1 /*
2 * Copyright (c) 2001, 2011, 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 // Align old gen size down to preserve specified heap size.
116 assert(og_align == yg_align, "sanity");
117 og_max_size = align_size_down(og_max_size, og_align);
118 og_max_size = MAX2(og_max_size, og_min_size);
119 size_t og_cur_size =
120 align_size_down(_collector_policy->old_gen_size(), og_align);
121 og_cur_size = MAX2(og_cur_size, og_min_size);
122
123 pg_min_size = align_size_up(pg_min_size, pg_align);
124 pg_max_size = align_size_up(pg_max_size, pg_align);
125 size_t pg_cur_size = pg_min_size;
126
127 trace_gen_sizes("ps heap rnd",
128 pg_min_size, pg_max_size,
129 og_min_size, og_max_size,
130 yg_min_size, yg_max_size);
131
132 const size_t total_reserved = pg_max_size + og_max_size + yg_max_size;
133 char* addr = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop);
134
135 // The main part of the heap (old gen + young gen) can often use a larger page
136 // size than is needed or wanted for the perm gen. Use the "compound
137 // alignment" ReservedSpace ctor to avoid having to use the same page size for
138 // all gens.
139
140 ReservedHeapSpace heap_rs(pg_max_size, pg_align, og_max_size + yg_max_size,
141 og_align, addr);
142
143 if (UseCompressedOops) {
144 if (addr != NULL && !heap_rs.is_reserved()) {
145 // Failed to reserve at specified address - the requested memory
146 // region is taken already, for example, by 'java' launcher.
147 // Try again to reserver heap higher.
148 addr = Universe::preferred_heap_base(total_reserved, Universe::ZeroBasedNarrowOop);
149 ReservedHeapSpace heap_rs0(pg_max_size, pg_align, og_max_size + yg_max_size,
150 og_align, addr);
151 if (addr != NULL && !heap_rs0.is_reserved()) {
152 // Failed to reserve at specified address again - give up.
153 addr = Universe::preferred_heap_base(total_reserved, Universe::HeapBasedNarrowOop);
154 assert(addr == NULL, "");
155 ReservedHeapSpace heap_rs1(pg_max_size, pg_align, og_max_size + yg_max_size,
156 og_align, addr);
157 heap_rs = heap_rs1;
158 } else {
159 heap_rs = heap_rs0;
160 }
161 }
162 }
163
164 os::trace_page_sizes("ps perm", pg_min_size, pg_max_size, pg_page_sz,
165 heap_rs.base(), pg_max_size);
166 os::trace_page_sizes("ps main", og_min_size + yg_min_size,
167 og_max_size + yg_max_size, og_page_sz,
168 heap_rs.base() + pg_max_size,
169 heap_rs.size() - pg_max_size);
170 if (!heap_rs.is_reserved()) {
171 vm_shutdown_during_initialization(
172 "Could not reserve enough space for object heap");
173 return JNI_ENOMEM;
174 }
175
176 _reserved = MemRegion((HeapWord*)heap_rs.base(),
177 (HeapWord*)(heap_rs.base() + heap_rs.size()));
178
179 CardTableExtension* const barrier_set = new CardTableExtension(_reserved, 3);
180 _barrier_set = barrier_set;
181 oopDesc::set_bs(_barrier_set);
182 if (_barrier_set == NULL) {
183 vm_shutdown_during_initialization(
184 "Could not reserve enough space for barrier set");
185 return JNI_ENOMEM;
186 }
187
188 // Initial young gen size is 4 Mb
189 //
190 // XXX - what about flag_parser.young_gen_size()?
191 const size_t init_young_size = align_size_up(4 * M, yg_align);
192 yg_cur_size = MAX2(MIN2(init_young_size, yg_max_size), yg_cur_size);
193
194 // Split the reserved space into perm gen and the main heap (everything else).
195 // The main heap uses a different alignment.
196 ReservedSpace perm_rs = heap_rs.first_part(pg_max_size);
197 ReservedSpace main_rs = heap_rs.last_part(pg_max_size, og_align);
198
199 // Make up the generations
200 // Calculate the maximum size that a generation can grow. This
201 // includes growth into the other generation. Note that the
202 // parameter _max_gen_size is kept as the maximum
203 // size of the generation as the boundaries currently stand.
204 // _max_gen_size is still used as that value.
