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 (FLAG_IS_CMDLINE(MaxHeapSize)) {
64 if (FLAG_IS_CMDLINE(InitialHeapSize) && InitialHeapSize > MaxHeapSize) {
65 vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
66 }
67 if (Arguments::min_heap_size() != 0 && MaxHeapSize < Arguments::min_heap_size()) {
68 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified");
69 }
70 _max_heap_size_cmdline = true;
71 }
72
73 if (FLAG_IS_CMDLINE(InitialHeapSize) && Arguments::min_heap_size() != 0 &&
74 InitialHeapSize < Arguments::min_heap_size()) {
75 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified");
76 }
77 if (!FLAG_IS_DEFAULT(InitialHeapSize) && InitialHeapSize > MaxHeapSize) {
78 FLAG_SET_ERGO(uintx, MaxHeapSize, InitialHeapSize);
79 } else if (!FLAG_IS_DEFAULT(MaxHeapSize) && InitialHeapSize > MaxHeapSize) {
80 FLAG_SET_ERGO(uintx, InitialHeapSize, MaxHeapSize);
81 if (InitialHeapSize < Arguments::min_heap_size()) {
82 Arguments::set_min_heap_size(InitialHeapSize);
83 }
84 }
85
86 // User inputs from -Xmx and -Xms must be aligned
87 Arguments::set_min_heap_size(align_size_up(Arguments::min_heap_size(), _min_alignment));
88 uintx alignedInitialHeapSize = align_size_up(InitialHeapSize, _min_alignment);
89 uintx alignedMaxHeapSize = align_size_up(MaxHeapSize, _max_alignment);
90
91 // Write back to flags if the values was changed
92 if (alignedInitialHeapSize != InitialHeapSize) {
93 FLAG_SET_ERGO(uintx, InitialHeapSize, alignedInitialHeapSize);
94 }
95 if (alignedMaxHeapSize != MaxHeapSize) {
96 FLAG_SET_ERGO(uintx, MaxHeapSize, alignedMaxHeapSize);
97 }
98
99 assert(InitialHeapSize <= MaxHeapSize, "Ergonomics decided on incompatible initial and maximum heap sizes");
100 assert(InitialHeapSize % _min_alignment == 0, "InitialHeapSize alignment");
101 assert(MaxHeapSize % _max_alignment == 0, "MaxHeapSize alignment");
102
103 if (!is_size_aligned(MaxMetaspaceSize, _max_alignment)) {
104 FLAG_SET_ERGO(uintx, MaxMetaspaceSize,
105 restricted_align_down(MaxMetaspaceSize, _max_alignment));
106 }
107
108 if (MetaspaceSize > MaxMetaspaceSize) {
109 FLAG_SET_ERGO(uintx, MetaspaceSize, MaxMetaspaceSize);
110 }
111
112 if (!is_size_aligned(MetaspaceSize, _min_alignment)) {
113 FLAG_SET_ERGO(uintx, MetaspaceSize,
114 restricted_align_down(MetaspaceSize, _min_alignment));
115 }
116
117 assert(MetaspaceSize <= MaxMetaspaceSize, "Must be");
118
119 MinMetaspaceExpansion = restricted_align_down(MinMetaspaceExpansion, _min_alignment);
120 MaxMetaspaceExpansion = restricted_align_down(MaxMetaspaceExpansion, _min_alignment);
121
122 MinHeapDeltaBytes = align_size_up(MinHeapDeltaBytes, _min_alignment);
123
124 assert(MetaspaceSize % _min_alignment == 0, "metapace alignment");
125 assert(MaxMetaspaceSize % _max_alignment == 0, "maximum metaspace alignment");
126 if (MetaspaceSize < 256*K) {
127 vm_exit_during_initialization("Too small initial Metaspace size");
128 }
129 }
130
131 void CollectorPolicy::initialize_size_info() {
132 _min_heap_byte_size = Arguments::min_heap_size();
133 _initial_heap_byte_size = InitialHeapSize;
134 _max_heap_byte_size = MaxHeapSize;
135
136 // Check heap parameter properties
137 if (_initial_heap_byte_size < M) {
138 vm_exit_during_initialization("Too small initial heap");
139 }
140 // Check heap parameter properties
141 if (_min_heap_byte_size < M) {
142 vm_exit_during_initialization("Too small minimum heap");
143 }
144
145 assert(_max_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible minimum and maximum heap sizes");
146 assert(_initial_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible initial and minimum heap sizes");
147 assert(_max_heap_byte_size >= _initial_heap_byte_size, "Ergonomics decided on incompatible initial and maximum heap sizes");
148 assert(_min_heap_byte_size % _min_alignment == 0, "min_heap_byte_size alignment");
149 assert(_initial_heap_byte_size % _min_alignment == 0, "initial_heap_byte_size alignment");
150 assert(_max_heap_byte_size % _max_alignment == 0, "max_heap_byte_size alignment");
151
152 if (PrintGCDetails && Verbose) {
153 gclog_or_tty->print_cr("Minimum heap " SIZE_FORMAT " Initial heap "
154 SIZE_FORMAT " Maximum heap " SIZE_FORMAT,
155 _min_heap_byte_size, _initial_heap_byte_size, _max_heap_byte_size);
156 }
157 }
158
159 bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) {
160 bool result = _should_clear_all_soft_refs;
161 set_should_clear_all_soft_refs(false);
162 return result;
163 }
164
165 GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap,
166 int max_covered_regions) {
167 switch (rem_set_name()) {
168 case GenRemSet::CardTable: {
169 CardTableRS* res = new CardTableRS(whole_heap, max_covered_regions);
170 return res;
171 }
172 default:
173 guarantee(false, "unrecognized GenRemSet::Name");
174 return NULL;
175 }
176 }
177
178 void CollectorPolicy::cleared_all_soft_refs() {
179 // If near gc overhear limit, continue to clear SoftRefs. SoftRefs may
180 // have been cleared in the last collection but if the gc overhear
181 // limit continues to be near, SoftRefs should still be cleared.
