Sat, 23 Nov 2013 12:25:13 +0100
8028128: Add a type safe alternative for working with counter based data
Reviewed-by: dholmes, egahlin
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.
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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
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23 */
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
48 // CollectorPolicy methods.
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 {}
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 }
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
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));
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 }
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 }
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);
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 }
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 }
135 _initial_heap_byte_size = InitialHeapSize;
136 _max_heap_byte_size = MaxHeapSize;
138 FLAG_SET_ERGO(uintx, MinHeapDeltaBytes, align_size_up(MinHeapDeltaBytes, _space_alignment));
140 DEBUG_ONLY(CollectorPolicy::assert_flags();)
141 }
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 }
150 DEBUG_ONLY(CollectorPolicy::assert_size_info();)
151 }
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 }
159 GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap,
160 int max_covered_regions) {
161 return new CardTableRS(whole_heap, max_covered_regions);
162 }
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 }
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.
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);
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 }
196 return alignment;
197 }
199 // GenCollectorPolicy methods.
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 {}
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 }
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 }
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 }
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 }
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 }
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 }
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 }
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
276 void GenCollectorPolicy::initialize_flags() {
277 CollectorPolicy::initialize_flags();
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));
290 // All generational heaps have a youngest gen; handle those flags here
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 }
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;
317 if (!FLAG_IS_DEFAULT(MaxNewSize)) {
318 uintx min_new_size = MAX2(_gen_alignment, _min_gen0_size);
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 }
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 }
353 if (SurvivorRatio < 1 || NewRatio < 1) {
354 vm_exit_during_initialization("Invalid young gen ratio specified");
355 }
357 DEBUG_ONLY(GenCollectorPolicy::assert_flags();)
358 }
360 void TwoGenerationCollectorPolicy::initialize_flags() {
361 GenCollectorPolicy::initialize_flags();
363 if (!is_size_aligned(OldSize, _gen_alignment)) {
364 FLAG_SET_ERGO(uintx, OldSize, align_size_down(OldSize, _gen_alignment));
365 }
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);
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 }
381 // adjust max heap size if necessary
382 if (NewSize + OldSize > MaxHeapSize) {
383 if (_max_heap_size_cmdline) {
384 // somebody 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;
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 }
403 always_do_update_barrier = UseConcMarkSweepGC;
405 DEBUG_ONLY(TwoGenerationCollectorPolicy::assert_flags();)
406 }
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();
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.
425 // Determine maximum size of gen0
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");
441 // Given the maximum gen0 size, determine the initial and
442 // minimum gen0 sizes.
444 if (_max_heap_byte_size == _min_heap_byte_size) {
445 // The maximum and minimum heap sizes are the same so
446 // the generations minimum and initial must be the
447 // same as its maximum.
448 _min_gen0_size = max_new_size;
449 _initial_gen0_size = max_new_size;
450 _max_gen0_size = max_new_size;
451 } else {
452 size_t desired_new_size = 0;
453 if (!FLAG_IS_DEFAULT(NewSize)) {
454 // If NewSize is set ergonomically (for example by cms), it
455 // would make sense to use it. If it is used, also use it
456 // to set the initial size. Although there is no reason
457 // the minimum size and the initial size have to be the same,
458 // the current implementation gets into trouble during the calculation
459 // of the tenured generation sizes if they are different.
460 // Note that this makes the initial size and the minimum size
461 // generally small compared to the NewRatio calculation.
462 _min_gen0_size = NewSize;
463 desired_new_size = NewSize;
464 max_new_size = MAX2(max_new_size, NewSize);
465 } else {
466 // For the case where NewSize is the default, use NewRatio
467 // to size the minimum and initial generation sizes.
468 // Use the default NewSize as the floor for these values. If
469 // NewRatio is overly large, the resulting sizes can be too
470 // small.
