1 /*
2 * Copyright (c) 2001, 2013, 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 #include "utilities/macros.hpp"
43 #if INCLUDE_ALL_GCS
44 #include "gc_implementation/concurrentMarkSweep/cmsAdaptiveSizePolicy.hpp"
45 #include "gc_implementation/concurrentMarkSweep/cmsGCAdaptivePolicyCounters.hpp"
46 #endif // INCLUDE_ALL_GCS
47
48 // CollectorPolicy methods.
49
50 void CollectorPolicy::initialize_flags() {
51 if (MetaspaceSize > MaxMetaspaceSize) {
52 MaxMetaspaceSize = MetaspaceSize;
53 }
54 MetaspaceSize = MAX2(min_alignment(), align_size_down_(MetaspaceSize, min_alignment()));
55 // Don't increase Metaspace size limit above specified.
56 MaxMetaspaceSize = align_size_down(MaxMetaspaceSize, max_alignment());
57 if (MetaspaceSize > MaxMetaspaceSize) {
58 MetaspaceSize = MaxMetaspaceSize;
59 }
60
61 MinMetaspaceExpansion = MAX2(min_alignment(), align_size_down_(MinMetaspaceExpansion, min_alignment()));
62 MaxMetaspaceExpansion = MAX2(min_alignment(), align_size_down_(MaxMetaspaceExpansion, min_alignment()));
63
64 MinHeapDeltaBytes = align_size_up(MinHeapDeltaBytes, min_alignment());
65
66 assert(MetaspaceSize % min_alignment() == 0, "metapace alignment");
67 assert(MaxMetaspaceSize % max_alignment() == 0, "maximum metaspace alignment");
68 if (MetaspaceSize < 256*K) {
69 vm_exit_during_initialization("Too small initial Metaspace size");
70 }
71 }
72
73 void CollectorPolicy::initialize_size_info() {
74 // User inputs from -mx and ms are aligned
75 set_initial_heap_byte_size(InitialHeapSize);
76 if (initial_heap_byte_size() == 0) {
77 set_initial_heap_byte_size(NewSize + OldSize);
78 }
79 set_initial_heap_byte_size(align_size_up(_initial_heap_byte_size,
80 min_alignment()));
81
82 set_min_heap_byte_size(Arguments::min_heap_size());
83 if (min_heap_byte_size() == 0) {
84 set_min_heap_byte_size(NewSize + OldSize);
85 }
86 set_min_heap_byte_size(align_size_up(_min_heap_byte_size,
87 min_alignment()));
88
89 set_max_heap_byte_size(align_size_up(MaxHeapSize, max_alignment()));
90
91 // Check heap parameter properties
92 if (initial_heap_byte_size() < M) {
93 vm_exit_during_initialization("Too small initial heap");
94 }
95 // Check heap parameter properties
96 if (min_heap_byte_size() < M) {
97 vm_exit_during_initialization("Too small minimum heap");
98 }
99 if (initial_heap_byte_size() <= NewSize) {
100 // make sure there is at least some room in old space
101 vm_exit_during_initialization("Too small initial heap for new size specified");
102 }
103 if (max_heap_byte_size() < min_heap_byte_size()) {
104 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified");
105 }
106 if (initial_heap_byte_size() < min_heap_byte_size()) {
107 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified");
108 }
109 if (max_heap_byte_size() < initial_heap_byte_size()) {
110 vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
111 }
112
113 if (PrintGCDetails && Verbose) {
114 gclog_or_tty->print_cr("Minimum heap " SIZE_FORMAT " Initial heap "
115 SIZE_FORMAT " Maximum heap " SIZE_FORMAT,
116 min_heap_byte_size(), initial_heap_byte_size(), max_heap_byte_size());
117 }
118 }
119
120 bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) {
121 bool result = _should_clear_all_soft_refs;
122 set_should_clear_all_soft_refs(false);
123 return result;
124 }
125
126 GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap,
127 int max_covered_regions) {
128 switch (rem_set_name()) {
129 case GenRemSet::CardTable: {
130 CardTableRS* res = new CardTableRS(whole_heap, max_covered_regions);
131 return res;
132 }
133 default:
134 guarantee(false, "unrecognized GenRemSet::Name");
135 return NULL;
136 }
137 }
138
139 void CollectorPolicy::cleared_all_soft_refs() {
140 // If near gc overhear limit, continue to clear SoftRefs. SoftRefs may
141 // have been cleared in the last collection but if the gc overhear
142 // limit continues to be near, SoftRefs should still be cleared.