205 double max_gc_pause_sec = ((double) MaxGCPauseMillis)/1000.0;
206 double max_gc_minor_pause_sec = ((double) MaxGCMinorPauseMillis)/1000.0;
207
208 _gens = new AdjoiningGenerations(main_rs,
209 og_cur_size,
210 og_min_size,
211 og_max_size,
212 yg_cur_size,
213 yg_min_size,
214 yg_max_size,
215 yg_align);
216
217 _old_gen = _gens->old_gen();
218 _young_gen = _gens->young_gen();
219
220 const size_t eden_capacity = _young_gen->eden_space()->capacity_in_bytes();
221 const size_t old_capacity = _old_gen->capacity_in_bytes();
222 const size_t initial_promo_size = MIN2(eden_capacity, old_capacity);
223 _size_policy =
224 new PSAdaptiveSizePolicy(eden_capacity,
225 initial_promo_size,
226 young_gen()->to_space()->capacity_in_bytes(),
227 intra_heap_alignment(),
228 max_gc_pause_sec,
229 max_gc_minor_pause_sec,
230 GCTimeRatio
231 );
232
233 _perm_gen = new PSPermGen(perm_rs,
234 pg_align,
235 pg_cur_size,
236 pg_cur_size,
237 pg_max_size,
238 "perm", 2);
239
240 assert(!UseAdaptiveGCBoundary ||
241 (old_gen()->virtual_space()->high_boundary() ==
242 young_gen()->virtual_space()->low_boundary()),
243 "Boundaries must meet");
244 // initialize the policy counters - 2 collectors, 3 generations
245 _gc_policy_counters =
246 new PSGCAdaptivePolicyCounters("ParScav:MSC", 2, 3, _size_policy);
247 _psh = this;
248
249 // Set up the GCTaskManager
250 _gc_task_manager = GCTaskManager::create(ParallelGCThreads);
251
252 if (UseParallelOldGC && !PSParallelCompact::initialize()) {
253 return JNI_ENOMEM;
254 }
255
256 return JNI_OK;
257 }
258
259 void ParallelScavengeHeap::post_initialize() {
260 // Need to init the tenuring threshold
261 PSScavenge::initialize();
262 if (UseParallelOldGC) {
263 PSParallelCompact::post_initialize();
264 } else {
265 PSMarkSweep::initialize();
266 }
267 PSPromotionManager::initialize();
268 }
269
270 void ParallelScavengeHeap::update_counters() {
271 young_gen()->update_counters();
272 old_gen()->update_counters();
273 perm_gen()->update_counters();
274 }
275
276 size_t ParallelScavengeHeap::capacity() const {
277 size_t value = young_gen()->capacity_in_bytes() + old_gen()->capacity_in_bytes();
278 return value;
279 }
280
281 size_t ParallelScavengeHeap::used() const {
282 size_t value = young_gen()->used_in_bytes() + old_gen()->used_in_bytes();
283 return value;
284 }
285
286 bool ParallelScavengeHeap::is_maximal_no_gc() const {
287 return old_gen()->is_maximal_no_gc() && young_gen()->is_maximal_no_gc();
288 }
289
290
291 size_t ParallelScavengeHeap::permanent_capacity() const {
292 return perm_gen()->capacity_in_bytes();
293 }
294
295 size_t ParallelScavengeHeap::permanent_used() const {
296 return perm_gen()->used_in_bytes();
297 }
298
299 size_t ParallelScavengeHeap::max_capacity() const {
300 size_t estimated = reserved_region().byte_size();
301 estimated -= perm_gen()->reserved().byte_size();
302 if (UseAdaptiveSizePolicy) {
303 estimated -= _size_policy->max_survivor_size(young_gen()->max_size());
304 } else {
305 estimated -= young_gen()->to_space()->capacity_in_bytes();
306 }
307 return MAX2(estimated, capacity());
308 }
309
310 bool ParallelScavengeHeap::is_in(const void* p) const {
311 if (young_gen()->is_in(p)) {
312 return true;
313 }
314
315 if (old_gen()->is_in(p)) {
316 return true;
317 }
318
319 if (perm_gen()->is_in(p)) {
320 return true;
321 }
322
323 return false;
324 }
325
326 bool ParallelScavengeHeap::is_in_reserved(const void* p) const {
327 if (young_gen()->is_in_reserved(p)) {
328 return true;
329 }
330
331 if (old_gen()->is_in_reserved(p)) {
332 return true;
333 }
334
335 if (perm_gen()->is_in_reserved(p)) {
336 return true;
337 }
338
339 return false;
340 }
341
342 bool ParallelScavengeHeap::is_scavengable(const void* addr) {
343 return is_in_young((oop)addr);
344 }
345
346 #ifdef ASSERT
347 // Don't implement this by using is_in_young(). This method is used
348 // in some cases to check that is_in_young() is correct.