182 if (size_policy() != NULL) {
183 _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near();
184 }
185 _all_soft_refs_clear = true;
186 }
187
188 size_t CollectorPolicy::compute_max_alignment() {
189 // The card marking array and the offset arrays for old generations are
190 // committed in os pages as well. Make sure they are entirely full (to
191 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
192 // byte entry and the os page size is 4096, the maximum heap size should
193 // be 512*4096 = 2MB aligned.
194
195 // There is only the GenRemSet in Hotspot and only the GenRemSet::CardTable
196 // is supported.
197 // Requirements of any new remembered set implementations must be added here.
198 size_t alignment = GenRemSet::max_alignment_constraint(GenRemSet::CardTable);
199
200 // Parallel GC does its own alignment of the generations to avoid requiring a
201 // large page (256M on some platforms) for the permanent generation. The
202 // other collectors should also be updated to do their own alignment and then
203 // this use of lcm() should be removed.
204 if (UseLargePages && !UseParallelGC) {
205 // in presence of large pages we have to make sure that our
206 // alignment is large page aware
207 alignment = lcm(os::large_page_size(), alignment);
208 }
209
210 return alignment;
211 }
212
213 // GenCollectorPolicy methods.
214
215 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {
216 size_t x = base_size / (NewRatio+1);
217 size_t new_gen_size = x > _min_alignment ?
218 align_size_down(x, _min_alignment) : _min_alignment;
219 return new_gen_size;
220 }
221
222 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,
223 size_t maximum_size) {
224 size_t alignment = _min_alignment;
225 size_t max_minus = maximum_size - alignment;
226 return desired_size < max_minus ? desired_size : max_minus;
227 }
228
229
230 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size,
231 size_t init_promo_size,
232 size_t init_survivor_size) {
233 const double max_gc_pause_sec = ((double) MaxGCPauseMillis)/1000.0;
234 _size_policy = new AdaptiveSizePolicy(init_eden_size,
235 init_promo_size,
236 init_survivor_size,
237 max_gc_pause_sec,
238 GCTimeRatio);
239 }
240
241 size_t GenCollectorPolicy::compute_max_alignment() {
242 // The card marking array and the offset arrays for old generations are
243 // committed in os pages as well. Make sure they are entirely full (to
244 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
245 // byte entry and the os page size is 4096, the maximum heap size should
246 // be 512*4096 = 2MB aligned.
247 size_t alignment = GenRemSet::max_alignment_constraint(rem_set_name());
248
249 // Parallel GC does its own alignment of the generations to avoid requiring a
250 // large page (256M on some platforms) for the permanent generation. The
251 // other collectors should also be updated to do their own alignment and then
252 // this use of lcm() should be removed.
253 if (UseLargePages && !UseParallelGC) {
254 // in presence of large pages we have to make sure that our
255 // alignment is large page aware
256 alignment = lcm(os::large_page_size(), alignment);
257 }
258
259 assert(alignment >= _min_alignment, "Must be");
260
261 return alignment;
262 }
263
264 void GenCollectorPolicy::initialize_flags() {
265 // All sizes must be multiples of the generation granularity.
266 _min_alignment = (uintx) Generation::GenGrain;
267 _max_alignment = compute_max_alignment();
268
269 CollectorPolicy::initialize_flags();
270
271 // This is the absolute minimum for the young generation. It has to hold two
272 // survivor areas and the eden. We set it here since it is used repeatedly
273 // throughout the initialization. However this is not necessarily the final
274 // value of _min_gen0_size.
275 _min_gen0_size = 3 * intra_heap_alignment();
276
277 // Make sure the heap is large enough for two generations.
278 uintx smallestHeapSize = _min_gen0_size + intra_heap_alignment();
279 if (MaxHeapSize < smallestHeapSize) {
280 FLAG_SET_ERGO(uintx, MaxHeapSize, align_size_up(smallestHeapSize, _max_alignment));
281 }
282
283 // All generational heaps have a youngest gen; handle those flags here.
