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 #include "precompiled.hpp"
26 #include "gc/g1/g1CollectedHeap.hpp"
27 #include "gc/g1/g1CollectionSet.hpp"
28 #include "gc/g1/g1CollectorState.hpp"
29 #include "gc/g1/g1FixedSizeStack.inline.hpp"
30 #include "gc/g1/g1Policy.hpp"
31 #include "gc/g1/heapRegion.inline.hpp"
32 #include "gc/g1/heapRegionRemSet.hpp"
33 #include "gc/g1/heapRegionSet.hpp"
34 #include "logging/logStream.hpp"
35 #include "utilities/debug.hpp"
36
37 G1CollectorState* G1CollectionSet::collector_state() {
38 return _g1->collector_state();
39 }
40
41 G1GCPhaseTimes* G1CollectionSet::phase_times() {
42 return _policy->phase_times();
43 }
44
45 CollectionSetChooser* G1CollectionSet::cset_chooser() {
46 return _cset_chooser;
47 }
48
49 double G1CollectionSet::predict_region_elapsed_time_ms(HeapRegion* hr) {
50 return _policy->predict_region_elapsed_time_ms(hr, collector_state()->gcs_are_young());
51 }
52
53 G1CollectionSet::G1CollectionSet(G1CollectedHeap* g1h, G1Policy* policy) :
54 _g1(g1h),
55 _policy(policy),
56 _cset_chooser(new CollectionSetChooser()),
57 _eden_region_length(0),
58 _survivor_region_length(0),
59 _old_region_length(0),
60 _collection_set_regions(),
61 _bytes_used_before(0),
62 _recorded_rs_lengths(0),
63 // Incremental CSet attributes
64 _inc_build_state(Inactive),
65 _inc_bytes_used_before(0),
66 _inc_recorded_rs_lengths(0),
67 _inc_recorded_rs_lengths_diffs(0),
68 _inc_predicted_elapsed_time_ms(0.0),
69 _inc_predicted_elapsed_time_ms_diffs(0.0) {
70 }
71
72 G1CollectionSet::~G1CollectionSet() {
73 delete _cset_chooser;
74 }
75
76 void G1CollectionSet::init_region_lengths(uint eden_cset_region_length,
77 uint survivor_cset_region_length) {
78 _eden_region_length = eden_cset_region_length;
79 _survivor_region_length = survivor_cset_region_length;
80
81 assert((size_t) young_region_length() == _collection_set_regions.length(),
82 "Young region length %u should match collection set length " SIZE_FORMAT, young_region_length(), _collection_set_regions.length());
83
84 _old_region_length = 0;
85 }
86
87 void G1CollectionSet::set_max_length(uint max_region_length) {
88 guarantee(_collection_set_regions.max_length() == 0, "Must only initialize once.");
89 _collection_set_regions.initialize(max_region_length);
90 }
91
92 void G1CollectionSet::set_recorded_rs_lengths(size_t rs_lengths) {
93 _recorded_rs_lengths = rs_lengths;
94 }
95
96 // Add the heap region at the head of the non-incremental collection set
97 void G1CollectionSet::add_old_region(HeapRegion* hr) {
98 assert(_inc_build_state == Active, "Precondition");
99 assert(hr->is_old(), "the region should be old");
100
101 assert(!hr->in_collection_set(), "should not already be in the CSet");
102 _g1->register_old_region_with_cset(hr);
103
104 _collection_set_regions.par_push(hr->hrm_index());
105
106 _bytes_used_before += hr->used();
107 size_t rs_length = hr->rem_set()->occupied();
108 _recorded_rs_lengths += rs_length;
109 _old_region_length += 1;
110 }
111
112 // Initialize the per-collection-set information
113 void G1CollectionSet::start_incremental_building() {
114 assert(_collection_set_regions.length() == 0, "Must be empty before starting a new collection set.");
115 assert(_inc_build_state == Inactive, "Precondition");
116
117 _collection_set_regions.clear();
118
119 _inc_bytes_used_before = 0;
120
121 _inc_recorded_rs_lengths = 0;
122 _inc_recorded_rs_lengths_diffs = 0;
123 _inc_predicted_elapsed_time_ms = 0.0;
124 _inc_predicted_elapsed_time_ms_diffs = 0.0;
125 _inc_build_state = Active;
126 }
127
128 void G1CollectionSet::finalize_incremental_building() {
129 assert(_inc_build_state == Active, "Precondition");
130 assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
131
132 // The two "main" fields, _inc_recorded_rs_lengths and
133 // _inc_predicted_elapsed_time_ms, are updated by the thread
134 // that adds a new region to the CSet. Further updates by the
135 // concurrent refinement thread that samples the young RSet lengths
136 // are accumulated in the *_diffs fields. Here we add the diffs to
137 // the "main" fields.
