1 /*
2 * Copyright (c) 2001, 2010, 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_implementation/parallelScavenge/adjoiningGenerations.hpp"
27 #include "gc_implementation/parallelScavenge/adjoiningVirtualSpaces.hpp"
28 #include "gc_implementation/parallelScavenge/cardTableExtension.hpp"
29 #include "gc_implementation/parallelScavenge/gcTaskManager.hpp"
30 #include "gc_implementation/parallelScavenge/generationSizer.hpp"
31 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.inline.hpp"
32 #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp"
33 #include "gc_implementation/parallelScavenge/psMarkSweep.hpp"
34 #include "gc_implementation/parallelScavenge/psParallelCompact.hpp"
35 #include "gc_implementation/parallelScavenge/psPromotionManager.hpp"
36 #include "gc_implementation/parallelScavenge/psScavenge.hpp"
37 #include "gc_implementation/parallelScavenge/vmPSOperations.hpp"
38 #include "memory/gcLocker.inline.hpp"
39 #include "oops/oop.inline.hpp"
40 #include "runtime/handles.inline.hpp"
41 #include "runtime/java.hpp"
42 #include "runtime/vmThread.hpp"
43 #include "utilities/vmError.hpp"
44
45 PSYoungGen* ParallelScavengeHeap::_young_gen = NULL;
46 PSOldGen* ParallelScavengeHeap::_old_gen = NULL;
47 PSPermGen* ParallelScavengeHeap::_perm_gen = NULL;
48 PSAdaptiveSizePolicy* ParallelScavengeHeap::_size_policy = NULL;
49 PSGCAdaptivePolicyCounters* ParallelScavengeHeap::_gc_policy_counters = NULL;
50 ParallelScavengeHeap* ParallelScavengeHeap::_psh = NULL;
51 GCTaskManager* ParallelScavengeHeap::_gc_task_manager = NULL;
52
53 static void trace_gen_sizes(const char* const str,
54 size_t pg_min, size_t pg_max,
55 size_t og_min, size_t og_max,
56 size_t yg_min, size_t yg_max)
57 {
58 if (TracePageSizes) {
59 tty->print_cr("%s: " SIZE_FORMAT "," SIZE_FORMAT " "
60 SIZE_FORMAT "," SIZE_FORMAT " "
61 SIZE_FORMAT "," SIZE_FORMAT " "
62 SIZE_FORMAT,
63 str, pg_min / K, pg_max / K,
64 og_min / K, og_max / K,
65 yg_min / K, yg_max / K,
66 (pg_max + og_max + yg_max) / K);
67 }
68 }
69
70 jint ParallelScavengeHeap::initialize() {
71 CollectedHeap::pre_initialize();
72
73 // Cannot be initialized until after the flags are parsed
74 // GenerationSizer flag_parser;
75 _collector_policy = new GenerationSizer();
76
77 size_t yg_min_size = _collector_policy->min_young_gen_size();
78 size_t yg_max_size = _collector_policy->max_young_gen_size();
79 size_t og_min_size = _collector_policy->min_old_gen_size();
80 size_t og_max_size = _collector_policy->max_old_gen_size();
81 // Why isn't there a min_perm_gen_size()?
82 size_t pg_min_size = _collector_policy->perm_gen_size();
83 size_t pg_max_size = _collector_policy->max_perm_gen_size();
84
85 trace_gen_sizes("ps heap raw",
86 pg_min_size, pg_max_size,
87 og_min_size, og_max_size,
88 yg_min_size, yg_max_size);
89
90 // The ReservedSpace ctor used below requires that the page size for the perm
91 // gen is <= the page size for the rest of the heap (young + old gens).
92 const size_t og_page_sz = os::page_size_for_region(yg_min_size + og_min_size,
93 yg_max_size + og_max_size,
94 8);
95 const size_t pg_page_sz = MIN2(os::page_size_for_region(pg_min_size,
96 pg_max_size, 16),
97 og_page_sz);
98
99 const size_t pg_align = set_alignment(_perm_gen_alignment, pg_page_sz);
100 const size_t og_align = set_alignment(_old_gen_alignment, og_page_sz);
101 const size_t yg_align = set_alignment(_young_gen_alignment, og_page_sz);
102
103 // Update sizes to reflect the selected page size(s).
104 //
105 // NEEDS_CLEANUP. The default TwoGenerationCollectorPolicy uses NewRatio; it
106 // should check UseAdaptiveSizePolicy. Changes from generationSizer could
107 // move to the common code.
