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 (MaxHeapSize < InitialHeapSize) {
52 vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
53 }
54
55 if (MetaspaceSize > MaxMetaspaceSize) {
56 MaxMetaspaceSize = MetaspaceSize;
57 }
58 MetaspaceSize = MAX2(min_alignment(), align_size_down_(MetaspaceSize, min_alignment()));
59 // Don't increase Metaspace size limit above specified.
60 MaxMetaspaceSize = align_size_down(MaxMetaspaceSize, max_alignment());
61 if (MetaspaceSize > MaxMetaspaceSize) {
62 MetaspaceSize = MaxMetaspaceSize;
63 }
64
65 MinMetaspaceExpansion = MAX2(min_alignment(), align_size_down_(MinMetaspaceExpansion, min_alignment()));
66 MaxMetaspaceExpansion = MAX2(min_alignment(), align_size_down_(MaxMetaspaceExpansion, min_alignment()));
67
68 MinHeapDeltaBytes = align_size_up(MinHeapDeltaBytes, min_alignment());
69
70 assert(MetaspaceSize % min_alignment() == 0, "metapace alignment");
71 assert(MaxMetaspaceSize % max_alignment() == 0, "maximum metaspace alignment");
72 if (MetaspaceSize < 256*K) {
73 vm_exit_during_initialization("Too small initial Metaspace size");
74 }
75 }
76
77 void CollectorPolicy::initialize_size_info() {
78 // User inputs from -mx and ms are aligned
79 set_initial_heap_byte_size(InitialHeapSize);
80 if (initial_heap_byte_size() == 0) {
81 set_initial_heap_byte_size(NewSize + OldSize);
82 }
83 set_initial_heap_byte_size(align_size_up(_initial_heap_byte_size,
84 min_alignment()));
85
86 set_min_heap_byte_size(Arguments::min_heap_size());
87 if (min_heap_byte_size() == 0) {
88 set_min_heap_byte_size(NewSize + OldSize);
89 }
90 set_min_heap_byte_size(align_size_up(_min_heap_byte_size,
91 min_alignment()));
92
93 set_max_heap_byte_size(align_size_up(MaxHeapSize, max_alignment()));
94
95 // Check heap parameter properties
96 if (initial_heap_byte_size() < M) {
97 vm_exit_during_initialization("Too small initial heap");
98 }
99 // Check heap parameter properties
100 if (min_heap_byte_size() < M) {
101 vm_exit_during_initialization("Too small minimum heap");
102 }
103 if (initial_heap_byte_size() <= NewSize) {
104 // make sure there is at least some room in old space
105 vm_exit_during_initialization("Too small initial heap for new size specified");
106 }
107 if (max_heap_byte_size() < min_heap_byte_size()) {
108 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified");
109 }
110 if (initial_heap_byte_size() < min_heap_byte_size()) {
111 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified");
112 }
113 if (max_heap_byte_size() < initial_heap_byte_size()) {
114 vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
115 }
116
117 if (PrintGCDetails && Verbose) {
118 gclog_or_tty->print_cr("Minimum heap " SIZE_FORMAT " Initial heap "
119 SIZE_FORMAT " Maximum heap " SIZE_FORMAT,
120 min_heap_byte_size(), initial_heap_byte_size(), max_heap_byte_size());
121 }
122 }
123
124 bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) {
125 bool result = _should_clear_all_soft_refs;
126 set_should_clear_all_soft_refs(false);
127 return result;
128 }
129
130 GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap,
131 int max_covered_regions) {
132 switch (rem_set_name()) {
133 case GenRemSet::CardTable: {
134 CardTableRS* res = new CardTableRS(whole_heap, max_covered_regions);
135 return res;
136 }
137 default:
138 guarantee(false, "unrecognized GenRemSet::Name");
139 return NULL;
140 }
141 }
142
143 void CollectorPolicy::cleared_all_soft_refs() {
144 // If near gc overhear limit, continue to clear SoftRefs. SoftRefs may
145 // have been cleared in the last collection but if the gc overhear
146 // limit continues to be near, SoftRefs should still be cleared.
