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 // Align down. If the aligning result in 0, return 'alignment'.
51 static size_t restricted_align_down(size_t size, size_t alignment) {
52 return MAX2(alignment, align_size_down_(size, alignment));
53 }
54
55 void CollectorPolicy::initialize_flags() {
56 assert(_max_alignment >= _min_alignment,
57 err_msg("max_alignment: " SIZE_FORMAT " less than min_alignment: " SIZE_FORMAT,
58 _max_alignment, _min_alignment));
59 assert(_max_alignment % _min_alignment == 0,
60 err_msg("max_alignment: " SIZE_FORMAT " not aligned by min_alignment: " SIZE_FORMAT,
61 _max_alignment, _min_alignment));
62
63 if (MaxHeapSize < InitialHeapSize) {
64 vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
65 }
66
67 if (!is_size_aligned(MaxMetaspaceSize, _max_alignment)) {
68 FLAG_SET_ERGO(uintx, MaxMetaspaceSize,
69 restricted_align_down(MaxMetaspaceSize, _max_alignment));
70 }
71
72 if (MetaspaceSize > MaxMetaspaceSize) {
73 FLAG_SET_ERGO(uintx, MetaspaceSize, MaxMetaspaceSize);
74 }
75
76 if (!is_size_aligned(MetaspaceSize, _min_alignment)) {
77 FLAG_SET_ERGO(uintx, MetaspaceSize,
78 restricted_align_down(MetaspaceSize, _min_alignment));
79 }
80
81 assert(MetaspaceSize <= MaxMetaspaceSize, "Must be");
82
83 MinMetaspaceExpansion = restricted_align_down(MinMetaspaceExpansion, _min_alignment);
84 MaxMetaspaceExpansion = restricted_align_down(MaxMetaspaceExpansion, _min_alignment);
85
86 MinHeapDeltaBytes = align_size_up(MinHeapDeltaBytes, _min_alignment);
87
88 assert(MetaspaceSize % _min_alignment == 0, "metapace alignment");
89 assert(MaxMetaspaceSize % _max_alignment == 0, "maximum metaspace alignment");
90 if (MetaspaceSize < 256*K) {
91 vm_exit_during_initialization("Too small initial Metaspace size");
92 }
93 }
94
95 void CollectorPolicy::initialize_size_info() {
96 // User inputs from -mx and ms must be aligned
97 _min_heap_byte_size = align_size_up(Arguments::min_heap_size(), _min_alignment);
98 _initial_heap_byte_size = align_size_up(InitialHeapSize, _min_alignment);
99 _max_heap_byte_size = align_size_up(MaxHeapSize, _max_alignment);
100
101 // Check heap parameter properties
102 if (_initial_heap_byte_size < M) {
103 vm_exit_during_initialization("Too small initial heap");
104 }
105 // Check heap parameter properties
106 if (_min_heap_byte_size < M) {
107 vm_exit_during_initialization("Too small minimum heap");
108 }
109 if (_initial_heap_byte_size <= NewSize) {
110 // make sure there is at least some room in old space
111 vm_exit_during_initialization("Too small initial heap for new size specified");
112 }
113 if (_max_heap_byte_size < _min_heap_byte_size) {
114 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified");
115 }
116 if (_initial_heap_byte_size < _min_heap_byte_size) {
117 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified");
118 }
119 if (_max_heap_byte_size < _initial_heap_byte_size) {
120 vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
121 }
122
123 if (PrintGCDetails && Verbose) {
124 gclog_or_tty->print_cr("Minimum heap " SIZE_FORMAT " Initial heap "
125 SIZE_FORMAT " Maximum heap " SIZE_FORMAT,
126 _min_heap_byte_size, _initial_heap_byte_size, _max_heap_byte_size);
127 }
128 }
129
130 bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) {
131 bool result = _should_clear_all_soft_refs;
132 set_should_clear_all_soft_refs(false);
133 return result;
134 }
135
136 GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap,
137 int max_covered_regions) {
138 switch (rem_set_name()) {
139 case GenRemSet::CardTable: {
140 CardTableRS* res = new CardTableRS(whole_heap, max_covered_regions);
141 return res;
142 }
143 default:
144 guarantee(false, "unrecognized GenRemSet::Name");
145 return NULL;
146 }
147 }
148
149 void CollectorPolicy::cleared_all_soft_refs() {
150 // If near gc overhear limit, continue to clear SoftRefs. SoftRefs may
151 // have been cleared in the last collection but if the gc overhear
152 // limit continues to be near, SoftRefs should still be cleared.
