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::assert_flags() {
56 assert(InitialHeapSize <= MaxHeapSize, "Ergonomics decided on incompatible initial and maximum heap sizes");
57 assert(InitialHeapSize % _min_alignment == 0, "InitialHeapSize alignment");
58 assert(MaxHeapSize % _max_alignment == 0, "MaxHeapSize alignment");
59 }
60
61 void CollectorPolicy::assert_size_info() {
62 assert(_max_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible minimum and maximum heap sizes");
63 assert(_initial_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible initial and minimum heap sizes");
64 assert(_max_heap_byte_size >= _initial_heap_byte_size, "Ergonomics decided on incompatible initial and maximum heap sizes");
65 assert(_min_heap_byte_size % _min_alignment == 0, "min_heap_byte_size alignment");
66 assert(_initial_heap_byte_size % _min_alignment == 0, "initial_heap_byte_size alignment");
67 assert(_max_heap_byte_size % _max_alignment == 0, "max_heap_byte_size alignment");
68 }
69
70 void CollectorPolicy::initialize_flags() {
71 assert(_max_alignment >= _min_alignment,
72 err_msg("max_alignment: " SIZE_FORMAT " less than min_alignment: " SIZE_FORMAT,
73 _max_alignment, _min_alignment));
74 assert(_max_alignment % _min_alignment == 0,
75 err_msg("max_alignment: " SIZE_FORMAT " not aligned by min_alignment: " SIZE_FORMAT,
76 _max_alignment, _min_alignment));
77
78 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
79 if (FLAG_IS_CMDLINE(InitialHeapSize) && InitialHeapSize > MaxHeapSize) {
80 vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
81 }
82 if (Arguments::min_heap_size() != 0 && MaxHeapSize < Arguments::min_heap_size()) {
83 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified");
84 }
85 _max_heap_size_cmdline = true;
86 }
87
88 if (FLAG_IS_CMDLINE(InitialHeapSize) && Arguments::min_heap_size() != 0 &&
89 InitialHeapSize < Arguments::min_heap_size()) {
90 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified");
91 }
92 if (!FLAG_IS_DEFAULT(InitialHeapSize) && InitialHeapSize > MaxHeapSize) {
93 FLAG_SET_ERGO(uintx, MaxHeapSize, InitialHeapSize);
94 } else if (!FLAG_IS_DEFAULT(MaxHeapSize) && InitialHeapSize > MaxHeapSize) {
95 FLAG_SET_ERGO(uintx, InitialHeapSize, MaxHeapSize);
96 if (InitialHeapSize < Arguments::min_heap_size()) {
97 Arguments::set_min_heap_size(InitialHeapSize);
98 }
99 }
100
101 // User inputs from -Xmx and -Xms must be aligned
102 Arguments::set_min_heap_size(align_size_up(Arguments::min_heap_size(), _min_alignment));
103 uintx alignedInitialHeapSize = align_size_up(InitialHeapSize, _min_alignment);
104 uintx alignedMaxHeapSize = align_size_up(MaxHeapSize, _max_alignment);
105
106 // Write back to flags if the values changed
107 if (alignedInitialHeapSize != InitialHeapSize) {
108 FLAG_SET_ERGO(uintx, InitialHeapSize, alignedInitialHeapSize);
109 }
110 if (alignedMaxHeapSize != MaxHeapSize) {
111 FLAG_SET_ERGO(uintx, MaxHeapSize, alignedMaxHeapSize);
112 }
113
114 if (!is_size_aligned(MaxMetaspaceSize, _max_alignment)) {
115 FLAG_SET_ERGO(uintx, MaxMetaspaceSize,
116 restricted_align_down(MaxMetaspaceSize, _max_alignment));
117 }
118
119 if (MetaspaceSize > MaxMetaspaceSize) {
120 FLAG_SET_ERGO(uintx, MetaspaceSize, MaxMetaspaceSize);
121 }
122
123 if (!is_size_aligned(MetaspaceSize, _min_alignment)) {
124 FLAG_SET_ERGO(uintx, MetaspaceSize,
125 restricted_align_down(MetaspaceSize, _min_alignment));
126 }
127
128 assert(MetaspaceSize <= MaxMetaspaceSize, "Must be");
129
130 MinMetaspaceExpansion = restricted_align_down(MinMetaspaceExpansion, _min_alignment);
131 MaxMetaspaceExpansion = restricted_align_down(MaxMetaspaceExpansion, _min_alignment);
132
133 MinHeapDeltaBytes = align_size_up(MinHeapDeltaBytes, _min_alignment);
134
135 assert(MetaspaceSize % _min_alignment == 0, "metapace alignment");
136 assert(MaxMetaspaceSize % _max_alignment == 0, "maximum metaspace alignment");
137 if (MetaspaceSize < 256*K) {
138 vm_exit_during_initialization("Too small initial Metaspace size");
139 }
140
141 CollectorPolicy::assert_flags();
142 }
143
144 void CollectorPolicy::initialize_size_info() {
145 _min_heap_byte_size = Arguments::min_heap_size();
