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 size_t alignment = GenRemSet::max_alignment_constraint();
182
183 // Parallel GC does its own alignment of the generations to avoid requiring a
184 // large page (256M on some platforms) for the permanent generation. The
185 // other collectors should also be updated to do their own alignment and then
186 // this use of lcm() should be removed.
187 if (UseLargePages && !UseParallelGC) {
188 // In presence of large pages we have to make sure that our
189 // alignment is large page aware
190 alignment = lcm(os::large_page_size(), alignment);
191 }
192
193 return alignment;
194 }
195
196 // GenCollectorPolicy methods
197
198 GenCollectorPolicy::GenCollectorPolicy() :
199 _min_gen0_size(0),
200 _initial_gen0_size(0),
201 _max_gen0_size(0),
202 _gen_alignment(0),
203 _generations(NULL)
204 {}
205
206 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {
207 return align_size_down_bounded(base_size / (NewRatio + 1), _gen_alignment);
208 }
209
210 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,
211 size_t maximum_size) {
212 size_t max_minus = maximum_size - _gen_alignment;
213 return desired_size < max_minus ? desired_size : max_minus;
214 }
215
216
217 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size,
218 size_t init_promo_size,
219 size_t init_survivor_size) {
220 const double max_gc_pause_sec = ((double) MaxGCPauseMillis) / 1000.0;
221 _size_policy = new AdaptiveSizePolicy(init_eden_size,
222 init_promo_size,
223 init_survivor_size,
224 max_gc_pause_sec,
225 GCTimeRatio);
226 }
227
228 size_t GenCollectorPolicy::young_gen_size_lower_bound() {
229 // The young generation must be aligned and have room for eden + two survivors
230 return align_size_up(3 * _space_alignment, _gen_alignment);
231 }
232
233 #ifdef ASSERT
234 void GenCollectorPolicy::assert_flags() {
235 CollectorPolicy::assert_flags();
236 assert(NewSize >= _min_gen0_size, "Ergonomics decided on a too small young gen size");
237 assert(NewSize <= MaxNewSize, "Ergonomics decided on incompatible initial and maximum young gen sizes");
238 assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize < MaxHeapSize, "Ergonomics decided on incompatible maximum young gen and heap sizes");
239 assert(NewSize % _gen_alignment == 0, "NewSize alignment");
240 assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize % _gen_alignment == 0, "MaxNewSize alignment");
241 }
242
243 void TwoGenerationCollectorPolicy::assert_flags() {
244 GenCollectorPolicy::assert_flags();
245 assert(OldSize + NewSize <= MaxHeapSize, "Ergonomics decided on incompatible generation and heap sizes");
246 assert(OldSize % _gen_alignment == 0, "OldSize alignment");
247 }
248
249 void GenCollectorPolicy::assert_size_info() {
250 CollectorPolicy::assert_size_info();
251 // GenCollectorPolicy::initialize_size_info may update the MaxNewSize
252 assert(MaxNewSize < MaxHeapSize, "Ergonomics decided on incompatible maximum young and heap sizes");
253 assert(NewSize == _initial_gen0_size, "Discrepancy between NewSize flag and local storage");
254 assert(MaxNewSize == _max_gen0_size, "Discrepancy between MaxNewSize flag and local storage");
255 assert(_min_gen0_size <= _initial_gen0_size, "Ergonomics decided on incompatible minimum and initial young gen sizes");
256 assert(_initial_gen0_size <= _max_gen0_size, "Ergonomics decided on incompatible initial and maximum young gen sizes");
257 assert(_min_gen0_size % _gen_alignment == 0, "_min_gen0_size alignment");
258 assert(_initial_gen0_size % _gen_alignment == 0, "_initial_gen0_size alignment");
259 assert(_max_gen0_size % _gen_alignment == 0, "_max_gen0_size alignment");
260 }
261
262 void TwoGenerationCollectorPolicy::assert_size_info() {
263 GenCollectorPolicy::assert_size_info();
