1 /*
2 * Copyright (c) 2001, 2012, 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/shared/adaptiveSizePolicy.hpp"
27 #include "gc_implementation/shared/gcPolicyCounters.hpp"
28 #include "gc_implementation/shared/vmGCOperations.hpp"
29 #include "memory/cardTableRS.hpp"
30 #include "memory/collectorPolicy.hpp"
31 #include "memory/gcLocker.inline.hpp"
32 #include "memory/genCollectedHeap.hpp"
33 #include "memory/generationSpec.hpp"
34 #include "memory/space.hpp"
35 #include "memory/universe.hpp"
36 #include "runtime/arguments.hpp"
37 #include "runtime/globals_extension.hpp"
38 #include "runtime/handles.inline.hpp"
39 #include "runtime/java.hpp"
40 #include "runtime/thread.inline.hpp"
41 #include "runtime/vmThread.hpp"
42 #ifndef SERIALGC
43 #include "gc_implementation/concurrentMarkSweep/cmsAdaptiveSizePolicy.hpp"
44 #include "gc_implementation/concurrentMarkSweep/cmsGCAdaptivePolicyCounters.hpp"
45 #endif
46
47 // CollectorPolicy methods.
48
49 void CollectorPolicy::initialize_flags() {
50 if (MetaspaceSize > MaxMetaspaceSize) {
51 MaxMetaspaceSize = MetaspaceSize;
52 }
53 MetaspaceSize = MAX2(min_alignment(), align_size_down_(MetaspaceSize, min_alignment()));
54 // Don't increase Metaspace size limit above specified.
55 MaxMetaspaceSize = align_size_down(MaxMetaspaceSize, max_alignment());
56 if (MetaspaceSize > MaxMetaspaceSize) {
57 MetaspaceSize = MaxMetaspaceSize;
58 }
59
60 MinMetaspaceExpansion = MAX2(min_alignment(), align_size_down_(MinMetaspaceExpansion, min_alignment()));
61 MaxMetaspaceExpansion = MAX2(min_alignment(), align_size_down_(MaxMetaspaceExpansion, min_alignment()));
62
63 MinHeapDeltaBytes = align_size_up(MinHeapDeltaBytes, min_alignment());
64
65 assert(MetaspaceSize % min_alignment() == 0, "metapace alignment");
66 assert(MaxMetaspaceSize % max_alignment() == 0, "maximum metaspace alignment");
67 if (MetaspaceSize < 256*K) {
68 vm_exit_during_initialization("Too small initial Metaspace size");
69 }
70 }
71
72 void CollectorPolicy::initialize_size_info() {
73 // User inputs from -mx and ms are aligned
74 set_initial_heap_byte_size(InitialHeapSize);
75 if (initial_heap_byte_size() == 0) {
76 set_initial_heap_byte_size(NewSize + OldSize);
77 }
78 set_initial_heap_byte_size(align_size_up(_initial_heap_byte_size,
79 min_alignment()));
80
81 set_min_heap_byte_size(Arguments::min_heap_size());
82 if (min_heap_byte_size() == 0) {
83 set_min_heap_byte_size(NewSize + OldSize);
84 }
85 set_min_heap_byte_size(align_size_up(_min_heap_byte_size,
86 min_alignment()));
87
88 set_max_heap_byte_size(align_size_up(MaxHeapSize, max_alignment()));
89
90 // Check heap parameter properties
91 if (initial_heap_byte_size() < M) {
92 vm_exit_during_initialization("Too small initial heap");
93 }
94 // Check heap parameter properties
95 if (min_heap_byte_size() < M) {
96 vm_exit_during_initialization("Too small minimum heap");
97 }
98 if (initial_heap_byte_size() <= NewSize) {
99 // make sure there is at least some room in old space
100 vm_exit_during_initialization("Too small initial heap for new size specified");
101 }
102 if (max_heap_byte_size() < min_heap_byte_size()) {
103 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified");
104 }
105 if (initial_heap_byte_size() < min_heap_byte_size()) {
106 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified");
107 }
108 if (max_heap_byte_size() < initial_heap_byte_size()) {
109 vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
110 }
111
112 if (PrintGCDetails && Verbose) {