147 if (size_policy() != NULL) {
148 _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near();
149 }
150 _all_soft_refs_clear = true;
151 }
152
153
154 // GenCollectorPolicy methods.
155
156 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {
157 size_t x = base_size / (NewRatio+1);
158 size_t new_gen_size = x > min_alignment() ?
159 align_size_down(x, min_alignment()) :
160 min_alignment();
161 return new_gen_size;
162 }
163
164 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,
165 size_t maximum_size) {
166 size_t alignment = min_alignment();
167 size_t max_minus = maximum_size - alignment;
168 return desired_size < max_minus ? desired_size : max_minus;
169 }
170
171
172 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size,
173 size_t init_promo_size,
174 size_t init_survivor_size) {
175 const double max_gc_pause_sec = ((double) MaxGCPauseMillis)/1000.0;
176 _size_policy = new AdaptiveSizePolicy(init_eden_size,
177 init_promo_size,
178 init_survivor_size,
179 max_gc_pause_sec,
180 GCTimeRatio);
181 }
182
183 size_t GenCollectorPolicy::compute_max_alignment() {
184 // The card marking array and the offset arrays for old generations are
185 // committed in os pages as well. Make sure they are entirely full (to
186 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
187 // byte entry and the os page size is 4096, the maximum heap size should
188 // be 512*4096 = 2MB aligned.
189 size_t alignment = GenRemSet::max_alignment_constraint(rem_set_name());
190
191 // Parallel GC does its own alignment of the generations to avoid requiring a
192 // large page (256M on some platforms) for the permanent generation. The
193 // other collectors should also be updated to do their own alignment and then
194 // this use of lcm() should be removed.
195 if (UseLargePages && !UseParallelGC) {
196 // in presence of large pages we have to make sure that our
197 // alignment is large page aware
198 alignment = lcm(os::large_page_size(), alignment);
199 }
200
201 return alignment;
202 }
203
204 void GenCollectorPolicy::initialize_flags() {
205 // All sizes must be multiples of the generation granularity.
206 set_min_alignment((uintx) Generation::GenGrain);
207 set_max_alignment(compute_max_alignment());
208 assert(max_alignment() >= min_alignment() &&
209 max_alignment() % min_alignment() == 0,
210 "invalid alignment constraints");
211
212 CollectorPolicy::initialize_flags();
213
214 // All generational heaps have a youngest gen; handle those flags here.
215
216 // Adjust max size parameters
217 if (NewSize > MaxNewSize) {
218 MaxNewSize = NewSize;
219 }
220 NewSize = align_size_down(NewSize, min_alignment());
221 MaxNewSize = align_size_down(MaxNewSize, min_alignment());
222
223 // Check validity of heap flags
224 assert(NewSize % min_alignment() == 0, "eden space alignment");
225 assert(MaxNewSize % min_alignment() == 0, "survivor space alignment");
226
227 if (NewSize < 3*min_alignment()) {
228 // make sure there room for eden and two survivor spaces
229 vm_exit_during_initialization("Too small new size specified");
230 }
231 if (SurvivorRatio < 1 || NewRatio < 1) {
232 vm_exit_during_initialization("Invalid heap ratio specified");
233 }
234 }
235
236 void TwoGenerationCollectorPolicy::initialize_flags() {
237 GenCollectorPolicy::initialize_flags();
238
239 OldSize = align_size_down(OldSize, min_alignment());
240
241 if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(NewSize)) {
242 // NewRatio will be used later to set the young generation size so we use
243 // it to calculate how big the heap should be based on the requested OldSize
244 // and NewRatio.
245 assert(NewRatio > 0, "NewRatio should have been set up earlier");
246 size_t calculated_heapsize = (OldSize / NewRatio) * (NewRatio + 1);
247
248 calculated_heapsize = align_size_up(calculated_heapsize, max_alignment());
249 MaxHeapSize = calculated_heapsize;
250 InitialHeapSize = calculated_heapsize;
251 }
252 MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
253
254 // adjust max heap size if necessary
255 if (NewSize + OldSize > MaxHeapSize) {
256 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
257 // somebody set a maximum heap size with the intention that we should not
258 // exceed it. Adjust New/OldSize as necessary.