138
139 if (_inc_recorded_rs_lengths_diffs >= 0) {
140 _inc_recorded_rs_lengths += _inc_recorded_rs_lengths_diffs;
141 } else {
142 // This is defensive. The diff should in theory be always positive
143 // as RSets can only grow between GCs. However, given that we
144 // sample their size concurrently with other threads updating them
145 // it's possible that we might get the wrong size back, which
146 // could make the calculations somewhat inaccurate.
147 size_t diffs = (size_t) (-_inc_recorded_rs_lengths_diffs);
148 if (_inc_recorded_rs_lengths >= diffs) {
149 _inc_recorded_rs_lengths -= diffs;
150 } else {
151 _inc_recorded_rs_lengths = 0;
152 }
153 }
154 _inc_predicted_elapsed_time_ms += _inc_predicted_elapsed_time_ms_diffs;
155
156 _inc_recorded_rs_lengths_diffs = 0;
157 _inc_predicted_elapsed_time_ms_diffs = 0.0;
158 }
159
160 void G1CollectionSet::iterate(HeapRegionClosure* cl) {
161 iterate_from(cl, 0, 1, true);
162 }
163
164 void G1CollectionSet::iterate_from(HeapRegionClosure* cl, uint worker_id, uint total_workers, bool may_be_aborted) {
165 size_t len = _collection_set_regions.length();
166 if (len == 0) {
167 return;
168 }
169 size_t start_pos = (worker_id * len) / total_workers;
170 size_t cur_pos = start_pos;
171
172 do {
173 HeapRegion* r = G1CollectedHeap::heap()->region_at(_collection_set_regions.get_by_index(cur_pos));
174 bool result = cl->doHeapRegion(r);
175 guarantee(may_be_aborted || !result, "This iteration should not abort.");
176 if (result) {
177 return;
178 }
179 cur_pos++;
180 if (cur_pos == len) {
181 cur_pos = 0;
182 }
183 } while (cur_pos != start_pos);
184 }
185
186 void G1CollectionSet::update_young_region_prediction(HeapRegion* hr,
187 size_t new_rs_length) {
188 // Update the CSet information that is dependent on the new RS length
189 assert(hr->is_young(), "Precondition");
190 assert(!SafepointSynchronize::is_at_safepoint(), "should not be at a safepoint");
191
192 // We could have updated _inc_recorded_rs_lengths and
193 // _inc_predicted_elapsed_time_ms directly but we'd need to do
194 // that atomically, as this code is executed by a concurrent
195 // refinement thread, potentially concurrently with a mutator thread
196 // allocating a new region and also updating the same fields. To
197 // avoid the atomic operations we accumulate these updates on two
198 // separate fields (*_diffs) and we'll just add them to the "main"
199 // fields at the start of a GC.
