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rev 2869 : 7117303: VM uses non-monotonic time source and complains that it is non-monotonic
Summary: Replaces calls to os::javaTimeMillis(), which does not guarantee montonicity, in GC code to os::javaTimeNanos() with a suitable conversion factor. os::javaTimeNanos() mostly guarantees montonicity depending on the underlying OS implementation and, as a result, a better alternative. Changes in OS files are to make use of the newly defined constants in globalDefinitions.hpp.
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--- old/src/share/vm/gc_implementation/parallelScavenge/psMarkSweep.cpp
+++ new/src/share/vm/gc_implementation/parallelScavenge/psMarkSweep.cpp
1 1 /*
2 2 * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.
3 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 4 *
5 5 * This code is free software; you can redistribute it and/or modify it
6 6 * under the terms of the GNU General Public License version 2 only, as
7 7 * published by the Free Software Foundation.
8 8 *
9 9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 12 * version 2 for more details (a copy is included in the LICENSE file that
13 13 * accompanied this code).
14 14 *
15 15 * You should have received a copy of the GNU General Public License version
16 16 * 2 along with this work; if not, write to the Free Software Foundation,
17 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 18 *
19 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 20 * or visit www.oracle.com if you need additional information or have any
21 21 * questions.
22 22 *
23 23 */
24 24
25 25 #include "precompiled.hpp"
26 26 #include "classfile/symbolTable.hpp"
27 27 #include "classfile/systemDictionary.hpp"
28 28 #include "code/codeCache.hpp"
29 29 #include "gc_implementation/parallelScavenge/generationSizer.hpp"
30 30 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp"
31 31 #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp"
32 32 #include "gc_implementation/parallelScavenge/psMarkSweep.hpp"
33 33 #include "gc_implementation/parallelScavenge/psMarkSweepDecorator.hpp"
34 34 #include "gc_implementation/parallelScavenge/psOldGen.hpp"
35 35 #include "gc_implementation/parallelScavenge/psPermGen.hpp"
36 36 #include "gc_implementation/parallelScavenge/psScavenge.hpp"
37 37 #include "gc_implementation/parallelScavenge/psYoungGen.hpp"
38 38 #include "gc_implementation/shared/isGCActiveMark.hpp"
39 39 #include "gc_implementation/shared/spaceDecorator.hpp"
40 40 #include "gc_interface/gcCause.hpp"
41 41 #include "memory/gcLocker.inline.hpp"
42 42 #include "memory/referencePolicy.hpp"
43 43 #include "memory/referenceProcessor.hpp"
44 44 #include "oops/oop.inline.hpp"
45 45 #include "runtime/biasedLocking.hpp"
46 46 #include "runtime/fprofiler.hpp"
47 47 #include "runtime/safepoint.hpp"
48 48 #include "runtime/vmThread.hpp"
49 49 #include "services/management.hpp"
50 50 #include "services/memoryService.hpp"
51 51 #include "utilities/events.hpp"
52 52 #include "utilities/stack.inline.hpp"
53 53
54 54 elapsedTimer PSMarkSweep::_accumulated_time;
55 55 unsigned int PSMarkSweep::_total_invocations = 0;
56 56 jlong PSMarkSweep::_time_of_last_gc = 0;
57 57 CollectorCounters* PSMarkSweep::_counters = NULL;
58 58
59 59 void PSMarkSweep::initialize() {
60 60 MemRegion mr = Universe::heap()->reserved_region();
61 61 _ref_processor = new ReferenceProcessor(mr); // a vanilla ref proc
62 62 _counters = new CollectorCounters("PSMarkSweep", 1);
63 63 }
64 64
65 65 // This method contains all heap specific policy for invoking mark sweep.
66 66 // PSMarkSweep::invoke_no_policy() will only attempt to mark-sweep-compact
67 67 // the heap. It will do nothing further. If we need to bail out for policy
68 68 // reasons, scavenge before full gc, or any other specialized behavior, it
69 69 // needs to be added here.
