1 /*
2 * Copyright (c) 2001, 2011, 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/vmThread.hpp"
41 #ifdef TARGET_OS_FAMILY_linux
42 # include "thread_linux.inline.hpp"
43 #endif
44 #ifdef TARGET_OS_FAMILY_solaris
45 # include "thread_solaris.inline.hpp"
46 #endif
47 #ifdef TARGET_OS_FAMILY_windows
48 # include "thread_windows.inline.hpp"
49 #endif
50 #ifndef SERIALGC
51 #include "gc_implementation/concurrentMarkSweep/cmsAdaptiveSizePolicy.hpp"
52 #include "gc_implementation/concurrentMarkSweep/cmsGCAdaptivePolicyCounters.hpp"
53 #endif
54
55 // CollectorPolicy methods.
56
57 void CollectorPolicy::initialize_flags() {
58 if (PermSize > MaxPermSize) {
59 MaxPermSize = PermSize;
60 }
61 PermSize = MAX2(min_alignment(), align_size_down_(PermSize, min_alignment()));
62 // Don't increase Perm size limit above specified.
63 MaxPermSize = align_size_down(MaxPermSize, max_alignment());
64 if (PermSize > MaxPermSize) {
65 PermSize = MaxPermSize;
66 }
67
68 MinPermHeapExpansion = MAX2(min_alignment(), align_size_down_(MinPermHeapExpansion, min_alignment()));
69 MaxPermHeapExpansion = MAX2(min_alignment(), align_size_down_(MaxPermHeapExpansion, min_alignment()));
70
71 MinHeapDeltaBytes = align_size_up(MinHeapDeltaBytes, min_alignment());
72
73 SharedReadOnlySize = align_size_up(SharedReadOnlySize, max_alignment());
74 SharedReadWriteSize = align_size_up(SharedReadWriteSize, max_alignment());
75 SharedMiscDataSize = align_size_up(SharedMiscDataSize, max_alignment());
76
77 assert(PermSize % min_alignment() == 0, "permanent space alignment");
78 assert(MaxPermSize % max_alignment() == 0, "maximum permanent space alignment");
79 assert(SharedReadOnlySize % max_alignment() == 0, "read-only space alignment");
80 assert(SharedReadWriteSize % max_alignment() == 0, "read-write space alignment");
81 assert(SharedMiscDataSize % max_alignment() == 0, "misc-data space alignment");
82 if (PermSize < M) {
83 vm_exit_during_initialization("Too small initial permanent heap");
84 }
85 }
86
87 void CollectorPolicy::initialize_size_info() {
88 // User inputs from -mx and ms are aligned
89 set_initial_heap_byte_size(InitialHeapSize);
90 if (initial_heap_byte_size() == 0) {
91 set_initial_heap_byte_size(NewSize + OldSize);
92 }
93 set_initial_heap_byte_size(align_size_up(_initial_heap_byte_size,
94 min_alignment()));
95
96 set_min_heap_byte_size(Arguments::min_heap_size());
97 if (min_heap_byte_size() == 0) {
98 set_min_heap_byte_size(NewSize + OldSize);
99 }
100 set_min_heap_byte_size(align_size_up(_min_heap_byte_size,
101 min_alignment()));
102
103 set_max_heap_byte_size(align_size_up(MaxHeapSize, max_alignment()));
104
105 // Check heap parameter properties
106 if (initial_heap_byte_size() < M) {
107 vm_exit_during_initialization("Too small initial heap");
108 }
109 // Check heap parameter properties
110 if (min_heap_byte_size() < M) {
111 vm_exit_during_initialization("Too small minimum heap");
112 }
113 if (initial_heap_byte_size() <= NewSize) {
114 // make sure there is at least some room in old space
115 vm_exit_during_initialization("Too small initial heap for new size specified");
116 }
117 if (max_heap_byte_size() < min_heap_byte_size()) {
118 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified");
119 }
120 if (initial_heap_byte_size() < min_heap_byte_size()) {
121 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified");
122 }
123 if (max_heap_byte_size() < initial_heap_byte_size()) {
124 vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
125 }
126
127 if (PrintGCDetails && Verbose) {
128 gclog_or_tty->print_cr("Minimum heap " SIZE_FORMAT " Initial heap "
129 SIZE_FORMAT " Maximum heap " SIZE_FORMAT,
130 min_heap_byte_size(), initial_heap_byte_size(), max_heap_byte_size());
