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.
22 *
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
50 class G1Policy: public CHeapObj<mtGC> {
51 private:
52 G1IHOPControl* _ihop_control;
53
54 G1IHOPControl* create_ihop_control() const;
55 // Update the IHOP control with necessary statistics.
56 void update_ihop_prediction(double mutator_time_s,
57 size_t mutator_alloc_bytes,
58 size_t young_gen_size);
59 void report_ihop_statistics();
60
61 G1Predictions _predictor;
62 G1Analytics* _analytics;
63 G1MMUTracker* _mmu_tracker;
64
65 double _full_collection_start_sec;
66
67 uint _young_list_target_length;
68 uint _young_list_fixed_length;
69
70 // The max number of regions we can extend the eden by while the GC
71 // locker is active. This should be >= _young_list_target_length;
72 uint _young_list_max_length;
73
74 SurvRateGroup* _short_lived_surv_rate_group;
75 SurvRateGroup* _survivor_surv_rate_group;
76
77 double _reserve_factor;
78 uint _reserve_regions;
79
80 G1YoungGenSizer _young_gen_sizer;
81
82 uint _free_regions_at_end_of_collection;
83
84 size_t _max_rs_lengths;
85
86 size_t _rs_lengths_prediction;
87
88 #ifndef PRODUCT
89 bool verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group);
90 #endif // PRODUCT
91
92 double _pause_time_target_ms;
93
94 size_t _pending_cards;
95
96 // The amount of allocated bytes in old gen during the last mutator and the following
97 // young GC phase.
98 size_t _bytes_allocated_in_old_since_last_gc;
99
100 G1InitialMarkToMixedTimeTracker _initial_mark_to_mixed;
101 public:
102 const G1Predictions& predictor() const { return _predictor; }
103 const G1Analytics* analytics() const { return const_cast<const G1Analytics*>(_analytics); }
104
105 // Add the given number of bytes to the total number of allocated bytes in the old gen.
106 void add_bytes_allocated_in_old_since_last_gc(size_t bytes) { _bytes_allocated_in_old_since_last_gc += bytes; }
107
108 // Accessors
109
110 void set_region_eden(HeapRegion* hr, int young_index_in_cset) {
111 hr->set_eden();
112 hr->install_surv_rate_group(_short_lived_surv_rate_group);
113 hr->set_young_index_in_cset(young_index_in_cset);
114 }
115
116 void set_region_survivor(HeapRegion* hr, int young_index_in_cset) {
117 assert(hr->is_survivor(), "pre-condition");
118 hr->install_surv_rate_group(_survivor_surv_rate_group);
119 hr->set_young_index_in_cset(young_index_in_cset);
120 }
121
122 #ifndef PRODUCT
123 bool verify_young_ages();
124 #endif // PRODUCT
125
126 void record_max_rs_lengths(size_t rs_lengths) {
127 _max_rs_lengths = rs_lengths;
128 }
129
130
131 double predict_base_elapsed_time_ms(size_t pending_cards) const;
132 double predict_base_elapsed_time_ms(size_t pending_cards,
133 size_t scanned_cards) const;
134 size_t predict_bytes_to_copy(HeapRegion* hr) const;
135 double predict_region_elapsed_time_ms(HeapRegion* hr, bool for_young_gc) const;
136
137 double predict_survivor_regions_evac_time() const;
138
139 bool should_update_surv_rate_group_predictors() {
140 return collector_state()->last_gc_was_young() && !collector_state()->in_marking_window();
141 }
142
143 void cset_regions_freed() {
144 bool update = should_update_surv_rate_group_predictors();
145
146 _short_lived_surv_rate_group->all_surviving_words_recorded(update);
147 _survivor_surv_rate_group->all_surviving_words_recorded(update);
148 }
149
150 G1MMUTracker* mmu_tracker() {
151 return _mmu_tracker;
152 }
153
154 const G1MMUTracker* mmu_tracker() const {
155 return _mmu_tracker;
156 }
157
158 double max_pause_time_ms() const {
159 return _mmu_tracker->max_gc_time() * 1000.0;
160 }
161
162 // Returns an estimate of the survival rate of the region at yg-age
163 // "yg_age".
164 double predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const;
165
166 double predict_yg_surv_rate(int age) const;
167
168 double accum_yg_surv_rate_pred(int age) const;
169
170 protected:
171 G1CollectionSet* _collection_set;
172 virtual double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const;
173 virtual double other_time_ms(double pause_time_ms) const;
174
175 double young_other_time_ms() const;
176 double non_young_other_time_ms() const;
177 double constant_other_time_ms(double pause_time_ms) const;
178
179 CollectionSetChooser* cset_chooser() const;
180 private:
181
182 // The number of bytes copied during the GC.