143 if (size_policy() != NULL) {
144 _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near();
145 }
146 _all_soft_refs_clear = true;
147 }
148
149
150 // GenCollectorPolicy methods.
151
152 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {
153 size_t x = base_size / (NewRatio+1);
154 size_t new_gen_size = x > min_alignment() ?
155 align_size_down(x, min_alignment()) :
156 min_alignment();
157 return new_gen_size;
158 }
159
160 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,
161 size_t maximum_size) {
162 size_t alignment = min_alignment();
163 size_t max_minus = maximum_size - alignment;
164 return desired_size < max_minus ? desired_size : max_minus;
165 }
166
167
168 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size,
169 size_t init_promo_size,
170 size_t init_survivor_size) {
171 const double max_gc_pause_sec = ((double) MaxGCPauseMillis)/1000.0;
172 _size_policy = new AdaptiveSizePolicy(init_eden_size,
173 init_promo_size,
174 init_survivor_size,
175 max_gc_pause_sec,
176 GCTimeRatio);
177 }
178
179 size_t GenCollectorPolicy::compute_max_alignment() {
180 // The card marking array and the offset arrays for old generations are
181 // committed in os pages as well. Make sure they are entirely full (to
182 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
183 // byte entry and the os page size is 4096, the maximum heap size should
184 // be 512*4096 = 2MB aligned.
185 size_t alignment = GenRemSet::max_alignment_constraint(rem_set_name());
186
187 // Parallel GC does its own alignment of the generations to avoid requiring a
188 // large page (256M on some platforms) for the permanent generation. The
189 // other collectors should also be updated to do their own alignment and then
190 // this use of lcm() should be removed.
191 if (UseLargePages && !UseParallelGC) {
192 // in presence of large pages we have to make sure that our
193 // alignment is large page aware
194 alignment = lcm(os::large_page_size(), alignment);
195 }
196
197 return alignment;
198 }
199
200 void GenCollectorPolicy::initialize_flags() {
201 // All sizes must be multiples of the generation granularity.
202 set_min_alignment((uintx) Generation::GenGrain);
203 set_max_alignment(compute_max_alignment());
204 assert(max_alignment() >= min_alignment() &&
205 max_alignment() % min_alignment() == 0,
206 "invalid alignment constraints");
207
208 CollectorPolicy::initialize_flags();
209
210 // All generational heaps have a youngest gen; handle those flags here.
211
212 // Adjust max size parameters
213 if (NewSize > MaxNewSize) {
214 MaxNewSize = NewSize;
215 }
216 NewSize = align_size_down(NewSize, min_alignment());
217 MaxNewSize = align_size_down(MaxNewSize, min_alignment());
218
219 // Check validity of heap flags
220 assert(NewSize % min_alignment() == 0, "eden space alignment");
221 assert(MaxNewSize % min_alignment() == 0, "survivor space alignment");
222
223 if (NewSize < 3*min_alignment()) {
224 // make sure there room for eden and two survivor spaces
225 vm_exit_during_initialization("Too small new size specified");
226 }
227 if (SurvivorRatio < 1 || NewRatio < 1) {
228 vm_exit_during_initialization("Invalid heap ratio specified");
229 }
230 }
231
232 void TwoGenerationCollectorPolicy::initialize_flags() {
233 GenCollectorPolicy::initialize_flags();
234
235 OldSize = align_size_down(OldSize, min_alignment());
236 if (NewSize + OldSize > MaxHeapSize) {
237 MaxHeapSize = NewSize + OldSize;
238 }
239
240 if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(NewSize)) {
241 // NewRatio will be used later to set the young generation size so we use
242 // it to calculate how big the heap should be based on the requested OldSize
243 // and NewRatio.