471 _min_gen0_size = MAX2(scale_by_NewRatio_aligned(_min_heap_byte_size), NewSize);
472 desired_new_size =
473 MAX2(scale_by_NewRatio_aligned(_initial_heap_byte_size), NewSize);
474 }
476 assert(_min_gen0_size > 0, "Sanity check");
477 _initial_gen0_size = desired_new_size;
478 _max_gen0_size = max_new_size;
480 // At this point the desirable initial and minimum sizes have been
481 // determined without regard to the maximum sizes.
483 // Bound the sizes by the corresponding overall heap sizes.
484 _min_gen0_size = bound_minus_alignment(_min_gen0_size, _min_heap_byte_size);
485 _initial_gen0_size = bound_minus_alignment(_initial_gen0_size, _initial_heap_byte_size);
486 _max_gen0_size = bound_minus_alignment(_max_gen0_size, _max_heap_byte_size);
488 // At this point all three sizes have been checked against the
489 // maximum sizes but have not been checked for consistency
490 // among the three.
492 // Final check min <= initial <= max
493 _min_gen0_size = MIN2(_min_gen0_size, _max_gen0_size);
494 _initial_gen0_size = MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size);
495 _min_gen0_size = MIN2(_min_gen0_size, _initial_gen0_size);
496 }
498 // Write back to flags if necessary
499 if (NewSize != _initial_gen0_size) {
500 FLAG_SET_ERGO(uintx, NewSize, _initial_gen0_size);
501 }
503 if (MaxNewSize != _max_gen0_size) {
504 FLAG_SET_ERGO(uintx, MaxNewSize, _max_gen0_size);
505 }
507 if (PrintGCDetails && Verbose) {
508 gclog_or_tty->print_cr("1: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
509 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
510 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
511 }
513 DEBUG_ONLY(GenCollectorPolicy::assert_size_info();)
514 }
516 // Call this method during the sizing of the gen1 to make
517 // adjustments to gen0 because of gen1 sizing policy. gen0 initially has
518 // the most freedom in sizing because it is done before the
519 // policy for gen1 is applied. Once gen1 policies have been applied,
520 // there may be conflicts in the shape of the heap and this method
521 // is used to make the needed adjustments. The application of the
522 // policies could be more sophisticated (iterative for example) but
523 // keeping it simple also seems a worthwhile goal.
524 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr,
525 size_t* gen1_size_ptr,
526 const size_t heap_size) {
527 bool result = false;
529 if ((*gen0_size_ptr + *gen1_size_ptr) > heap_size) {
530 uintx smallest_new_size = young_gen_size_lower_bound();
531 if ((heap_size < (*gen0_size_ptr + _min_gen1_size)) &&
532 (heap_size >= _min_gen1_size + smallest_new_size)) {
533 // Adjust gen0 down to accommodate _min_gen1_size
534 *gen0_size_ptr = align_size_down_bounded(heap_size - _min_gen1_size, _gen_alignment);
535 result = true;
536 } else {
537 *gen1_size_ptr = align_size_down_bounded(heap_size - *gen0_size_ptr, _gen_alignment);
538 }
539 }
540 return result;
541 }
543 // Minimum sizes of the generations may be different than
544 // the initial sizes. An inconsistently is permitted here
545 // in the total size that can be specified explicitly by
546 // command line specification of OldSize and NewSize and
547 // also a command line specification of -Xms. Issue a warning
548 // but allow the values to pass.
550 void TwoGenerationCollectorPolicy::initialize_size_info() {
551 GenCollectorPolicy::initialize_size_info();
553 // At this point the minimum, initial and maximum sizes
554 // of the overall heap and of gen0 have been determined.
555 // The maximum gen1 size can be determined from the maximum gen0
556 // and maximum heap size since no explicit flags exits
557 // for setting the gen1 maximum.
558 _max_gen1_size = MAX2(_max_heap_byte_size - _max_gen0_size, _gen_alignment);
560 // If no explicit command line flag has been set for the
561 // gen1 size, use what is left for gen1.