284
285 if (FLAG_IS_CMDLINE(NewSize) && FLAG_IS_CMDLINE(MaxNewSize) && NewSize > MaxNewSize) {
286 vm_exit_during_initialization("Incompatible initial and maximum young gen sizes specified");
287 }
288
289 if (!FLAG_IS_DEFAULT(MaxNewSize)) {
290 uintx minNewSize = MAX2(_min_alignment, _min_gen0_size);
291
292 if (MaxNewSize >= MaxHeapSize) {
293 uintx smallerMaxNewSize = align_size_down(MaxHeapSize - _min_alignment, _min_alignment);
294 if (FLAG_IS_CMDLINE(MaxNewSize)) {
295 warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or greater than the entire "
296 "heap (" SIZE_FORMAT "k). A new max generation size of " SIZE_FORMAT "k will be used.",
297 MaxNewSize/K, MaxHeapSize/K, smallerMaxNewSize/K);
298 }
299 FLAG_SET_ERGO(uintx, MaxNewSize, smallerMaxNewSize);
300 if (NewSize > MaxNewSize) {
301 FLAG_SET_ERGO(uintx, NewSize, MaxNewSize);
302 }
303 } else if (MaxNewSize < minNewSize) {
304 FLAG_SET_ERGO(uintx, MaxNewSize, align_size_up(minNewSize, _min_alignment));
305 } else if (!is_size_aligned(MaxNewSize, _min_alignment)) {
306 FLAG_SET_ERGO(uintx, MaxNewSize, align_size_down(MaxNewSize, _min_alignment));
307 }
308 }
309
310 // Young space must be aligned and have room for eden + two survivors.
311 // We will silently increase the NewSize even if the user specified a smaller value.
312 uintx smallestNewSize = MAX2(align_size_up(_min_gen0_size, _min_alignment),
313 align_size_down(NewSize, _min_alignment));
314 if (smallestNewSize != NewSize) {
315 FLAG_SET_ERGO(uintx, NewSize, smallestNewSize);
316 }
317
318 if (NewSize > MaxNewSize) {
319 // At this point this should only happen if the user specifies a large NewSize or
320 // a small (but not too small) MaxNewSize.
321 if (FLAG_IS_CMDLINE(NewSize)) {
322 warning("NewSize (" SIZE_FORMAT "k) is greater than the MaxNewSize (" SIZE_FORMAT "k). "
323 "A new generation size of " SIZE_FORMAT "k will be used.",
324 NewSize/K, MaxNewSize/K, MaxNewSize/K);
325 }
326 FLAG_SET_ERGO(uintx, NewSize, MaxNewSize);
327 }
328
329 assert(InitialHeapSize <= MaxHeapSize, "Ergonomics decided on incompatible initial and maximum heap sizes");
330 assert(NewSize >= _min_gen0_size, "Ergonomics decided on a too small young gen size");
331 assert(NewSize <= MaxNewSize, "Ergonomics decided on incompatible initial and maximum young gen sizes");
332 assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize < MaxHeapSize, "Ergonomics decided on incompatible maximum young gen and heap sizes");
333 assert(InitialHeapSize % _min_alignment == 0, "InitialHeapSize alignment");
334 assert(MaxHeapSize % _max_alignment == 0, "MaxHeapSize alignment");
335 assert(NewSize % _min_alignment == 0, "NewSize alignment");
336 assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize % _min_alignment == 0, "MaxNewSize alignment");
337
338 if (SurvivorRatio < 1 || NewRatio < 1) {
339 vm_exit_during_initialization("Invalid young gen ratio specified");
340 }
341 }
342
343 void TwoGenerationCollectorPolicy::initialize_flags() {
344 GenCollectorPolicy::initialize_flags();
345
346 if (!is_size_aligned(OldSize, _min_alignment)) {
347 FLAG_SET_ERGO(uintx, OldSize, align_size_down(OldSize, _min_alignment));
348 }
349
350 if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(MaxHeapSize)) {
351 // NewRatio will be used later to set the young generation size so we use
352 // it to calculate how big the heap should be based on the requested OldSize
353 // and NewRatio.
354 assert(NewRatio > 0, "NewRatio should have been set up earlier");
355 size_t calculated_heapsize = (OldSize / NewRatio) * (NewRatio + 1);
356
357 calculated_heapsize = align_size_up(calculated_heapsize, _max_alignment);
358 FLAG_SET_ERGO(uintx, MaxHeapSize, calculated_heapsize);
359 FLAG_SET_ERGO(uintx, InitialHeapSize, calculated_heapsize);
360 }
361
362 // adjust max heap size if necessary
363 if (NewSize + OldSize > MaxHeapSize) {
364 if (_max_heap_size_cmdline) {
365 // Somebody has set a maximum heap size with the intention that we should not
366 // exceed it. Adjust New/OldSize as necessary.
367 uintx calculated_size = NewSize + OldSize;
368 double shrink_factor = (double) MaxHeapSize / calculated_size;
369 // align
370 FLAG_SET_ERGO(uintx, NewSize, MAX2(_min_gen0_size, (uintx)align_size_down((uintx)(NewSize * shrink_factor), _min_alignment)));
371
372 // OldSize is already aligned because above we aligned MaxHeapSize to
373 // _max_alignment, and we just made sure that NewSize is aligned to
374 // _min_alignment. In initialize_flags() we verified that _max_alignment
375 // is a multiple of _min_alignment.