70 70 //
71 71 // Note that this method should only be called from the vm_thread while
72 72 // at a safepoint!
73 73 //
74 74 // Note that the all_soft_refs_clear flag in the collector policy
75 75 // may be true because this method can be called without intervening
76 76 // activity. For example when the heap space is tight and full measure
77 77 // are being taken to free space.
78 78
79 79 void PSMarkSweep::invoke(bool maximum_heap_compaction) {
80 80 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
81 81 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
82 82 assert(!Universe::heap()->is_gc_active(), "not reentrant");
83 83
84 84 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
85 85 GCCause::Cause gc_cause = heap->gc_cause();
86 86 PSAdaptiveSizePolicy* policy = heap->size_policy();
87 87 IsGCActiveMark mark;
88 88
89 89 if (ScavengeBeforeFullGC) {
90 90 PSScavenge::invoke_no_policy();
91 91 }
92 92
93 93 const bool clear_all_soft_refs =
94 94 heap->collector_policy()->should_clear_all_soft_refs();
95 95
96 96 int count = (maximum_heap_compaction)?1:MarkSweepAlwaysCompactCount;
97 97 IntFlagSetting flag_setting(MarkSweepAlwaysCompactCount, count);
98 98 PSMarkSweep::invoke_no_policy(clear_all_soft_refs || maximum_heap_compaction);
99 99 }
100 100
101 101 // This method contains no policy. You should probably
102 102 // be calling invoke() instead.
103 103 void PSMarkSweep::invoke_no_policy(bool clear_all_softrefs) {
104 104 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
105 105 assert(ref_processor() != NULL, "Sanity");
106 106
107 107 if (GC_locker::check_active_before_gc()) {
108 108 return;
109 109 }
110 110
111 111 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
112 112 GCCause::Cause gc_cause = heap->gc_cause();
113 113 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
114 114 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
115 115
116 116 // The scope of casr should end after code that can change
117 117 // CollectorPolicy::_should_clear_all_soft_refs.
118 118 ClearedAllSoftRefs casr(clear_all_softrefs, heap->collector_policy());
119 119
120 120 PSYoungGen* young_gen = heap->young_gen();
121 121 PSOldGen* old_gen = heap->old_gen();
122 122 PSPermGen* perm_gen = heap->perm_gen();
123 123
124 124 // Increment the invocation count
125 125 heap->increment_total_collections(true /* full */);
126 126
127 127 // Save information needed to minimize mangling
128 128 heap->record_gen_tops_before_GC();
129 129
130 130 // We need to track unique mark sweep invocations as well.
131 131 _total_invocations++;
132 132
133 133 AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
134 134
135 135 if (PrintHeapAtGC) {
136 136 Universe::print_heap_before_gc();
137 137 }
138 138
139 139 // Fill in TLABs
140 140 heap->accumulate_statistics_all_tlabs();
141 141 heap->ensure_parsability(true); // retire TLABs
142 142
143 143 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
144 144 HandleMark hm; // Discard invalid handles created during verification
145 145 gclog_or_tty->print(" VerifyBeforeGC:");
146 146 Universe::verify(true);
147 147 }
148 148
149 149 // Verify object start arrays
150 150 if (VerifyObjectStartArray &&
151 151 VerifyBeforeGC) {
152 152 old_gen->verify_object_start_array();
153 153 perm_gen->verify_object_start_array();
154 154 }
155 155
156 156 heap->pre_full_gc_dump();
157 157
158 158 // Filled in below to track the state of the young gen after the collection.
159 159 bool eden_empty;
160 160 bool survivors_empty;
161 161 bool young_gen_empty;
162 162
163 163 {
164 164 HandleMark hm;
165 165 const bool is_system_gc = gc_cause == GCCause::_java_lang_system_gc;
166 166 // This is useful for debugging but don't change the output the
167 167 // the customer sees.