113 gclog_or_tty->print_cr("Minimum heap " SIZE_FORMAT " Initial heap "
114 SIZE_FORMAT " Maximum heap " SIZE_FORMAT,
115 min_heap_byte_size(), initial_heap_byte_size(), max_heap_byte_size());
116 }
117 }
118
119 bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) {
120 bool result = _should_clear_all_soft_refs;
121 set_should_clear_all_soft_refs(false);
122 return result;
123 }
124
125 GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap,
126 int max_covered_regions) {
127 switch (rem_set_name()) {
128 case GenRemSet::CardTable: {
129 CardTableRS* res = new CardTableRS(whole_heap, max_covered_regions);
130 return res;
131 }
132 default:
133 guarantee(false, "unrecognized GenRemSet::Name");
134 return NULL;
135 }
136 }
137
138 void CollectorPolicy::cleared_all_soft_refs() {
139 // If near gc overhear limit, continue to clear SoftRefs. SoftRefs may
140 // have been cleared in the last collection but if the gc overhear
141 // limit continues to be near, SoftRefs should still be cleared.
142 if (size_policy() != NULL) {
143 _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near();
144 }
145 _all_soft_refs_clear = true;
146 }
147
148
149 // GenCollectorPolicy methods.
150
151 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {
152 size_t x = base_size / (NewRatio+1);
153 size_t new_gen_size = x > min_alignment() ?
154 align_size_down(x, min_alignment()) :
155 min_alignment();
156 return new_gen_size;
157 }
158
159 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,
160 size_t maximum_size) {
161 size_t alignment = min_alignment();
162 size_t max_minus = maximum_size - alignment;
163 return desired_size < max_minus ? desired_size : max_minus;
164 }
165
166
167 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size,
168 size_t init_promo_size,
169 size_t init_survivor_size) {
170 const double max_gc_minor_pause_sec = ((double) MaxGCMinorPauseMillis)/1000.0;
171 _size_policy = new AdaptiveSizePolicy(init_eden_size,
172 init_promo_size,
173 init_survivor_size,
174 max_gc_minor_pause_sec,
175 GCTimeRatio);
176 }
177
178 size_t GenCollectorPolicy::compute_max_alignment() {
179 // The card marking array and the offset arrays for old generations are
180 // committed in os pages as well. Make sure they are entirely full (to
181 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
182 // byte entry and the os page size is 4096, the maximum heap size should
183 // be 512*4096 = 2MB aligned.
184 size_t alignment = GenRemSet::max_alignment_constraint(rem_set_name());
185
186 // Parallel GC does its own alignment of the generations to avoid requiring a
187 // large page (256M on some platforms) for the permanent generation. The
188 // other collectors should also be updated to do their own alignment and then
189 // this use of lcm() should be removed.
190 if (UseLargePages && !UseParallelGC) {
191 // in presence of large pages we have to make sure that our
192 // alignment is large page aware
193 alignment = lcm(os::large_page_size(), alignment);
194 }
195
196 return alignment;
197 }
198
199 void GenCollectorPolicy::initialize_flags() {
200 // All sizes must be multiples of the generation granularity.
201 set_min_alignment((uintx) Generation::GenGrain);
202 set_max_alignment(compute_max_alignment());
203 assert(max_alignment() >= min_alignment() &&
204 max_alignment() % min_alignment() == 0,
205 "invalid alignment constraints");
206
207 CollectorPolicy::initialize_flags();
208
209 // All generational heaps have a youngest gen; handle those flags here.
