1 /*
2 * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "gc_implementation/shared/adaptiveSizePolicy.hpp"
27 #include "gc_implementation/shared/gcPolicyCounters.hpp"
28 #include "gc_implementation/shared/vmGCOperations.hpp"
29 #include "memory/cardTableRS.hpp"
30 #include "memory/collectorPolicy.hpp"
31 #include "memory/gcLocker.inline.hpp"
32 #include "memory/genCollectedHeap.hpp"
33 #include "memory/generationSpec.hpp"
34 #include "memory/space.hpp"
35 #include "memory/universe.hpp"
36 #include "runtime/arguments.hpp"
37 #include "runtime/globals_extension.hpp"
38 #include "runtime/handles.inline.hpp"
39 #include "runtime/java.hpp"
40 #include "runtime/thread.inline.hpp"
41 #include "runtime/vmThread.hpp"
42 #include "utilities/macros.hpp"
43 #if INCLUDE_ALL_GCS
44 #include "gc_implementation/concurrentMarkSweep/cmsAdaptiveSizePolicy.hpp"
45 #include "gc_implementation/concurrentMarkSweep/cmsGCAdaptivePolicyCounters.hpp"
46 #endif // INCLUDE_ALL_GCS
47
48 // CollectorPolicy methods.
49
50 void CollectorPolicy::initialize_flags() {
51 assert(_max_alignment >= _min_alignment,
52 err_msg("max_alignment: " SIZE_FORMAT " less than min_alignment: " SIZE_FORMAT,
53 _max_alignment, _min_alignment));
54 assert(_max_alignment % _min_alignment == 0,
55 err_msg("max_alignment: " SIZE_FORMAT " not aligned by min_alignment: " SIZE_FORMAT,
56 _max_alignment, _min_alignment));
57
58 if (MaxHeapSize < InitialHeapSize) {
59 vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
60 }
61
62 MinHeapDeltaBytes = align_size_up(MinHeapDeltaBytes, _min_alignment);
63 }
64
65 void CollectorPolicy::initialize_size_info() {
66 // User inputs from -mx and ms must be aligned
67 _min_heap_byte_size = align_size_up(Arguments::min_heap_size(), _min_alignment);
68 _initial_heap_byte_size = align_size_up(InitialHeapSize, _min_alignment);
69 _max_heap_byte_size = align_size_up(MaxHeapSize, _max_alignment);
70
71 // Check heap parameter properties
72 if (_initial_heap_byte_size < M) {
73 vm_exit_during_initialization("Too small initial heap");
74 }
75 // Check heap parameter properties
76 if (_min_heap_byte_size < M) {
77 vm_exit_during_initialization("Too small minimum heap");
78 }
79 if (_initial_heap_byte_size <= NewSize) {
80 // make sure there is at least some room in old space
81 vm_exit_during_initialization("Too small initial heap for new size specified");
82 }
83 if (_max_heap_byte_size < _min_heap_byte_size) {
84 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified");
85 }
86 if (_initial_heap_byte_size < _min_heap_byte_size) {
87 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified");
88 }
89 if (_max_heap_byte_size < _initial_heap_byte_size) {
90 vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
91 }
92
93 if (PrintGCDetails && Verbose) {
94 gclog_or_tty->print_cr("Minimum heap " SIZE_FORMAT " Initial heap "
95 SIZE_FORMAT " Maximum heap " SIZE_FORMAT,
96 _min_heap_byte_size, _initial_heap_byte_size, _max_heap_byte_size);
97 }
98 }
99
100 bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) {
101 bool result = _should_clear_all_soft_refs;
102 set_should_clear_all_soft_refs(false);
103 return result;
104 }
105
106 GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap,
107 int max_covered_regions) {
108 return new CardTableRS(whole_heap, max_covered_regions);
109 }
110
111 void CollectorPolicy::cleared_all_soft_refs() {
112 // If near gc overhear limit, continue to clear SoftRefs. SoftRefs may
113 // have been cleared in the last collection but if the gc overhear
114 // limit continues to be near, SoftRefs should still be cleared.
