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 size_t x = base_size / (NewRatio+1);
150 size_t new_gen_size = x > _min_alignment ?
151 align_size_down(x, _min_alignment) :
152 _min_alignment;
153 return new_gen_size;
154 }
155
156 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,
157 size_t maximum_size) {
158 size_t alignment = _min_alignment;
159 size_t max_minus = maximum_size - alignment;
160 return desired_size < max_minus ? desired_size : max_minus;
161 }
162
163
164 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size,
165 size_t init_promo_size,
166 size_t init_survivor_size) {
167 const double max_gc_pause_sec = ((double) MaxGCPauseMillis)/1000.0;
168 _size_policy = new AdaptiveSizePolicy(init_eden_size,
169 init_promo_size,
170 init_survivor_size,
171 max_gc_pause_sec,
172 GCTimeRatio);
173 }
174
175 void GenCollectorPolicy::initialize_flags() {
176 // All sizes must be multiples of the generation granularity.
177 _min_alignment = (uintx) Generation::GenGrain;
178 _max_alignment = compute_max_alignment();
179
180 CollectorPolicy::initialize_flags();
181
182 // All generational heaps have a youngest gen; handle those flags here.
183
184 // Adjust max size parameters
185 if (NewSize > MaxNewSize) {
186 MaxNewSize = NewSize;
187 }
188 NewSize = align_size_down(NewSize, _min_alignment);
189 MaxNewSize = align_size_down(MaxNewSize, _min_alignment);
190
191 // Check validity of heap flags
192 assert(NewSize % _min_alignment == 0, "eden space alignment");
193 assert(MaxNewSize % _min_alignment == 0, "survivor space alignment");
194
195 if (NewSize < 3 * _min_alignment) {
196 // make sure there room for eden and two survivor spaces
197 vm_exit_during_initialization("Too small new size specified");
198 }
199 if (SurvivorRatio < 1 || NewRatio < 1) {
200 vm_exit_during_initialization("Invalid young gen ratio specified");
201 }
202 }
203
204 void TwoGenerationCollectorPolicy::initialize_flags() {
205 GenCollectorPolicy::initialize_flags();
206
207 OldSize = align_size_down(OldSize, _min_alignment);
208
209 if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(NewSize)) {
210 // NewRatio will be used later to set the young generation size so we use
211 // it to calculate how big the heap should be based on the requested OldSize
212 // and NewRatio.
213 assert(NewRatio > 0, "NewRatio should have been set up earlier");
214 size_t calculated_heapsize = (OldSize / NewRatio) * (NewRatio + 1);
215
216 calculated_heapsize = align_size_up(calculated_heapsize, _max_alignment);
217 MaxHeapSize = calculated_heapsize;
218 InitialHeapSize = calculated_heapsize;
219 }
220 MaxHeapSize = align_size_up(MaxHeapSize, _max_alignment);
221
222 // adjust max heap size if necessary
223 if (NewSize + OldSize > MaxHeapSize) {
224 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
225 // somebody set a maximum heap size with the intention that we should not
226 // exceed it. Adjust New/OldSize as necessary.
227 uintx calculated_size = NewSize + OldSize;
228 double shrink_factor = (double) MaxHeapSize / calculated_size;
229 // align
230 NewSize = align_size_down((uintx) (NewSize * shrink_factor), _min_alignment);
231 // OldSize is already aligned because above we aligned MaxHeapSize to
232 // _max_alignment, and we just made sure that NewSize is aligned to
233 // _min_alignment. In initialize_flags() we verified that _max_alignment
234 // is a multiple of _min_alignment.
235 OldSize = MaxHeapSize - NewSize;
236 } else {
237 MaxHeapSize = NewSize + OldSize;
238 }
239 }
240 // need to do this again
241 MaxHeapSize = align_size_up(MaxHeapSize, _max_alignment);
242
243 // adjust max heap size if necessary
244 if (NewSize + OldSize > MaxHeapSize) {
245 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
246 // somebody set a maximum heap size with the intention that we should not
247 // exceed it. Adjust New/OldSize as necessary.
