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 if (MetaspaceSize > MaxMetaspaceSize) {
63 MaxMetaspaceSize = MetaspaceSize;
64 }
65 MetaspaceSize = MAX2(min_alignment(), align_size_down_(MetaspaceSize, min_alignment()));
66 // Don't increase Metaspace size limit above specified.
67 MaxMetaspaceSize = align_size_down(MaxMetaspaceSize, max_alignment());
68 if (MetaspaceSize > MaxMetaspaceSize) {
69 MetaspaceSize = MaxMetaspaceSize;
70 }
71
72 MinMetaspaceExpansion = MAX2(min_alignment(), align_size_down_(MinMetaspaceExpansion, min_alignment()));
73 MaxMetaspaceExpansion = MAX2(min_alignment(), align_size_down_(MaxMetaspaceExpansion, min_alignment()));
74
75 MinHeapDeltaBytes = align_size_up(MinHeapDeltaBytes, min_alignment());
76
77 assert(MetaspaceSize % min_alignment() == 0, "metapace alignment");
78 assert(MaxMetaspaceSize % max_alignment() == 0, "maximum metaspace alignment");
79 if (MetaspaceSize < 256*K) {
80 vm_exit_during_initialization("Too small initial Metaspace size");
81 }
82 }
83
84 void CollectorPolicy::initialize_size_info() {
85 // User inputs from -mx and ms must be aligned
86 set_min_heap_byte_size(align_size_up(Arguments::min_heap_size(), min_alignment()));
87 set_initial_heap_byte_size(align_size_up(InitialHeapSize, min_alignment()));
88 set_max_heap_byte_size(align_size_up(MaxHeapSize, max_alignment()));
89
90 // Check heap parameter properties
91 if (initial_heap_byte_size() < M) {
92 vm_exit_during_initialization("Too small initial heap");
93 }
94 // Check heap parameter properties
95 if (min_heap_byte_size() < M) {
96 vm_exit_during_initialization("Too small minimum heap");
97 }
98 if (initial_heap_byte_size() <= NewSize) {
99 // make sure there is at least some room in old space
100 vm_exit_during_initialization("Too small initial heap for new size specified");
101 }
102 if (max_heap_byte_size() < min_heap_byte_size()) {
103 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified");
104 }
105 if (initial_heap_byte_size() < min_heap_byte_size()) {
106 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified");
107 }
108 if (max_heap_byte_size() < initial_heap_byte_size()) {
109 vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
110 }
111
112 if (PrintGCDetails && Verbose) {
113 gclog_or_tty->print_cr("Minimum heap " SIZE_FORMAT " Initial heap "
114 SIZE_FORMAT " Maximum heap " SIZE_FORMAT,
115 min_heap_byte_size(), initial_heap_byte_size(), max_heap_byte_size());
116 }
117 }
118
119 bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) {
120 bool result = _should_clear_all_soft_refs;
121 set_should_clear_all_soft_refs(false);
122 return result;
123 }
124
125 GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap,
126 int max_covered_regions) {
127 switch (rem_set_name()) {
128 case GenRemSet::CardTable: {
129 CardTableRS* res = new CardTableRS(whole_heap, max_covered_regions);
130 return res;
131 }
132 default:
133 guarantee(false, "unrecognized GenRemSet::Name");
134 return NULL;
135 }
136 }
137
138 void CollectorPolicy::cleared_all_soft_refs() {
139 // If near gc overhear limit, continue to clear SoftRefs. SoftRefs may
140 // have been cleared in the last collection but if the gc overhear
141 // limit continues to be near, SoftRefs should still be cleared.
142 if (size_policy() != NULL) {
143 _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near();
144 }
145 _all_soft_refs_clear = true;
146 }
147
148 size_t CollectorPolicy::compute_max_alignment() {
149 // The card marking array and the offset arrays for old generations are
150 // committed in os pages as well. Make sure they are entirely full (to
151 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
152 // byte entry and the os page size is 4096, the maximum heap size should
153 // be 512*4096 = 2MB aligned.
154
155 // There is only the GenRemSet in Hotspot and only the GenRemSet::CardTable
156 // is supported.
