1 /*
2 * Copyright (c) 2001, 2016, 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/shared/adaptiveSizePolicy.hpp"
27 #include "gc/shared/cardTableRS.hpp"
28 #include "gc/shared/collectorPolicy.hpp"
29 #include "gc/shared/gcLocker.inline.hpp"
30 #include "gc/shared/gcPolicyCounters.hpp"
31 #include "gc/shared/genCollectedHeap.hpp"
32 #include "gc/shared/generationSpec.hpp"
33 #include "gc/shared/space.hpp"
34 #include "gc/shared/vmGCOperations.hpp"
35 #include "logging/log.hpp"
36 #include "memory/universe.hpp"
37 #include "runtime/arguments.hpp"
38 #include "runtime/globals_extension.hpp"
39 #include "runtime/handles.inline.hpp"
40 #include "runtime/java.hpp"
41 #include "runtime/thread.inline.hpp"
42 #include "runtime/vmThread.hpp"
43 #include "utilities/macros.hpp"
44
45 // CollectorPolicy methods
46
47 CollectorPolicy::CollectorPolicy() :
48 _space_alignment(0),
49 _heap_alignment(0),
50 _initial_heap_byte_size(InitialHeapSize),
51 _max_heap_byte_size(MaxHeapSize),
52 _min_heap_byte_size(Arguments::min_heap_size()),
53 _size_policy(NULL),
54 _should_clear_all_soft_refs(false),
55 _all_soft_refs_clear(false)
56 {}
57
58 #ifdef ASSERT
59 void CollectorPolicy::assert_flags() {
60 assert(InitialHeapSize <= MaxHeapSize, "Ergonomics decided on incompatible initial and maximum heap sizes");
61 assert(InitialHeapSize % _heap_alignment == 0, "InitialHeapSize alignment");
62 assert(MaxHeapSize % _heap_alignment == 0, "MaxHeapSize alignment");
63 }
64
65 void CollectorPolicy::assert_size_info() {
66 assert(InitialHeapSize == _initial_heap_byte_size, "Discrepancy between InitialHeapSize flag and local storage");
67 assert(MaxHeapSize == _max_heap_byte_size, "Discrepancy between MaxHeapSize flag and local storage");
68 assert(_max_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible minimum and maximum heap sizes");
69 assert(_initial_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible initial and minimum heap sizes");
70 assert(_max_heap_byte_size >= _initial_heap_byte_size, "Ergonomics decided on incompatible initial and maximum heap sizes");
71 assert(_min_heap_byte_size % _heap_alignment == 0, "min_heap_byte_size alignment");
72 assert(_initial_heap_byte_size % _heap_alignment == 0, "initial_heap_byte_size alignment");
73 assert(_max_heap_byte_size % _heap_alignment == 0, "max_heap_byte_size alignment");
74 }
75 #endif // ASSERT
76
77 void CollectorPolicy::initialize_flags() {
78 assert(_space_alignment != 0, "Space alignment not set up properly");
79 assert(_heap_alignment != 0, "Heap alignment not set up properly");
80 assert(_heap_alignment >= _space_alignment,
81 "heap_alignment: " SIZE_FORMAT " less than space_alignment: " SIZE_FORMAT,
82 _heap_alignment, _space_alignment);
83 assert(_heap_alignment % _space_alignment == 0,
84 "heap_alignment: " SIZE_FORMAT " not aligned by space_alignment: " SIZE_FORMAT,
85 _heap_alignment, _space_alignment);
86
87 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
88 if (FLAG_IS_CMDLINE(InitialHeapSize) && InitialHeapSize > MaxHeapSize) {
89 vm_exit_during_initialization("Initial heap size set to a larger value than the maximum heap size");
90 }
91 if (_min_heap_byte_size != 0 && MaxHeapSize < _min_heap_byte_size) {
92 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified");