248 uintx calculated_size = NewSize + OldSize;
249 double shrink_factor = (double) MaxHeapSize / calculated_size;
250 // align
251 NewSize = align_size_down((uintx) (NewSize * shrink_factor), _min_alignment);
252 // OldSize is already aligned because above we aligned MaxHeapSize to
253 // _max_alignment, and we just made sure that NewSize is aligned to
254 // _min_alignment. In initialize_flags() we verified that _max_alignment
255 // is a multiple of _min_alignment.
256 OldSize = MaxHeapSize - NewSize;
257 } else {
258 MaxHeapSize = NewSize + OldSize;
259 }
260 }
261 // need to do this again
262 MaxHeapSize = align_size_up(MaxHeapSize, _max_alignment);
263
264 always_do_update_barrier = UseConcMarkSweepGC;
265
266 // Check validity of heap flags
267 assert(OldSize % _min_alignment == 0, "old space alignment");
268 assert(MaxHeapSize % _max_alignment == 0, "maximum heap alignment");
269 }
270
271 // Values set on the command line win over any ergonomically
272 // set command line parameters.
273 // Ergonomic choice of parameters are done before this
274 // method is called. Values for command line parameters such as NewSize
275 // and MaxNewSize feed those ergonomic choices into this method.
276 // This method makes the final generation sizings consistent with
277 // themselves and with overall heap sizings.
278 // In the absence of explicitly set command line flags, policies
279 // such as the use of NewRatio are used to size the generation.
280 void GenCollectorPolicy::initialize_size_info() {
281 CollectorPolicy::initialize_size_info();
282
283 // _min_alignment is used for alignment within a generation.
284 // There is additional alignment done down stream for some
285 // collectors that sometimes causes unwanted rounding up of
286 // generations sizes.
287
288 // Determine maximum size of gen0
289
290 size_t max_new_size = 0;
291 if (FLAG_IS_CMDLINE(MaxNewSize) || FLAG_IS_ERGO(MaxNewSize)) {
292 if (MaxNewSize < _min_alignment) {
293 max_new_size = _min_alignment;
294 }
295 if (MaxNewSize >= _max_heap_byte_size) {
296 max_new_size = align_size_down(_max_heap_byte_size - _min_alignment,
297 _min_alignment);
298 warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or "
299 "greater than the entire heap (" SIZE_FORMAT "k). A "
300 "new generation size of " SIZE_FORMAT "k will be used.",
301 MaxNewSize/K, _max_heap_byte_size/K, max_new_size/K);
302 } else {
303 max_new_size = align_size_down(MaxNewSize, _min_alignment);
304 }
305
306 // The case for FLAG_IS_ERGO(MaxNewSize) could be treated
307 // specially at this point to just use an ergonomically set
308 // MaxNewSize to set max_new_size. For cases with small
309 // heaps such a policy often did not work because the MaxNewSize
310 // was larger than the entire heap. The interpretation given
311 // to ergonomically set flags is that the flags are set
312 // by different collectors for their own special needs but
313 // are not allowed to badly shape the heap. This allows the
314 // different collectors to decide what's best for themselves
315 // without having to factor in the overall heap shape. It
316 // can be the case in the future that the collectors would
317 // only make "wise" ergonomics choices and this policy could
318 // just accept those choices. The choices currently made are
319 // not always "wise".
320 } else {
321 max_new_size = scale_by_NewRatio_aligned(_max_heap_byte_size);
322 // Bound the maximum size by NewSize below (since it historically
323 // would have been NewSize and because the NewRatio calculation could
324 // yield a size that is too small) and bound it by MaxNewSize above.
325 // Ergonomics plays here by previously calculating the desired
326 // NewSize and MaxNewSize.
327 max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize);
328 }
329 assert(max_new_size > 0, "All paths should set max_new_size");
330
331 // Given the maximum gen0 size, determine the initial and
332 // minimum gen0 sizes.
333
334 if (_max_heap_byte_size == _min_heap_byte_size) {
335 // The maximum and minimum heap sizes are the same so
336 // the generations minimum and initial must be the
337 // same as its maximum.