157 // Requirements of any new remembered set implementations must be added here.
158 size_t alignment = GenRemSet::max_alignment_constraint(GenRemSet::CardTable);
159
160 // Parallel GC does its own alignment of the generations to avoid requiring a
161 // large page (256M on some platforms) for the permanent generation. The
162 // other collectors should also be updated to do their own alignment and then
163 // this use of lcm() should be removed.
164 if (UseLargePages && !UseParallelGC) {
165 // in presence of large pages we have to make sure that our
166 // alignment is large page aware
167 alignment = lcm(os::large_page_size(), alignment);
168 }
169
170 return alignment;
171 }
172
173 // GenCollectorPolicy methods.
174
175 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {
176 size_t x = base_size / (NewRatio+1);
177 size_t new_gen_size = x > min_alignment() ?
178 align_size_down(x, min_alignment()) :
179 min_alignment();
180 return new_gen_size;
181 }
182
183 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,
184 size_t maximum_size) {
185 size_t alignment = min_alignment();
186 size_t max_minus = maximum_size - alignment;
187 return desired_size < max_minus ? desired_size : max_minus;
188 }
189
190
191 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size,
192 size_t init_promo_size,
193 size_t init_survivor_size) {
194 const double max_gc_pause_sec = ((double) MaxGCPauseMillis)/1000.0;
195 _size_policy = new AdaptiveSizePolicy(init_eden_size,
196 init_promo_size,
197 init_survivor_size,
198 max_gc_pause_sec,
199 GCTimeRatio);
200 }
201
202 void GenCollectorPolicy::initialize_flags() {
203 // All sizes must be multiples of the generation granularity.
204 set_min_alignment((uintx) Generation::GenGrain);
205 set_max_alignment(compute_max_alignment());
206
207 CollectorPolicy::initialize_flags();
208
209 // All generational heaps have a youngest gen; handle those flags here.
210
211 // Adjust max size parameters
212 if (NewSize > MaxNewSize) {
213 MaxNewSize = NewSize;
214 }
215 NewSize = align_size_down(NewSize, min_alignment());
216 MaxNewSize = align_size_down(MaxNewSize, min_alignment());
217
218 // Check validity of heap flags
219 assert(NewSize % min_alignment() == 0, "eden space alignment");
220 assert(MaxNewSize % min_alignment() == 0, "survivor space alignment");
221
222 if (NewSize < 3*min_alignment()) {
223 // make sure there room for eden and two survivor spaces
224 vm_exit_during_initialization("Too small new size specified");
225 }
226 if (SurvivorRatio < 1 || NewRatio < 1) {
227 vm_exit_during_initialization("Invalid heap ratio specified");
228 }
229 }
230
231 void TwoGenerationCollectorPolicy::initialize_flags() {
232 GenCollectorPolicy::initialize_flags();
233
234 OldSize = align_size_down(OldSize, min_alignment());
235
236 if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(NewSize)) {
237 // NewRatio will be used later to set the young generation size so we use
238 // it to calculate how big the heap should be based on the requested OldSize
239 // and NewRatio.
240 assert(NewRatio > 0, "NewRatio should have been set up earlier");
241 size_t calculated_heapsize = (OldSize / NewRatio) * (NewRatio + 1);
242
243 calculated_heapsize = align_size_up(calculated_heapsize, max_alignment());
244 MaxHeapSize = calculated_heapsize;
245 InitialHeapSize = calculated_heapsize;
246 }
247 MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
248
249 // adjust max heap size if necessary
250 if (NewSize + OldSize > MaxHeapSize) {
251 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
252 // somebody set a maximum heap size with the intention that we should not
253 // exceed it. Adjust New/OldSize as necessary.
254 uintx calculated_size = NewSize + OldSize;
255 double shrink_factor = (double) MaxHeapSize / calculated_size;
256 // align
257 NewSize = align_size_down((uintx) (NewSize * shrink_factor), min_alignment());
258 // OldSize is already aligned because above we aligned MaxHeapSize to
259 // max_alignment(), and we just made sure that NewSize is aligned to
260 // min_alignment(). In initialize_flags() we verified that max_alignment()
261 // is a multiple of min_alignment().