259 uintx calculated_size = NewSize + OldSize;
260 double shrink_factor = (double) MaxHeapSize / calculated_size;
261 // align
262 NewSize = align_size_down((uintx) (NewSize * shrink_factor), min_alignment());
263 // OldSize is already aligned because above we aligned MaxHeapSize to
264 // max_alignment(), and we just made sure that NewSize is aligned to
265 // min_alignment(). In initialize_flags() we verified that max_alignment()
266 // is a multiple of min_alignment().
267 OldSize = MaxHeapSize - NewSize;
268 } else {
269 MaxHeapSize = NewSize + OldSize;
270 }
271 }
272 // need to do this again
273 MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
274
275 always_do_update_barrier = UseConcMarkSweepGC;
276
277 // Check validity of heap flags
278 assert(OldSize % min_alignment() == 0, "old space alignment");
279 assert(MaxHeapSize % max_alignment() == 0, "maximum heap alignment");
280 }
281
282 // Values set on the command line win over any ergonomically
283 // set command line parameters.
284 // Ergonomic choice of parameters are done before this
285 // method is called. Values for command line parameters such as NewSize
286 // and MaxNewSize feed those ergonomic choices into this method.
287 // This method makes the final generation sizings consistent with
288 // themselves and with overall heap sizings.
289 // In the absence of explicitly set command line flags, policies
290 // such as the use of NewRatio are used to size the generation.
291 void GenCollectorPolicy::initialize_size_info() {
292 CollectorPolicy::initialize_size_info();
293
294 // min_alignment() is used for alignment within a generation.
295 // There is additional alignment done down stream for some
296 // collectors that sometimes causes unwanted rounding up of
297 // generations sizes.
298
299 // Determine maximum size of gen0
300
301 size_t max_new_size = 0;
302 if (FLAG_IS_CMDLINE(MaxNewSize) || FLAG_IS_ERGO(MaxNewSize)) {
303 if (MaxNewSize < min_alignment()) {
304 max_new_size = min_alignment();
305 }
306 if (MaxNewSize >= max_heap_byte_size()) {
307 max_new_size = align_size_down(max_heap_byte_size() - min_alignment(),
308 min_alignment());
309 warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or "
310 "greater than the entire heap (" SIZE_FORMAT "k). A "
311 "new generation size of " SIZE_FORMAT "k will be used.",
312 MaxNewSize/K, max_heap_byte_size()/K, max_new_size/K);
313 } else {
314 max_new_size = align_size_down(MaxNewSize, min_alignment());
315 }
316
317 // The case for FLAG_IS_ERGO(MaxNewSize) could be treated
318 // specially at this point to just use an ergonomically set
319 // MaxNewSize to set max_new_size. For cases with small
320 // heaps such a policy often did not work because the MaxNewSize
321 // was larger than the entire heap. The interpretation given
322 // to ergonomically set flags is that the flags are set
323 // by different collectors for their own special needs but
324 // are not allowed to badly shape the heap. This allows the
325 // different collectors to decide what's best for themselves
326 // without having to factor in the overall heap shape. It
327 // can be the case in the future that the collectors would
328 // only make "wise" ergonomics choices and this policy could
329 // just accept those choices. The choices currently made are
330 // not always "wise".
331 } else {
332 max_new_size = scale_by_NewRatio_aligned(max_heap_byte_size());
333 // Bound the maximum size by NewSize below (since it historically
334 // would have been NewSize and because the NewRatio calculation could
335 // yield a size that is too small) and bound it by MaxNewSize above.
336 // Ergonomics plays here by previously calculating the desired
337 // NewSize and MaxNewSize.
338 max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize);
339 }
340 assert(max_new_size > 0, "All paths should set max_new_size");
341
342 // Given the maximum gen0 size, determine the initial and
343 // minimum gen0 sizes.
344
345 if (max_heap_byte_size() == min_heap_byte_size()) {
346 // The maximum and minimum heap sizes are the same so
347 // the generations minimum and initial must be the
348 // same as its maximum.