338 _min_gen0_size = max_new_size;
339 _initial_gen0_size = max_new_size;
340 _max_gen0_size = max_new_size;
341 } else {
342 size_t desired_new_size = 0;
343 if (!FLAG_IS_DEFAULT(NewSize)) {
344 // If NewSize is set ergonomically (for example by cms), it
345 // would make sense to use it. If it is used, also use it
346 // to set the initial size. Although there is no reason
347 // the minimum size and the initial size have to be the same,
348 // the current implementation gets into trouble during the calculation
349 // of the tenured generation sizes if they are different.
350 // Note that this makes the initial size and the minimum size
351 // generally small compared to the NewRatio calculation.
352 _min_gen0_size = NewSize;
353 desired_new_size = NewSize;
354 max_new_size = MAX2(max_new_size, NewSize);
355 } else {
356 // For the case where NewSize is the default, use NewRatio
357 // to size the minimum and initial generation sizes.
358 // Use the default NewSize as the floor for these values. If
359 // NewRatio is overly large, the resulting sizes can be too
360 // small.
361 _min_gen0_size = MAX2(scale_by_NewRatio_aligned(_min_heap_byte_size), NewSize);
362 desired_new_size =
363 MAX2(scale_by_NewRatio_aligned(_initial_heap_byte_size), NewSize);
364 }
365
366 assert(_min_gen0_size > 0, "Sanity check");
367 _initial_gen0_size = desired_new_size;
368 _max_gen0_size = max_new_size;
369
370 // At this point the desirable initial and minimum sizes have been
371 // determined without regard to the maximum sizes.
372
373 // Bound the sizes by the corresponding overall heap sizes.
374 _min_gen0_size = bound_minus_alignment(_min_gen0_size, _min_heap_byte_size);
375 _initial_gen0_size = bound_minus_alignment(_initial_gen0_size, _initial_heap_byte_size);
376 _max_gen0_size = bound_minus_alignment(_max_gen0_size, _max_heap_byte_size);
377
378 // At this point all three sizes have been checked against the
379 // maximum sizes but have not been checked for consistency
380 // among the three.
381
382 // Final check min <= initial <= max
383 _min_gen0_size = MIN2(_min_gen0_size, _max_gen0_size);
384 _initial_gen0_size = MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size);
385 _min_gen0_size = MIN2(_min_gen0_size, _initial_gen0_size);
386 }
387
388 if (PrintGCDetails && Verbose) {
389 gclog_or_tty->print_cr("1: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
390 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
391 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
392 }
393 }
394
395 // Call this method during the sizing of the gen1 to make
396 // adjustments to gen0 because of gen1 sizing policy. gen0 initially has
397 // the most freedom in sizing because it is done before the
398 // policy for gen1 is applied. Once gen1 policies have been applied,
399 // there may be conflicts in the shape of the heap and this method
400 // is used to make the needed adjustments. The application of the
401 // policies could be more sophisticated (iterative for example) but
402 // keeping it simple also seems a worthwhile goal.
403 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr,
404 size_t* gen1_size_ptr,
405 const size_t heap_size,
406 const size_t min_gen1_size) {
407 bool result = false;
408
409 if ((*gen1_size_ptr + *gen0_size_ptr) > heap_size) {
410 if ((heap_size < (*gen0_size_ptr + min_gen1_size)) &&
411 (heap_size >= min_gen1_size + _min_alignment)) {
412 // Adjust gen0 down to accommodate min_gen1_size
413 *gen0_size_ptr = heap_size - min_gen1_size;
414 *gen0_size_ptr =
415 MAX2((uintx)align_size_down(*gen0_size_ptr, _min_alignment), _min_alignment);
416 assert(*gen0_size_ptr > 0, "Min gen0 is too large");
417 result = true;
418 } else {
419 *gen1_size_ptr = heap_size - *gen0_size_ptr;
420 *gen1_size_ptr =
421 MAX2((uintx)align_size_down(*gen1_size_ptr, _min_alignment), _min_alignment);
422 }
423 }
424 return result;
425 }
426
427 // Minimum sizes of the generations may be different than
428 // the initial sizes. An inconsistently is permitted here
429 // in the total size that can be specified explicitly by
430 // command line specification of OldSize and NewSize and
431 // also a command line specification of -Xms. Issue a warning
432 // but allow the values to pass.