244 assert(NewRatio > 0, "NewRatio should have been set up earlier");
245 size_t calculated_heapsize = (OldSize / NewRatio) * (NewRatio + 1);
246
247 calculated_heapsize = align_size_up(calculated_heapsize, max_alignment());
248 MaxHeapSize = calculated_heapsize;
249 InitialHeapSize = calculated_heapsize;
250 }
251 MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
252
253 always_do_update_barrier = UseConcMarkSweepGC;
254
255 // Check validity of heap flags
256 assert(OldSize % min_alignment() == 0, "old space alignment");
257 assert(MaxHeapSize % max_alignment() == 0, "maximum heap alignment");
258 }
259
260 // Values set on the command line win over any ergonomically
261 // set command line parameters.
262 // Ergonomic choice of parameters are done before this
263 // method is called. Values for command line parameters such as NewSize
264 // and MaxNewSize feed those ergonomic choices into this method.
265 // This method makes the final generation sizings consistent with
266 // themselves and with overall heap sizings.
267 // In the absence of explicitly set command line flags, policies
268 // such as the use of NewRatio are used to size the generation.
269 void GenCollectorPolicy::initialize_size_info() {
270 CollectorPolicy::initialize_size_info();
271
272 // min_alignment() is used for alignment within a generation.
273 // There is additional alignment done down stream for some
274 // collectors that sometimes causes unwanted rounding up of
275 // generations sizes.
276
277 // Determine maximum size of gen0
278
279 size_t max_new_size = 0;
280 if (FLAG_IS_CMDLINE(MaxNewSize) || FLAG_IS_ERGO(MaxNewSize)) {
281 if (MaxNewSize < min_alignment()) {
282 max_new_size = min_alignment();
283 }
284 if (MaxNewSize >= max_heap_byte_size()) {
285 max_new_size = align_size_down(max_heap_byte_size() - min_alignment(),
286 min_alignment());
287 warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or "
288 "greater than the entire heap (" SIZE_FORMAT "k). A "
289 "new generation size of " SIZE_FORMAT "k will be used.",
290 MaxNewSize/K, max_heap_byte_size()/K, max_new_size/K);
291 } else {
292 max_new_size = align_size_down(MaxNewSize, min_alignment());
293 }
294
295 // The case for FLAG_IS_ERGO(MaxNewSize) could be treated
296 // specially at this point to just use an ergonomically set
297 // MaxNewSize to set max_new_size. For cases with small
298 // heaps such a policy often did not work because the MaxNewSize
299 // was larger than the entire heap. The interpretation given
300 // to ergonomically set flags is that the flags are set
301 // by different collectors for their own special needs but
302 // are not allowed to badly shape the heap. This allows the
303 // different collectors to decide what's best for themselves
304 // without having to factor in the overall heap shape. It
305 // can be the case in the future that the collectors would
306 // only make "wise" ergonomics choices and this policy could
307 // just accept those choices. The choices currently made are
308 // not always "wise".
309 } else {
310 max_new_size = scale_by_NewRatio_aligned(max_heap_byte_size());
311 // Bound the maximum size by NewSize below (since it historically
312 // would have been NewSize and because the NewRatio calculation could
313 // yield a size that is too small) and bound it by MaxNewSize above.
314 // Ergonomics plays here by previously calculating the desired
315 // NewSize and MaxNewSize.
316 max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize);
317 }
318 assert(max_new_size > 0, "All paths should set max_new_size");
319
320 // Given the maximum gen0 size, determine the initial and
321 // minimum gen0 sizes.
322
323 if (max_heap_byte_size() == min_heap_byte_size()) {
324 // The maximum and minimum heap sizes are the same so
325 // the generations minimum and initial must be the
326 // same as its maximum.