376 FLAG_SET_ERGO(uintx, OldSize, MaxHeapSize - NewSize);
377 } else {
378 FLAG_SET_ERGO(uintx, MaxHeapSize, align_size_up(NewSize + OldSize, _max_alignment));
379 }
380 }
381
382 always_do_update_barrier = UseConcMarkSweepGC;
383
384 // Check validity of heap flags
385 assert(InitialHeapSize <= MaxHeapSize, "Ergonomics decided on incompatible initial and maximum heap sizes");
386 assert(NewSize >= _min_gen0_size, "Ergonomics decided on a too small young gen size");
387 assert(NewSize <= MaxNewSize, "Ergonomics decided on incompatible initial and maximum young gen sizes");
388 assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize < MaxHeapSize, "Ergonomics decided on incompatible maximum young gen and heap sizes");
389 assert(OldSize + NewSize <= MaxHeapSize, "Ergonomics decided on incompatible generation and heap sizes");
390 assert(InitialHeapSize % _min_alignment == 0, "InitialHeapSize alignment");
391 assert(MaxHeapSize % _max_alignment == 0, "MaxHeapSize alignment");
392 assert(NewSize % _min_alignment == 0, "NewSize alignment");
393 assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize % _min_alignment == 0, "MaxNewSize alignment");
394 assert(OldSize % _min_alignment == 0, "OldSize alignment");
395 }
396
397 // Values set on the command line win over any ergonomically
398 // set command line parameters.
399 // Ergonomic choice of parameters are done before this
400 // method is called. Values for command line parameters such as NewSize
401 // and MaxNewSize feed those ergonomic choices into this method.
402 // This method makes the final generation sizings consistent with
403 // themselves and with overall heap sizings.
404 // In the absence of explicitly set command line flags, policies
405 // such as the use of NewRatio are used to size the generation.
406 void GenCollectorPolicy::initialize_size_info() {
407 CollectorPolicy::initialize_size_info();
408
409 // _min_alignment is used for alignment within a generation.
410 // There is additional alignment done down stream for some
411 // collectors that sometimes causes unwanted rounding up of
412 // generations sizes.
413
414 // Determine maximum size of gen0
415
416 size_t max_new_size = 0;
417 if (!FLAG_IS_DEFAULT(MaxNewSize)) {
418 max_new_size = MaxNewSize;
419 } else {
420 max_new_size = scale_by_NewRatio_aligned(_max_heap_byte_size);
421 // Bound the maximum size by NewSize below (since it historically
422 // would have been NewSize and because the NewRatio calculation could
423 // yield a size that is too small) and bound it by MaxNewSize above.
424 // Ergonomics plays here by previously calculating the desired
425 // NewSize and MaxNewSize.
426 max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize);
427 }
428 assert(max_new_size > 0, "All paths should set max_new_size");
429
430 // Given the maximum gen0 size, determine the initial and
431 // minimum gen0 sizes.
432
433 if (_max_heap_byte_size == _min_heap_byte_size) {
434 // The maximum and minimum heap sizes are the same so
435 // the generations minimum and initial must be the
436 // same as its maximum.
437 _min_gen0_size = max_new_size;
438 _initial_gen0_size = max_new_size;
439 _max_gen0_size = max_new_size;
440 } else {
441 size_t desired_new_size = 0;
442 if (!FLAG_IS_DEFAULT(NewSize)) {
443 // If NewSize is set ergonomically (for example by cms), it
444 // would make sense to use it. If it is used, also use it
445 // to set the initial size. Although there is no reason
446 // the minimum size and the initial size have to be the same,
447 // the current implementation gets into trouble during the calculation
448 // of the tenured generation sizes if they are different.
449 // Note that this makes the initial size and the minimum size
450 // generally small compared to the NewRatio calculation.
451 _min_gen0_size = NewSize;
452 desired_new_size = NewSize;
453 max_new_size = MAX2(max_new_size, NewSize);
454 } else {
455 // For the case where NewSize is the default, use NewRatio
456 // to size the minimum and initial generation sizes.
457 // Use the default NewSize as the floor for these values. If
458 // NewRatio is overly large, the resulting sizes can be too
459 // small.
460 _min_gen0_size = MAX2(scale_by_NewRatio_aligned(_min_heap_byte_size), NewSize);
461 desired_new_size =
462 MAX2(scale_by_NewRatio_aligned(_initial_heap_byte_size), NewSize);
463 }
464
465 assert(_min_gen0_size > 0, "Sanity check");
466 _initial_gen0_size = desired_new_size;
467 _max_gen0_size = max_new_size;
468
469 // At this point the desirable initial and minimum sizes have been
470 // determined without regard to the maximum sizes.
471
472 // Bound the sizes by the corresponding overall heap sizes.
473 _min_gen0_size = bound_minus_alignment(_min_gen0_size, _min_heap_byte_size);
474 _initial_gen0_size = bound_minus_alignment(_initial_gen0_size, _initial_heap_byte_size);
475 _max_gen0_size = bound_minus_alignment(_max_gen0_size, _max_heap_byte_size);
476
477 // At this point all three sizes have been checked against the
478 // maximum sizes but have not been checked for consistency
479 // among the three.