210
211 // Adjust max size parameters
212 if (NewSize > MaxNewSize) {
213 MaxNewSize = NewSize;
214 }
215 NewSize = align_size_down(NewSize, min_alignment());
216 MaxNewSize = align_size_down(MaxNewSize, min_alignment());
217
218 // Check validity of heap flags
219 assert(NewSize % min_alignment() == 0, "eden space alignment");
220 assert(MaxNewSize % min_alignment() == 0, "survivor space alignment");
221
222 if (NewSize < 3*min_alignment()) {
223 // make sure there room for eden and two survivor spaces
224 vm_exit_during_initialization("Too small new size specified");
225 }
226 if (SurvivorRatio < 1 || NewRatio < 1) {
227 vm_exit_during_initialization("Invalid heap ratio specified");
228 }
229 }
230
231 void TwoGenerationCollectorPolicy::initialize_flags() {
232 GenCollectorPolicy::initialize_flags();
233
234 OldSize = align_size_down(OldSize, min_alignment());
235 if (NewSize + OldSize > MaxHeapSize) {
236 MaxHeapSize = NewSize + OldSize;
237 }
238 MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
239
240 always_do_update_barrier = UseConcMarkSweepGC;
241
242 // Check validity of heap flags
243 assert(OldSize % min_alignment() == 0, "old space alignment");
244 assert(MaxHeapSize % max_alignment() == 0, "maximum heap alignment");
245 }
246
247 // Values set on the command line win over any ergonomically
248 // set command line parameters.
249 // Ergonomic choice of parameters are done before this
250 // method is called. Values for command line parameters such as NewSize
251 // and MaxNewSize feed those ergonomic choices into this method.
252 // This method makes the final generation sizings consistent with
253 // themselves and with overall heap sizings.
254 // In the absence of explicitly set command line flags, policies
255 // such as the use of NewRatio are used to size the generation.
256 void GenCollectorPolicy::initialize_size_info() {
257 CollectorPolicy::initialize_size_info();
258
259 // min_alignment() is used for alignment within a generation.
260 // There is additional alignment done down stream for some
261 // collectors that sometimes causes unwanted rounding up of
262 // generations sizes.
263
264 // Determine maximum size of gen0
265
266 size_t max_new_size = 0;
267 if (FLAG_IS_CMDLINE(MaxNewSize) || FLAG_IS_ERGO(MaxNewSize)) {
268 if (MaxNewSize < min_alignment()) {
269 max_new_size = min_alignment();
270 }
271 if (MaxNewSize >= max_heap_byte_size()) {
272 max_new_size = align_size_down(max_heap_byte_size() - min_alignment(),
273 min_alignment());
274 warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or "
275 "greater than the entire heap (" SIZE_FORMAT "k). A "
276 "new generation size of " SIZE_FORMAT "k will be used.",
277 MaxNewSize/K, max_heap_byte_size()/K, max_new_size/K);
278 } else {
279 max_new_size = align_size_down(MaxNewSize, min_alignment());
280 }
281
282 // The case for FLAG_IS_ERGO(MaxNewSize) could be treated
283 // specially at this point to just use an ergonomically set
284 // MaxNewSize to set max_new_size. For cases with small
285 // heaps such a policy often did not work because the MaxNewSize
286 // was larger than the entire heap. The interpretation given
287 // to ergonomically set flags is that the flags are set
288 // by different collectors for their own special needs but
289 // are not allowed to badly shape the heap. This allows the
290 // different collectors to decide what's best for themselves
291 // without having to factor in the overall heap shape. It
292 // can be the case in the future that the collectors would
293 // only make "wise" ergonomics choices and this policy could
294 // just accept those choices. The choices currently made are
295 // not always "wise".
296 } else {
297 max_new_size = scale_by_NewRatio_aligned(max_heap_byte_size());
298 // Bound the maximum size by NewSize below (since it historically
299 // would have been NewSize and because the NewRatio calculation could
300 // yield a size that is too small) and bound it by MaxNewSize above.
301 // Ergonomics plays here by previously calculating the desired
302 // NewSize and MaxNewSize.
303 max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize);
304 }
305 assert(max_new_size > 0, "All paths should set max_new_size");
306
307 // Given the maximum gen0 size, determine the initial and
308 // minimum gen0 sizes.
309
310 if (max_heap_byte_size() == min_heap_byte_size()) {
311 // The maximum and minimum heap sizes are the same so
312 // the generations minimum and initial must be the
313 // same as its maximum.