115 if (size_policy() != NULL) {
116 _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near();
117 }
118 _all_soft_refs_clear = true;
119 }
120
121 size_t CollectorPolicy::compute_max_alignment() {
122 // The card marking array and the offset arrays for old generations are
123 // committed in os pages as well. Make sure they are entirely full (to
124 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
125 // byte entry and the os page size is 4096, the maximum heap size should
126 // be 512*4096 = 2MB aligned.
127
128 // There is only the GenRemSet in Hotspot and only the GenRemSet::CardTable
129 // is supported.
130 // Requirements of any new remembered set implementations must be added here.
131 size_t alignment = GenRemSet::max_alignment_constraint(GenRemSet::CardTable);
132
133 // Parallel GC does its own alignment of the generations to avoid requiring a
134 // large page (256M on some platforms) for the permanent generation. The
135 // other collectors should also be updated to do their own alignment and then
136 // this use of lcm() should be removed.
137 if (UseLargePages && !UseParallelGC) {
138 // in presence of large pages we have to make sure that our
139 // alignment is large page aware
140 alignment = lcm(os::large_page_size(), alignment);
141 }
142
143 return alignment;
144 }
145
146 // GenCollectorPolicy methods.
147
148 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {
149 return align_size_down_bounded(base_size / (NewRatio + 1), _min_alignment);
150 }
151
152 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,
153 size_t maximum_size) {
154 size_t alignment = _min_alignment;
155 size_t max_minus = maximum_size - alignment;
156 return desired_size < max_minus ? desired_size : max_minus;
157 }
158
159
160 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size,
161 size_t init_promo_size,
162 size_t init_survivor_size) {
163 const double max_gc_pause_sec = ((double) MaxGCPauseMillis) / 1000.0;
164 _size_policy = new AdaptiveSizePolicy(init_eden_size,
165 init_promo_size,
166 init_survivor_size,
167 max_gc_pause_sec,
168 GCTimeRatio);
169 }
170
171 void GenCollectorPolicy::initialize_flags() {
172 // All sizes must be multiples of the generation granularity.
173 _min_alignment = (uintx) Generation::GenGrain;
174 _max_alignment = compute_max_alignment();
175
176 CollectorPolicy::initialize_flags();
177
178 // All generational heaps have a youngest gen; handle those flags here.
179
180 // Adjust max size parameters
181 if (NewSize > MaxNewSize) {
182 MaxNewSize = NewSize;
183 }
184 NewSize = align_size_down(NewSize, _min_alignment);
185 MaxNewSize = align_size_down(MaxNewSize, _min_alignment);
186
187 // Check validity of heap flags
188 assert(NewSize % _min_alignment == 0, "eden space alignment");
189 assert(MaxNewSize % _min_alignment == 0, "survivor space alignment");
190
191 if (NewSize < 3 * _min_alignment) {
192 // make sure there room for eden and two survivor spaces
193 vm_exit_during_initialization("Too small new size specified");
194 }
195
196 if (SurvivorRatio < 1 || NewRatio < 1) {
197 vm_exit_during_initialization("Invalid young gen ratio specified");
198 }
199 }
200
201 void TwoGenerationCollectorPolicy::initialize_flags() {
202 GenCollectorPolicy::initialize_flags();
203
204 OldSize = align_size_down(OldSize, _min_alignment);
205
206 if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(NewSize)) {
207 // NewRatio will be used later to set the young generation size so we use
208 // it to calculate how big the heap should be based on the requested OldSize
209 // and NewRatio.
210 assert(NewRatio > 0, "NewRatio should have been set up earlier");
211 size_t calculated_heapsize = (OldSize / NewRatio) * (NewRatio + 1);
212
213 calculated_heapsize = align_size_up(calculated_heapsize, _max_alignment);
214 MaxHeapSize = calculated_heapsize;
215 InitialHeapSize = calculated_heapsize;
216 }
217 MaxHeapSize = align_size_up(MaxHeapSize, _max_alignment);
218
219 // adjust max heap size if necessary
220 if (NewSize + OldSize > MaxHeapSize) {
221 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
222 // somebody set a maximum heap size with the intention that we should not
223 // exceed it. Adjust New/OldSize as necessary.