153 if (size_policy() != NULL) {
154 _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near();
155 }
156 _all_soft_refs_clear = true;
157 }
158
159 size_t CollectorPolicy::compute_max_alignment() {
160 // The card marking array and the offset arrays for old generations are
161 // committed in os pages as well. Make sure they are entirely full (to
162 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
163 // byte entry and the os page size is 4096, the maximum heap size should
164 // be 512*4096 = 2MB aligned.
165
166 // There is only the GenRemSet in Hotspot and only the GenRemSet::CardTable
167 // is supported.
168 // Requirements of any new remembered set implementations must be added here.
169 size_t alignment = GenRemSet::max_alignment_constraint(GenRemSet::CardTable);
170
171 // Parallel GC does its own alignment of the generations to avoid requiring a
172 // large page (256M on some platforms) for the permanent generation. The
173 // other collectors should also be updated to do their own alignment and then
174 // this use of lcm() should be removed.
175 if (UseLargePages && !UseParallelGC) {
176 // in presence of large pages we have to make sure that our
177 // alignment is large page aware
178 alignment = lcm(os::large_page_size(), alignment);
179 }
180
181 return alignment;
182 }
183
184 // GenCollectorPolicy methods.
185
186 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {
187 size_t x = base_size / (NewRatio+1);
188 size_t new_gen_size = x > _min_alignment ?
189 align_size_down(x, _min_alignment) : _min_alignment;
190 return new_gen_size;
191 }
192
193 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,
194 size_t maximum_size) {
195 size_t alignment = _min_alignment;
196 size_t max_minus = maximum_size - alignment;
197 return desired_size < max_minus ? desired_size : max_minus;
198 }
199
200
201 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size,
202 size_t init_promo_size,
203 size_t init_survivor_size) {
204 const double max_gc_pause_sec = ((double) MaxGCPauseMillis)/1000.0;
205 _size_policy = new AdaptiveSizePolicy(init_eden_size,
206 init_promo_size,
207 init_survivor_size,
208 max_gc_pause_sec,
209 GCTimeRatio);
210 }
211
212 void GenCollectorPolicy::initialize_flags() {
213 // All sizes must be multiples of the generation granularity.
214 _min_alignment = (uintx) Generation::GenGrain;
215 _max_alignment = compute_max_alignment();
216
217 CollectorPolicy::initialize_flags();
218
219 // All generational heaps have a youngest gen; handle those flags here.
220
221 // Adjust max size parameters
222 if (NewSize > MaxNewSize) {
223 MaxNewSize = NewSize;
224 }
225 NewSize = align_size_down(NewSize, _min_alignment);
226 MaxNewSize = align_size_down(MaxNewSize, _min_alignment);
227
228 // Check validity of heap flags
229 assert(NewSize % _min_alignment == 0, "eden space alignment");
230 assert(MaxNewSize % _min_alignment == 0, "survivor space alignment");
231
232 if (NewSize < 3 * _min_alignment) {
233 // make sure there room for eden and two survivor spaces
234 vm_exit_during_initialization("Too small new size specified");
235 }
236 if (SurvivorRatio < 1 || NewRatio < 1) {
237 vm_exit_during_initialization("Invalid young gen ratio specified");
238 }
239 }
240
241 void TwoGenerationCollectorPolicy::initialize_flags() {
242 GenCollectorPolicy::initialize_flags();
243
244 OldSize = align_size_down(OldSize, _min_alignment);
245
246 if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(NewSize)) {
247 // NewRatio will be used later to set the young generation size so we use
248 // it to calculate how big the heap should be based on the requested OldSize
249 // and NewRatio.
250 assert(NewRatio > 0, "NewRatio should have been set up earlier");
251 size_t calculated_heapsize = (OldSize / NewRatio) * (NewRatio + 1);
252
253 calculated_heapsize = align_size_up(calculated_heapsize, _max_alignment);
254 MaxHeapSize = calculated_heapsize;
255 InitialHeapSize = calculated_heapsize;
256 }
257 MaxHeapSize = align_size_up(MaxHeapSize, _max_alignment);
258
259 // adjust max heap size if necessary
260 if (NewSize + OldSize > MaxHeapSize) {
261 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
262 // Somebody has set a maximum heap size with the intention that we should not
263 // exceed it. Adjust New/OldSize as necessary.