262 OldSize = MaxHeapSize - NewSize;
263 } else {
264 MaxHeapSize = NewSize + OldSize;
265 }
266 }
267 // need to do this again
268 MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
269
270 // adjust max heap size if necessary
271 if (NewSize + OldSize > MaxHeapSize) {
272 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
273 // somebody set a maximum heap size with the intention that we should not
274 // exceed it. Adjust New/OldSize as necessary.
275 uintx calculated_size = NewSize + OldSize;
276 double shrink_factor = (double) MaxHeapSize / calculated_size;
277 // align
278 NewSize = align_size_down((uintx) (NewSize * shrink_factor), min_alignment());
279 // OldSize is already aligned because above we aligned MaxHeapSize to
280 // max_alignment(), and we just made sure that NewSize is aligned to
281 // min_alignment(). In initialize_flags() we verified that max_alignment()
282 // is a multiple of min_alignment().
283 OldSize = MaxHeapSize - NewSize;
284 } else {
285 MaxHeapSize = NewSize + OldSize;
286 }
287 }
288 // need to do this again
289 MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
290
291 always_do_update_barrier = UseConcMarkSweepGC;
292
293 // Check validity of heap flags
294 assert(OldSize % min_alignment() == 0, "old space alignment");
295 assert(MaxHeapSize % max_alignment() == 0, "maximum heap alignment");
296 }
297
298 // Values set on the command line win over any ergonomically
299 // set command line parameters.
300 // Ergonomic choice of parameters are done before this
301 // method is called. Values for command line parameters such as NewSize
302 // and MaxNewSize feed those ergonomic choices into this method.
303 // This method makes the final generation sizings consistent with
304 // themselves and with overall heap sizings.
305 // In the absence of explicitly set command line flags, policies
306 // such as the use of NewRatio are used to size the generation.
307 void GenCollectorPolicy::initialize_size_info() {
308 CollectorPolicy::initialize_size_info();
309
310 // min_alignment() is used for alignment within a generation.
311 // There is additional alignment done down stream for some
312 // collectors that sometimes causes unwanted rounding up of
313 // generations sizes.
314
315 // Determine maximum size of gen0
316
317 size_t max_new_size = 0;
318 if (FLAG_IS_CMDLINE(MaxNewSize) || FLAG_IS_ERGO(MaxNewSize)) {
319 if (MaxNewSize < min_alignment()) {
320 max_new_size = min_alignment();
321 }
322 if (MaxNewSize >= max_heap_byte_size()) {
323 max_new_size = align_size_down(max_heap_byte_size() - min_alignment(),
324 min_alignment());
325 warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or "
326 "greater than the entire heap (" SIZE_FORMAT "k). A "
327 "new generation size of " SIZE_FORMAT "k will be used.",
328 MaxNewSize/K, max_heap_byte_size()/K, max_new_size/K);
329 } else {
330 max_new_size = align_size_down(MaxNewSize, min_alignment());
331 }
332
333 // The case for FLAG_IS_ERGO(MaxNewSize) could be treated
334 // specially at this point to just use an ergonomically set
335 // MaxNewSize to set max_new_size. For cases with small
336 // heaps such a policy often did not work because the MaxNewSize
337 // was larger than the entire heap. The interpretation given
338 // to ergonomically set flags is that the flags are set
339 // by different collectors for their own special needs but
340 // are not allowed to badly shape the heap. This allows the
341 // different collectors to decide what's best for themselves
342 // without having to factor in the overall heap shape. It
343 // can be the case in the future that the collectors would
344 // only make "wise" ergonomics choices and this policy could
345 // just accept those choices. The choices currently made are
346 // not always "wise".
347 } else {
348 max_new_size = scale_by_NewRatio_aligned(max_heap_byte_size());
349 // Bound the maximum size by NewSize below (since it historically
350 // would have been NewSize and because the NewRatio calculation could
351 // yield a size that is too small) and bound it by MaxNewSize above.
352 // Ergonomics plays here by previously calculating the desired
353 // NewSize and MaxNewSize.
354 max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize);
355 }
356 assert(max_new_size > 0, "All paths should set max_new_size");
357
358 // Given the maximum gen0 size, determine the initial and
359 // minimum gen0 sizes.