433
434 void TwoGenerationCollectorPolicy::initialize_size_info() {
435 GenCollectorPolicy::initialize_size_info();
436
437 // At this point the minimum, initial and maximum sizes
438 // of the overall heap and of gen0 have been determined.
439 // The maximum gen1 size can be determined from the maximum gen0
440 // and maximum heap size since no explicit flags exits
441 // for setting the gen1 maximum.
442 _max_gen1_size = _max_heap_byte_size - _max_gen0_size;
443 _max_gen1_size =
444 MAX2((uintx)align_size_down(_max_gen1_size, _min_alignment), _min_alignment);
445 // If no explicit command line flag has been set for the
446 // gen1 size, use what is left for gen1.
447 if (FLAG_IS_DEFAULT(OldSize) || FLAG_IS_ERGO(OldSize)) {
448 // The user has not specified any value or ergonomics
449 // has chosen a value (which may or may not be consistent
450 // with the overall heap size). In either case make
451 // the minimum, maximum and initial sizes consistent
452 // with the gen0 sizes and the overall heap sizes.
453 assert(_min_heap_byte_size > _min_gen0_size,
454 "gen0 has an unexpected minimum size");
455 _min_gen1_size = _min_heap_byte_size - _min_gen0_size;
456 _min_gen1_size =
457 MAX2((uintx)align_size_down(_min_gen1_size, _min_alignment), _min_alignment);
458 _initial_gen1_size = _initial_heap_byte_size - _initial_gen0_size;
459 _initial_gen1_size =
460 MAX2((uintx)align_size_down(_initial_gen1_size, _min_alignment), _min_alignment);
461 } else {
462 // It's been explicitly set on the command line. Use the
463 // OldSize and then determine the consequences.
464 _min_gen1_size = OldSize;
465 _initial_gen1_size = OldSize;
466
467 // If the user has explicitly set an OldSize that is inconsistent
468 // with other command line flags, issue a warning.
469 // The generation minimums and the overall heap mimimum should
470 // be within one heap alignment.
471 if ((_min_gen1_size + _min_gen0_size + _min_alignment) < _min_heap_byte_size) {
472 warning("Inconsistency between minimum heap size and minimum "
473 "generation sizes: using minimum heap = " SIZE_FORMAT,
474 _min_heap_byte_size);
475 }
476 if ((OldSize > _max_gen1_size)) {
477 warning("Inconsistency between maximum heap size and maximum "
478 "generation sizes: using maximum heap = " SIZE_FORMAT
479 " -XX:OldSize flag is being ignored",
480 _max_heap_byte_size);
481 }
482 // If there is an inconsistency between the OldSize and the minimum and/or
483 // initial size of gen0, since OldSize was explicitly set, OldSize wins.
484 if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size,
485 _min_heap_byte_size, OldSize)) {
486 if (PrintGCDetails && Verbose) {
487 gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
488 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
489 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
490 }
491 }
492 // Initial size
493 if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,
494 _initial_heap_byte_size, OldSize)) {
495 if (PrintGCDetails && Verbose) {
496 gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
497 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
498 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
499 }
500 }
501 }
502 // Enforce the maximum gen1 size.
503 _min_gen1_size = MIN2(_min_gen1_size, _max_gen1_size);
504
505 // Check that min gen1 <= initial gen1 <= max gen1
506 _initial_gen1_size = MAX2(_initial_gen1_size, _min_gen1_size);
507 _initial_gen1_size = MIN2(_initial_gen1_size, _max_gen1_size);
508
509 if (PrintGCDetails && Verbose) {
510 gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 "
511 SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT,
512 _min_gen1_size, _initial_gen1_size, _max_gen1_size);
513 }
514 }
515
516 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
517 bool is_tlab,
518 bool* gc_overhead_limit_was_exceeded) {
519 GenCollectedHeap *gch = GenCollectedHeap::heap();
520
521 debug_only(gch->check_for_valid_allocation_state());
522 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
523
524 // In general gc_overhead_limit_was_exceeded should be false so
525 // set it so here and reset it to true only if the gc time
526 // limit is being exceeded as checked below.