131 }
132 }
133
134 void CollectorPolicy::initialize_perm_generation(PermGen::Name pgnm) {
135 _permanent_generation =
136 new PermanentGenerationSpec(pgnm, PermSize, MaxPermSize,
137 SharedReadOnlySize,
138 SharedReadWriteSize,
139 SharedMiscDataSize,
140 SharedMiscCodeSize);
141 if (_permanent_generation == NULL) {
142 vm_exit_during_initialization("Unable to allocate gen spec");
143 }
144 }
145
146 bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) {
147 bool result = _should_clear_all_soft_refs;
148 set_should_clear_all_soft_refs(false);
149 return result;
150 }
151
152 GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap,
153 int max_covered_regions) {
154 switch (rem_set_name()) {
155 case GenRemSet::CardTable: {
156 CardTableRS* res = new CardTableRS(whole_heap, max_covered_regions);
157 return res;
158 }
159 default:
160 guarantee(false, "unrecognized GenRemSet::Name");
161 return NULL;
162 }
163 }
164
165 void CollectorPolicy::cleared_all_soft_refs() {
166 // If near gc overhear limit, continue to clear SoftRefs. SoftRefs may
167 // have been cleared in the last collection but if the gc overhear
168 // limit continues to be near, SoftRefs should still be cleared.
169 if (size_policy() != NULL) {
170 _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near();
171 }
172 _all_soft_refs_clear = true;
173 }
174
175
176 // GenCollectorPolicy methods.
177
178 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {
179 size_t x = base_size / (NewRatio+1);
180 size_t new_gen_size = x > min_alignment() ?
181 align_size_down(x, min_alignment()) :
182 min_alignment();
183 return new_gen_size;
184 }
185
186 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,
187 size_t maximum_size) {
188 size_t alignment = min_alignment();
189 size_t max_minus = maximum_size - alignment;
190 return desired_size < max_minus ? desired_size : max_minus;
191 }
192
193
194 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size,
195 size_t init_promo_size,
196 size_t init_survivor_size) {
197 const double max_gc_minor_pause_sec = ((double) MaxGCMinorPauseMillis)/1000.0;
198 _size_policy = new AdaptiveSizePolicy(init_eden_size,
199 init_promo_size,
200 init_survivor_size,
201 max_gc_minor_pause_sec,
202 GCTimeRatio);
203 }
204
205 size_t GenCollectorPolicy::compute_max_alignment() {
206 // The card marking array and the offset arrays for old generations are
207 // committed in os pages as well. Make sure they are entirely full (to
208 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
209 // byte entry and the os page size is 4096, the maximum heap size should
210 // be 512*4096 = 2MB aligned.
211 size_t alignment = GenRemSet::max_alignment_constraint(rem_set_name());
212
213 // Parallel GC does its own alignment of the generations to avoid requiring a
214 // large page (256M on some platforms) for the permanent generation. The
215 // other collectors should also be updated to do their own alignment and then
216 // this use of lcm() should be removed.
217 if (UseLargePages && !UseParallelGC) {
218 // in presence of large pages we have to make sure that our
219 // alignment is large page aware
220 alignment = lcm(os::large_page_size(), alignment);
221 }
222
223 return alignment;
224 }
225
226 void GenCollectorPolicy::initialize_flags() {
227 // All sizes must be multiples of the generation granularity.
228 set_min_alignment((uintx) Generation::GenGrain);
229 set_max_alignment(compute_max_alignment());
230 assert(max_alignment() >= min_alignment() &&
231 max_alignment() % min_alignment() == 0,
232 "invalid alignment constraints");
233
234 CollectorPolicy::initialize_flags();
235
236 // All generational heaps have a youngest gen; handle those flags here.