168 168 const char* gc_cause_str = "Full GC";
169 169 if (is_system_gc && PrintGCDetails) {
170 170 gc_cause_str = "Full GC (System)";
171 171 }
172 172 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
173 173 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
174 174 TraceTime t1(gc_cause_str, PrintGC, !PrintGCDetails, gclog_or_tty);
175 175 TraceCollectorStats tcs(counters());
176 176 TraceMemoryManagerStats tms(true /* Full GC */,gc_cause);
177 177
178 178 if (TraceGen1Time) accumulated_time()->start();
179 179
180 180 // Let the size policy know we're starting
181 181 size_policy->major_collection_begin();
182 182
183 183 // When collecting the permanent generation methodOops may be moving,
184 184 // so we either have to flush all bcp data or convert it into bci.
185 185 CodeCache::gc_prologue();
186 186 Threads::gc_prologue();
187 187 BiasedLocking::preserve_marks();
188 188
189 189 // Capture heap size before collection for printing.
190 190 size_t prev_used = heap->used();
191 191
192 192 // Capture perm gen size before collection for sizing.
193 193 size_t perm_gen_prev_used = perm_gen->used_in_bytes();
194 194
195 195 // For PrintGCDetails
196 196 size_t old_gen_prev_used = old_gen->used_in_bytes();
197 197 size_t young_gen_prev_used = young_gen->used_in_bytes();
198 198
199 199 allocate_stacks();
200 200
201 201 COMPILER2_PRESENT(DerivedPointerTable::clear());
202 202
203 203 ref_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
204 204 ref_processor()->setup_policy(clear_all_softrefs);
205 205
206 206 mark_sweep_phase1(clear_all_softrefs);
207 207
208 208 mark_sweep_phase2();
209 209
210 210 // Don't add any more derived pointers during phase3
211 211 COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
212 212 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
213 213
214 214 mark_sweep_phase3();
215 215
216 216 mark_sweep_phase4();
217 217
218 218 restore_marks();
219 219
220 220 deallocate_stacks();
221 221
222 222 if (ZapUnusedHeapArea) {
223 223 // Do a complete mangle (top to end) because the usage for
224 224 // scratch does not maintain a top pointer.
225 225 young_gen->to_space()->mangle_unused_area_complete();
226 226 }
227 227
228 228 eden_empty = young_gen->eden_space()->is_empty();
229 229 if (!eden_empty) {
230 230 eden_empty = absorb_live_data_from_eden(size_policy, young_gen, old_gen);
231 231 }
232 232
233 233 // Update heap occupancy information which is used as
234 234 // input to soft ref clearing policy at the next gc.
235 235 Universe::update_heap_info_at_gc();
236 236
237 237 survivors_empty = young_gen->from_space()->is_empty() &&
238 238 young_gen->to_space()->is_empty();
239 239 young_gen_empty = eden_empty && survivors_empty;
240 240
241 241 BarrierSet* bs = heap->barrier_set();
242 242 if (bs->is_a(BarrierSet::ModRef)) {
243 243 ModRefBarrierSet* modBS = (ModRefBarrierSet*)bs;
244 244 MemRegion old_mr = heap->old_gen()->reserved();
245 245 MemRegion perm_mr = heap->perm_gen()->reserved();
246 246 assert(perm_mr.end() <= old_mr.start(), "Generations out of order");
247 247
248 248 if (young_gen_empty) {
249 249 modBS->clear(MemRegion(perm_mr.start(), old_mr.end()));
250 250 } else {
251 251 modBS->invalidate(MemRegion(perm_mr.start(), old_mr.end()));
252 252 }
253 253 }
254 254
255 255 BiasedLocking::restore_marks();
256 256 Threads::gc_epilogue();
257 257 CodeCache::gc_epilogue();
258 258 JvmtiExport::gc_epilogue();
259 259
260 260 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
261 261
262 262 ref_processor()->enqueue_discovered_references(NULL);
263 263
264 264 // Update time of last GC
265 265 reset_millis_since_last_gc();
266 266
267 267 // Let the size policy know we're done
268 268 size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
269 269
270 270 if (UseAdaptiveSizePolicy) {
271 271
272 272 if (PrintAdaptiveSizePolicy) {
273 273 gclog_or_tty->print("AdaptiveSizeStart: ");
274 274 gclog_or_tty->stamp();
275 275 gclog_or_tty->print_cr(" collection: %d ",
276 276 heap->total_collections());
277 277 if (Verbose) {
278 278 gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d"
279 279 " perm_gen_capacity: %d ",
280 280 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes(),
281 281 perm_gen->capacity_in_bytes());
282 282 }
283 283 }
284 284
285 285 // Don't check if the size_policy is ready here. Let
286 286 // the size_policy check that internally.