264 assert(OldSize == _initial_gen1_size, "Discrepancy between OldSize flag and local storage");
265 assert(_min_gen1_size <= _initial_gen1_size, "Ergonomics decided on incompatible minimum and initial old gen sizes");
266 assert(_initial_gen1_size <= _max_gen1_size, "Ergonomics decided on incompatible initial and maximum old gen sizes");
267 assert(_max_gen1_size % _gen_alignment == 0, "_max_gen1_size alignment");
268 assert(_initial_gen1_size % _gen_alignment == 0, "_initial_gen1_size alignment");
269 assert(_max_heap_byte_size <= (_max_gen0_size + _max_gen1_size), "Total maximum heap sizes must be sum of generation maximum sizes");
270 }
271 #endif // ASSERT
272
273 void GenCollectorPolicy::initialize_flags() {
274 CollectorPolicy::initialize_flags();
275
276 assert(_gen_alignment != 0, "Generation alignment not set up properly");
277 assert(_heap_alignment >= _gen_alignment,
278 err_msg("heap_alignment: " SIZE_FORMAT " less than gen_alignment: " SIZE_FORMAT,
279 _heap_alignment, _gen_alignment));
280 assert(_gen_alignment % _space_alignment == 0,
281 err_msg("gen_alignment: " SIZE_FORMAT " not aligned by space_alignment: " SIZE_FORMAT,
282 _gen_alignment, _space_alignment));
283 assert(_heap_alignment % _gen_alignment == 0,
284 err_msg("heap_alignment: " SIZE_FORMAT " not aligned by gen_alignment: " SIZE_FORMAT,
285 _heap_alignment, _gen_alignment));
286
287 // All generational heaps have a youngest gen; handle those flags here
288
289 // Make sure the heap is large enough for two generations
290 uintx smallest_new_size = young_gen_size_lower_bound();
291 uintx smallest_heap_size = align_size_up(smallest_new_size + align_size_up(_space_alignment, _gen_alignment),
292 _heap_alignment);
293 if (MaxHeapSize < smallest_heap_size) {
294 FLAG_SET_ERGO(uintx, MaxHeapSize, smallest_heap_size);
295 _max_heap_byte_size = MaxHeapSize;
296 }
297 // If needed, synchronize _min_heap_byte size and _initial_heap_byte_size
298 if (_min_heap_byte_size < smallest_heap_size) {
299 _min_heap_byte_size = smallest_heap_size;
300 if (InitialHeapSize < _min_heap_byte_size) {
301 FLAG_SET_ERGO(uintx, InitialHeapSize, smallest_heap_size);
302 _initial_heap_byte_size = smallest_heap_size;
303 }
304 }
305
306 // Now take the actual NewSize into account. We will silently increase NewSize
307 // if the user specified a smaller value.
308 smallest_new_size = MAX2(smallest_new_size, (uintx)align_size_down(NewSize, _gen_alignment));
309 if (smallest_new_size != NewSize) {
310 FLAG_SET_ERGO(uintx, NewSize, smallest_new_size);
311 }
312 _initial_gen0_size = NewSize;
313
314 if (!FLAG_IS_DEFAULT(MaxNewSize)) {
315 uintx min_new_size = MAX2(_gen_alignment, _min_gen0_size);
316
317 if (MaxNewSize >= MaxHeapSize) {
318 // Make sure there is room for an old generation
319 uintx smaller_max_new_size = MaxHeapSize - _gen_alignment;
320 if (FLAG_IS_CMDLINE(MaxNewSize)) {
321 warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or greater than the entire "
322 "heap (" SIZE_FORMAT "k). A new max generation size of " SIZE_FORMAT "k will be used.",
323 MaxNewSize/K, MaxHeapSize/K, smaller_max_new_size/K);
324 }
325 FLAG_SET_ERGO(uintx, MaxNewSize, smaller_max_new_size);
326 if (NewSize > MaxNewSize) {
327 FLAG_SET_ERGO(uintx, NewSize, MaxNewSize);
328 _initial_gen0_size = NewSize;
329 }
330 } else if (MaxNewSize < min_new_size) {
331 FLAG_SET_ERGO(uintx, MaxNewSize, min_new_size);
332 } else if (!is_size_aligned(MaxNewSize, _gen_alignment)) {
333 FLAG_SET_ERGO(uintx, MaxNewSize, align_size_down(MaxNewSize, _gen_alignment));
334 }
335 _max_gen0_size = MaxNewSize;
336 }
337
338 if (NewSize > MaxNewSize) {
339 // At this point this should only happen if the user specifies a large NewSize and/or
340 // a small (but not too small) MaxNewSize.