349 set_min_gen0_size(max_new_size);
350 set_initial_gen0_size(max_new_size);
351 set_max_gen0_size(max_new_size);
352 } else {
353 size_t desired_new_size = 0;
354 if (!FLAG_IS_DEFAULT(NewSize)) {
355 // If NewSize is set ergonomically (for example by cms), it
356 // would make sense to use it. If it is used, also use it
357 // to set the initial size. Although there is no reason
358 // the minimum size and the initial size have to be the same,
359 // the current implementation gets into trouble during the calculation
360 // of the tenured generation sizes if they are different.
361 // Note that this makes the initial size and the minimum size
362 // generally small compared to the NewRatio calculation.
363 _min_gen0_size = NewSize;
364 desired_new_size = NewSize;
365 max_new_size = MAX2(max_new_size, NewSize);
366 } else {
367 // For the case where NewSize is the default, use NewRatio
368 // to size the minimum and initial generation sizes.
369 // Use the default NewSize as the floor for these values. If
370 // NewRatio is overly large, the resulting sizes can be too
371 // small.
372 _min_gen0_size = MAX2(scale_by_NewRatio_aligned(min_heap_byte_size()),
373 NewSize);
374 desired_new_size =
375 MAX2(scale_by_NewRatio_aligned(initial_heap_byte_size()),
376 NewSize);
377 }
378
379 assert(_min_gen0_size > 0, "Sanity check");
380 set_initial_gen0_size(desired_new_size);
381 set_max_gen0_size(max_new_size);
382
383 // At this point the desirable initial and minimum sizes have been
384 // determined without regard to the maximum sizes.
385
386 // Bound the sizes by the corresponding overall heap sizes.
387 set_min_gen0_size(
388 bound_minus_alignment(_min_gen0_size, min_heap_byte_size()));
389 set_initial_gen0_size(
390 bound_minus_alignment(_initial_gen0_size, initial_heap_byte_size()));
391 set_max_gen0_size(
392 bound_minus_alignment(_max_gen0_size, max_heap_byte_size()));
393
394 // At this point all three sizes have been checked against the
395 // maximum sizes but have not been checked for consistency
396 // among the three.
397
398 // Final check min <= initial <= max
399 set_min_gen0_size(MIN2(_min_gen0_size, _max_gen0_size));
400 set_initial_gen0_size(
401 MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size));
402 set_min_gen0_size(MIN2(_min_gen0_size, _initial_gen0_size));
403 }
404
405 if (PrintGCDetails && Verbose) {
406 gclog_or_tty->print_cr("1: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
407 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
408 min_gen0_size(), initial_gen0_size(), max_gen0_size());
409 }
410 }
411
412 // Call this method during the sizing of the gen1 to make
413 // adjustments to gen0 because of gen1 sizing policy. gen0 initially has
414 // the most freedom in sizing because it is done before the
415 // policy for gen1 is applied. Once gen1 policies have been applied,
416 // there may be conflicts in the shape of the heap and this method
417 // is used to make the needed adjustments. The application of the
418 // policies could be more sophisticated (iterative for example) but
419 // keeping it simple also seems a worthwhile goal.
420 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr,
421 size_t* gen1_size_ptr,
422 const size_t heap_size,
423 const size_t min_gen1_size) {
424 bool result = false;
425
426 if ((*gen1_size_ptr + *gen0_size_ptr) > heap_size) {
427 if ((heap_size < (*gen0_size_ptr + min_gen1_size)) &&
428 (heap_size >= min_gen1_size + min_alignment())) {
429 // Adjust gen0 down to accommodate min_gen1_size
430 *gen0_size_ptr = heap_size - min_gen1_size;
431 *gen0_size_ptr =
432 MAX2((uintx)align_size_down(*gen0_size_ptr, min_alignment()),
433 min_alignment());
434 assert(*gen0_size_ptr > 0, "Min gen0 is too large");
435 result = true;
436 } else {
437 *gen1_size_ptr = heap_size - *gen0_size_ptr;
438 *gen1_size_ptr =
439 MAX2((uintx)align_size_down(*gen1_size_ptr, min_alignment()),
440 min_alignment());
441 }
442 }
443 return result;
444 }
445
446 // Minimum sizes of the generations may be different than
447 // the initial sizes. An inconsistently is permitted here
448 // in the total size that can be specified explicitly by
449 // command line specification of OldSize and NewSize and
450 // also a command line specification of -Xms. Issue a warning
451 // but allow the values to pass.
