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 size_t CollectorPolicy::compute_max_alignment() {
149 // The card marking array and the offset arrays for old generations are
150 // committed in os pages as well. Make sure they are entirely full (to
151 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
152 // byte entry and the os page size is 4096, the maximum heap size should
153 // be 512*4096 = 2MB aligned.
154
155 // there is only the GenRemSet in Hotspot and only the GenRemSet::CardTable
156 // is supported.
157 return GenRemSet::max_alignment_constraint(GenRemSet::CardTable);
158 }
159
160 // GenCollectorPolicy methods.
161
162 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {
163 size_t x = base_size / (NewRatio+1);
164 size_t new_gen_size = x > min_alignment() ?
165 align_size_down(x, min_alignment()) :
166 min_alignment();
167 return new_gen_size;
168 }
169
170 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,
171 size_t maximum_size) {
172 size_t alignment = min_alignment();
173 size_t max_minus = maximum_size - alignment;
174 return desired_size < max_minus ? desired_size : max_minus;
175 }
176
177
178 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size,
179 size_t init_promo_size,
180 size_t init_survivor_size) {
181 const double max_gc_pause_sec = ((double) MaxGCPauseMillis)/1000.0;
182 _size_policy = new AdaptiveSizePolicy(init_eden_size,
183 init_promo_size,
184 init_survivor_size,
185 max_gc_pause_sec,
186 GCTimeRatio);
187 }
188
189 void GenCollectorPolicy::initialize_flags() {
190 // All sizes must be multiples of the generation granularity.
191 set_min_alignment((uintx) Generation::GenGrain);
192 set_max_alignment(compute_max_alignment());
193
194 CollectorPolicy::initialize_flags();
195
196 // All generational heaps have a youngest gen; handle those flags here.
197
198 // Adjust max size parameters
199 if (NewSize > MaxNewSize) {
200 MaxNewSize = NewSize;
201 }
202 NewSize = align_size_down(NewSize, min_alignment());
203 MaxNewSize = align_size_down(MaxNewSize, min_alignment());
204
205 // Check validity of heap flags
206 assert(NewSize % min_alignment() == 0, "eden space alignment");
207 assert(MaxNewSize % min_alignment() == 0, "survivor space alignment");
208
209 if (NewSize < 3*min_alignment()) {
210 // make sure there room for eden and two survivor spaces
211 vm_exit_during_initialization("Too small new size specified");
212 }
213 if (SurvivorRatio < 1 || NewRatio < 1) {
214 vm_exit_during_initialization("Invalid heap ratio specified");
215 }
216 }
217
218 void TwoGenerationCollectorPolicy::initialize_flags() {
219 GenCollectorPolicy::initialize_flags();
220
221 OldSize = align_size_down(OldSize, min_alignment());
222
223 if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(NewSize)) {
224 // NewRatio will be used later to set the young generation size so we use
225 // it to calculate how big the heap should be based on the requested OldSize
226 // and NewRatio.
227 assert(NewRatio > 0, "NewRatio should have been set up earlier");
228 size_t calculated_heapsize = (OldSize / NewRatio) * (NewRatio + 1);
229
230 calculated_heapsize = align_size_up(calculated_heapsize, max_alignment());
231 MaxHeapSize = calculated_heapsize;
232 InitialHeapSize = calculated_heapsize;
233 }
234 MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
235
236 // adjust max heap size if necessary
237 if (NewSize + OldSize > MaxHeapSize) {
238 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
239 // somebody set a maximum heap size with the intention that we should not
240 // exceed it. Adjust New/OldSize as necessary.
241 uintx calculated_size = NewSize + OldSize;
242 double shrink_factor = (double) MaxHeapSize / calculated_size;
243 // align
244 NewSize = align_size_down((uintx) (NewSize * shrink_factor), min_alignment());
245 // OldSize is already aligned because above we aligned MaxHeapSize to
246 // max_alignment(), and we just made sure that NewSize is aligned to
247 // min_alignment(). In initialize_flags() we verified that max_alignment()
248 // is a multiple of min_alignment().