341 if (FLAG_IS_CMDLINE(MaxNewSize)) {
342 warning("NewSize (" SIZE_FORMAT "k) is greater than the MaxNewSize (" SIZE_FORMAT "k). "
343 "A new max generation size of " SIZE_FORMAT "k will be used.",
344 NewSize/K, MaxNewSize/K, NewSize/K);
345 }
346 FLAG_SET_ERGO(uintx, MaxNewSize, NewSize);
347 _max_gen0_size = MaxNewSize;
348 }
349
350 if (SurvivorRatio < 1 || NewRatio < 1) {
351 vm_exit_during_initialization("Invalid young gen ratio specified");
352 }
353
354 DEBUG_ONLY(GenCollectorPolicy::assert_flags();)
355 }
356
357 void TwoGenerationCollectorPolicy::initialize_flags() {
358 GenCollectorPolicy::initialize_flags();
359
360 if (!is_size_aligned(OldSize, _gen_alignment)) {
361 FLAG_SET_ERGO(uintx, OldSize, align_size_down(OldSize, _gen_alignment));
362 }
363
364 if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(MaxHeapSize)) {
365 // NewRatio will be used later to set the young generation size so we use
366 // it to calculate how big the heap should be based on the requested OldSize
367 // and NewRatio.
368 assert(NewRatio > 0, "NewRatio should have been set up earlier");
369 size_t calculated_heapsize = (OldSize / NewRatio) * (NewRatio + 1);
370
371 calculated_heapsize = align_size_up(calculated_heapsize, _heap_alignment);
372 FLAG_SET_ERGO(uintx, MaxHeapSize, calculated_heapsize);
373 _max_heap_byte_size = MaxHeapSize;
374 FLAG_SET_ERGO(uintx, InitialHeapSize, calculated_heapsize);
375 _initial_heap_byte_size = InitialHeapSize;
376 }
377
378 // Adjust NewSize and OldSize or MaxHeapSize to match each other
379 if (NewSize + OldSize > MaxHeapSize) {
380 if (_max_heap_size_cmdline) {
381 // Somebody has set a maximum heap size with the intention that we should not
382 // exceed it. Adjust New/OldSize as necessary.
383 uintx calculated_size = NewSize + OldSize;
384 double shrink_factor = (double) MaxHeapSize / calculated_size;
385 uintx smaller_new_size = align_size_down((uintx)(NewSize * shrink_factor), _gen_alignment);
386 FLAG_SET_ERGO(uintx, NewSize, MAX2(young_gen_size_lower_bound(), smaller_new_size));
387 _initial_gen0_size = NewSize;
388
389 // OldSize is already aligned because above we aligned MaxHeapSize to
390 // _heap_alignment, and we just made sure that NewSize is aligned to
391 // _gen_alignment. In initialize_flags() we verified that _heap_alignment
392 // is a multiple of _gen_alignment.
393 FLAG_SET_ERGO(uintx, OldSize, MaxHeapSize - NewSize);
394 } else {
395 FLAG_SET_ERGO(uintx, MaxHeapSize, align_size_up(NewSize + OldSize, _heap_alignment));
396 _max_heap_byte_size = MaxHeapSize;
397 }
398 }
399
400 always_do_update_barrier = UseConcMarkSweepGC;
401
402 DEBUG_ONLY(TwoGenerationCollectorPolicy::assert_flags();)
403 }
404
405 // Values set on the command line win over any ergonomically
406 // set command line parameters.
407 // Ergonomic choice of parameters are done before this
408 // method is called. Values for command line parameters such as NewSize
409 // and MaxNewSize feed those ergonomic choices into this method.
410 // This method makes the final generation sizings consistent with
411 // themselves and with overall heap sizings.
412 // In the absence of explicitly set command line flags, policies
413 // such as the use of NewRatio are used to size the generation.
414 void GenCollectorPolicy::initialize_size_info() {
415 CollectorPolicy::initialize_size_info();
416
417 // _space_alignment is used for alignment within a generation.