183 size_t _bytes_copied_during_gc;
184
185 // Stash a pointer to the g1 heap.
186 G1CollectedHeap* _g1;
187
188 G1GCPhaseTimes* _phase_times;
189
190 // This set of variables tracks the collector efficiency, in order to
191 // determine whether we should initiate a new marking.
192 double _mark_remark_start_sec;
193 double _mark_cleanup_start_sec;
194
195 // Updates the internal young list maximum and target lengths. Returns the
196 // unbounded young list target length.
197 uint update_young_list_max_and_target_length();
198 uint update_young_list_max_and_target_length(size_t rs_lengths);
199
200 // Update the young list target length either by setting it to the
201 // desired fixed value or by calculating it using G1's pause
202 // prediction model. If no rs_lengths parameter is passed, predict
203 // the RS lengths using the prediction model, otherwise use the
204 // given rs_lengths as the prediction.
205 // Returns the unbounded young list target length.
206 uint update_young_list_target_length(size_t rs_lengths);
207
208 // Calculate and return the minimum desired young list target
209 // length. This is the minimum desired young list length according
210 // to the user's inputs.
211 uint calculate_young_list_desired_min_length(uint base_min_length) const;
212
213 // Calculate and return the maximum desired young list target
214 // length. This is the maximum desired young list length according
215 // to the user's inputs.
216 uint calculate_young_list_desired_max_length() const;
217
218 // Calculate and return the maximum young list target length that
219 // can fit into the pause time goal. The parameters are: rs_lengths
220 // represent the prediction of how large the young RSet lengths will
221 // be, base_min_length is the already existing number of regions in
222 // the young list, min_length and max_length are the desired min and
223 // max young list length according to the user's inputs.
224 uint calculate_young_list_target_length(size_t rs_lengths,
225 uint base_min_length,
226 uint desired_min_length,
227 uint desired_max_length) const;
228
229 // Result of the bounded_young_list_target_length() method, containing both the
230 // bounded as well as the unbounded young list target lengths in this order.
231 typedef Pair<uint, uint, StackObj> YoungTargetLengths;
232 YoungTargetLengths young_list_target_lengths(size_t rs_lengths) const;
233
234 void update_rs_lengths_prediction();
235 void update_rs_lengths_prediction(size_t prediction);
236
237 // Check whether a given young length (young_length) fits into the
238 // given target pause time and whether the prediction for the amount
239 // of objects to be copied for the given length will fit into the
240 // given free space (expressed by base_free_regions). It is used by
241 // calculate_young_list_target_length().
242 bool predict_will_fit(uint young_length, double base_time_ms,
243 uint base_free_regions, double target_pause_time_ms) const;
244
245 public:
246 size_t pending_cards() const { return _pending_cards; }
247
248 // Calculate the minimum number of old regions we'll add to the CSet
249 // during a mixed GC.
250 uint calc_min_old_cset_length() const;
251
252 // Calculate the maximum number of old regions we'll add to the CSet
253 // during a mixed GC.
254 uint calc_max_old_cset_length() const;
255
256 // Returns the given amount of uncollected reclaimable space
257 // as a percentage of the current heap capacity.
258 double reclaimable_bytes_perc(size_t reclaimable_bytes) const;
259
260 private:
261 // Sets up marking if proper conditions are met.
262 void maybe_start_marking();
263
264 // The kind of STW pause.
265 enum PauseKind {
266 FullGC,
267 YoungOnlyGC,
268 MixedGC,
269 LastYoungGC,
270 InitialMarkGC,
271 Cleanup,
272 Remark
273 };
274
275 // Calculate PauseKind from internal state.
276 PauseKind young_gc_pause_kind() const;
277 // Record the given STW pause with the given start and end times (in s).
278 void record_pause(PauseKind kind, double start, double end);
279 // Indicate that we aborted marking before doing any mixed GCs.
280 void abort_time_to_mixed_tracking();
281 public:
282
283 G1Policy();
284
285 virtual ~G1Policy();
286
287 G1CollectorState* collector_state() const;
288
289 G1GCPhaseTimes* phase_times() const { return _phase_times; }
290
291 // Check the current value of the young list RSet lengths and
292 // compare it against the last prediction. If the current value is
293 // higher, recalculate the young list target length prediction.