93 }
94 }
95
96 // Check heap parameter properties
97 if (MaxHeapSize < 2 * M) {
98 vm_exit_during_initialization("Too small maximum heap");
99 }
100 if (InitialHeapSize < M) {
101 vm_exit_during_initialization("Too small initial heap");
102 }
103 if (_min_heap_byte_size < M) {
104 vm_exit_during_initialization("Too small minimum heap");
105 }
106
107 // User inputs from -Xmx and -Xms must be aligned
108 _min_heap_byte_size = align_size_up(_min_heap_byte_size, _heap_alignment);
109 size_t aligned_initial_heap_size = align_size_up(InitialHeapSize, _heap_alignment);
110 size_t aligned_max_heap_size = align_size_up(MaxHeapSize, _heap_alignment);
111
112 // Write back to flags if the values changed
113 if (aligned_initial_heap_size != InitialHeapSize) {
114 FLAG_SET_ERGO(size_t, InitialHeapSize, aligned_initial_heap_size);
115 }
116 if (aligned_max_heap_size != MaxHeapSize) {
117 FLAG_SET_ERGO(size_t, MaxHeapSize, aligned_max_heap_size);
118 }
119
120 if (FLAG_IS_CMDLINE(InitialHeapSize) && _min_heap_byte_size != 0 &&
121 InitialHeapSize < _min_heap_byte_size) {
122 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified");
123 }
124 if (!FLAG_IS_DEFAULT(InitialHeapSize) && InitialHeapSize > MaxHeapSize) {
125 FLAG_SET_ERGO(size_t, MaxHeapSize, InitialHeapSize);
126 } else if (!FLAG_IS_DEFAULT(MaxHeapSize) && InitialHeapSize > MaxHeapSize) {
127 FLAG_SET_ERGO(size_t, InitialHeapSize, MaxHeapSize);
128 if (InitialHeapSize < _min_heap_byte_size) {
129 _min_heap_byte_size = InitialHeapSize;
130 }
131 }
132
133 _initial_heap_byte_size = InitialHeapSize;
134 _max_heap_byte_size = MaxHeapSize;
135
136 FLAG_SET_ERGO(size_t, MinHeapDeltaBytes, align_size_up(MinHeapDeltaBytes, _space_alignment));
137
138 DEBUG_ONLY(CollectorPolicy::assert_flags();)
139 }
140
141 void CollectorPolicy::initialize_size_info() {
142 log_debug(gc, heap)("Minimum heap " SIZE_FORMAT " Initial heap " SIZE_FORMAT " Maximum heap " SIZE_FORMAT,
143 _min_heap_byte_size, _initial_heap_byte_size, _max_heap_byte_size);
144
145 DEBUG_ONLY(CollectorPolicy::assert_size_info();)
146 }
147
148 bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) {
149 bool result = _should_clear_all_soft_refs;
150 set_should_clear_all_soft_refs(false);
151 return result;
152 }
153
154 void CollectorPolicy::cleared_all_soft_refs() {
155 // If near gc overhear limit, continue to clear SoftRefs. SoftRefs may
156 // have been cleared in the last collection but if the gc overhear
157 // limit continues to be near, SoftRefs should still be cleared.
158 if (size_policy() != NULL) {
159 _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near();
160 }
161 _all_soft_refs_clear = true;
162 }
163
164 size_t CollectorPolicy::compute_heap_alignment() {
165 // The card marking array and the offset arrays for old generations are
166 // committed in os pages as well. Make sure they are entirely full (to
167 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
168 // byte entry and the os page size is 4096, the maximum heap size should
169 // be 512*4096 = 2MB aligned.
170
171 size_t alignment = CardTableRS::ct_max_alignment_constraint();
172
173 if (UseLargePages) {
174 // In presence of large pages we have to make sure that our
175 // alignment is large page aware.
