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 CollectorPolicy::CollectorPolicy() :
51 _space_alignment(0),
52 _heap_alignment(0),
53 _initial_heap_byte_size(InitialHeapSize),
54 _max_heap_byte_size(MaxHeapSize),
55 _min_heap_byte_size(Arguments::min_heap_size()),
56 _max_heap_size_cmdline(false),
57 _size_policy(NULL),
58 _should_clear_all_soft_refs(false),
59 _all_soft_refs_clear(false)
60 {}
61
62 #ifdef ASSERT
63 void CollectorPolicy::assert_flags() {
64 assert(InitialHeapSize <= MaxHeapSize, "Ergonomics decided on incompatible initial and maximum heap sizes");
65 assert(InitialHeapSize % _heap_alignment == 0, "InitialHeapSize alignment");
66 assert(MaxHeapSize % _heap_alignment == 0, "MaxHeapSize alignment");
67 }
68
69 void CollectorPolicy::assert_size_info() {
70 assert(InitialHeapSize == _initial_heap_byte_size, "Discrepancy between InitialHeapSize flag and local storage");
71 assert(MaxHeapSize == _max_heap_byte_size, "Discrepancy between MaxHeapSize flag and local storage");
72 assert(_max_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible minimum and maximum heap sizes");
73 assert(_initial_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible initial and minimum heap sizes");
74 assert(_max_heap_byte_size >= _initial_heap_byte_size, "Ergonomics decided on incompatible initial and maximum heap sizes");
75 assert(_min_heap_byte_size % _heap_alignment == 0, "min_heap_byte_size alignment");
76 assert(_initial_heap_byte_size % _heap_alignment == 0, "initial_heap_byte_size alignment");
77 assert(_max_heap_byte_size % _heap_alignment == 0, "max_heap_byte_size alignment");
78 }
79 #endif // ASSERT
80
81 void CollectorPolicy::initialize_flags() {
82 assert(_space_alignment != 0, "Space alignment not set up properly");
83 assert(_heap_alignment != 0, "Heap alignment not set up properly");
84 assert(_heap_alignment >= _space_alignment,
85 err_msg("heap_alignment: " SIZE_FORMAT " less than space_alignment: " SIZE_FORMAT,
86 _heap_alignment, _space_alignment));
87 assert(_heap_alignment % _space_alignment == 0,
88 err_msg("heap_alignment: " SIZE_FORMAT " not aligned by space_alignment: " SIZE_FORMAT,
89 _heap_alignment, _space_alignment));
90
91 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
92 if (FLAG_IS_CMDLINE(InitialHeapSize) && InitialHeapSize > MaxHeapSize) {
93 vm_exit_during_initialization("Initial heap size set to a larger value than the maximum heap size");
94 }
95 if (_min_heap_byte_size != 0 && MaxHeapSize < _min_heap_byte_size) {
96 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified");
97 }
98 _max_heap_size_cmdline = true;
99 }
100
101 // Check heap parameter properties
102 if (InitialHeapSize < M) {
103 vm_exit_during_initialization("Too small initial heap");
104 }
105 if (_min_heap_byte_size < M) {
106 vm_exit_during_initialization("Too small minimum heap");
107 }
108
109 // User inputs from -Xmx and -Xms must be aligned
110 _min_heap_byte_size = align_size_up(_min_heap_byte_size, _heap_alignment);
111 uintx aligned_initial_heap_size = align_size_up(InitialHeapSize, _heap_alignment);
112 uintx aligned_max_heap_size = align_size_up(MaxHeapSize, _heap_alignment);
113
114 // Write back to flags if the values changed
115 if (aligned_initial_heap_size != InitialHeapSize) {
116 FLAG_SET_ERGO(uintx, InitialHeapSize, aligned_initial_heap_size);
117 }
118 if (aligned_max_heap_size != MaxHeapSize) {
119 FLAG_SET_ERGO(uintx, MaxHeapSize, aligned_max_heap_size);
120 }
121
122 if (FLAG_IS_CMDLINE(InitialHeapSize) && _min_heap_byte_size != 0 &&
123 InitialHeapSize < _min_heap_byte_size) {
124 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified");
125 }
126 if (!FLAG_IS_DEFAULT(InitialHeapSize) && InitialHeapSize > MaxHeapSize) {
127 FLAG_SET_ERGO(uintx, MaxHeapSize, InitialHeapSize);
128 } else if (!FLAG_IS_DEFAULT(MaxHeapSize) && InitialHeapSize > MaxHeapSize) {
129 FLAG_SET_ERGO(uintx, InitialHeapSize, MaxHeapSize);
130 if (InitialHeapSize < _min_heap_byte_size) {
131 _min_heap_byte_size = InitialHeapSize;
132 }
133 }
134
135 _initial_heap_byte_size = InitialHeapSize;
136 _max_heap_byte_size = MaxHeapSize;
137
138 FLAG_SET_ERGO(uintx, MinHeapDeltaBytes, align_size_up(MinHeapDeltaBytes, _space_alignment));
139
140 DEBUG_ONLY(CollectorPolicy::assert_flags();)
141 }
142
143 void CollectorPolicy::initialize_size_info() {
144 if (PrintGCDetails && Verbose) {
145 gclog_or_tty->print_cr("Minimum heap " SIZE_FORMAT " Initial heap "
146 SIZE_FORMAT " Maximum heap " SIZE_FORMAT,
147 _min_heap_byte_size, _initial_heap_byte_size, _max_heap_byte_size);
148 }
149
150 DEBUG_ONLY(CollectorPolicy::assert_size_info();)
151 }
152
153 bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) {
154 bool result = _should_clear_all_soft_refs;
155 set_should_clear_all_soft_refs(false);
156 return result;
157 }
158
159 GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap,
160 int max_covered_regions) {
161 return new CardTableRS(whole_heap, max_covered_regions);
162 }
163
164 void CollectorPolicy::cleared_all_soft_refs() {
165 // If near gc overhear limit, continue to clear SoftRefs. SoftRefs may
166 // have been cleared in the last collection but if the gc overhear
167 // limit continues to be near, SoftRefs should still be cleared.