108 yg_min_size = align_size_up(yg_min_size, yg_align);
109 yg_max_size = align_size_up(yg_max_size, yg_align);
110 size_t yg_cur_size =
111 align_size_up(_collector_policy->young_gen_size(), yg_align);
112 yg_cur_size = MAX2(yg_cur_size, yg_min_size);
113
114 og_min_size = align_size_up(og_min_size, og_align);
115 og_max_size = align_size_up(og_max_size, og_align);
116 size_t og_cur_size =
117 align_size_up(_collector_policy->old_gen_size(), og_align);
118 og_cur_size = MAX2(og_cur_size, og_min_size);
119
120 pg_min_size = align_size_up(pg_min_size, pg_align);
121 pg_max_size = align_size_up(pg_max_size, pg_align);
122 size_t pg_cur_size = pg_min_size;
123
124 trace_gen_sizes("ps heap rnd",
125 pg_min_size, pg_max_size,
126 og_min_size, og_max_size,
127 yg_min_size, yg_max_size);
128
129 const size_t total_reserved = pg_max_size + og_max_size + yg_max_size;
130 char* addr = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop);
131
132 // The main part of the heap (old gen + young gen) can often use a larger page
133 // size than is needed or wanted for the perm gen. Use the "compound
134 // alignment" ReservedSpace ctor to avoid having to use the same page size for
135 // all gens.
136
137 ReservedHeapSpace heap_rs(pg_max_size, pg_align, og_max_size + yg_max_size,
138 og_align, addr);
139
140 if (UseCompressedOops) {
141 if (addr != NULL && !heap_rs.is_reserved()) {
142 // Failed to reserve at specified address - the requested memory
143 // region is taken already, for example, by 'java' launcher.
144 // Try again to reserver heap higher.
145 addr = Universe::preferred_heap_base(total_reserved, Universe::ZeroBasedNarrowOop);
146 ReservedHeapSpace heap_rs0(pg_max_size, pg_align, og_max_size + yg_max_size,
147 og_align, addr);
148 if (addr != NULL && !heap_rs0.is_reserved()) {
149 // Failed to reserve at specified address again - give up.
150 addr = Universe::preferred_heap_base(total_reserved, Universe::HeapBasedNarrowOop);
151 assert(addr == NULL, "");
152 ReservedHeapSpace heap_rs1(pg_max_size, pg_align, og_max_size + yg_max_size,
153 og_align, addr);
154 heap_rs = heap_rs1;
155 } else {
156 heap_rs = heap_rs0;
157 }
158 }
159 }
160
161 os::trace_page_sizes("ps perm", pg_min_size, pg_max_size, pg_page_sz,
162 heap_rs.base(), pg_max_size);
163 os::trace_page_sizes("ps main", og_min_size + yg_min_size,
164 og_max_size + yg_max_size, og_page_sz,
165 heap_rs.base() + pg_max_size,
166 heap_rs.size() - pg_max_size);
167 if (!heap_rs.is_reserved()) {
168 vm_shutdown_during_initialization(
169 "Could not reserve enough space for object heap");
170 return JNI_ENOMEM;
171 }
172
173 _reserved = MemRegion((HeapWord*)heap_rs.base(),
174 (HeapWord*)(heap_rs.base() + heap_rs.size()));
175
176 CardTableExtension* const barrier_set = new CardTableExtension(_reserved, 3);
177 _barrier_set = barrier_set;
178 oopDesc::set_bs(_barrier_set);
179 if (_barrier_set == NULL) {
180 vm_shutdown_during_initialization(
181 "Could not reserve enough space for barrier set");
182 return JNI_ENOMEM;
183 }
184
185 // Initial young gen size is 4 Mb
186 //
187 // XXX - what about flag_parser.young_gen_size()?
188 const size_t init_young_size = align_size_up(4 * M, yg_align);
189 yg_cur_size = MAX2(MIN2(init_young_size, yg_max_size), yg_cur_size);
190
191 // Split the reserved space into perm gen and the main heap (everything else).
192 // The main heap uses a different alignment.
193 ReservedSpace perm_rs = heap_rs.first_part(pg_max_size);
194 ReservedSpace main_rs = heap_rs.last_part(pg_max_size, og_align);
195
196 // Make up the generations
197 // Calculate the maximum size that a generation can grow. This
198 // includes growth into the other generation. Note that the
199 // parameter _max_gen_size is kept as the maximum
200 // size of the generation as the boundaries currently stand.
201 // _max_gen_size is still used as that value.