327 set_min_gen0_size(max_new_size);
328 set_initial_gen0_size(max_new_size);
329 set_max_gen0_size(max_new_size);
330 } else {
331 size_t desired_new_size = 0;
332 if (!FLAG_IS_DEFAULT(NewSize)) {
333 // If NewSize is set ergonomically (for example by cms), it
334 // would make sense to use it. If it is used, also use it
335 // to set the initial size. Although there is no reason
336 // the minimum size and the initial size have to be the same,
337 // the current implementation gets into trouble during the calculation
338 // of the tenured generation sizes if they are different.
339 // Note that this makes the initial size and the minimum size
340 // generally small compared to the NewRatio calculation.
341 _min_gen0_size = NewSize;
342 desired_new_size = NewSize;
343 max_new_size = MAX2(max_new_size, NewSize);
344 } else {
345 // For the case where NewSize is the default, use NewRatio
346 // to size the minimum and initial generation sizes.
347 // Use the default NewSize as the floor for these values. If
348 // NewRatio is overly large, the resulting sizes can be too
349 // small.
350 _min_gen0_size = MAX2(scale_by_NewRatio_aligned(min_heap_byte_size()),
351 NewSize);
352 desired_new_size =
353 MAX2(scale_by_NewRatio_aligned(initial_heap_byte_size()),
354 NewSize);
355 }
356
357 assert(_min_gen0_size > 0, "Sanity check");
358 set_initial_gen0_size(desired_new_size);
359 set_max_gen0_size(max_new_size);
360
361 // At this point the desirable initial and minimum sizes have been
362 // determined without regard to the maximum sizes.
363
364 // Bound the sizes by the corresponding overall heap sizes.
365 set_min_gen0_size(
366 bound_minus_alignment(_min_gen0_size, min_heap_byte_size()));
367 set_initial_gen0_size(
368 bound_minus_alignment(_initial_gen0_size, initial_heap_byte_size()));
369 set_max_gen0_size(
370 bound_minus_alignment(_max_gen0_size, max_heap_byte_size()));
371
372 // At this point all three sizes have been checked against the
373 // maximum sizes but have not been checked for consistency
374 // among the three.
375
376 // Final check min <= initial <= max
377 set_min_gen0_size(MIN2(_min_gen0_size, _max_gen0_size));
378 set_initial_gen0_size(
379 MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size));
380 set_min_gen0_size(MIN2(_min_gen0_size, _initial_gen0_size));
381 }
382
383 if (PrintGCDetails && Verbose) {
384 gclog_or_tty->print_cr("1: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
385 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
386 min_gen0_size(), initial_gen0_size(), max_gen0_size());
387 }
388 }
389
390 // Call this method during the sizing of the gen1 to make
391 // adjustments to gen0 because of gen1 sizing policy. gen0 initially has
392 // the most freedom in sizing because it is done before the
393 // policy for gen1 is applied. Once gen1 policies have been applied,
394 // there may be conflicts in the shape of the heap and this method
395 // is used to make the needed adjustments. The application of the
396 // policies could be more sophisticated (iterative for example) but
397 // keeping it simple also seems a worthwhile goal.
398 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr,
399 size_t* gen1_size_ptr,
400 const size_t heap_size,
401 const size_t min_gen1_size) {
402 bool result = false;
403
404 if ((*gen1_size_ptr + *gen0_size_ptr) > heap_size) {
405 if ((heap_size < (*gen0_size_ptr + min_gen1_size)) &&
406 (heap_size >= min_gen1_size + min_alignment())) {
407 // Adjust gen0 down to accommodate min_gen1_size
408 *gen0_size_ptr = heap_size - min_gen1_size;
409 *gen0_size_ptr =
410 MAX2((uintx)align_size_down(*gen0_size_ptr, min_alignment()),
411 min_alignment());
412 assert(*gen0_size_ptr > 0, "Min gen0 is too large");
413 result = true;
414 } else {
415 *gen1_size_ptr = heap_size - *gen0_size_ptr;
416 *gen1_size_ptr =
417 MAX2((uintx)align_size_down(*gen1_size_ptr, min_alignment()),
418 min_alignment());
419 }
420 }
421 return result;
422 }
423
424 // Minimum sizes of the generations may be different than
425 // the initial sizes. An inconsistently is permitted here
426 // in the total size that can be specified explicitly by
427 // command line specification of OldSize and NewSize and
428 // also a command line specification of -Xms. Issue a warning
429 // but allow the values to pass.