249 OldSize = MaxHeapSize - NewSize;
250 } else {
251 MaxHeapSize = NewSize + OldSize;
252 }
253 }
254 // need to do this again
255 MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
256
257 // adjust max heap size if necessary
258 if (NewSize + OldSize > MaxHeapSize) {
259 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
260 // somebody set a maximum heap size with the intention that we should not
261 // exceed it. Adjust New/OldSize as necessary.
262 uintx calculated_size = NewSize + OldSize;
263 double shrink_factor = (double) MaxHeapSize / calculated_size;
264 // align
265 NewSize = align_size_down((uintx) (NewSize * shrink_factor), min_alignment());
266 // OldSize is already aligned because above we aligned MaxHeapSize to
267 // max_alignment(), and we just made sure that NewSize is aligned to
268 // min_alignment(). In initialize_flags() we verified that max_alignment()
269 // is a multiple of min_alignment().
270 OldSize = MaxHeapSize - NewSize;
271 } else {
272 MaxHeapSize = NewSize + OldSize;
273 }
274 }
275 // need to do this again
276 MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
277
278 always_do_update_barrier = UseConcMarkSweepGC;
279
280 // Check validity of heap flags
281 assert(OldSize % min_alignment() == 0, "old space alignment");
282 assert(MaxHeapSize % max_alignment() == 0, "maximum heap alignment");
283 }
284
285 // Values set on the command line win over any ergonomically
286 // set command line parameters.
287 // Ergonomic choice of parameters are done before this
288 // method is called. Values for command line parameters such as NewSize
289 // and MaxNewSize feed those ergonomic choices into this method.
290 // This method makes the final generation sizings consistent with
291 // themselves and with overall heap sizings.
292 // In the absence of explicitly set command line flags, policies
293 // such as the use of NewRatio are used to size the generation.
294 void GenCollectorPolicy::initialize_size_info() {
295 CollectorPolicy::initialize_size_info();
296
297 // min_alignment() is used for alignment within a generation.
298 // There is additional alignment done down stream for some
299 // collectors that sometimes causes unwanted rounding up of
300 // generations sizes.
301
302 // Determine maximum size of gen0
303
304 size_t max_new_size = 0;
305 if (FLAG_IS_CMDLINE(MaxNewSize) || FLAG_IS_ERGO(MaxNewSize)) {
306 if (MaxNewSize < min_alignment()) {
307 max_new_size = min_alignment();
308 }
309 if (MaxNewSize >= max_heap_byte_size()) {
310 max_new_size = align_size_down(max_heap_byte_size() - min_alignment(),
311 min_alignment());
312 warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or "
313 "greater than the entire heap (" SIZE_FORMAT "k). A "
314 "new generation size of " SIZE_FORMAT "k will be used.",
315 MaxNewSize/K, max_heap_byte_size()/K, max_new_size/K);
316 } else {
317 max_new_size = align_size_down(MaxNewSize, min_alignment());
318 }
319
320 // The case for FLAG_IS_ERGO(MaxNewSize) could be treated
321 // specially at this point to just use an ergonomically set
322 // MaxNewSize to set max_new_size. For cases with small
323 // heaps such a policy often did not work because the MaxNewSize
324 // was larger than the entire heap. The interpretation given
325 // to ergonomically set flags is that the flags are set
326 // by different collectors for their own special needs but
327 // are not allowed to badly shape the heap. This allows the
328 // different collectors to decide what's best for themselves
329 // without having to factor in the overall heap shape. It
330 // can be the case in the future that the collectors would
331 // only make "wise" ergonomics choices and this policy could
332 // just accept those choices. The choices currently made are
333 // not always "wise".
334 } else {
335 max_new_size = scale_by_NewRatio_aligned(max_heap_byte_size());
336 // Bound the maximum size by NewSize below (since it historically
337 // would have been NewSize and because the NewRatio calculation could
338 // yield a size that is too small) and bound it by MaxNewSize above.
339 // Ergonomics plays here by previously calculating the desired
340 // NewSize and MaxNewSize.
341 max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize);
342 }
343 assert(max_new_size > 0, "All paths should set max_new_size");
344
345 // Given the maximum gen0 size, determine the initial and
346 // minimum gen0 sizes.