224 uintx calculated_size = NewSize + OldSize;
225 double shrink_factor = (double) MaxHeapSize / calculated_size;
226 // align
227 NewSize = align_size_down((uintx) (NewSize * shrink_factor), _min_alignment);
228 // OldSize is already aligned because above we aligned MaxHeapSize to
229 // _max_alignment, and we just made sure that NewSize is aligned to
230 // _min_alignment. In initialize_flags() we verified that _max_alignment
231 // is a multiple of _min_alignment.
232 OldSize = MaxHeapSize - NewSize;
233 } else {
234 MaxHeapSize = NewSize + OldSize;
235 }
236 }
237 // need to do this again
238 MaxHeapSize = align_size_up(MaxHeapSize, _max_alignment);
239
240 // adjust max heap size if necessary
241 if (NewSize + OldSize > MaxHeapSize) {
242 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
243 // somebody set a maximum heap size with the intention that we should not
244 // exceed it. Adjust New/OldSize as necessary.
245 uintx calculated_size = NewSize + OldSize;
246 double shrink_factor = (double) MaxHeapSize / calculated_size;
247 // align
248 NewSize = align_size_down((uintx) (NewSize * shrink_factor), _min_alignment);
249 // OldSize is already aligned because above we aligned MaxHeapSize to
250 // _max_alignment, and we just made sure that NewSize is aligned to
251 // _min_alignment. In initialize_flags() we verified that _max_alignment
252 // is a multiple of _min_alignment.
253 OldSize = MaxHeapSize - NewSize;
254 } else {
255 MaxHeapSize = NewSize + OldSize;
256 }
257 }
258 // need to do this again
259 MaxHeapSize = align_size_up(MaxHeapSize, _max_alignment);
260
261 always_do_update_barrier = UseConcMarkSweepGC;
262
263 // Check validity of heap flags
264 assert(OldSize % _min_alignment == 0, "old space alignment");
265 assert(MaxHeapSize % _max_alignment == 0, "maximum heap alignment");
266 }
267
268 // Values set on the command line win over any ergonomically
269 // set command line parameters.
270 // Ergonomic choice of parameters are done before this
271 // method is called. Values for command line parameters such as NewSize
272 // and MaxNewSize feed those ergonomic choices into this method.
273 // This method makes the final generation sizings consistent with
274 // themselves and with overall heap sizings.
275 // In the absence of explicitly set command line flags, policies
276 // such as the use of NewRatio are used to size the generation.
277 void GenCollectorPolicy::initialize_size_info() {
278 CollectorPolicy::initialize_size_info();
279
280 // _min_alignment is used for alignment within a generation.
281 // There is additional alignment done down stream for some
282 // collectors that sometimes causes unwanted rounding up of
283 // generations sizes.
284
285 // Determine maximum size of gen0
286
287 size_t max_new_size = 0;
288 if (FLAG_IS_CMDLINE(MaxNewSize) || FLAG_IS_ERGO(MaxNewSize)) {
289 if (MaxNewSize < _min_alignment) {
290 max_new_size = _min_alignment;
291 }
292 if (MaxNewSize >= _max_heap_byte_size) {
293 max_new_size = align_size_down(_max_heap_byte_size - _min_alignment,
294 _min_alignment);
295 warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or "
296 "greater than the entire heap (" SIZE_FORMAT "k). A "
297 "new generation size of " SIZE_FORMAT "k will be used.",
298 MaxNewSize/K, _max_heap_byte_size/K, max_new_size/K);
299 } else {
300 max_new_size = align_size_down(MaxNewSize, _min_alignment);
301 }
302
303 // The case for FLAG_IS_ERGO(MaxNewSize) could be treated
304 // specially at this point to just use an ergonomically set
305 // MaxNewSize to set max_new_size. For cases with small
306 // heaps such a policy often did not work because the MaxNewSize
307 // was larger than the entire heap. The interpretation given
308 // to ergonomically set flags is that the flags are set
309 // by different collectors for their own special needs but
310 // are not allowed to badly shape the heap. This allows the
311 // different collectors to decide what's best for themselves
312 // without having to factor in the overall heap shape. It
313 // can be the case in the future that the collectors would
314 // only make "wise" ergonomics choices and this policy could
315 // just accept those choices. The choices currently made are
316 // not always "wise".