202 double max_gc_pause_sec = ((double) MaxGCPauseMillis)/1000.0;
203 double max_gc_minor_pause_sec = ((double) MaxGCMinorPauseMillis)/1000.0;
204
205 _gens = new AdjoiningGenerations(main_rs,
206 og_cur_size,
207 og_min_size,
208 og_max_size,
209 yg_cur_size,
210 yg_min_size,
211 yg_max_size,
212 yg_align);
213
214 _old_gen = _gens->old_gen();
215 _young_gen = _gens->young_gen();
216
217 const size_t eden_capacity = _young_gen->eden_space()->capacity_in_bytes();
218 const size_t old_capacity = _old_gen->capacity_in_bytes();
219 const size_t initial_promo_size = MIN2(eden_capacity, old_capacity);
220 _size_policy =
221 new PSAdaptiveSizePolicy(eden_capacity,
222 initial_promo_size,
223 young_gen()->to_space()->capacity_in_bytes(),
224 intra_heap_alignment(),
225 max_gc_pause_sec,
226 max_gc_minor_pause_sec,
227 GCTimeRatio
228 );
229
230 _perm_gen = new PSPermGen(perm_rs,
231 pg_align,
232 pg_cur_size,
233 pg_cur_size,
234 pg_max_size,
235 "perm", 2);
236
237 assert(!UseAdaptiveGCBoundary ||
238 (old_gen()->virtual_space()->high_boundary() ==
239 young_gen()->virtual_space()->low_boundary()),
240 "Boundaries must meet");
241 // initialize the policy counters - 2 collectors, 3 generations
242 _gc_policy_counters =
243 new PSGCAdaptivePolicyCounters("ParScav:MSC", 2, 3, _size_policy);
244 _psh = this;
245
246 // Set up the GCTaskManager
247 _gc_task_manager = GCTaskManager::create(ParallelGCThreads);
248
249 if (UseParallelOldGC && !PSParallelCompact::initialize()) {
250 return JNI_ENOMEM;
251 }
252
253 return JNI_OK;
254 }
255
256 void ParallelScavengeHeap::post_initialize() {
257 // Need to init the tenuring threshold
258 PSScavenge::initialize();
259 if (UseParallelOldGC) {
260 PSParallelCompact::post_initialize();
261 } else {
262 PSMarkSweep::initialize();
263 }
264 PSPromotionManager::initialize();
265 }
266
267 void ParallelScavengeHeap::update_counters() {
268 young_gen()->update_counters();
269 old_gen()->update_counters();
270 perm_gen()->update_counters();
271 }
272
273 size_t ParallelScavengeHeap::capacity() const {
274 size_t value = young_gen()->capacity_in_bytes() + old_gen()->capacity_in_bytes();
275 return value;
276 }
277
278 size_t ParallelScavengeHeap::used() const {
279 size_t value = young_gen()->used_in_bytes() + old_gen()->used_in_bytes();
280 return value;
281 }
282
283 bool ParallelScavengeHeap::is_maximal_no_gc() const {
284 return old_gen()->is_maximal_no_gc() && young_gen()->is_maximal_no_gc();
285 }
286
287
288 size_t ParallelScavengeHeap::permanent_capacity() const {
289 return perm_gen()->capacity_in_bytes();
290 }
291
292 size_t ParallelScavengeHeap::permanent_used() const {
293 return perm_gen()->used_in_bytes();
294 }
295
296 size_t ParallelScavengeHeap::max_capacity() const {
297 size_t estimated = reserved_region().byte_size();
298 estimated -= perm_gen()->reserved().byte_size();
299 if (UseAdaptiveSizePolicy) {
300 estimated -= _size_policy->max_survivor_size(young_gen()->max_size());
301 } else {
302 estimated -= young_gen()->to_space()->capacity_in_bytes();
303 }
304 return MAX2(estimated, capacity());
305 }
306
307 bool ParallelScavengeHeap::is_in(const void* p) const {
308 if (young_gen()->is_in(p)) {
309 return true;
310 }
311
312 if (old_gen()->is_in(p)) {
313 return true;
314 }
315
316 if (perm_gen()->is_in(p)) {
317 return true;
318 }
319
320 return false;
321 }
322
323 bool ParallelScavengeHeap::is_in_reserved(const void* p) const {
324 if (young_gen()->is_in_reserved(p)) {
325 return true;
326 }
327
328 if (old_gen()->is_in_reserved(p)) {
329 return true;
330 }
331
332 if (perm_gen()->is_in_reserved(p)) {
333 return true;
334 }
335
336 return false;
337 }
338
339 // There are two levels of allocation policy here.
340 //
341 // When an allocation request fails, the requesting thread must invoke a VM
342 // operation, transfer control to the VM thread, and await the results of a
343 // garbage collection. That is quite expensive, and we should avoid doing it
344 // multiple times if possible.
345 //
346 // To accomplish this, we have a basic allocation policy, and also a
347 // failed allocation policy.
348 //
349 // The basic allocation policy controls how you allocate memory without
350 // attempting garbage collection. It is okay to grab locks and
351 // expand the heap, if that can be done without coming to a safepoint.
352 // It is likely that the basic allocation policy will not be very
353 // aggressive.
354 //
355 // The failed allocation policy is invoked from the VM thread after
356 // the basic allocation policy is unable to satisfy a mem_allocate
357 // request. This policy needs to cover the entire range of collection,
358 // heap expansion, and out-of-memory conditions. It should make every
359 // attempt to allocate the requested memory.
360
361 // Basic allocation policy. Should never be called at a safepoint, or
362 // from the VM thread.
363 //
364 // This method must handle cases where many mem_allocate requests fail
365 // simultaneously. When that happens, only one VM operation will succeed,
366 // and the rest will not be executed. For that reason, this method loops
367 // during failed allocation attempts. If the java heap becomes exhausted,
368 // we rely on the size_policy object to force a bail out.