200
201 ssize_t old_rs_length = (ssize_t) hr->recorded_rs_length();
202 ssize_t rs_lengths_diff = (ssize_t) new_rs_length - old_rs_length;
203 _inc_recorded_rs_lengths_diffs += rs_lengths_diff;
204
205 double old_elapsed_time_ms = hr->predicted_elapsed_time_ms();
206 double new_region_elapsed_time_ms = predict_region_elapsed_time_ms(hr);
207 double elapsed_ms_diff = new_region_elapsed_time_ms - old_elapsed_time_ms;
208 _inc_predicted_elapsed_time_ms_diffs += elapsed_ms_diff;
209
210 hr->set_recorded_rs_length(new_rs_length);
211 hr->set_predicted_elapsed_time_ms(new_region_elapsed_time_ms);
212 }
213
214 void G1CollectionSet::add_young_region_common(HeapRegion* hr) {
215 assert(hr->is_young(), "invariant");
216 assert(_inc_build_state == Active, "Precondition");
217
218 size_t collection_set_length = _collection_set_regions.length();
219 assert(collection_set_length <= INT_MAX, "Collection set is too large with %d entries", (int)collection_set_length);
220 hr->set_young_index_in_cset((int)collection_set_length);
221 _collection_set_regions.par_push(hr->hrm_index());
222
223 // This routine is used when:
224 // * adding survivor regions to the incremental cset at the end of an
225 // evacuation pause or
226 // * adding the current allocation region to the incremental cset
227 // when it is retired.
228 // Therefore this routine may be called at a safepoint by the
229 // VM thread, or in-between safepoints by mutator threads (when
230 // retiring the current allocation region)
231 // We need to clear and set the cached recorded/cached collection set
232 // information in the heap region here (before the region gets added
233 // to the collection set). An individual heap region's cached values
234 // are calculated, aggregated with the policy collection set info,
235 // and cached in the heap region here (initially) and (subsequently)
236 // by the Young List sampling code.
237
238 size_t rs_length = hr->rem_set()->occupied();
239 double region_elapsed_time_ms = predict_region_elapsed_time_ms(hr);
240
241 // Cache the values we have added to the aggregated information
242 // in the heap region in case we have to remove this region from
243 // the incremental collection set, or it is updated by the
244 // rset sampling code
245 hr->set_recorded_rs_length(rs_length);
246 hr->set_predicted_elapsed_time_ms(region_elapsed_time_ms);
247
248 size_t used_bytes = hr->used();
249 _inc_recorded_rs_lengths += rs_length;
250 _inc_predicted_elapsed_time_ms += region_elapsed_time_ms;
251 _inc_bytes_used_before += used_bytes;
252
253 assert(!hr->in_collection_set(), "invariant");
254 _g1->register_young_region_with_cset(hr);
255 }
256
257 void G1CollectionSet::add_survivor_regions(HeapRegion* hr) {
258 assert(hr->is_survivor(), "Must only add survivor regions, but is %s", hr->get_type_str());
259 add_young_region_common(hr);
260 }
261
262 void G1CollectionSet::add_eden_region(HeapRegion* hr) {
263 assert(hr->is_eden(), "Must only add eden regions, but is %s", hr->get_type_str());
264 add_young_region_common(hr);
265 }
266
267 #ifndef PRODUCT
268 bool G1CollectionSet::verify_young_ages() {
269 bool ret = true;
270
271 size_t length = _collection_set_regions.length();
272 for (size_t i = 0; i < length; i++) {
273 HeapRegion* curr = G1CollectedHeap::heap()->region_at(_collection_set_regions.get_by_index(i));
274
275 guarantee(curr->is_young(), "Region must be young but is %s", curr->get_type_str());
276
277 SurvRateGroup* group = curr->surv_rate_group();
278
279 if (group == NULL) {
280 log_error(gc, verify)("## encountered NULL surv_rate_group in young region");
281 ret = false;
282 }
283
284 if (curr->age_in_surv_rate_group() < 0) {
285 log_error(gc, verify)("## encountered negative age in young region");
286 ret = false;
287 }
288 }
289
290 if (!ret) {
291 LogStreamHandle(Error, gc, verify) log;
292 print(&log);
293 }
294
295 return ret;
296 }
297
298 class G1PrintCollectionSetClosure : public HeapRegionClosure {
299 outputStream* _st;
300 public:
301 G1PrintCollectionSetClosure(outputStream* st) : HeapRegionClosure(), _st(st) { }
302
303 virtual bool doHeapRegion(HeapRegion* r) {