430
431 void TwoGenerationCollectorPolicy::initialize_size_info() {
432 GenCollectorPolicy::initialize_size_info();
433
434 // At this point the minimum, initial and maximum sizes
435 // of the overall heap and of gen0 have been determined.
436 // The maximum gen1 size can be determined from the maximum gen0
437 // and maximum heap size since no explicit flags exits
438 // for setting the gen1 maximum.
439 _max_gen1_size = max_heap_byte_size() - _max_gen0_size;
440 _max_gen1_size =
441 MAX2((uintx)align_size_down(_max_gen1_size, min_alignment()),
442 min_alignment());
443 // If no explicit command line flag has been set for the
444 // gen1 size, use what is left for gen1.
445 if (FLAG_IS_DEFAULT(OldSize) || FLAG_IS_ERGO(OldSize)) {
446 // The user has not specified any value or ergonomics
447 // has chosen a value (which may or may not be consistent
448 // with the overall heap size). In either case make
449 // the minimum, maximum and initial sizes consistent
450 // with the gen0 sizes and the overall heap sizes.
451 assert(min_heap_byte_size() > _min_gen0_size,
452 "gen0 has an unexpected minimum size");
453 set_min_gen1_size(min_heap_byte_size() - min_gen0_size());
454 set_min_gen1_size(
455 MAX2((uintx)align_size_down(_min_gen1_size, min_alignment()),
456 min_alignment()));
457 set_initial_gen1_size(initial_heap_byte_size() - initial_gen0_size());
458 set_initial_gen1_size(
459 MAX2((uintx)align_size_down(_initial_gen1_size, min_alignment()),
460 min_alignment()));
461
462 } else {
463 // It's been explicitly set on the command line. Use the
464 // OldSize and then determine the consequences.
465 set_min_gen1_size(OldSize);
466 set_initial_gen1_size(OldSize);
467
468 // If the user has explicitly set an OldSize that is inconsistent
469 // with other command line flags, issue a warning.
470 // The generation minimums and the overall heap mimimum should
471 // be within one heap alignment.
472 if ((_min_gen1_size + _min_gen0_size + min_alignment()) <
473 min_heap_byte_size()) {
474 warning("Inconsistency between minimum heap size and minimum "
475 "generation sizes: using minimum heap = " SIZE_FORMAT,
476 min_heap_byte_size());
477 }
478 if ((OldSize > _max_gen1_size)) {
479 warning("Inconsistency between maximum heap size and maximum "
480 "generation sizes: using maximum heap = " SIZE_FORMAT
481 " -XX:OldSize flag is being ignored",
482 max_heap_byte_size());
483 }
484 // If there is an inconsistency between the OldSize and the minimum and/or
485 // initial size of gen0, since OldSize was explicitly set, OldSize wins.
486 if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size,
487 min_heap_byte_size(), OldSize)) {
488 if (PrintGCDetails && Verbose) {
489 gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
490 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
491 min_gen0_size(), initial_gen0_size(), max_gen0_size());
492 }
493 }
494 // Initial size
495 if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,
496 initial_heap_byte_size(), OldSize)) {
497 if (PrintGCDetails && Verbose) {
498 gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
499 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
500 min_gen0_size(), initial_gen0_size(), max_gen0_size());
501 }
502 }
503 }
504 // Enforce the maximum gen1 size.