237
238 // Adjust max size parameters
239 if (NewSize > MaxNewSize) {
240 MaxNewSize = NewSize;
241 }
242 NewSize = align_size_down(NewSize, min_alignment());
243 MaxNewSize = align_size_down(MaxNewSize, min_alignment());
244
245 // Check validity of heap flags
246 assert(NewSize % min_alignment() == 0, "eden space alignment");
247 assert(MaxNewSize % min_alignment() == 0, "survivor space alignment");
248
249 if (NewSize < 3*min_alignment()) {
250 // make sure there room for eden and two survivor spaces
251 vm_exit_during_initialization("Too small new size specified");
252 }
253 if (SurvivorRatio < 1 || NewRatio < 1) {
254 vm_exit_during_initialization("Invalid heap ratio specified");
255 }
256 }
257
258 void TwoGenerationCollectorPolicy::initialize_flags() {
259 GenCollectorPolicy::initialize_flags();
260
261 OldSize = align_size_down(OldSize, min_alignment());
262 if (NewSize + OldSize > MaxHeapSize) {
263 MaxHeapSize = NewSize + OldSize;
264 }
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 size_t heap_size,
415 size_t min_gen0_size) {
416 bool result = false;
417 if ((*gen1_size_ptr + *gen0_size_ptr) > heap_size) {
418 if (((*gen0_size_ptr + OldSize) > heap_size) &&
419 (heap_size - min_gen0_size) >= min_alignment()) {
420 // Adjust gen0 down to accomodate OldSize
421 *gen0_size_ptr = heap_size - min_gen0_size;
422 *gen0_size_ptr =
423 MAX2((uintx)align_size_down(*gen0_size_ptr, min_alignment()),
424 min_alignment());
425 assert(*gen0_size_ptr > 0, "Min gen0 is too large");
426 result = true;
427 } else {
428 *gen1_size_ptr = heap_size - *gen0_size_ptr;
429 *gen1_size_ptr =
430 MAX2((uintx)align_size_down(*gen1_size_ptr, min_alignment()),
431 min_alignment());
432 }
433 }
434 return result;
435 }
436
437 // Minimum sizes of the generations may be different than
438 // the initial sizes. An inconsistently is permitted here
439 // in the total size that can be specified explicitly by
440 // command line specification of OldSize and NewSize and
441 // also a command line specification of -Xms. Issue a warning
442 // but allow the values to pass.
443
444 void TwoGenerationCollectorPolicy::initialize_size_info() {
445 GenCollectorPolicy::initialize_size_info();
446
447 // At this point the minimum, initial and maximum sizes
448 // of the overall heap and of gen0 have been determined.
449 // The maximum gen1 size can be determined from the maximum gen0
450 // and maximum heap size since no explicit flags exits
451 // for setting the gen1 maximum.
452 _max_gen1_size = max_heap_byte_size() - _max_gen0_size;
453 _max_gen1_size =
454 MAX2((uintx)align_size_down(_max_gen1_size, min_alignment()),
455 min_alignment());
456 // If no explicit command line flag has been set for the
457 // gen1 size, use what is left for gen1.
458 if (FLAG_IS_DEFAULT(OldSize) || FLAG_IS_ERGO(OldSize)) {
459 // The user has not specified any value or ergonomics
460 // has chosen a value (which may or may not be consistent
461 // with the overall heap size). In either case make
462 // the minimum, maximum and initial sizes consistent
463 // with the gen0 sizes and the overall heap sizes.
464 assert(min_heap_byte_size() > _min_gen0_size,
465 "gen0 has an unexpected minimum size");
466 set_min_gen1_size(min_heap_byte_size() - min_gen0_size());
467 set_min_gen1_size(
468 MAX2((uintx)align_size_down(_min_gen1_size, min_alignment()),
469 min_alignment()));
470 set_initial_gen1_size(initial_heap_byte_size() - initial_gen0_size());
471 set_initial_gen1_size(
472 MAX2((uintx)align_size_down(_initial_gen1_size, min_alignment()),
473 min_alignment()));
474
475 } else {
476 // It's been explicitly set on the command line. Use the
477 // OldSize and then determine the consequences.