287 287 if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
288 288 ((gc_cause != GCCause::_java_lang_system_gc) ||
289 289 UseAdaptiveSizePolicyWithSystemGC)) {
290 290 // Calculate optimal free space amounts
291 291 assert(young_gen->max_size() >
292 292 young_gen->from_space()->capacity_in_bytes() +
293 293 young_gen->to_space()->capacity_in_bytes(),
294 294 "Sizes of space in young gen are out-of-bounds");
295 295 size_t max_eden_size = young_gen->max_size() -
296 296 young_gen->from_space()->capacity_in_bytes() -
297 297 young_gen->to_space()->capacity_in_bytes();
298 298 size_policy->compute_generation_free_space(young_gen->used_in_bytes(),
299 299 young_gen->eden_space()->used_in_bytes(),
300 300 old_gen->used_in_bytes(),
301 301 perm_gen->used_in_bytes(),
302 302 young_gen->eden_space()->capacity_in_bytes(),
303 303 old_gen->max_gen_size(),
304 304 max_eden_size,
305 305 true /* full gc*/,
306 306 gc_cause,
307 307 heap->collector_policy());
308 308
309 309 heap->resize_old_gen(size_policy->calculated_old_free_size_in_bytes());
310 310
311 311 // Don't resize the young generation at an major collection. A
312 312 // desired young generation size may have been calculated but
313 313 // resizing the young generation complicates the code because the
314 314 // resizing of the old generation may have moved the boundary
315 315 // between the young generation and the old generation. Let the
316 316 // young generation resizing happen at the minor collections.
317 317 }
318 318 if (PrintAdaptiveSizePolicy) {
319 319 gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
320 320 heap->total_collections());
321 321 }
322 322 }
323 323
324 324 if (UsePerfData) {
325 325 heap->gc_policy_counters()->update_counters();
326 326 heap->gc_policy_counters()->update_old_capacity(
327 327 old_gen->capacity_in_bytes());
328 328 heap->gc_policy_counters()->update_young_capacity(
329 329 young_gen->capacity_in_bytes());
330 330 }
331 331
332 332 heap->resize_all_tlabs();
333 333
334 334 // We collected the perm gen, so we'll resize it here.
335 335 perm_gen->compute_new_size(perm_gen_prev_used);
336 336
337 337 if (TraceGen1Time) accumulated_time()->stop();
338 338
339 339 if (PrintGC) {
340 340 if (PrintGCDetails) {
341 341 // Don't print a GC timestamp here. This is after the GC so
342 342 // would be confusing.
343 343 young_gen->print_used_change(young_gen_prev_used);
344 344 old_gen->print_used_change(old_gen_prev_used);
345 345 }
346 346 heap->print_heap_change(prev_used);
347 347 // Do perm gen after heap becase prev_used does
348 348 // not include the perm gen (done this way in the other
349 349 // collectors).