369 HeapWord* ParallelScavengeHeap::mem_allocate(
370 size_t size,
371 bool is_noref,
372 bool is_tlab,
373 bool* gc_overhead_limit_was_exceeded) {
374 assert(!SafepointSynchronize::is_at_safepoint(), "should not be at safepoint");
375 assert(Thread::current() != (Thread*)VMThread::vm_thread(), "should not be in vm thread");
376 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
377
378 // In general gc_overhead_limit_was_exceeded should be false so
379 // set it so here and reset it to true only if the gc time
380 // limit is being exceeded as checked below.
381 *gc_overhead_limit_was_exceeded = false;
382
383 HeapWord* result = young_gen()->allocate(size, is_tlab);
384
385 uint loop_count = 0;
386 uint gc_count = 0;
387
388 while (result == NULL) {
389 // We don't want to have multiple collections for a single filled generation.
390 // To prevent this, each thread tracks the total_collections() value, and if
391 // the count has changed, does not do a new collection.
392 //
393 // The collection count must be read only while holding the heap lock. VM
394 // operations also hold the heap lock during collections. There is a lock
395 // contention case where thread A blocks waiting on the Heap_lock, while
396 // thread B is holding it doing a collection. When thread A gets the lock,
397 // the collection count has already changed. To prevent duplicate collections,
398 // The policy MUST attempt allocations during the same period it reads the
399 // total_collections() value!
400 {
401 MutexLocker ml(Heap_lock);
402 gc_count = Universe::heap()->total_collections();
403
404 result = young_gen()->allocate(size, is_tlab);
405
406 // (1) If the requested object is too large to easily fit in the
407 // young_gen, or
408 // (2) If GC is locked out via GCLocker, young gen is full and
409 // the need for a GC already signalled to GCLocker (done
410 // at a safepoint),
411 // ... then, rather than force a safepoint and (a potentially futile)
412 // collection (attempt) for each allocation, try allocation directly
413 // in old_gen. For case (2) above, we may in the future allow
414 // TLAB allocation directly in the old gen.
415 if (result != NULL) {
416 return result;
417 }
418 if (!is_tlab &&
419 size >= (young_gen()->eden_space()->capacity_in_words(Thread::current()) / 2)) {
420 result = old_gen()->allocate(size, is_tlab);
421 if (result != NULL) {
422 return result;
423 }
424 }
425 if (GC_locker::is_active_and_needs_gc()) {
426 // GC is locked out. If this is a TLAB allocation,
427 // return NULL; the requestor will retry allocation
428 // of an idividual object at a time.
429 if (is_tlab) {
430 return NULL;
431 }
432
433 // If this thread is not in a jni critical section, we stall
434 // the requestor until the critical section has cleared and
435 // GC allowed. When the critical section clears, a GC is
436 // initiated by the last thread exiting the critical section; so
437 // we retry the allocation sequence from the beginning of the loop,
438 // rather than causing more, now probably unnecessary, GC attempts.
439 JavaThread* jthr = JavaThread::current();
440 if (!jthr->in_critical()) {
441 MutexUnlocker mul(Heap_lock);
442 GC_locker::stall_until_clear();
443 continue;
444 } else {
445 if (CheckJNICalls) {
446 fatal("Possible deadlock due to allocating while"
447 " in jni critical section");
448 }
449 return NULL;
450 }
451 }
452 }
453
454 if (result == NULL) {
455
456 // Generate a VM operation
457 VM_ParallelGCFailedAllocation op(size, is_tlab, gc_count);
458 VMThread::execute(&op);
459
460 // Did the VM operation execute? If so, return the result directly.
461 // This prevents us from looping until time out on requests that can
462 // not be satisfied.
463 if (op.prologue_succeeded()) {
464 assert(Universe::heap()->is_in_or_null(op.result()),
465 "result not in heap");
466
467 // If GC was locked out during VM operation then retry allocation
468 // and/or stall as necessary.
469 if (op.gc_locked()) {
470 assert(op.result() == NULL, "must be NULL if gc_locked() is true");
471 continue; // retry and/or stall as necessary
472 }
473
474 // Exit the loop if the gc time limit has been exceeded.
475 // The allocation must have failed above ("result" guarding
476 // this path is NULL) and the most recent collection has exceeded the
477 // gc overhead limit (although enough may have been collected to
478 // satisfy the allocation). Exit the loop so that an out-of-memory
479 // will be thrown (return a NULL ignoring the contents of
480 // op.result()),
481 // but clear gc_overhead_limit_exceeded so that the next collection
482 // starts with a clean slate (i.e., forgets about previous overhead
483 // excesses). Fill op.result() with a filler object so that the
484 // heap remains parsable.
