Thu, 12 Jun 2008 13:50:55 -0700
Merge
1 /*
2 * Copyright 2001-2007 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
25 # include "incls/_precompiled.incl"
26 # include "incls/_collectorPolicy.cpp.incl"
28 // CollectorPolicy methods.
30 void CollectorPolicy::initialize_flags() {
31 if (PermSize > MaxPermSize) {
32 MaxPermSize = PermSize;
33 }
34 PermSize = MAX2(min_alignment(), align_size_down_(PermSize, min_alignment()));
35 MaxPermSize = align_size_up(MaxPermSize, max_alignment());
37 MinPermHeapExpansion = MAX2(min_alignment(), align_size_down_(MinPermHeapExpansion, min_alignment()));
38 MaxPermHeapExpansion = MAX2(min_alignment(), align_size_down_(MaxPermHeapExpansion, min_alignment()));
40 MinHeapDeltaBytes = align_size_up(MinHeapDeltaBytes, min_alignment());
42 SharedReadOnlySize = align_size_up(SharedReadOnlySize, max_alignment());
43 SharedReadWriteSize = align_size_up(SharedReadWriteSize, max_alignment());
44 SharedMiscDataSize = align_size_up(SharedMiscDataSize, max_alignment());
46 assert(PermSize % min_alignment() == 0, "permanent space alignment");
47 assert(MaxPermSize % max_alignment() == 0, "maximum permanent space alignment");
48 assert(SharedReadOnlySize % max_alignment() == 0, "read-only space alignment");
49 assert(SharedReadWriteSize % max_alignment() == 0, "read-write space alignment");
50 assert(SharedMiscDataSize % max_alignment() == 0, "misc-data space alignment");
51 if (PermSize < M) {
52 vm_exit_during_initialization("Too small initial permanent heap");
53 }
54 }
56 void CollectorPolicy::initialize_size_info() {
57 // User inputs from -mx and ms are aligned
58 set_initial_heap_byte_size(Arguments::initial_heap_size());
59 if (initial_heap_byte_size() == 0) {
60 set_initial_heap_byte_size(NewSize + OldSize);
61 }
62 set_initial_heap_byte_size(align_size_up(_initial_heap_byte_size,
63 min_alignment()));
65 set_min_heap_byte_size(Arguments::min_heap_size());
66 if (min_heap_byte_size() == 0) {
67 set_min_heap_byte_size(NewSize + OldSize);
68 }
69 set_min_heap_byte_size(align_size_up(_min_heap_byte_size,
70 min_alignment()));
72 set_max_heap_byte_size(align_size_up(MaxHeapSize, max_alignment()));
74 // Check heap parameter properties
75 if (initial_heap_byte_size() < M) {
76 vm_exit_during_initialization("Too small initial heap");
77 }
78 // Check heap parameter properties
79 if (min_heap_byte_size() < M) {
80 vm_exit_during_initialization("Too small minimum heap");
81 }
82 if (initial_heap_byte_size() <= NewSize) {
83 // make sure there is at least some room in old space
84 vm_exit_during_initialization("Too small initial heap for new size specified");
85 }
86 if (max_heap_byte_size() < min_heap_byte_size()) {
87 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified");
88 }
89 if (initial_heap_byte_size() < min_heap_byte_size()) {
90 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified");
91 }
92 if (max_heap_byte_size() < initial_heap_byte_size()) {
93 vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
94 }
96 if (PrintGCDetails && Verbose) {
97 gclog_or_tty->print_cr("Minimum heap " SIZE_FORMAT " Initial heap "
98 SIZE_FORMAT " Maximum heap " SIZE_FORMAT,
99 min_heap_byte_size(), initial_heap_byte_size(), max_heap_byte_size());
100 }
101 }
103 void CollectorPolicy::initialize_perm_generation(PermGen::Name pgnm) {
104 _permanent_generation =
105 new PermanentGenerationSpec(pgnm, PermSize, MaxPermSize,
106 SharedReadOnlySize,
107 SharedReadWriteSize,
108 SharedMiscDataSize,
109 SharedMiscCodeSize);
110 if (_permanent_generation == NULL) {
111 vm_exit_during_initialization("Unable to allocate gen spec");
112 }
113 }
116 GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap,
117 int max_covered_regions) {
118 switch (rem_set_name()) {
119 case GenRemSet::CardTable: {
120 CardTableRS* res = new CardTableRS(whole_heap, max_covered_regions);
121 return res;
122 }
123 default:
124 guarantee(false, "unrecognized GenRemSet::Name");
125 return NULL;
126 }
127 }
129 // GenCollectorPolicy methods.