317 } else {
318 max_new_size = scale_by_NewRatio_aligned(_max_heap_byte_size);
319 // Bound the maximum size by NewSize below (since it historically
320 // would have been NewSize and because the NewRatio calculation could
321 // yield a size that is too small) and bound it by MaxNewSize above.
322 // Ergonomics plays here by previously calculating the desired
323 // NewSize and MaxNewSize.
324 max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize);
325 }
326 assert(max_new_size > 0, "All paths should set max_new_size");
327
328 // Given the maximum gen0 size, determine the initial and
329 // minimum gen0 sizes.
330
331 if (_max_heap_byte_size == _min_heap_byte_size) {
332 // The maximum and minimum heap sizes are the same so
333 // the generations minimum and initial must be the
334 // same as its maximum.
335 _min_gen0_size = max_new_size;
336 _initial_gen0_size = max_new_size;
337 _max_gen0_size = max_new_size;
338 } else {
339 size_t desired_new_size = 0;
340 if (!FLAG_IS_DEFAULT(NewSize)) {
341 // If NewSize is set ergonomically (for example by cms), it
342 // would make sense to use it. If it is used, also use it
343 // to set the initial size. Although there is no reason
344 // the minimum size and the initial size have to be the same,
345 // the current implementation gets into trouble during the calculation
346 // of the tenured generation sizes if they are different.
347 // Note that this makes the initial size and the minimum size
348 // generally small compared to the NewRatio calculation.
349 _min_gen0_size = NewSize;
350 desired_new_size = NewSize;
351 max_new_size = MAX2(max_new_size, NewSize);
352 } else {
353 // For the case where NewSize is the default, use NewRatio
354 // to size the minimum and initial generation sizes.
355 // Use the default NewSize as the floor for these values. If
356 // NewRatio is overly large, the resulting sizes can be too
357 // small.
358 _min_gen0_size = MAX2(scale_by_NewRatio_aligned(_min_heap_byte_size), NewSize);
359 desired_new_size =
360 MAX2(scale_by_NewRatio_aligned(_initial_heap_byte_size), NewSize);
361 }
362
363 assert(_min_gen0_size > 0, "Sanity check");
364 _initial_gen0_size = desired_new_size;
365 _max_gen0_size = max_new_size;
366
367 // At this point the desirable initial and minimum sizes have been
368 // determined without regard to the maximum sizes.
369
370 // Bound the sizes by the corresponding overall heap sizes.
371 _min_gen0_size = bound_minus_alignment(_min_gen0_size, _min_heap_byte_size);
372 _initial_gen0_size = bound_minus_alignment(_initial_gen0_size, _initial_heap_byte_size);
373 _max_gen0_size = bound_minus_alignment(_max_gen0_size, _max_heap_byte_size);
374
375 // At this point all three sizes have been checked against the
376 // maximum sizes but have not been checked for consistency
377 // among the three.
378
379 // Final check min <= initial <= max
380 _min_gen0_size = MIN2(_min_gen0_size, _max_gen0_size);
381 _initial_gen0_size = MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size);
382 _min_gen0_size = MIN2(_min_gen0_size, _initial_gen0_size);
383 }
384
385 if (PrintGCDetails && Verbose) {
386 gclog_or_tty->print_cr("1: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
387 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
388 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
389 }
390 }
391
392 // Call this method during the sizing of the gen1 to make
393 // adjustments to gen0 because of gen1 sizing policy. gen0 initially has
394 // the most freedom in sizing because it is done before the
395 // policy for gen1 is applied. Once gen1 policies have been applied,
396 // there may be conflicts in the shape of the heap and this method
397 // is used to make the needed adjustments. The application of the
398 // policies could be more sophisticated (iterative for example) but
399 // keeping it simple also seems a worthwhile goal.