314 set_min_gen0_size(max_new_size);
315 set_initial_gen0_size(max_new_size);
316 set_max_gen0_size(max_new_size);
317 } else {
318 size_t desired_new_size = 0;
319 if (!FLAG_IS_DEFAULT(NewSize)) {
320 // If NewSize is set ergonomically (for example by cms), it
321 // would make sense to use it. If it is used, also use it
322 // to set the initial size. Although there is no reason
323 // the minimum size and the initial size have to be the same,
324 // the current implementation gets into trouble during the calculation
325 // of the tenured generation sizes if they are different.
326 // Note that this makes the initial size and the minimum size
327 // generally small compared to the NewRatio calculation.
328 _min_gen0_size = NewSize;
329 desired_new_size = NewSize;
330 max_new_size = MAX2(max_new_size, NewSize);
331 } else {
332 // For the case where NewSize is the default, use NewRatio
333 // to size the minimum and initial generation sizes.
334 // Use the default NewSize as the floor for these values. If
335 // NewRatio is overly large, the resulting sizes can be too
336 // small.
337 _min_gen0_size = MAX2(scale_by_NewRatio_aligned(min_heap_byte_size()),
338 NewSize);
339 desired_new_size =
340 MAX2(scale_by_NewRatio_aligned(initial_heap_byte_size()),
341 NewSize);
342 }
343
344 assert(_min_gen0_size > 0, "Sanity check");
345 set_initial_gen0_size(desired_new_size);
346 set_max_gen0_size(max_new_size);
347
348 // At this point the desirable initial and minimum sizes have been
349 // determined without regard to the maximum sizes.
350
351 // Bound the sizes by the corresponding overall heap sizes.
352 set_min_gen0_size(
353 bound_minus_alignment(_min_gen0_size, min_heap_byte_size()));
354 set_initial_gen0_size(
355 bound_minus_alignment(_initial_gen0_size, initial_heap_byte_size()));
356 set_max_gen0_size(
357 bound_minus_alignment(_max_gen0_size, max_heap_byte_size()));
358
359 // At this point all three sizes have been checked against the
360 // maximum sizes but have not been checked for consistency
361 // among the three.
362
363 // Final check min <= initial <= max
364 set_min_gen0_size(MIN2(_min_gen0_size, _max_gen0_size));
365 set_initial_gen0_size(
366 MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size));
367 set_min_gen0_size(MIN2(_min_gen0_size, _initial_gen0_size));
368 }
369
370 if (PrintGCDetails && Verbose) {
371 gclog_or_tty->print_cr("1: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
372 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
373 min_gen0_size(), initial_gen0_size(), max_gen0_size());
374 }
375 }
376
377 // Call this method during the sizing of the gen1 to make
378 // adjustments to gen0 because of gen1 sizing policy. gen0 initially has
379 // the most freedom in sizing because it is done before the
380 // policy for gen1 is applied. Once gen1 policies have been applied,
381 // there may be conflicts in the shape of the heap and this method
382 // is used to make the needed adjustments. The application of the
383 // policies could be more sophisticated (iterative for example) but
384 // keeping it simple also seems a worthwhile goal.
385 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr,
386 size_t* gen1_size_ptr,
387 size_t heap_size,
388 size_t min_gen0_size) {
389 bool result = false;
390 if ((*gen1_size_ptr + *gen0_size_ptr) > heap_size) {
391 if (((*gen0_size_ptr + OldSize) > heap_size) &&
392 (heap_size - min_gen0_size) >= min_alignment()) {
393 // Adjust gen0 down to accomodate OldSize
394 *gen0_size_ptr = heap_size - min_gen0_size;
395 *gen0_size_ptr =
396 MAX2((uintx)align_size_down(*gen0_size_ptr, min_alignment()),
397 min_alignment());
398 assert(*gen0_size_ptr > 0, "Min gen0 is too large");
399 result = true;
400 } else {
401 *gen1_size_ptr = heap_size - *gen0_size_ptr;
402 *gen1_size_ptr =
403 MAX2((uintx)align_size_down(*gen1_size_ptr, min_alignment()),
404 min_alignment());
405 }
406 }
407 return result;
408 }
409
410 // Minimum sizes of the generations may be different than
411 // the initial sizes. An inconsistently is permitted here
412 // in the total size that can be specified explicitly by
413 // command line specification of OldSize and NewSize and
414 // also a command line specification of -Xms. Issue a warning
415 // but allow the values to pass.