168 if (size_policy() != NULL) {
169 _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near();
170 }
171 _all_soft_refs_clear = true;
172 }
173
174 size_t CollectorPolicy::compute_heap_alignment() {
175 // The card marking array and the offset arrays for old generations are
176 // committed in os pages as well. Make sure they are entirely full (to
177 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
178 // byte entry and the os page size is 4096, the maximum heap size should
179 // be 512*4096 = 2MB aligned.
180
181 // There is only the GenRemSet in Hotspot and only the GenRemSet::CardTable
182 // is supported.
183 // Requirements of any new remembered set implementations must be added here.
184 size_t alignment = GenRemSet::max_alignment_constraint(GenRemSet::CardTable);
185
186 // Parallel GC does its own alignment of the generations to avoid requiring a
187 // large page (256M on some platforms) for the permanent generation. The
188 // other collectors should also be updated to do their own alignment and then
189 // this use of lcm() should be removed.
190 if (UseLargePages && !UseParallelGC) {
191 // In presence of large pages we have to make sure that our
192 // alignment is large page aware
193 alignment = lcm(os::large_page_size(), alignment);
194 }
195
196 return alignment;
197 }
198
199 // GenCollectorPolicy methods
200
201 GenCollectorPolicy::GenCollectorPolicy() :
202 _min_gen0_size(0),
203 _initial_gen0_size(0),
204 _max_gen0_size(0),
205 _gen_alignment(0),
206 _generations(NULL)
207 {}
208
209 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {
210 return align_size_down_bounded(base_size / (NewRatio + 1), _gen_alignment);
211 }
212
213 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,
214 size_t maximum_size) {
215 size_t max_minus = maximum_size - _gen_alignment;
216 return desired_size < max_minus ? desired_size : max_minus;
217 }
218
219
220 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size,
221 size_t init_promo_size,
222 size_t init_survivor_size) {
223 const double max_gc_pause_sec = ((double) MaxGCPauseMillis) / 1000.0;
224 _size_policy = new AdaptiveSizePolicy(init_eden_size,
225 init_promo_size,
226 init_survivor_size,
227 max_gc_pause_sec,
228 GCTimeRatio);
229 }
230
231 size_t GenCollectorPolicy::young_gen_size_lower_bound() {
232 // The young generation must be aligned and have room for eden + two survivors
233 return align_size_up(3 * _space_alignment, _gen_alignment);
234 }
235
236 #ifdef ASSERT
237 void GenCollectorPolicy::assert_flags() {
238 CollectorPolicy::assert_flags();
239 assert(NewSize >= _min_gen0_size, "Ergonomics decided on a too small young gen size");
240 assert(NewSize <= MaxNewSize, "Ergonomics decided on incompatible initial and maximum young gen sizes");
241 assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize < MaxHeapSize, "Ergonomics decided on incompatible maximum young gen and heap sizes");
242 assert(NewSize % _gen_alignment == 0, "NewSize alignment");
243 assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize % _gen_alignment == 0, "MaxNewSize alignment");
244 }
245
246 void TwoGenerationCollectorPolicy::assert_flags() {
247 GenCollectorPolicy::assert_flags();
248 assert(OldSize + NewSize <= MaxHeapSize, "Ergonomics decided on incompatible generation and heap sizes");
249 assert(OldSize % _gen_alignment == 0, "OldSize alignment");
250 }
251
252 void GenCollectorPolicy::assert_size_info() {
253 CollectorPolicy::assert_size_info();
254 // GenCollectorPolicy::initialize_size_info may update the MaxNewSize
255 assert(MaxNewSize < MaxHeapSize, "Ergonomics decided on incompatible maximum young and heap sizes");
256 assert(NewSize == _initial_gen0_size, "Discrepancy between NewSize flag and local storage");
257 assert(MaxNewSize == _max_gen0_size, "Discrepancy between MaxNewSize flag and local storage");
258 assert(_min_gen0_size <= _initial_gen0_size, "Ergonomics decided on incompatible minimum and initial young gen sizes");
259 assert(_initial_gen0_size <= _max_gen0_size, "Ergonomics decided on incompatible initial and maximum young gen sizes");
