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 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 protected:
173 G1CollectionSet* _collection_set;
174 virtual double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const;
175 virtual double other_time_ms(double pause_time_ms) const;
176
177 double young_other_time_ms() const;
178 double non_young_other_time_ms() const;
179 double constant_other_time_ms(double pause_time_ms) const;
180
181 CollectionSetChooser* cset_chooser() const;
182 private:
183
184 // The number of bytes copied during the GC.
185 size_t _bytes_copied_during_gc;
186
187 // Stash a pointer to the g1 heap.
188 G1CollectedHeap* _g1;
189
190 G1GCPhaseTimes* _phase_times;
191
192 // This set of variables tracks the collector efficiency, in order to
193 // determine whether we should initiate a new marking.
194 double _mark_remark_start_sec;
195 double _mark_cleanup_start_sec;
196
197 // Updates the internal young list maximum and target lengths. Returns the
198 // unbounded young list target length.
199 uint update_young_list_max_and_target_length();
200 uint update_young_list_max_and_target_length(size_t rs_lengths);
201
202 // Update the young list target length either by setting it to the
203 // desired fixed value or by calculating it using G1's pause
204 // prediction model. If no rs_lengths parameter is passed, predict
205 // the RS lengths using the prediction model, otherwise use the
206 // given rs_lengths as the prediction.
207 // Returns the unbounded young list target length.
208 uint update_young_list_target_length(size_t rs_lengths);
209
210 // Calculate and return the minimum desired young list target
211 // length. This is the minimum desired young list length according
212 // to the user's inputs.
213 uint calculate_young_list_desired_min_length(uint base_min_length) const;
214
215 // Calculate and return the maximum desired young list target
216 // length. This is the maximum desired young list length according
217 // to the user's inputs.
218 uint calculate_young_list_desired_max_length() const;
219
220 // Calculate and return the maximum young list target length that
221 // can fit into the pause time goal. The parameters are: rs_lengths
222 // represent the prediction of how large the young RSet lengths will
223 // be, base_min_length is the already existing number of regions in
224 // the young list, min_length and max_length are the desired min and
225 // max young list length according to the user's inputs.
226 uint calculate_young_list_target_length(size_t rs_lengths,
227 uint base_min_length,
228 uint desired_min_length,
229 uint desired_max_length) const;
230
231 // Result of the bounded_young_list_target_length() method, containing both the
232 // bounded as well as the unbounded young list target lengths in this order.
233 typedef Pair<uint, uint, StackObj> YoungTargetLengths;
234 YoungTargetLengths young_list_target_lengths(size_t rs_lengths) const;
235
236 void update_rs_lengths_prediction();
237 void update_rs_lengths_prediction(size_t prediction);
238
239 // Check whether a given young length (young_length) fits into the
240 // given target pause time and whether the prediction for the amount
241 // of objects to be copied for the given length will fit into the
242 // given free space (expressed by base_free_regions). It is used by
243 // calculate_young_list_target_length().
244 bool predict_will_fit(uint young_length, double base_time_ms,
245 uint base_free_regions, double target_pause_time_ms) const;
246
247 public:
248 size_t pending_cards() const { return _pending_cards; }
249
250 // Calculate the minimum number of old regions we'll add to the CSet
251 // during a mixed GC.
252 uint calc_min_old_cset_length() const;
253
254 // Calculate the maximum number of old regions we'll add to the CSet
255 // during a mixed GC.
256 uint calc_max_old_cset_length() const;
257
258 // Returns the given amount of uncollected reclaimable space
259 // as a percentage of the current heap capacity.
260 double reclaimable_bytes_perc(size_t reclaimable_bytes) const;
261
262 private:
263 // Sets up marking if proper conditions are met.
264 void maybe_start_marking();
265
266 // The kind of STW pause.
267 enum PauseKind {
268 FullGC,
269 YoungOnlyGC,
270 MixedGC,
271 LastYoungGC,
272 InitialMarkGC,
273 Cleanup,
274 Remark
275 };
276
277 // Calculate PauseKind from internal state.
278 PauseKind young_gc_pause_kind() const;
279 // Record the given STW pause with the given start and end times (in s).
280 void record_pause(PauseKind kind, double start, double end);
281 // Indicate that we aborted marking before doing any mixed GCs.
282 void abort_time_to_mixed_tracking();
283 public:
284
285 G1CollectorPolicy();
286
287 virtual ~G1CollectorPolicy();
288
289 virtual G1CollectorPolicy* as_g1_policy() { return this; }
290
291 G1CollectorState* collector_state() const;
292
293 G1GCPhaseTimes* phase_times() const { return _phase_times; }
294
295 // Check the current value of the young list RSet lengths and
296 // compare it against the last prediction. If the current value is
297 // higher, recalculate the young list target length prediction.