416
417 void TwoGenerationCollectorPolicy::initialize_size_info() {
418 GenCollectorPolicy::initialize_size_info();
419
420 // At this point the minimum, initial and maximum sizes
421 // of the overall heap and of gen0 have been determined.
422 // The maximum gen1 size can be determined from the maximum gen0
423 // and maximum heap size since no explicit flags exits
424 // for setting the gen1 maximum.
425 _max_gen1_size = max_heap_byte_size() - _max_gen0_size;
426 _max_gen1_size =
427 MAX2((uintx)align_size_down(_max_gen1_size, min_alignment()),
428 min_alignment());
429 // If no explicit command line flag has been set for the
430 // gen1 size, use what is left for gen1.
431 if (FLAG_IS_DEFAULT(OldSize) || FLAG_IS_ERGO(OldSize)) {
432 // The user has not specified any value or ergonomics
433 // has chosen a value (which may or may not be consistent
434 // with the overall heap size). In either case make
435 // the minimum, maximum and initial sizes consistent
436 // with the gen0 sizes and the overall heap sizes.
437 assert(min_heap_byte_size() > _min_gen0_size,
438 "gen0 has an unexpected minimum size");
439 set_min_gen1_size(min_heap_byte_size() - min_gen0_size());
440 set_min_gen1_size(
441 MAX2((uintx)align_size_down(_min_gen1_size, min_alignment()),
442 min_alignment()));
443 set_initial_gen1_size(initial_heap_byte_size() - initial_gen0_size());
444 set_initial_gen1_size(
445 MAX2((uintx)align_size_down(_initial_gen1_size, min_alignment()),
446 min_alignment()));
447
448 } else {
449 // It's been explicitly set on the command line. Use the
450 // OldSize and then determine the consequences.
451 set_min_gen1_size(OldSize);
452 set_initial_gen1_size(OldSize);
453
454 // If the user has explicitly set an OldSize that is inconsistent
455 // with other command line flags, issue a warning.
456 // The generation minimums and the overall heap mimimum should
457 // be within one heap alignment.
458 if ((_min_gen1_size + _min_gen0_size + min_alignment()) <
459 min_heap_byte_size()) {
460 warning("Inconsistency between minimum heap size and minimum "
461 "generation sizes: using minimum heap = " SIZE_FORMAT,
462 min_heap_byte_size());
463 }
464 if ((OldSize > _max_gen1_size)) {
465 warning("Inconsistency between maximum heap size and maximum "
466 "generation sizes: using maximum heap = " SIZE_FORMAT
467 " -XX:OldSize flag is being ignored",
468 max_heap_byte_size());
469 }
470 // If there is an inconsistency between the OldSize and the minimum and/or
471 // initial size of gen0, since OldSize was explicitly set, OldSize wins.
472 if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size,
473 min_heap_byte_size(), OldSize)) {
474 if (PrintGCDetails && Verbose) {
475 gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
476 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
477 min_gen0_size(), initial_gen0_size(), max_gen0_size());
478 }
479 }
480 // Initial size
481 if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,
482 initial_heap_byte_size(), OldSize)) {
483 if (PrintGCDetails && Verbose) {
484 gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
485 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
486 min_gen0_size(), initial_gen0_size(), max_gen0_size());
487 }
488 }
489 }
490 // Enforce the maximum gen1 size.
