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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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
63 G1MMUTracker* _mmu_tracker;
64
65 void initialize_alignments();
66 void initialize_flags();
67
68 double _full_collection_start_sec;
69
70 // Ratio check data for determining if heap growth is necessary.
71 uint _ratio_over_threshold_count;
72 double _ratio_over_threshold_sum;
73 uint _pauses_since_start;
74
75 uint _young_list_target_length;
76 uint _young_list_fixed_length;
77
78 // The max number of regions we can extend the eden by while the GC
79 // locker is active. This should be >= _young_list_target_length;
80 uint _young_list_max_length;
81
82 SurvRateGroup* _short_lived_surv_rate_group;
83 SurvRateGroup* _survivor_surv_rate_group;
84
85 double _gc_overhead_perc;
86
87 double _reserve_factor;
88 uint _reserve_regions;
89
90 enum PredictionConstants {
91 NumPrevPausesForHeuristics = 10,
92 // MinOverThresholdForGrowth must be less than NumPrevPausesForHeuristics,
93 // representing the minimum number of pause time ratios that exceed
94 // GCTimeRatio before a heap expansion will be triggered.
95 MinOverThresholdForGrowth = 4
96 };
97 G1YoungGenSizer* _young_gen_sizer;
98
99 uint _free_regions_at_end_of_collection;
100
101 size_t _max_rs_lengths;
102
103 size_t _rs_lengths_prediction;
104
105 #ifndef PRODUCT
106 bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group);
107 #endif // PRODUCT
108
109 void adjust_concurrent_refinement(double update_rs_time,
110 double update_rs_processed_buffers,
111 double goal_ms);
112
113 double _pause_time_target_ms;
114
115 size_t _pending_cards;
116
117 // The amount of allocated bytes in old gen during the last mutator and the following
118 // young GC phase.
119 size_t _bytes_allocated_in_old_since_last_gc;
120
121 G1InitialMarkToMixedTimeTracker _initial_mark_to_mixed;
122 public:
123 const G1Predictions& predictor() const { return _predictor; }
124 const G1Analytics* analytics() const { return const_cast<const G1Analytics*>(_analytics); }
125
126 // Add the given number of bytes to the total number of allocated bytes in the old gen.
127 void add_bytes_allocated_in_old_since_last_gc(size_t bytes) { _bytes_allocated_in_old_since_last_gc += bytes; }
128
129 // Accessors
130
131 void set_region_eden(HeapRegion* hr, int young_index_in_cset) {
132 hr->set_eden();
133 hr->install_surv_rate_group(_short_lived_surv_rate_group);
134 hr->set_young_index_in_cset(young_index_in_cset);
135 }
136
137 void set_region_survivor(HeapRegion* hr, int young_index_in_cset) {
138 assert(hr->is_survivor(), "pre-condition");
139 hr->install_surv_rate_group(_survivor_surv_rate_group);
140 hr->set_young_index_in_cset(young_index_in_cset);
141 }
142
143 #ifndef PRODUCT
144 bool verify_young_ages();
145 #endif // PRODUCT
146
147 void record_max_rs_lengths(size_t rs_lengths) {
148 _max_rs_lengths = rs_lengths;
149 }
150
151
152 double predict_base_elapsed_time_ms(size_t pending_cards) const;
153 double predict_base_elapsed_time_ms(size_t pending_cards,
154 size_t scanned_cards) const;
155 size_t predict_bytes_to_copy(HeapRegion* hr) const;
156 double predict_region_elapsed_time_ms(HeapRegion* hr, bool for_young_gc) const;
157
158 double predict_survivor_regions_evac_time() const;
159
160 bool should_update_surv_rate_group_predictors() {
161 return collector_state()->last_gc_was_young() && !collector_state()->in_marking_window();
162 }
163
164 void cset_regions_freed() {
165 bool update = should_update_surv_rate_group_predictors();
166
167 _short_lived_surv_rate_group->all_surviving_words_recorded(update);
168 _survivor_surv_rate_group->all_surviving_words_recorded(update);
169 }
170
171 G1MMUTracker* mmu_tracker() {
172 return _mmu_tracker;
173 }
174
175 const G1MMUTracker* mmu_tracker() const {
176 return _mmu_tracker;
177 }
178
179 double max_pause_time_ms() const {
180 return _mmu_tracker->max_gc_time() * 1000.0;
181 }
182
183 // Returns an estimate of the survival rate of the region at yg-age
184 // "yg_age".
185 double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const;
186
187 double predict_yg_surv_rate(int age) const;
188
189 double accum_yg_surv_rate_pred(int age) const;
190
191 protected:
192 G1CollectionSet* _collection_set;
193 virtual double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const;
194 virtual double other_time_ms(double pause_time_ms) const;
195
196 double young_other_time_ms() const;
197 double non_young_other_time_ms() const;
198 double constant_other_time_ms(double pause_time_ms) const;
199
200 CollectionSetChooser* cset_chooser() const;
201 private:
202
203 // The number of bytes copied during the GC.