480
481 // Final check min <= initial <= max
482 _min_gen0_size = MIN2(_min_gen0_size, _max_gen0_size);
483 _initial_gen0_size = MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size);
484 _min_gen0_size = MIN2(_min_gen0_size, _initial_gen0_size);
485 }
486
487 // Write back to flag if necessary
488 if (MaxNewSize != _min_gen0_size) {
489 FLAG_SET_ERGO(uintx, MaxNewSize, _max_gen0_size);
490 }
491 assert(MaxNewSize < MaxHeapSize, "Ergonomics decided on incompatible maximum young and heap sizes");
492 assert(_max_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible minimum and maximum heap sizes");
493 assert(_initial_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible initial and minimum heap sizes");
494 assert(_max_heap_byte_size >= _initial_heap_byte_size, "Ergonomics decided on incompatible initial and maximum heap sizes");
495 assert(_min_gen0_size <= _initial_gen0_size, "Ergonomics decided on incompatible minimum and initial young gen sizes");
496 assert(_initial_gen0_size <= _max_gen0_size, "Ergonomics decided on incompatible initial and maximum young gen sizes");
497 assert(_min_heap_byte_size % _min_alignment == 0, "min_heap_byte_size alignment");
498 assert(_initial_heap_byte_size % _min_alignment == 0, "initial_heap_byte_size alignment");
499 assert(_max_heap_byte_size % _max_alignment == 0, "max_heap_byte_size alignment");
500 assert(_min_gen0_size % _min_alignment == 0, "_min_gen0_size alignment");
501 assert(_initial_gen0_size % _min_alignment == 0, "_initial_gen0_size alignment");
502 assert(_max_gen0_size % _min_alignment == 0, "_max_gen0_size alignment");
503
504 if (PrintGCDetails && Verbose) {
505 gclog_or_tty->print_cr("1: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
506 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
507 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
508 }
509 }
510
511 // Call this method during the sizing of the gen1 to make
512 // adjustments to gen0 because of gen1 sizing policy. gen0 initially has
513 // the most freedom in sizing because it is done before the
514 // policy for gen1 is applied. Once gen1 policies have been applied,
515 // there may be conflicts in the shape of the heap and this method
516 // is used to make the needed adjustments. The application of the
517 // policies could be more sophisticated (iterative for example) but
518 // keeping it simple also seems a worthwhile goal.
519 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr,
520 size_t* gen1_size_ptr,
521 const size_t heap_size,
522 const size_t min_gen1_size) {
523 bool result = false;
524
525 if ((*gen1_size_ptr + *gen0_size_ptr) > heap_size) {
526 if ((heap_size < (*gen0_size_ptr + min_gen1_size)) &&
527 (heap_size >= min_gen1_size + _min_alignment)) {
528 // Adjust gen0 down to accommodate min_gen1_size
529 *gen0_size_ptr =
530 MAX2((uintx)align_size_down(heap_size - min_gen1_size, _min_alignment),
531 _min_alignment);
532 assert(*gen0_size_ptr > 0, "Min gen0 is too large");
533 result = true;
534 } else {
535 *gen1_size_ptr =
536 MAX2((uintx)align_size_down(heap_size - *gen0_size_ptr, _min_alignment),
537 _min_alignment);
538 }
539 }
540 return result;
541 }
542
543 // Minimum sizes of the generations may be different than
544 // the initial sizes. An inconsistency is permitted here
545 // in the total size that can be specified explicitly by
546 // command line specification of OldSize and NewSize and
547 // also a command line specification of -Xms. Issue a warning
548 // but allow the values to pass.
549
550 void TwoGenerationCollectorPolicy::initialize_size_info() {
551 GenCollectorPolicy::initialize_size_info();
552
553 // At this point the minimum, initial and maximum sizes
554 // of the overall heap and of gen0 have been determined.
555 // The maximum gen1 size can be determined from the maximum gen0
556 // and maximum heap size since no explicit flags exist
557 // for setting the gen1 maximum.
558 _max_gen1_size = MAX2(_max_heap_byte_size - _max_gen0_size, _min_alignment);
559
560 // If no explicit command line flag has been set for the
561 // gen1 size, use what is left for gen1.
562 if (!FLAG_IS_CMDLINE(OldSize)) {
563 // The user has not specified any value but the ergonomics
564 // may have chosen a value (which may or may not be consistent
565 // with the overall heap size). In either case make
566 // the minimum, maximum and initial sizes consistent
567 // with the gen0 sizes and the overall heap sizes.
568 _min_gen1_size = MAX2(_min_heap_byte_size - _min_gen0_size, _min_alignment);
569 _initial_gen1_size = MAX2(_initial_heap_byte_size - _initial_gen0_size, _min_alignment);
570 // _max_gen1_size has already been made consistent above
571 FLAG_SET_ERGO(uintx, OldSize, _initial_gen1_size);
572 } else {
573 // OldSize has been explicitly set on the command line. Use the
574 // OldSize and then determine the consequences.
575 _min_gen1_size = MIN2(OldSize, _min_heap_byte_size - _min_gen0_size);
576 _initial_gen1_size = OldSize;
577
578 // If the user has explicitly set an OldSize that is inconsistent
579 // with other command line flags, issue a warning.
580 // The generation minimums and the overall heap minimum should
581 // be within one heap alignment.
