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