204 size_t _bytes_copied_during_gc;
205
206 // Stash a pointer to the g1 heap.
207 G1CollectedHeap* _g1;
208
209 G1GCPhaseTimes* _phase_times;
210
211 // This set of variables tracks the collector efficiency, in order to
212 // determine whether we should initiate a new marking.
213 double _mark_remark_start_sec;
214 double _mark_cleanup_start_sec;
215
216 // Updates the internal young list maximum and target lengths. Returns the
217 // unbounded young list target length.
218 uint update_young_list_max_and_target_length();
219 uint update_young_list_max_and_target_length(size_t rs_lengths);
220
221 // Update the young list target length either by setting it to the
222 // desired fixed value or by calculating it using G1's pause
223 // prediction model. If no rs_lengths parameter is passed, predict
224 // the RS lengths using the prediction model, otherwise use the
225 // given rs_lengths as the prediction.
226 // Returns the unbounded young list target length.
227 uint update_young_list_target_length(size_t rs_lengths);
228
229 // Calculate and return the minimum desired young list target
230 // length. This is the minimum desired young list length according
231 // to the user's inputs.
232 uint calculate_young_list_desired_min_length(uint base_min_length) const;
233
234 // Calculate and return the maximum desired young list target
235 // length. This is the maximum desired young list length according
236 // to the user's inputs.
237 uint calculate_young_list_desired_max_length() const;
238
239 // Calculate and return the maximum young list target length that
240 // can fit into the pause time goal. The parameters are: rs_lengths
241 // represent the prediction of how large the young RSet lengths will
242 // be, base_min_length is the already existing number of regions in
243 // the young list, min_length and max_length are the desired min and
244 // max young list length according to the user's inputs.
245 uint calculate_young_list_target_length(size_t rs_lengths,
246 uint base_min_length,
247 uint desired_min_length,
248 uint desired_max_length) const;
249
250 // Result of the bounded_young_list_target_length() method, containing both the
251 // bounded as well as the unbounded young list target lengths in this order.
252 typedef Pair<uint, uint, StackObj> YoungTargetLengths;
253 YoungTargetLengths young_list_target_lengths(size_t rs_lengths) const;
254
255 void update_rs_lengths_prediction();
256 void update_rs_lengths_prediction(size_t prediction);
257
258 // Calculate and return chunk size (in number of regions) for parallel
259 // concurrent mark cleanup.
260 uint calculate_parallel_work_chunk_size(uint n_workers, uint n_regions) const;
261
262 // Check whether a given young length (young_length) fits into the
263 // given target pause time and whether the prediction for the amount
264 // of objects to be copied for the given length will fit into the
265 // given free space (expressed by base_free_regions). It is used by
266 // calculate_young_list_target_length().
267 bool predict_will_fit(uint young_length, double base_time_ms,
268 uint base_free_regions, double target_pause_time_ms) const;
269
270 public:
271 size_t pending_cards() const { return _pending_cards; }
272
273 // Calculate the minimum number of old regions we'll add to the CSet
274 // during a mixed GC.
275 uint calc_min_old_cset_length() const;
276
277 // Calculate the maximum number of old regions we'll add to the CSet
278 // during a mixed GC.
279 uint calc_max_old_cset_length() const;
280
281 // Returns the given amount of uncollected reclaimable space
282 // as a percentage of the current heap capacity.
283 double reclaimable_bytes_perc(size_t reclaimable_bytes) const;
284
285 private:
286 // Sets up marking if proper conditions are met.
287 void maybe_start_marking();
288
289 // The kind of STW pause.
290 enum PauseKind {
291 FullGC,
292 YoungOnlyGC,
293 MixedGC,
294 LastYoungGC,
295 InitialMarkGC,
296 Cleanup,
297 Remark
298 };
299
300 // Calculate PauseKind from internal state.
301 PauseKind young_gc_pause_kind() const;
302 // Record the given STW pause with the given start and end times (in s).
303 void record_pause(PauseKind kind, double start, double end);
304 // Indicate that we aborted marking before doing any mixed GCs.
305 void abort_time_to_mixed_tracking();
306 public:
307
308 G1CollectorPolicy();
309
310 virtual ~G1CollectorPolicy();
311
312 virtual G1CollectorPolicy* as_g1_policy() { return this; }
313
314 G1CollectorState* collector_state() const;
315
316 G1GCPhaseTimes* phase_times() const { return _phase_times; }
317
318 // Check the current value of the young list RSet lengths and
319 // compare it against the last prediction. If the current value is
320 // higher, recalculate the young list target length prediction.
321 void revise_young_list_target_length_if_necessary(size_t rs_lengths);
322
323 // This should be called after the heap is resized.
324 void record_new_heap_size(uint new_number_of_regions);
325
326 void init();
327
328 virtual void note_gc_start(uint num_active_workers);
329
330 // Create jstat counters for the policy.