360
361 if (max_heap_byte_size() == min_heap_byte_size()) {
362 // The maximum and minimum heap sizes are the same so
363 // the generations minimum and initial must be the
364 // same as its maximum.
365 set_min_gen0_size(max_new_size);
366 set_initial_gen0_size(max_new_size);
367 set_max_gen0_size(max_new_size);
368 } else {
369 size_t desired_new_size = 0;
370 if (!FLAG_IS_DEFAULT(NewSize)) {
371 // If NewSize is set ergonomically (for example by cms), it
372 // would make sense to use it. If it is used, also use it
373 // to set the initial size. Although there is no reason
374 // the minimum size and the initial size have to be the same,
375 // the current implementation gets into trouble during the calculation
376 // of the tenured generation sizes if they are different.
377 // Note that this makes the initial size and the minimum size
378 // generally small compared to the NewRatio calculation.
379 _min_gen0_size = NewSize;
380 desired_new_size = NewSize;
381 max_new_size = MAX2(max_new_size, NewSize);
382 } else {
383 // For the case where NewSize is the default, use NewRatio
384 // to size the minimum and initial generation sizes.
385 // Use the default NewSize as the floor for these values. If
386 // NewRatio is overly large, the resulting sizes can be too
387 // small.
388 _min_gen0_size = MAX2(scale_by_NewRatio_aligned(min_heap_byte_size()),
389 NewSize);
390 desired_new_size =
391 MAX2(scale_by_NewRatio_aligned(initial_heap_byte_size()),
392 NewSize);
393 }
394
395 assert(_min_gen0_size > 0, "Sanity check");
396 set_initial_gen0_size(desired_new_size);
397 set_max_gen0_size(max_new_size);
398
399 // At this point the desirable initial and minimum sizes have been
400 // determined without regard to the maximum sizes.
401
402 // Bound the sizes by the corresponding overall heap sizes.
403 set_min_gen0_size(
404 bound_minus_alignment(_min_gen0_size, min_heap_byte_size()));
405 set_initial_gen0_size(
406 bound_minus_alignment(_initial_gen0_size, initial_heap_byte_size()));
407 set_max_gen0_size(
408 bound_minus_alignment(_max_gen0_size, max_heap_byte_size()));
409
410 // At this point all three sizes have been checked against the
411 // maximum sizes but have not been checked for consistency
412 // among the three.
413
414 // Final check min <= initial <= max
415 set_min_gen0_size(MIN2(_min_gen0_size, _max_gen0_size));
416 set_initial_gen0_size(
417 MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size));
418 set_min_gen0_size(MIN2(_min_gen0_size, _initial_gen0_size));
419 }
420
421 if (PrintGCDetails && Verbose) {
422 gclog_or_tty->print_cr("1: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
423 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
424 min_gen0_size(), initial_gen0_size(), max_gen0_size());
425 }
426 }
427
428 // Call this method during the sizing of the gen1 to make
429 // adjustments to gen0 because of gen1 sizing policy. gen0 initially has
430 // the most freedom in sizing because it is done before the
431 // policy for gen1 is applied. Once gen1 policies have been applied,
432 // there may be conflicts in the shape of the heap and this method
433 // is used to make the needed adjustments. The application of the
434 // policies could be more sophisticated (iterative for example) but
435 // keeping it simple also seems a worthwhile goal.
436 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr,
437 size_t* gen1_size_ptr,
438 const size_t heap_size,
439 const size_t min_gen1_size) {
440 bool result = false;
441
442 if ((*gen1_size_ptr + *gen0_size_ptr) > heap_size) {
443 if ((heap_size < (*gen0_size_ptr + min_gen1_size)) &&
444 (heap_size >= min_gen1_size + min_alignment())) {
445 // Adjust gen0 down to accommodate min_gen1_size
446 *gen0_size_ptr = heap_size - min_gen1_size;
447 *gen0_size_ptr =
448 MAX2((uintx)align_size_down(*gen0_size_ptr, min_alignment()),
449 min_alignment());
450 assert(*gen0_size_ptr > 0, "Min gen0 is too large");
451 result = true;
452 } else {
453 *gen1_size_ptr = heap_size - *gen0_size_ptr;
454 *gen1_size_ptr =
455 MAX2((uintx)align_size_down(*gen1_size_ptr, min_alignment()),
456 min_alignment());
457 }
458 }
459 return result;
460 }
461
462 // Minimum sizes of the generations may be different than
463 // the initial sizes. An inconsistently is permitted here
464 // in the total size that can be specified explicitly by
465 // command line specification of OldSize and NewSize and
466 // also a command line specification of -Xms. Issue a warning
467 // but allow the values to pass.