294 void revise_young_list_target_length_if_necessary(size_t rs_lengths);
295
296 // This should be called after the heap is resized.
297 void record_new_heap_size(uint new_number_of_regions);
298
299 void init();
300
301 virtual void note_gc_start();
302
303 bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
304
305 bool about_to_start_mixed_phase() const;
306
307 // Record the start and end of an evacuation pause.
308 void record_collection_pause_start(double start_time_sec);
309 void record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc);
310
311 // Record the start and end of a full collection.
312 void record_full_collection_start();
313 void record_full_collection_end();
314
315 // Must currently be called while the world is stopped.
316 void record_concurrent_mark_init_end(double mark_init_elapsed_time_ms);
317
318 // Record start and end of remark.
319 void record_concurrent_mark_remark_start();
320 void record_concurrent_mark_remark_end();
321
322 // Record start, end, and completion of cleanup.
323 void record_concurrent_mark_cleanup_start();
324 void record_concurrent_mark_cleanup_end();
325 void record_concurrent_mark_cleanup_completed();
326
327 virtual void print_phases();
328
329 // Record how much space we copied during a GC. This is typically
330 // called when a GC alloc region is being retired.
331 void record_bytes_copied_during_gc(size_t bytes) {
332 _bytes_copied_during_gc += bytes;
333 }
334
335 // The amount of space we copied during a GC.
336 size_t bytes_copied_during_gc() const {
337 return _bytes_copied_during_gc;
338 }
339
340 // Determine whether there are candidate regions so that the
341 // next GC should be mixed. The two action strings are used
342 // in the ergo output when the method returns true or false.
343 bool next_gc_should_be_mixed(const char* true_action_str,
344 const char* false_action_str) const;
345
346 virtual void finalize_collection_set(double target_pause_time_ms);
347 private:
348 // Set the state to start a concurrent marking cycle and clear
349 // _initiate_conc_mark_if_possible because it has now been
350 // acted on.
351 void initiate_conc_mark();
352
353 public:
354 // This sets the initiate_conc_mark_if_possible() flag to start a
355 // new cycle, as long as we are not already in one. It's best if it
356 // is called during a safepoint when the test whether a cycle is in
357 // progress or not is stable.
358 bool force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause);
359
360 // This is called at the very beginning of an evacuation pause (it
361 // has to be the first thing that the pause does). If
362 // initiate_conc_mark_if_possible() is true, and the concurrent
363 // marking thread has completed its work during the previous cycle,
364 // it will set during_initial_mark_pause() to so that the pause does
365 // the initial-mark work and start a marking cycle.
366 void decide_on_conc_mark_initiation();
367
368 // Print stats on young survival ratio
369 void print_yg_surv_rate_info() const;
370
371 void finished_recalculating_age_indexes(bool is_survivors) {
372 if (is_survivors) {
373 _survivor_surv_rate_group->finished_recalculating_age_indexes();
374 } else {
375 _short_lived_surv_rate_group->finished_recalculating_age_indexes();
376 }
377 }
378
379 size_t young_list_target_length() const { return _young_list_target_length; }
380
381 bool is_young_list_full() const;
382
383 bool can_expand_young_list() const;
384
385 uint young_list_max_length() const {
386 return _young_list_max_length;
387 }
388
389 bool adaptive_young_list_length() const;
390
391 virtual bool should_process_references() const {
392 return true;
393 }
394
395 private:
396 //
397 // Survivor regions policy.
398 //
399
400 // Current tenuring threshold, set to 0 if the collector reaches the
401 // maximum amount of survivors regions.
402 uint _tenuring_threshold;
403
404 // The limit on the number of regions allocated for survivors.
405 uint _max_survivor_regions;
406
407 AgeTable _survivors_age_table;
408
409 public:
410 uint tenuring_threshold() const { return _tenuring_threshold; }
411
412 uint max_survivor_regions() {
413 return _max_survivor_regions;
414 }
415
416 void note_start_adding_survivor_regions() {
417 _survivor_surv_rate_group->start_adding_regions();
418 }
419
420 void note_stop_adding_survivor_regions() {
421 _survivor_surv_rate_group->stop_adding_regions();
422 }
423
424 void record_age_table(AgeTable* age_table) {
425 _survivors_age_table.merge(age_table);
426 }
427
428 void update_max_gc_locker_expansion();
429
430 // Calculates survivor space parameters.
431 void update_survivors_policy();
432 };
433
434 #endif // SHARE_VM_GC_G1_G1POLICY_HPP