349 bool ParallelScavengeHeap::is_in_partial_collection(const void *p) {
350 assert(is_in_reserved(p) || p == NULL,
351 "Does not work if address is non-null and outside of the heap");
352 // The order of the generations is perm (low addr), old, young (high addr)
353 return p >= old_gen()->reserved().end();
354 }
355 #endif
356
357 // There are two levels of allocation policy here.
358 //
359 // When an allocation request fails, the requesting thread must invoke a VM
360 // operation, transfer control to the VM thread, and await the results of a
361 // garbage collection. That is quite expensive, and we should avoid doing it
362 // multiple times if possible.
363 //
364 // To accomplish this, we have a basic allocation policy, and also a
365 // failed allocation policy.
366 //
367 // The basic allocation policy controls how you allocate memory without
368 // attempting garbage collection. It is okay to grab locks and
369 // expand the heap, if that can be done without coming to a safepoint.
370 // It is likely that the basic allocation policy will not be very
371 // aggressive.
372 //
373 // The failed allocation policy is invoked from the VM thread after
374 // the basic allocation policy is unable to satisfy a mem_allocate
375 // request. This policy needs to cover the entire range of collection,
376 // heap expansion, and out-of-memory conditions. It should make every
377 // attempt to allocate the requested memory.
378
379 // Basic allocation policy. Should never be called at a safepoint, or
380 // from the VM thread.
381 //
382 // This method must handle cases where many mem_allocate requests fail
383 // simultaneously. When that happens, only one VM operation will succeed,
384 // and the rest will not be executed. For that reason, this method loops
385 // during failed allocation attempts. If the java heap becomes exhausted,
386 // we rely on the size_policy object to force a bail out.
387 HeapWord* ParallelScavengeHeap::mem_allocate(
388 size_t size,
389 bool* gc_overhead_limit_was_exceeded) {
390 assert(!SafepointSynchronize::is_at_safepoint(), "should not be at safepoint");
391 assert(Thread::current() != (Thread*)VMThread::vm_thread(), "should not be in vm thread");
392 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
393
394 // In general gc_overhead_limit_was_exceeded should be false so
395 // set it so here and reset it to true only if the gc time
396 // limit is being exceeded as checked below.
397 *gc_overhead_limit_was_exceeded = false;
398
399 HeapWord* result = young_gen()->allocate(size);
400
401 uint loop_count = 0;
402 uint gc_count = 0;
403
404 while (result == NULL) {
405 // We don't want to have multiple collections for a single filled generation.
406 // To prevent this, each thread tracks the total_collections() value, and if
407 // the count has changed, does not do a new collection.
408 //
409 // The collection count must be read only while holding the heap lock. VM
410 // operations also hold the heap lock during collections. There is a lock
411 // contention case where thread A blocks waiting on the Heap_lock, while
412 // thread B is holding it doing a collection. When thread A gets the lock,
413 // the collection count has already changed. To prevent duplicate collections,
414 // The policy MUST attempt allocations during the same period it reads the
415 // total_collections() value!
416 {
417 MutexLocker ml(Heap_lock);
418 gc_count = Universe::heap()->total_collections();
419
420 result = young_gen()->allocate(size);
421
422 // (1) If the requested object is too large to easily fit in the
423 // young_gen, or
424 // (2) If GC is locked out via GCLocker, young gen is full and
425 // the need for a GC already signalled to GCLocker (done
426 // at a safepoint),
427 // ... then, rather than force a safepoint and (a potentially futile)
428 // collection (attempt) for each allocation, try allocation directly
429 // in old_gen. For case (2) above, we may in the future allow
430 // TLAB allocation directly in the old gen.