264 uintx calculated_size = NewSize + OldSize;
265 double shrink_factor = (double) MaxHeapSize / calculated_size;
266 // align
267 NewSize = align_size_down((uintx) (NewSize * shrink_factor), _min_alignment);
268 // OldSize is already aligned because above we aligned MaxHeapSize to
269 // _max_alignment, and we just made sure that NewSize is aligned to
270 // _min_alignment. In initialize_flags() we verified that _max_alignment
271 // is a multiple of _min_alignment.
272 OldSize = MaxHeapSize - NewSize;
273 } else {
274 MaxHeapSize = NewSize + OldSize;
275 }
276 }
277 // need to do this again
278 MaxHeapSize = align_size_up(MaxHeapSize, _max_alignment);
279
280 // adjust max heap size if necessary
281 if (NewSize + OldSize > MaxHeapSize) {
282 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
283 // somebody set a maximum heap size with the intention that we should not
284 // exceed it. Adjust New/OldSize as necessary.
285 uintx calculated_size = NewSize + OldSize;
286 double shrink_factor = (double) MaxHeapSize / calculated_size;
287 // align
288 NewSize = align_size_down((uintx) (NewSize * shrink_factor), _min_alignment);
289 // OldSize is already aligned because above we aligned MaxHeapSize to
290 // _max_alignment, and we just made sure that NewSize is aligned to
291 // _min_alignment. In initialize_flags() we verified that _max_alignment
292 // is a multiple of _min_alignment.
293 OldSize = MaxHeapSize - NewSize;
294 } else {
295 MaxHeapSize = NewSize + OldSize;
296 }
297 }
298 // need to do this again
299 MaxHeapSize = align_size_up(MaxHeapSize, _max_alignment);
300
301 always_do_update_barrier = UseConcMarkSweepGC;
302
303 // Check validity of heap flags
304 assert(OldSize % _min_alignment == 0, "old space alignment");
305 assert(MaxHeapSize % _max_alignment == 0, "maximum heap alignment");
306 }
307
308 // Values set on the command line win over any ergonomically
309 // set command line parameters.
310 // Ergonomic choice of parameters are done before this
311 // method is called. Values for command line parameters such as NewSize
312 // and MaxNewSize feed those ergonomic choices into this method.
313 // This method makes the final generation sizings consistent with
314 // themselves and with overall heap sizings.
315 // In the absence of explicitly set command line flags, policies
316 // such as the use of NewRatio are used to size the generation.
317 void GenCollectorPolicy::initialize_size_info() {
318 CollectorPolicy::initialize_size_info();
319
320 // _min_alignment is used for alignment within a generation.
321 // There is additional alignment done down stream for some
322 // collectors that sometimes causes unwanted rounding up of
323 // generations sizes.
324
325 // Determine maximum size of gen0
326
327 size_t max_new_size = 0;
328 if (FLAG_IS_CMDLINE(MaxNewSize) || FLAG_IS_ERGO(MaxNewSize)) {
329 if (MaxNewSize < _min_alignment) {
330 max_new_size = _min_alignment;
331 }
332 if (MaxNewSize >= _max_heap_byte_size) {
333 max_new_size = align_size_down(_max_heap_byte_size - _min_alignment,
334 _min_alignment);
335 warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or "
336 "greater than the entire heap (" SIZE_FORMAT "k). A "
337 "new generation size of " SIZE_FORMAT "k will be used.",
338 MaxNewSize/K, _max_heap_byte_size/K, max_new_size/K);
339 } else {
340 max_new_size = align_size_down(MaxNewSize, _min_alignment);
341 }
342
343 // The case for FLAG_IS_ERGO(MaxNewSize) could be treated
344 // specially at this point to just use an ergonomically set
345 // MaxNewSize to set max_new_size. For cases with small
346 // heaps such a policy often did not work because the MaxNewSize
347 // was larger than the entire heap. The interpretation given
348 // to ergonomically set flags is that the flags are set
349 // by different collectors for their own special needs but
350 // are not allowed to badly shape the heap. This allows the
351 // different collectors to decide what's best for themselves
352 // without having to factor in the overall heap shape. It
353 // can be the case in the future that the collectors would
354 // only make "wise" ergonomics choices and this policy could
355 // just accept those choices. The choices currently made are
356 // not always "wise".