260 assert(_min_gen0_size % _gen_alignment == 0, "_min_gen0_size alignment");
261 assert(_initial_gen0_size % _gen_alignment == 0, "_initial_gen0_size alignment");
262 assert(_max_gen0_size % _gen_alignment == 0, "_max_gen0_size alignment");
263 }
264
265 void TwoGenerationCollectorPolicy::assert_size_info() {
266 GenCollectorPolicy::assert_size_info();
267 assert(OldSize == _initial_gen1_size, "Discrepancy between OldSize flag and local storage");
268 assert(_min_gen1_size <= _initial_gen1_size, "Ergonomics decided on incompatible minimum and initial old gen sizes");
269 assert(_initial_gen1_size <= _max_gen1_size, "Ergonomics decided on incompatible initial and maximum old gen sizes");
270 assert(_max_gen1_size % _gen_alignment == 0, "_max_gen1_size alignment");
271 assert(_initial_gen1_size % _gen_alignment == 0, "_initial_gen1_size alignment");
272 assert(_max_heap_byte_size <= (_max_gen0_size + _max_gen1_size), "Total maximum heap sizes must be sum of generation maximum sizes");
273 }
274 #endif // ASSERT
275
276 void GenCollectorPolicy::initialize_flags() {
277 CollectorPolicy::initialize_flags();
278
279 assert(_gen_alignment != 0, "Generation alignment not set up properly");
280 assert(_heap_alignment >= _gen_alignment,
281 err_msg("heap_alignment: " SIZE_FORMAT " less than gen_alignment: " SIZE_FORMAT,
282 _heap_alignment, _gen_alignment));
283 assert(_gen_alignment % _space_alignment == 0,
284 err_msg("gen_alignment: " SIZE_FORMAT " not aligned by space_alignment: " SIZE_FORMAT,
285 _gen_alignment, _space_alignment));
286 assert(_heap_alignment % _gen_alignment == 0,
287 err_msg("heap_alignment: " SIZE_FORMAT " not aligned by gen_alignment: " SIZE_FORMAT,
288 _heap_alignment, _gen_alignment));
289
290 // All generational heaps have a youngest gen; handle those flags here
291
292 // Make sure the heap is large enough for two generations
293 uintx smallest_new_size = young_gen_size_lower_bound();
294 uintx smallest_heap_size = align_size_up(smallest_new_size + align_size_up(_space_alignment, _gen_alignment),
295 _heap_alignment);
296 if (MaxHeapSize < smallest_heap_size) {
297 FLAG_SET_ERGO(uintx, MaxHeapSize, smallest_heap_size);
298 _max_heap_byte_size = MaxHeapSize;
299 }
300 // If needed, synchronize _min_heap_byte size and _initial_heap_byte_size
301 if (_min_heap_byte_size < smallest_heap_size) {
302 _min_heap_byte_size = smallest_heap_size;
303 if (InitialHeapSize < _min_heap_byte_size) {
304 FLAG_SET_ERGO(uintx, InitialHeapSize, smallest_heap_size);
305 _initial_heap_byte_size = smallest_heap_size;
306 }
307 }
308
309 // Now take the actual NewSize into account. We will silently increase NewSize
310 // if the user specified a smaller value.
311 smallest_new_size = MAX2(smallest_new_size, (uintx)align_size_down(NewSize, _gen_alignment));
312 if (smallest_new_size != NewSize) {
313 FLAG_SET_ERGO(uintx, NewSize, smallest_new_size);
314 }
315 _initial_gen0_size = NewSize;
316
317 if (!FLAG_IS_DEFAULT(MaxNewSize)) {
318 uintx min_new_size = MAX2(_gen_alignment, _min_gen0_size);
319
320 if (MaxNewSize >= MaxHeapSize) {
321 // Make sure there is room for an old generation
322 uintx smaller_max_new_size = MaxHeapSize - _gen_alignment;
323 if (FLAG_IS_CMDLINE(MaxNewSize)) {
324 warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or greater than the entire "
325 "heap (" SIZE_FORMAT "k). A new max generation size of " SIZE_FORMAT "k will be used.",
326 MaxNewSize/K, MaxHeapSize/K, smaller_max_new_size/K);
327 }
328 FLAG_SET_ERGO(uintx, MaxNewSize, smaller_max_new_size);
329 if (NewSize > MaxNewSize) {
330 FLAG_SET_ERGO(uintx, NewSize, MaxNewSize);
331 _initial_gen0_size = NewSize;
332 }
333 } else if (MaxNewSize < min_new_size) {
334 FLAG_SET_ERGO(uintx, MaxNewSize, min_new_size);
335 } else if (!is_size_aligned(MaxNewSize, _gen_alignment)) {
336 FLAG_SET_ERGO(uintx, MaxNewSize, align_size_down(MaxNewSize, _gen_alignment));
337 }
338 _max_gen0_size = MaxNewSize;
339 }
340
341 if (NewSize > MaxNewSize) {
342 // At this point this should only happen if the user specifies a large NewSize and/or
343 // a small (but not too small) MaxNewSize.
