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