527 *gc_overhead_limit_was_exceeded = false;
528
529 HeapWord* result = NULL;
530
531 // Loop until the allocation is satisified,
532 // or unsatisfied after GC.
533 for (int try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) {
534 HandleMark hm; // discard any handles allocated in each iteration
535
536 // First allocation attempt is lock-free.
537 Generation *gen0 = gch->get_gen(0);
538 assert(gen0->supports_inline_contig_alloc(),
539 "Otherwise, must do alloc within heap lock");
540 if (gen0->should_allocate(size, is_tlab)) {
541 result = gen0->par_allocate(size, is_tlab);
542 if (result != NULL) {
543 assert(gch->is_in_reserved(result), "result not in heap");
544 return result;
545 }
546 }
547 unsigned int gc_count_before; // read inside the Heap_lock locked region
548 {
549 MutexLocker ml(Heap_lock);
550 if (PrintGC && Verbose) {
551 gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:"
552 " attempting locked slow path allocation");
553 }
554 // Note that only large objects get a shot at being
555 // allocated in later generations.
556 bool first_only = ! should_try_older_generation_allocation(size);
557
558 result = gch->attempt_allocation(size, is_tlab, first_only);
559 if (result != NULL) {
560 assert(gch->is_in_reserved(result), "result not in heap");
561 return result;
562 }
563
564 if (GC_locker::is_active_and_needs_gc()) {
565 if (is_tlab) {
566 return NULL; // Caller will retry allocating individual object
567 }
568 if (!gch->is_maximal_no_gc()) {
569 // Try and expand heap to satisfy request
570 result = expand_heap_and_allocate(size, is_tlab);
571 // result could be null if we are out of space
572 if (result != NULL) {
573 return result;
574 }
575 }
576
577 if (gclocker_stalled_count > GCLockerRetryAllocationCount) {
578 return NULL; // we didn't get to do a GC and we didn't get any memory
579 }
580
581 // If this thread is not in a jni critical section, we stall
582 // the requestor until the critical section has cleared and
583 // GC allowed. When the critical section clears, a GC is
584 // initiated by the last thread exiting the critical section; so
585 // we retry the allocation sequence from the beginning of the loop,
586 // rather than causing more, now probably unnecessary, GC attempts.
587 JavaThread* jthr = JavaThread::current();
588 if (!jthr->in_critical()) {
589 MutexUnlocker mul(Heap_lock);
590 // Wait for JNI critical section to be exited
591 GC_locker::stall_until_clear();
592 gclocker_stalled_count += 1;
593 continue;
594 } else {
595 if (CheckJNICalls) {
596 fatal("Possible deadlock due to allocating while"
597 " in jni critical section");
598 }
599 return NULL;
600 }
601 }
602
603 // Read the gc count while the heap lock is held.
604 gc_count_before = Universe::heap()->total_collections();
605 }
606
607 VM_GenCollectForAllocation op(size,
608 is_tlab,
609 gc_count_before);
610 VMThread::execute(&op);
611 if (op.prologue_succeeded()) {
612 result = op.result();
613 if (op.gc_locked()) {
614 assert(result == NULL, "must be NULL if gc_locked() is true");
615 continue; // retry and/or stall as necessary
616 }
617
618 // Allocation has failed and a collection
619 // has been done. If the gc time limit was exceeded the
620 // this time, return NULL so that an out-of-memory
621 // will be thrown. Clear gc_overhead_limit_exceeded
622 // so that the overhead exceeded does not persist.