344 if (FLAG_IS_CMDLINE(MaxNewSize)) {
345 warning("NewSize (" SIZE_FORMAT "k) is greater than the MaxNewSize (" SIZE_FORMAT "k). "
346 "A new max generation size of " SIZE_FORMAT "k will be used.",
347 NewSize/K, MaxNewSize/K, NewSize/K);
348 }
349 FLAG_SET_ERGO(uintx, MaxNewSize, NewSize);
350 _max_gen0_size = MaxNewSize;
351 }
352
353 if (SurvivorRatio < 1 || NewRatio < 1) {
354 vm_exit_during_initialization("Invalid young gen ratio specified");
355 }
356
357 DEBUG_ONLY(GenCollectorPolicy::assert_flags();)
358 }
359
360 void TwoGenerationCollectorPolicy::initialize_flags() {
361 GenCollectorPolicy::initialize_flags();
362
363 if (!is_size_aligned(OldSize, _gen_alignment)) {
364 FLAG_SET_ERGO(uintx, OldSize, align_size_down(OldSize, _gen_alignment));
365 }
366
367 if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(MaxHeapSize)) {
368 // NewRatio will be used later to set the young generation size so we use
369 // it to calculate how big the heap should be based on the requested OldSize
370 // and NewRatio.
371 assert(NewRatio > 0, "NewRatio should have been set up earlier");
372 size_t calculated_heapsize = (OldSize / NewRatio) * (NewRatio + 1);
373
374 calculated_heapsize = align_size_up(calculated_heapsize, _heap_alignment);
375 FLAG_SET_ERGO(uintx, MaxHeapSize, calculated_heapsize);
376 _max_heap_byte_size = MaxHeapSize;
377 FLAG_SET_ERGO(uintx, InitialHeapSize, calculated_heapsize);
378 _initial_heap_byte_size = InitialHeapSize;
379 }
380
381 // Adjust NewSize and OldSize or MaxHeapSize to match each other
382 if (NewSize + OldSize > MaxHeapSize) {
383 if (_max_heap_size_cmdline) {
384 // Somebody has set a maximum heap size with the intention that we should not
385 // exceed it. Adjust New/OldSize as necessary.
386 uintx calculated_size = NewSize + OldSize;
387 double shrink_factor = (double) MaxHeapSize / calculated_size;
388 uintx smaller_new_size = align_size_down((uintx)(NewSize * shrink_factor), _gen_alignment);
389 FLAG_SET_ERGO(uintx, NewSize, MAX2(young_gen_size_lower_bound(), smaller_new_size));
390 _initial_gen0_size = NewSize;
391
392 // OldSize is already aligned because above we aligned MaxHeapSize to
393 // _heap_alignment, and we just made sure that NewSize is aligned to
394 // _gen_alignment. In initialize_flags() we verified that _heap_alignment
395 // is a multiple of _gen_alignment.
396 FLAG_SET_ERGO(uintx, OldSize, MaxHeapSize - NewSize);
397 } else {
398 FLAG_SET_ERGO(uintx, MaxHeapSize, align_size_up(NewSize + OldSize, _heap_alignment));
399 _max_heap_byte_size = MaxHeapSize;
400 }
401 }
402
403 always_do_update_barrier = UseConcMarkSweepGC;
404
405 DEBUG_ONLY(TwoGenerationCollectorPolicy::assert_flags();)
406 }
407
408 // Values set on the command line win over any ergonomically
409 // set command line parameters.
410 // Ergonomic choice of parameters are done before this
411 // method is called. Values for command line parameters such as NewSize
412 // and MaxNewSize feed those ergonomic choices into this method.
413 // This method makes the final generation sizings consistent with
414 // themselves and with overall heap sizings.
415 // In the absence of explicitly set command line flags, policies
416 // such as the use of NewRatio are used to size the generation.
417 void GenCollectorPolicy::initialize_size_info() {
418 CollectorPolicy::initialize_size_info();
419
420 // _space_alignment is used for alignment within a generation.
421 // There is additional alignment done down stream for some
422 // collectors that sometimes causes unwanted rounding up of
423 // generations sizes.
424
425 // Determine maximum size of gen0
426
427 size_t max_new_size = 0;
428 if (!FLAG_IS_DEFAULT(MaxNewSize)) {
429 max_new_size = MaxNewSize;
430 } else {
431 max_new_size = scale_by_NewRatio_aligned(_max_heap_byte_size);
432 // Bound the maximum size by NewSize below (since it historically
433 // would have been NewSize and because the NewRatio calculation could
434 // yield a size that is too small) and bound it by MaxNewSize above.
435 // Ergonomics plays here by previously calculating the desired
436 // NewSize and MaxNewSize.
437 max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize);
438 }
439 assert(max_new_size > 0, "All paths should set max_new_size");
440
441 // Given the maximum gen0 size, determine the initial and
442 // minimum gen0 sizes.
443
444 if (_max_heap_byte_size == _min_heap_byte_size) {
445 // The maximum and minimum heap sizes are the same so the generations
446 // minimum and initial must be the same as its maximum.