146 _initial_heap_byte_size = InitialHeapSize;
147 _max_heap_byte_size = MaxHeapSize;
148
149 // Check heap parameter properties
150 if (_initial_heap_byte_size < M) {
151 vm_exit_during_initialization("Too small initial heap");
152 }
153 // Check heap parameter properties
154 if (_min_heap_byte_size < M) {
155 vm_exit_during_initialization("Too small minimum heap");
156 }
157
158 if (PrintGCDetails && Verbose) {
159 gclog_or_tty->print_cr("Minimum heap " SIZE_FORMAT " Initial heap "
160 SIZE_FORMAT " Maximum heap " SIZE_FORMAT,
161 _min_heap_byte_size, _initial_heap_byte_size, _max_heap_byte_size);
162 }
163
164 CollectorPolicy::assert_size_info();
165 }
166
167 bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) {
168 bool result = _should_clear_all_soft_refs;
169 set_should_clear_all_soft_refs(false);
170 return result;
171 }
172
173 GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap,
174 int max_covered_regions) {
175 assert(rem_set_name() == GenRemSet::CardTable, "unrecognized GenRemSet::Name");
176 return new CardTableRS(whole_heap, max_covered_regions);
177 }
178
179 void CollectorPolicy::cleared_all_soft_refs() {
180 // If near gc overhear limit, continue to clear SoftRefs. SoftRefs may
181 // have been cleared in the last collection but if the gc overhear
182 // limit continues to be near, SoftRefs should still be cleared.
183 if (size_policy() != NULL) {
184 _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near();
185 }
186 _all_soft_refs_clear = true;
187 }
188
189 size_t CollectorPolicy::compute_max_alignment() {
190 // The card marking array and the offset arrays for old generations are
191 // committed in os pages as well. Make sure they are entirely full (to
192 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
193 // byte entry and the os page size is 4096, the maximum heap size should
194 // be 512*4096 = 2MB aligned.
195
196 // There is only the GenRemSet in Hotspot and only the GenRemSet::CardTable
197 // is supported.
198 // Requirements of any new remembered set implementations must be added here.
199 size_t alignment = GenRemSet::max_alignment_constraint(GenRemSet::CardTable);
200
201 // Parallel GC does its own alignment of the generations to avoid requiring a
202 // large page (256M on some platforms) for the permanent generation. The
203 // other collectors should also be updated to do their own alignment and then
204 // this use of lcm() should be removed.
205 if (UseLargePages && !UseParallelGC) {
206 // in presence of large pages we have to make sure that our
207 // alignment is large page aware
208 alignment = lcm(os::large_page_size(), alignment);
209 }
210
211 return alignment;
212 }
213
214 // GenCollectorPolicy methods.
215
216 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {
217 return restricted_align_down(base_size / (NewRatio + 1), _min_alignment);
218 }
219
220 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,
221 size_t maximum_size) {
222 size_t alignment = _min_alignment;
223 size_t max_minus = maximum_size - alignment;
224 return desired_size < max_minus ? desired_size : max_minus;
225 }
226
227
228 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size,
229 size_t init_promo_size,
230 size_t init_survivor_size) {
231 const double max_gc_pause_sec = ((double) MaxGCPauseMillis)/1000.0;
232 _size_policy = new AdaptiveSizePolicy(init_eden_size,
233 init_promo_size,
234 init_survivor_size,
235 max_gc_pause_sec,
236 GCTimeRatio);
237 }
238
239 size_t GenCollectorPolicy::compute_max_alignment() {
240 // The card marking array and the offset arrays for old generations are
241 // committed in os pages as well. Make sure they are entirely full (to
242 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
243 // byte entry and the os page size is 4096, the maximum heap size should
244 // be 512*4096 = 2MB aligned.
245 size_t alignment = GenRemSet::max_alignment_constraint(rem_set_name());
246
247 // Parallel GC does its own alignment of the generations to avoid requiring a
248 // large page (256M on some platforms) for the permanent generation. The
249 // other collectors should also be updated to do their own alignment and then
250 // this use of lcm() should be removed.