485 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
486 const bool softrefs_clear = collector_policy()->all_soft_refs_clear();
487 assert(!limit_exceeded || softrefs_clear, "Should have been cleared");
488 if (limit_exceeded && softrefs_clear) {
489 *gc_overhead_limit_was_exceeded = true;
490 size_policy()->set_gc_overhead_limit_exceeded(false);
491 if (PrintGCDetails && Verbose) {
492 gclog_or_tty->print_cr("ParallelScavengeHeap::mem_allocate: "
493 "return NULL because gc_overhead_limit_exceeded is set");
494 }
495 if (op.result() != NULL) {
496 CollectedHeap::fill_with_object(op.result(), size);
497 }
498 return NULL;
499 }
500
501 return op.result();
502 }
503 }
504
505 // The policy object will prevent us from looping forever. If the
506 // time spent in gc crosses a threshold, we will bail out.
507 loop_count++;
508 if ((result == NULL) && (QueuedAllocationWarningCount > 0) &&
509 (loop_count % QueuedAllocationWarningCount == 0)) {
510 warning("ParallelScavengeHeap::mem_allocate retries %d times \n\t"
511 " size=%d %s", loop_count, size, is_tlab ? "(TLAB)" : "");
512 }
513 }
514
515 return result;
516 }
517
518 // Failed allocation policy. Must be called from the VM thread, and
519 // only at a safepoint! Note that this method has policy for allocation
520 // flow, and NOT collection policy. So we do not check for gc collection
521 // time over limit here, that is the responsibility of the heap specific
522 // collection methods. This method decides where to attempt allocations,
523 // and when to attempt collections, but no collection specific policy.
524 HeapWord* ParallelScavengeHeap::failed_mem_allocate(size_t size, bool is_tlab) {
525 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
526 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
527 assert(!Universe::heap()->is_gc_active(), "not reentrant");
528 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
529
530 size_t mark_sweep_invocation_count = total_invocations();
531
532 // We assume (and assert!) that an allocation at this point will fail
533 // unless we collect.
534
535 // First level allocation failure, scavenge and allocate in young gen.
536 GCCauseSetter gccs(this, GCCause::_allocation_failure);
537 PSScavenge::invoke();
538 HeapWord* result = young_gen()->allocate(size, is_tlab);
539
540 // Second level allocation failure.
541 // Mark sweep and allocate in young generation.
542 if (result == NULL) {
543 // There is some chance the scavenge method decided to invoke mark_sweep.
544 // Don't mark sweep twice if so.
545 if (mark_sweep_invocation_count == total_invocations()) {
546 invoke_full_gc(false);
547 result = young_gen()->allocate(size, is_tlab);
548 }
549 }
550
551 // Third level allocation failure.
552 // After mark sweep and young generation allocation failure,
553 // allocate in old generation.
554 if (result == NULL && !is_tlab) {
555 result = old_gen()->allocate(size, is_tlab);
556 }
557
558 // Fourth level allocation failure. We're running out of memory.
559 // More complete mark sweep and allocate in young generation.
560 if (result == NULL) {
561 invoke_full_gc(true);
562 result = young_gen()->allocate(size, is_tlab);
563 }
564
565 // Fifth level allocation failure.
566 // After more complete mark sweep, allocate in old generation.
567 if (result == NULL && !is_tlab) {
568 result = old_gen()->allocate(size, is_tlab);
569 }
570
571 return result;
572 }
573
574 //
575 // This is the policy loop for allocating in the permanent generation.
576 // If the initial allocation fails, we create a vm operation which will
577 // cause a collection.
578 HeapWord* ParallelScavengeHeap::permanent_mem_allocate(size_t size) {
579 assert(!SafepointSynchronize::is_at_safepoint(), "should not be at safepoint");
580 assert(Thread::current() != (Thread*)VMThread::vm_thread(), "should not be in vm thread");
581 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
582
583 HeapWord* result;
584
585 uint loop_count = 0;
586 uint gc_count = 0;
587 uint full_gc_count = 0;
588
589 do {
590 // We don't want to have multiple collections for a single filled generation.
591 // To prevent this, each thread tracks the total_collections() value, and if
592 // the count has changed, does not do a new collection.
593 //
594 // The collection count must be read only while holding the heap lock. VM
595 // operations also hold the heap lock during collections. There is a lock
596 // contention case where thread A blocks waiting on the Heap_lock, while
597 // thread B is holding it doing a collection. When thread A gets the lock,
598 // the collection count has already changed. To prevent duplicate collections,
599 // The policy MUST attempt allocations during the same period it reads the
600 // total_collections() value!
601 {
602 MutexLocker ml(Heap_lock);
603 gc_count = Universe::heap()->total_collections();
604 full_gc_count = Universe::heap()->total_full_collections();
605
606 result = perm_gen()->allocate_permanent(size);
607
608 if (result != NULL) {
609 return result;
610 }
611
612 if (GC_locker::is_active_and_needs_gc()) {
613 // If this thread is not in a jni critical section, we stall
614 // the requestor until the critical section has cleared and
615 // GC allowed. When the critical section clears, a GC is
616 // initiated by the last thread exiting the critical section; so
617 // we retry the allocation sequence from the beginning of the loop,
618 // rather than causing more, now probably unnecessary, GC attempts.