447 _min_gen0_size = max_new_size;
448 _initial_gen0_size = max_new_size;
449 _max_gen0_size = max_new_size;
450 } else {
451 size_t desired_new_size = 0;
452 if (!FLAG_IS_DEFAULT(NewSize)) {
453 // If NewSize is set ergonomically (for example by cms), it
454 // would make sense to use it. If it is used, also use it
455 // to set the initial size. Although there is no reason
456 // the minimum size and the initial size have to be the same,
457 // the current implementation gets into trouble during the calculation
458 // of the tenured generation sizes if they are different.
459 // Note that this makes the initial size and the minimum size
460 // generally small compared to the NewRatio calculation.
461 _min_gen0_size = NewSize;
462 desired_new_size = NewSize;
463 max_new_size = MAX2(max_new_size, NewSize);
464 } else {
465 // For the case where NewSize is the default, use NewRatio
466 // to size the minimum and initial generation sizes.
467 // Use the default NewSize as the floor for these values. If
468 // NewRatio is overly large, the resulting sizes can be too small.
469 _min_gen0_size = MAX2(scale_by_NewRatio_aligned(_min_heap_byte_size), NewSize);
470 desired_new_size =
471 MAX2(scale_by_NewRatio_aligned(_initial_heap_byte_size), NewSize);
472 }
473
474 assert(_min_gen0_size > 0, "Sanity check");
475 _initial_gen0_size = desired_new_size;
476 _max_gen0_size = max_new_size;
477
478 // At this point the desirable initial and minimum sizes have been
479 // determined without regard to the maximum sizes.
480
481 // Bound the sizes by the corresponding overall heap sizes.
482 _min_gen0_size = bound_minus_alignment(_min_gen0_size, _min_heap_byte_size);
483 _initial_gen0_size = bound_minus_alignment(_initial_gen0_size, _initial_heap_byte_size);
484 _max_gen0_size = bound_minus_alignment(_max_gen0_size, _max_heap_byte_size);
485
486 // At this point all three sizes have been checked against the
487 // maximum sizes but have not been checked for consistency among the three.
488
489 // Final check min <= initial <= max
490 _min_gen0_size = MIN2(_min_gen0_size, _max_gen0_size);
491 _initial_gen0_size = MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size);
492 _min_gen0_size = MIN2(_min_gen0_size, _initial_gen0_size);
493 }
494
495 // Write back to flags if necessary.
496 if (NewSize != _initial_gen0_size) {
497 FLAG_SET_ERGO(uintx, NewSize, _initial_gen0_size);
498 }
499
500 if (MaxNewSize != _max_gen0_size) {
501 FLAG_SET_ERGO(uintx, MaxNewSize, _max_gen0_size);
502 }
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 DEBUG_ONLY(GenCollectorPolicy::assert_size_info();)
511 }
512
513 // Call this method during the sizing of the gen1 to make
514 // adjustments to gen0 because of gen1 sizing policy. gen0 initially has
515 // the most freedom in sizing because it is done before the
516 // policy for gen1 is applied. Once gen1 policies have been applied,
517 // there may be conflicts in the shape of the heap and this method
518 // is used to make the needed adjustments. The application of the
519 // policies could be more sophisticated (iterative for example) but
520 // keeping it simple also seems a worthwhile goal.
521 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr,
522 size_t* gen1_size_ptr,
523 const size_t heap_size) {
524 bool result = false;
525
526 if ((*gen0_size_ptr + *gen1_size_ptr) > heap_size) {
527 uintx smallest_new_size = young_gen_size_lower_bound();
528 if ((heap_size < (*gen0_size_ptr + _min_gen1_size)) &&
529 (heap_size >= _min_gen1_size + smallest_new_size)) {
530 // Adjust gen0 down to accommodate _min_gen1_size
531 *gen0_size_ptr = align_size_down_bounded(heap_size - _min_gen1_size, _gen_alignment);
532 result = true;
533 } else {
534 *gen1_size_ptr = align_size_down_bounded(heap_size - *gen0_size_ptr, _gen_alignment);
535 }
536 }
537 return result;
538 }
539
540 // Minimum sizes of the generations may be different than
541 // the initial sizes. An inconsistency is permitted here
542 // in the total size that can be specified explicitly by
543 // command line specification of OldSize and NewSize and
544 // also a command line specification of -Xms. Issue a warning
545 // but allow the values to pass.
546
547 void TwoGenerationCollectorPolicy::initialize_size_info() {
548 GenCollectorPolicy::initialize_size_info();
549
550 // At this point the minimum, initial and maximum sizes
551 // of the overall heap and of gen0 have been determined.
552 // The maximum gen1 size can be determined from the maximum gen0
553 // and maximum heap size since no explicit flags exist
554 // for setting the gen1 maximum.
555 _max_gen1_size = MAX2(_max_heap_byte_size - _max_gen0_size, _gen_alignment);
556
557 // If no explicit command line flag has been set for the
558 // gen1 size, use what is left for gen1
559 if (!FLAG_IS_CMDLINE(OldSize)) {
560 // The user has not specified any value but the ergonomics
561 // may have chosen a value (which may or may not be consistent
562 // with the overall heap size). In either case make
563 // the minimum, maximum and initial sizes consistent
564 // with the gen0 sizes and the overall heap sizes.
