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 MaxMetaspaceSize = restricted_align_down(MaxMetaspaceSize, max_alignment());
69 }
70
71 if (MetaspaceSize > MaxMetaspaceSize) {
72 FLAG_SET_ERGO(uintx, MetaspaceSize, MaxMetaspaceSize);
73 }
74
75 if (!is_size_aligned(MetaspaceSize, min_alignment())) {
76 FLAG_SET_ERGO(uintx, MetaspaceSize,
77 restricted_align_down(MetaspaceSize, min_alignment()));
78 }
79
80 assert(MetaspaceSize <= MaxMetaspaceSize, "Must be");
81
82 MinMetaspaceExpansion = restricted_align_down(MinMetaspaceExpansion, min_alignment());
83 MaxMetaspaceExpansion = restricted_align_down(MaxMetaspaceExpansion, min_alignment());
84
85 MinHeapDeltaBytes = align_size_up(MinHeapDeltaBytes, min_alignment());
86
87 assert(MetaspaceSize % min_alignment() == 0, "metapace alignment");
88 assert(MaxMetaspaceSize % max_alignment() == 0, "maximum metaspace alignment");
89 if (MetaspaceSize < 256*K) {
90 vm_exit_during_initialization("Too small initial Metaspace size");
91 }
92 }
93
94 void CollectorPolicy::initialize_size_info() {
95 // User inputs from -mx and ms must be aligned
96 set_min_heap_byte_size(align_size_up(Arguments::min_heap_size(), min_alignment()));
97 set_initial_heap_byte_size(align_size_up(InitialHeapSize, min_alignment()));
98 set_max_heap_byte_size(align_size_up(MaxHeapSize, max_alignment()));
99
100 // Check heap parameter properties
101 if (initial_heap_byte_size() < M) {
102 vm_exit_during_initialization("Too small initial heap");
103 }
104 // Check heap parameter properties
105 if (min_heap_byte_size() < M) {
106 vm_exit_during_initialization("Too small minimum heap");
107 }
108 if (initial_heap_byte_size() <= NewSize) {
109 // make sure there is at least some room in old space
110 vm_exit_during_initialization("Too small initial heap for new size specified");
111 }
112 if (max_heap_byte_size() < min_heap_byte_size()) {
113 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified");
114 }
115 if (initial_heap_byte_size() < min_heap_byte_size()) {
116 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified");
117 }
118 if (max_heap_byte_size() < initial_heap_byte_size()) {
119 vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
120 }
121
122 if (PrintGCDetails && Verbose) {
123 gclog_or_tty->print_cr("Minimum heap " SIZE_FORMAT " Initial heap "
124 SIZE_FORMAT " Maximum heap " SIZE_FORMAT,
125 min_heap_byte_size(), initial_heap_byte_size(), max_heap_byte_size());
126 }
127 }
128
129 bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) {
130 bool result = _should_clear_all_soft_refs;
131 set_should_clear_all_soft_refs(false);
132 return result;
133 }
134
135 GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap,
136 int max_covered_regions) {
137 switch (rem_set_name()) {
138 case GenRemSet::CardTable: {
139 CardTableRS* res = new CardTableRS(whole_heap, max_covered_regions);
140 return res;
141 }
142 default:
143 guarantee(false, "unrecognized GenRemSet::Name");
144 return NULL;
145 }
146 }
147
148 void CollectorPolicy::cleared_all_soft_refs() {
149 // If near gc overhear limit, continue to clear SoftRefs. SoftRefs may
150 // have been cleared in the last collection but if the gc overhear
151 // limit continues to be near, SoftRefs should still be cleared.
152 if (size_policy() != NULL) {
153 _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near();
154 }
155 _all_soft_refs_clear = true;
156 }
157
158 size_t CollectorPolicy::compute_max_alignment() {
159 // The card marking array and the offset arrays for old generations are
160 // committed in os pages as well. Make sure they are entirely full (to
161 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
162 // byte entry and the os page size is 4096, the maximum heap size should
163 // be 512*4096 = 2MB aligned.
164
165 // There is only the GenRemSet in Hotspot and only the GenRemSet::CardTable
166 // is supported.