251 if (UseLargePages && !UseParallelGC) {
252 // in presence of large pages we have to make sure that our
253 // alignment is large page aware
254 alignment = lcm(os::large_page_size(), alignment);
255 }
256
257 assert(alignment >= _min_alignment, "Must be");
258
259 return alignment;
260 }
261
262 void GenCollectorPolicy::assert_flags() {
263 CollectorPolicy::assert_flags();
264 assert(NewSize >= _min_gen0_size, "Ergonomics decided on a too small young gen size");
265 assert(NewSize <= MaxNewSize, "Ergonomics decided on incompatible initial and maximum young gen sizes");
266 assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize < MaxHeapSize, "Ergonomics decided on incompatible maximum young gen and heap sizes");
267 assert(NewSize % _min_alignment == 0, "NewSize alignment");
268 assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize % _min_alignment == 0, "MaxNewSize alignment");
269 }
270
271 void TwoGenerationCollectorPolicy::assert_flags() {
272 GenCollectorPolicy::assert_flags();
273 assert(OldSize + NewSize <= MaxHeapSize, "Ergonomics decided on incompatible generation and heap sizes");
274 assert(OldSize % _min_alignment == 0, "OldSize alignment");
275 }
276
277 void GenCollectorPolicy::assert_size_info() {
278 CollectorPolicy::assert_size_info();
279 // GenCollectorPolicy::initialize_size_info may update the MaxNewSize
280 assert(MaxNewSize < MaxHeapSize, "Ergonomics decided on incompatible maximum young and heap sizes");
281 assert(_min_gen0_size <= _initial_gen0_size, "Ergonomics decided on incompatible minimum and initial young gen sizes");
282 assert(_initial_gen0_size <= _max_gen0_size, "Ergonomics decided on incompatible initial and maximum young gen sizes");
283 assert(_min_gen0_size % _min_alignment == 0, "_min_gen0_size alignment");
284 assert(_initial_gen0_size % _min_alignment == 0, "_initial_gen0_size alignment");
285 assert(_max_gen0_size % _min_alignment == 0, "_max_gen0_size alignment");
286 }
287
288 void TwoGenerationCollectorPolicy::assert_size_info() {
289 GenCollectorPolicy::assert_size_info();
290 assert(_min_gen1_size <= _initial_gen1_size, "Ergonomics decided on incompatible minimum and initial old gen sizes");
291 assert(_initial_gen1_size <= _max_gen1_size, "Ergonomics decided on incompatible initial and maximum old gen sizes");
292 assert(_max_gen1_size % _min_alignment == 0, "_max_gen1_size alignment");
293 assert(_initial_gen1_size % _min_alignment == 0, "_initial_gen1_size alignment");
294 assert(_max_heap_byte_size <= (_max_gen0_size + _max_gen1_size), "Total maximum heap sizes must be sum of generation maximum sizes");
295 }
296
297 void GenCollectorPolicy::initialize_flags() {
298 // All sizes must be multiples of the generation granularity.
299 _min_alignment = (uintx) Generation::GenGrain;
300 _max_alignment = compute_max_alignment();
301
302 CollectorPolicy::initialize_flags();
303
304 // This is the absolute minimum for the young generation. It has to hold two
305 // survivor areas and the eden. We set it here since it is used repeatedly
306 // throughout the initialization. However this is not necessarily the final
307 // value of _min_gen0_size.
308 _min_gen0_size = 3 * intra_heap_alignment();
309
310 // Make sure the heap is large enough for two generations.
311 uintx smallestHeapSize = _min_gen0_size + intra_heap_alignment();
312 if (MaxHeapSize < smallestHeapSize) {
313 FLAG_SET_ERGO(uintx, MaxHeapSize, align_size_up(smallestHeapSize, _max_alignment));
314 }
315
316 // All generational heaps have a youngest gen; handle those flags here.
317
318 if (FLAG_IS_CMDLINE(NewSize) && FLAG_IS_CMDLINE(MaxNewSize) && NewSize > MaxNewSize) {
319 vm_exit_during_initialization("Incompatible initial and maximum young gen sizes specified");
320 }
321
322 if (!FLAG_IS_DEFAULT(MaxNewSize)) {
323 uintx minNewSize = MAX2(_min_alignment, _min_gen0_size);
324
325 if (MaxNewSize >= MaxHeapSize) {
326 uintx smallerMaxNewSize = MaxHeapSize - _min_alignment;
327 if (FLAG_IS_CMDLINE(MaxNewSize)) {
328 warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or greater than the entire "
329 "heap (" SIZE_FORMAT "k). A new max generation size of " SIZE_FORMAT "k will be used.",
330 MaxNewSize/K, MaxHeapSize/K, smallerMaxNewSize/K);
331 }
332 FLAG_SET_ERGO(uintx, MaxNewSize, smallerMaxNewSize);
333 if (NewSize > MaxNewSize) {
334 FLAG_SET_ERGO(uintx, NewSize, MaxNewSize);
335 }
336 } else if (MaxNewSize < minNewSize) {
337 FLAG_SET_ERGO(uintx, MaxNewSize, minNewSize);
338 } else if (!is_size_aligned(MaxNewSize, _min_alignment)) {
339 FLAG_SET_ERGO(uintx, MaxNewSize, align_size_down(MaxNewSize, _min_alignment));
340 }
341 }
342
343 // Young space must be aligned and have room for eden + two survivors.
344 // We will silently increase the NewSize even if the user specified a smaller value.
345 uintx smallestNewSize = MAX2(align_size_up(_min_gen0_size, _min_alignment),
346 align_size_down(NewSize, _min_alignment));
347 if (smallestNewSize != NewSize) {
348 FLAG_SET_ERGO(uintx, NewSize, smallestNewSize);
349 }
350
351 if (NewSize > MaxNewSize) {
352 // At this point this should only happen if the user specifies a large NewSize or
353 // a small (but not too small) MaxNewSize.