582 if ((_min_gen1_size + _min_gen0_size + _min_alignment) < _min_heap_byte_size) {
583 warning("Inconsistency between minimum heap size and minimum "
584 "generation sizes: using minimum heap = " SIZE_FORMAT,
585 _min_heap_byte_size);
586 }
587 if (OldSize > _max_gen1_size) {
588 warning("Inconsistency between maximum heap size and maximum "
589 "generation sizes: using maximum heap = " SIZE_FORMAT
590 " -XX:OldSize flag is being ignored",
591 _max_heap_byte_size);
592 }
593 // If there is an inconsistency between the OldSize and the minimum and/or
594 // initial size of gen0, since OldSize was explicitly set, OldSize wins.
595 if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size,
596 _min_heap_byte_size, _min_gen1_size)) {
597 if (PrintGCDetails && Verbose) {
598 gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
599 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
600 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
601 }
602 }
603 // The same as above for the old gen initial size
604 if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,
605 _initial_heap_byte_size, _initial_gen1_size)) {
606 if (PrintGCDetails && Verbose) {
607 gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
608 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
609 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
610 }
611 }
612 // update OldSize
613 FLAG_SET_ERGO(uintx, OldSize, _initial_gen1_size);
614 }
615
616 _min_gen1_size = MIN2(_min_gen1_size, _max_gen1_size);
617
618 // Make sure that min gen1 <= initial gen1 <= max gen1
619 _initial_gen1_size = MAX2(_initial_gen1_size, _min_gen1_size);
620 _initial_gen1_size = MIN2(_initial_gen1_size, _max_gen1_size);
621
622 // check
623 assert(_max_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible minimum and maximum heap sizes");
624 assert(_initial_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible initial and minimum heap sizes");
625 assert(_max_heap_byte_size >= _initial_heap_byte_size, "Ergonomics decided on incompatible initial and maximum heap sizes");
626 assert(_min_gen0_size <= _initial_gen0_size, "Ergonomics decided on incompatible minimum and initial young gen sizes");
627 assert(_initial_gen0_size <= _max_gen0_size, "Ergonomics decided on incompatible initial and maximum young gen sizes");
628 assert(_min_gen1_size <= _initial_gen1_size, "Ergonomics decided on incompatible minimum and initial old gen sizes");
629 assert(_initial_gen1_size <= _max_gen1_size, "Ergonomics decided on incompatible initial and maximum old gen sizes");
630 assert(_min_heap_byte_size % _min_alignment == 0, "min_heap_byte_size alignment");
631 assert(_initial_heap_byte_size % _min_alignment == 0, "initial_heap_byte_size alignment");
632 assert(_max_heap_byte_size % _max_alignment == 0, "max_heap_byte_size alignment");
633 assert(_min_gen0_size % _min_alignment == 0, "_min_gen0_size alignment");
634 assert(_initial_gen0_size % _min_alignment == 0, "_initial_gen0_size alignment");
635 assert(_max_gen0_size % _min_alignment == 0, "_max_gen0_size alignment");
636 assert(_max_gen1_size % _min_alignment == 0, "_max_gen1_size alignment");
637
638 assert(_max_heap_byte_size <= (_max_gen0_size + _max_gen1_size), "Total maximum heap sizes must be sum of generation maximum sizes");
639
640 if (PrintGCDetails && Verbose) {
641 gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 "
642 SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT,
643 _min_gen1_size, _initial_gen1_size, _max_gen1_size);
644 }
645 }
646
647 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
648 bool is_tlab,
649 bool* gc_overhead_limit_was_exceeded) {
650 GenCollectedHeap *gch = GenCollectedHeap::heap();
651
652 debug_only(gch->check_for_valid_allocation_state());
653 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
654
655 // In general gc_overhead_limit_was_exceeded should be false so
656 // set it so here and reset it to true only if the gc time
657 // limit is being exceeded as checked below.
658 *gc_overhead_limit_was_exceeded = false;
659
660 HeapWord* result = NULL;
661
662 // Loop until the allocation is satisfied, or unsatisfied after GC.
663 for (int try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) {
664 HandleMark hm; // discard any handles allocated in each iteration
665
666 // First allocation attempt is lock-free.
667 Generation *gen0 = gch->get_gen(0);
668 assert(gen0->supports_inline_contig_alloc(),
669 "Otherwise, must do alloc within heap lock");
670 if (gen0->should_allocate(size, is_tlab)) {
671 result = gen0->par_allocate(size, is_tlab);
672 if (result != NULL) {
673 assert(gch->is_in_reserved(result), "result not in heap");
674 return result;
675 }
676 }
677 unsigned int gc_count_before; // read inside the Heap_lock locked region
678 {
679 MutexLocker ml(Heap_lock);
680 if (PrintGC && Verbose) {
681 gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:"
682 " attempting locked slow path allocation");
683 }
684 // Note that only large objects get a shot at being
685 // allocated in later generations.