167 // Requirements of any new remembered set implementations must be added here.
168 size_t alignment = GenRemSet::max_alignment_constraint(GenRemSet::CardTable);
169
170 // Parallel GC does its own alignment of the generations to avoid requiring a
171 // large page (256M on some platforms) for the permanent generation. The
172 // other collectors should also be updated to do their own alignment and then
173 // this use of lcm() should be removed.
174 if (UseLargePages && !UseParallelGC) {
175 // in presence of large pages we have to make sure that our
176 // alignment is large page aware
177 alignment = lcm(os::large_page_size(), alignment);
178 }
179
180 return alignment;
181 }
182
183 // GenCollectorPolicy methods.
184
185 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {
186 size_t x = base_size / (NewRatio+1);
187 size_t new_gen_size = x > min_alignment() ?
188 align_size_down(x, min_alignment()) :
189 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 set_min_alignment((uintx) Generation::GenGrain);
215 set_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 heap 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 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 set_min_gen0_size(max_new_size);
376 set_initial_gen0_size(max_new_size);
377 set_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()),
399 NewSize);
400 desired_new_size =
401 MAX2(scale_by_NewRatio_aligned(initial_heap_byte_size()),
402 NewSize);
403 }
404
405 assert(_min_gen0_size > 0, "Sanity check");
406 set_initial_gen0_size(desired_new_size);
407 set_max_gen0_size(max_new_size);
408
409 // At this point the desirable initial and minimum sizes have been
410 // determined without regard to the maximum sizes.
411
412 // Bound the sizes by the corresponding overall heap sizes.
413 set_min_gen0_size(
414 bound_minus_alignment(_min_gen0_size, min_heap_byte_size()));
415 set_initial_gen0_size(
416 bound_minus_alignment(_initial_gen0_size, initial_heap_byte_size()));
417 set_max_gen0_size(
418 bound_minus_alignment(_max_gen0_size, max_heap_byte_size()));
419
420 // At this point all three sizes have been checked against the
421 // maximum sizes but have not been checked for consistency
422 // among the three.
423
424 // Final check min <= initial <= max
425 set_min_gen0_size(MIN2(_min_gen0_size, _max_gen0_size));
426 set_initial_gen0_size(
427 MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size));
428 set_min_gen0_size(MIN2(_min_gen0_size, _initial_gen0_size));
429 }
430
431 if (PrintGCDetails && Verbose) {
432 gclog_or_tty->print_cr("1: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
433 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
434 min_gen0_size(), initial_gen0_size(), max_gen0_size());
435 }
436 }
437
438 // Call this method during the sizing of the gen1 to make
439 // adjustments to gen0 because of gen1 sizing policy. gen0 initially has
440 // the most freedom in sizing because it is done before the
441 // policy for gen1 is applied. Once gen1 policies have been applied,
442 // there may be conflicts in the shape of the heap and this method
443 // is used to make the needed adjustments. The application of the
444 // policies could be more sophisticated (iterative for example) but
445 // keeping it simple also seems a worthwhile goal.
446 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr,
447 size_t* gen1_size_ptr,
448 const size_t heap_size,
449 const size_t min_gen1_size) {
450 bool result = false;
451
452 if ((*gen1_size_ptr + *gen0_size_ptr) > heap_size) {
453 if ((heap_size < (*gen0_size_ptr + min_gen1_size)) &&
454 (heap_size >= min_gen1_size + min_alignment())) {
455 // Adjust gen0 down to accommodate min_gen1_size
456 *gen0_size_ptr = heap_size - min_gen1_size;
457 *gen0_size_ptr =
458 MAX2((uintx)align_size_down(*gen0_size_ptr, min_alignment()),
459 min_alignment());
460 assert(*gen0_size_ptr > 0, "Min gen0 is too large");
461 result = true;
462 } else {
463 *gen1_size_ptr = heap_size - *gen0_size_ptr;
464 *gen1_size_ptr =
465 MAX2((uintx)align_size_down(*gen1_size_ptr, min_alignment()),
466 min_alignment());
467 }
468 }
469 return result;
470 }
471
472 // Minimum sizes of the generations may be different than
473 // the initial sizes. An inconsistently is permitted here
474 // in the total size that can be specified explicitly by
475 // command line specification of OldSize and NewSize and
476 // also a command line specification of -Xms. Issue a warning
477 // but allow the values to pass.