354 if (FLAG_IS_CMDLINE(NewSize)) {
355 warning("NewSize (" SIZE_FORMAT "k) is greater than the MaxNewSize (" SIZE_FORMAT "k). "
356 "A new generation size of " SIZE_FORMAT "k will be used.",
357 NewSize/K, MaxNewSize/K, MaxNewSize/K);
358 }
359 FLAG_SET_ERGO(uintx, NewSize, MaxNewSize);
360 }
361
362 if (SurvivorRatio < 1 || NewRatio < 1) {
363 vm_exit_during_initialization("Invalid young gen ratio specified");
364 }
365
366 GenCollectorPolicy::assert_flags();
367 }
368
369 void TwoGenerationCollectorPolicy::initialize_flags() {
370 GenCollectorPolicy::initialize_flags();
371
372 if (!is_size_aligned(OldSize, _min_alignment)) {
373 FLAG_SET_ERGO(uintx, OldSize, align_size_down(OldSize, _min_alignment));
374 }
375
376 if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(MaxHeapSize)) {
377 // NewRatio will be used later to set the young generation size so we use
378 // it to calculate how big the heap should be based on the requested OldSize
379 // and NewRatio.
380 assert(NewRatio > 0, "NewRatio should have been set up earlier");
381 size_t calculated_heapsize = (OldSize / NewRatio) * (NewRatio + 1);
382
383 calculated_heapsize = align_size_up(calculated_heapsize, _max_alignment);
384 FLAG_SET_ERGO(uintx, MaxHeapSize, calculated_heapsize);
385 FLAG_SET_ERGO(uintx, InitialHeapSize, calculated_heapsize);
386 }
387
388 // adjust max heap size if necessary
389 if (NewSize + OldSize > MaxHeapSize) {
390 if (_max_heap_size_cmdline) {
391 // Somebody has set a maximum heap size with the intention that we should not
392 // exceed it. Adjust New/OldSize as necessary.
393 uintx calculated_size = NewSize + OldSize;
394 double shrink_factor = (double) MaxHeapSize / calculated_size;
395 // align
396 FLAG_SET_ERGO(uintx, NewSize, MAX2(_min_gen0_size, (uintx)align_size_down((uintx)(NewSize * shrink_factor), _min_alignment)));
397
398 // OldSize is already aligned because above we aligned MaxHeapSize to
399 // _max_alignment, and we just made sure that NewSize is aligned to
400 // _min_alignment. In initialize_flags() we verified that _max_alignment
401 // is a multiple of _min_alignment.
402 FLAG_SET_ERGO(uintx, OldSize, MaxHeapSize - NewSize);
403 } else {
404 FLAG_SET_ERGO(uintx, MaxHeapSize, align_size_up(NewSize + OldSize, _max_alignment));
405 }
406 }
407
408 always_do_update_barrier = UseConcMarkSweepGC;
409 TwoGenerationCollectorPolicy::assert_flags();
410 }
411
412 // Values set on the command line win over any ergonomically
413 // set command line parameters.
414 // Ergonomic choice of parameters are done before this
415 // method is called. Values for command line parameters such as NewSize
416 // and MaxNewSize feed those ergonomic choices into this method.
417 // This method makes the final generation sizings consistent with
418 // themselves and with overall heap sizings.
419 // In the absence of explicitly set command line flags, policies
420 // such as the use of NewRatio are used to size the generation.
421 void GenCollectorPolicy::initialize_size_info() {
422 CollectorPolicy::initialize_size_info();
423
424 // _min_alignment is used for alignment within a generation.
425 // There is additional alignment done down stream for some
426 // collectors that sometimes causes unwanted rounding up of
427 // generations sizes.
428
429 // Determine maximum size of gen0
430
431 size_t max_new_size = 0;
432 if (!FLAG_IS_DEFAULT(MaxNewSize)) {
433 max_new_size = MaxNewSize;
434 } else {
435 max_new_size = scale_by_NewRatio_aligned(_max_heap_byte_size);
436 // Bound the maximum size by NewSize below (since it historically
437 // would have been NewSize and because the NewRatio calculation could
438 // yield a size that is too small) and bound it by MaxNewSize above.
439 // Ergonomics plays here by previously calculating the desired
440 // NewSize and MaxNewSize.
441 max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize);
442 }
443 assert(max_new_size > 0, "All paths should set max_new_size");
444
445 // Given the maximum gen0 size, determine the initial and
446 // minimum gen0 sizes.
447
448 if (_max_heap_byte_size == _min_heap_byte_size) {
449 // The maximum and minimum heap sizes are the same so
450 // the generations minimum and initial must be the
451 // same as its maximum.