357 } else {
358 max_new_size = scale_by_NewRatio_aligned(_max_heap_byte_size);
359 // Bound the maximum size by NewSize below (since it historically
360 // would have been NewSize and because the NewRatio calculation could
361 // yield a size that is too small) and bound it by MaxNewSize above.
362 // Ergonomics plays here by previously calculating the desired
363 // NewSize and MaxNewSize.
364 max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize);
365 }
366 assert(max_new_size > 0, "All paths should set max_new_size");
367
368 // Given the maximum gen0 size, determine the initial and
369 // minimum gen0 sizes.
370
371 if (_max_heap_byte_size == _min_heap_byte_size) {
372 // The maximum and minimum heap sizes are the same so
373 // the generations minimum and initial must be the
374 // same as its maximum.
375 _min_gen0_size = max_new_size;
376 _initial_gen0_size = max_new_size;
377 _max_gen0_size = max_new_size;
378 } else {
379 size_t desired_new_size = 0;
380 if (!FLAG_IS_DEFAULT(NewSize)) {
381 // If NewSize is set ergonomically (for example by cms), it
382 // would make sense to use it. If it is used, also use it
383 // to set the initial size. Although there is no reason
384 // the minimum size and the initial size have to be the same,
385 // the current implementation gets into trouble during the calculation
386 // of the tenured generation sizes if they are different.
387 // Note that this makes the initial size and the minimum size
388 // generally small compared to the NewRatio calculation.
389 _min_gen0_size = NewSize;
390 desired_new_size = NewSize;
391 max_new_size = MAX2(max_new_size, NewSize);
392 } else {
393 // For the case where NewSize is the default, use NewRatio
394 // to size the minimum and initial generation sizes.
395 // Use the default NewSize as the floor for these values. If
396 // NewRatio is overly large, the resulting sizes can be too
397 // small.
398 _min_gen0_size = MAX2(scale_by_NewRatio_aligned(_min_heap_byte_size), NewSize);
399 desired_new_size =
400 MAX2(scale_by_NewRatio_aligned(_initial_heap_byte_size), NewSize);
401 }
402
403 assert(_min_gen0_size > 0, "Sanity check");
404 _initial_gen0_size = desired_new_size;
405 _max_gen0_size = max_new_size;
406
407 // At this point the desirable initial and minimum sizes have been
408 // determined without regard to the maximum sizes.
409
410 // Bound the sizes by the corresponding overall heap sizes.
411 _min_gen0_size = bound_minus_alignment(_min_gen0_size, _min_heap_byte_size);
412 _initial_gen0_size = bound_minus_alignment(_initial_gen0_size, _initial_heap_byte_size);
413 _max_gen0_size = bound_minus_alignment(_max_gen0_size, _max_heap_byte_size);
414
415 // At this point all three sizes have been checked against the
416 // maximum sizes but have not been checked for consistency
417 // among the three.
418
419 // Final check min <= initial <= max
420 _min_gen0_size = MIN2(_min_gen0_size, _max_gen0_size);
421 _initial_gen0_size = MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size);
422 _min_gen0_size = MIN2(_min_gen0_size, _initial_gen0_size);
423 }
424
425 if (PrintGCDetails && Verbose) {
426 gclog_or_tty->print_cr("1: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
427 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
428 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
429 }
430 }
431
432 // Call this method during the sizing of the gen1 to make
433 // adjustments to gen0 because of gen1 sizing policy. gen0 initially has
434 // the most freedom in sizing because it is done before the
435 // policy for gen1 is applied. Once gen1 policies have been applied,
436 // there may be conflicts in the shape of the heap and this method
437 // is used to make the needed adjustments. The application of the
438 // policies could be more sophisticated (iterative for example) but
439 // keeping it simple also seems a worthwhile goal.