505 set_min_gen1_size(MIN2(_min_gen1_size, _max_gen1_size));
506
507 // Check that min gen1 <= initial gen1 <= max gen1
508 set_initial_gen1_size(MAX2(_initial_gen1_size, _min_gen1_size));
509 set_initial_gen1_size(MIN2(_initial_gen1_size, _max_gen1_size));
510
511 if (PrintGCDetails && Verbose) {
512 gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 "
513 SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT,
514 min_gen1_size(), initial_gen1_size(), max_gen1_size());
515 }
516 }
517
518 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
519 bool is_tlab,
520 bool* gc_overhead_limit_was_exceeded) {
521 GenCollectedHeap *gch = GenCollectedHeap::heap();
522
523 debug_only(gch->check_for_valid_allocation_state());
524 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
525
526 // In general gc_overhead_limit_was_exceeded should be false so
527 // set it so here and reset it to true only if the gc time
528 // limit is being exceeded as checked below.
529 *gc_overhead_limit_was_exceeded = false;
530
531 HeapWord* result = NULL;
532
533 // Loop until the allocation is satisified,
534 // or unsatisfied after GC.
535 for (int try_count = 1; /* return or throw */; try_count += 1) {
536 HandleMark hm; // discard any handles allocated in each iteration
537
538 // First allocation attempt is lock-free.
539 Generation *gen0 = gch->get_gen(0);
540 assert(gen0->supports_inline_contig_alloc(),
541 "Otherwise, must do alloc within heap lock");
542 if (gen0->should_allocate(size, is_tlab)) {
543 result = gen0->par_allocate(size, is_tlab);
544 if (result != NULL) {
545 assert(gch->is_in_reserved(result), "result not in heap");
546 return result;
547 }
548 }
549 unsigned int gc_count_before; // read inside the Heap_lock locked region
550 {
551 MutexLocker ml(Heap_lock);
552 if (PrintGC && Verbose) {
553 gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:"
554 " attempting locked slow path allocation");
555 }
556 // Note that only large objects get a shot at being
557 // allocated in later generations.
558 bool first_only = ! should_try_older_generation_allocation(size);
559
560 result = gch->attempt_allocation(size, is_tlab, first_only);
561 if (result != NULL) {
562 assert(gch->is_in_reserved(result), "result not in heap");
563 return result;
564 }
565
566 if (GC_locker::is_active_and_needs_gc()) {
567 if (is_tlab) {
568 return NULL; // Caller will retry allocating individual object
569 }
570 if (!gch->is_maximal_no_gc()) {
571 // Try and expand heap to satisfy request
572 result = expand_heap_and_allocate(size, is_tlab);
573 // result could be null if we are out of space
574 if (result != NULL) {
575 return result;
576 }
577 }
578
579 // If this thread is not in a jni critical section, we stall
580 // the requestor until the critical section has cleared and
581 // GC allowed. When the critical section clears, a GC is
582 // initiated by the last thread exiting the critical section; so
583 // we retry the allocation sequence from the beginning of the loop,
584 // rather than causing more, now probably unnecessary, GC attempts.
585 JavaThread* jthr = JavaThread::current();
586 if (!jthr->in_critical()) {
587 MutexUnlocker mul(Heap_lock);
588 // Wait for JNI critical section to be exited
589 GC_locker::stall_until_clear();
590 continue;
591 } else {
592 if (CheckJNICalls) {
593 fatal("Possible deadlock due to allocating while"
594 " in jni critical section");
595 }
596 return NULL;
597 }
598 }
599
600 // Read the gc count while the heap lock is held.
601 gc_count_before = Universe::heap()->total_collections();
602 }
603
604 VM_GenCollectForAllocation op(size,
605 is_tlab,
606 gc_count_before);
607 VMThread::execute(&op);
608 if (op.prologue_succeeded()) {
609 result = op.result();
610 if (op.gc_locked()) {
611 assert(result == NULL, "must be NULL if gc_locked() is true");
612 continue; // retry and/or stall as necessary
613 }
614
615 // Allocation has failed and a collection
616 // has been done. If the gc time limit was exceeded the
617 // this time, return NULL so that an out-of-memory
618 // will be thrown. Clear gc_overhead_limit_exceeded
619 // so that the overhead exceeded does not persist.