350 350 if (PrintGCDetails) {
351 351 perm_gen->print_used_change(perm_gen_prev_used);
352 352 }
353 353 }
354 354
355 355 // Track memory usage and detect low memory
356 356 MemoryService::track_memory_usage();
357 357 heap->update_counters();
358 358 }
359 359
360 360 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
361 361 HandleMark hm; // Discard invalid handles created during verification
362 362 gclog_or_tty->print(" VerifyAfterGC:");
363 363 Universe::verify(false);
364 364 }
365 365
366 366 // Re-verify object start arrays
367 367 if (VerifyObjectStartArray &&
368 368 VerifyAfterGC) {
369 369 old_gen->verify_object_start_array();
370 370 perm_gen->verify_object_start_array();
371 371 }
372 372
373 373 if (ZapUnusedHeapArea) {
374 374 old_gen->object_space()->check_mangled_unused_area_complete();
375 375 perm_gen->object_space()->check_mangled_unused_area_complete();
376 376 }
377 377
378 378 NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
379 379
380 380 if (PrintHeapAtGC) {
381 381 Universe::print_heap_after_gc();
382 382 }
383 383
384 384 heap->post_full_gc_dump();
385 385
386 386 #ifdef TRACESPINNING
387 387 ParallelTaskTerminator::print_termination_counts();
388 388 #endif
389 389 }
390 390
391 391 bool PSMarkSweep::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
392 392 PSYoungGen* young_gen,
393 393 PSOldGen* old_gen) {
394 394 MutableSpace* const eden_space = young_gen->eden_space();
395 395 assert(!eden_space->is_empty(), "eden must be non-empty");
396 396 assert(young_gen->virtual_space()->alignment() ==
397 397 old_gen->virtual_space()->alignment(), "alignments do not match");
398 398
399 399 if (!(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary)) {
400 400 return false;
401 401 }
402 402
403 403 // Both generations must be completely committed.
404 404 if (young_gen->virtual_space()->uncommitted_size() != 0) {
405 405 return false;
406 406 }
407 407 if (old_gen->virtual_space()->uncommitted_size() != 0) {
408 408 return false;
409 409 }
410 410
411 411 // Figure out how much to take from eden. Include the average amount promoted
412 412 // in the total; otherwise the next young gen GC will simply bail out to a
413 413 // full GC.
414 414 const size_t alignment = old_gen->virtual_space()->alignment();
415 415 const size_t eden_used = eden_space->used_in_bytes();
416 416 const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average();
417 417 const size_t absorb_size = align_size_up(eden_used + promoted, alignment);
418 418 const size_t eden_capacity = eden_space->capacity_in_bytes();
419 419
420 420 if (absorb_size >= eden_capacity) {
421 421 return false; // Must leave some space in eden.
422 422 }
423 423
424 424 const size_t new_young_size = young_gen->capacity_in_bytes() - absorb_size;
425 425 if (new_young_size < young_gen->min_gen_size()) {
426 426 return false; // Respect young gen minimum size.
427 427 }
428 428
429 429 if (TraceAdaptiveGCBoundary && Verbose) {
430 430 gclog_or_tty->print(" absorbing " SIZE_FORMAT "K: "
431 431 "eden " SIZE_FORMAT "K->" SIZE_FORMAT "K "
432 432 "from " SIZE_FORMAT "K, to " SIZE_FORMAT "K "
433 433 "young_gen " SIZE_FORMAT "K->" SIZE_FORMAT "K ",
434 434 absorb_size / K,
435 435 eden_capacity / K, (eden_capacity - absorb_size) / K,
436 436 young_gen->from_space()->used_in_bytes() / K,
437 437 young_gen->to_space()->used_in_bytes() / K,
438 438 young_gen->capacity_in_bytes() / K, new_young_size / K);
439 439 }
440 440
441 441 // Fill the unused part of the old gen.