562 if (!FLAG_IS_CMDLINE(OldSize)) {
563 // The user has not specified any value but the ergonomics
564 // may have chosen a value (which may or may not be consistent
565 // with the overall heap size). In either case make
566 // the minimum, maximum and initial sizes consistent
567 // with the gen0 sizes and the overall heap sizes.
568 _min_gen1_size = MAX2(_min_heap_byte_size - _min_gen0_size, _gen_alignment);
569 _initial_gen1_size = MAX2(_initial_heap_byte_size - _initial_gen0_size, _gen_alignment);
570 // _max_gen1_size has already been made consistent above
571 FLAG_SET_ERGO(uintx, OldSize, _initial_gen1_size);
572 } else {
573 // It's been explicitly set on the command line. Use the
574 // OldSize and then determine the consequences.
575 _min_gen1_size = MIN2(OldSize, _min_heap_byte_size - _min_gen0_size);
576 _initial_gen1_size = OldSize;
578 // If the user has explicitly set an OldSize that is inconsistent
579 // with other command line flags, issue a warning.
580 // The generation minimums and the overall heap mimimum should
581 // be within one generation alignment.
582 if ((_min_gen1_size + _min_gen0_size + _gen_alignment) < _min_heap_byte_size) {
583 warning("Inconsistency between minimum heap size and minimum "
584 "generation sizes: using minimum heap = " SIZE_FORMAT,
585 _min_heap_byte_size);
586 }
587 if (OldSize > _max_gen1_size) {
588 warning("Inconsistency between maximum heap size and maximum "
589 "generation sizes: using maximum heap = " SIZE_FORMAT
590 " -XX:OldSize flag is being ignored",
591 _max_heap_byte_size);
592 }
593 // If there is an inconsistency between the OldSize and the minimum and/or
594 // initial size of gen0, since OldSize was explicitly set, OldSize wins.
595 if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size, _min_heap_byte_size)) {
596 if (PrintGCDetails && Verbose) {
597 gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
598 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
599 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
600 }
601 }
602 // Initial size
603 if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,
604 _initial_heap_byte_size)) {
605 if (PrintGCDetails && Verbose) {
606 gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
607 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
608 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
609 }
610 }
611 }
612 // Enforce the maximum gen1 size.
613 _min_gen1_size = MIN2(_min_gen1_size, _max_gen1_size);
615 // Check that min gen1 <= initial gen1 <= max gen1
616 _initial_gen1_size = MAX2(_initial_gen1_size, _min_gen1_size);
617 _initial_gen1_size = MIN2(_initial_gen1_size, _max_gen1_size);
619 // Write back to flags if necessary
620 if (NewSize != _initial_gen0_size) {
621 FLAG_SET_ERGO(uintx, NewSize, _initial_gen0_size);
622 }
624 if (MaxNewSize != _max_gen0_size) {
625 FLAG_SET_ERGO(uintx, MaxNewSize, _max_gen0_size);
626 }
628 if (OldSize != _initial_gen1_size) {
629 FLAG_SET_ERGO(uintx, OldSize, _initial_gen1_size);
630 }
632 if (PrintGCDetails && Verbose) {
633 gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 "
634 SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT,
635 _min_gen1_size, _initial_gen1_size, _max_gen1_size);
636 }
638 DEBUG_ONLY(TwoGenerationCollectorPolicy::assert_size_info();)
639 }
641 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
642 bool is_tlab,
643 bool* gc_overhead_limit_was_exceeded) {
644 GenCollectedHeap *gch = GenCollectedHeap::heap();
646 debug_only(gch->check_for_valid_allocation_state());
647 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
649 // In general gc_overhead_limit_was_exceeded should be false so
650 // set it so here and reset it to true only if the gc time
651 // limit is being exceeded as checked below.