347
348 if (max_heap_byte_size() == min_heap_byte_size()) {
349 // The maximum and minimum heap sizes are the same so
350 // the generations minimum and initial must be the
351 // same as its maximum.
352 set_min_gen0_size(max_new_size);
353 set_initial_gen0_size(max_new_size);
354 set_max_gen0_size(max_new_size);
355 } else {
356 size_t desired_new_size = 0;
357 if (!FLAG_IS_DEFAULT(NewSize)) {
358 // If NewSize is set ergonomically (for example by cms), it
359 // would make sense to use it. If it is used, also use it
360 // to set the initial size. Although there is no reason
361 // the minimum size and the initial size have to be the same,
362 // the current implementation gets into trouble during the calculation
363 // of the tenured generation sizes if they are different.
364 // Note that this makes the initial size and the minimum size
365 // generally small compared to the NewRatio calculation.
366 _min_gen0_size = NewSize;
367 desired_new_size = NewSize;
368 max_new_size = MAX2(max_new_size, NewSize);
369 } else {
370 // For the case where NewSize is the default, use NewRatio
371 // to size the minimum and initial generation sizes.
372 // Use the default NewSize as the floor for these values. If
373 // NewRatio is overly large, the resulting sizes can be too
374 // small.
375 _min_gen0_size = MAX2(scale_by_NewRatio_aligned(min_heap_byte_size()),
376 NewSize);
377 desired_new_size =
378 MAX2(scale_by_NewRatio_aligned(initial_heap_byte_size()),
379 NewSize);
380 }
381
382 assert(_min_gen0_size > 0, "Sanity check");
383 set_initial_gen0_size(desired_new_size);
384 set_max_gen0_size(max_new_size);
385
386 // At this point the desirable initial and minimum sizes have been
387 // determined without regard to the maximum sizes.
388
389 // Bound the sizes by the corresponding overall heap sizes.
390 set_min_gen0_size(
391 bound_minus_alignment(_min_gen0_size, min_heap_byte_size()));
392 set_initial_gen0_size(
393 bound_minus_alignment(_initial_gen0_size, initial_heap_byte_size()));
394 set_max_gen0_size(
395 bound_minus_alignment(_max_gen0_size, max_heap_byte_size()));
396
397 // At this point all three sizes have been checked against the
398 // maximum sizes but have not been checked for consistency
399 // among the three.
400
401 // Final check min <= initial <= max
402 set_min_gen0_size(MIN2(_min_gen0_size, _max_gen0_size));
403 set_initial_gen0_size(
404 MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size));
405 set_min_gen0_size(MIN2(_min_gen0_size, _initial_gen0_size));
406 }
407
408 if (PrintGCDetails && Verbose) {
409 gclog_or_tty->print_cr("1: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
410 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
411 min_gen0_size(), initial_gen0_size(), max_gen0_size());
412 }
413 }
414
415 // Call this method during the sizing of the gen1 to make
416 // adjustments to gen0 because of gen1 sizing policy. gen0 initially has
417 // the most freedom in sizing because it is done before the
418 // policy for gen1 is applied. Once gen1 policies have been applied,
419 // there may be conflicts in the shape of the heap and this method
420 // is used to make the needed adjustments. The application of the
421 // policies could be more sophisticated (iterative for example) but
422 // keeping it simple also seems a worthwhile goal.
423 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr,
424 size_t* gen1_size_ptr,
425 const size_t heap_size,
426 const size_t min_gen1_size) {
427 bool result = false;
428
429 if ((*gen1_size_ptr + *gen0_size_ptr) > heap_size) {
430 if ((heap_size < (*gen0_size_ptr + min_gen1_size)) &&
431 (heap_size >= min_gen1_size + min_alignment())) {
432 // Adjust gen0 down to accommodate min_gen1_size
433 *gen0_size_ptr = heap_size - min_gen1_size;
434 *gen0_size_ptr =
435 MAX2((uintx)align_size_down(*gen0_size_ptr, min_alignment()),
436 min_alignment());
437 assert(*gen0_size_ptr > 0, "Min gen0 is too large");
438 result = true;
439 } else {
440 *gen1_size_ptr = heap_size - *gen0_size_ptr;
441 *gen1_size_ptr =
442 MAX2((uintx)align_size_down(*gen1_size_ptr, min_alignment()),
443 min_alignment());
444 }
445 }
446 return result;
447 }
448
449 // Minimum sizes of the generations may be different than
450 // the initial sizes. An inconsistently is permitted here
451 // in the total size that can be specified explicitly by
452 // command line specification of OldSize and NewSize and
453 // also a command line specification of -Xms. Issue a warning
454 // but allow the values to pass.