623
624 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
625 const bool softrefs_clear = all_soft_refs_clear();
626
627 if (limit_exceeded && softrefs_clear) {
628 *gc_overhead_limit_was_exceeded = true;
629 size_policy()->set_gc_overhead_limit_exceeded(false);
630 if (op.result() != NULL) {
631 CollectedHeap::fill_with_object(op.result(), size);
632 }
633 return NULL;
634 }
635 assert(result == NULL || gch->is_in_reserved(result),
636 "result not in heap");
637 return result;
638 }
639
640 // Give a warning if we seem to be looping forever.
641 if ((QueuedAllocationWarningCount > 0) &&
642 (try_count % QueuedAllocationWarningCount == 0)) {
643 warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t"
644 " size=%d %s", try_count, size, is_tlab ? "(TLAB)" : "");
645 }
646 }
647 }
648
649 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size,
650 bool is_tlab) {
651 GenCollectedHeap *gch = GenCollectedHeap::heap();
652 HeapWord* result = NULL;
653 for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) {
654 Generation *gen = gch->get_gen(i);
655 if (gen->should_allocate(size, is_tlab)) {
656 result = gen->expand_and_allocate(size, is_tlab);
657 }
658 }
659 assert(result == NULL || gch->is_in_reserved(result), "result not in heap");
660 return result;
661 }
662
663 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size,
664 bool is_tlab) {
665 GenCollectedHeap *gch = GenCollectedHeap::heap();
666 GCCauseSetter x(gch, GCCause::_allocation_failure);
667 HeapWord* result = NULL;
668
669 assert(size != 0, "Precondition violated");
670 if (GC_locker::is_active_and_needs_gc()) {
671 // GC locker is active; instead of a collection we will attempt
672 // to expand the heap, if there's room for expansion.
673 if (!gch->is_maximal_no_gc()) {
674 result = expand_heap_and_allocate(size, is_tlab);
675 }
676 return result; // could be null if we are out of space
677 } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) {
678 // Do an incremental collection.
679 gch->do_collection(false /* full */,
680 false /* clear_all_soft_refs */,
681 size /* size */,
682 is_tlab /* is_tlab */,
683 number_of_generations() - 1 /* max_level */);
684 } else {
685 if (Verbose && PrintGCDetails) {
686 gclog_or_tty->print(" :: Trying full because partial may fail :: ");
687 }
688 // Try a full collection; see delta for bug id 6266275
689 // for the original code and why this has been simplified
690 // with from-space allocation criteria modified and
691 // such allocation moved out of the safepoint path.
692 gch->do_collection(true /* full */,
693 false /* clear_all_soft_refs */,
694 size /* size */,
695 is_tlab /* is_tlab */,
696 number_of_generations() - 1 /* max_level */);
697 }
698
699 result = gch->attempt_allocation(size, is_tlab, false /*first_only*/);
700
701 if (result != NULL) {
702 assert(gch->is_in_reserved(result), "result not in heap");
703 return result;
704 }
705
706 // OK, collection failed, try expansion.
707 result = expand_heap_and_allocate(size, is_tlab);
708 if (result != NULL) {
709 return result;
710 }
711
712 // If we reach this point, we're really out of memory. Try every trick
713 // we can to reclaim memory. Force collection of soft references. Force
714 // a complete compaction of the heap. Any additional methods for finding
715 // free memory should be here, especially if they are expensive. If this
716 // attempt fails, an OOM exception will be thrown.
717 {
718 UIntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
719
720 gch->do_collection(true /* full */,
721 true /* clear_all_soft_refs */,
722 size /* size */,
723 is_tlab /* is_tlab */,
724 number_of_generations() - 1 /* max_level */);
725 }
726
727 result = gch->attempt_allocation(size, is_tlab, false /* first_only */);
728 if (result != NULL) {
729 assert(gch->is_in_reserved(result), "result not in heap");
730 return result;
731 }
732
733 assert(!should_clear_all_soft_refs(),
734 "Flag should have been handled and cleared prior to this point");
735
736 // What else? We might try synchronous finalization later. If the total
737 // space available is large enough for the allocation, then a more
738 // complete compaction phase than we've tried so far might be
739 // appropriate.
