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