452
453 void TwoGenerationCollectorPolicy::initialize_size_info() {
454 GenCollectorPolicy::initialize_size_info();
455
456 // At this point the minimum, initial and maximum sizes
457 // of the overall heap and of gen0 have been determined.
458 // The maximum gen1 size can be determined from the maximum gen0
459 // and maximum heap size since no explicit flags exits
460 // for setting the gen1 maximum.
461 _max_gen1_size = max_heap_byte_size() - _max_gen0_size;
462 _max_gen1_size =
463 MAX2((uintx)align_size_down(_max_gen1_size, min_alignment()),
464 min_alignment());
465 // If no explicit command line flag has been set for the
466 // gen1 size, use what is left for gen1.
467 if (FLAG_IS_DEFAULT(OldSize) || FLAG_IS_ERGO(OldSize)) {
468 // The user has not specified any value or ergonomics
469 // has chosen a value (which may or may not be consistent
470 // with the overall heap size). In either case make
471 // the minimum, maximum and initial sizes consistent
472 // with the gen0 sizes and the overall heap sizes.
473 assert(min_heap_byte_size() > _min_gen0_size,
474 "gen0 has an unexpected minimum size");
475 set_min_gen1_size(min_heap_byte_size() - min_gen0_size());
476 set_min_gen1_size(
477 MAX2((uintx)align_size_down(_min_gen1_size, min_alignment()),
478 min_alignment()));
479 set_initial_gen1_size(initial_heap_byte_size() - initial_gen0_size());
480 set_initial_gen1_size(
481 MAX2((uintx)align_size_down(_initial_gen1_size, min_alignment()),
482 min_alignment()));
483
484 } else {
485 // It's been explicitly set on the command line. Use the
486 // OldSize and then determine the consequences.
487 set_min_gen1_size(OldSize);
488 set_initial_gen1_size(OldSize);
489
490 // If the user has explicitly set an OldSize that is inconsistent
491 // with other command line flags, issue a warning.
492 // The generation minimums and the overall heap mimimum should
493 // be within one heap alignment.
494 if ((_min_gen1_size + _min_gen0_size + min_alignment()) <
495 min_heap_byte_size()) {
496 warning("Inconsistency between minimum heap size and minimum "
497 "generation sizes: using minimum heap = " SIZE_FORMAT,
498 min_heap_byte_size());
499 }
500 if ((OldSize > _max_gen1_size)) {
501 warning("Inconsistency between maximum heap size and maximum "
502 "generation sizes: using maximum heap = " SIZE_FORMAT
503 " -XX:OldSize flag is being ignored",
504 max_heap_byte_size());
505 }
506 // If there is an inconsistency between the OldSize and the minimum and/or
507 // initial size of gen0, since OldSize was explicitly set, OldSize wins.
508 if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size,
509 min_heap_byte_size(), OldSize)) {
510 if (PrintGCDetails && Verbose) {
511 gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
512 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
513 min_gen0_size(), initial_gen0_size(), max_gen0_size());
514 }
515 }
516 // Initial size
517 if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,
518 initial_heap_byte_size(), OldSize)) {
519 if (PrintGCDetails && Verbose) {
520 gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
521 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
522 min_gen0_size(), initial_gen0_size(), max_gen0_size());
523 }
524 }
525 }
526 // Enforce the maximum gen1 size.