565 _min_gen1_size = MAX2(_min_heap_byte_size - _min_gen0_size, _gen_alignment);
566 _initial_gen1_size = MAX2(_initial_heap_byte_size - _initial_gen0_size, _gen_alignment);
567 // _max_gen1_size has already been made consistent above
568 FLAG_SET_ERGO(uintx, OldSize, _initial_gen1_size);
569 } else {
570 // OldSize has been explicitly set on the command line. Use the
571 // OldSize and then determine the consequences.
572 _min_gen1_size = MIN2(OldSize, _min_heap_byte_size - _min_gen0_size);
573 _initial_gen1_size = OldSize;
574
575 // If the user has explicitly set an OldSize that is inconsistent
576 // with other command line flags, issue a warning.
577 // The generation minimums and the overall heap minimum should
578 // be within one generation alignment.
579 if ((_min_gen1_size + _min_gen0_size + _gen_alignment) < _min_heap_byte_size) {
580 warning("Inconsistency between minimum heap size and minimum "
581 "generation sizes: using minimum heap = " SIZE_FORMAT,
582 _min_heap_byte_size);
583 }
584 if (OldSize > _max_gen1_size) {
585 warning("Inconsistency between maximum heap size and maximum "
586 "generation sizes: using maximum heap = " SIZE_FORMAT
587 " -XX:OldSize flag is being ignored",
588 _max_heap_byte_size);
589 }
590 // If there is an inconsistency between the OldSize and the minimum and/or
591 // initial size of gen0, since OldSize was explicitly set, OldSize wins.
592 if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size, _min_heap_byte_size)) {
593 if (PrintGCDetails && Verbose) {
594 gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
595 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
596 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
597 }
598 }
599 // The same as above for the old gen initial size.
600 if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,
601 _initial_heap_byte_size)) {
602 if (PrintGCDetails && Verbose) {
603 gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
604 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
605 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
606 }
607 }
608 }
609
610 _min_gen1_size = MIN2(_min_gen1_size, _max_gen1_size);
611
612 // Make sure that min gen1 <= initial gen1 <= max gen1.
613 _initial_gen1_size = MAX2(_initial_gen1_size, _min_gen1_size);
614 _initial_gen1_size = MIN2(_initial_gen1_size, _max_gen1_size);
615
616 // Write back to flags if necessary
617 if (NewSize != _initial_gen0_size) {
618 FLAG_SET_ERGO(uintx, NewSize, _initial_gen0_size);
619 }
620
621 if (MaxNewSize != _max_gen0_size) {
622 FLAG_SET_ERGO(uintx, MaxNewSize, _max_gen0_size);
623 }
624
625 if (OldSize != _initial_gen1_size) {
626 FLAG_SET_ERGO(uintx, OldSize, _initial_gen1_size);
627 }
628
629 if (PrintGCDetails && Verbose) {
630 gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 "
631 SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT,
632 _min_gen1_size, _initial_gen1_size, _max_gen1_size);
633 }
634
635 DEBUG_ONLY(TwoGenerationCollectorPolicy::assert_size_info();)
636 }
637
638 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
639 bool is_tlab,
640 bool* gc_overhead_limit_was_exceeded) {
641 GenCollectedHeap *gch = GenCollectedHeap::heap();
642
643 debug_only(gch->check_for_valid_allocation_state());
644 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
645
646 // In general gc_overhead_limit_was_exceeded should be false so
647 // set it so here and reset it to true only if the gc time
648 // limit is being exceeded as checked below.
649 *gc_overhead_limit_was_exceeded = false;
650
651 HeapWord* result = NULL;
652
653 // Loop until the allocation is satisfied, or unsatisfied after GC.
654 for (int try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) {
655 HandleMark hm; // Discard any handles allocated in each iteration.
656
657 // First allocation attempt is lock-free.
658 Generation *gen0 = gch->get_gen(0);
659 assert(gen0->supports_inline_contig_alloc(),
660 "Otherwise, must do alloc within heap lock");
661 if (gen0->should_allocate(size, is_tlab)) {
662 result = gen0->par_allocate(size, is_tlab);
663 if (result != NULL) {
664 assert(gch->is_in_reserved(result), "result not in heap");
665 return result;
666 }
667 }
668 unsigned int gc_count_before; // Read inside the Heap_lock locked region.
669 {
670 MutexLocker ml(Heap_lock);
671 if (PrintGC && Verbose) {
672 gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:"
673 " attempting locked slow path allocation");
674 }
675 // Note that only large objects get a shot at being
676 // allocated in later generations.
677 bool first_only = ! should_try_older_generation_allocation(size);
678
679 result = gch->attempt_allocation(size, is_tlab, first_only);
680 if (result != NULL) {
681 assert(gch->is_in_reserved(result), "result not in heap");
682 return result;
683 }
684
685 if (GC_locker::is_active_and_needs_gc()) {
686 if (is_tlab) {
687 return NULL; // Caller will retry allocating individual object.
688 }
689 if (!gch->is_maximal_no_gc()) {
690 // Try and expand heap to satisfy request.