478
479 void TwoGenerationCollectorPolicy::initialize_size_info() {
480 GenCollectorPolicy::initialize_size_info();
481
482 // At this point the minimum, initial and maximum sizes
483 // of the overall heap and of gen0 have been determined.
484 // The maximum gen1 size can be determined from the maximum gen0
485 // and maximum heap size since no explicit flags exits
486 // for setting the gen1 maximum.
487 _max_gen1_size = max_heap_byte_size() - _max_gen0_size;
488 _max_gen1_size =
489 MAX2((uintx)align_size_down(_max_gen1_size, min_alignment()),
490 min_alignment());
491 // If no explicit command line flag has been set for the
492 // gen1 size, use what is left for gen1.
493 if (FLAG_IS_DEFAULT(OldSize) || FLAG_IS_ERGO(OldSize)) {
494 // The user has not specified any value or ergonomics
495 // has chosen a value (which may or may not be consistent
496 // with the overall heap size). In either case make
497 // the minimum, maximum and initial sizes consistent
498 // with the gen0 sizes and the overall heap sizes.
499 assert(min_heap_byte_size() > _min_gen0_size,
500 "gen0 has an unexpected minimum size");
501 set_min_gen1_size(min_heap_byte_size() - min_gen0_size());
502 set_min_gen1_size(
503 MAX2((uintx)align_size_down(_min_gen1_size, min_alignment()),
504 min_alignment()));
505 set_initial_gen1_size(initial_heap_byte_size() - initial_gen0_size());
506 set_initial_gen1_size(
507 MAX2((uintx)align_size_down(_initial_gen1_size, min_alignment()),
508 min_alignment()));
509
510 } else {
511 // It's been explicitly set on the command line. Use the
512 // OldSize and then determine the consequences.
513 set_min_gen1_size(OldSize);
514 set_initial_gen1_size(OldSize);
515
516 // If the user has explicitly set an OldSize that is inconsistent
517 // with other command line flags, issue a warning.
518 // The generation minimums and the overall heap mimimum should
519 // be within one heap alignment.
520 if ((_min_gen1_size + _min_gen0_size + min_alignment()) <
521 min_heap_byte_size()) {
522 warning("Inconsistency between minimum heap size and minimum "
523 "generation sizes: using minimum heap = " SIZE_FORMAT,
524 min_heap_byte_size());
525 }
526 if ((OldSize > _max_gen1_size)) {
527 warning("Inconsistency between maximum heap size and maximum "
528 "generation sizes: using maximum heap = " SIZE_FORMAT
529 " -XX:OldSize flag is being ignored",
530 max_heap_byte_size());
531 }
532 // If there is an inconsistency between the OldSize and the minimum and/or
533 // initial size of gen0, since OldSize was explicitly set, OldSize wins.
534 if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size,
535 min_heap_byte_size(), OldSize)) {
536 if (PrintGCDetails && Verbose) {
537 gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
538 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
539 min_gen0_size(), initial_gen0_size(), max_gen0_size());
540 }
541 }
542 // Initial size
543 if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,
544 initial_heap_byte_size(), OldSize)) {
545 if (PrintGCDetails && Verbose) {
546 gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
547 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
548 min_gen0_size(), initial_gen0_size(), max_gen0_size());
549 }
550 }
551 }
552 // Enforce the maximum gen1 size.
