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