691 result = expand_heap_and_allocate(size, is_tlab);
692 // Result could be null if we are out of space.
693 if (result != NULL) {
694 return result;
695 }
696 }
697
698 if (gclocker_stalled_count > GCLockerRetryAllocationCount) {
699 return NULL; // We didn't get to do a GC and we didn't get any memory.
700 }
701
702 // If this thread is not in a jni critical section, we stall
703 // the requestor until the critical section has cleared and
704 // GC allowed. When the critical section clears, a GC is
705 // initiated by the last thread exiting the critical section; so
706 // we retry the allocation sequence from the beginning of the loop,
707 // rather than causing more, now probably unnecessary, GC attempts.
708 JavaThread* jthr = JavaThread::current();
709 if (!jthr->in_critical()) {
710 MutexUnlocker mul(Heap_lock);
711 // Wait for JNI critical section to be exited
712 GC_locker::stall_until_clear();
713 gclocker_stalled_count += 1;
714 continue;
715 } else {
716 if (CheckJNICalls) {
717 fatal("Possible deadlock due to allocating while"
718 " in jni critical section");
719 }
720 return NULL;
721 }
722 }
723
724 // Read the gc count while the heap lock is held.
725 gc_count_before = Universe::heap()->total_collections();
726 }
727
728 VM_GenCollectForAllocation op(size, is_tlab, gc_count_before);
729 VMThread::execute(&op);
730 if (op.prologue_succeeded()) {
731 result = op.result();
732 if (op.gc_locked()) {
733 assert(result == NULL, "must be NULL if gc_locked() is true");
734 continue; // Retry and/or stall as necessary.
735 }
736
737 // Allocation has failed and a collection
738 // has been done. If the gc time limit was exceeded the
739 // this time, return NULL so that an out-of-memory
740 // will be thrown. Clear gc_overhead_limit_exceeded
741 // so that the overhead exceeded does not persist.
742
743 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
744 const bool softrefs_clear = all_soft_refs_clear();
745
746 if (limit_exceeded && softrefs_clear) {
747 *gc_overhead_limit_was_exceeded = true;
748 size_policy()->set_gc_overhead_limit_exceeded(false);
749 if (op.result() != NULL) {
750 CollectedHeap::fill_with_object(op.result(), size);
751 }
752 return NULL;
753 }
754 assert(result == NULL || gch->is_in_reserved(result),
755 "result not in heap");
756 return result;
757 }
758
759 // Give a warning if we seem to be looping forever.
760 if ((QueuedAllocationWarningCount > 0) &&
761 (try_count % QueuedAllocationWarningCount == 0)) {
762 warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t"
763 " size=%d %s", try_count, size, is_tlab ? "(TLAB)" : "");
764 }
765 }
766 }
767
768 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size,
769 bool is_tlab) {
770 GenCollectedHeap *gch = GenCollectedHeap::heap();
771 HeapWord* result = NULL;
772 for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) {
773 Generation *gen = gch->get_gen(i);
774 if (gen->should_allocate(size, is_tlab)) {
775 result = gen->expand_and_allocate(size, is_tlab);
776 }
777 }
778 assert(result == NULL || gch->is_in_reserved(result), "result not in heap");
779 return result;
780 }
781
782 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size,
783 bool is_tlab) {
784 GenCollectedHeap *gch = GenCollectedHeap::heap();
785 GCCauseSetter x(gch, GCCause::_allocation_failure);
786 HeapWord* result = NULL;
787
788 assert(size != 0, "Precondition violated");
789 if (GC_locker::is_active_and_needs_gc()) {
790 // GC locker is active; instead of a collection we will attempt
791 // to expand the heap, if there's room for expansion.
792 if (!gch->is_maximal_no_gc()) {
793 result = expand_heap_and_allocate(size, is_tlab);
794 }
795 return result; // Could be null if we are out of space.
796 } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) {
797 // Do an incremental collection.
798 gch->do_collection(false /* full */,
799 false /* clear_all_soft_refs */,
800 size /* size */,
801 is_tlab /* is_tlab */,
802 number_of_generations() - 1 /* max_level */);
803 } else {
804 if (Verbose && PrintGCDetails) {
805 gclog_or_tty->print(" :: Trying full because partial may fail :: ");
806 }
807 // Try a full collection; see delta for bug id 6266275
808 // for the original code and why this has been simplified
809 // with from-space allocation criteria modified and
810 // such allocation moved out of the safepoint path.
811 gch->do_collection(true /* full */,
812 false /* clear_all_soft_refs */,
813 size /* size */,
814 is_tlab /* is_tlab */,
815 number_of_generations() - 1 /* max_level */);
816 }
817
818 result = gch->attempt_allocation(size, is_tlab, false /*first_only*/);
819
820 if (result != NULL) {
821 assert(gch->is_in_reserved(result), "result not in heap");
822 return result;
823 }
824
825 // OK, collection failed, try expansion.
826 result = expand_heap_and_allocate(size, is_tlab);
827 if (result != NULL) {
828 return result;
829 }
830
831 // If we reach this point, we're really out of memory. Try every trick
832 // we can to reclaim memory. Force collection of soft references. Force
833 // a complete compaction of the heap. Any additional methods for finding
834 // free memory should be here, especially if they are expensive. If this
835 // attempt fails, an OOM exception will be thrown.