491 set_min_gen1_size(MIN2(_min_gen1_size, _max_gen1_size));
492
493 // Check that min gen1 <= initial gen1 <= max gen1
494 set_initial_gen1_size(MAX2(_initial_gen1_size, _min_gen1_size));
495 set_initial_gen1_size(MIN2(_initial_gen1_size, _max_gen1_size));
496
497 if (PrintGCDetails && Verbose) {
498 gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 "
499 SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT,
500 min_gen1_size(), initial_gen1_size(), max_gen1_size());
501 }
502 }
503
504 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
505 bool is_tlab,
506 bool* gc_overhead_limit_was_exceeded) {
507 GenCollectedHeap *gch = GenCollectedHeap::heap();
508
509 debug_only(gch->check_for_valid_allocation_state());
510 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
511
512 // In general gc_overhead_limit_was_exceeded should be false so
513 // set it so here and reset it to true only if the gc time
514 // limit is being exceeded as checked below.
515 *gc_overhead_limit_was_exceeded = false;
516
517 HeapWord* result = NULL;
518
519 // Loop until the allocation is satisified,
520 // or unsatisfied after GC.
521 for (int try_count = 1; /* return or throw */; try_count += 1) {
522 HandleMark hm; // discard any handles allocated in each iteration
523
524 // First allocation attempt is lock-free.
525 Generation *gen0 = gch->get_gen(0);
526 assert(gen0->supports_inline_contig_alloc(),
527 "Otherwise, must do alloc within heap lock");
528 if (gen0->should_allocate(size, is_tlab)) {
529 result = gen0->par_allocate(size, is_tlab);
530 if (result != NULL) {
531 assert(gch->is_in_reserved(result), "result not in heap");
532 return result;
533 }
534 }
535 unsigned int gc_count_before; // read inside the Heap_lock locked region
536 {
537 MutexLocker ml(Heap_lock);
538 if (PrintGC && Verbose) {
539 gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:"
540 " attempting locked slow path allocation");
541 }
542 // Note that only large objects get a shot at being
543 // allocated in later generations.
544 bool first_only = ! should_try_older_generation_allocation(size);
545
546 result = gch->attempt_allocation(size, is_tlab, first_only);
547 if (result != NULL) {
548 assert(gch->is_in_reserved(result), "result not in heap");
549 return result;
550 }
551
552 if (GC_locker::is_active_and_needs_gc()) {
553 if (is_tlab) {
554 return NULL; // Caller will retry allocating individual object
555 }
556 if (!gch->is_maximal_no_gc()) {
557 // Try and expand heap to satisfy request
558 result = expand_heap_and_allocate(size, is_tlab);
559 // result could be null if we are out of space
560 if (result != NULL) {
561 return result;
562 }
563 }
564
565 // If this thread is not in a jni critical section, we stall
566 // the requestor until the critical section has cleared and
567 // GC allowed. When the critical section clears, a GC is
568 // initiated by the last thread exiting the critical section; so
569 // we retry the allocation sequence from the beginning of the loop,
570 // rather than causing more, now probably unnecessary, GC attempts.
571 JavaThread* jthr = JavaThread::current();
572 if (!jthr->in_critical()) {
573 MutexUnlocker mul(Heap_lock);
574 // Wait for JNI critical section to be exited
575 GC_locker::stall_until_clear();
576 continue;
577 } else {
578 if (CheckJNICalls) {
579 fatal("Possible deadlock due to allocating while"
580 " in jni critical section");
581 }
582 return NULL;
583 }
584 }
585
586 // Read the gc count while the heap lock is held.
587 gc_count_before = Universe::heap()->total_collections();
588 }
589
590 VM_GenCollectForAllocation op(size,
591 is_tlab,
592 gc_count_before);
593 VMThread::execute(&op);
594 if (op.prologue_succeeded()) {
595 result = op.result();
596 if (op.gc_locked()) {
597 assert(result == NULL, "must be NULL if gc_locked() is true");
598 continue; // retry and/or stall as necessary
599 }
600
601 // Allocation has failed and a collection
602 // has been done. If the gc time limit was exceeded the
603 // this time, return NULL so that an out-of-memory
604 // will be thrown. Clear gc_overhead_limit_exceeded
605 // so that the overhead exceeded does not persist.