652 *gc_overhead_limit_was_exceeded = false;
654 HeapWord* result = NULL;
656 // Loop until the allocation is satisified,
657 // or unsatisfied after GC.
658 for (int try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) {
659 HandleMark hm; // discard any handles allocated in each iteration
661 // First allocation attempt is lock-free.
662 Generation *gen0 = gch->get_gen(0);
663 assert(gen0->supports_inline_contig_alloc(),
664 "Otherwise, must do alloc within heap lock");
665 if (gen0->should_allocate(size, is_tlab)) {
666 result = gen0->par_allocate(size, is_tlab);
667 if (result != NULL) {
668 assert(gch->is_in_reserved(result), "result not in heap");
669 return result;
670 }
671 }
672 unsigned int gc_count_before; // read inside the Heap_lock locked region
673 {
674 MutexLocker ml(Heap_lock);
675 if (PrintGC && Verbose) {
676 gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:"
677 " attempting locked slow path allocation");
678 }
679 // Note that only large objects get a shot at being
680 // allocated in later generations.
681 bool first_only = ! should_try_older_generation_allocation(size);
683 result = gch->attempt_allocation(size, is_tlab, first_only);
684 if (result != NULL) {
685 assert(gch->is_in_reserved(result), "result not in heap");
686 return result;
687 }
689 if (GC_locker::is_active_and_needs_gc()) {
690 if (is_tlab) {
691 return NULL; // Caller will retry allocating individual object
692 }
693 if (!gch->is_maximal_no_gc()) {
694 // Try and expand heap to satisfy request
695 result = expand_heap_and_allocate(size, is_tlab);
696 // result could be null if we are out of space
697 if (result != NULL) {
698 return result;
699 }
700 }
702 if (gclocker_stalled_count > GCLockerRetryAllocationCount) {
703 return NULL; // we didn't get to do a GC and we didn't get any memory
704 }
706 // If this thread is not in a jni critical section, we stall
707 // the requestor until the critical section has cleared and
708 // GC allowed. When the critical section clears, a GC is
709 // initiated by the last thread exiting the critical section; so
710 // we retry the allocation sequence from the beginning of the loop,
711 // rather than causing more, now probably unnecessary, GC attempts.
712 JavaThread* jthr = JavaThread::current();
713 if (!jthr->in_critical()) {
714 MutexUnlocker mul(Heap_lock);
715 // Wait for JNI critical section to be exited
716 GC_locker::stall_until_clear();
717 gclocker_stalled_count += 1;
718 continue;
719 } else {
720 if (CheckJNICalls) {
721 fatal("Possible deadlock due to allocating while"
722 " in jni critical section");
723 }
724 return NULL;
725 }
726 }
728 // Read the gc count while the heap lock is held.
729 gc_count_before = Universe::heap()->total_collections();
730 }
732 VM_GenCollectForAllocation op(size, is_tlab, gc_count_before);
733 VMThread::execute(&op);
734 if (op.prologue_succeeded()) {
735 result = op.result();
736 if (op.gc_locked()) {
737 assert(result == NULL, "must be NULL if gc_locked() is true");
738 continue; // retry and/or stall as necessary
739 }
741 // Allocation has failed and a collection
742 // has been done. If the gc time limit was exceeded the
743 // this time, return NULL so that an out-of-memory
744 // will be thrown. Clear gc_overhead_limit_exceeded
745 // so that the overhead exceeded does not persist.
747 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
748 const bool softrefs_clear = all_soft_refs_clear();
750 if (limit_exceeded && softrefs_clear) {
751 *gc_overhead_limit_was_exceeded = true;
752 size_policy()->set_gc_overhead_limit_exceeded(false);
753 if (op.result() != NULL) {
754 CollectedHeap::fill_with_object(op.result(), size);
755 }
756 return NULL;
757 }
758 assert(result == NULL || gch->is_in_reserved(result),
759 "result not in heap");
760 return result;
761 }
763 // Give a warning if we seem to be looping forever.