400 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr,
401 size_t* gen1_size_ptr,
402 const size_t heap_size,
403 const size_t min_gen1_size) {
404 bool result = false;
405
406 if ((*gen1_size_ptr + *gen0_size_ptr) > heap_size) {
407 if ((heap_size < (*gen0_size_ptr + min_gen1_size)) &&
408 (heap_size >= min_gen1_size + _min_alignment)) {
409 // Adjust gen0 down to accommodate min_gen1_size
410 *gen0_size_ptr = align_size_down_bounded(heap_size - min_gen1_size, _min_alignment);
411 assert(*gen0_size_ptr > 0, "Min gen0 is too large");
412 result = true;
413 } else {
414 *gen1_size_ptr = align_size_down_bounded(heap_size - *gen0_size_ptr, _min_alignment);
415 }
416 }
417 return result;
418 }
419
420 // Minimum sizes of the generations may be different than
421 // the initial sizes. An inconsistently is permitted here
422 // in the total size that can be specified explicitly by
423 // command line specification of OldSize and NewSize and
424 // also a command line specification of -Xms. Issue a warning
425 // but allow the values to pass.
426
427 void TwoGenerationCollectorPolicy::initialize_size_info() {
428 GenCollectorPolicy::initialize_size_info();
429
430 // At this point the minimum, initial and maximum sizes
431 // of the overall heap and of gen0 have been determined.
432 // The maximum gen1 size can be determined from the maximum gen0
433 // and maximum heap size since no explicit flags exits
434 // for setting the gen1 maximum.
435 _max_gen1_size = _max_heap_byte_size - _max_gen0_size;
436 _max_gen1_size =
437 MAX2((uintx)align_size_down(_max_gen1_size, _min_alignment), _min_alignment);
438 // If no explicit command line flag has been set for the
439 // gen1 size, use what is left for gen1.
440 if (FLAG_IS_DEFAULT(OldSize) || FLAG_IS_ERGO(OldSize)) {
441 // The user has not specified any value or ergonomics
442 // has chosen a value (which may or may not be consistent
443 // with the overall heap size). In either case make
444 // the minimum, maximum and initial sizes consistent
445 // with the gen0 sizes and the overall heap sizes.
446 assert(_min_heap_byte_size > _min_gen0_size,
447 "gen0 has an unexpected minimum size");
448 _min_gen1_size = _min_heap_byte_size - _min_gen0_size;
449 _min_gen1_size =
450 MAX2((uintx)align_size_down(_min_gen1_size, _min_alignment), _min_alignment);
451 _initial_gen1_size = _initial_heap_byte_size - _initial_gen0_size;
452 _initial_gen1_size =
453 MAX2((uintx)align_size_down(_initial_gen1_size, _min_alignment), _min_alignment);
454 } else {
455 // It's been explicitly set on the command line. Use the
456 // OldSize and then determine the consequences.
457 _min_gen1_size = OldSize;
458 _initial_gen1_size = OldSize;
459
460 // If the user has explicitly set an OldSize that is inconsistent
461 // with other command line flags, issue a warning.
462 // The generation minimums and the overall heap mimimum should
463 // be within one heap alignment.
464 if ((_min_gen1_size + _min_gen0_size + _min_alignment) < _min_heap_byte_size) {
465 warning("Inconsistency between minimum heap size and minimum "
466 "generation sizes: using minimum heap = " SIZE_FORMAT,
467 _min_heap_byte_size);
468 }
469 if (OldSize > _max_gen1_size) {
470 warning("Inconsistency between maximum heap size and maximum "
471 "generation sizes: using maximum heap = " SIZE_FORMAT
472 " -XX:OldSize flag is being ignored",
473 _max_heap_byte_size);
474 }
475 // If there is an inconsistency between the OldSize and the minimum and/or
476 // initial size of gen0, since OldSize was explicitly set, OldSize wins.
477 if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size,
478 _min_heap_byte_size, OldSize)) {
479 if (PrintGCDetails && Verbose) {
480 gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
481 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
482 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
483 }
484 }
485 // Initial size
486 if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,
487 _initial_heap_byte_size, OldSize)) {
488 if (PrintGCDetails && Verbose) {
489 gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
490 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
491 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
492 }
493 }
494 }
495 // Enforce the maximum gen1 size.