442 442 MutableSpace* const old_space = old_gen->object_space();
443 443 HeapWord* const unused_start = old_space->top();
444 444 size_t const unused_words = pointer_delta(old_space->end(), unused_start);
445 445
446 446 if (unused_words > 0) {
447 447 if (unused_words < CollectedHeap::min_fill_size()) {
448 448 return false; // If the old gen cannot be filled, must give up.
449 449 }
450 450 CollectedHeap::fill_with_objects(unused_start, unused_words);
451 451 }
452 452
453 453 // Take the live data from eden and set both top and end in the old gen to
454 454 // eden top. (Need to set end because reset_after_change() mangles the region
455 455 // from end to virtual_space->high() in debug builds).
456 456 HeapWord* const new_top = eden_space->top();
457 457 old_gen->virtual_space()->expand_into(young_gen->virtual_space(),
458 458 absorb_size);
459 459 young_gen->reset_after_change();
460 460 old_space->set_top(new_top);
461 461 old_space->set_end(new_top);
462 462 old_gen->reset_after_change();
463 463
464 464 // Update the object start array for the filler object and the data from eden.
465 465 ObjectStartArray* const start_array = old_gen->start_array();
466 466 for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) {
467 467 start_array->allocate_block(p);
468 468 }
469 469
470 470 // Could update the promoted average here, but it is not typically updated at
471 471 // full GCs and the value to use is unclear. Something like
472 472 //
473 473 // cur_promoted_avg + absorb_size / number_of_scavenges_since_last_full_gc.
474 474
475 475 size_policy->set_bytes_absorbed_from_eden(absorb_size);
476 476 return true;
477 477 }
478 478
479 479 void PSMarkSweep::allocate_stacks() {
480 480 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
481 481 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
482 482
483 483 PSYoungGen* young_gen = heap->young_gen();
484 484
485 485 MutableSpace* to_space = young_gen->to_space();
486 486 _preserved_marks = (PreservedMark*)to_space->top();
487 487 _preserved_count = 0;
488 488
489 489 // We want to calculate the size in bytes first.
490 490 _preserved_count_max = pointer_delta(to_space->end(), to_space->top(), sizeof(jbyte));
491 491 // Now divide by the size of a PreservedMark
492 492 _preserved_count_max /= sizeof(PreservedMark);
493 493 }
494 494
495 495
496 496 void PSMarkSweep::deallocate_stacks() {
497 497 _preserved_mark_stack.clear(true);
498 498 _preserved_oop_stack.clear(true);
499 499 _marking_stack.clear();
500 500 _objarray_stack.clear(true);
501 501 _revisit_klass_stack.clear(true);
502 502 _revisit_mdo_stack.clear(true);
503 503 }
504 504
505 505 void PSMarkSweep::mark_sweep_phase1(bool clear_all_softrefs) {
506 506 // Recursively traverse all live objects and mark them
507 507 EventMark m("1 mark object");
508 508 TraceTime tm("phase 1", PrintGCDetails && Verbose, true, gclog_or_tty);
509 509 trace(" 1");
510 510
511 511 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
512 512 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
513 513
514 514 // General strong roots.
515 515 {
516 516 ParallelScavengeHeap::ParStrongRootsScope psrs;
517 517 Universe::oops_do(mark_and_push_closure());
518 518 JNIHandles::oops_do(mark_and_push_closure()); // Global (strong) JNI handles
519 519 CodeBlobToOopClosure each_active_code_blob(mark_and_push_closure(), /*do_marking=*/ true);
520 520 Threads::oops_do(mark_and_push_closure(), &each_active_code_blob);
521 521 ObjectSynchronizer::oops_do(mark_and_push_closure());
522 522 FlatProfiler::oops_do(mark_and_push_closure());
523 523 Management::oops_do(mark_and_push_closure());
524 524 JvmtiExport::oops_do(mark_and_push_closure());
525 525 SystemDictionary::always_strong_oops_do(mark_and_push_closure());
526 526 // Do not treat nmethods as strong roots for mark/sweep, since we can unload them.