468
469 void TwoGenerationCollectorPolicy::initialize_size_info() {
470 GenCollectorPolicy::initialize_size_info();
471
472 // At this point the minimum, initial and maximum sizes
473 // of the overall heap and of gen0 have been determined.
474 // The maximum gen1 size can be determined from the maximum gen0
475 // and maximum heap size since no explicit flags exits
476 // for setting the gen1 maximum.
477 _max_gen1_size = max_heap_byte_size() - _max_gen0_size;
478 _max_gen1_size =
479 MAX2((uintx)align_size_down(_max_gen1_size, min_alignment()),
480 min_alignment());
481 // If no explicit command line flag has been set for the
482 // gen1 size, use what is left for gen1.
483 if (FLAG_IS_DEFAULT(OldSize) || FLAG_IS_ERGO(OldSize)) {
484 // The user has not specified any value or ergonomics
485 // has chosen a value (which may or may not be consistent
486 // with the overall heap size). In either case make
487 // the minimum, maximum and initial sizes consistent
488 // with the gen0 sizes and the overall heap sizes.
489 assert(min_heap_byte_size() > _min_gen0_size,
490 "gen0 has an unexpected minimum size");
491 set_min_gen1_size(min_heap_byte_size() - min_gen0_size());
492 set_min_gen1_size(
493 MAX2((uintx)align_size_down(_min_gen1_size, min_alignment()),
494 min_alignment()));
495 set_initial_gen1_size(initial_heap_byte_size() - initial_gen0_size());
496 set_initial_gen1_size(
497 MAX2((uintx)align_size_down(_initial_gen1_size, min_alignment()),
498 min_alignment()));
499
500 } else {
501 // It's been explicitly set on the command line. Use the
502 // OldSize and then determine the consequences.
503 set_min_gen1_size(OldSize);
504 set_initial_gen1_size(OldSize);
505
506 // If the user has explicitly set an OldSize that is inconsistent
507 // with other command line flags, issue a warning.
508 // The generation minimums and the overall heap mimimum should
509 // be within one heap alignment.
510 if ((_min_gen1_size + _min_gen0_size + min_alignment()) <
511 min_heap_byte_size()) {
512 warning("Inconsistency between minimum heap size and minimum "
513 "generation sizes: using minimum heap = " SIZE_FORMAT,
514 min_heap_byte_size());
515 }
516 if ((OldSize > _max_gen1_size)) {
517 warning("Inconsistency between maximum heap size and maximum "
518 "generation sizes: using maximum heap = " SIZE_FORMAT
519 " -XX:OldSize flag is being ignored",
520 max_heap_byte_size());
521 }
522 // If there is an inconsistency between the OldSize and the minimum and/or
523 // initial size of gen0, since OldSize was explicitly set, OldSize wins.
524 if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size,
525 min_heap_byte_size(), OldSize)) {
526 if (PrintGCDetails && Verbose) {
527 gclog_or_tty->print_cr("2: 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 // Initial size
533 if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,
534 initial_heap_byte_size(), OldSize)) {
535 if (PrintGCDetails && Verbose) {
536 gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
537 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
538 min_gen0_size(), initial_gen0_size(), max_gen0_size());
539 }
540 }
541 }
542 // Enforce the maximum gen1 size.