431 if (result != NULL) {
432 return result;
433 }
434 if (size >= (young_gen()->eden_space()->capacity_in_words(Thread::current()) / 2)) {
435 result = old_gen()->allocate(size);
436 if (result != NULL) {
437 return result;
438 }
439 }
440 if (GC_locker::is_active_and_needs_gc()) {
441 // If this thread is not in a jni critical section, we stall
442 // the requestor until the critical section has cleared and
443 // GC allowed. When the critical section clears, a GC is
444 // initiated by the last thread exiting the critical section; so
445 // we retry the allocation sequence from the beginning of the loop,
446 // rather than causing more, now probably unnecessary, GC attempts.
447 JavaThread* jthr = JavaThread::current();
448 if (!jthr->in_critical()) {
449 MutexUnlocker mul(Heap_lock);
450 GC_locker::stall_until_clear();
451 continue;
452 } else {
453 if (CheckJNICalls) {
454 fatal("Possible deadlock due to allocating while"
455 " in jni critical section");
456 }
457 return NULL;
458 }
459 }
460 }
461
462 if (result == NULL) {
463
464 // Generate a VM operation
465 VM_ParallelGCFailedAllocation op(size, gc_count);
466 VMThread::execute(&op);
467
468 // Did the VM operation execute? If so, return the result directly.
469 // This prevents us from looping until time out on requests that can
470 // not be satisfied.
471 if (op.prologue_succeeded()) {
472 assert(Universe::heap()->is_in_or_null(op.result()),
473 "result not in heap");
474
475 // If GC was locked out during VM operation then retry allocation
476 // and/or stall as necessary.
477 if (op.gc_locked()) {
478 assert(op.result() == NULL, "must be NULL if gc_locked() is true");
479 continue; // retry and/or stall as necessary
480 }
481
482 // Exit the loop if the gc time limit has been exceeded.
483 // The allocation must have failed above ("result" guarding
484 // this path is NULL) and the most recent collection has exceeded the
485 // gc overhead limit (although enough may have been collected to
486 // satisfy the allocation). Exit the loop so that an out-of-memory
487 // will be thrown (return a NULL ignoring the contents of
488 // op.result()),
489 // but clear gc_overhead_limit_exceeded so that the next collection
490 // starts with a clean slate (i.e., forgets about previous overhead
491 // excesses). Fill op.result() with a filler object so that the
492 // heap remains parsable.
493 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
494 const bool softrefs_clear = collector_policy()->all_soft_refs_clear();
495 assert(!limit_exceeded || softrefs_clear, "Should have been cleared");
496 if (limit_exceeded && softrefs_clear) {
497 *gc_overhead_limit_was_exceeded = true;
498 size_policy()->set_gc_overhead_limit_exceeded(false);
499 if (PrintGCDetails && Verbose) {
500 gclog_or_tty->print_cr("ParallelScavengeHeap::mem_allocate: "
501 "return NULL because gc_overhead_limit_exceeded is set");
502 }
503 if (op.result() != NULL) {
504 CollectedHeap::fill_with_object(op.result(), size);
505 }
506 return NULL;
507 }
508
509 return op.result();
510 }
511 }
512
513 // The policy object will prevent us from looping forever. If the
514 // time spent in gc crosses a threshold, we will bail out.
515 loop_count++;
516 if ((result == NULL) && (QueuedAllocationWarningCount > 0) &&
517 (loop_count % QueuedAllocationWarningCount == 0)) {
518 warning("ParallelScavengeHeap::mem_allocate retries %d times \n\t"
519 " size=%d", loop_count, size);
520 }
521 }
522
523 return result;
524 }
525
526 // Failed allocation policy. Must be called from the VM thread, and
527 // only at a safepoint! Note that this method has policy for allocation
528 // flow, and NOT collection policy. So we do not check for gc collection
529 // time over limit here, that is the responsibility of the heap specific
530 // collection methods. This method decides where to attempt allocations,
531 // and when to attempt collections, but no collection specific policy.
532 HeapWord* ParallelScavengeHeap::failed_mem_allocate(size_t size) {
533 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
534 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
535 assert(!Universe::heap()->is_gc_active(), "not reentrant");
536 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
537
538 size_t mark_sweep_invocation_count = total_invocations();
539
540 // We assume (and assert!) that an allocation at this point will fail
541 // unless we collect.
542
543 // First level allocation failure, scavenge and allocate in young gen.
544 GCCauseSetter gccs(this, GCCause::_allocation_failure);
545 PSScavenge::invoke();
546 HeapWord* result = young_gen()->allocate(size);
547
548 // Second level allocation failure.