440 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr,
441 size_t* gen1_size_ptr,
442 const size_t heap_size,
443 const size_t min_gen1_size) {
444 bool result = false;
445
446 if ((*gen1_size_ptr + *gen0_size_ptr) > heap_size) {
447 if ((heap_size < (*gen0_size_ptr + min_gen1_size)) &&
448 (heap_size >= min_gen1_size + _min_alignment)) {
449 // Adjust gen0 down to accommodate min_gen1_size
450 *gen0_size_ptr =
451 MAX2((uintx)align_size_down(heap_size - min_gen1_size, _min_alignment),
452 _min_alignment);
453 assert(*gen0_size_ptr > 0, "Min gen0 is too large");
454 result = true;
455 } else {
456 *gen1_size_ptr =
457 MAX2((uintx)align_size_down(heap_size - *gen0_size_ptr, _min_alignment),
458 _min_alignment);
459 }
460 }
461 return result;
462 }
463
464 // Minimum sizes of the generations may be different than
465 // the initial sizes. An inconsistency is permitted here
466 // in the total size that can be specified explicitly by
467 // command line specification of OldSize and NewSize and
468 // also a command line specification of -Xms. Issue a warning
469 // but allow the values to pass.
470
471 void TwoGenerationCollectorPolicy::initialize_size_info() {
472 GenCollectorPolicy::initialize_size_info();
473
474 // At this point the minimum, initial and maximum sizes
475 // of the overall heap and of gen0 have been determined.
476 // The maximum gen1 size can be determined from the maximum gen0
477 // and maximum heap size since no explicit flags exist
478 // for setting the gen1 maximum.
479 _max_gen1_size = _max_heap_byte_size - _max_gen0_size;
480 _max_gen1_size =
481 MAX2((uintx)align_size_down(_max_gen1_size, _min_alignment), _min_alignment);
482
483 // If no explicit command line flag has been set for the
484 // gen1 size, use what is left for gen1.
485 if (FLAG_IS_DEFAULT(OldSize) || FLAG_IS_ERGO(OldSize)) {
486 // The user has not specified any value or ergonomics
487 // has chosen a value (which may or may not be consistent
488 // with the overall heap size). In either case make
489 // the minimum, maximum and initial sizes consistent
490 // with the gen0 sizes and the overall heap sizes.
491 assert(_min_heap_byte_size > _min_gen0_size,
492 "gen0 has an unexpected minimum size");
493 _min_gen1_size = _min_heap_byte_size - _min_gen0_size;
494 _min_gen1_size = MAX2((uintx)align_size_down(_min_gen1_size, _min_alignment),
495 _min_alignment);
496 _initial_gen1_size = _initial_heap_byte_size - _initial_gen0_size;
497 _initial_gen1_size = MAX2((uintx)align_size_down(_initial_gen1_size, _min_alignment),
498 _min_alignment);
499 } else {
500 // OldSize has been explicitly set on the command line. Use the
501 // OldSize and then determine the consequences.
502 _min_gen1_size = OldSize;
503 _initial_gen1_size = OldSize;
504
505 // If the user has explicitly set an OldSize that is inconsistent
506 // with other command line flags, issue a warning.
507 // The generation minimums and the overall heap minimum should
508 // be within one heap alignment.
509 if ((_min_gen1_size + _min_gen0_size + _min_alignment) < _min_heap_byte_size) {
510 warning("Inconsistency between minimum heap size and minimum "
511 "generation sizes: using minimum heap = " SIZE_FORMAT,
512 _min_heap_byte_size);
513 }
514 if (OldSize > _max_gen1_size) {
515 warning("Inconsistency between maximum heap size and maximum "
516 "generation sizes: using maximum heap = " SIZE_FORMAT
517 " -XX:OldSize flag is being ignored",
518 _max_heap_byte_size);
519 }
520 // If there is an inconsistency between the OldSize and the minimum and/or
521 // initial size of gen0, since OldSize was explicitly set, OldSize wins.
522 if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size,
523 _min_heap_byte_size, OldSize)) {
524 if (PrintGCDetails && Verbose) {
525 gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
526 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
527 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
528 }
529 }
530 // The same as above for the old gen initial size
531 if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,
532 _initial_heap_byte_size, OldSize)) {
533 if (PrintGCDetails && Verbose) {
534 gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
535 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
536 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
537 }
538 }
539 }
540 // Enforce the maximum gen1 size.