176 alignment = lcm(os::large_page_size(), alignment);
177 }
178
179 return alignment;
180 }
181
182 // GenCollectorPolicy methods
183
184 GenCollectorPolicy::GenCollectorPolicy() :
185 _min_young_size(0),
186 _initial_young_size(0),
187 _max_young_size(0),
188 _min_old_size(0),
189 _initial_old_size(0),
190 _max_old_size(0),
191 _gen_alignment(0),
192 _young_gen_spec(NULL),
193 _old_gen_spec(NULL)
194 {}
195
196 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {
197 return align_size_down_bounded(base_size / (NewRatio + 1), _gen_alignment);
198 }
199
200 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,
201 size_t maximum_size) {
202 size_t max_minus = maximum_size - _gen_alignment;
203 return desired_size < max_minus ? desired_size : max_minus;
204 }
205
206
207 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size,
208 size_t init_promo_size,
209 size_t init_survivor_size) {
210 const double max_gc_pause_sec = ((double) MaxGCPauseMillis) / 1000.0;
211 _size_policy = new AdaptiveSizePolicy(init_eden_size,
212 init_promo_size,
213 init_survivor_size,
214 max_gc_pause_sec,
215 GCTimeRatio);
216 }
217
218 size_t GenCollectorPolicy::young_gen_size_lower_bound() {
219 // The young generation must be aligned and have room for eden + two survivors
220 return align_size_up(3 * _space_alignment, _gen_alignment);
221 }
222
223 size_t GenCollectorPolicy::old_gen_size_lower_bound() {
224 return align_size_up(_space_alignment, _gen_alignment);
225 }
226
227 #ifdef ASSERT
228 void GenCollectorPolicy::assert_flags() {
229 CollectorPolicy::assert_flags();
230 assert(NewSize >= _min_young_size, "Ergonomics decided on a too small young gen size");
231 assert(NewSize <= MaxNewSize, "Ergonomics decided on incompatible initial and maximum young gen sizes");
232 assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize < MaxHeapSize, "Ergonomics decided on incompatible maximum young gen and heap sizes");
233 assert(NewSize % _gen_alignment == 0, "NewSize alignment");
234 assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize % _gen_alignment == 0, "MaxNewSize alignment");
235 assert(OldSize + NewSize <= MaxHeapSize, "Ergonomics decided on incompatible generation and heap sizes");
236 assert(OldSize % _gen_alignment == 0, "OldSize alignment");
237 }
238
239 void GenCollectorPolicy::assert_size_info() {
240 CollectorPolicy::assert_size_info();
241 // GenCollectorPolicy::initialize_size_info may update the MaxNewSize
242 assert(MaxNewSize < MaxHeapSize, "Ergonomics decided on incompatible maximum young and heap sizes");
243 assert(NewSize == _initial_young_size, "Discrepancy between NewSize flag and local storage");
244 assert(MaxNewSize == _max_young_size, "Discrepancy between MaxNewSize flag and local storage");
245 assert(OldSize == _initial_old_size, "Discrepancy between OldSize flag and local storage");
246 assert(_min_young_size <= _initial_young_size, "Ergonomics decided on incompatible minimum and initial young gen sizes");
247 assert(_initial_young_size <= _max_young_size, "Ergonomics decided on incompatible initial and maximum young gen sizes");
248 assert(_min_young_size % _gen_alignment == 0, "_min_young_size alignment");
249 assert(_initial_young_size % _gen_alignment == 0, "_initial_young_size alignment");
250 assert(_max_young_size % _gen_alignment == 0, "_max_young_size alignment");
251 assert(_min_young_size <= bound_minus_alignment(_min_young_size, _min_heap_byte_size),
252 "Ergonomics made minimum young generation larger than minimum heap");
253 assert(_initial_young_size <= bound_minus_alignment(_initial_young_size, _initial_heap_byte_size),
254 "Ergonomics made initial young generation larger than initial heap");
255 assert(_max_young_size <= bound_minus_alignment(_max_young_size, _max_heap_byte_size),
256 "Ergonomics made maximum young generation lager than maximum heap");
257 assert(_min_old_size <= _initial_old_size, "Ergonomics decided on incompatible minimum and initial old gen sizes");
258 assert(_initial_old_size <= _max_old_size, "Ergonomics decided on incompatible initial and maximum old gen sizes");
259 assert(_max_old_size % _gen_alignment == 0, "_max_old_size alignment");
260 assert(_initial_old_size % _gen_alignment == 0, "_initial_old_size alignment");
261 assert(_max_heap_byte_size <= (_max_young_size + _max_old_size), "Total maximum heap sizes must be sum of generation maximum sizes");