549 // Mark sweep and allocate in young generation.
550 if (result == NULL) {
551 // There is some chance the scavenge method decided to invoke mark_sweep.
552 // Don't mark sweep twice if so.
553 if (mark_sweep_invocation_count == total_invocations()) {
554 invoke_full_gc(false);
555 result = young_gen()->allocate(size);
556 }
557 }
558
559 // Third level allocation failure.
560 // After mark sweep and young generation allocation failure,
561 // allocate in old generation.
562 if (result == NULL) {
563 result = old_gen()->allocate(size);
564 }
565
566 // Fourth level allocation failure. We're running out of memory.
567 // More complete mark sweep and allocate in young generation.
568 if (result == NULL) {
569 invoke_full_gc(true);
570 result = young_gen()->allocate(size);
571 }
572
573 // Fifth level allocation failure.
574 // After more complete mark sweep, allocate in old generation.
575 if (result == NULL) {
576 result = old_gen()->allocate(size);
577 }
578
579 return result;
580 }
581
582 //
583 // This is the policy loop for allocating in the permanent generation.
584 // If the initial allocation fails, we create a vm operation which will
585 // cause a collection.
586 HeapWord* ParallelScavengeHeap::permanent_mem_allocate(size_t size) {
587 assert(!SafepointSynchronize::is_at_safepoint(), "should not be at safepoint");
588 assert(Thread::current() != (Thread*)VMThread::vm_thread(), "should not be in vm thread");
589 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
590
591 HeapWord* result;
592
593 uint loop_count = 0;
594 uint gc_count = 0;
595 uint full_gc_count = 0;
596
597 do {
598 // We don't want to have multiple collections for a single filled generation.
599 // To prevent this, each thread tracks the total_collections() value, and if
600 // the count has changed, does not do a new collection.
601 //
602 // The collection count must be read only while holding the heap lock. VM
603 // operations also hold the heap lock during collections. There is a lock
604 // contention case where thread A blocks waiting on the Heap_lock, while
605 // thread B is holding it doing a collection. When thread A gets the lock,
606 // the collection count has already changed. To prevent duplicate collections,
607 // The policy MUST attempt allocations during the same period it reads the
608 // total_collections() value!
609 {
610 MutexLocker ml(Heap_lock);
611 gc_count = Universe::heap()->total_collections();
612 full_gc_count = Universe::heap()->total_full_collections();
613
614 result = perm_gen()->allocate_permanent(size);
615
616 if (result != NULL) {
617 return result;
618 }
619
620 if (GC_locker::is_active_and_needs_gc()) {
621 // If this thread is not in a jni critical section, we stall
622 // the requestor until the critical section has cleared and
623 // GC allowed. When the critical section clears, a GC is
624 // initiated by the last thread exiting the critical section; so
625 // we retry the allocation sequence from the beginning of the loop,
626 // rather than causing more, now probably unnecessary, GC attempts.
627 JavaThread* jthr = JavaThread::current();
628 if (!jthr->in_critical()) {
629 MutexUnlocker mul(Heap_lock);
630 GC_locker::stall_until_clear();
631 continue;
632 } else {
633 if (CheckJNICalls) {
634 fatal("Possible deadlock due to allocating while"
635 " in jni critical section");
636 }
637 return NULL;
638 }
639 }
640 }
641
642 if (result == NULL) {
643
644 // Exit the loop if the gc time limit has been exceeded.
645 // The allocation must have failed above (result must be NULL),
646 // and the most recent collection must have exceeded the
647 // gc time limit. Exit the loop so that an out-of-memory
648 // will be thrown (returning a NULL will do that), but
649 // clear gc_overhead_limit_exceeded so that the next collection
650 // will succeeded if the applications decides to handle the
651 // out-of-memory and tries to go on.
652 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
653 if (limit_exceeded) {
654 size_policy()->set_gc_overhead_limit_exceeded(false);
655 if (PrintGCDetails && Verbose) {
656 gclog_or_tty->print_cr("ParallelScavengeHeap::permanent_mem_allocate:"
657 " return NULL because gc_overhead_limit_exceeded is set");
658 }
659 assert(result == NULL, "Allocation did not fail");
660 return NULL;
661 }
662
663 // Generate a VM operation
664 VM_ParallelGCFailedPermanentAllocation op(size, gc_count, full_gc_count);
665 VMThread::execute(&op);
666
667 // Did the VM operation execute? If so, return the result directly.