606
607 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
608 const bool softrefs_clear = all_soft_refs_clear();
609 assert(!limit_exceeded || softrefs_clear, "Should have been cleared");
610 if (limit_exceeded && softrefs_clear) {
611 *gc_overhead_limit_was_exceeded = true;
612 size_policy()->set_gc_overhead_limit_exceeded(false);
613 if (op.result() != NULL) {
614 CollectedHeap::fill_with_object(op.result(), size);
615 }
616 return NULL;
617 }
618 assert(result == NULL || gch->is_in_reserved(result),
619 "result not in heap");
620 return result;
621 }
622
623 // Give a warning if we seem to be looping forever.
624 if ((QueuedAllocationWarningCount > 0) &&
625 (try_count % QueuedAllocationWarningCount == 0)) {
626 warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t"
627 " size=%d %s", try_count, size, is_tlab ? "(TLAB)" : "");
628 }
629 }
630 }
631
632 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size,
633 bool is_tlab) {
634 GenCollectedHeap *gch = GenCollectedHeap::heap();
635 HeapWord* result = NULL;
636 for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) {
637 Generation *gen = gch->get_gen(i);
638 if (gen->should_allocate(size, is_tlab)) {
639 result = gen->expand_and_allocate(size, is_tlab);
640 }
641 }
642 assert(result == NULL || gch->is_in_reserved(result), "result not in heap");
643 return result;
644 }
645
646 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size,
647 bool is_tlab) {
648 GenCollectedHeap *gch = GenCollectedHeap::heap();
649 GCCauseSetter x(gch, GCCause::_allocation_failure);
650 HeapWord* result = NULL;
651
652 assert(size != 0, "Precondition violated");
653 if (GC_locker::is_active_and_needs_gc()) {
654 // GC locker is active; instead of a collection we will attempt
655 // to expand the heap, if there's room for expansion.
656 if (!gch->is_maximal_no_gc()) {
657 result = expand_heap_and_allocate(size, is_tlab);
658 }
659 return result; // could be null if we are out of space
660 } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) {
661 // Do an incremental collection.
662 gch->do_collection(false /* full */,
663 false /* clear_all_soft_refs */,
664 size /* size */,
665 is_tlab /* is_tlab */,
666 number_of_generations() - 1 /* max_level */);
667 } else {
668 if (Verbose && PrintGCDetails) {
669 gclog_or_tty->print(" :: Trying full because partial may fail :: ");
670 }
671 // Try a full collection; see delta for bug id 6266275
672 // for the original code and why this has been simplified
673 // with from-space allocation criteria modified and
674 // such allocation moved out of the safepoint path.
675 gch->do_collection(true /* full */,
676 false /* clear_all_soft_refs */,
677 size /* size */,
678 is_tlab /* is_tlab */,
679 number_of_generations() - 1 /* max_level */);
680 }
681
682 result = gch->attempt_allocation(size, is_tlab, false /*first_only*/);
683
684 if (result != NULL) {
685 assert(gch->is_in_reserved(result), "result not in heap");
686 return result;
687 }
688
689 // OK, collection failed, try expansion.
690 result = expand_heap_and_allocate(size, is_tlab);
691 if (result != NULL) {
692 return result;
693 }
694
695 // If we reach this point, we're really out of memory. Try every trick
696 // we can to reclaim memory. Force collection of soft references. Force
697 // a complete compaction of the heap. Any additional methods for finding
698 // free memory should be here, especially if they are expensive. If this
699 // attempt fails, an OOM exception will be thrown.
700 {
701 IntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
702
703 gch->do_collection(true /* full */,
704 true /* clear_all_soft_refs */,
705 size /* size */,
706 is_tlab /* is_tlab */,
707 number_of_generations() - 1 /* max_level */);
708 }
709
710 result = gch->attempt_allocation(size, is_tlab, false /* first_only */);
711 if (result != NULL) {
712 assert(gch->is_in_reserved(result), "result not in heap");
713 return result;
714 }
715
716 assert(!should_clear_all_soft_refs(),
717 "Flag should have been handled and cleared prior to this point");
718
719 // What else? We might try synchronous finalization later. If the total
720 // space available is large enough for the allocation, then a more
721 // complete compaction phase than we've tried so far might be
722 // appropriate.