496 _min_gen1_size = MIN2(_min_gen1_size, _max_gen1_size);
497
498 // Check that min gen1 <= initial gen1 <= max gen1
499 _initial_gen1_size = MAX2(_initial_gen1_size, _min_gen1_size);
500 _initial_gen1_size = MIN2(_initial_gen1_size, _max_gen1_size);
501
502 if (PrintGCDetails && Verbose) {
503 gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 "
504 SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT,
505 _min_gen1_size, _initial_gen1_size, _max_gen1_size);
506 }
507 }
508
509 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
510 bool is_tlab,
511 bool* gc_overhead_limit_was_exceeded) {
512 GenCollectedHeap *gch = GenCollectedHeap::heap();
513
514 debug_only(gch->check_for_valid_allocation_state());
515 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
516
517 // In general gc_overhead_limit_was_exceeded should be false so
518 // set it so here and reset it to true only if the gc time
519 // limit is being exceeded as checked below.
520 *gc_overhead_limit_was_exceeded = false;
521
522 HeapWord* result = NULL;
523
524 // Loop until the allocation is satisified,
525 // or unsatisfied after GC.
526 for (int try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) {
527 HandleMark hm; // discard any handles allocated in each iteration
528
529 // First allocation attempt is lock-free.
530 Generation *gen0 = gch->get_gen(0);
531 assert(gen0->supports_inline_contig_alloc(),
532 "Otherwise, must do alloc within heap lock");
533 if (gen0->should_allocate(size, is_tlab)) {
534 result = gen0->par_allocate(size, is_tlab);
535 if (result != NULL) {
536 assert(gch->is_in_reserved(result), "result not in heap");
537 return result;
538 }
539 }
540 unsigned int gc_count_before; // read inside the Heap_lock locked region
541 {
542 MutexLocker ml(Heap_lock);
543 if (PrintGC && Verbose) {
544 gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:"
545 " attempting locked slow path allocation");
546 }
547 // Note that only large objects get a shot at being
548 // allocated in later generations.
549 bool first_only = ! should_try_older_generation_allocation(size);
550
551 result = gch->attempt_allocation(size, is_tlab, first_only);
552 if (result != NULL) {
553 assert(gch->is_in_reserved(result), "result not in heap");
554 return result;
555 }
556
557 if (GC_locker::is_active_and_needs_gc()) {
558 if (is_tlab) {
559 return NULL; // Caller will retry allocating individual object
560 }
561 if (!gch->is_maximal_no_gc()) {
562 // Try and expand heap to satisfy request
563 result = expand_heap_and_allocate(size, is_tlab);
564 // result could be null if we are out of space
565 if (result != NULL) {
566 return result;
567 }
568 }
569
570 if (gclocker_stalled_count > GCLockerRetryAllocationCount) {
571 return NULL; // we didn't get to do a GC and we didn't get any memory
572 }
573
574 // If this thread is not in a jni critical section, we stall
575 // the requestor until the critical section has cleared and
576 // GC allowed. When the critical section clears, a GC is
577 // initiated by the last thread exiting the critical section; so
578 // we retry the allocation sequence from the beginning of the loop,
579 // rather than causing more, now probably unnecessary, GC attempts.
580 JavaThread* jthr = JavaThread::current();
581 if (!jthr->in_critical()) {
582 MutexUnlocker mul(Heap_lock);
583 // Wait for JNI critical section to be exited
584 GC_locker::stall_until_clear();
585 gclocker_stalled_count += 1;
586 continue;
587 } else {
588 if (CheckJNICalls) {
589 fatal("Possible deadlock due to allocating while"
590 " in jni critical section");
591 }
592 return NULL;
593 }
594 }
595
596 // Read the gc count while the heap lock is held.
597 gc_count_before = Universe::heap()->total_collections();
598 }
599
600 VM_GenCollectForAllocation op(size, is_tlab, gc_count_before);
601 VMThread::execute(&op);
602 if (op.prologue_succeeded()) {
603 result = op.result();
604 if (op.gc_locked()) {
605 assert(result == NULL, "must be NULL if gc_locked() is true");
606 continue; // retry and/or stall as necessary
607 }
608
609 // Allocation has failed and a collection
610 // has been done. If the gc time limit was exceeded the
611 // this time, return NULL so that an out-of-memory
612 // will be thrown. Clear gc_overhead_limit_exceeded
613 // so that the overhead exceeded does not persist.