619 JavaThread* jthr = JavaThread::current();
620 if (!jthr->in_critical()) {
621 MutexUnlocker mul(Heap_lock);
622 GC_locker::stall_until_clear();
623 continue;
624 } else {
625 if (CheckJNICalls) {
626 fatal("Possible deadlock due to allocating while"
627 " in jni critical section");
628 }
629 return NULL;
630 }
631 }
632 }
633
634 if (result == NULL) {
635
636 // Exit the loop if the gc time limit has been exceeded.
637 // The allocation must have failed above (result must be NULL),
638 // and the most recent collection must have exceeded the
639 // gc time limit. Exit the loop so that an out-of-memory
640 // will be thrown (returning a NULL will do that), but
641 // clear gc_overhead_limit_exceeded so that the next collection
642 // will succeeded if the applications decides to handle the
643 // out-of-memory and tries to go on.
644 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
645 if (limit_exceeded) {
646 size_policy()->set_gc_overhead_limit_exceeded(false);
647 if (PrintGCDetails && Verbose) {
648 gclog_or_tty->print_cr("ParallelScavengeHeap::permanent_mem_allocate:"
649 " return NULL because gc_overhead_limit_exceeded is set");
650 }
651 assert(result == NULL, "Allocation did not fail");
652 return NULL;
653 }
654
655 // Generate a VM operation
656 VM_ParallelGCFailedPermanentAllocation op(size, gc_count, full_gc_count);
657 VMThread::execute(&op);
658
659 // Did the VM operation execute? If so, return the result directly.
660 // This prevents us from looping until time out on requests that can
661 // not be satisfied.
662 if (op.prologue_succeeded()) {
663 assert(Universe::heap()->is_in_permanent_or_null(op.result()),
664 "result not in heap");
665 // If GC was locked out during VM operation then retry allocation
666 // and/or stall as necessary.
667 if (op.gc_locked()) {
668 assert(op.result() == NULL, "must be NULL if gc_locked() is true");
669 continue; // retry and/or stall as necessary
670 }
671 // If a NULL results is being returned, an out-of-memory
672 // will be thrown now. Clear the gc_overhead_limit_exceeded
673 // flag to avoid the following situation.
674 // gc_overhead_limit_exceeded is set during a collection
675 // the collection fails to return enough space and an OOM is thrown
676 // a subsequent GC prematurely throws an out-of-memory because
677 // the gc_overhead_limit_exceeded counts did not start
678 // again from 0.
679 if (op.result() == NULL) {
680 size_policy()->reset_gc_overhead_limit_count();
681 }
682 return op.result();
683 }
684 }
685
686 // The policy object will prevent us from looping forever. If the
687 // time spent in gc crosses a threshold, we will bail out.
688 loop_count++;
689 if ((QueuedAllocationWarningCount > 0) &&
690 (loop_count % QueuedAllocationWarningCount == 0)) {
691 warning("ParallelScavengeHeap::permanent_mem_allocate retries %d times \n\t"
692 " size=%d", loop_count, size);
693 }
694 } while (result == NULL);
695
696 return result;
697 }
698
699 //
700 // This is the policy code for permanent allocations which have failed
701 // and require a collection. Note that just as in failed_mem_allocate,
702 // we do not set collection policy, only where & when to allocate and
703 // collect.
704 HeapWord* ParallelScavengeHeap::failed_permanent_mem_allocate(size_t size) {
705 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
706 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
707 assert(!Universe::heap()->is_gc_active(), "not reentrant");
708 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
709 assert(size > perm_gen()->free_in_words(), "Allocation should fail");
710
711 // We assume (and assert!) that an allocation at this point will fail
712 // unless we collect.
713
714 // First level allocation failure. Mark-sweep and allocate in perm gen.
715 GCCauseSetter gccs(this, GCCause::_allocation_failure);
716 invoke_full_gc(false);
717 HeapWord* result = perm_gen()->allocate_permanent(size);
718
719 // Second level allocation failure. We're running out of memory.