455
456 void TwoGenerationCollectorPolicy::initialize_size_info() {
457 GenCollectorPolicy::initialize_size_info();
458
459 // At this point the minimum, initial and maximum sizes
460 // of the overall heap and of gen0 have been determined.
461 // The maximum gen1 size can be determined from the maximum gen0
462 // and maximum heap size since no explicit flags exits
463 // for setting the gen1 maximum.
464 _max_gen1_size = max_heap_byte_size() - _max_gen0_size;
465 _max_gen1_size =
466 MAX2((uintx)align_size_down(_max_gen1_size, min_alignment()),
467 min_alignment());
468 // If no explicit command line flag has been set for the
469 // gen1 size, use what is left for gen1.
470 if (FLAG_IS_DEFAULT(OldSize) || FLAG_IS_ERGO(OldSize)) {
471 // The user has not specified any value or ergonomics
472 // has chosen a value (which may or may not be consistent
473 // with the overall heap size). In either case make
474 // the minimum, maximum and initial sizes consistent
475 // with the gen0 sizes and the overall heap sizes.
476 assert(min_heap_byte_size() > _min_gen0_size,
477 "gen0 has an unexpected minimum size");
478 set_min_gen1_size(min_heap_byte_size() - min_gen0_size());
479 set_min_gen1_size(
480 MAX2((uintx)align_size_down(_min_gen1_size, min_alignment()),
481 min_alignment()));
482 set_initial_gen1_size(initial_heap_byte_size() - initial_gen0_size());
483 set_initial_gen1_size(
484 MAX2((uintx)align_size_down(_initial_gen1_size, min_alignment()),
485 min_alignment()));
486
487 } else {
488 // It's been explicitly set on the command line. Use the
489 // OldSize and then determine the consequences.
490 set_min_gen1_size(OldSize);
491 set_initial_gen1_size(OldSize);
492
493 // If the user has explicitly set an OldSize that is inconsistent
494 // with other command line flags, issue a warning.
495 // The generation minimums and the overall heap mimimum should
496 // be within one heap alignment.
497 if ((_min_gen1_size + _min_gen0_size + min_alignment()) <
498 min_heap_byte_size()) {
499 warning("Inconsistency between minimum heap size and minimum "
500 "generation sizes: using minimum heap = " SIZE_FORMAT,
501 min_heap_byte_size());
502 }
503 if ((OldSize > _max_gen1_size)) {
504 warning("Inconsistency between maximum heap size and maximum "
505 "generation sizes: using maximum heap = " SIZE_FORMAT
506 " -XX:OldSize flag is being ignored",
507 max_heap_byte_size());
508 }
509 // If there is an inconsistency between the OldSize and the minimum and/or
510 // initial size of gen0, since OldSize was explicitly set, OldSize wins.
511 if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size,
512 min_heap_byte_size(), OldSize)) {
513 if (PrintGCDetails && Verbose) {
514 gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
515 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
516 min_gen0_size(), initial_gen0_size(), max_gen0_size());
517 }
518 }
519 // Initial size
520 if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,
521 initial_heap_byte_size(), OldSize)) {
522 if (PrintGCDetails && Verbose) {
523 gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
524 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
525 min_gen0_size(), initial_gen0_size(), max_gen0_size());
526 }
527 }
528 }
529 // Enforce the maximum gen1 size.
