young list target length either by setting it to the
218 // desired fixed value or by calculating it using G1's pause
219 // prediction model. If no rs_lengths parameter is passed, predict
220 // the RS lengths using the prediction model, otherwise use the
221 // given rs_lengths as the prediction.
222 // Returns the unbounded young list target length.
223 uint update_young_list_target_length(size_t rs_lengths);
224
225 // Calculate and return the minimum desired young list target
226 // length. This is the minimum desired young list length according
227 // to the user's inputs.
228 uint calculate_young_list_desired_min_length(uint base_min_length) const;
229
230 // Calculate and return the maximum desired young list target
231 // length. This is the maximum desired young list length according
232 // to the user's inputs.
233 uint calculate_young_list_desired_max_length() const;
234
235 // Calculate and return the maximum young list target length that
236 // can fit into the pause time goal. The parameters are: rs_lengths
237 // represent the prediction of how large the young RSet lengths will
238 // be, base_min_length is the already existing number of regions in
239 // the young list, min_length and max_length are the desired min and
240 // max young list length according to the user's inputs.
241 uint calculate_young_list_target_length(size_t rs_lengths,
242 uint base_min_length,
243 uint desired_min_length,
244 uint desired_max_length) const;
245
246 // Result of the bounded_young_list_target_length() method, containing both the
247 // bounded as well as the unbounded young list target lengths in this order.
248 typedef Pair<uint, uint, StackObj> YoungTargetLengths;
249 YoungTargetLengths young_list_target_lengths(size_t rs_lengths) const;
250
251 void update_rs_lengths_prediction();
252 void update_rs_lengths_prediction(size_t prediction);
253
254 // Check whether a given young length (young_length) fits into the
255 // given target pause time and whether the prediction for the amount
256 // of objects to be copied for the given length will fit into the
257 // given free space (expressed by base_free_regions). It is used by
258 // calculate_young_list_target_length().
259 bool predict_will_fit(uint young_length, double base_time_ms,
260 uint base_free_regions, double target_pause_time_ms) const;
261
262 public:
263 size_t pending_cards() const { return _pending_cards; }
264
265 // Calculate the minimum number of old regions we'll add to the CSet
266 // during a mixed GC.
267 uint calc_min_old_cset_length() const;
268
269 // Calculate the maximum number of old regions we'll add to the CSet
270 // during a mixed GC.
271 uint calc_max_old_cset_length() const;
272
273 // Returns the given amount of uncollected reclaimable space
274 // as a percentage of the current heap capacity.
275 double reclaimable_bytes_perc(size_t reclaimable_bytes) const;
276
277 private:
278 // Sets up marking if proper conditions are met.
279 void maybe_start_marking();
280
281 // The kind of STW pause.
282 enum PauseKind {
283 FullGC,
284 YoungOnlyGC,
285 MixedGC,
286 LastYoungGC,
287 InitialMarkGC,
288 Cleanup,
289 Remark
290 };
291
292 // Calculate PauseKind from internal state.
293 PauseKind young_gc_pause_kind() const;
294 // Record the given STW pause with the given start and end times (in s).
295 void record_pause(PauseKind kind, double start, double end);
296 // Indicate that we aborted marking before doing any mixed GCs.
297 void abort_time_to_mixed_tracking();
298 public:
299
300 G1CollectorPolicy();
301
302 virtual ~G1CollectorPolicy();
303
304 virtual G1CollectorPolicy* as_g1_policy() { return this; }
305
306 G1CollectorState* collector_state() const;
307
308 G1GCPhaseTimes* phase_times() const { return _phase_times; }
309
310 // Check the current value of the young list RSet lengths and
311 // compare it against the last prediction. If the current value is
312 // higher, recalculate the young list target length prediction.
313 void revise_young_list_target_length_if_necessary(size_t rs_lengths);
314
315 // This should be called after the heap is resized.
316 void record_new_heap_size(uint new_number_of_regions);
317
318 void init();
319
320 virtual void note_gc_start(uint num_active_workers);
321
322 // Create jstat counters for the policy.
323 virtual void initialize_gc_policy_counters();
324
325 bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
326
327 bool about_to_start_mixed_phase() const;
328
329 // Record the start and end of an evacuation pause.