131 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {
132 size_t x = base_size / (NewRatio+1);
133 size_t new_gen_size = x > min_alignment() ?
134 align_size_down(x, min_alignment()) :
135 min_alignment();
136 return new_gen_size;
137 }
139 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,
140 size_t maximum_size) {
141 size_t alignment = min_alignment();
142 size_t max_minus = maximum_size - alignment;
143 return desired_size < max_minus ? desired_size : max_minus;
144 }
147 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size,
148 size_t init_promo_size,
149 size_t init_survivor_size) {
150 const double max_gc_minor_pause_sec = ((double) MaxGCMinorPauseMillis)/1000.0;
151 _size_policy = new AdaptiveSizePolicy(init_eden_size,
152 init_promo_size,
153 init_survivor_size,
154 max_gc_minor_pause_sec,
155 GCTimeRatio);
156 }
158 size_t GenCollectorPolicy::compute_max_alignment() {
159 // The card marking array and the offset arrays for old generations are
160 // committed in os pages as well. Make sure they are entirely full (to
161 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
162 // byte entry and the os page size is 4096, the maximum heap size should
163 // be 512*4096 = 2MB aligned.
164 size_t alignment = GenRemSet::max_alignment_constraint(rem_set_name());
166 // Parallel GC does its own alignment of the generations to avoid requiring a
167 // large page (256M on some platforms) for the permanent generation. The
168 // other collectors should also be updated to do their own alignment and then
169 // this use of lcm() should be removed.
170 if (UseLargePages && !UseParallelGC) {
171 // in presence of large pages we have to make sure that our
172 // alignment is large page aware
173 alignment = lcm(os::large_page_size(), alignment);
174 }
176 return alignment;
177 }
179 void GenCollectorPolicy::initialize_flags() {
180 // All sizes must be multiples of the generation granularity.
181 set_min_alignment((uintx) Generation::GenGrain);
182 set_max_alignment(compute_max_alignment());
183 assert(max_alignment() >= min_alignment() &&
184 max_alignment() % min_alignment() == 0,
185 "invalid alignment constraints");
187 CollectorPolicy::initialize_flags();
189 // All generational heaps have a youngest gen; handle those flags here.
191 // Adjust max size parameters
192 if (NewSize > MaxNewSize) {
193 MaxNewSize = NewSize;
194 }
195 NewSize = align_size_down(NewSize, min_alignment());
196 MaxNewSize = align_size_down(MaxNewSize, min_alignment());
198 // Check validity of heap flags
199 assert(NewSize % min_alignment() == 0, "eden space alignment");
200 assert(MaxNewSize % min_alignment() == 0, "survivor space alignment");
202 if (NewSize < 3*min_alignment()) {
203 // make sure there room for eden and two survivor spaces
204 vm_exit_during_initialization("Too small new size specified");
205 }
206 if (SurvivorRatio < 1 || NewRatio < 1) {
207 vm_exit_during_initialization("Invalid heap ratio specified");
208 }
209 }
211 void TwoGenerationCollectorPolicy::initialize_flags() {
212 GenCollectorPolicy::initialize_flags();
214 OldSize = align_size_down(OldSize, min_alignment());
215 if (NewSize + OldSize > MaxHeapSize) {
216 MaxHeapSize = NewSize + OldSize;
217 }
218 MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
220 always_do_update_barrier = UseConcMarkSweepGC;
221 BlockOffsetArrayUseUnallocatedBlock =
222 BlockOffsetArrayUseUnallocatedBlock || ParallelGCThreads > 0;
224 // Check validity of heap flags
225 assert(OldSize % min_alignment() == 0, "old space alignment");
226 assert(MaxHeapSize % max_alignment() == 0, "maximum heap alignment");
227 }
229 // Values set on the command line win over any ergonomically
230 // set command line parameters.