304 assert(r->in_collection_set(), "Region %u should be in collection set", r->hrm_index());
305 _st->print_cr(" " HR_FORMAT ", P: " PTR_FORMAT "N: " PTR_FORMAT ", age: %4d",
306 HR_FORMAT_PARAMS(r),
307 p2i(r->prev_top_at_mark_start()),
308 p2i(r->next_top_at_mark_start()),
309 r->age_in_surv_rate_group_cond());
310 return false;
311 }
312 };
313
314 void G1CollectionSet::print(outputStream* st) {
315 st->print_cr("\nCollection_set:");
316
317 G1PrintCollectionSetClosure cl(st);
318 iterate(&cl);
319 }
320 #endif // !PRODUCT
321
322 double G1CollectionSet::finalize_young_part(double target_pause_time_ms, G1SurvivorRegions* survivors) {
323 double young_start_time_sec = os::elapsedTime();
324
325 finalize_incremental_building();
326
327 guarantee(target_pause_time_ms > 0.0,
328 "target_pause_time_ms = %1.6lf should be positive", target_pause_time_ms);
329
330 size_t pending_cards = _policy->pending_cards();
331 double base_time_ms = _policy->predict_base_elapsed_time_ms(pending_cards);
332 double time_remaining_ms = MAX2(target_pause_time_ms - base_time_ms, 0.0);
333
334 log_trace(gc, ergo, cset)("Start choosing CSet. pending cards: " SIZE_FORMAT " predicted base time: %1.2fms remaining time: %1.2fms target pause time: %1.2fms",
335 pending_cards, base_time_ms, time_remaining_ms, target_pause_time_ms);
336
337 collector_state()->set_last_gc_was_young(collector_state()->gcs_are_young());
338
339 // The young list is laid with the survivor regions from the previous
340 // pause are appended to the RHS of the young list, i.e.
341 // [Newly Young Regions ++ Survivors from last pause].
342
343 uint survivor_region_length = survivors->length();
344 uint eden_region_length = _g1->eden_regions_count();
345 init_region_lengths(eden_region_length, survivor_region_length);
346
347 verify_young_cset_indices();
348
349 // Clear the fields that point to the survivor list - they are all young now.
350 survivors->convert_to_eden();
351
352 _bytes_used_before = _inc_bytes_used_before;
353 time_remaining_ms = MAX2(time_remaining_ms - _inc_predicted_elapsed_time_ms, 0.0);
354
355 log_trace(gc, ergo, cset)("Add young regions to CSet. eden: %u regions, survivors: %u regions, predicted young region time: %1.2fms, target pause time: %1.2fms",
356 eden_region_length, survivor_region_length, _inc_predicted_elapsed_time_ms, target_pause_time_ms);
357
358 // The number of recorded young regions is the incremental
359 // collection set's current size
360 set_recorded_rs_lengths(_inc_recorded_rs_lengths);
361
362 double young_end_time_sec = os::elapsedTime();
363 phase_times()->record_young_cset_choice_time_ms((young_end_time_sec - young_start_time_sec) * 1000.0);
364
365 return time_remaining_ms;
366 }
367
368 void G1CollectionSet::finalize_old_part(double time_remaining_ms) {
369 double non_young_start_time_sec = os::elapsedTime();
370 double predicted_old_time_ms = 0.0;
371
372 if (!collector_state()->gcs_are_young()) {
373 cset_chooser()->verify();
374 const uint min_old_cset_length = _policy->calc_min_old_cset_length();
375 const uint max_old_cset_length = _policy->calc_max_old_cset_length();
376
377 uint expensive_region_num = 0;
378 bool check_time_remaining = _policy->adaptive_young_list_length();
379
380 HeapRegion* hr = cset_chooser()->peek();
381 while (hr != NULL) {
382 if (old_region_length() >= max_old_cset_length) {
383 // Added maximum number of old regions to the CSet.
384 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (old CSet region num reached max). old %u regions, max %u regions",
385 old_region_length(), max_old_cset_length);
386 break;
387 }
388
389 // Stop adding regions if the remaining reclaimable space is
390 // not above G1HeapWastePercent.
391 size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes();
392 double reclaimable_perc = _policy->reclaimable_bytes_perc(reclaimable_bytes);
393 double threshold = (double) G1HeapWastePercent;
394 if (reclaimable_perc <= threshold) {
395 // We've added enough old regions that the amount of uncollected
396 // reclaimable space is at or below the waste threshold. Stop
397 // adding old regions to the CSet.