764 if ((QueuedAllocationWarningCount > 0) &&
765 (try_count % QueuedAllocationWarningCount == 0)) {
766 warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t"
767 " size=%d %s", try_count, size, is_tlab ? "(TLAB)" : "");
768 }
769 }
770 }
772 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size,
773 bool is_tlab) {
774 GenCollectedHeap *gch = GenCollectedHeap::heap();
775 HeapWord* result = NULL;
776 for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) {
777 Generation *gen = gch->get_gen(i);
778 if (gen->should_allocate(size, is_tlab)) {
779 result = gen->expand_and_allocate(size, is_tlab);
780 }
781 }
782 assert(result == NULL || gch->is_in_reserved(result), "result not in heap");
783 return result;
784 }
786 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size,
787 bool is_tlab) {
788 GenCollectedHeap *gch = GenCollectedHeap::heap();
789 GCCauseSetter x(gch, GCCause::_allocation_failure);
790 HeapWord* result = NULL;
792 assert(size != 0, "Precondition violated");
793 if (GC_locker::is_active_and_needs_gc()) {
794 // GC locker is active; instead of a collection we will attempt
795 // to expand the heap, if there's room for expansion.
796 if (!gch->is_maximal_no_gc()) {
797 result = expand_heap_and_allocate(size, is_tlab);
798 }
799 return result; // could be null if we are out of space
800 } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) {
801 // Do an incremental collection.
802 gch->do_collection(false /* full */,
803 false /* clear_all_soft_refs */,
804 size /* size */,
805 is_tlab /* is_tlab */,
806 number_of_generations() - 1 /* max_level */);
807 } else {
808 if (Verbose && PrintGCDetails) {
809 gclog_or_tty->print(" :: Trying full because partial may fail :: ");
810 }
811 // Try a full collection; see delta for bug id 6266275
812 // for the original code and why this has been simplified
813 // with from-space allocation criteria modified and
814 // such allocation moved out of the safepoint path.
815 gch->do_collection(true /* full */,
816 false /* clear_all_soft_refs */,
817 size /* size */,
818 is_tlab /* is_tlab */,
819 number_of_generations() - 1 /* max_level */);
820 }
822 result = gch->attempt_allocation(size, is_tlab, false /*first_only*/);
824 if (result != NULL) {
825 assert(gch->is_in_reserved(result), "result not in heap");
826 return result;
827 }
829 // OK, collection failed, try expansion.
830 result = expand_heap_and_allocate(size, is_tlab);
831 if (result != NULL) {
832 return result;
833 }
835 // If we reach this point, we're really out of memory. Try every trick
836 // we can to reclaim memory. Force collection of soft references. Force
837 // a complete compaction of the heap. Any additional methods for finding
838 // free memory should be here, especially if they are expensive. If this
839 // attempt fails, an OOM exception will be thrown.
840 {
841 UIntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
843 gch->do_collection(true /* full */,
844 true /* clear_all_soft_refs */,
845 size /* size */,
846 is_tlab /* is_tlab */,
847 number_of_generations() - 1 /* max_level */);
848 }
850 result = gch->attempt_allocation(size, is_tlab, false /* first_only */);
851 if (result != NULL) {
852 assert(gch->is_in_reserved(result), "result not in heap");
853 return result;
854 }
856 assert(!should_clear_all_soft_refs(),
857 "Flag should have been handled and cleared prior to this point");
859 // What else? We might try synchronous finalization later. If the total
860 // space available is large enough for the allocation, then a more
861 // complete compaction phase than we've tried so far might be
862 // appropriate.
863 return NULL;
864 }
866 MetaWord* CollectorPolicy::satisfy_failed_metadata_allocation(
867 ClassLoaderData* loader_data,
868 size_t word_size,
869 Metaspace::MetadataType mdtype) {
870 uint loop_count = 0;
871 uint gc_count = 0;
872 uint full_gc_count = 0;
874 assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock");
876 do {
877 MetaWord* result = NULL;
878 if (GC_locker::is_active_and_needs_gc()) {
879 // If the GC_locker is active, just expand and allocate.