530 set_min_gen1_size(MIN2(_min_gen1_size, _max_gen1_size));
531
532 // Check that min gen1 <= initial gen1 <= max gen1
533 set_initial_gen1_size(MAX2(_initial_gen1_size, _min_gen1_size));
534 set_initial_gen1_size(MIN2(_initial_gen1_size, _max_gen1_size));
535
536 if (PrintGCDetails && Verbose) {
537 gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 "
538 SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT,
539 min_gen1_size(), initial_gen1_size(), max_gen1_size());
540 }
541 }
542
543 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
544 bool is_tlab,
545 bool* gc_overhead_limit_was_exceeded) {
546 GenCollectedHeap *gch = GenCollectedHeap::heap();
547
548 debug_only(gch->check_for_valid_allocation_state());
549 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
550
551 // In general gc_overhead_limit_was_exceeded should be false so
552 // set it so here and reset it to true only if the gc time
553 // limit is being exceeded as checked below.
554 *gc_overhead_limit_was_exceeded = false;
555
556 HeapWord* result = NULL;
557
558 // Loop until the allocation is satisified,
559 // or unsatisfied after GC.
560 for (int try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) {
561 HandleMark hm; // discard any handles allocated in each iteration
562
563 // First allocation attempt is lock-free.
564 Generation *gen0 = gch->get_gen(0);
565 assert(gen0->supports_inline_contig_alloc(),
566 "Otherwise, must do alloc within heap lock");
567 if (gen0->should_allocate(size, is_tlab)) {
568 result = gen0->par_allocate(size, is_tlab);
569 if (result != NULL) {
570 assert(gch->is_in_reserved(result), "result not in heap");
571 return result;
572 }
573 }
574 unsigned int gc_count_before; // read inside the Heap_lock locked region
575 {
576 MutexLocker ml(Heap_lock);
577 if (PrintGC && Verbose) {
578 gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:"
579 " attempting locked slow path allocation");
580 }
581 // Note that only large objects get a shot at being
582 // allocated in later generations.
583 bool first_only = ! should_try_older_generation_allocation(size);
584
585 result = gch->attempt_allocation(size, is_tlab, first_only);
586 if (result != NULL) {
587 assert(gch->is_in_reserved(result), "result not in heap");
588 return result;
589 }
590
591 if (GC_locker::is_active_and_needs_gc()) {
592 if (is_tlab) {
593 return NULL; // Caller will retry allocating individual object
594 }
595 if (!gch->is_maximal_no_gc()) {
596 // Try and expand heap to satisfy request
597 result = expand_heap_and_allocate(size, is_tlab);
598 // result could be null if we are out of space
599 if (result != NULL) {
600 return result;
601 }
602 }
603
604 if (gclocker_stalled_count > GCLockerRetryAllocationCount) {
605 return NULL; // we didn't get to do a GC and we didn't get any memory
606 }
607
608 // If this thread is not in a jni critical section, we stall
609 // the requestor until the critical section has cleared and
610 // GC allowed. When the critical section clears, a GC is
611 // initiated by the last thread exiting the critical section; so
612 // we retry the allocation sequence from the beginning of the loop,
613 // rather than causing more, now probably unnecessary, GC attempts.
614 JavaThread* jthr = JavaThread::current();
615 if (!jthr->in_critical()) {
616 MutexUnlocker mul(Heap_lock);
617 // Wait for JNI critical section to be exited
618 GC_locker::stall_until_clear();
619 gclocker_stalled_count += 1;
620 continue;
621 } else {
622 if (CheckJNICalls) {
623 fatal("Possible deadlock due to allocating while"
624 " in jni critical section");
625 }
626 return NULL;
627 }
628 }
629
630 // Read the gc count while the heap lock is held.
631 gc_count_before = Universe::heap()->total_collections();
632 }
633
634 VM_GenCollectForAllocation op(size,
635 is_tlab,
636 gc_count_before);
637 VMThread::execute(&op);
638 if (op.prologue_succeeded()) {
639 result = op.result();
640 if (op.gc_locked()) {
641 assert(result == NULL, "must be NULL if gc_locked() is true");
642 continue; // retry and/or stall as necessary
643 }
644
645 // Allocation has failed and a collection
646 // has been done. If the gc time limit was exceeded the
647 // this time, return NULL so that an out-of-memory
648 // will be thrown. Clear gc_overhead_limit_exceeded
649 // so that the overhead exceeded does not persist.