231 // Ergonomic choice of parameters are done before this
232 // method is called. Values for command line parameters such as NewSize
233 // and MaxNewSize feed those ergonomic choices into this method.
234 // This method makes the final generation sizings consistent with
235 // themselves and with overall heap sizings.
236 // In the absence of explicitly set command line flags, policies
237 // such as the use of NewRatio are used to size the generation.
238 void GenCollectorPolicy::initialize_size_info() {
239 CollectorPolicy::initialize_size_info();
241 // min_alignment() is used for alignment within a generation.
242 // There is additional alignment done down stream for some
243 // collectors that sometimes causes unwanted rounding up of
244 // generations sizes.
246 // Determine maximum size of gen0
248 size_t max_new_size = 0;
249 if (FLAG_IS_CMDLINE(MaxNewSize)) {
250 if (MaxNewSize < min_alignment()) {
251 max_new_size = min_alignment();
252 } else if (MaxNewSize >= max_heap_byte_size()) {
253 max_new_size = align_size_down(max_heap_byte_size() - min_alignment(),
254 min_alignment());
255 warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or "
256 "greater than the entire heap (" SIZE_FORMAT "k). A "
257 "new generation size of " SIZE_FORMAT "k will be used.",
258 MaxNewSize/K, max_heap_byte_size()/K, max_new_size/K);
259 } else {
260 max_new_size = align_size_down(MaxNewSize, min_alignment());
261 }
263 // The case for FLAG_IS_ERGO(MaxNewSize) could be treated
264 // specially at this point to just use an ergonomically set
265 // MaxNewSize to set max_new_size. For cases with small
266 // heaps such a policy often did not work because the MaxNewSize
267 // was larger than the entire heap. The interpretation given
268 // to ergonomically set flags is that the flags are set
269 // by different collectors for their own special needs but
270 // are not allowed to badly shape the heap. This allows the
271 // different collectors to decide what's best for themselves
272 // without having to factor in the overall heap shape. It
273 // can be the case in the future that the collectors would
274 // only make "wise" ergonomics choices and this policy could
275 // just accept those choices. The choices currently made are
276 // not always "wise".
277 } else {
278 max_new_size = scale_by_NewRatio_aligned(max_heap_byte_size());
279 // Bound the maximum size by NewSize below (since it historically
280 // would have been NewSize and because the NewRatio calculation could
281 // yield a size that is too small) and bound it by MaxNewSize above.
282 // Ergonomics plays here by previously calculating the desired
283 // NewSize and MaxNewSize.
284 max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize);
285 }
286 assert(max_new_size > 0, "All paths should set max_new_size");
288 // Given the maximum gen0 size, determine the initial and
289 // minimum sizes.
291 if (max_heap_byte_size() == min_heap_byte_size()) {
292 // The maximum and minimum heap sizes are the same so
293 // the generations minimum and initial must be the
294 // same as its maximum.
295 set_min_gen0_size(max_new_size);
296 set_initial_gen0_size(max_new_size);
297 set_max_gen0_size(max_new_size);
298 } else {
299 size_t desired_new_size = 0;
300 if (!FLAG_IS_DEFAULT(NewSize)) {
301 // If NewSize is set ergonomically (for example by cms), it
302 // would make sense to use it. If it is used, also use it
303 // to set the initial size. Although there is no reason
304 // the minimum size and the initial size have to be the same,
305 // the current implementation gets into trouble during the calculation
306 // of the tenured generation sizes if they are different.
307 // Note that this makes the initial size and the minimum size
308 // generally small compared to the NewRatio calculation.
309 _min_gen0_size = NewSize;
310 desired_new_size = NewSize;
311 max_new_size = MAX2(max_new_size, NewSize);
312 } else {
313 // For the case where NewSize is the default, use NewRatio
314 // to size the minimum and initial generation sizes.
315 // Use the default NewSize as the floor for these values. If
316 // NewRatio is overly large, the resulting sizes can be too
317 // small.