262 assert(_min_young_size + _min_old_size <= _min_heap_byte_size, "Minimum generation sizes exceed minimum heap size");
263 assert(_initial_young_size + _initial_old_size == _initial_heap_byte_size, "Initial generation sizes should match initial heap size");
264 assert(_max_young_size + _max_old_size == _max_heap_byte_size, "Maximum generation sizes should match maximum heap size");
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 "heap_alignment: " SIZE_FORMAT " less than gen_alignment: " SIZE_FORMAT,
274 _heap_alignment, _gen_alignment);
275 assert(_gen_alignment % _space_alignment == 0,
276 "gen_alignment: " SIZE_FORMAT " not aligned by space_alignment: " SIZE_FORMAT,
277 _gen_alignment, _space_alignment);
278 assert(_heap_alignment % _gen_alignment == 0,
279 "heap_alignment: " SIZE_FORMAT " not aligned by gen_alignment: " SIZE_FORMAT,
280 _heap_alignment, _gen_alignment);
281
282 // All generational heaps have a young gen; handle those flags here
283
284 // Make sure the heap is large enough for two generations
285 size_t smallest_new_size = young_gen_size_lower_bound();
286 size_t smallest_heap_size = align_size_up(smallest_new_size + old_gen_size_lower_bound(),
287 _heap_alignment);
288 if (MaxHeapSize < smallest_heap_size) {
289 FLAG_SET_ERGO(size_t, 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(size_t, InitialHeapSize, smallest_heap_size);
297 _initial_heap_byte_size = smallest_heap_size;
298 }
299 }
300
301 // Make sure NewSize allows an old generation to fit even if set on the command line
302 if (FLAG_IS_CMDLINE(NewSize) && NewSize >= _initial_heap_byte_size) {
303 log_warning(gc, ergo)("NewSize was set larger than initial heap size, will use initial heap size.");
304 FLAG_SET_ERGO(size_t, NewSize, bound_minus_alignment(NewSize, _initial_heap_byte_size));
305 }
306
307 // Now take the actual NewSize into account. We will silently increase NewSize
308 // if the user specified a smaller or unaligned value.
309 size_t bounded_new_size = bound_minus_alignment(NewSize, MaxHeapSize);
310 bounded_new_size = MAX2(smallest_new_size, (size_t)align_size_down(bounded_new_size, _gen_alignment));
311 if (bounded_new_size != NewSize) {
312 FLAG_SET_ERGO(size_t, NewSize, bounded_new_size);
313 }
314 _min_young_size = smallest_new_size;
315 _initial_young_size = NewSize;
316
317 if (!FLAG_IS_DEFAULT(MaxNewSize)) {
318 if (MaxNewSize >= MaxHeapSize) {
319 // Make sure there is room for an old generation
320 size_t smaller_max_new_size = MaxHeapSize - _gen_alignment;
321 if (FLAG_IS_CMDLINE(MaxNewSize)) {
322 log_warning(gc, ergo)("MaxNewSize (" SIZE_FORMAT "k) is equal to or greater than the entire "
323 "heap (" SIZE_FORMAT "k). A new max generation size of " SIZE_FORMAT "k will be used.",
324 MaxNewSize/K, MaxHeapSize/K, smaller_max_new_size/K);
325 }
326 FLAG_SET_ERGO(size_t, MaxNewSize, smaller_max_new_size);
327 if (NewSize > MaxNewSize) {
328 FLAG_SET_ERGO(size_t, NewSize, MaxNewSize);
329 _initial_young_size = NewSize;
330 }
331 } else if (MaxNewSize < _initial_young_size) {
332 FLAG_SET_ERGO(size_t, MaxNewSize, _initial_young_size);
333 } else if (!is_size_aligned(MaxNewSize, _gen_alignment)) {
334 FLAG_SET_ERGO(size_t, MaxNewSize, align_size_down(MaxNewSize, _gen_alignment));
335 }
336 _max_young_size = MaxNewSize;
337 }
338
339 if (NewSize > MaxNewSize) {
340 // At this point this should only happen if the user specifies a large NewSize and/or
341 // a small (but not too small) MaxNewSize.
342 if (FLAG_IS_CMDLINE(MaxNewSize)) {
343 log_warning(gc, ergo)("NewSize (" SIZE_FORMAT "k) is greater than the MaxNewSize (" SIZE_FORMAT "k). "
344 "A new max generation size of " SIZE_FORMAT "k will be used.",
345 NewSize/K, MaxNewSize/K, NewSize/K);
346 }
347 FLAG_SET_ERGO(size_t, MaxNewSize, NewSize);
348 _max_young_size = MaxNewSize;
349 }
350
351 if (SurvivorRatio < 1 || NewRatio < 1) {
352 vm_exit_during_initialization("Invalid young gen ratio specified");
353 }
354
355 if (OldSize < old_gen_size_lower_bound()) {
356 FLAG_SET_ERGO(size_t, OldSize, old_gen_size_lower_bound());
357 }
358 if (!is_size_aligned(OldSize, _gen_alignment)) {
359 FLAG_SET_ERGO(size_t, OldSize, align_size_down(OldSize, _gen_alignment));
360 }
361
362 if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(MaxHeapSize)) {
363 // NewRatio will be used later to set the young generation size so we use
364 // it to calculate how big the heap should be based on the requested OldSize
365 // and NewRatio.