541 _min_gen1_size = MIN2(_min_gen1_size, _max_gen1_size);
542
543 // Check that min gen1 <= initial gen1 <= max gen1
544 _initial_gen1_size = MAX2(_initial_gen1_size, _min_gen1_size);
545 _initial_gen1_size = MIN2(_initial_gen1_size, _max_gen1_size);
546
547 if (PrintGCDetails && Verbose) {
548 gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 "
549 SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT,
550 _min_gen1_size, _initial_gen1_size, _max_gen1_size);
551 }
552 }
553
554 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
555 bool is_tlab,
556 bool* gc_overhead_limit_was_exceeded) {
557 GenCollectedHeap *gch = GenCollectedHeap::heap();
558
559 debug_only(gch->check_for_valid_allocation_state());
560 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
561
562 // In general gc_overhead_limit_was_exceeded should be false so
563 // set it so here and reset it to true only if the gc time
564 // limit is being exceeded as checked below.
565 *gc_overhead_limit_was_exceeded = false;
566
567 HeapWord* result = NULL;
568
569 // Loop until the allocation is satisfied, or unsatisfied after GC.
570 for (int try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) {
571 HandleMark hm; // discard any handles allocated in each iteration
572
573 // First allocation attempt is lock-free.
574 Generation *gen0 = gch->get_gen(0);
575 assert(gen0->supports_inline_contig_alloc(),
576 "Otherwise, must do alloc within heap lock");
577 if (gen0->should_allocate(size, is_tlab)) {
578 result = gen0->par_allocate(size, is_tlab);
579 if (result != NULL) {
580 assert(gch->is_in_reserved(result), "result not in heap");
581 return result;
582 }
583 }
584 unsigned int gc_count_before; // read inside the Heap_lock locked region
585 {
586 MutexLocker ml(Heap_lock);
587 if (PrintGC && Verbose) {
588 gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:"
589 " attempting locked slow path allocation");
590 }
591 // Note that only large objects get a shot at being
592 // allocated in later generations.
593 bool first_only = ! should_try_older_generation_allocation(size);
594
595 result = gch->attempt_allocation(size, is_tlab, first_only);
596 if (result != NULL) {
597 assert(gch->is_in_reserved(result), "result not in heap");
598 return result;
599 }
600
601 if (GC_locker::is_active_and_needs_gc()) {
602 if (is_tlab) {
603 return NULL; // Caller will retry allocating individual object
604 }
605 if (!gch->is_maximal_no_gc()) {
606 // Try and expand heap to satisfy request
607 result = expand_heap_and_allocate(size, is_tlab);
608 // result could be null if we are out of space
609 if (result != NULL) {
610 return result;
611 }
612 }
613
614 if (gclocker_stalled_count > GCLockerRetryAllocationCount) {
615 return NULL; // we didn't get to do a GC and we didn't get any memory
616 }
617
618 // If this thread is not in a jni critical section, we stall
619 // the requestor until the critical section has cleared and
620 // GC allowed. When the critical section clears, a GC is
621 // initiated by the last thread exiting the critical section; so
622 // we retry the allocation sequence from the beginning of the loop,
623 // rather than causing more, now probably unnecessary, GC attempts.
624 JavaThread* jthr = JavaThread::current();
625 if (!jthr->in_critical()) {
626 MutexUnlocker mul(Heap_lock);
627 // Wait for JNI critical section to be exited
628 GC_locker::stall_until_clear();
629 gclocker_stalled_count += 1;
630 continue;
631 } else {
632 if (CheckJNICalls) {
633 fatal("Possible deadlock due to allocating while"
634 " in jni critical section");
635 }
636 return NULL;
637 }
638 }
639
640 // Read the gc count while the heap lock is held.
641 gc_count_before = Universe::heap()->total_collections();
642 }
643
644 VM_GenCollectForAllocation op(size,
645 is_tlab,
646 gc_count_before);
647 VMThread::execute(&op);
648 if (op.prologue_succeeded()) {
649 result = op.result();
650 if (op.gc_locked()) {
651 assert(result == NULL, "must be NULL if gc_locked() is true");
652 continue; // retry and/or stall as necessary
653 }
654
655 // Allocation has failed and a collection
656 // has been done. If the gc time limit was exceeded the
657 // this time, return NULL so that an out-of-memory
658 // will be thrown. Clear gc_overhead_limit_exceeded
659 // so that the overhead exceeded does not persist.