836 {
837 UIntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
838
839 gch->do_collection(true /* full */,
840 true /* clear_all_soft_refs */,
841 size /* size */,
842 is_tlab /* is_tlab */,
843 number_of_generations() - 1 /* max_level */);
844 }
845
846 result = gch->attempt_allocation(size, is_tlab, false /* first_only */);
847 if (result != NULL) {
848 assert(gch->is_in_reserved(result), "result not in heap");
849 return result;
850 }
851
852 assert(!should_clear_all_soft_refs(),
853 "Flag should have been handled and cleared prior to this point");
854
855 // What else? We might try synchronous finalization later. If the total
856 // space available is large enough for the allocation, then a more
857 // complete compaction phase than we've tried so far might be
858 // appropriate.
859 return NULL;
860 }
861
862 MetaWord* CollectorPolicy::satisfy_failed_metadata_allocation(
863 ClassLoaderData* loader_data,
864 size_t word_size,
865 Metaspace::MetadataType mdtype) {
866 uint loop_count = 0;
867 uint gc_count = 0;
868 uint full_gc_count = 0;
869
870 assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock");
871
872 do {
873 MetaWord* result = NULL;
874 if (GC_locker::is_active_and_needs_gc()) {
875 // If the GC_locker is active, just expand and allocate.
876 // If that does not succeed, wait if this thread is not
877 // in a critical section itself.
878 result =
879 loader_data->metaspace_non_null()->expand_and_allocate(word_size,
880 mdtype);
881 if (result != NULL) {
882 return result;
883 }
884 JavaThread* jthr = JavaThread::current();
885 if (!jthr->in_critical()) {
886 // Wait for JNI critical section to be exited
887 GC_locker::stall_until_clear();
888 // The GC invoked by the last thread leaving the critical
889 // section will be a young collection and a full collection
890 // is (currently) needed for unloading classes so continue
891 // to the next iteration to get a full GC.
892 continue;
893 } else {
894 if (CheckJNICalls) {
895 fatal("Possible deadlock due to allocating while"
896 " in jni critical section");
897 }
898 return NULL;
899 }
900 }
901
902 { // Need lock to get self consistent gc_count's
903 MutexLocker ml(Heap_lock);
904 gc_count = Universe::heap()->total_collections();
905 full_gc_count = Universe::heap()->total_full_collections();
906 }
907
908 // Generate a VM operation
909 VM_CollectForMetadataAllocation op(loader_data,
910 word_size,
911 mdtype,
912 gc_count,
913 full_gc_count,
914 GCCause::_metadata_GC_threshold);
915 VMThread::execute(&op);
916
917 // If GC was locked out, try again. Check before checking success because the
918 // prologue could have succeeded and the GC still have been locked out.
919 if (op.gc_locked()) {
920 continue;
921 }
922
923 if (op.prologue_succeeded()) {
924 return op.result();
925 }
926 loop_count++;
927 if ((QueuedAllocationWarningCount > 0) &&
928 (loop_count % QueuedAllocationWarningCount == 0)) {
929 warning("satisfy_failed_metadata_allocation() retries %d times \n\t"
930 " size=%d", loop_count, word_size);
931 }
932 } while (true); // Until a GC is done
933 }
934
935 // Return true if any of the following is true:
936 // . the allocation won't fit into the current young gen heap
937 // . gc locker is occupied (jni critical section)
938 // . heap memory is tight -- the most recent previous collection
939 // was a full collection because a partial collection (would
940 // have) failed and is likely to fail again
941 bool GenCollectorPolicy::should_try_older_generation_allocation(
942 size_t word_size) const {
943 GenCollectedHeap* gch = GenCollectedHeap::heap();
944 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();
945 return (word_size > heap_word_size(gen0_capacity))
946 || GC_locker::is_active_and_needs_gc()
947 || gch->incremental_collection_failed();
948 }
949
950
951 //
952 // MarkSweepPolicy methods
953 //
954
955 void MarkSweepPolicy::initialize_alignments() {
956 _space_alignment = _gen_alignment = (uintx)Generation::GenGrain;
957 _heap_alignment = compute_heap_alignment();
958 }
959
960 void MarkSweepPolicy::initialize_generations() {
961 _generations = NEW_C_HEAP_ARRAY3(GenerationSpecPtr, number_of_generations(), mtGC, 0, AllocFailStrategy::RETURN_NULL);
962 if (_generations == NULL) {
963 vm_exit_during_initialization("Unable to allocate gen spec");
964 }
965
966 if (UseParNewGC) {
967 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);
968 } else {
969 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);
970 }
971 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);
972
973 if (_generations[0] == NULL || _generations[1] == NULL) {
974 vm_exit_during_initialization("Unable to allocate gen spec");
975 }
976 }
977
978 void MarkSweepPolicy::initialize_gc_policy_counters() {
979 // Initialize the policy counters - 2 collectors, 3 generations.
980 if (UseParNewGC) {
981 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);
982 } else {
983 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
984 }
985 }