452 _min_gen0_size = max_new_size;
453 _initial_gen0_size = max_new_size;
454 _max_gen0_size = max_new_size;
455 } else {
456 size_t desired_new_size = 0;
457 if (!FLAG_IS_DEFAULT(NewSize)) {
458 // If NewSize is set ergonomically (for example by cms), it
459 // would make sense to use it. If it is used, also use it
460 // to set the initial size. Although there is no reason
461 // the minimum size and the initial size have to be the same,
462 // the current implementation gets into trouble during the calculation
463 // of the tenured generation sizes if they are different.
464 // Note that this makes the initial size and the minimum size
465 // generally small compared to the NewRatio calculation.
466 _min_gen0_size = NewSize;
467 desired_new_size = NewSize;
468 max_new_size = MAX2(max_new_size, NewSize);
469 } else {
470 // For the case where NewSize is the default, use NewRatio
471 // to size the minimum and initial generation sizes.
472 // Use the default NewSize as the floor for these values. If
473 // NewRatio is overly large, the resulting sizes can be too
474 // small.
475 _min_gen0_size = MAX2(scale_by_NewRatio_aligned(_min_heap_byte_size), NewSize);
476 desired_new_size =
477 MAX2(scale_by_NewRatio_aligned(_initial_heap_byte_size), NewSize);
478 }
479
480 assert(_min_gen0_size > 0, "Sanity check");
481 _initial_gen0_size = desired_new_size;
482 _max_gen0_size = max_new_size;
483
484 // At this point the desirable initial and minimum sizes have been
485 // determined without regard to the maximum sizes.
486
487 // Bound the sizes by the corresponding overall heap sizes.
488 _min_gen0_size = bound_minus_alignment(_min_gen0_size, _min_heap_byte_size);
489 _initial_gen0_size = bound_minus_alignment(_initial_gen0_size, _initial_heap_byte_size);
490 _max_gen0_size = bound_minus_alignment(_max_gen0_size, _max_heap_byte_size);
491
492 // At this point all three sizes have been checked against the
493 // maximum sizes but have not been checked for consistency
494 // among the three.
495
496 // Final check min <= initial <= max
497 _min_gen0_size = MIN2(_min_gen0_size, _max_gen0_size);
498 _initial_gen0_size = MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size);
499 _min_gen0_size = MIN2(_min_gen0_size, _initial_gen0_size);
500 }
501
502 // Write back to flag if necessary
503 if (MaxNewSize != _min_gen0_size) {
504 FLAG_SET_ERGO(uintx, MaxNewSize, _max_gen0_size);
505 }
506
507 if (PrintGCDetails && Verbose) {
508 gclog_or_tty->print_cr("1: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
509 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
510 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
511 }
512
513 GenCollectorPolicy::assert_size_info();
514 }
515
516 // Call this method during the sizing of the gen1 to make
517 // adjustments to gen0 because of gen1 sizing policy. gen0 initially has
518 // the most freedom in sizing because it is done before the
519 // policy for gen1 is applied. Once gen1 policies have been applied,
520 // there may be conflicts in the shape of the heap and this method
521 // is used to make the needed adjustments. The application of the
522 // policies could be more sophisticated (iterative for example) but
523 // keeping it simple also seems a worthwhile goal.
524 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr,
525 size_t* gen1_size_ptr,
526 const size_t heap_size,
527 const size_t min_gen1_size) {
528 bool result = false;
529
530 if ((*gen1_size_ptr + *gen0_size_ptr) > heap_size) {
531 if ((heap_size < (*gen0_size_ptr + min_gen1_size)) &&
532 (heap_size >= min_gen1_size + _min_alignment)) {
533 // Adjust gen0 down to accommodate min_gen1_size
534 *gen0_size_ptr = restricted_align_down(heap_size - min_gen1_size, _min_alignment);
535 assert(*gen0_size_ptr > 0, "Min gen0 is too large");
536 result = true;
537 } else {
538 *gen1_size_ptr = restricted_align_down(heap_size - *gen0_size_ptr, _min_alignment);
539 }
540 }
541 return result;
542 }
543
544 // Minimum sizes of the generations may be different than
545 // the initial sizes. An inconsistency is permitted here
546 // in the total size that can be specified explicitly by
547 // command line specification of OldSize and NewSize and
548 // also a command line specification of -Xms. Issue a warning
549 // but allow the values to pass.
550
551 void TwoGenerationCollectorPolicy::initialize_size_info() {
552 GenCollectorPolicy::initialize_size_info();
553
554 // At this point the minimum, initial and maximum sizes
555 // of the overall heap and of gen0 have been determined.
556 // The maximum gen1 size can be determined from the maximum gen0
557 // and maximum heap size since no explicit flags exist
558 // for setting the gen1 maximum.
559 _max_gen1_size = MAX2(_max_heap_byte_size - _max_gen0_size, _min_alignment);
560
561 // If no explicit command line flag has been set for the
562 // gen1 size, use what is left for gen1.
563 if (!FLAG_IS_CMDLINE(OldSize)) {
564 // The user has not specified any value but the ergonomics
565 // may have chosen a value (which may or may not be consistent
566 // with the overall heap size). In either case make
567 // the minimum, maximum and initial sizes consistent
568 // with the gen0 sizes and the overall heap sizes.