660
661 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
662 const bool softrefs_clear = all_soft_refs_clear();
663
664 if (limit_exceeded && softrefs_clear) {
665 *gc_overhead_limit_was_exceeded = true;
666 size_policy()->set_gc_overhead_limit_exceeded(false);
667 if (op.result() != NULL) {
668 CollectedHeap::fill_with_object(op.result(), size);
669 }
670 return NULL;
671 }
672 assert(result == NULL || gch->is_in_reserved(result),
673 "result not in heap");
674 return result;
675 }
676
677 // Give a warning if we seem to be looping forever.
678 if ((QueuedAllocationWarningCount > 0) &&
679 (try_count % QueuedAllocationWarningCount == 0)) {
680 warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t"
681 " size=%d %s", try_count, size, is_tlab ? "(TLAB)" : "");
682 }
683 }
684 }
685
686 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size,
687 bool is_tlab) {
688 GenCollectedHeap *gch = GenCollectedHeap::heap();
689 HeapWord* result = NULL;
690 for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) {
691 Generation *gen = gch->get_gen(i);
692 if (gen->should_allocate(size, is_tlab)) {
693 result = gen->expand_and_allocate(size, is_tlab);
694 }
695 }
696 assert(result == NULL || gch->is_in_reserved(result), "result not in heap");
697 return result;
698 }
699
700 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size,
701 bool is_tlab) {
702 GenCollectedHeap *gch = GenCollectedHeap::heap();
703 GCCauseSetter x(gch, GCCause::_allocation_failure);
704 HeapWord* result = NULL;
705
706 assert(size != 0, "Precondition violated");
707 if (GC_locker::is_active_and_needs_gc()) {
708 // GC locker is active; instead of a collection we will attempt
709 // to expand the heap, if there's room for expansion.
710 if (!gch->is_maximal_no_gc()) {
711 result = expand_heap_and_allocate(size, is_tlab);
712 }
713 return result; // could be null if we are out of space
714 } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) {
715 // Do an incremental collection.
716 gch->do_collection(false /* full */,
717 false /* clear_all_soft_refs */,
718 size /* size */,
719 is_tlab /* is_tlab */,
720 number_of_generations() - 1 /* max_level */);
721 } else {
722 if (Verbose && PrintGCDetails) {
723 gclog_or_tty->print(" :: Trying full because partial may fail :: ");
724 }
725 // Try a full collection; see delta for bug id 6266275
726 // for the original code and why this has been simplified
727 // with from-space allocation criteria modified and
728 // such allocation moved out of the safepoint path.
729 gch->do_collection(true /* full */,
730 false /* clear_all_soft_refs */,
731 size /* size */,
732 is_tlab /* is_tlab */,
733 number_of_generations() - 1 /* max_level */);
734 }
735
736 result = gch->attempt_allocation(size, is_tlab, false /*first_only*/);
737
738 if (result != NULL) {
739 assert(gch->is_in_reserved(result), "result not in heap");
740 return result;
741 }
742
743 // OK, collection failed, try expansion.
744 result = expand_heap_and_allocate(size, is_tlab);
745 if (result != NULL) {
746 return result;
747 }
748
749 // If we reach this point, we're really out of memory. Try every trick
750 // we can to reclaim memory. Force collection of soft references. Force
751 // a complete compaction of the heap. Any additional methods for finding
752 // free memory should be here, especially if they are expensive. If this
753 // attempt fails, an OOM exception will be thrown.
754 {
755 UIntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
756
757 gch->do_collection(true /* full */,
758 true /* clear_all_soft_refs */,
759 size /* size */,
760 is_tlab /* is_tlab */,
761 number_of_generations() - 1 /* max_level */);
762 }
763
764 result = gch->attempt_allocation(size, is_tlab, false /* first_only */);
765 if (result != NULL) {
766 assert(gch->is_in_reserved(result), "result not in heap");
767 return result;
768 }
769
770 assert(!should_clear_all_soft_refs(),
771 "Flag should have been handled and cleared prior to this point");
772
773 // What else? We might try synchronous finalization later. If the total
774 // space available is large enough for the allocation, then a more
775 // complete compaction phase than we've tried so far might be
776 // appropriate.