650
651 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
652 const bool softrefs_clear = all_soft_refs_clear();
653
654 if (limit_exceeded && softrefs_clear) {
655 *gc_overhead_limit_was_exceeded = true;
656 size_policy()->set_gc_overhead_limit_exceeded(false);
657 if (op.result() != NULL) {
658 CollectedHeap::fill_with_object(op.result(), size);
659 }
660 return NULL;
661 }
662 assert(result == NULL || gch->is_in_reserved(result),
663 "result not in heap");
664 return result;
665 }
666
667 // Give a warning if we seem to be looping forever.
668 if ((QueuedAllocationWarningCount > 0) &&
669 (try_count % QueuedAllocationWarningCount == 0)) {
670 warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t"
671 " size=%d %s", try_count, size, is_tlab ? "(TLAB)" : "");
672 }
673 }
674 }
675
676 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size,
677 bool is_tlab) {
678 GenCollectedHeap *gch = GenCollectedHeap::heap();
679 HeapWord* result = NULL;
680 for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) {
681 Generation *gen = gch->get_gen(i);
682 if (gen->should_allocate(size, is_tlab)) {
683 result = gen->expand_and_allocate(size, is_tlab);
684 }
685 }
686 assert(result == NULL || gch->is_in_reserved(result), "result not in heap");
687 return result;
688 }
689
690 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size,
691 bool is_tlab) {
692 GenCollectedHeap *gch = GenCollectedHeap::heap();
693 GCCauseSetter x(gch, GCCause::_allocation_failure);
694 HeapWord* result = NULL;
695
696 assert(size != 0, "Precondition violated");
697 if (GC_locker::is_active_and_needs_gc()) {
698 // GC locker is active; instead of a collection we will attempt
699 // to expand the heap, if there's room for expansion.
700 if (!gch->is_maximal_no_gc()) {
701 result = expand_heap_and_allocate(size, is_tlab);
702 }
703 return result; // could be null if we are out of space
704 } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) {
705 // Do an incremental collection.
706 gch->do_collection(false /* full */,
707 false /* clear_all_soft_refs */,
708 size /* size */,
709 is_tlab /* is_tlab */,
710 number_of_generations() - 1 /* max_level */);
711 } else {
712 if (Verbose && PrintGCDetails) {
713 gclog_or_tty->print(" :: Trying full because partial may fail :: ");
714 }
715 // Try a full collection; see delta for bug id 6266275
716 // for the original code and why this has been simplified
717 // with from-space allocation criteria modified and
718 // such allocation moved out of the safepoint path.
719 gch->do_collection(true /* full */,
720 false /* clear_all_soft_refs */,
721 size /* size */,
722 is_tlab /* is_tlab */,
723 number_of_generations() - 1 /* max_level */);
724 }
725
726 result = gch->attempt_allocation(size, is_tlab, false /*first_only*/);
727
728 if (result != NULL) {
729 assert(gch->is_in_reserved(result), "result not in heap");
730 return result;
731 }
732
733 // OK, collection failed, try expansion.
734 result = expand_heap_and_allocate(size, is_tlab);
735 if (result != NULL) {
736 return result;
737 }
738
739 // If we reach this point, we're really out of memory. Try every trick
740 // we can to reclaim memory. Force collection of soft references. Force
741 // a complete compaction of the heap. Any additional methods for finding
742 // free memory should be here, especially if they are expensive. If this
743 // attempt fails, an OOM exception will be thrown.
744 {
745 IntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
746
747 gch->do_collection(true /* full */,
748 true /* clear_all_soft_refs */,
749 size /* size */,
750 is_tlab /* is_tlab */,
751 number_of_generations() - 1 /* max_level */);
752 }
753
754 result = gch->attempt_allocation(size, is_tlab, false /* first_only */);
755 if (result != NULL) {
756 assert(gch->is_in_reserved(result), "result not in heap");
757 return result;
758 }
759
760 assert(!should_clear_all_soft_refs(),
761 "Flag should have been handled and cleared prior to this point");
762
763 // What else? We might try synchronous finalization later. If the total
764 // space available is large enough for the allocation, then a more
765 // complete compaction phase than we've tried so far might be
766 // appropriate.