569 _min_gen1_size = MAX2(_min_heap_byte_size - _min_gen0_size, _min_alignment);
570 _initial_gen1_size = MAX2(_initial_heap_byte_size - _initial_gen0_size, _min_alignment);
571 // _max_gen1_size has already been made consistent above
572 FLAG_SET_ERGO(uintx, OldSize, _initial_gen1_size);
573 } else {
574 // OldSize has been explicitly set on the command line. Use the
575 // OldSize and then determine the consequences.
576 _min_gen1_size = MIN2(OldSize, _min_heap_byte_size - _min_gen0_size);
577 _initial_gen1_size = OldSize;
578
579 // If the user has explicitly set an OldSize that is inconsistent
580 // with other command line flags, issue a warning.
581 // The generation minimums and the overall heap minimum should
582 // be within one heap alignment.
583 if ((_min_gen1_size + _min_gen0_size + _min_alignment) < _min_heap_byte_size) {
584 warning("Inconsistency between minimum heap size and minimum "
585 "generation sizes: using minimum heap = " SIZE_FORMAT,
586 _min_heap_byte_size);
587 }
588 if (OldSize > _max_gen1_size) {
589 warning("Inconsistency between maximum heap size and maximum "
590 "generation sizes: using maximum heap = " SIZE_FORMAT
591 " -XX:OldSize flag is being ignored",
592 _max_heap_byte_size);
593 }
594 // If there is an inconsistency between the OldSize and the minimum and/or
595 // initial size of gen0, since OldSize was explicitly set, OldSize wins.
596 if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size,
597 _min_heap_byte_size, _min_gen1_size)) {
598 if (PrintGCDetails && Verbose) {
599 gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
600 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
601 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
602 }
603 }
604 // The same as above for the old gen initial size
605 if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,
606 _initial_heap_byte_size, _initial_gen1_size)) {
607 if (PrintGCDetails && Verbose) {
608 gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
609 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
610 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
611 }
612 }
613 // update OldSize
614 FLAG_SET_ERGO(uintx, OldSize, _initial_gen1_size);
615 }
616
617 _min_gen1_size = MIN2(_min_gen1_size, _max_gen1_size);
618
619 // Make sure that min gen1 <= initial gen1 <= max gen1
620 _initial_gen1_size = MAX2(_initial_gen1_size, _min_gen1_size);
621 _initial_gen1_size = MIN2(_initial_gen1_size, _max_gen1_size);
622
623 if (PrintGCDetails && Verbose) {
624 gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 "
625 SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT,
626 _min_gen1_size, _initial_gen1_size, _max_gen1_size);
627 }
628
629 TwoGenerationCollectorPolicy::assert_size_info();
630 }
631
632 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
633 bool is_tlab,
634 bool* gc_overhead_limit_was_exceeded) {
635 GenCollectedHeap *gch = GenCollectedHeap::heap();
636
637 debug_only(gch->check_for_valid_allocation_state());
638 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
639
640 // In general gc_overhead_limit_was_exceeded should be false so
641 // set it so here and reset it to true only if the gc time
642 // limit is being exceeded as checked below.
643 *gc_overhead_limit_was_exceeded = false;
644
645 HeapWord* result = NULL;
646
647 // Loop until the allocation is satisfied, or unsatisfied after GC.
648 for (int try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) {
649 HandleMark hm; // discard any handles allocated in each iteration
650
651 // First allocation attempt is lock-free.
652 Generation *gen0 = gch->get_gen(0);
653 assert(gen0->supports_inline_contig_alloc(),
654 "Otherwise, must do alloc within heap lock");
655 if (gen0->should_allocate(size, is_tlab)) {
656 result = gen0->par_allocate(size, is_tlab);
657 if (result != NULL) {
658 assert(gch->is_in_reserved(result), "result not in heap");
659 return result;
660 }
661 }
662 unsigned int gc_count_before; // read inside the Heap_lock locked region
663 {
664 MutexLocker ml(Heap_lock);
665 if (PrintGC && Verbose) {
666 gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:"
667 " attempting locked slow path allocation");
668 }
669 // Note that only large objects get a shot at being
670 // allocated in later generations.
671 bool first_only = ! should_try_older_generation_allocation(size);
672
673 result = gch->attempt_allocation(size, is_tlab, first_only);
674 if (result != NULL) {
675 assert(gch->is_in_reserved(result), "result not in heap");
676 return result;
677 }
678
679 if (GC_locker::is_active_and_needs_gc()) {
680 if (is_tlab) {
681 return NULL; // Caller will retry allocating individual object
682 }
683 if (!gch->is_maximal_no_gc()) {
684 // Try and expand heap to satisfy request
685 result = expand_heap_and_allocate(size, is_tlab);
686 // result could be null if we are out of space
687 if (result != NULL) {
688 return result;
689 }
690 }
691
692 if (gclocker_stalled_count > GCLockerRetryAllocationCount) {
693 return NULL; // we didn't get to do a GC and we didn't get any memory
694 }
695
696 // If this thread is not in a jni critical section, we stall
697 // the requestor until the critical section has cleared and
698 // GC allowed. When the critical section clears, a GC is
699 // initiated by the last thread exiting the critical section; so
700 // we retry the allocation sequence from the beginning of the loop,
701 // rather than causing more, now probably unnecessary, GC attempts.