366 assert(NewRatio > 0, "NewRatio should have been set up earlier");
367 size_t calculated_heapsize = (OldSize / NewRatio) * (NewRatio + 1);
368
369 calculated_heapsize = align_size_up(calculated_heapsize, _heap_alignment);
370 FLAG_SET_ERGO(size_t, MaxHeapSize, calculated_heapsize);
371 _max_heap_byte_size = MaxHeapSize;
372 FLAG_SET_ERGO(size_t, InitialHeapSize, calculated_heapsize);
373 _initial_heap_byte_size = InitialHeapSize;
374 }
375
376 // Adjust NewSize and OldSize or MaxHeapSize to match each other
377 if (NewSize + OldSize > MaxHeapSize) {
378 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
379 // Somebody has set a maximum heap size with the intention that we should not
380 // exceed it. Adjust New/OldSize as necessary.
381 size_t calculated_size = NewSize + OldSize;
382 double shrink_factor = (double) MaxHeapSize / calculated_size;
383 size_t smaller_new_size = align_size_down((size_t)(NewSize * shrink_factor), _gen_alignment);
384 FLAG_SET_ERGO(size_t, NewSize, MAX2(young_gen_size_lower_bound(), smaller_new_size));
385 _initial_young_size = NewSize;
386
387 // OldSize is already aligned because above we aligned MaxHeapSize to
388 // _heap_alignment, and we just made sure that NewSize is aligned to
389 // _gen_alignment. In initialize_flags() we verified that _heap_alignment
390 // is a multiple of _gen_alignment.
391 FLAG_SET_ERGO(size_t, OldSize, MaxHeapSize - NewSize);
392 } else {
393 FLAG_SET_ERGO(size_t, MaxHeapSize, align_size_up(NewSize + OldSize, _heap_alignment));
394 _max_heap_byte_size = MaxHeapSize;
395 }
396 }
397
398 // Update NewSize, if possible, to avoid sizing the young gen too small when only
399 // OldSize is set on the command line.
400 if (FLAG_IS_CMDLINE(OldSize) && !FLAG_IS_CMDLINE(NewSize)) {
401 if (OldSize < _initial_heap_byte_size) {
402 size_t new_size = _initial_heap_byte_size - OldSize;
403 // Need to compare against the flag value for max since _max_young_size
404 // might not have been set yet.
405 if (new_size >= _min_young_size && new_size <= MaxNewSize) {
406 FLAG_SET_ERGO(size_t, NewSize, new_size);
407 _initial_young_size = NewSize;
408 }
409 }
410 }
411
412 always_do_update_barrier = UseConcMarkSweepGC;
413
414 DEBUG_ONLY(GenCollectorPolicy::assert_flags();)
415 }
416
417 // Values set on the command line win over any ergonomically
418 // set command line parameters.
419 // Ergonomic choice of parameters are done before this
420 // method is called. Values for command line parameters such as NewSize
421 // and MaxNewSize feed those ergonomic choices into this method.
422 // This method makes the final generation sizings consistent with
423 // themselves and with overall heap sizings.
424 // In the absence of explicitly set command line flags, policies
425 // such as the use of NewRatio are used to size the generation.
426
427 // Minimum sizes of the generations may be different than
428 // the initial sizes. An inconsistency is permitted here
429 // in the total size that can be specified explicitly by
430 // command line specification of OldSize and NewSize and
431 // also a command line specification of -Xms. Issue a warning
432 // but allow the values to pass.
433 void GenCollectorPolicy::initialize_size_info() {
434 CollectorPolicy::initialize_size_info();
435
436 _initial_young_size = NewSize;
437 _max_young_size = MaxNewSize;
438 _initial_old_size = OldSize;
439
440 // Determine maximum size of the young generation.
441
442 if (FLAG_IS_DEFAULT(MaxNewSize)) {
443 _max_young_size = scale_by_NewRatio_aligned(_max_heap_byte_size);
444 // Bound the maximum size by NewSize below (since it historically
445 // would have been NewSize and because the NewRatio calculation could
446 // yield a size that is too small) and bound it by MaxNewSize above.