620
621 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
622 const bool softrefs_clear = all_soft_refs_clear();
623
624 if (limit_exceeded && softrefs_clear) {
625 *gc_overhead_limit_was_exceeded = true;
626 size_policy()->set_gc_overhead_limit_exceeded(false);
627 if (op.result() != NULL) {
628 CollectedHeap::fill_with_object(op.result(), size);
629 }
630 return NULL;
631 }
632 assert(result == NULL || gch->is_in_reserved(result),
633 "result not in heap");
634 return result;
635 }
636
637 // Give a warning if we seem to be looping forever.
638 if ((QueuedAllocationWarningCount > 0) &&
639 (try_count % QueuedAllocationWarningCount == 0)) {
640 warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t"
641 " size=%d %s", try_count, size, is_tlab ? "(TLAB)" : "");
642 }
643 }
644 }
645
646 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size,
647 bool is_tlab) {
648 GenCollectedHeap *gch = GenCollectedHeap::heap();
649 HeapWord* result = NULL;
650 for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) {
651 Generation *gen = gch->get_gen(i);
652 if (gen->should_allocate(size, is_tlab)) {
653 result = gen->expand_and_allocate(size, is_tlab);
654 }
655 }
656 assert(result == NULL || gch->is_in_reserved(result), "result not in heap");
657 return result;
658 }
659
660 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size,
661 bool is_tlab) {
662 GenCollectedHeap *gch = GenCollectedHeap::heap();
663 GCCauseSetter x(gch, GCCause::_allocation_failure);
664 HeapWord* result = NULL;
665
666 assert(size != 0, "Precondition violated");
667 if (GC_locker::is_active_and_needs_gc()) {
668 // GC locker is active; instead of a collection we will attempt
669 // to expand the heap, if there's room for expansion.
670 if (!gch->is_maximal_no_gc()) {
671 result = expand_heap_and_allocate(size, is_tlab);
672 }
673 return result; // could be null if we are out of space
674 } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) {
675 // Do an incremental collection.
676 gch->do_collection(false /* full */,
677 false /* clear_all_soft_refs */,
678 size /* size */,
679 is_tlab /* is_tlab */,
680 number_of_generations() - 1 /* max_level */);
681 } else {
682 if (Verbose && PrintGCDetails) {
683 gclog_or_tty->print(" :: Trying full because partial may fail :: ");
684 }
685 // Try a full collection; see delta for bug id 6266275
686 // for the original code and why this has been simplified
687 // with from-space allocation criteria modified and
688 // such allocation moved out of the safepoint path.
689 gch->do_collection(true /* full */,
690 false /* clear_all_soft_refs */,
691 size /* size */,
692 is_tlab /* is_tlab */,
693 number_of_generations() - 1 /* max_level */);
694 }
695
696 result = gch->attempt_allocation(size, is_tlab, false /*first_only*/);
697
698 if (result != NULL) {
699 assert(gch->is_in_reserved(result), "result not in heap");
700 return result;
701 }
702
703 // OK, collection failed, try expansion.
704 result = expand_heap_and_allocate(size, is_tlab);
705 if (result != NULL) {
706 return result;
707 }
708
709 // If we reach this point, we're really out of memory. Try every trick
710 // we can to reclaim memory. Force collection of soft references. Force
711 // a complete compaction of the heap. Any additional methods for finding
712 // free memory should be here, especially if they are expensive. If this
713 // attempt fails, an OOM exception will be thrown.
714 {
715 IntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
716
717 gch->do_collection(true /* full */,
718 true /* clear_all_soft_refs */,
719 size /* size */,
720 is_tlab /* is_tlab */,
721 number_of_generations() - 1 /* max_level */);
722 }
723
724 result = gch->attempt_allocation(size, is_tlab, false /* first_only */);
725 if (result != NULL) {
726 assert(gch->is_in_reserved(result), "result not in heap");
727 return result;
728 }
729
730 assert(!should_clear_all_soft_refs(),
731 "Flag should have been handled and cleared prior to this point");
732
733 // What else? We might try synchronous finalization later. If the total
734 // space available is large enough for the allocation, then a more
735 // complete compaction phase than we've tried so far might be
736 // appropriate.