478 set_min_gen1_size(OldSize);
479 set_initial_gen1_size(OldSize);
480
481 // If the user has explicitly set an OldSize that is inconsistent
482 // with other command line flags, issue a warning.
483 // The generation minimums and the overall heap mimimum should
484 // be within one heap alignment.
485 if ((_min_gen1_size + _min_gen0_size + min_alignment()) <
486 min_heap_byte_size()) {
487 warning("Inconsistency between minimum heap size and minimum "
488 "generation sizes: using minimum heap = " SIZE_FORMAT,
489 min_heap_byte_size());
490 }
491 if ((OldSize > _max_gen1_size)) {
492 warning("Inconsistency between maximum heap size and maximum "
493 "generation sizes: using maximum heap = " SIZE_FORMAT
494 " -XX:OldSize flag is being ignored",
495 max_heap_byte_size());
496 }
497 // If there is an inconsistency between the OldSize and the minimum and/or
498 // initial size of gen0, since OldSize was explicitly set, OldSize wins.
499 if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size,
500 min_heap_byte_size(), OldSize)) {
501 if (PrintGCDetails && Verbose) {
502 gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
503 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
504 min_gen0_size(), initial_gen0_size(), max_gen0_size());
505 }
506 }
507 // Initial size
508 if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,
509 initial_heap_byte_size(), OldSize)) {
510 if (PrintGCDetails && Verbose) {
511 gclog_or_tty->print_cr("3: 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 }
517 // Enforce the maximum gen1 size.
518 set_min_gen1_size(MIN2(_min_gen1_size, _max_gen1_size));
519
520 // Check that min gen1 <= initial gen1 <= max gen1
521 set_initial_gen1_size(MAX2(_initial_gen1_size, _min_gen1_size));
522 set_initial_gen1_size(MIN2(_initial_gen1_size, _max_gen1_size));
523
524 if (PrintGCDetails && Verbose) {
525 gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 "
526 SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT,
527 min_gen1_size(), initial_gen1_size(), max_gen1_size());
528 }
529 }
530
531 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
532 bool is_tlab,
533 bool* gc_overhead_limit_was_exceeded) {
534 GenCollectedHeap *gch = GenCollectedHeap::heap();
535
536 debug_only(gch->check_for_valid_allocation_state());
537 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
538
539 // In general gc_overhead_limit_was_exceeded should be false so
540 // set it so here and reset it to true only if the gc time
541 // limit is being exceeded as checked below.
542 *gc_overhead_limit_was_exceeded = false;
543
544 HeapWord* result = NULL;
545
546 // Loop until the allocation is satisified,
547 // or unsatisfied after GC.
548 for (int try_count = 1; /* return or throw */; try_count += 1) {
549 HandleMark hm; // discard any handles allocated in each iteration
550
551 // First allocation attempt is lock-free.
552 Generation *gen0 = gch->get_gen(0);
553 assert(gen0->supports_inline_contig_alloc(),
554 "Otherwise, must do alloc within heap lock");
555 if (gen0->should_allocate(size, is_tlab)) {
556 result = gen0->par_allocate(size, is_tlab);
557 if (result != NULL) {
558 assert(gch->is_in_reserved(result), "result not in heap");
559 return result;
560 }
561 }
562 unsigned int gc_count_before; // read inside the Heap_lock locked region
563 {
564 MutexLocker ml(Heap_lock);
565 if (PrintGC && Verbose) {
566 gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:"
567 " attempting locked slow path allocation");
568 }
569 // Note that only large objects get a shot at being
570 // allocated in later generations.
