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