668 // This prevents us from looping until time out on requests that can
669 // not be satisfied.
670 if (op.prologue_succeeded()) {
671 assert(Universe::heap()->is_in_permanent_or_null(op.result()),
672 "result not in heap");
673 // If GC was locked out during VM operation then retry allocation
674 // and/or stall as necessary.
675 if (op.gc_locked()) {
676 assert(op.result() == NULL, "must be NULL if gc_locked() is true");
677 continue; // retry and/or stall as necessary
678 }
679 // If a NULL results is being returned, an out-of-memory
680 // will be thrown now. Clear the gc_overhead_limit_exceeded
681 // flag to avoid the following situation.
682 // gc_overhead_limit_exceeded is set during a collection
683 // the collection fails to return enough space and an OOM is thrown
684 // a subsequent GC prematurely throws an out-of-memory because
685 // the gc_overhead_limit_exceeded counts did not start
686 // again from 0.
687 if (op.result() == NULL) {
688 size_policy()->reset_gc_overhead_limit_count();
689 }
690 return op.result();
691 }
692 }
693
694 // The policy object will prevent us from looping forever. If the
695 // time spent in gc crosses a threshold, we will bail out.
696 loop_count++;
697 if ((QueuedAllocationWarningCount > 0) &&
698 (loop_count % QueuedAllocationWarningCount == 0)) {
699 warning("ParallelScavengeHeap::permanent_mem_allocate retries %d times \n\t"
700 " size=%d", loop_count, size);
701 }
702 } while (result == NULL);
703
704 return result;
705 }
706
707 //
708 // This is the policy code for permanent allocations which have failed
709 // and require a collection. Note that just as in failed_mem_allocate,
710 // we do not set collection policy, only where & when to allocate and
711 // collect.
712 HeapWord* ParallelScavengeHeap::failed_permanent_mem_allocate(size_t size) {
713 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
714 assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");
715 assert(!Universe::heap()->is_gc_active(), "not reentrant");
716 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
717 assert(size > perm_gen()->free_in_words(), "Allocation should fail");
718
719 // We assume (and assert!) that an allocation at this point will fail
720 // unless we collect.
721
722 // First level allocation failure. Mark-sweep and allocate in perm gen.
723 GCCauseSetter gccs(this, GCCause::_allocation_failure);
724 invoke_full_gc(false);
725 HeapWord* result = perm_gen()->allocate_permanent(size);
726
727 // Second level allocation failure. We're running out of memory.
728 if (result == NULL) {
729 invoke_full_gc(true);
730 result = perm_gen()->allocate_permanent(size);
731 }
732
733 return result;
734 }
735
736 void ParallelScavengeHeap::ensure_parsability(bool retire_tlabs) {
737 CollectedHeap::ensure_parsability(retire_tlabs);
738 young_gen()->eden_space()->ensure_parsability();
739 }
740
741 size_t ParallelScavengeHeap::unsafe_max_alloc() {
742 return young_gen()->eden_space()->free_in_bytes();
743 }
744
745 size_t ParallelScavengeHeap::tlab_capacity(Thread* thr) const {
746 return young_gen()->eden_space()->tlab_capacity(thr);
747 }
748
749 size_t ParallelScavengeHeap::unsafe_max_tlab_alloc(Thread* thr) const {
750 return young_gen()->eden_space()->unsafe_max_tlab_alloc(thr);
751 }
752
753 HeapWord* ParallelScavengeHeap::allocate_new_tlab(size_t size) {
754 return young_gen()->allocate(size);
755 }
756
757 void ParallelScavengeHeap::accumulate_statistics_all_tlabs() {
758 CollectedHeap::accumulate_statistics_all_tlabs();
759 }
760
761 void ParallelScavengeHeap::resize_all_tlabs() {
762 CollectedHeap::resize_all_tlabs();
763 }
764
765 bool ParallelScavengeHeap::can_elide_initializing_store_barrier(oop new_obj) {
766 // We don't need barriers for stores to objects in the
767 // young gen and, a fortiori, for initializing stores to
768 // objects therein.
769 return is_in_young(new_obj);
770 }
771
772 // This method is used by System.gc() and JVMTI.