318 _min_gen0_size = MAX2(scale_by_NewRatio_aligned(min_heap_byte_size()),
319 NewSize);
320 desired_new_size =
321 MAX2(scale_by_NewRatio_aligned(initial_heap_byte_size()),
322 NewSize);
323 }
325 assert(_min_gen0_size > 0, "Sanity check");
326 set_initial_gen0_size(desired_new_size);
327 set_max_gen0_size(max_new_size);
329 // At this point the desirable initial and minimum sizes have been
330 // determined without regard to the maximum sizes.
332 // Bound the sizes by the corresponding overall heap sizes.
333 set_min_gen0_size(
334 bound_minus_alignment(_min_gen0_size, min_heap_byte_size()));
335 set_initial_gen0_size(
336 bound_minus_alignment(_initial_gen0_size, initial_heap_byte_size()));
337 set_max_gen0_size(
338 bound_minus_alignment(_max_gen0_size, max_heap_byte_size()));
340 // At this point all three sizes have been checked against the
341 // maximum sizes but have not been checked for consistency
342 // among the three.
344 // Final check min <= initial <= max
345 set_min_gen0_size(MIN2(_min_gen0_size, _max_gen0_size));
346 set_initial_gen0_size(
347 MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size));
348 set_min_gen0_size(MIN2(_min_gen0_size, _initial_gen0_size));
349 }
351 if (PrintGCDetails && Verbose) {
352 gclog_or_tty->print_cr("Minimum gen0 " SIZE_FORMAT " Initial gen0 "
353 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
354 min_gen0_size(), initial_gen0_size(), max_gen0_size());
355 }
356 }
358 // Call this method during the sizing of the gen1 to make
359 // adjustments to gen0 because of gen1 sizing policy. gen0 initially has
360 // the most freedom in sizing because it is done before the
361 // policy for gen1 is applied. Once gen1 policies have been applied,
362 // there may be conflicts in the shape of the heap and this method
363 // is used to make the needed adjustments. The application of the
364 // policies could be more sophisticated (iterative for example) but
365 // keeping it simple also seems a worthwhile goal.
366 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr,
367 size_t* gen1_size_ptr,
368 size_t heap_size,
369 size_t min_gen0_size) {
370 bool result = false;
371 if ((*gen1_size_ptr + *gen0_size_ptr) > heap_size) {
372 if (((*gen0_size_ptr + OldSize) > heap_size) &&
373 (heap_size - min_gen0_size) >= min_alignment()) {
374 // Adjust gen0 down to accomodate OldSize
375 *gen0_size_ptr = heap_size - min_gen0_size;
376 *gen0_size_ptr =
377 MAX2((uintx)align_size_down(*gen0_size_ptr, min_alignment()),
378 min_alignment());
379 assert(*gen0_size_ptr > 0, "Min gen0 is too large");
380 result = true;
381 } else {
382 *gen1_size_ptr = heap_size - *gen0_size_ptr;
383 *gen1_size_ptr =
384 MAX2((uintx)align_size_down(*gen1_size_ptr, min_alignment()),
385 min_alignment());
386 }
387 }
388 return result;
389 }
391 // Minimum sizes of the generations may be different than
392 // the initial sizes. An inconsistently is permitted here
393 // in the total size that can be specified explicitly by
394 // command line specification of OldSize and NewSize and
395 // also a command line specification of -Xms. Issue a warning
396 // but allow the values to pass.
398 void TwoGenerationCollectorPolicy::initialize_size_info() {
399 GenCollectorPolicy::initialize_size_info();
401 // At this point the minimum, initial and maximum sizes
402 // of the overall heap and of gen0 have been determined.
403 // The maximum gen1 size can be determined from the maximum gen0
404 // and maximum heap size since not explicit flags exits
405 // for setting the gen1 maximum.
406 _max_gen1_size = max_heap_byte_size() - _max_gen0_size;
407 _max_gen1_size =
408 MAX2((uintx)align_size_down(_max_gen1_size, min_alignment()),
409 min_alignment());
410 // If no explicit command line flag has been set for the
411 // gen1 size, use what is left for gen1.
412 if (FLAG_IS_DEFAULT(OldSize) || FLAG_IS_ERGO(OldSize)) {
413 // The user has not specified any value or ergonomics
414 // has chosen a value (which may or may not be consistent
415 // with the overall heap size). In either case make
416 // the minimum, maximum and initial sizes consistent
417 // with the gen0 sizes and the overall heap sizes.