737 return NULL;
738 }
739
740 MetaWord* CollectorPolicy::satisfy_failed_metadata_allocation(
741 ClassLoaderData* loader_data,
742 size_t word_size,
743 Metaspace::MetadataType mdtype) {
744 uint loop_count = 0;
745 uint gc_count = 0;
746 uint full_gc_count = 0;
747
748 assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock");
749
750 do {
751 MetaWord* result = NULL;
752 if (GC_locker::is_active_and_needs_gc()) {
753 // If the GC_locker is active, just expand and allocate.
754 // If that does not succeed, wait if this thread is not
755 // in a critical section itself.
756 result =
757 loader_data->metaspace_non_null()->expand_and_allocate(word_size,
758 mdtype);
759 if (result != NULL) {
760 return result;
761 }
762 JavaThread* jthr = JavaThread::current();
763 if (!jthr->in_critical()) {
764 // Wait for JNI critical section to be exited
765 GC_locker::stall_until_clear();
766 // The GC invoked by the last thread leaving the critical
767 // section will be a young collection and a full collection
768 // is (currently) needed for unloading classes so continue
769 // to the next iteration to get a full GC.
770 continue;
771 } else {
772 if (CheckJNICalls) {
773 fatal("Possible deadlock due to allocating while"
774 " in jni critical section");
775 }
776 return NULL;
777 }
778 }
779
780 { // Need lock to get self consistent gc_count's
781 MutexLocker ml(Heap_lock);
782 gc_count = Universe::heap()->total_collections();
783 full_gc_count = Universe::heap()->total_full_collections();
784 }
785
786 // Generate a VM operation
787 VM_CollectForMetadataAllocation op(loader_data,
788 word_size,
789 mdtype,
790 gc_count,
791 full_gc_count,
792 GCCause::_metadata_GC_threshold);
793 VMThread::execute(&op);
794
795 // If GC was locked out, try again. Check
796 // before checking success because the prologue
797 // could have succeeded and the GC still have
798 // been locked out.
799 if (op.gc_locked()) {
800 continue;
801 }
802
803 if (op.prologue_succeeded()) {
804 return op.result();
805 }
806 loop_count++;
807 if ((QueuedAllocationWarningCount > 0) &&
808 (loop_count % QueuedAllocationWarningCount == 0)) {
809 warning("satisfy_failed_metadata_allocation() retries %d times \n\t"
810 " size=%d", loop_count, word_size);
811 }
812 } while (true); // Until a GC is done
813 }
814
815 // Return true if any of the following is true:
816 // . the allocation won't fit into the current young gen heap
817 // . gc locker is occupied (jni critical section)
818 // . heap memory is tight -- the most recent previous collection
819 // was a full collection because a partial collection (would
820 // have) failed and is likely to fail again
821 bool GenCollectorPolicy::should_try_older_generation_allocation(
822 size_t word_size) const {
823 GenCollectedHeap* gch = GenCollectedHeap::heap();
824 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();
825 return (word_size > heap_word_size(gen0_capacity))
826 || GC_locker::is_active_and_needs_gc()
827 || gch->incremental_collection_failed();
828 }
829
830
831 //
832 // MarkSweepPolicy methods
833 //
834
835 MarkSweepPolicy::MarkSweepPolicy() {
836 initialize_all();
837 }
838
839 void MarkSweepPolicy::initialize_generations() {
840 _generations = new GenerationSpecPtr[number_of_generations()];
841 if (_generations == NULL)
842 vm_exit_during_initialization("Unable to allocate gen spec");
843
844 if (UseParNewGC) {
845 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);
846 } else {
847 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);
848 }
849 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);
850
851 if (_generations[0] == NULL || _generations[1] == NULL)
852 vm_exit_during_initialization("Unable to allocate gen spec");
853 }
854
855 void MarkSweepPolicy::initialize_gc_policy_counters() {
856 // initialize the policy counters - 2 collectors, 3 generations
857 if (UseParNewGC) {
858 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);
859 } else {
860 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
861 }
862 }