418 // There is additional alignment done down stream for some
419 // collectors that sometimes causes unwanted rounding up of
420 // generations sizes.
421
422 // Determine maximum size of gen0
423
424 size_t max_new_size = 0;
425 if (!FLAG_IS_DEFAULT(MaxNewSize)) {
426 max_new_size = MaxNewSize;
427 } else {
428 max_new_size = scale_by_NewRatio_aligned(_max_heap_byte_size);
429 // Bound the maximum size by NewSize below (since it historically
430 // would have been NewSize and because the NewRatio calculation could
431 // yield a size that is too small) and bound it by MaxNewSize above.
432 // Ergonomics plays here by previously calculating the desired
433 // NewSize and MaxNewSize.
434 max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize);
435 }
436 assert(max_new_size > 0, "All paths should set max_new_size");
437
438 // Given the maximum gen0 size, determine the initial and
439 // minimum gen0 sizes.
440
441 if (_max_heap_byte_size == _min_heap_byte_size) {
442 // The maximum and minimum heap sizes are the same so the generations
443 // minimum and initial must be the same as its maximum.
444 _min_gen0_size = max_new_size;
445 _initial_gen0_size = max_new_size;
446 _max_gen0_size = max_new_size;
447 } else {
448 size_t desired_new_size = 0;
449 if (FLAG_IS_CMDLINE(NewSize)) {
450 // If NewSize is set on the command line, we must use it as
451 // the initial size and it also makes sense to use it as the
452 // lower limit.
453 _min_gen0_size = NewSize;
454 desired_new_size = NewSize;
455 max_new_size = MAX2(max_new_size, NewSize);
456 } else if (FLAG_IS_ERGO(NewSize)) {
457 // If NewSize is set ergonomically, we should use it as a lower
458 // limit, but use NewRatio to calculate the initial size.
459 _min_gen0_size = NewSize;
460 desired_new_size =
461 MAX2(scale_by_NewRatio_aligned(_initial_heap_byte_size), NewSize);
462 max_new_size = MAX2(max_new_size, NewSize);
463 } else {
464 // For the case where NewSize is the default, use NewRatio
465 // to size the minimum and initial generation sizes.
466 // Use the default NewSize as the floor for these values. If
467 // NewRatio is overly large, the resulting sizes can be too small.
468 _min_gen0_size = MAX2(scale_by_NewRatio_aligned(_min_heap_byte_size), NewSize);
469 desired_new_size =
470 MAX2(scale_by_NewRatio_aligned(_initial_heap_byte_size), NewSize);
471 }
472
473 assert(_min_gen0_size > 0, "Sanity check");
474 _initial_gen0_size = desired_new_size;
475 _max_gen0_size = max_new_size;
476
477 // At this point the desirable initial and minimum sizes have been
478 // determined without regard to the maximum sizes.
479
480 // Bound the sizes by the corresponding overall heap sizes.
481 _min_gen0_size = bound_minus_alignment(_min_gen0_size, _min_heap_byte_size);
482 _initial_gen0_size = bound_minus_alignment(_initial_gen0_size, _initial_heap_byte_size);
483 _max_gen0_size = bound_minus_alignment(_max_gen0_size, _max_heap_byte_size);
484
485 // At this point all three sizes have been checked against the
486 // maximum sizes but have not been checked for consistency among the three.
487
488 // Final check min <= initial <= max
489 _min_gen0_size = MIN2(_min_gen0_size, _max_gen0_size);
490 _initial_gen0_size = MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size);
491 _min_gen0_size = MIN2(_min_gen0_size, _initial_gen0_size);
492 }
493
494 // Write back to flags if necessary.
495 if (NewSize != _initial_gen0_size) {
496 FLAG_SET_ERGO(uintx, NewSize, _initial_gen0_size);
497 }
498
499 if (MaxNewSize != _max_gen0_size) {
500 FLAG_SET_ERGO(uintx, MaxNewSize, _max_gen0_size);
501 }
502
503 if (PrintGCDetails && Verbose) {
504 gclog_or_tty->print_cr("1: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
505 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
506 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
507 }
508
509 DEBUG_ONLY(GenCollectorPolicy::assert_size_info();)
510 }
511
512 // Call this method during the sizing of the gen1 to make
513 // adjustments to gen0 because of gen1 sizing policy. gen0 initially has
514 // the most freedom in sizing because it is done before the
515 // policy for gen1 is applied. Once gen1 policies have been applied,
516 // there may be conflicts in the shape of the heap and this method
517 // is used to make the needed adjustments. The application of the
518 // policies could be more sophisticated (iterative for example) but
519 // keeping it simple also seems a worthwhile goal.