418 assert(min_heap_byte_size() > _min_gen0_size,
419 "gen0 has an unexpected minimum size");
420 set_min_gen1_size(min_heap_byte_size() - min_gen0_size());
421 set_min_gen1_size(
422 MAX2((uintx)align_size_down(_min_gen1_size, min_alignment()),
423 min_alignment()));
424 set_initial_gen1_size(initial_heap_byte_size() - initial_gen0_size());
425 set_initial_gen1_size(
426 MAX2((uintx)align_size_down(_initial_gen1_size, min_alignment()),
427 min_alignment()));
429 } else {
430 // It's been explicitly set on the command line. Use the
431 // OldSize and then determine the consequences.
432 set_min_gen1_size(OldSize);
433 set_initial_gen1_size(OldSize);
435 // If the user has explicitly set an OldSize that is inconsistent
436 // with other command line flags, issue a warning.
437 // The generation minimums and the overall heap mimimum should
438 // be within one heap alignment.
439 if ((_min_gen1_size + _min_gen0_size + min_alignment()) <
440 min_heap_byte_size()) {
441 warning("Inconsistency between minimum heap size and minimum "
442 "generation sizes: using minimum heap = " SIZE_FORMAT,
443 min_heap_byte_size());
444 }
445 if ((OldSize > _max_gen1_size)) {
446 warning("Inconsistency between maximum heap size and maximum "
447 "generation sizes: using maximum heap = " SIZE_FORMAT
448 " -XX:OldSize flag is being ignored",
449 max_heap_byte_size());
450 }
451 // If there is an inconsistency between the OldSize and the minimum and/or
452 // initial size of gen0, since OldSize was explicitly set, OldSize wins.
453 if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size,
454 min_heap_byte_size(), OldSize)) {
455 if (PrintGCDetails && Verbose) {
456 gclog_or_tty->print_cr("Minimum gen0 " SIZE_FORMAT " Initial gen0 "
457 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
458 min_gen0_size(), initial_gen0_size(), max_gen0_size());
459 }
460 }
461 // Initial size
462 if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,
463 initial_heap_byte_size(), OldSize)) {
464 if (PrintGCDetails && Verbose) {
465 gclog_or_tty->print_cr("Minimum gen0 " SIZE_FORMAT " Initial gen0 "
466 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
467 min_gen0_size(), initial_gen0_size(), max_gen0_size());
468 }
469 }
470 }
471 // Enforce the maximum gen1 size.
472 set_min_gen1_size(MIN2(_min_gen1_size, _max_gen1_size));
474 // Check that min gen1 <= initial gen1 <= max gen1
475 set_initial_gen1_size(MAX2(_initial_gen1_size, _min_gen1_size));
476 set_initial_gen1_size(MIN2(_initial_gen1_size, _max_gen1_size));
478 if (PrintGCDetails && Verbose) {
479 gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 "
480 SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT,
481 min_gen1_size(), initial_gen1_size(), max_gen1_size());
482 }
483 }
485 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
486 bool is_tlab,
487 bool* gc_overhead_limit_was_exceeded) {
488 GenCollectedHeap *gch = GenCollectedHeap::heap();
490 debug_only(gch->check_for_valid_allocation_state());
491 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
492 HeapWord* result = NULL;
494 // Loop until the allocation is satisified,
495 // or unsatisfied after GC.
496 for (int try_count = 1; /* return or throw */; try_count += 1) {
497 HandleMark hm; // discard any handles allocated in each iteration
499 // First allocation attempt is lock-free.
500 Generation *gen0 = gch->get_gen(0);
501 assert(gen0->supports_inline_contig_alloc(),
502 "Otherwise, must do alloc within heap lock");
503 if (gen0->should_allocate(size, is_tlab)) {
504 result = gen0->par_allocate(size, is_tlab);
505 if (result != NULL) {
506 assert(gch->is_in_reserved(result), "result not in heap");
507 return result;
508 }
509 }
510 unsigned int gc_count_before; // read inside the Heap_lock locked region
511 {
512 MutexLocker ml(Heap_lock);
513 if (PrintGC && Verbose) {
514 gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:"
515 " attempting locked slow path allocation");
516 }
517 // Note that only large objects get a shot at being
518 // allocated in later generations.