720 if (result == NULL) {
721 invoke_full_gc(true);
722 result = perm_gen()->allocate_permanent(size);
723 }
724
725 return result;
726 }
727
728 void ParallelScavengeHeap::ensure_parsability(bool retire_tlabs) {
729 CollectedHeap::ensure_parsability(retire_tlabs);
730 young_gen()->eden_space()->ensure_parsability();
731 }
732
733 size_t ParallelScavengeHeap::unsafe_max_alloc() {
734 return young_gen()->eden_space()->free_in_bytes();
735 }
736
737 size_t ParallelScavengeHeap::tlab_capacity(Thread* thr) const {
738 return young_gen()->eden_space()->tlab_capacity(thr);
739 }
740
741 size_t ParallelScavengeHeap::unsafe_max_tlab_alloc(Thread* thr) const {
742 return young_gen()->eden_space()->unsafe_max_tlab_alloc(thr);
743 }
744
745 HeapWord* ParallelScavengeHeap::allocate_new_tlab(size_t size) {
746 return young_gen()->allocate(size, true);
747 }
748
749 void ParallelScavengeHeap::accumulate_statistics_all_tlabs() {
750 CollectedHeap::accumulate_statistics_all_tlabs();
751 }
752
753 void ParallelScavengeHeap::resize_all_tlabs() {
754 CollectedHeap::resize_all_tlabs();
755 }
756
757 bool ParallelScavengeHeap::can_elide_initializing_store_barrier(oop new_obj) {
758 // We don't need barriers for stores to objects in the
759 // young gen and, a fortiori, for initializing stores to
760 // objects therein.
761 return is_in_young(new_obj);
762 }
763
764 // This method is used by System.gc() and JVMTI.
765 void ParallelScavengeHeap::collect(GCCause::Cause cause) {
766 assert(!Heap_lock->owned_by_self(),
767 "this thread should not own the Heap_lock");
768
769 unsigned int gc_count = 0;
770 unsigned int full_gc_count = 0;
771 {
772 MutexLocker ml(Heap_lock);
773 // This value is guarded by the Heap_lock
774 gc_count = Universe::heap()->total_collections();
775 full_gc_count = Universe::heap()->total_full_collections();
776 }
777
778 VM_ParallelGCSystemGC op(gc_count, full_gc_count, cause);
779 VMThread::execute(&op);
780 }
781
782 // This interface assumes that it's being called by the
783 // vm thread. It collects the heap assuming that the
784 // heap lock is already held and that we are executing in
785 // the context of the vm thread.
786 void ParallelScavengeHeap::collect_as_vm_thread(GCCause::Cause cause) {
787 assert(Thread::current()->is_VM_thread(), "Precondition#1");
788 assert(Heap_lock->is_locked(), "Precondition#2");
789 GCCauseSetter gcs(this, cause);
790 switch (cause) {
791 case GCCause::_heap_inspection:
792 case GCCause::_heap_dump: {
793 HandleMark hm;
794 invoke_full_gc(false);
795 break;
796 }
797 default: // XXX FIX ME
798 ShouldNotReachHere();
799 }
800 }
801
802
803 void ParallelScavengeHeap::oop_iterate(OopClosure* cl) {
804 Unimplemented();
805 }
806
807 void ParallelScavengeHeap::object_iterate(ObjectClosure* cl) {
808 young_gen()->object_iterate(cl);
809 old_gen()->object_iterate(cl);
810 perm_gen()->object_iterate(cl);
811 }
812
813 void ParallelScavengeHeap::permanent_oop_iterate(OopClosure* cl) {
814 Unimplemented();
815 }
816
817 void ParallelScavengeHeap::permanent_object_iterate(ObjectClosure* cl) {
818 perm_gen()->object_iterate(cl);
819 }
820
821 HeapWord* ParallelScavengeHeap::block_start(const void* addr) const {
822 if (young_gen()->is_in_reserved(addr)) {
823 assert(young_gen()->is_in(addr),
824 "addr should be in allocated part of young gen");
825 // called from os::print_location by find or VMError
826 if (Debugging || VMError::fatal_error_in_progress()) return NULL;
827 Unimplemented();
828 } else if (old_gen()->is_in_reserved(addr)) {
829 assert(old_gen()->is_in(addr),
830 "addr should be in allocated part of old gen");
831 return old_gen()->start_array()->object_start((HeapWord*)addr);
832 } else if (perm_gen()->is_in_reserved(addr)) {
833 assert(perm_gen()->is_in(addr),
834 "addr should be in allocated part of perm gen");
835 return perm_gen()->start_array()->object_start((HeapWord*)addr);
836 }
837 return 0;
838 }
839
840 size_t ParallelScavengeHeap::block_size(const HeapWord* addr) const {
841 return oop(addr)->size();
842 }
843
844 bool ParallelScavengeHeap::block_is_obj(const HeapWord* addr) const {
845 return block_start(addr) == addr;
846 }
847
848 jlong ParallelScavengeHeap::millis_since_last_gc() {
849 return UseParallelOldGC ?