520 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr,
521 size_t* gen1_size_ptr,
522 const size_t heap_size) {
523 bool result = false;
524
525 if ((*gen0_size_ptr + *gen1_size_ptr) > heap_size) {
526 uintx smallest_new_size = young_gen_size_lower_bound();
527 if ((heap_size < (*gen0_size_ptr + _min_gen1_size)) &&
528 (heap_size >= _min_gen1_size + smallest_new_size)) {
529 // Adjust gen0 down to accommodate _min_gen1_size
530 *gen0_size_ptr = align_size_down_bounded(heap_size - _min_gen1_size, _gen_alignment);
531 result = true;
532 } else {
533 *gen1_size_ptr = align_size_down_bounded(heap_size - *gen0_size_ptr, _gen_alignment);
534 }
535 }
536 return result;
537 }
538
539 // Minimum sizes of the generations may be different than
540 // the initial sizes. An inconsistency is permitted here
541 // in the total size that can be specified explicitly by
542 // command line specification of OldSize and NewSize and
543 // also a command line specification of -Xms. Issue a warning
544 // but allow the values to pass.
545
546 void TwoGenerationCollectorPolicy::initialize_size_info() {
547 GenCollectorPolicy::initialize_size_info();
548
549 // At this point the minimum, initial and maximum sizes
550 // of the overall heap and of gen0 have been determined.
551 // The maximum gen1 size can be determined from the maximum gen0
552 // and maximum heap size since no explicit flags exist
553 // for setting the gen1 maximum.
554 _max_gen1_size = MAX2(_max_heap_byte_size - _max_gen0_size, _gen_alignment);
555
556 // If no explicit command line flag has been set for the
557 // gen1 size, use what is left for gen1
558 if (!FLAG_IS_CMDLINE(OldSize)) {
559 // The user has not specified any value but the ergonomics
560 // may have chosen a value (which may or may not be consistent
561 // with the overall heap size). In either case make
562 // the minimum, maximum and initial sizes consistent
563 // with the gen0 sizes and the overall heap sizes.
564 _min_gen1_size = MAX2(_min_heap_byte_size - _min_gen0_size, _gen_alignment);
565 _initial_gen1_size = MAX2(_initial_heap_byte_size - _initial_gen0_size, _gen_alignment);
566 // _max_gen1_size has already been made consistent above
567 FLAG_SET_ERGO(uintx, OldSize, _initial_gen1_size);
568 } else {
569 // OldSize has been explicitly set on the command line. Use the
570 // OldSize and then determine the consequences.
571 _min_gen1_size = MIN2(OldSize, _min_heap_byte_size - _min_gen0_size);
572 _initial_gen1_size = OldSize;
573
574 // If the user has explicitly set an OldSize that is inconsistent
575 // with other command line flags, issue a warning.
576 // The generation minimums and the overall heap minimum should
577 // be within one generation alignment.
578 if ((_min_gen1_size + _min_gen0_size + _gen_alignment) < _min_heap_byte_size) {
579 warning("Inconsistency between minimum heap size and minimum "
580 "generation sizes: using minimum heap = " SIZE_FORMAT,
581 _min_heap_byte_size);
582 }
583 if (OldSize > _max_gen1_size) {
584 warning("Inconsistency between maximum heap size and maximum "
585 "generation sizes: using maximum heap = " SIZE_FORMAT
586 " -XX:OldSize flag is being ignored",
587 _max_heap_byte_size);
588 }
589 // If there is an inconsistency between the OldSize and the minimum and/or
590 // initial size of gen0, since OldSize was explicitly set, OldSize wins.
591 if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size, _min_heap_byte_size)) {
592 if (PrintGCDetails && Verbose) {
593 gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
594 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
595 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
596 }
597 }
598 // The same as above for the old gen initial size.