686 bool first_only = ! should_try_older_generation_allocation(size);
687
688 result = gch->attempt_allocation(size, is_tlab, first_only);
689 if (result != NULL) {
690 assert(gch->is_in_reserved(result), "result not in heap");
691 return result;
692 }
693
694 if (GC_locker::is_active_and_needs_gc()) {
695 if (is_tlab) {
696 return NULL; // Caller will retry allocating individual object
697 }
698 if (!gch->is_maximal_no_gc()) {
699 // Try and expand heap to satisfy request
700 result = expand_heap_and_allocate(size, is_tlab);
701 // result could be null if we are out of space
702 if (result != NULL) {
703 return result;
704 }
705 }
706
707 if (gclocker_stalled_count > GCLockerRetryAllocationCount) {
708 return NULL; // we didn't get to do a GC and we didn't get any memory
709 }
710
711 // If this thread is not in a jni critical section, we stall
712 // the requestor until the critical section has cleared and
713 // GC allowed. When the critical section clears, a GC is
714 // initiated by the last thread exiting the critical section; so
715 // we retry the allocation sequence from the beginning of the loop,
716 // rather than causing more, now probably unnecessary, GC attempts.
717 JavaThread* jthr = JavaThread::current();
718 if (!jthr->in_critical()) {
719 MutexUnlocker mul(Heap_lock);
720 // Wait for JNI critical section to be exited
721 GC_locker::stall_until_clear();
722 gclocker_stalled_count += 1;
723 continue;
724 } else {
725 if (CheckJNICalls) {
726 fatal("Possible deadlock due to allocating while"
727 " in jni critical section");
728 }
729 return NULL;
730 }
731 }
732
733 // Read the gc count while the heap lock is held.
734 gc_count_before = Universe::heap()->total_collections();
735 }
736
737 VM_GenCollectForAllocation op(size,
738 is_tlab,
739 gc_count_before);
740 VMThread::execute(&op);
741 if (op.prologue_succeeded()) {
742 result = op.result();
743 if (op.gc_locked()) {
744 assert(result == NULL, "must be NULL if gc_locked() is true");
745 continue; // retry and/or stall as necessary
746 }
747
748 // Allocation has failed and a collection
749 // has been done. If the gc time limit was exceeded the
750 // this time, return NULL so that an out-of-memory
751 // will be thrown. Clear gc_overhead_limit_exceeded
752 // so that the overhead exceeded does not persist.
753
754 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
755 const bool softrefs_clear = all_soft_refs_clear();
756
757 if (limit_exceeded && softrefs_clear) {
758 *gc_overhead_limit_was_exceeded = true;
759 size_policy()->set_gc_overhead_limit_exceeded(false);
760 if (op.result() != NULL) {
761 CollectedHeap::fill_with_object(op.result(), size);
762 }
763 return NULL;
764 }
765 assert(result == NULL || gch->is_in_reserved(result),
766 "result not in heap");
767 return result;
768 }
769
770 // Give a warning if we seem to be looping forever.
771 if ((QueuedAllocationWarningCount > 0) &&
772 (try_count % QueuedAllocationWarningCount == 0)) {
773 warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t"
774 " size=%d %s", try_count, size, is_tlab ? "(TLAB)" : "");
775 }
776 }
777 }
778
779 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size,
780 bool is_tlab) {
781 GenCollectedHeap *gch = GenCollectedHeap::heap();
782 HeapWord* result = NULL;
783 for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) {
784 Generation *gen = gch->get_gen(i);
785 if (gen->should_allocate(size, is_tlab)) {
786 result = gen->expand_and_allocate(size, is_tlab);
787 }
788 }
789 assert(result == NULL || gch->is_in_reserved(result), "result not in heap");
790 return result;
791 }
792
793 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size,
794 bool is_tlab) {
795 GenCollectedHeap *gch = GenCollectedHeap::heap();
796 GCCauseSetter x(gch, GCCause::_allocation_failure);
797 HeapWord* result = NULL;
798
799 assert(size != 0, "Precondition violated");
800 if (GC_locker::is_active_and_needs_gc()) {
801 // GC locker is active; instead of a collection we will attempt
802 // to expand the heap, if there's room for expansion.
803 if (!gch->is_maximal_no_gc()) {
804 result = expand_heap_and_allocate(size, is_tlab);
805 }
806 return result; // could be null if we are out of space
807 } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) {
808 // Do an incremental collection.
809 gch->do_collection(false /* full */,
810 false /* clear_all_soft_refs */,
811 size /* size */,
812 is_tlab /* is_tlab */,
813 number_of_generations() - 1 /* max_level */);
814 } else {
815 if (Verbose && PrintGCDetails) {
816 gclog_or_tty->print(" :: Trying full because partial may fail :: ");
817 }
818 // Try a full collection; see delta for bug id 6266275
819 // for the original code and why this has been simplified
820 // with from-space allocation criteria modified and
821 // such allocation moved out of the safepoint path.
822 gch->do_collection(true /* full */,
823 false /* clear_all_soft_refs */,
824 size /* size */,
825 is_tlab /* is_tlab */,
826 number_of_generations() - 1 /* max_level */);
827 }
828
829 result = gch->attempt_allocation(size, is_tlab, false /*first_only*/);
830
831 if (result != NULL) {
832 assert(gch->is_in_reserved(result), "result not in heap");
833 return result;
834 }
835
836 // OK, collection failed, try expansion.