330 void record_collection_pause_start(double start_time_sec);
331 void record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc);
332
333 // Record the start and end of a full collection.
334 void record_full_collection_start();
335 void record_full_collection_end();
336
337 // Must currently be called while the world is stopped.
338 void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
339
340 // Record start and end of remark.
341 void record_concurrent_mark_remark_start();
342 void record_concurrent_mark_remark_end();
343
344 // Record start, end, and completion of cleanup.
345 void record_concurrent_mark_cleanup_start();
346 void record_concurrent_mark_cleanup_end();
347 void record_concurrent_mark_cleanup_completed();
348
349 virtual void print_phases();
350
351 // Record how much space we copied during a GC. This is typically
352 // called when a GC alloc region is being retired.
353 void record_bytes_copied_during_gc(size_t bytes) {
354 _bytes_copied_during_gc += bytes;
355 }
356
357 // The amount of space we copied during a GC.
358 size_t bytes_copied_during_gc() const {
359 return _bytes_copied_during_gc;
360 }
361
362 // Determine whether there are candidate regions so that the
363 // next GC should be mixed. The two action strings are used
364 // in the ergo output when the method returns true or false.
365 bool next_gc_should_be_mixed(const char* true_action_str,
366 const char* false_action_str) const;
367
368 virtual void finalize_collection_set(double target_pause_time_ms);
369 private:
370 // Set the state to start a concurrent marking cycle and clear
371 // _initiate_conc_mark_if_possible because it has now been
372 // acted on.
373 void initiate_conc_mark();
374
375 public:
376 // This sets the initiate_conc_mark_if_possible() flag to start a
377 // new cycle, as long as we are not already in one. It's best if it
378 // is called during a safepoint when the test whether a cycle is in
379 // progress or not is stable.
380 bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
381
382 // This is called at the very beginning of an evacuation pause (it
383 // has to be the first thing that the pause does). If
384 // initiate_conc_mark_if_possible() is true, and the concurrent
385 // marking thread has completed its work during the previous cycle,
386 // it will set during_initial_mark_pause() to so that the pause does
387 // the initial-mark work and start a marking cycle.
388 void decide_on_conc_mark_initiation();
389
390 // Print stats on young survival ratio
391 void print_yg_surv_rate_info() const;
392
393 void finished_recalculating_age_indexes(bool is_survivors) {
394 if (is_survivors) {
395 _survivor_surv_rate_group->finished_recalculating_age_indexes();
396 } else {
397 _short_lived_surv_rate_group->finished_recalculating_age_indexes();
398 }
399 }
400
401 size_t young_list_target_length() const { return _young_list_target_length; }
402
403 bool is_young_list_full() const;
404
405 bool can_expand_young_list() const;
406
407 uint young_list_max_length() const {
408 return _young_list_max_length;
409 }
410
411 bool adaptive_young_list_length() const;
412
413 virtual bool should_process_references() const {
414 return true;
415 }
416
417 private:
418 //
419 // Survivor regions policy.
420 //
421
422 // Current tenuring threshold, set to 0 if the collector reaches the
423 // maximum amount of survivors regions.
424 uint _tenuring_threshold;
425
426 // The limit on the number of regions allocated for survivors.
427 uint _max_survivor_regions;
428
429 AgeTable _survivors_age_table;
430
431 public:
432 uint tenuring_threshold() const { return _tenuring_threshold; }
433
434 uint max_survivor_regions() {
435 return _max_survivor_regions;
436 }
437
438 void note_start_adding_survivor_regions() {
439 _survivor_surv_rate_group->start_adding_regions();
440 }
441
442 void note_stop_adding_survivor_regions() {
443 _survivor_surv_rate_group->stop_adding_regions();
444 }
445
446 void record_age_table(AgeTable* age_table) {
447 _survivors_age_table.merge(age_table);
448 }
449
450 void update_max_gc_locker_expansion();
451
452 // Calculates survivor space parameters.
453 void update_survivors_policy();
454
455 virtual void post_heap_initialize();
456 };
457
458 #endif // SHARE_VM_GC_G1_G1COLLECTORPOLICY_HPP