519 bool first_only = ! should_try_older_generation_allocation(size);
521 result = gch->attempt_allocation(size, is_tlab, first_only);
522 if (result != NULL) {
523 assert(gch->is_in_reserved(result), "result not in heap");
524 return result;
525 }
527 // There are NULL's returned for different circumstances below.
528 // In general gc_overhead_limit_was_exceeded should be false so
529 // set it so here and reset it to true only if the gc time
530 // limit is being exceeded as checked below.
531 *gc_overhead_limit_was_exceeded = false;
533 if (GC_locker::is_active_and_needs_gc()) {
534 if (is_tlab) {
535 return NULL; // Caller will retry allocating individual object
536 }
537 if (!gch->is_maximal_no_gc()) {
538 // Try and expand heap to satisfy request
539 result = expand_heap_and_allocate(size, is_tlab);
540 // result could be null if we are out of space
541 if (result != NULL) {
542 return result;
543 }
544 }
546 // If this thread is not in a jni critical section, we stall
547 // the requestor until the critical section has cleared and
548 // GC allowed. When the critical section clears, a GC is
549 // initiated by the last thread exiting the critical section; so
550 // we retry the allocation sequence from the beginning of the loop,
551 // rather than causing more, now probably unnecessary, GC attempts.
552 JavaThread* jthr = JavaThread::current();
553 if (!jthr->in_critical()) {
554 MutexUnlocker mul(Heap_lock);
555 // Wait for JNI critical section to be exited
556 GC_locker::stall_until_clear();
557 continue;
558 } else {
559 if (CheckJNICalls) {
560 fatal("Possible deadlock due to allocating while"
561 " in jni critical section");
562 }
563 return NULL;
564 }
565 }
567 // Read the gc count while the heap lock is held.
568 gc_count_before = Universe::heap()->total_collections();
569 }
571 // Allocation has failed and a collection is about
572 // to be done. If the gc time limit was exceeded the
573 // last time a collection was done, return NULL so
574 // that an out-of-memory will be thrown. Clear
575 // gc_time_limit_exceeded so that subsequent attempts
576 // at a collection will be made.
577 if (size_policy()->gc_time_limit_exceeded()) {
578 *gc_overhead_limit_was_exceeded = true;
579 size_policy()->set_gc_time_limit_exceeded(false);
580 return NULL;
581 }
583 VM_GenCollectForAllocation op(size,
584 is_tlab,
585 gc_count_before);
586 VMThread::execute(&op);
587 if (op.prologue_succeeded()) {
588 result = op.result();
589 if (op.gc_locked()) {
590 assert(result == NULL, "must be NULL if gc_locked() is true");
591 continue; // retry and/or stall as necessary
592 }
593 assert(result == NULL || gch->is_in_reserved(result),
594 "result not in heap");
595 return result;
596 }
598 // Give a warning if we seem to be looping forever.
599 if ((QueuedAllocationWarningCount > 0) &&
600 (try_count % QueuedAllocationWarningCount == 0)) {
601 warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t"
602 " size=%d %s", try_count, size, is_tlab ? "(TLAB)" : "");
603 }
604 }
605 }
607 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size,
608 bool is_tlab) {
609 GenCollectedHeap *gch = GenCollectedHeap::heap();
610 HeapWord* result = NULL;
611 for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) {
612 Generation *gen = gch->get_gen(i);
613 if (gen->should_allocate(size, is_tlab)) {
614 result = gen->expand_and_allocate(size, is_tlab);
615 }
616 }
617 assert(result == NULL || gch->is_in_reserved(result), "result not in heap");
618 return result;
619 }
621 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size,
622 bool is_tlab) {
623 GenCollectedHeap *gch = GenCollectedHeap::heap();
624 GCCauseSetter x(gch, GCCause::_allocation_failure);
625 HeapWord* result = NULL;
627 assert(size != 0, "Precondition violated");
628 if (GC_locker::is_active_and_needs_gc()) {
629 // GC locker is active; instead of a collection we will attempt
630 // to expand the heap, if there's room for expansion.