527 set_min_gen1_size(MIN2(_min_gen1_size, _max_gen1_size));
528
529 // Check that min gen1 <= initial gen1 <= max gen1
530 set_initial_gen1_size(MAX2(_initial_gen1_size, _min_gen1_size));
531 set_initial_gen1_size(MIN2(_initial_gen1_size, _max_gen1_size));
532
533 if (PrintGCDetails && Verbose) {
534 gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 "
535 SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT,
536 min_gen1_size(), initial_gen1_size(), max_gen1_size());
537 }
538 }
539
540 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
541 bool is_tlab,
542 bool* gc_overhead_limit_was_exceeded) {
543 GenCollectedHeap *gch = GenCollectedHeap::heap();
544
545 debug_only(gch->check_for_valid_allocation_state());
546 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
547
548 // In general gc_overhead_limit_was_exceeded should be false so
549 // set it so here and reset it to true only if the gc time
550 // limit is being exceeded as checked below.
551 *gc_overhead_limit_was_exceeded = false;
552
553 HeapWord* result = NULL;
554
555 // Loop until the allocation is satisified,
556 // or unsatisfied after GC.
557 for (int try_count = 1; /* return or throw */; try_count += 1) {
558 HandleMark hm; // discard any handles allocated in each iteration
559
560 // First allocation attempt is lock-free.
561 Generation *gen0 = gch->get_gen(0);
562 assert(gen0->supports_inline_contig_alloc(),
563 "Otherwise, must do alloc within heap lock");
564 if (gen0->should_allocate(size, is_tlab)) {
565 result = gen0->par_allocate(size, is_tlab);
566 if (result != NULL) {
567 assert(gch->is_in_reserved(result), "result not in heap");
568 return result;
569 }
570 }
571 unsigned int gc_count_before; // read inside the Heap_lock locked region
572 {
573 MutexLocker ml(Heap_lock);
574 if (PrintGC && Verbose) {
575 gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:"
576 " attempting locked slow path allocation");
577 }
578 // Note that only large objects get a shot at being
579 // allocated in later generations.
580 bool first_only = ! should_try_older_generation_allocation(size);
581
582 result = gch->attempt_allocation(size, is_tlab, first_only);
583 if (result != NULL) {
584 assert(gch->is_in_reserved(result), "result not in heap");
585 return result;
586 }
587
588 if (GC_locker::is_active_and_needs_gc()) {
589 if (is_tlab) {
590 return NULL; // Caller will retry allocating individual object
591 }
592 if (!gch->is_maximal_no_gc()) {
593 // Try and expand heap to satisfy request
594 result = expand_heap_and_allocate(size, is_tlab);
595 // result could be null if we are out of space
596 if (result != NULL) {
597 return result;
598 }
599 }
600
601 // If this thread is not in a jni critical section, we stall
602 // the requestor until the critical section has cleared and
603 // GC allowed. When the critical section clears, a GC is
604 // initiated by the last thread exiting the critical section; so
605 // we retry the allocation sequence from the beginning of the loop,
606 // rather than causing more, now probably unnecessary, GC attempts.
607 JavaThread* jthr = JavaThread::current();
608 if (!jthr->in_critical()) {
609 MutexUnlocker mul(Heap_lock);
610 // Wait for JNI critical section to be exited
611 GC_locker::stall_until_clear();
612 continue;
613 } else {
614 if (CheckJNICalls) {
615 fatal("Possible deadlock due to allocating while"
616 " in jni critical section");
617 }
618 return NULL;
619 }
620 }
621
622 // Read the gc count while the heap lock is held.
623 gc_count_before = Universe::heap()->total_collections();
624 }
625
626 VM_GenCollectForAllocation op(size,
627 is_tlab,
628 gc_count_before);
629 VMThread::execute(&op);
630 if (op.prologue_succeeded()) {
631 result = op.result();
632 if (op.gc_locked()) {
633 assert(result == NULL, "must be NULL if gc_locked() is true");
634 continue; // retry and/or stall as necessary
635 }
636
637 // Allocation has failed and a collection
638 // has been done. If the gc time limit was exceeded the
639 // this time, return NULL so that an out-of-memory
640 // will be thrown. Clear gc_overhead_limit_exceeded
641 // so that the overhead exceeded does not persist.