543 set_min_gen1_size(MIN2(_min_gen1_size, _max_gen1_size));
544
545 // Check that min gen1 <= initial gen1 <= max gen1
546 set_initial_gen1_size(MAX2(_initial_gen1_size, _min_gen1_size));
547 set_initial_gen1_size(MIN2(_initial_gen1_size, _max_gen1_size));
548
549 if (PrintGCDetails && Verbose) {
550 gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 "
551 SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT,
552 min_gen1_size(), initial_gen1_size(), max_gen1_size());
553 }
554 }
555
556 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
557 bool is_tlab,
558 bool* gc_overhead_limit_was_exceeded) {
559 GenCollectedHeap *gch = GenCollectedHeap::heap();
560
561 debug_only(gch->check_for_valid_allocation_state());
562 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
563
564 // In general gc_overhead_limit_was_exceeded should be false so
565 // set it so here and reset it to true only if the gc time
566 // limit is being exceeded as checked below.
567 *gc_overhead_limit_was_exceeded = false;
568
569 HeapWord* result = NULL;
570
571 // Loop until the allocation is satisified,
572 // or unsatisfied after GC.
573 for (int try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) {
574 HandleMark hm; // discard any handles allocated in each iteration
575
576 // First allocation attempt is lock-free.
577 Generation *gen0 = gch->get_gen(0);
578 assert(gen0->supports_inline_contig_alloc(),
579 "Otherwise, must do alloc within heap lock");
580 if (gen0->should_allocate(size, is_tlab)) {
581 result = gen0->par_allocate(size, is_tlab);
582 if (result != NULL) {
583 assert(gch->is_in_reserved(result), "result not in heap");
584 return result;
585 }
586 }
587 unsigned int gc_count_before; // read inside the Heap_lock locked region
588 {
589 MutexLocker ml(Heap_lock);
590 if (PrintGC && Verbose) {
591 gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:"
592 " attempting locked slow path allocation");
593 }
594 // Note that only large objects get a shot at being
595 // allocated in later generations.
596 bool first_only = ! should_try_older_generation_allocation(size);
597
598 result = gch->attempt_allocation(size, is_tlab, first_only);
599 if (result != NULL) {
600 assert(gch->is_in_reserved(result), "result not in heap");
601 return result;
602 }
603
604 if (GC_locker::is_active_and_needs_gc()) {
605 if (is_tlab) {
606 return NULL; // Caller will retry allocating individual object
607 }
608 if (!gch->is_maximal_no_gc()) {
609 // Try and expand heap to satisfy request
610 result = expand_heap_and_allocate(size, is_tlab);
611 // result could be null if we are out of space
612 if (result != NULL) {
613 return result;
614 }
615 }
616
617 if (gclocker_stalled_count > GCLockerRetryAllocationCount) {
618 return NULL; // we didn't get to do a GC and we didn't get any memory
619 }
620
621 // If this thread is not in a jni critical section, we stall
622 // the requestor until the critical section has cleared and
623 // GC allowed. When the critical section clears, a GC is
624 // initiated by the last thread exiting the critical section; so
625 // we retry the allocation sequence from the beginning of the loop,
626 // rather than causing more, now probably unnecessary, GC attempts.
627 JavaThread* jthr = JavaThread::current();
628 if (!jthr->in_critical()) {
629 MutexUnlocker mul(Heap_lock);
630 // Wait for JNI critical section to be exited
631 GC_locker::stall_until_clear();
632 gclocker_stalled_count += 1;
633 continue;
634 } else {
635 if (CheckJNICalls) {
636 fatal("Possible deadlock due to allocating while"
637 " in jni critical section");
638 }
639 return NULL;
640 }
641 }
642
643 // Read the gc count while the heap lock is held.
644 gc_count_before = Universe::heap()->total_collections();
645 }
646
647 VM_GenCollectForAllocation op(size,
648 is_tlab,
649 gc_count_before);
650 VMThread::execute(&op);
651 if (op.prologue_succeeded()) {
652 result = op.result();
653 if (op.gc_locked()) {
654 assert(result == NULL, "must be NULL if gc_locked() is true");
655 continue; // retry and/or stall as necessary
656 }
657
658 // Allocation has failed and a collection
659 // has been done. If the gc time limit was exceeded the
660 // this time, return NULL so that an out-of-memory
661 // will be thrown. Clear gc_overhead_limit_exceeded
662 // so that the overhead exceeded does not persist.