614
615 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
616 const bool softrefs_clear = all_soft_refs_clear();
617
618 if (limit_exceeded && softrefs_clear) {
619 *gc_overhead_limit_was_exceeded = true;
620 size_policy()->set_gc_overhead_limit_exceeded(false);
621 if (op.result() != NULL) {
622 CollectedHeap::fill_with_object(op.result(), size);
623 }
624 return NULL;
625 }
626 assert(result == NULL || gch->is_in_reserved(result),
627 "result not in heap");
628 return result;
629 }
630
631 // Give a warning if we seem to be looping forever.
632 if ((QueuedAllocationWarningCount > 0) &&
633 (try_count % QueuedAllocationWarningCount == 0)) {
634 warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t"
635 " size=%d %s", try_count, size, is_tlab ? "(TLAB)" : "");
636 }
637 }
638 }
639
640 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size,
641 bool is_tlab) {
642 GenCollectedHeap *gch = GenCollectedHeap::heap();
643 HeapWord* result = NULL;
644 for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) {
645 Generation *gen = gch->get_gen(i);
646 if (gen->should_allocate(size, is_tlab)) {
647 result = gen->expand_and_allocate(size, is_tlab);
648 }
649 }
650 assert(result == NULL || gch->is_in_reserved(result), "result not in heap");
651 return result;
652 }
653
654 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size,
655 bool is_tlab) {
656 GenCollectedHeap *gch = GenCollectedHeap::heap();
657 GCCauseSetter x(gch, GCCause::_allocation_failure);
658 HeapWord* result = NULL;
659
660 assert(size != 0, "Precondition violated");
661 if (GC_locker::is_active_and_needs_gc()) {
662 // GC locker is active; instead of a collection we will attempt
663 // to expand the heap, if there's room for expansion.
664 if (!gch->is_maximal_no_gc()) {
665 result = expand_heap_and_allocate(size, is_tlab);
666 }
667 return result; // could be null if we are out of space
668 } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) {
669 // Do an incremental collection.
670 gch->do_collection(false /* full */,
671 false /* clear_all_soft_refs */,
672 size /* size */,
673 is_tlab /* is_tlab */,
674 number_of_generations() - 1 /* max_level */);
675 } else {
676 if (Verbose && PrintGCDetails) {
677 gclog_or_tty->print(" :: Trying full because partial may fail :: ");
678 }
679 // Try a full collection; see delta for bug id 6266275
680 // for the original code and why this has been simplified
681 // with from-space allocation criteria modified and
682 // such allocation moved out of the safepoint path.
683 gch->do_collection(true /* full */,
684 false /* clear_all_soft_refs */,
685 size /* size */,
686 is_tlab /* is_tlab */,
687 number_of_generations() - 1 /* max_level */);
688 }
689
690 result = gch->attempt_allocation(size, is_tlab, false /*first_only*/);
691
692 if (result != NULL) {
693 assert(gch->is_in_reserved(result), "result not in heap");
694 return result;
695 }
696
697 // OK, collection failed, try expansion.
698 result = expand_heap_and_allocate(size, is_tlab);
699 if (result != NULL) {
700 return result;
701 }
702
703 // If we reach this point, we're really out of memory. Try every trick
704 // we can to reclaim memory. Force collection of soft references. Force
705 // a complete compaction of the heap. Any additional methods for finding
706 // free memory should be here, especially if they are expensive. If this
707 // attempt fails, an OOM exception will be thrown.
708 {
709 UIntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
710
711 gch->do_collection(true /* full */,
712 true /* clear_all_soft_refs */,
713 size /* size */,
714 is_tlab /* is_tlab */,
715 number_of_generations() - 1 /* max_level */);
716 }
717
718 result = gch->attempt_allocation(size, is_tlab, false /* first_only */);
719 if (result != NULL) {
720 assert(gch->is_in_reserved(result), "result not in heap");
721 return result;
722 }
723
724 assert(!should_clear_all_soft_refs(),
725 "Flag should have been handled and cleared prior to this point");
726
727 // What else? We might try synchronous finalization later. If the total
728 // space available is large enough for the allocation, then a more
729 // complete compaction phase than we've tried so far might be
730 // appropriate.