880 // If that does not succeed, wait if this thread is not
881 // in a critical section itself.
882 result =
883 loader_data->metaspace_non_null()->expand_and_allocate(word_size,
884 mdtype);
885 if (result != NULL) {
886 return result;
887 }
888 JavaThread* jthr = JavaThread::current();
889 if (!jthr->in_critical()) {
890 // Wait for JNI critical section to be exited
891 GC_locker::stall_until_clear();
892 // The GC invoked by the last thread leaving the critical
893 // section will be a young collection and a full collection
894 // is (currently) needed for unloading classes so continue
895 // to the next iteration to get a full GC.
896 continue;
897 } else {
898 if (CheckJNICalls) {
899 fatal("Possible deadlock due to allocating while"
900 " in jni critical section");
901 }
902 return NULL;
903 }
904 }
906 { // Need lock to get self consistent gc_count's
907 MutexLocker ml(Heap_lock);
908 gc_count = Universe::heap()->total_collections();
909 full_gc_count = Universe::heap()->total_full_collections();
910 }
912 // Generate a VM operation
913 VM_CollectForMetadataAllocation op(loader_data,
914 word_size,
915 mdtype,
916 gc_count,
917 full_gc_count,
918 GCCause::_metadata_GC_threshold);
919 VMThread::execute(&op);
921 // If GC was locked out, try again. Check
922 // before checking success because the prologue
923 // could have succeeded and the GC still have
924 // been locked out.
925 if (op.gc_locked()) {
926 continue;
927 }
929 if (op.prologue_succeeded()) {
930 return op.result();
931 }
932 loop_count++;
933 if ((QueuedAllocationWarningCount > 0) &&
934 (loop_count % QueuedAllocationWarningCount == 0)) {
935 warning("satisfy_failed_metadata_allocation() retries %d times \n\t"
936 " size=%d", loop_count, word_size);
937 }
938 } while (true); // Until a GC is done
939 }
941 // Return true if any of the following is true:
942 // . the allocation won't fit into the current young gen heap
943 // . gc locker is occupied (jni critical section)
944 // . heap memory is tight -- the most recent previous collection
945 // was a full collection because a partial collection (would
946 // have) failed and is likely to fail again
947 bool GenCollectorPolicy::should_try_older_generation_allocation(
948 size_t word_size) const {
949 GenCollectedHeap* gch = GenCollectedHeap::heap();
950 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();
951 return (word_size > heap_word_size(gen0_capacity))
952 || GC_locker::is_active_and_needs_gc()
953 || gch->incremental_collection_failed();
954 }
957 //
958 // MarkSweepPolicy methods
959 //
961 void MarkSweepPolicy::initialize_alignments() {
962 _space_alignment = _gen_alignment = (uintx)Generation::GenGrain;
963 _heap_alignment = compute_heap_alignment();
964 }
966 void MarkSweepPolicy::initialize_generations() {
967 _generations = NEW_C_HEAP_ARRAY3(GenerationSpecPtr, number_of_generations(), mtGC, 0, AllocFailStrategy::RETURN_NULL);
968 if (_generations == NULL) {
969 vm_exit_during_initialization("Unable to allocate gen spec");
970 }
972 if (UseParNewGC) {
973 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);
974 } else {
975 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);
976 }
977 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);
979 if (_generations[0] == NULL || _generations[1] == NULL) {
980 vm_exit_during_initialization("Unable to allocate gen spec");
981 }
982 }
984 void MarkSweepPolicy::initialize_gc_policy_counters() {
985 // initialize the policy counters - 2 collectors, 3 generations
986 if (UseParNewGC) {
987 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);
988 } else {
989 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
990 }
991 }