773 void ParallelScavengeHeap::collect(GCCause::Cause cause) {
774 assert(!Heap_lock->owned_by_self(),
775 "this thread should not own the Heap_lock");
776
777 unsigned int gc_count = 0;
778 unsigned int full_gc_count = 0;
779 {
780 MutexLocker ml(Heap_lock);
781 // This value is guarded by the Heap_lock
782 gc_count = Universe::heap()->total_collections();
783 full_gc_count = Universe::heap()->total_full_collections();
784 }
785
786 VM_ParallelGCSystemGC op(gc_count, full_gc_count, cause);
787 VMThread::execute(&op);
788 }
789
790 // This interface assumes that it's being called by the
791 // vm thread. It collects the heap assuming that the
792 // heap lock is already held and that we are executing in
793 // the context of the vm thread.
794 void ParallelScavengeHeap::collect_as_vm_thread(GCCause::Cause cause) {
795 assert(Thread::current()->is_VM_thread(), "Precondition#1");
796 assert(Heap_lock->is_locked(), "Precondition#2");
797 GCCauseSetter gcs(this, cause);
798 switch (cause) {
799 case GCCause::_heap_inspection:
800 case GCCause::_heap_dump: {
801 HandleMark hm;
802 invoke_full_gc(false);
803 break;
804 }
805 default: // XXX FIX ME
806 ShouldNotReachHere();
807 }
808 }
809
810
811 void ParallelScavengeHeap::oop_iterate(OopClosure* cl) {
812 Unimplemented();
813 }
814
815 void ParallelScavengeHeap::object_iterate(ObjectClosure* cl) {
816 young_gen()->object_iterate(cl);
817 old_gen()->object_iterate(cl);
818 perm_gen()->object_iterate(cl);
819 }
820
821 void ParallelScavengeHeap::permanent_oop_iterate(OopClosure* cl) {
822 Unimplemented();
823 }
824
825 void ParallelScavengeHeap::permanent_object_iterate(ObjectClosure* cl) {
826 perm_gen()->object_iterate(cl);
827 }
828
829 HeapWord* ParallelScavengeHeap::block_start(const void* addr) const {
830 if (young_gen()->is_in_reserved(addr)) {
831 assert(young_gen()->is_in(addr),
832 "addr should be in allocated part of young gen");
833 // called from os::print_location by find or VMError
834 if (Debugging || VMError::fatal_error_in_progress()) return NULL;
835 Unimplemented();
836 } else if (old_gen()->is_in_reserved(addr)) {
837 assert(old_gen()->is_in(addr),
838 "addr should be in allocated part of old gen");
839 return old_gen()->start_array()->object_start((HeapWord*)addr);
840 } else if (perm_gen()->is_in_reserved(addr)) {
841 assert(perm_gen()->is_in(addr),
842 "addr should be in allocated part of perm gen");
843 return perm_gen()->start_array()->object_start((HeapWord*)addr);
844 }
845 return 0;
846 }
847
848 size_t ParallelScavengeHeap::block_size(const HeapWord* addr) const {
849 return oop(addr)->size();
850 }
851
852 bool ParallelScavengeHeap::block_is_obj(const HeapWord* addr) const {
853 return block_start(addr) == addr;
854 }
855
856 jlong ParallelScavengeHeap::millis_since_last_gc() {
857 return UseParallelOldGC ?
858 PSParallelCompact::millis_since_last_gc() :
859 PSMarkSweep::millis_since_last_gc();
860 }
861
862 void ParallelScavengeHeap::prepare_for_verify() {
863 ensure_parsability(false); // no need to retire TLABs for verification
864 }
865
866 void ParallelScavengeHeap::print() const { print_on(tty); }
867
868 void ParallelScavengeHeap::print_on(outputStream* st) const {
869 young_gen()->print_on(st);
870 old_gen()->print_on(st);
871 perm_gen()->print_on(st);
872 }
873
874 void ParallelScavengeHeap::gc_threads_do(ThreadClosure* tc) const {
875 PSScavenge::gc_task_manager()->threads_do(tc);
876 }
877
878 void ParallelScavengeHeap::print_gc_threads_on(outputStream* st) const {
879 PSScavenge::gc_task_manager()->print_threads_on(st);
880 }
881
882 void ParallelScavengeHeap::print_tracing_info() const {
883 if (TraceGen0Time) {
884 double time = PSScavenge::accumulated_time()->seconds();
885 tty->print_cr("[Accumulated GC generation 0 time %3.7f secs]", time);
886 }
887 if (TraceGen1Time) {
888 double time = PSMarkSweep::accumulated_time()->seconds();
889 tty->print_cr("[Accumulated GC generation 1 time %3.7f secs]", time);
890 }
891 }
892
893
894 void ParallelScavengeHeap::verify(bool allow_dirty, bool silent, VerifyOption option /* ignored */) {
895 // Why do we need the total_collections()-filter below?