527 527 //CodeCache::scavenge_root_nmethods_do(CodeBlobToOopClosure(mark_and_push_closure()));
528 528 }
529 529
530 530 // Flush marking stack.
531 531 follow_stack();
532 532
533 533 // Process reference objects found during marking
534 534 {
535 535 ref_processor()->setup_policy(clear_all_softrefs);
536 536 ref_processor()->process_discovered_references(
537 537 is_alive_closure(), mark_and_push_closure(), follow_stack_closure(), NULL);
538 538 }
539 539
540 540 // Follow system dictionary roots and unload classes
541 541 bool purged_class = SystemDictionary::do_unloading(is_alive_closure());
542 542
543 543 // Follow code cache roots
544 544 CodeCache::do_unloading(is_alive_closure(), mark_and_push_closure(),
545 545 purged_class);
546 546 follow_stack(); // Flush marking stack
547 547
548 548 // Update subklass/sibling/implementor links of live klasses
549 549 follow_weak_klass_links();
550 550 assert(_marking_stack.is_empty(), "just drained");
551 551
552 552 // Visit memoized mdo's and clear unmarked weak refs
553 553 follow_mdo_weak_refs();
554 554 assert(_marking_stack.is_empty(), "just drained");
555 555
556 556 // Visit interned string tables and delete unmarked oops
557 557 StringTable::unlink(is_alive_closure());
558 558 // Clean up unreferenced symbols in symbol table.
559 559 SymbolTable::unlink();
560 560
561 561 assert(_marking_stack.is_empty(), "stack should be empty by now");
562 562 }
563 563
564 564
565 565 void PSMarkSweep::mark_sweep_phase2() {
566 566 EventMark m("2 compute new addresses");
567 567 TraceTime tm("phase 2", PrintGCDetails && Verbose, true, gclog_or_tty);
568 568 trace("2");
569 569
570 570 // Now all live objects are marked, compute the new object addresses.
571 571
572 572 // It is imperative that we traverse perm_gen LAST. If dead space is
573 573 // allowed a range of dead object may get overwritten by a dead int
574 574 // array. If perm_gen is not traversed last a klassOop may get
575 575 // overwritten. This is fine since it is dead, but if the class has dead
576 576 // instances we have to skip them, and in order to find their size we
577 577 // need the klassOop!
578 578 //
579 579 // It is not required that we traverse spaces in the same order in
580 580 // phase2, phase3 and phase4, but the ValidateMarkSweep live oops
581 581 // tracking expects us to do so. See comment under phase4.
582 582
583 583 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
584 584 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
585 585
586 586 PSOldGen* old_gen = heap->old_gen();
587 587 PSPermGen* perm_gen = heap->perm_gen();
588 588
589 589 // Begin compacting into the old gen
590 590 PSMarkSweepDecorator::set_destination_decorator_tenured();
591 591
592 592 // This will also compact the young gen spaces.
593 593 old_gen->precompact();
594 594
595 595 // Compact the perm gen into the perm gen
596 596 PSMarkSweepDecorator::set_destination_decorator_perm_gen();
597 597
598 598 perm_gen->precompact();
599 599 }
600 600
601 601 // This should be moved to the shared markSweep code!
602 602 class PSAlwaysTrueClosure: public BoolObjectClosure {
603 603 public:
604 604 void do_object(oop p) { ShouldNotReachHere(); }
605 605 bool do_object_b(oop p) { return true; }
606 606 };
607 607 static PSAlwaysTrueClosure always_true;
608 608
609 609 void PSMarkSweep::mark_sweep_phase3() {
610 610 // Adjust the pointers to reflect the new locations
611 611 EventMark m("3 adjust pointers");
612 612 TraceTime tm("phase 3", PrintGCDetails && Verbose, true, gclog_or_tty);
613 613 trace("3");
614 614
615 615 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
616 616 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
617 617
618 618 PSYoungGen* young_gen = heap->young_gen();
619 619 PSOldGen* old_gen = heap->old_gen();
620 620 PSPermGen* perm_gen = heap->perm_gen();
621 621
622 622 // General strong roots.