599 if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,
600 _initial_heap_byte_size)) {
601 if (PrintGCDetails && Verbose) {
602 gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
603 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
604 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
605 }
606 }
607 }
608
609 _min_gen1_size = MIN2(_min_gen1_size, _max_gen1_size);
610
611 // Make sure that min gen1 <= initial gen1 <= max gen1.
612 _initial_gen1_size = MAX2(_initial_gen1_size, _min_gen1_size);
613 _initial_gen1_size = MIN2(_initial_gen1_size, _max_gen1_size);
614
615 // Write back to flags if necessary
616 if (NewSize != _initial_gen0_size) {
617 FLAG_SET_ERGO(uintx, NewSize, _initial_gen0_size);
618 }
619
620 if (MaxNewSize != _max_gen0_size) {
621 FLAG_SET_ERGO(uintx, MaxNewSize, _max_gen0_size);
622 }
623
624 if (OldSize != _initial_gen1_size) {
625 FLAG_SET_ERGO(uintx, OldSize, _initial_gen1_size);
626 }
627
628 if (PrintGCDetails && Verbose) {
629 gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 "
630 SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT,
631 _min_gen1_size, _initial_gen1_size, _max_gen1_size);
632 }
633
634 DEBUG_ONLY(TwoGenerationCollectorPolicy::assert_size_info();)
635 }
636
637 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
638 bool is_tlab,
639 bool* gc_overhead_limit_was_exceeded) {
640 GenCollectedHeap *gch = GenCollectedHeap::heap();
641
642 debug_only(gch->check_for_valid_allocation_state());
643 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
644
645 // In general gc_overhead_limit_was_exceeded should be false so
646 // set it so here and reset it to true only if the gc time
647 // limit is being exceeded as checked below.
648 *gc_overhead_limit_was_exceeded = false;
649
650 HeapWord* result = NULL;
651
652 // Loop until the allocation is satisfied, 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 before checking success because the
917 // prologue could have succeeded and the GC still have been locked out.
918 if (op.gc_locked()) {
919 continue;
920 }
921
922 if (op.prologue_succeeded()) {
923 return op.result();
924 }
925 loop_count++;
926 if ((QueuedAllocationWarningCount > 0) &&
927 (loop_count % QueuedAllocationWarningCount == 0)) {
928 warning("satisfy_failed_metadata_allocation() retries %d times \n\t"
929 " size=%d", loop_count, word_size);
930 }
931 } while (true); // Until a GC is done
932 }
933
934 // Return true if any of the following is true:
935 // . the allocation won't fit into the current young gen heap
936 // . gc locker is occupied (jni critical section)
937 // . heap memory is tight -- the most recent previous collection
938 // was a full collection because a partial collection (would
939 // have) failed and is likely to fail again
940 bool GenCollectorPolicy::should_try_older_generation_allocation(
941 size_t word_size) const {
942 GenCollectedHeap* gch = GenCollectedHeap::heap();
943 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();
944 return (word_size > heap_word_size(gen0_capacity))
945 || GC_locker::is_active_and_needs_gc()
946 || gch->incremental_collection_failed();
947 }
948
949
950 //
951 // MarkSweepPolicy methods
952 //
953
954 void MarkSweepPolicy::initialize_alignments() {
955 _space_alignment = _gen_alignment = (uintx)Generation::GenGrain;
956 _heap_alignment = compute_heap_alignment();
957 }
958
959 void MarkSweepPolicy::initialize_generations() {
960 _generations = NEW_C_HEAP_ARRAY3(GenerationSpecPtr, number_of_generations(), mtGC, 0, AllocFailStrategy::RETURN_NULL);
961 if (_generations == NULL) {
962 vm_exit_during_initialization("Unable to allocate gen spec");
963 }
964
965 if (UseParNewGC) {
966 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);
967 } else {
968 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);
969 }
970 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);
971
972 if (_generations[0] == NULL || _generations[1] == NULL) {
973 vm_exit_during_initialization("Unable to allocate gen spec");
974 }
975 }
976
977 void MarkSweepPolicy::initialize_gc_policy_counters() {
978 // Initialize the policy counters - 2 collectors, 3 generations.
979 if (UseParNewGC) {
980 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);
981 } else {
982 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
983 }
984 }