642
643 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
644 const bool softrefs_clear = all_soft_refs_clear();
645 assert(!limit_exceeded || softrefs_clear, "Should have been cleared");
646 if (limit_exceeded && softrefs_clear) {
647 *gc_overhead_limit_was_exceeded = true;
648 size_policy()->set_gc_overhead_limit_exceeded(false);
649 if (op.result() != NULL) {
650 CollectedHeap::fill_with_object(op.result(), size);
651 }
652 return NULL;
653 }
654 assert(result == NULL || gch->is_in_reserved(result),
655 "result not in heap");
656 return result;
657 }
658
659 // Give a warning if we seem to be looping forever.
660 if ((QueuedAllocationWarningCount > 0) &&
661 (try_count % QueuedAllocationWarningCount == 0)) {
662 warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t"
663 " size=%d %s", try_count, size, is_tlab ? "(TLAB)" : "");
664 }
665 }
666 }
667
668 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size,
669 bool is_tlab) {
670 GenCollectedHeap *gch = GenCollectedHeap::heap();
671 HeapWord* result = NULL;
672 for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) {
673 Generation *gen = gch->get_gen(i);
674 if (gen->should_allocate(size, is_tlab)) {
675 result = gen->expand_and_allocate(size, is_tlab);
676 }
677 }
678 assert(result == NULL || gch->is_in_reserved(result), "result not in heap");
679 return result;
680 }
681
682 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size,
683 bool is_tlab) {
684 GenCollectedHeap *gch = GenCollectedHeap::heap();
685 GCCauseSetter x(gch, GCCause::_allocation_failure);
686 HeapWord* result = NULL;
687
688 assert(size != 0, "Precondition violated");
689 if (GC_locker::is_active_and_needs_gc()) {
690 // GC locker is active; instead of a collection we will attempt
691 // to expand the heap, if there's room for expansion.
692 if (!gch->is_maximal_no_gc()) {
693 result = expand_heap_and_allocate(size, is_tlab);
694 }
695 return result; // could be null if we are out of space
696 } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) {
697 // Do an incremental collection.
698 gch->do_collection(false /* full */,
699 false /* clear_all_soft_refs */,
700 size /* size */,
701 is_tlab /* is_tlab */,
702 number_of_generations() - 1 /* max_level */);
703 } else {
704 if (Verbose && PrintGCDetails) {
705 gclog_or_tty->print(" :: Trying full because partial may fail :: ");
706 }
707 // Try a full collection; see delta for bug id 6266275
708 // for the original code and why this has been simplified
709 // with from-space allocation criteria modified and
710 // such allocation moved out of the safepoint path.
711 gch->do_collection(true /* full */,
712 false /* clear_all_soft_refs */,
713 size /* size */,
714 is_tlab /* is_tlab */,
715 number_of_generations() - 1 /* max_level */);
716 }
717
718 result = gch->attempt_allocation(size, is_tlab, false /*first_only*/);
719
720 if (result != NULL) {
721 assert(gch->is_in_reserved(result), "result not in heap");
722 return result;
723 }
724
725 // OK, collection failed, try expansion.
726 result = expand_heap_and_allocate(size, is_tlab);
727 if (result != NULL) {
728 return result;
729 }
730
731 // If we reach this point, we're really out of memory. Try every trick
732 // we can to reclaim memory. Force collection of soft references. Force
733 // a complete compaction of the heap. Any additional methods for finding
734 // free memory should be here, especially if they are expensive. If this
735 // attempt fails, an OOM exception will be thrown.
736 {
737 IntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
738
739 gch->do_collection(true /* full */,
740 true /* clear_all_soft_refs */,
741 size /* size */,
742 is_tlab /* is_tlab */,
743 number_of_generations() - 1 /* max_level */);
744 }
745
746 result = gch->attempt_allocation(size, is_tlab, false /* first_only */);
747 if (result != NULL) {
748 assert(gch->is_in_reserved(result), "result not in heap");
749 return result;
750 }
751
752 assert(!should_clear_all_soft_refs(),
753 "Flag should have been handled and cleared prior to this point");
754
755 // What else? We might try synchronous finalization later. If the total
756 // space available is large enough for the allocation, then a more
757 // complete compaction phase than we've tried so far might be
758 // appropriate.