723 return NULL;
724 }
725
726 MetaWord* CollectorPolicy::satisfy_failed_metadata_allocation(
727 ClassLoaderData* loader_data,
728 size_t word_size,
729 Metaspace::MetadataType mdtype) {
730 uint loop_count = 0;
731 uint gc_count = 0;
732 uint full_gc_count = 0;
733
734 assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock");
735
736 do {
737 MetaWord* result = NULL;
738 if (GC_locker::is_active_and_needs_gc()) {
739 // If the GC_locker is active, just expand and allocate.
740 // If that does not succeed, wait if this thread is not
741 // in a critical section itself.
742 result =
743 loader_data->metaspace_non_null()->expand_and_allocate(word_size,
744 mdtype);
745 if (result != NULL) {
746 return result;
747 }
748 JavaThread* jthr = JavaThread::current();
749 if (!jthr->in_critical()) {
750 // Wait for JNI critical section to be exited
751 GC_locker::stall_until_clear();
752 // The GC invoked by the last thread leaving the critical
753 // section will be a young collection and a full collection
754 // is (currently) needed for unloading classes so continue
755 // to the next iteration to get a full GC.
756 continue;
757 } else {
758 if (CheckJNICalls) {
759 fatal("Possible deadlock due to allocating while"
760 " in jni critical section");
761 }
762 return NULL;
763 }
764 }
765
766 { // Need lock to get self consistent gc_count's
767 MutexLocker ml(Heap_lock);
768 gc_count = Universe::heap()->total_collections();
769 full_gc_count = Universe::heap()->total_full_collections();
770 }
771
772 // Generate a VM operation
773 VM_CollectForMetadataAllocation op(loader_data,
774 word_size,
775 mdtype,
776 gc_count,
777 full_gc_count,
778 GCCause::_metadata_GC_threshold);
779 VMThread::execute(&op);
780 if (op.prologue_succeeded()) {
781 return op.result();
782 }
783 loop_count++;
784 if ((QueuedAllocationWarningCount > 0) &&
785 (loop_count % QueuedAllocationWarningCount == 0)) {
786 warning("satisfy_failed_metadata_allocation() retries %d times \n\t"
787 " size=%d", loop_count, word_size);
788 }
789 } while (true); // Until a GC is done
790 }
791
792 // Return true if any of the following is true:
793 // . the allocation won't fit into the current young gen heap
794 // . gc locker is occupied (jni critical section)
795 // . heap memory is tight -- the most recent previous collection
796 // was a full collection because a partial collection (would
797 // have) failed and is likely to fail again
798 bool GenCollectorPolicy::should_try_older_generation_allocation(
799 size_t word_size) const {
800 GenCollectedHeap* gch = GenCollectedHeap::heap();
801 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();
802 return (word_size > heap_word_size(gen0_capacity))
803 || GC_locker::is_active_and_needs_gc()
804 || gch->incremental_collection_failed();
805 }
806
807
808 //
809 // MarkSweepPolicy methods
810 //
811
812 MarkSweepPolicy::MarkSweepPolicy() {
813 initialize_all();
814 }
815
816 void MarkSweepPolicy::initialize_generations() {
817 _generations = new GenerationSpecPtr[number_of_generations()];
818 if (_generations == NULL)
819 vm_exit_during_initialization("Unable to allocate gen spec");
820
821 if (UseParNewGC && ParallelGCThreads > 0) {
822 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);
823 } else {
824 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);
825 }
826 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);
827
828 if (_generations[0] == NULL || _generations[1] == NULL)
829 vm_exit_during_initialization("Unable to allocate gen spec");
830 }
831
832 void MarkSweepPolicy::initialize_gc_policy_counters() {
833 // initialize the policy counters - 2 collectors, 3 generations
834 if (UseParNewGC && ParallelGCThreads > 0) {
835 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);
836 }
837 else {
838 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
839 }
840 }