731 return NULL;
732 }
733
734 MetaWord* CollectorPolicy::satisfy_failed_metadata_allocation(
735 ClassLoaderData* loader_data,
736 size_t word_size,
737 Metaspace::MetadataType mdtype) {
738 uint loop_count = 0;
739 uint gc_count = 0;
740 uint full_gc_count = 0;
741
742 assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock");
743
744 do {
745 MetaWord* result = NULL;
746 if (GC_locker::is_active_and_needs_gc()) {
747 // If the GC_locker is active, just expand and allocate.
748 // If that does not succeed, wait if this thread is not
749 // in a critical section itself.
750 result =
751 loader_data->metaspace_non_null()->expand_and_allocate(word_size,
752 mdtype);
753 if (result != NULL) {
754 return result;
755 }
756 JavaThread* jthr = JavaThread::current();
757 if (!jthr->in_critical()) {
758 // Wait for JNI critical section to be exited
759 GC_locker::stall_until_clear();
760 // The GC invoked by the last thread leaving the critical
761 // section will be a young collection and a full collection
762 // is (currently) needed for unloading classes so continue
763 // to the next iteration to get a full GC.
764 continue;
765 } else {
766 if (CheckJNICalls) {
767 fatal("Possible deadlock due to allocating while"
768 " in jni critical section");
769 }
770 return NULL;
771 }
772 }
773
774 { // Need lock to get self consistent gc_count's
775 MutexLocker ml(Heap_lock);
776 gc_count = Universe::heap()->total_collections();
777 full_gc_count = Universe::heap()->total_full_collections();
778 }
779
780 // Generate a VM operation
781 VM_CollectForMetadataAllocation op(loader_data,
782 word_size,
783 mdtype,
784 gc_count,
785 full_gc_count,
786 GCCause::_metadata_GC_threshold);
787 VMThread::execute(&op);
788
789 // If GC was locked out, try again. Check
790 // before checking success because the prologue
791 // could have succeeded and the GC still have
792 // been locked out.
793 if (op.gc_locked()) {
794 continue;
795 }
796
797 if (op.prologue_succeeded()) {
798 return op.result();
799 }
800 loop_count++;
801 if ((QueuedAllocationWarningCount > 0) &&
802 (loop_count % QueuedAllocationWarningCount == 0)) {
803 warning("satisfy_failed_metadata_allocation() retries %d times \n\t"
804 " size=%d", loop_count, word_size);
805 }
806 } while (true); // Until a GC is done
807 }
808
809 // Return true if any of the following is true:
810 // . the allocation won't fit into the current young gen heap
811 // . gc locker is occupied (jni critical section)
812 // . heap memory is tight -- the most recent previous collection
813 // was a full collection because a partial collection (would
814 // have) failed and is likely to fail again
815 bool GenCollectorPolicy::should_try_older_generation_allocation(
816 size_t word_size) const {
817 GenCollectedHeap* gch = GenCollectedHeap::heap();
818 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();
819 return (word_size > heap_word_size(gen0_capacity))
820 || GC_locker::is_active_and_needs_gc()
821 || gch->incremental_collection_failed();
822 }
823
824
825 //
826 // MarkSweepPolicy methods
827 //
828
829 MarkSweepPolicy::MarkSweepPolicy() {
830 initialize_all();
831 }
832
833 void MarkSweepPolicy::initialize_generations() {
834 _generations = NEW_C_HEAP_ARRAY3(GenerationSpecPtr, number_of_generations(), mtGC, 0, AllocFailStrategy::RETURN_NULL);
835 if (_generations == NULL) {
836 vm_exit_during_initialization("Unable to allocate gen spec");
837 }
838
839 if (UseParNewGC) {
840 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);
841 } else {
842 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);
843 }
844 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);
845
846 if (_generations[0] == NULL || _generations[1] == NULL) {
847 vm_exit_during_initialization("Unable to allocate gen spec");
848 }
849 }
850
851 void MarkSweepPolicy::initialize_gc_policy_counters() {
852 // initialize the policy counters - 2 collectors, 3 generations
853 if (UseParNewGC) {
854 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);
855 } else {
856 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
857 }
858 }