702 JavaThread* jthr = JavaThread::current();
703 if (!jthr->in_critical()) {
704 MutexUnlocker mul(Heap_lock);
705 // Wait for JNI critical section to be exited
706 GC_locker::stall_until_clear();
707 gclocker_stalled_count += 1;
708 continue;
709 } else {
710 if (CheckJNICalls) {
711 fatal("Possible deadlock due to allocating while"
712 " in jni critical section");
713 }
714 return NULL;
715 }
716 }
717
718 // Read the gc count while the heap lock is held.
719 gc_count_before = Universe::heap()->total_collections();
720 }
721
722 VM_GenCollectForAllocation op(size, is_tlab, gc_count_before);
723 VMThread::execute(&op);
724 if (op.prologue_succeeded()) {
725 result = op.result();
726 if (op.gc_locked()) {
727 assert(result == NULL, "must be NULL if gc_locked() is true");
728 continue; // retry and/or stall as necessary
729 }
730
731 // Allocation has failed and a collection
732 // has been done. If the gc time limit was exceeded the
733 // this time, return NULL so that an out-of-memory
734 // will be thrown. Clear gc_overhead_limit_exceeded
735 // so that the overhead exceeded does not persist.
736
737 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
738 const bool softrefs_clear = all_soft_refs_clear();
739
740 if (limit_exceeded && softrefs_clear) {
741 *gc_overhead_limit_was_exceeded = true;
742 size_policy()->set_gc_overhead_limit_exceeded(false);
743 if (op.result() != NULL) {
744 CollectedHeap::fill_with_object(op.result(), size);
745 }
746 return NULL;
747 }
748 assert(result == NULL || gch->is_in_reserved(result),
749 "result not in heap");
750 return result;
751 }
752
753 // Give a warning if we seem to be looping forever.
754 if ((QueuedAllocationWarningCount > 0) &&
755 (try_count % QueuedAllocationWarningCount == 0)) {
756 warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t"
757 " size=%d %s", try_count, size, is_tlab ? "(TLAB)" : "");
758 }
759 }
760 }
761
762 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size,
763 bool is_tlab) {
764 GenCollectedHeap *gch = GenCollectedHeap::heap();
765 HeapWord* result = NULL;
766 for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) {
767 Generation *gen = gch->get_gen(i);
768 if (gen->should_allocate(size, is_tlab)) {
769 result = gen->expand_and_allocate(size, is_tlab);
770 }
771 }
772 assert(result == NULL || gch->is_in_reserved(result), "result not in heap");
773 return result;
774 }
775
776 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size,
777 bool is_tlab) {
778 GenCollectedHeap *gch = GenCollectedHeap::heap();
779 GCCauseSetter x(gch, GCCause::_allocation_failure);
780 HeapWord* result = NULL;
781
782 assert(size != 0, "Precondition violated");
783 if (GC_locker::is_active_and_needs_gc()) {
784 // GC locker is active; instead of a collection we will attempt
785 // to expand the heap, if there's room for expansion.
786 if (!gch->is_maximal_no_gc()) {
787 result = expand_heap_and_allocate(size, is_tlab);
788 }
789 return result; // could be null if we are out of space
790 } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) {
791 // Do an incremental collection.
792 gch->do_collection(false /* full */,
793 false /* clear_all_soft_refs */,
794 size /* size */,
795 is_tlab /* is_tlab */,
796 number_of_generations() - 1 /* max_level */);
797 } else {
798 if (Verbose && PrintGCDetails) {
799 gclog_or_tty->print(" :: Trying full because partial may fail :: ");
800 }
801 // Try a full collection; see delta for bug id 6266275
802 // for the original code and why this has been simplified
803 // with from-space allocation criteria modified and
804 // such allocation moved out of the safepoint path.
805 gch->do_collection(true /* full */,
806 false /* clear_all_soft_refs */,
807 size /* size */,
808 is_tlab /* is_tlab */,
809 number_of_generations() - 1 /* max_level */);
810 }
811
812 result = gch->attempt_allocation(size, is_tlab, false /*first_only*/);
813
814 if (result != NULL) {
815 assert(gch->is_in_reserved(result), "result not in heap");
816 return result;
817 }
818
819 // OK, collection failed, try expansion.
820 result = expand_heap_and_allocate(size, is_tlab);
821 if (result != NULL) {
822 return result;
823 }
824
825 // If we reach this point, we're really out of memory. Try every trick
826 // we can to reclaim memory. Force collection of soft references. Force
827 // a complete compaction of the heap. Any additional methods for finding
828 // free memory should be here, especially if they are expensive. If this
829 // attempt fails, an OOM exception will be thrown.