663
664 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
665 const bool softrefs_clear = all_soft_refs_clear();
666
667 if (limit_exceeded && softrefs_clear) {
668 *gc_overhead_limit_was_exceeded = true;
669 size_policy()->set_gc_overhead_limit_exceeded(false);
670 if (op.result() != NULL) {
671 CollectedHeap::fill_with_object(op.result(), size);
672 }
673 return NULL;
674 }
675 assert(result == NULL || gch->is_in_reserved(result),
676 "result not in heap");
677 return result;
678 }
679
680 // Give a warning if we seem to be looping forever.
681 if ((QueuedAllocationWarningCount > 0) &&
682 (try_count % QueuedAllocationWarningCount == 0)) {
683 warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t"
684 " size=%d %s", try_count, size, is_tlab ? "(TLAB)" : "");
685 }
686 }
687 }
688
689 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size,
690 bool is_tlab) {
691 GenCollectedHeap *gch = GenCollectedHeap::heap();
692 HeapWord* result = NULL;
693 for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) {
694 Generation *gen = gch->get_gen(i);
695 if (gen->should_allocate(size, is_tlab)) {
696 result = gen->expand_and_allocate(size, is_tlab);
697 }
698 }
699 assert(result == NULL || gch->is_in_reserved(result), "result not in heap");
700 return result;
701 }
702
703 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size,
704 bool is_tlab) {
705 GenCollectedHeap *gch = GenCollectedHeap::heap();
706 GCCauseSetter x(gch, GCCause::_allocation_failure);
707 HeapWord* result = NULL;
708
709 assert(size != 0, "Precondition violated");
710 if (GC_locker::is_active_and_needs_gc()) {
711 // GC locker is active; instead of a collection we will attempt
712 // to expand the heap, if there's room for expansion.
713 if (!gch->is_maximal_no_gc()) {
714 result = expand_heap_and_allocate(size, is_tlab);
715 }
716 return result; // could be null if we are out of space
717 } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) {
718 // Do an incremental collection.
719 gch->do_collection(false /* full */,
720 false /* clear_all_soft_refs */,
721 size /* size */,
722 is_tlab /* is_tlab */,
723 number_of_generations() - 1 /* max_level */);
724 } else {
725 if (Verbose && PrintGCDetails) {
726 gclog_or_tty->print(" :: Trying full because partial may fail :: ");
727 }
728 // Try a full collection; see delta for bug id 6266275
729 // for the original code and why this has been simplified
730 // with from-space allocation criteria modified and
731 // such allocation moved out of the safepoint path.
732 gch->do_collection(true /* full */,
733 false /* clear_all_soft_refs */,
734 size /* size */,
735 is_tlab /* is_tlab */,
736 number_of_generations() - 1 /* max_level */);
737 }
738
739 result = gch->attempt_allocation(size, is_tlab, false /*first_only*/);
740
741 if (result != NULL) {
742 assert(gch->is_in_reserved(result), "result not in heap");
743 return result;
744 }
745
746 // OK, collection failed, try expansion.
747 result = expand_heap_and_allocate(size, is_tlab);
748 if (result != NULL) {
749 return result;
750 }
751
752 // If we reach this point, we're really out of memory. Try every trick
753 // we can to reclaim memory. Force collection of soft references. Force
754 // a complete compaction of the heap. Any additional methods for finding
755 // free memory should be here, especially if they are expensive. If this
756 // attempt fails, an OOM exception will be thrown.
757 {
758 UIntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
759
760 gch->do_collection(true /* full */,
761 true /* clear_all_soft_refs */,
762 size /* size */,
763 is_tlab /* is_tlab */,
764 number_of_generations() - 1 /* max_level */);
765 }
766
767 result = gch->attempt_allocation(size, is_tlab, false /* first_only */);
768 if (result != NULL) {
769 assert(gch->is_in_reserved(result), "result not in heap");
770 return result;
771 }
772
773 assert(!should_clear_all_soft_refs(),
774 "Flag should have been handled and cleared prior to this point");
775
776 // What else? We might try synchronous finalization later. If the total
777 // space available is large enough for the allocation, then a more
778 // complete compaction phase than we've tried so far might be
779 // appropriate.