896 if (total_collections() > 0) {
897 if (!silent) {
898 gclog_or_tty->print("permanent ");
899 }
900 perm_gen()->verify(allow_dirty);
901
902 if (!silent) {
903 gclog_or_tty->print("tenured ");
904 }
905 old_gen()->verify(allow_dirty);
906
907 if (!silent) {
908 gclog_or_tty->print("eden ");
909 }
910 young_gen()->verify(allow_dirty);
911 }
912 }
913
914 void ParallelScavengeHeap::print_heap_change(size_t prev_used) {
915 if (PrintGCDetails && Verbose) {
916 gclog_or_tty->print(" " SIZE_FORMAT
917 "->" SIZE_FORMAT
918 "(" SIZE_FORMAT ")",
919 prev_used, used(), capacity());
920 } else {
921 gclog_or_tty->print(" " SIZE_FORMAT "K"
922 "->" SIZE_FORMAT "K"
923 "(" SIZE_FORMAT "K)",
924 prev_used / K, used() / K, capacity() / K);
925 }
926 }
927
928 ParallelScavengeHeap* ParallelScavengeHeap::heap() {
929 assert(_psh != NULL, "Uninitialized access to ParallelScavengeHeap::heap()");
930 assert(_psh->kind() == CollectedHeap::ParallelScavengeHeap, "not a parallel scavenge heap");
931 return _psh;
932 }
933
934 // Before delegating the resize to the young generation,
935 // the reserved space for the young and old generations
936 // may be changed to accomodate the desired resize.
937 void ParallelScavengeHeap::resize_young_gen(size_t eden_size,
938 size_t survivor_size) {
939 if (UseAdaptiveGCBoundary) {
940 if (size_policy()->bytes_absorbed_from_eden() != 0) {
941 size_policy()->reset_bytes_absorbed_from_eden();
942 return; // The generation changed size already.
943 }
944 gens()->adjust_boundary_for_young_gen_needs(eden_size, survivor_size);
945 }
946
947 // Delegate the resize to the generation.
948 _young_gen->resize(eden_size, survivor_size);
949 }
950
951 // Before delegating the resize to the old generation,
952 // the reserved space for the young and old generations
953 // may be changed to accomodate the desired resize.
954 void ParallelScavengeHeap::resize_old_gen(size_t desired_free_space) {
955 if (UseAdaptiveGCBoundary) {
956 if (size_policy()->bytes_absorbed_from_eden() != 0) {
957 size_policy()->reset_bytes_absorbed_from_eden();
958 return; // The generation changed size already.
959 }
960 gens()->adjust_boundary_for_old_gen_needs(desired_free_space);
961 }
962
963 // Delegate the resize to the generation.
964 _old_gen->resize(desired_free_space);
965 }
966
967 ParallelScavengeHeap::ParStrongRootsScope::ParStrongRootsScope() {
968 // nothing particular
969 }
970
971 ParallelScavengeHeap::ParStrongRootsScope::~ParStrongRootsScope() {
972 // nothing particular
973 }
974
975 #ifndef PRODUCT
976 void ParallelScavengeHeap::record_gen_tops_before_GC() {
977 if (ZapUnusedHeapArea) {
978 young_gen()->record_spaces_top();
979 old_gen()->record_spaces_top();
980 perm_gen()->record_spaces_top();
981 }
982 }
983
984 void ParallelScavengeHeap::gen_mangle_unused_area() {
985 if (ZapUnusedHeapArea) {
986 young_gen()->eden_space()->mangle_unused_area();
987 young_gen()->to_space()->mangle_unused_area();
988 young_gen()->from_space()->mangle_unused_area();
989 old_gen()->object_space()->mangle_unused_area();
990 perm_gen()->object_space()->mangle_unused_area();
991 }
992 }
993 #endif