553 set_min_gen1_size(MIN2(_min_gen1_size, _max_gen1_size));
554
555 // Check that min gen1 <= initial gen1 <= max gen1
556 set_initial_gen1_size(MAX2(_initial_gen1_size, _min_gen1_size));
557 set_initial_gen1_size(MIN2(_initial_gen1_size, _max_gen1_size));
558
559 if (PrintGCDetails && Verbose) {
560 gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 "
561 SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT,
562 min_gen1_size(), initial_gen1_size(), max_gen1_size());
563 }
564 }
565
566 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
567 bool is_tlab,
568 bool* gc_overhead_limit_was_exceeded) {
569 GenCollectedHeap *gch = GenCollectedHeap::heap();
570
571 debug_only(gch->check_for_valid_allocation_state());
572 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
573
574 // In general gc_overhead_limit_was_exceeded should be false so
575 // set it so here and reset it to true only if the gc time
576 // limit is being exceeded as checked below.
577 *gc_overhead_limit_was_exceeded = false;
578
579 HeapWord* result = NULL;
580
581 // Loop until the allocation is satisified,
582 // or unsatisfied after GC.
583 for (int try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) {
584 HandleMark hm; // discard any handles allocated in each iteration
585
586 // First allocation attempt is lock-free.
587 Generation *gen0 = gch->get_gen(0);
588 assert(gen0->supports_inline_contig_alloc(),
589 "Otherwise, must do alloc within heap lock");
590 if (gen0->should_allocate(size, is_tlab)) {
591 result = gen0->par_allocate(size, is_tlab);
592 if (result != NULL) {
593 assert(gch->is_in_reserved(result), "result not in heap");
594 return result;
595 }
596 }
597 unsigned int gc_count_before; // read inside the Heap_lock locked region
598 {
599 MutexLocker ml(Heap_lock);
600 if (PrintGC && Verbose) {
601 gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:"
602 " attempting locked slow path allocation");
603 }
604 // Note that only large objects get a shot at being
605 // allocated in later generations.
606 bool first_only = ! should_try_older_generation_allocation(size);
607
608 result = gch->attempt_allocation(size, is_tlab, first_only);
609 if (result != NULL) {
610 assert(gch->is_in_reserved(result), "result not in heap");
611 return result;
612 }
613
614 if (GC_locker::is_active_and_needs_gc()) {
615 if (is_tlab) {
616 return NULL; // Caller will retry allocating individual object
617 }
618 if (!gch->is_maximal_no_gc()) {
619 // Try and expand heap to satisfy request
620 result = expand_heap_and_allocate(size, is_tlab);
621 // result could be null if we are out of space
622 if (result != NULL) {
623 return result;
624 }
625 }
626
627 if (gclocker_stalled_count > GCLockerRetryAllocationCount) {
628 return NULL; // we didn't get to do a GC and we didn't get any memory
629 }
630
631 // If this thread is not in a jni critical section, we stall
632 // the requestor until the critical section has cleared and
633 // GC allowed. When the critical section clears, a GC is
634 // initiated by the last thread exiting the critical section; so
635 // we retry the allocation sequence from the beginning of the loop,
636 // rather than causing more, now probably unnecessary, GC attempts.
637 JavaThread* jthr = JavaThread::current();
638 if (!jthr->in_critical()) {
639 MutexUnlocker mul(Heap_lock);
640 // Wait for JNI critical section to be exited
641 GC_locker::stall_until_clear();
642 gclocker_stalled_count += 1;
643 continue;
644 } else {
645 if (CheckJNICalls) {
646 fatal("Possible deadlock due to allocating while"
647 " in jni critical section");
648 }
649 return NULL;
650 }
651 }
652
653 // Read the gc count while the heap lock is held.
654 gc_count_before = Universe::heap()->total_collections();
655 }
656
657 VM_GenCollectForAllocation op(size,
658 is_tlab,
659 gc_count_before);
660 VMThread::execute(&op);
661 if (op.prologue_succeeded()) {
662 result = op.result();
663 if (op.gc_locked()) {
664 assert(result == NULL, "must be NULL if gc_locked() is true");
665 continue; // retry and/or stall as necessary
666 }
667
668 // Allocation has failed and a collection
669 // has been done. If the gc time limit was exceeded the
670 // this time, return NULL so that an out-of-memory
671 // will be thrown. Clear gc_overhead_limit_exceeded
672 // so that the overhead exceeded does not persist.