777 return NULL;
778 }
779
780 MetaWord* CollectorPolicy::satisfy_failed_metadata_allocation(
781 ClassLoaderData* loader_data,
782 size_t word_size,
783 Metaspace::MetadataType mdtype) {
784 uint loop_count = 0;
785 uint gc_count = 0;
786 uint full_gc_count = 0;
787
788 assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock");
789
790 do {
791 MetaWord* result = NULL;
792 if (GC_locker::is_active_and_needs_gc()) {
793 // If the GC_locker is active, just expand and allocate.
794 // If that does not succeed, wait if this thread is not
795 // in a critical section itself.
796 result =
797 loader_data->metaspace_non_null()->expand_and_allocate(word_size,
798 mdtype);
799 if (result != NULL) {
800 return result;
801 }
802 JavaThread* jthr = JavaThread::current();
803 if (!jthr->in_critical()) {
804 // Wait for JNI critical section to be exited
805 GC_locker::stall_until_clear();
806 // The GC invoked by the last thread leaving the critical
807 // section will be a young collection and a full collection
808 // is (currently) needed for unloading classes so continue
809 // to the next iteration to get a full GC.
810 continue;
811 } else {
812 if (CheckJNICalls) {
813 fatal("Possible deadlock due to allocating while"
814 " in jni critical section");
815 }
816 return NULL;
817 }
818 }
819
820 { // Need lock to get self consistent gc_count's
821 MutexLocker ml(Heap_lock);
822 gc_count = Universe::heap()->total_collections();
823 full_gc_count = Universe::heap()->total_full_collections();
824 }
825
826 // Generate a VM operation
827 VM_CollectForMetadataAllocation op(loader_data,
828 word_size,
829 mdtype,
830 gc_count,
831 full_gc_count,
832 GCCause::_metadata_GC_threshold);
833 VMThread::execute(&op);
834
835 // If GC was locked out, try again. Check
836 // before checking success because the prologue
837 // could have succeeded and the GC still have
838 // been locked out.
839 if (op.gc_locked()) {
840 continue;
841 }
842
843 if (op.prologue_succeeded()) {
844 return op.result();
845 }
846 loop_count++;
847 if ((QueuedAllocationWarningCount > 0) &&
848 (loop_count % QueuedAllocationWarningCount == 0)) {
849 warning("satisfy_failed_metadata_allocation() retries %d times \n\t"
850 " size=%d", loop_count, word_size);
851 }
852 } while (true); // Until a GC is done
853 }
854
855 // Return true if any of the following is true:
856 // . the allocation won't fit into the current young gen heap
857 // . gc locker is occupied (jni critical section)
858 // . heap memory is tight -- the most recent previous collection
859 // was a full collection because a partial collection (would
860 // have) failed and is likely to fail again
861 bool GenCollectorPolicy::should_try_older_generation_allocation(
862 size_t word_size) const {
863 GenCollectedHeap* gch = GenCollectedHeap::heap();
864 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();
865 return (word_size > heap_word_size(gen0_capacity))
866 || GC_locker::is_active_and_needs_gc()
867 || gch->incremental_collection_failed();
868 }
869
870
871 //
872 // MarkSweepPolicy methods
873 //
874
875 MarkSweepPolicy::MarkSweepPolicy() {
876 initialize_all();
877 }
878
879 void MarkSweepPolicy::initialize_generations() {
880 _generations = NEW_C_HEAP_ARRAY3(GenerationSpecPtr, number_of_generations(), mtGC, 0, AllocFailStrategy::RETURN_NULL);
881 if (_generations == NULL) {
882 vm_exit_during_initialization("Unable to allocate gen spec");
883 }
884
885 if (UseParNewGC) {
886 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);
887 } else {
888 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);
889 }
890 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);
891
892 if (_generations[0] == NULL || _generations[1] == NULL) {
893 vm_exit_during_initialization("Unable to allocate gen spec");
894 }
895 }
896
897 void MarkSweepPolicy::initialize_gc_policy_counters() {
898 // initialize the policy counters - 2 collectors, 3 generations
899 if (UseParNewGC) {
900 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);
901 } else {
902 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
903 }
904 }