780 return NULL;
781 }
782
783 MetaWord* CollectorPolicy::satisfy_failed_metadata_allocation(
784 ClassLoaderData* loader_data,
785 size_t word_size,
786 Metaspace::MetadataType mdtype) {
787 uint loop_count = 0;
788 uint gc_count = 0;
789 uint full_gc_count = 0;
790
791 assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock");
792
793 do {
794 MetaWord* result = NULL;
795 if (GC_locker::is_active_and_needs_gc()) {
796 // If the GC_locker is active, just expand and allocate.
797 // If that does not succeed, wait if this thread is not
798 // in a critical section itself.
799 result =
800 loader_data->metaspace_non_null()->expand_and_allocate(word_size,
801 mdtype);
802 if (result != NULL) {
803 return result;
804 }
805 JavaThread* jthr = JavaThread::current();
806 if (!jthr->in_critical()) {
807 // Wait for JNI critical section to be exited
808 GC_locker::stall_until_clear();
809 // The GC invoked by the last thread leaving the critical
810 // section will be a young collection and a full collection
811 // is (currently) needed for unloading classes so continue
812 // to the next iteration to get a full GC.
813 continue;
814 } else {
815 if (CheckJNICalls) {
816 fatal("Possible deadlock due to allocating while"
817 " in jni critical section");
818 }
819 return NULL;
820 }
821 }
822
823 { // Need lock to get self consistent gc_count's
824 MutexLocker ml(Heap_lock);
825 gc_count = Universe::heap()->total_collections();
826 full_gc_count = Universe::heap()->total_full_collections();
827 }
828
829 // Generate a VM operation
830 VM_CollectForMetadataAllocation op(loader_data,
831 word_size,
832 mdtype,
833 gc_count,
834 full_gc_count,
835 GCCause::_metadata_GC_threshold);
836 VMThread::execute(&op);
837
838 // If GC was locked out, try again. Check
839 // before checking success because the prologue
840 // could have succeeded and the GC still have
841 // been locked out.
842 if (op.gc_locked()) {
843 continue;
844 }
845
846 if (op.prologue_succeeded()) {
847 return op.result();
848 }
849 loop_count++;
850 if ((QueuedAllocationWarningCount > 0) &&
851 (loop_count % QueuedAllocationWarningCount == 0)) {
852 warning("satisfy_failed_metadata_allocation() retries %d times \n\t"
853 " size=%d", loop_count, word_size);
854 }
855 } while (true); // Until a GC is done
856 }
857
858 // Return true if any of the following is true:
859 // . the allocation won't fit into the current young gen heap
860 // . gc locker is occupied (jni critical section)
861 // . heap memory is tight -- the most recent previous collection
862 // was a full collection because a partial collection (would
863 // have) failed and is likely to fail again
864 bool GenCollectorPolicy::should_try_older_generation_allocation(
865 size_t word_size) const {
866 GenCollectedHeap* gch = GenCollectedHeap::heap();
867 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();
868 return (word_size > heap_word_size(gen0_capacity))
869 || GC_locker::is_active_and_needs_gc()
870 || gch->incremental_collection_failed();
871 }
872
873
874 //
875 // MarkSweepPolicy methods
876 //
877
878 MarkSweepPolicy::MarkSweepPolicy() {
879 initialize_all();
880 }
881
882 void MarkSweepPolicy::initialize_generations() {
883 _generations = NEW_C_HEAP_ARRAY3(GenerationSpecPtr, number_of_generations(), mtGC, 0, AllocFailStrategy::RETURN_NULL);
884 if (_generations == NULL)
885 vm_exit_during_initialization("Unable to allocate gen spec");
886
887 if (UseParNewGC) {
888 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);
889 } else {
890 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);
891 }
892 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);
893
894 if (_generations[0] == NULL || _generations[1] == NULL)
895 vm_exit_during_initialization("Unable to allocate gen spec");
896 }
897
898 void MarkSweepPolicy::initialize_gc_policy_counters() {
899 // initialize the policy counters - 2 collectors, 3 generations
900 if (UseParNewGC) {
901 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);
902 } else {
903 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
904 }
905 }