759 return NULL;
760 }
761
762 MetaWord* CollectorPolicy::satisfy_failed_metadata_allocation(
763 ClassLoaderData* loader_data,
764 size_t word_size,
765 Metaspace::MetadataType mdtype) {
766 uint loop_count = 0;
767 uint gc_count = 0;
768 uint full_gc_count = 0;
769
770 assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock");
771
772 do {
773 MetaWord* result = NULL;
774 if (GC_locker::is_active_and_needs_gc()) {
775 // If the GC_locker is active, just expand and allocate.
776 // If that does not succeed, wait if this thread is not
777 // in a critical section itself.
778 result =
779 loader_data->metaspace_non_null()->expand_and_allocate(word_size,
780 mdtype);
781 if (result != NULL) {
782 return result;
783 }
784 JavaThread* jthr = JavaThread::current();
785 if (!jthr->in_critical()) {
786 // Wait for JNI critical section to be exited
787 GC_locker::stall_until_clear();
788 // The GC invoked by the last thread leaving the critical
789 // section will be a young collection and a full collection
790 // is (currently) needed for unloading classes so continue
791 // to the next iteration to get a full GC.
792 continue;
793 } else {
794 if (CheckJNICalls) {
795 fatal("Possible deadlock due to allocating while"
796 " in jni critical section");
797 }
798 return NULL;
799 }
800 }
801
802 { // Need lock to get self consistent gc_count's
803 MutexLocker ml(Heap_lock);
804 gc_count = Universe::heap()->total_collections();
805 full_gc_count = Universe::heap()->total_full_collections();
806 }
807
808 // Generate a VM operation
809 VM_CollectForMetadataAllocation op(loader_data,
810 word_size,
811 mdtype,
812 gc_count,
813 full_gc_count,
814 GCCause::_metadata_GC_threshold);
815 VMThread::execute(&op);
816
817 // If GC was locked out, try again. Check
818 // before checking success because the prologue
819 // could have succeeded and the GC still have
820 // been locked out.
821 if (op.gc_locked()) {
822 continue;
823 }
824
825 if (op.prologue_succeeded()) {
826 return op.result();
827 }
828 loop_count++;
829 if ((QueuedAllocationWarningCount > 0) &&
830 (loop_count % QueuedAllocationWarningCount == 0)) {
831 warning("satisfy_failed_metadata_allocation() retries %d times \n\t"
832 " size=%d", loop_count, word_size);
833 }
834 } while (true); // Until a GC is done
835 }
836
837 // Return true if any of the following is true:
838 // . the allocation won't fit into the current young gen heap
839 // . gc locker is occupied (jni critical section)
840 // . heap memory is tight -- the most recent previous collection
841 // was a full collection because a partial collection (would
842 // have) failed and is likely to fail again
843 bool GenCollectorPolicy::should_try_older_generation_allocation(
844 size_t word_size) const {
845 GenCollectedHeap* gch = GenCollectedHeap::heap();
846 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();
847 return (word_size > heap_word_size(gen0_capacity))
848 || GC_locker::is_active_and_needs_gc()
849 || gch->incremental_collection_failed();
850 }
851
852
853 //
854 // MarkSweepPolicy methods
855 //
856
857 MarkSweepPolicy::MarkSweepPolicy() {
858 initialize_all();
859 }
860
861 void MarkSweepPolicy::initialize_generations() {
862 _generations = new GenerationSpecPtr[number_of_generations()];
863 if (_generations == NULL)
864 vm_exit_during_initialization("Unable to allocate gen spec");
865
866 if (UseParNewGC) {
867 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);
868 } else {
869 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);
870 }
871 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);
872
873 if (_generations[0] == NULL || _generations[1] == NULL)
874 vm_exit_during_initialization("Unable to allocate gen spec");
875 }
876
877 void MarkSweepPolicy::initialize_gc_policy_counters() {
878 // initialize the policy counters - 2 collectors, 3 generations
879 if (UseParNewGC) {
880 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);
881 } else {
882 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
883 }
884 }