398 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (reclaimable percentage not over threshold). "
399 "old %u regions, max %u regions, reclaimable: " SIZE_FORMAT "B (%1.2f%%) threshold: " UINTX_FORMAT "%%",
400 old_region_length(), max_old_cset_length, reclaimable_bytes, reclaimable_perc, G1HeapWastePercent);
401 break;
402 }
403
404 double predicted_time_ms = predict_region_elapsed_time_ms(hr);
405 if (check_time_remaining) {
406 if (predicted_time_ms > time_remaining_ms) {
407 // Too expensive for the current CSet.
408
409 if (old_region_length() >= min_old_cset_length) {
410 // We have added the minimum number of old regions to the CSet,
411 // we are done with this CSet.
412 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (predicted time is too high). "
413 "predicted time: %1.2fms, remaining time: %1.2fms old %u regions, min %u regions",
414 predicted_time_ms, time_remaining_ms, old_region_length(), min_old_cset_length);
415 break;
416 }
417
418 // We'll add it anyway given that we haven't reached the
419 // minimum number of old regions.
420 expensive_region_num += 1;
421 }
422 } else {
423 if (old_region_length() >= min_old_cset_length) {
424 // In the non-auto-tuning case, we'll finish adding regions
425 // to the CSet if we reach the minimum.
426
427 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (old CSet region num reached min). old %u regions, min %u regions",
428 old_region_length(), min_old_cset_length);
429 break;
430 }
431 }
432
433 // We will add this region to the CSet.
434 time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0);
435 predicted_old_time_ms += predicted_time_ms;
436 cset_chooser()->pop(); // already have region via peek()
437 _g1->old_set_remove(hr);
438 add_old_region(hr);
439
440 hr = cset_chooser()->peek();
441 }
442 if (hr == NULL) {
443 log_debug(gc, ergo, cset)("Finish adding old regions to CSet (candidate old regions not available)");
444 }
445
446 if (expensive_region_num > 0) {
447 // We print the information once here at the end, predicated on
448 // whether we added any apparently expensive regions or not, to
449 // avoid generating output per region.
450 log_debug(gc, ergo, cset)("Added expensive regions to CSet (old CSet region num not reached min)."
451 "old: %u regions, expensive: %u regions, min: %u regions, remaining time: %1.2fms",
452 old_region_length(), expensive_region_num, min_old_cset_length, time_remaining_ms);
453 }
454
455 cset_chooser()->verify();
456 }
457
458 stop_incremental_building();
459
460 log_debug(gc, ergo, cset)("Finish choosing CSet. old: %u regions, predicted old region time: %1.2fms, time remaining: %1.2f",
461 old_region_length(), predicted_old_time_ms, time_remaining_ms);
462
463 double non_young_end_time_sec = os::elapsedTime();
464 phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0);
465 }
466
467 #ifdef ASSERT
468 void G1CollectionSet::verify_young_cset_indices() const {
469 ResourceMark rm;
470 uint* heap_region_indices = NEW_RESOURCE_ARRAY(uint, young_region_length());
471 for (uint i = 0; i < young_region_length(); ++i) {
472 heap_region_indices[i] = (uint)-1;
473 }
474
475 size_t length = _collection_set_regions.length();
476 for (size_t i = 0; i < length; i++) {
477 HeapRegion* hr = G1CollectedHeap::heap()->region_at(_collection_set_regions.get_by_index(i));
478
479 const int idx = hr->young_index_in_cset();
480 assert(idx > -1, "Young index must be set for all regions in the incremental collection set but is not for region %u.", hr->hrm_index());
481 assert((uint)idx < young_region_length(), "Young cset index too large for region %u", hr->hrm_index());
482
483 assert(heap_region_indices[idx] == (uint)-1,
484 "Index %d used by multiple regions, first use by region %u, second by region %u",
485 idx, heap_region_indices[idx], hr->hrm_index());
486
487 heap_region_indices[idx] = hr->hrm_index();
488 }
489 }
490 #endif