631 if (!gch->is_maximal_no_gc()) {
632 result = expand_heap_and_allocate(size, is_tlab);
633 }
634 return result; // could be null if we are out of space
635 } else if (!gch->incremental_collection_will_fail()) {
636 // The gc_prologues have not executed yet. The value
637 // for incremental_collection_will_fail() is the remanent
638 // of the last collection.
639 // Do an incremental collection.
640 gch->do_collection(false /* full */,
641 false /* clear_all_soft_refs */,
642 size /* size */,
643 is_tlab /* is_tlab */,
644 number_of_generations() - 1 /* max_level */);
645 } else {
646 // Try a full collection; see delta for bug id 6266275
647 // for the original code and why this has been simplified
648 // with from-space allocation criteria modified and
649 // such allocation moved out of the safepoint path.
650 gch->do_collection(true /* full */,
651 false /* clear_all_soft_refs */,
652 size /* size */,
653 is_tlab /* is_tlab */,
654 number_of_generations() - 1 /* max_level */);
655 }
657 result = gch->attempt_allocation(size, is_tlab, false /*first_only*/);
659 if (result != NULL) {
660 assert(gch->is_in_reserved(result), "result not in heap");
661 return result;
662 }
664 // OK, collection failed, try expansion.
665 result = expand_heap_and_allocate(size, is_tlab);
666 if (result != NULL) {
667 return result;
668 }
670 // If we reach this point, we're really out of memory. Try every trick
671 // we can to reclaim memory. Force collection of soft references. Force
672 // a complete compaction of the heap. Any additional methods for finding
673 // free memory should be here, especially if they are expensive. If this
674 // attempt fails, an OOM exception will be thrown.
675 {
676 IntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
678 gch->do_collection(true /* full */,
679 true /* clear_all_soft_refs */,
680 size /* size */,
681 is_tlab /* is_tlab */,
682 number_of_generations() - 1 /* max_level */);
683 }
685 result = gch->attempt_allocation(size, is_tlab, false /* first_only */);
686 if (result != NULL) {
687 assert(gch->is_in_reserved(result), "result not in heap");
688 return result;
689 }
691 // What else? We might try synchronous finalization later. If the total
692 // space available is large enough for the allocation, then a more
693 // complete compaction phase than we've tried so far might be
694 // appropriate.
695 return NULL;
696 }
698 size_t GenCollectorPolicy::large_typearray_limit() {
699 return FastAllocateSizeLimit;
700 }
702 // Return true if any of the following is true:
703 // . the allocation won't fit into the current young gen heap
704 // . gc locker is occupied (jni critical section)
705 // . heap memory is tight -- the most recent previous collection
706 // was a full collection because a partial collection (would
707 // have) failed and is likely to fail again
708 bool GenCollectorPolicy::should_try_older_generation_allocation(
709 size_t word_size) const {
710 GenCollectedHeap* gch = GenCollectedHeap::heap();
711 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();
712 return (word_size > heap_word_size(gen0_capacity))
713 || (GC_locker::is_active_and_needs_gc())
714 || ( gch->last_incremental_collection_failed()
715 && gch->incremental_collection_will_fail());
716 }
719 //
720 // MarkSweepPolicy methods
721 //
723 MarkSweepPolicy::MarkSweepPolicy() {
724 initialize_all();
725 }
727 void MarkSweepPolicy::initialize_generations() {
728 initialize_perm_generation(PermGen::MarkSweepCompact);
729 _generations = new GenerationSpecPtr[number_of_generations()];
730 if (_generations == NULL)
731 vm_exit_during_initialization("Unable to allocate gen spec");
733 if (UseParNewGC && ParallelGCThreads > 0) {
734 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);
735 } else {
736 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);
737 }
738 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);
740 if (_generations[0] == NULL || _generations[1] == NULL)
741 vm_exit_during_initialization("Unable to allocate gen spec");
742 }
744 void MarkSweepPolicy::initialize_gc_policy_counters() {
745 // initialize the policy counters - 2 collectors, 3 generations
746 if (UseParNewGC && ParallelGCThreads > 0) {
747 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);
748 }
749 else {
750 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
751 }
752 }