837 result = expand_heap_and_allocate(size, is_tlab);
838 if (result != NULL) {
839 return result;
840 }
841
842 // If we reach this point, we're really out of memory. Try every trick
843 // we can to reclaim memory. Force collection of soft references. Force
844 // a complete compaction of the heap. Any additional methods for finding
845 // free memory should be here, especially if they are expensive. If this
846 // attempt fails, an OOM exception will be thrown.
847 {
848 UIntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
849
850 gch->do_collection(true /* full */,
851 true /* clear_all_soft_refs */,
852 size /* size */,
853 is_tlab /* is_tlab */,
854 number_of_generations() - 1 /* max_level */);
855 }
856
857 result = gch->attempt_allocation(size, is_tlab, false /* first_only */);
858 if (result != NULL) {
859 assert(gch->is_in_reserved(result), "result not in heap");
860 return result;
861 }
862
863 assert(!should_clear_all_soft_refs(),
864 "Flag should have been handled and cleared prior to this point");
865
866 // What else? We might try synchronous finalization later. If the total
867 // space available is large enough for the allocation, then a more
868 // complete compaction phase than we've tried so far might be
869 // appropriate.
870 return NULL;
871 }
872
873 MetaWord* CollectorPolicy::satisfy_failed_metadata_allocation(
874 ClassLoaderData* loader_data,
875 size_t word_size,
876 Metaspace::MetadataType mdtype) {
877 uint loop_count = 0;
878 uint gc_count = 0;
879 uint full_gc_count = 0;
880
881 assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock");
882
883 do {
884 MetaWord* result = NULL;
885 if (GC_locker::is_active_and_needs_gc()) {
886 // If the GC_locker is active, just expand and allocate.
887 // If that does not succeed, wait if this thread is not
888 // in a critical section itself.
889 result =
890 loader_data->metaspace_non_null()->expand_and_allocate(word_size,
891 mdtype);
892 if (result != NULL) {
893 return result;
894 }
895 JavaThread* jthr = JavaThread::current();
896 if (!jthr->in_critical()) {
897 // Wait for JNI critical section to be exited
898 GC_locker::stall_until_clear();
899 // The GC invoked by the last thread leaving the critical
900 // section will be a young collection and a full collection
901 // is (currently) needed for unloading classes so continue
902 // to the next iteration to get a full GC.
903 continue;
904 } else {
905 if (CheckJNICalls) {
906 fatal("Possible deadlock due to allocating while"
907 " in jni critical section");
908 }
909 return NULL;
910 }
911 }
912
913 { // Need lock to get self consistent gc_count's
914 MutexLocker ml(Heap_lock);
915 gc_count = Universe::heap()->total_collections();
916 full_gc_count = Universe::heap()->total_full_collections();
917 }
918
919 // Generate a VM operation
920 VM_CollectForMetadataAllocation op(loader_data,
921 word_size,
922 mdtype,
923 gc_count,
924 full_gc_count,
925 GCCause::_metadata_GC_threshold);
926 VMThread::execute(&op);
927
928 // If GC was locked out, try again. Check
929 // before checking success because the prologue
930 // could have succeeded and the GC still have
931 // been locked out.
932 if (op.gc_locked()) {
933 continue;
934 }
935
936 if (op.prologue_succeeded()) {
937 return op.result();
938 }
939 loop_count++;
940 if ((QueuedAllocationWarningCount > 0) &&
941 (loop_count % QueuedAllocationWarningCount == 0)) {
942 warning("satisfy_failed_metadata_allocation() retries %d times \n\t"
943 " size=%d", loop_count, word_size);
944 }
945 } while (true); // Until a GC is done
946 }
947
948 // Return true if any of the following is true:
949 // . the allocation won't fit into the current young gen heap
950 // . gc locker is occupied (jni critical section)
951 // . heap memory is tight -- the most recent previous collection
952 // was a full collection because a partial collection (would
953 // have) failed and is likely to fail again
954 bool GenCollectorPolicy::should_try_older_generation_allocation(
955 size_t word_size) const {
956 GenCollectedHeap* gch = GenCollectedHeap::heap();
957 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();
958 return (word_size > heap_word_size(gen0_capacity))
959 || GC_locker::is_active_and_needs_gc()
960 || gch->incremental_collection_failed();
961 }
962
963
964 //
965 // MarkSweepPolicy methods
966 //
967
968 MarkSweepPolicy::MarkSweepPolicy() {
969 initialize_all();
970 }
971
972 void MarkSweepPolicy::initialize_generations() {
973 _generations = NEW_C_HEAP_ARRAY3(GenerationSpecPtr, number_of_generations(), mtGC, 0, AllocFailStrategy::RETURN_NULL);
974 if (_generations == NULL) {
975 vm_exit_during_initialization("Unable to allocate gen spec");
976 }
977
978 if (UseParNewGC) {
979 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);
980 } else {
981 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);
982 }
983 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);
984
985 if (_generations[0] == NULL || _generations[1] == NULL) {
986 vm_exit_during_initialization("Unable to allocate gen spec");
987 }
988 }
989
990 void MarkSweepPolicy::initialize_gc_policy_counters() {
991 // initialize the policy counters - 2 collectors, 3 generations
992 if (UseParNewGC) {
993 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);
994 } else {
995 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
996 }
997 }