298 void revise_young_list_target_length_if_necessary(size_t rs_lengths);
299
300 // This should be called after the heap is resized.
301 void record_new_heap_size(uint new_number_of_regions);
302
303 void init();
304
305 virtual void note_gc_start(uint num_active_workers);
306
307 // Create jstat counters for the policy.
308 virtual void initialize_gc_policy_counters();
309
310 bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
311
312 bool about_to_start_mixed_phase() const;
313
314 // Record the start and end of an evacuation pause.
315 void record_collection_pause_start(double start_time_sec);
316 void record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc);
317
318 // Record the start and end of a full collection.
319 void record_full_collection_start();
320 void record_full_collection_end();
321
322 // Must currently be called while the world is stopped.
323 void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
324
325 // Record start and end of remark.
326 void record_concurrent_mark_remark_start();
327 void record_concurrent_mark_remark_end();
328
329 // Record start, end, and completion of cleanup.
330 void record_concurrent_mark_cleanup_start();
331 void record_concurrent_mark_cleanup_end();
332 void record_concurrent_mark_cleanup_completed();
333
334 virtual void print_phases();
335
336 // Record how much space we copied during a GC. This is typically
337 // called when a GC alloc region is being retired.
338 void record_bytes_copied_during_gc(size_t bytes) {
339 _bytes_copied_during_gc += bytes;
340 }
341
342 // The amount of space we copied during a GC.
343 size_t bytes_copied_during_gc() const {
344 return _bytes_copied_during_gc;
345 }
346
347 // Determine whether there are candidate regions so that the
348 // next GC should be mixed. The two action strings are used
349 // in the ergo output when the method returns true or false.
350 bool next_gc_should_be_mixed(const char* true_action_str,
351 const char* false_action_str) const;
352
353 virtual void finalize_collection_set(double target_pause_time_ms);
354 private:
355 // Set the state to start a concurrent marking cycle and clear
356 // _initiate_conc_mark_if_possible because it has now been
357 // acted on.
358 void initiate_conc_mark();
359
360 public:
361 // This sets the initiate_conc_mark_if_possible() flag to start a
362 // new cycle, as long as we are not already in one. It's best if it
363 // is called during a safepoint when the test whether a cycle is in
364 // progress or not is stable.
365 bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
366
367 // This is called at the very beginning of an evacuation pause (it
368 // has to be the first thing that the pause does). If
369 // initiate_conc_mark_if_possible() is true, and the concurrent
370 // marking thread has completed its work during the previous cycle,
371 // it will set during_initial_mark_pause() to so that the pause does
372 // the initial-mark work and start a marking cycle.
373 void decide_on_conc_mark_initiation();
374
375 // Print stats on young survival ratio
376 void print_yg_surv_rate_info() const;
377
378 void finished_recalculating_age_indexes(bool is_survivors) {
379 if (is_survivors) {
380 _survivor_surv_rate_group->finished_recalculating_age_indexes();
381 } else {
382 _short_lived_surv_rate_group->finished_recalculating_age_indexes();
383 }
384 }
385
386 size_t young_list_target_length() const { return _young_list_target_length; }
387
388 bool is_young_list_full() const;
389
390 bool can_expand_young_list() const;
391
392 uint young_list_max_length() const {
393 return _young_list_max_length;
394 }
395
396 bool adaptive_young_list_length() const;
397
398 virtual bool should_process_references() const {
399 return true;
400 }
401
402 private:
403 //
404 // Survivor regions policy.
405 //
406
407 // Current tenuring threshold, set to 0 if the collector reaches the
408 // maximum amount of survivors regions.
409 uint _tenuring_threshold;
410
411 // The limit on the number of regions allocated for survivors.
412 uint _max_survivor_regions;
413
414 AgeTable _survivors_age_table;
415
416 public:
417 uint tenuring_threshold() const { return _tenuring_threshold; }
418
419 uint max_survivor_regions() {
420 return _max_survivor_regions;
421 }
422
423 void note_start_adding_survivor_regions() {
424 _survivor_surv_rate_group->start_adding_regions();
425 }
426
427 void note_stop_adding_survivor_regions() {
428 _survivor_surv_rate_group->stop_adding_regions();
429 }
430
431 void record_age_table(AgeTable* age_table) {
432 _survivors_age_table.merge(age_table);
433 }
434
435 void update_max_gc_locker_expansion();
436
437 // Calculates survivor space parameters.
438 void update_survivors_policy();
439
440 virtual void post_heap_initialize();
441 };
442
443 #endif // SHARE_VM_GC_G1_G1COLLECTORPOLICY_HPP