571 bool first_only = ! should_try_older_generation_allocation(size);
572
573 result = gch->attempt_allocation(size, is_tlab, first_only);
574 if (result != NULL) {
575 assert(gch->is_in_reserved(result), "result not in heap");
576 return result;
577 }
578
579 if (GC_locker::is_active_and_needs_gc()) {
580 if (is_tlab) {
581 return NULL; // Caller will retry allocating individual object
582 }
583 if (!gch->is_maximal_no_gc()) {
584 // Try and expand heap to satisfy request
585 result = expand_heap_and_allocate(size, is_tlab);
586 // result could be null if we are out of space
587 if (result != NULL) {
588 return result;
589 }
590 }
591
592 // If this thread is not in a jni critical section, we stall
593 // the requestor until the critical section has cleared and
594 // GC allowed. When the critical section clears, a GC is
595 // initiated by the last thread exiting the critical section; so
596 // we retry the allocation sequence from the beginning of the loop,
597 // rather than causing more, now probably unnecessary, GC attempts.
598 JavaThread* jthr = JavaThread::current();
599 if (!jthr->in_critical()) {
600 MutexUnlocker mul(Heap_lock);
601 // Wait for JNI critical section to be exited
602 GC_locker::stall_until_clear();
603 continue;
604 } else {
605 if (CheckJNICalls) {
606 fatal("Possible deadlock due to allocating while"
607 " in jni critical section");
608 }
609 return NULL;
610 }
611 }
612
613 // Read the gc count while the heap lock is held.
614 gc_count_before = Universe::heap()->total_collections();
615 }
616
617 VM_GenCollectForAllocation op(size,
618 is_tlab,
619 gc_count_before);
620 VMThread::execute(&op);
621 if (op.prologue_succeeded()) {
622 result = op.result();
623 if (op.gc_locked()) {
624 assert(result == NULL, "must be NULL if gc_locked() is true");
625 continue; // retry and/or stall as necessary
626 }
627
628 // Allocation has failed and a collection
629 // has been done. If the gc time limit was exceeded the
630 // this time, return NULL so that an out-of-memory
631 // will be thrown. Clear gc_overhead_limit_exceeded
632 // so that the overhead exceeded does not persist.
633
634 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
635 const bool softrefs_clear = all_soft_refs_clear();
636 assert(!limit_exceeded || softrefs_clear, "Should have been cleared");
637 if (limit_exceeded && softrefs_clear) {
638 *gc_overhead_limit_was_exceeded = true;
639 size_policy()->set_gc_overhead_limit_exceeded(false);
640 if (op.result() != NULL) {
641 CollectedHeap::fill_with_object(op.result(), size);
642 }
643 return NULL;
644 }
645 assert(result == NULL || gch->is_in_reserved(result),
646 "result not in heap");
647 return result;
648 }
649
650 // Give a warning if we seem to be looping forever.
651 if ((QueuedAllocationWarningCount > 0) &&
652 (try_count % QueuedAllocationWarningCount == 0)) {
653 warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t"
654 " size=%d %s", try_count, size, is_tlab ? "(TLAB)" : "");
655 }
656 }
657 }
658
659 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size,
660 bool is_tlab) {
661 GenCollectedHeap *gch = GenCollectedHeap::heap();
662 HeapWord* result = NULL;
663 for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) {
664 Generation *gen = gch->get_gen(i);
665 if (gen->should_allocate(size, is_tlab)) {
666 result = gen->expand_and_allocate(size, is_tlab);
667 }
668 }
669 assert(result == NULL || gch->is_in_reserved(result), "result not in heap");
670 return result;
671 }
672
673 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size,
674 bool is_tlab) {
675 GenCollectedHeap *gch = GenCollectedHeap::heap();
676 GCCauseSetter x(gch, GCCause::_allocation_failure);
677 HeapWord* result = NULL;
678
679 assert(size != 0, "Precondition violated");
680 if (GC_locker::is_active_and_needs_gc()) {
681 // GC locker is active; instead of a collection we will attempt
682 // to expand the heap, if there's room for expansion.
683 if (!gch->is_maximal_no_gc()) {
684 result = expand_heap_and_allocate(size, is_tlab);
685 }
686 return result; // could be null if we are out of space
687 } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) {
688 // Do an incremental collection.