850 PSParallelCompact::millis_since_last_gc() :
851 PSMarkSweep::millis_since_last_gc();
852 }
853
854 void ParallelScavengeHeap::prepare_for_verify() {
855 ensure_parsability(false); // no need to retire TLABs for verification
856 }
857
858 void ParallelScavengeHeap::print() const { print_on(tty); }
859
860 void ParallelScavengeHeap::print_on(outputStream* st) const {
861 young_gen()->print_on(st);
862 old_gen()->print_on(st);
863 perm_gen()->print_on(st);
864 }
865
866 void ParallelScavengeHeap::gc_threads_do(ThreadClosure* tc) const {
867 PSScavenge::gc_task_manager()->threads_do(tc);
868 }
869
870 void ParallelScavengeHeap::print_gc_threads_on(outputStream* st) const {
871 PSScavenge::gc_task_manager()->print_threads_on(st);
872 }
873
874 void ParallelScavengeHeap::print_tracing_info() const {
875 if (TraceGen0Time) {
876 double time = PSScavenge::accumulated_time()->seconds();
877 tty->print_cr("[Accumulated GC generation 0 time %3.7f secs]", time);
878 }
879 if (TraceGen1Time) {
880 double time = PSMarkSweep::accumulated_time()->seconds();
881 tty->print_cr("[Accumulated GC generation 1 time %3.7f secs]", time);
882 }
883 }
884
885
886 void ParallelScavengeHeap::verify(bool allow_dirty, bool silent, bool option /* ignored */) {
887 // Why do we need the total_collections()-filter below?
888 if (total_collections() > 0) {
889 if (!silent) {
890 gclog_or_tty->print("permanent ");
891 }
892 perm_gen()->verify(allow_dirty);
893
894 if (!silent) {
895 gclog_or_tty->print("tenured ");
896 }
897 old_gen()->verify(allow_dirty);
898
899 if (!silent) {
900 gclog_or_tty->print("eden ");
901 }
902 young_gen()->verify(allow_dirty);
903 }
904 if (!silent) {
905 gclog_or_tty->print("ref_proc ");
906 }
907 ReferenceProcessor::verify();
908 }
909
910 void ParallelScavengeHeap::print_heap_change(size_t prev_used) {
911 if (PrintGCDetails && Verbose) {
912 gclog_or_tty->print(" " SIZE_FORMAT
913 "->" SIZE_FORMAT
914 "(" SIZE_FORMAT ")",
915 prev_used, used(), capacity());
916 } else {
917 gclog_or_tty->print(" " SIZE_FORMAT "K"
918 "->" SIZE_FORMAT "K"
919 "(" SIZE_FORMAT "K)",
920 prev_used / K, used() / K, capacity() / K);
921 }
922 }
923
924 ParallelScavengeHeap* ParallelScavengeHeap::heap() {
925 assert(_psh != NULL, "Uninitialized access to ParallelScavengeHeap::heap()");
926 assert(_psh->kind() == CollectedHeap::ParallelScavengeHeap, "not a parallel scavenge heap");
927 return _psh;
928 }
929
930 // Before delegating the resize to the young generation,
931 // the reserved space for the young and old generations
932 // may be changed to accomodate the desired resize.
933 void ParallelScavengeHeap::resize_young_gen(size_t eden_size,
934 size_t survivor_size) {
935 if (UseAdaptiveGCBoundary) {
936 if (size_policy()->bytes_absorbed_from_eden() != 0) {
937 size_policy()->reset_bytes_absorbed_from_eden();
938 return; // The generation changed size already.
939 }
940 gens()->adjust_boundary_for_young_gen_needs(eden_size, survivor_size);
941 }
942
943 // Delegate the resize to the generation.
944 _young_gen->resize(eden_size, survivor_size);
945 }
946
947 // Before delegating the resize to the old generation,
948 // the reserved space for the young and old generations
949 // may be changed to accomodate the desired resize.
950 void ParallelScavengeHeap::resize_old_gen(size_t desired_free_space) {
951 if (UseAdaptiveGCBoundary) {
952 if (size_policy()->bytes_absorbed_from_eden() != 0) {
953 size_policy()->reset_bytes_absorbed_from_eden();
954 return; // The generation changed size already.
955 }
956 gens()->adjust_boundary_for_old_gen_needs(desired_free_space);
957 }
958
959 // Delegate the resize to the generation.
960 _old_gen->resize(desired_free_space);
961 }
962
963 ParallelScavengeHeap::ParStrongRootsScope::ParStrongRootsScope() {
964 // nothing particular
965 }
966
967 ParallelScavengeHeap::ParStrongRootsScope::~ParStrongRootsScope() {
968 // nothing particular
969 }
970
971 #ifndef PRODUCT
972 void ParallelScavengeHeap::record_gen_tops_before_GC() {
973 if (ZapUnusedHeapArea) {
974 young_gen()->record_spaces_top();
975 old_gen()->record_spaces_top();
976 perm_gen()->record_spaces_top();
977 }
978 }
979
980 void ParallelScavengeHeap::gen_mangle_unused_area() {
981 if (ZapUnusedHeapArea) {
982 young_gen()->eden_space()->mangle_unused_area();
983 young_gen()->to_space()->mangle_unused_area();
984 young_gen()->from_space()->mangle_unused_area();
985 old_gen()->object_space()->mangle_unused_area();
986 perm_gen()->object_space()->mangle_unused_area();
987 }
988 }
989 #endif