830 {
831 UIntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
832
833 gch->do_collection(true /* full */,
834 true /* clear_all_soft_refs */,
835 size /* size */,
836 is_tlab /* is_tlab */,
837 number_of_generations() - 1 /* max_level */);
838 }
839
840 result = gch->attempt_allocation(size, is_tlab, false /* first_only */);
841 if (result != NULL) {
842 assert(gch->is_in_reserved(result), "result not in heap");
843 return result;
844 }
845
846 assert(!should_clear_all_soft_refs(),
847 "Flag should have been handled and cleared prior to this point");
848
849 // What else? We might try synchronous finalization later. If the total
850 // space available is large enough for the allocation, then a more
851 // complete compaction phase than we've tried so far might be
852 // appropriate.
853 return NULL;
854 }
855
856 MetaWord* CollectorPolicy::satisfy_failed_metadata_allocation(
857 ClassLoaderData* loader_data,
858 size_t word_size,
859 Metaspace::MetadataType mdtype) {
860 uint loop_count = 0;
861 uint gc_count = 0;
862 uint full_gc_count = 0;
863
864 assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock");
865
866 do {
867 MetaWord* result = NULL;
868 if (GC_locker::is_active_and_needs_gc()) {
869 // If the GC_locker is active, just expand and allocate.
870 // If that does not succeed, wait if this thread is not
871 // in a critical section itself.
872 result =
873 loader_data->metaspace_non_null()->expand_and_allocate(word_size,
874 mdtype);
875 if (result != NULL) {
876 return result;
877 }
878 JavaThread* jthr = JavaThread::current();
879 if (!jthr->in_critical()) {
880 // Wait for JNI critical section to be exited
881 GC_locker::stall_until_clear();
882 // The GC invoked by the last thread leaving the critical
883 // section will be a young collection and a full collection
884 // is (currently) needed for unloading classes so continue
885 // to the next iteration to get a full GC.
886 continue;
887 } else {
888 if (CheckJNICalls) {
889 fatal("Possible deadlock due to allocating while"
890 " in jni critical section");
891 }
892 return NULL;
893 }
894 }
895
896 { // Need lock to get self consistent gc_count's
897 MutexLocker ml(Heap_lock);
898 gc_count = Universe::heap()->total_collections();
899 full_gc_count = Universe::heap()->total_full_collections();
900 }
901
902 // Generate a VM operation
903 VM_CollectForMetadataAllocation op(loader_data,
904 word_size,
905 mdtype,
906 gc_count,
907 full_gc_count,
908 GCCause::_metadata_GC_threshold);
909 VMThread::execute(&op);
910
911 // If GC was locked out, try again. Check
912 // before checking success because the prologue
913 // could have succeeded and the GC still have
914 // been locked out.
915 if (op.gc_locked()) {
916 continue;
917 }
918
919 if (op.prologue_succeeded()) {
920 return op.result();
921 }
922 loop_count++;
923 if ((QueuedAllocationWarningCount > 0) &&
924 (loop_count % QueuedAllocationWarningCount == 0)) {
925 warning("satisfy_failed_metadata_allocation() retries %d times \n\t"
926 " size=%d", loop_count, word_size);
927 }
928 } while (true); // Until a GC is done
929 }
930
931 // Return true if any of the following is true:
932 // . the allocation won't fit into the current young gen heap
933 // . gc locker is occupied (jni critical section)
934 // . heap memory is tight -- the most recent previous collection
935 // was a full collection because a partial collection (would
936 // have) failed and is likely to fail again
937 bool GenCollectorPolicy::should_try_older_generation_allocation(
938 size_t word_size) const {
939 GenCollectedHeap* gch = GenCollectedHeap::heap();
940 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();
941 return (word_size > heap_word_size(gen0_capacity))
942 || GC_locker::is_active_and_needs_gc()
943 || gch->incremental_collection_failed();
944 }
945
946
947 //
948 // MarkSweepPolicy methods
949 //
950
951 MarkSweepPolicy::MarkSweepPolicy() {
952 initialize_all();
953 }
954
955 void MarkSweepPolicy::initialize_generations() {
956 _generations = NEW_C_HEAP_ARRAY3(GenerationSpecPtr, number_of_generations(), mtGC, 0, AllocFailStrategy::RETURN_NULL);
957 if (_generations == NULL) {
958 vm_exit_during_initialization("Unable to allocate gen spec");
959 }
960
961 if (UseParNewGC) {
962 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);
963 } else {
964 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);
965 }
966 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);
967
968 if (_generations[0] == NULL || _generations[1] == NULL) {
969 vm_exit_during_initialization("Unable to allocate gen spec");
970 }
971 }
972
973 void MarkSweepPolicy::initialize_gc_policy_counters() {
974 // initialize the policy counters - 2 collectors, 3 generations
975 if (UseParNewGC) {
976 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);
977 } else {
978 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
979 }
980 }