673
674 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
675 const bool softrefs_clear = all_soft_refs_clear();
676
677 if (limit_exceeded && softrefs_clear) {
678 *gc_overhead_limit_was_exceeded = true;
679 size_policy()->set_gc_overhead_limit_exceeded(false);
680 if (op.result() != NULL) {
681 CollectedHeap::fill_with_object(op.result(), size);
682 }
683 return NULL;
684 }
685 assert(result == NULL || gch->is_in_reserved(result),
686 "result not in heap");
687 return result;
688 }
689
690 // Give a warning if we seem to be looping forever.
691 if ((QueuedAllocationWarningCount > 0) &&
692 (try_count % QueuedAllocationWarningCount == 0)) {
693 warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t"
694 " size=%d %s", try_count, size, is_tlab ? "(TLAB)" : "");
695 }
696 }
697 }
698
699 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size,
700 bool is_tlab) {
701 GenCollectedHeap *gch = GenCollectedHeap::heap();
702 HeapWord* result = NULL;
703 for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) {
704 Generation *gen = gch->get_gen(i);
705 if (gen->should_allocate(size, is_tlab)) {
706 result = gen->expand_and_allocate(size, is_tlab);
707 }
708 }
709 assert(result == NULL || gch->is_in_reserved(result), "result not in heap");
710 return result;
711 }
712
713 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size,
714 bool is_tlab) {
715 GenCollectedHeap *gch = GenCollectedHeap::heap();
716 GCCauseSetter x(gch, GCCause::_allocation_failure);
717 HeapWord* result = NULL;
718
719 assert(size != 0, "Precondition violated");
720 if (GC_locker::is_active_and_needs_gc()) {
721 // GC locker is active; instead of a collection we will attempt
722 // to expand the heap, if there's room for expansion.
723 if (!gch->is_maximal_no_gc()) {
724 result = expand_heap_and_allocate(size, is_tlab);
725 }
726 return result; // could be null if we are out of space
727 } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) {
728 // Do an incremental collection.
729 gch->do_collection(false /* full */,
730 false /* clear_all_soft_refs */,
731 size /* size */,
732 is_tlab /* is_tlab */,
733 number_of_generations() - 1 /* max_level */);
734 } else {
735 if (Verbose && PrintGCDetails) {
736 gclog_or_tty->print(" :: Trying full because partial may fail :: ");
737 }
738 // Try a full collection; see delta for bug id 6266275
739 // for the original code and why this has been simplified
740 // with from-space allocation criteria modified and
741 // such allocation moved out of the safepoint path.
742 gch->do_collection(true /* full */,
743 false /* clear_all_soft_refs */,
744 size /* size */,
745 is_tlab /* is_tlab */,
746 number_of_generations() - 1 /* max_level */);
747 }
748
749 result = gch->attempt_allocation(size, is_tlab, false /*first_only*/);
750
751 if (result != NULL) {
752 assert(gch->is_in_reserved(result), "result not in heap");
753 return result;
754 }
755
756 // OK, collection failed, try expansion.
757 result = expand_heap_and_allocate(size, is_tlab);
758 if (result != NULL) {
759 return result;
760 }
761
762 // If we reach this point, we're really out of memory. Try every trick
763 // we can to reclaim memory. Force collection of soft references. Force
764 // a complete compaction of the heap. Any additional methods for finding
765 // free memory should be here, especially if they are expensive. If this
766 // attempt fails, an OOM exception will be thrown.
767 {
768 UIntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
769
770 gch->do_collection(true /* full */,
771 true /* clear_all_soft_refs */,
772 size /* size */,
773 is_tlab /* is_tlab */,
774 number_of_generations() - 1 /* max_level */);
775 }
776
777 result = gch->attempt_allocation(size, is_tlab, false /* first_only */);
778 if (result != NULL) {
779 assert(gch->is_in_reserved(result), "result not in heap");
780 return result;
781 }
782
783 assert(!should_clear_all_soft_refs(),
784 "Flag should have been handled and cleared prior to this point");
785
786 // What else? We might try synchronous finalization later. If the total
787 // space available is large enough for the allocation, then a more
788 // complete compaction phase than we've tried so far might be
789 // appropriate.