740 return NULL;
741 }
742
743 MetaWord* CollectorPolicy::satisfy_failed_metadata_allocation(
744 ClassLoaderData* loader_data,
745 size_t word_size,
746 Metaspace::MetadataType mdtype) {
747 uint loop_count = 0;
748 uint gc_count = 0;
749 uint full_gc_count = 0;
750
751 assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock");
752
753 do {
754 MetaWord* result = NULL;
755 if (GC_locker::is_active_and_needs_gc()) {
756 // If the GC_locker is active, just expand and allocate.
757 // If that does not succeed, wait if this thread is not
758 // in a critical section itself.
759 result =
760 loader_data->metaspace_non_null()->expand_and_allocate(word_size,
761 mdtype);
762 if (result != NULL) {
763 return result;
764 }
765 JavaThread* jthr = JavaThread::current();
766 if (!jthr->in_critical()) {
767 // Wait for JNI critical section to be exited
768 GC_locker::stall_until_clear();
769 // The GC invoked by the last thread leaving the critical
770 // section will be a young collection and a full collection
771 // is (currently) needed for unloading classes so continue
772 // to the next iteration to get a full GC.
773 continue;
774 } else {
775 if (CheckJNICalls) {
776 fatal("Possible deadlock due to allocating while"
777 " in jni critical section");
778 }
779 return NULL;
780 }
781 }
782
783 { // Need lock to get self consistent gc_count's
784 MutexLocker ml(Heap_lock);
785 gc_count = Universe::heap()->total_collections();
786 full_gc_count = Universe::heap()->total_full_collections();
787 }
788
789 // Generate a VM operation
790 VM_CollectForMetadataAllocation op(loader_data,
791 word_size,
792 mdtype,
793 gc_count,
794 full_gc_count,
795 GCCause::_metadata_GC_threshold);
796 VMThread::execute(&op);
797
798 // If GC was locked out, try again. Check
799 // before checking success because the prologue
800 // could have succeeded and the GC still have
801 // been locked out.
802 if (op.gc_locked()) {
803 continue;
804 }
805
806 if (op.prologue_succeeded()) {
807 return op.result();
808 }
809 loop_count++;
810 if ((QueuedAllocationWarningCount > 0) &&
811 (loop_count % QueuedAllocationWarningCount == 0)) {
812 warning("satisfy_failed_metadata_allocation() retries %d times \n\t"
813 " size=%d", loop_count, word_size);
814 }
815 } while (true); // Until a GC is done
816 }
817
818 // Return true if any of the following is true:
819 // . the allocation won't fit into the current young gen heap
820 // . gc locker is occupied (jni critical section)
821 // . heap memory is tight -- the most recent previous collection
822 // was a full collection because a partial collection (would
823 // have) failed and is likely to fail again
824 bool GenCollectorPolicy::should_try_older_generation_allocation(
825 size_t word_size) const {
826 GenCollectedHeap* gch = GenCollectedHeap::heap();
827 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();
828 return (word_size > heap_word_size(gen0_capacity))
829 || GC_locker::is_active_and_needs_gc()
830 || gch->incremental_collection_failed();
831 }
832
833
834 //
835 // MarkSweepPolicy methods
836 //
837
838 MarkSweepPolicy::MarkSweepPolicy() {
839 initialize_all();
840 }
841
842 void MarkSweepPolicy::initialize_generations() {
843 _generations = NEW_C_HEAP_ARRAY3(GenerationSpecPtr, number_of_generations(), mtGC, 0, AllocFailStrategy::RETURN_NULL);
844 if (_generations == NULL)
845 vm_exit_during_initialization("Unable to allocate gen spec");
846
847 if (UseParNewGC) {
848 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);
849 } else {
850 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);
851 }
852 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);
853
854 if (_generations[0] == NULL || _generations[1] == NULL)
855 vm_exit_during_initialization("Unable to allocate gen spec");
856 }
857
858 void MarkSweepPolicy::initialize_gc_policy_counters() {
859 // initialize the policy counters - 2 collectors, 3 generations
860 if (UseParNewGC) {
861 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);
862 } else {
863 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
864 }
865 }