689 gch->do_collection(false /* full */,
690 false /* clear_all_soft_refs */,
691 size /* size */,
692 is_tlab /* is_tlab */,
693 number_of_generations() - 1 /* max_level */);
694 } else {
695 if (Verbose && PrintGCDetails) {
696 gclog_or_tty->print(" :: Trying full because partial may fail :: ");
697 }
698 // Try a full collection; see delta for bug id 6266275
699 // for the original code and why this has been simplified
700 // with from-space allocation criteria modified and
701 // such allocation moved out of the safepoint path.
702 gch->do_collection(true /* full */,
703 false /* clear_all_soft_refs */,
704 size /* size */,
705 is_tlab /* is_tlab */,
706 number_of_generations() - 1 /* max_level */);
707 }
708
709 result = gch->attempt_allocation(size, is_tlab, false /*first_only*/);
710
711 if (result != NULL) {
712 assert(gch->is_in_reserved(result), "result not in heap");
713 return result;
714 }
715
716 // OK, collection failed, try expansion.
717 result = expand_heap_and_allocate(size, is_tlab);
718 if (result != NULL) {
719 return result;
720 }
721
722 // If we reach this point, we're really out of memory. Try every trick
723 // we can to reclaim memory. Force collection of soft references. Force
724 // a complete compaction of the heap. Any additional methods for finding
725 // free memory should be here, especially if they are expensive. If this
726 // attempt fails, an OOM exception will be thrown.
727 {
728 IntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
729
730 gch->do_collection(true /* full */,
731 true /* clear_all_soft_refs */,
732 size /* size */,
733 is_tlab /* is_tlab */,
734 number_of_generations() - 1 /* max_level */);
735 }
736
737 result = gch->attempt_allocation(size, is_tlab, false /* first_only */);
738 if (result != NULL) {
739 assert(gch->is_in_reserved(result), "result not in heap");
740 return result;
741 }
742
743 assert(!should_clear_all_soft_refs(),
744 "Flag should have been handled and cleared prior to this point");
745
746 // What else? We might try synchronous finalization later. If the total
747 // space available is large enough for the allocation, then a more
748 // complete compaction phase than we've tried so far might be
749 // appropriate.
750 return NULL;
751 }
752
753 // Return true if any of the following is true:
754 // . the allocation won't fit into the current young gen heap
755 // . gc locker is occupied (jni critical section)
756 // . heap memory is tight -- the most recent previous collection
757 // was a full collection because a partial collection (would
758 // have) failed and is likely to fail again
759 bool GenCollectorPolicy::should_try_older_generation_allocation(
760 size_t word_size) const {
761 GenCollectedHeap* gch = GenCollectedHeap::heap();
762 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();
763 return (word_size > heap_word_size(gen0_capacity))
764 || GC_locker::is_active_and_needs_gc()
765 || gch->incremental_collection_failed();
766 }
767
768
769 //
770 // MarkSweepPolicy methods
771 //
772
773 MarkSweepPolicy::MarkSweepPolicy() {
774 initialize_all();
775 }
776
777 void MarkSweepPolicy::initialize_generations() {
778 initialize_perm_generation(PermGen::MarkSweepCompact);
779 _generations = new GenerationSpecPtr[number_of_generations()];
780 if (_generations == NULL)
781 vm_exit_during_initialization("Unable to allocate gen spec");
782
783 if (UseParNewGC && ParallelGCThreads > 0) {
784 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);
785 } else {
786 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);
787 }
788 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);
789
790 if (_generations[0] == NULL || _generations[1] == NULL)
791 vm_exit_during_initialization("Unable to allocate gen spec");
792 }
793
794 void MarkSweepPolicy::initialize_gc_policy_counters() {
795 // initialize the policy counters - 2 collectors, 3 generations
796 if (UseParNewGC && ParallelGCThreads > 0) {
797 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);
798 }
799 else {
800 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
801 }
802 }