331 virtual void initialize_gc_policy_counters();
332
333 bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
334
335 bool about_to_start_mixed_phase() const;
336
337 // Record the start and end of an evacuation pause.
338 void record_collection_pause_start(double start_time_sec);
339 void record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc);
340
341 // Record the start and end of a full collection.
342 void record_full_collection_start();
343 void record_full_collection_end();
344
345 // Must currently be called while the world is stopped.
346 void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
347
348 // Record start and end of remark.
349 void record_concurrent_mark_remark_start();
350 void record_concurrent_mark_remark_end();
351
352 // Record start, end, and completion of cleanup.
353 void record_concurrent_mark_cleanup_start();
354 void record_concurrent_mark_cleanup_end();
355 void record_concurrent_mark_cleanup_completed();
356
357 virtual void print_phases();
358
359 // Record how much space we copied during a GC. This is typically
360 // called when a GC alloc region is being retired.
361 void record_bytes_copied_during_gc(size_t bytes) {
362 _bytes_copied_during_gc += bytes;
363 }
364
365 // The amount of space we copied during a GC.
366 size_t bytes_copied_during_gc() const {
367 return _bytes_copied_during_gc;
368 }
369
370 // Determine whether there are candidate regions so that the
371 // next GC should be mixed. The two action strings are used
372 // in the ergo output when the method returns true or false.
373 bool next_gc_should_be_mixed(const char* true_action_str,
374 const char* false_action_str) const;
375
376 virtual void finalize_collection_set(double target_pause_time_ms);
377 private:
378 // Set the state to start a concurrent marking cycle and clear
379 // _initiate_conc_mark_if_possible because it has now been
380 // acted on.
381 void initiate_conc_mark();
382
383 public:
384 // This sets the initiate_conc_mark_if_possible() flag to start a
385 // new cycle, as long as we are not already in one. It's best if it
386 // is called during a safepoint when the test whether a cycle is in
387 // progress or not is stable.
388 bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
389
390 // This is called at the very beginning of an evacuation pause (it
391 // has to be the first thing that the pause does). If
392 // initiate_conc_mark_if_possible() is true, and the concurrent
393 // marking thread has completed its work during the previous cycle,
394 // it will set during_initial_mark_pause() to so that the pause does
395 // the initial-mark work and start a marking cycle.
396 void decide_on_conc_mark_initiation();
397
398 // If an expansion would be appropriate, because recent GC overhead had
399 // exceeded the desired limit, return an amount to expand by.
400 virtual size_t expansion_amount();
401
402 // Clear ratio tracking data used by expansion_amount().
403 void clear_ratio_check_data();
404
405 // Print stats on young survival ratio
406 void print_yg_surv_rate_info() const;
407
408 void finished_recalculating_age_indexes(bool is_survivors) {
409 if (is_survivors) {
410 _survivor_surv_rate_group->finished_recalculating_age_indexes();
411 } else {
412 _short_lived_surv_rate_group->finished_recalculating_age_indexes();
413 }
414 }
415
416 size_t young_list_target_length() const { return _young_list_target_length; }
417
418 bool is_young_list_full() const;
419
420 bool can_expand_young_list() const;
421
422 uint young_list_max_length() const {
423 return _young_list_max_length;
424 }
425
426 bool adaptive_young_list_length() const;
427
428 virtual bool should_process_references() const {
429 return true;
430 }
431
432 private:
433 //
434 // Survivor regions policy.
435 //
436
437 // Current tenuring threshold, set to 0 if the collector reaches the
438 // maximum amount of survivors regions.
439 uint _tenuring_threshold;
440
441 // The limit on the number of regions allocated for survivors.
442 uint _max_survivor_regions;
443
444 AgeTable _survivors_age_table;
445
446 public:
447 uint tenuring_threshold() const { return _tenuring_threshold; }
448
449 uint max_survivor_regions() {
450 return _max_survivor_regions;
451 }
452
453 static const uint REGIONS_UNLIMITED = (uint) -1;
454
455 uint max_regions(InCSetState dest) const {
456 switch (dest.value()) {
457 case InCSetState::Young:
458 return _max_survivor_regions;
459 case InCSetState::Old:
460 return REGIONS_UNLIMITED;
461 default:
462 assert(false, "Unknown dest state: " CSETSTATE_FORMAT, dest.value());
463 break;
464 }
465 // keep some compilers happy
466 return 0;
467 }
468
469 void note_start_adding_survivor_regions() {
470 _survivor_surv_rate_group->start_adding_regions();
471 }
472
473 void note_stop_adding_survivor_regions() {
474 _survivor_surv_rate_group->stop_adding_regions();
475 }
476
477 void record_age_table(AgeTable* age_table) {
478 _survivors_age_table.merge(age_table);
479 }
480
481 void update_max_gc_locker_expansion();
482
483 // Calculates survivor space parameters.
484 void update_survivors_policy();
485
486 virtual void post_heap_initialize();
487 };
488
489 #endif // SHARE_VM_GC_G1_G1COLLECTORPOLICY_HPP