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