767 return NULL;
768 }
769
770 MetaWord* CollectorPolicy::satisfy_failed_metadata_allocation(
771 ClassLoaderData* loader_data,
772 size_t word_size,
773 Metaspace::MetadataType mdtype) {
774 uint loop_count = 0;
775 uint gc_count = 0;
776 uint full_gc_count = 0;
777
778 assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock");
779
780 do {
781 MetaWord* result = NULL;
782 if (GC_locker::is_active_and_needs_gc()) {
783 // If the GC_locker is active, just expand and allocate.
784 // If that does not succeed, wait if this thread is not
785 // in a critical section itself.
786 result =
787 loader_data->metaspace_non_null()->expand_and_allocate(word_size,
788 mdtype);
789 if (result != NULL) {
790 return result;
791 }
792 JavaThread* jthr = JavaThread::current();
793 if (!jthr->in_critical()) {
794 // Wait for JNI critical section to be exited
795 GC_locker::stall_until_clear();
796 // The GC invoked by the last thread leaving the critical
797 // section will be a young collection and a full collection
798 // is (currently) needed for unloading classes so continue
799 // to the next iteration to get a full GC.
800 continue;
801 } else {
802 if (CheckJNICalls) {
803 fatal("Possible deadlock due to allocating while"
804 " in jni critical section");
805 }
806 return NULL;
807 }
808 }
809
810 { // Need lock to get self consistent gc_count's
811 MutexLocker ml(Heap_lock);
812 gc_count = Universe::heap()->total_collections();
813 full_gc_count = Universe::heap()->total_full_collections();
814 }
815
816 // Generate a VM operation
817 VM_CollectForMetadataAllocation op(loader_data,
818 word_size,
819 mdtype,
820 gc_count,
821 full_gc_count,
822 GCCause::_metadata_GC_threshold);
823 VMThread::execute(&op);
824
825 // If GC was locked out, try again. Check
826 // before checking success because the prologue
827 // could have succeeded and the GC still have
828 // been locked out.
829 if (op.gc_locked()) {
830 continue;
831 }
832
833 if (op.prologue_succeeded()) {
834 return op.result();
835 }
836 loop_count++;
837 if ((QueuedAllocationWarningCount > 0) &&
838 (loop_count % QueuedAllocationWarningCount == 0)) {
839 warning("satisfy_failed_metadata_allocation() retries %d times \n\t"
840 " size=%d", loop_count, word_size);
841 }
842 } while (true); // Until a GC is done
843 }
844
845 // Return true if any of the following is true:
846 // . the allocation won't fit into the current young gen heap
847 // . gc locker is occupied (jni critical section)
848 // . heap memory is tight -- the most recent previous collection
849 // was a full collection because a partial collection (would
850 // have) failed and is likely to fail again
851 bool GenCollectorPolicy::should_try_older_generation_allocation(
852 size_t word_size) const {
853 GenCollectedHeap* gch = GenCollectedHeap::heap();
854 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();
855 return (word_size > heap_word_size(gen0_capacity))
856 || GC_locker::is_active_and_needs_gc()
857 || gch->incremental_collection_failed();
858 }
859
860
861 //
862 // MarkSweepPolicy methods
863 //
864
865 MarkSweepPolicy::MarkSweepPolicy() {
866 initialize_all();
867 }
868
869 void MarkSweepPolicy::initialize_generations() {
870 _generations = new GenerationSpecPtr[number_of_generations()];
871 if (_generations == NULL)
872 vm_exit_during_initialization("Unable to allocate gen spec");
873
874 if (UseParNewGC) {
875 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);
876 } else {
877 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);
878 }
879 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);
880
881 if (_generations[0] == NULL || _generations[1] == NULL)
882 vm_exit_during_initialization("Unable to allocate gen spec");
883 }
884
885 void MarkSweepPolicy::initialize_gc_policy_counters() {
886 // initialize the policy counters - 2 collectors, 3 generations
887 if (UseParNewGC) {
888 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);
889 } else {
890 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
891 }
892 }