623 623 Universe::oops_do(adjust_root_pointer_closure());
624 624 JNIHandles::oops_do(adjust_root_pointer_closure()); // Global (strong) JNI handles
625 625 Threads::oops_do(adjust_root_pointer_closure(), NULL);
626 626 ObjectSynchronizer::oops_do(adjust_root_pointer_closure());
627 627 FlatProfiler::oops_do(adjust_root_pointer_closure());
628 628 Management::oops_do(adjust_root_pointer_closure());
629 629 JvmtiExport::oops_do(adjust_root_pointer_closure());
630 630 // SO_AllClasses
631 631 SystemDictionary::oops_do(adjust_root_pointer_closure());
632 632 //CodeCache::scavenge_root_nmethods_oops_do(adjust_root_pointer_closure());
633 633
634 634 // Now adjust pointers in remaining weak roots. (All of which should
635 635 // have been cleared if they pointed to non-surviving objects.)
636 636 // Global (weak) JNI handles
637 637 JNIHandles::weak_oops_do(&always_true, adjust_root_pointer_closure());
638 638
639 639 CodeCache::oops_do(adjust_pointer_closure());
640 640 StringTable::oops_do(adjust_root_pointer_closure());
641 641 ref_processor()->weak_oops_do(adjust_root_pointer_closure());
642 642 PSScavenge::reference_processor()->weak_oops_do(adjust_root_pointer_closure());
643 643
644 644 adjust_marks();
645 645
646 646 young_gen->adjust_pointers();
647 647 old_gen->adjust_pointers();
648 648 perm_gen->adjust_pointers();
649 649 }
650 650
651 651 void PSMarkSweep::mark_sweep_phase4() {
652 652 EventMark m("4 compact heap");
653 653 TraceTime tm("phase 4", PrintGCDetails && Verbose, true, gclog_or_tty);
654 654 trace("4");
655 655
656 656 // All pointers are now adjusted, move objects accordingly
657 657
658 658 // It is imperative that we traverse perm_gen first in phase4. All
659 659 // classes must be allocated earlier than their instances, and traversing
660 660 // perm_gen first makes sure that all klassOops have moved to their new
661 661 // location before any instance does a dispatch through it's klass!
662 662 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
663 663 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
664 664
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665 665 PSYoungGen* young_gen = heap->young_gen();
666 666 PSOldGen* old_gen = heap->old_gen();
667 667 PSPermGen* perm_gen = heap->perm_gen();
668 668
669 669 perm_gen->compact();
670 670 old_gen->compact();
671 671 young_gen->compact();
672 672 }
673 673
674 674 jlong PSMarkSweep::millis_since_last_gc() {
675 - jlong ret_val = os::javaTimeMillis() - _time_of_last_gc;
675 + // os::javaTimeMillis() does not guarantee monotonicity.
676 + jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
677 + jlong ret_val = now - _time_of_last_gc;
676 678 // XXX See note in genCollectedHeap::millis_since_last_gc().
677 679 if (ret_val < 0) {
678 - NOT_PRODUCT(warning("time warp: %d", ret_val);)
680 + NOT_PRODUCT(warning("time warp: "INT64_FORMAT, ret_val);)
679 681 return 0;
680 682 }
681 683 return ret_val;
682 684 }
683 685
684 686 void PSMarkSweep::reset_millis_since_last_gc() {
685 - _time_of_last_gc = os::javaTimeMillis();
687 + // os::javaTimeMillis() does not guarantee monotonicity.
688 + _time_of_last_gc = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
686 689 }
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