790 return NULL;
791 }
792
793 MetaWord* CollectorPolicy::satisfy_failed_metadata_allocation(
794 ClassLoaderData* loader_data,
795 size_t word_size,
796 Metaspace::MetadataType mdtype) {
797 uint loop_count = 0;
798 uint gc_count = 0;
799 uint full_gc_count = 0;
800
801 assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock");
802
803 do {
804 MetaWord* result = NULL;
805 if (GC_locker::is_active_and_needs_gc()) {
806 // If the GC_locker is active, just expand and allocate.
807 // If that does not succeed, wait if this thread is not
808 // in a critical section itself.
809 result =
810 loader_data->metaspace_non_null()->expand_and_allocate(word_size,
811 mdtype);
812 if (result != NULL) {
813 return result;
814 }
815 JavaThread* jthr = JavaThread::current();
816 if (!jthr->in_critical()) {
817 // Wait for JNI critical section to be exited
818 GC_locker::stall_until_clear();
819 // The GC invoked by the last thread leaving the critical
820 // section will be a young collection and a full collection
821 // is (currently) needed for unloading classes so continue
822 // to the next iteration to get a full GC.
823 continue;
824 } else {
825 if (CheckJNICalls) {
826 fatal("Possible deadlock due to allocating while"
827 " in jni critical section");
828 }
829 return NULL;
830 }
831 }
832
833 { // Need lock to get self consistent gc_count's
834 MutexLocker ml(Heap_lock);
835 gc_count = Universe::heap()->total_collections();
836 full_gc_count = Universe::heap()->total_full_collections();
837 }
838
839 // Generate a VM operation
840 VM_CollectForMetadataAllocation op(loader_data,
841 word_size,
842 mdtype,
843 gc_count,
844 full_gc_count,
845 GCCause::_metadata_GC_threshold);
846 VMThread::execute(&op);
847
848 // If GC was locked out, try again. Check
849 // before checking success because the prologue
850 // could have succeeded and the GC still have
851 // been locked out.
852 if (op.gc_locked()) {
853 continue;
854 }
855
856 if (op.prologue_succeeded()) {
857 return op.result();
858 }
859 loop_count++;
860 if ((QueuedAllocationWarningCount > 0) &&
861 (loop_count % QueuedAllocationWarningCount == 0)) {
862 warning("satisfy_failed_metadata_allocation() retries %d times \n\t"
863 " size=%d", loop_count, word_size);
864 }
865 } while (true); // Until a GC is done
866 }
867
868 // Return true if any of the following is true:
869 // . the allocation won't fit into the current young gen heap
870 // . gc locker is occupied (jni critical section)
871 // . heap memory is tight -- the most recent previous collection
872 // was a full collection because a partial collection (would
873 // have) failed and is likely to fail again
874 bool GenCollectorPolicy::should_try_older_generation_allocation(
875 size_t word_size) const {
876 GenCollectedHeap* gch = GenCollectedHeap::heap();
877 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();
878 return (word_size > heap_word_size(gen0_capacity))
879 || GC_locker::is_active_and_needs_gc()
880 || gch->incremental_collection_failed();
881 }
882
883
884 //
885 // MarkSweepPolicy methods
886 //
887
888 MarkSweepPolicy::MarkSweepPolicy() {
889 initialize_all();
890 }
891
892 void MarkSweepPolicy::initialize_generations() {
893 _generations = NEW_C_HEAP_ARRAY3(GenerationSpecPtr, number_of_generations(), mtGC, 0, AllocFailStrategy::RETURN_NULL);
894 if (_generations == NULL)
895 vm_exit_during_initialization("Unable to allocate gen spec");
896
897 if (UseParNewGC) {
898 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);
899 } else {
900 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);
901 }
902 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);
903
904 if (_generations[0] == NULL || _generations[1] == NULL)
905 vm_exit_during_initialization("Unable to allocate gen spec");
906 }
907
908 void MarkSweepPolicy::initialize_gc_policy_counters() {
909 // initialize the policy counters - 2 collectors, 3 generations
910 if (UseParNewGC) {
911 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);
912 } else {
913 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
914 }
915 }