447 // Ergonomics plays here by previously calculating the desired
448 // NewSize and MaxNewSize.
449 _max_young_size = MIN2(MAX2(_max_young_size, _initial_young_size), MaxNewSize);
450 }
451
452 // Given the maximum young size, determine the initial and
453 // minimum young sizes.
454
455 if (_max_heap_byte_size == _initial_heap_byte_size) {
456 // The maximum and initial heap sizes are the same so the generation's
457 // initial size must be the same as it maximum size. Use NewSize as the
458 // size if set on command line.
459 _max_young_size = FLAG_IS_CMDLINE(NewSize) ? NewSize : _max_young_size;
460 _initial_young_size = _max_young_size;
461
462 // Also update the minimum size if min == initial == max.
463 if (_max_heap_byte_size == _min_heap_byte_size) {
464 _min_young_size = _max_young_size;
465 }
466 } else {
467 if (FLAG_IS_CMDLINE(NewSize)) {
468 // If NewSize is set on the command line, we should use it as
469 // the initial size, but make sure it is within the heap bounds.
470 _initial_young_size =
471 MIN2(_max_young_size, bound_minus_alignment(NewSize, _initial_heap_byte_size));
472 _min_young_size = bound_minus_alignment(_initial_young_size, _min_heap_byte_size);
473 } else {
474 // For the case where NewSize is not set on the command line, use
475 // NewRatio to size the initial generation size. Use the current
476 // NewSize as the floor, because if NewRatio is overly large, the resulting
477 // size can be too small.
478 _initial_young_size =
479 MIN2(_max_young_size, MAX2(scale_by_NewRatio_aligned(_initial_heap_byte_size), NewSize));
480 }
481 }
482
483 log_trace(gc, heap)("1: Minimum young " SIZE_FORMAT " Initial young " SIZE_FORMAT " Maximum young " SIZE_FORMAT,
484 _min_young_size, _initial_young_size, _max_young_size);
485
486 // At this point the minimum, initial and maximum sizes
487 // of the overall heap and of the young generation have been determined.
488 // The maximum old size can be determined from the maximum young
489 // and maximum heap size since no explicit flags exist
490 // for setting the old generation maximum.
491 _max_old_size = MAX2(_max_heap_byte_size - _max_young_size, _gen_alignment);
492
493 // If no explicit command line flag has been set for the
494 // old generation size, use what is left.
495 if (!FLAG_IS_CMDLINE(OldSize)) {
496 // The user has not specified any value but the ergonomics
497 // may have chosen a value (which may or may not be consistent
498 // with the overall heap size). In either case make
499 // the minimum, maximum and initial sizes consistent
500 // with the young sizes and the overall heap sizes.
501 _min_old_size = _gen_alignment;
502 _initial_old_size = MIN2(_max_old_size, MAX2(_initial_heap_byte_size - _initial_young_size, _min_old_size));
503 // _max_old_size has already been made consistent above.
504 } else {
505 // OldSize has been explicitly set on the command line. Use it
506 // for the initial size but make sure the minimum allow a young
507 // generation to fit as well.
508 // If the user has explicitly set an OldSize that is inconsistent
509 // with other command line flags, issue a warning.
510 // The generation minimums and the overall heap minimum should
511 // be within one generation alignment.
512 if (_initial_old_size > _max_old_size) {
513 log_warning(gc, ergo)("Inconsistency between maximum heap size and maximum "
514 "generation sizes: using maximum heap = " SIZE_FORMAT
515 ", -XX:OldSize flag is being ignored",
516 _max_heap_byte_size);
517 _initial_old_size = _max_old_size;
518 }
519
520 _min_old_size = MIN2(_initial_old_size, _min_heap_byte_size - _min_young_size);
521 }
522
523 // The initial generation sizes should match the initial heap size,
524 // if not issue a warning and resize the generations. This behavior
525 // differs from JDK8 where the generation sizes have higher priority
526 // than the initial heap size.
527 if ((_initial_old_size + _initial_young_size) != _initial_heap_byte_size) {
528 log_warning(gc, ergo)("Inconsistency between generation sizes and heap size, resizing "
529 "the generations to fit the heap.");
530
531 size_t desired_young_size = _initial_heap_byte_size - _initial_old_size;
532 if (_initial_heap_byte_size < _initial_old_size) {
533 // Old want all memory, use minimum for young and rest for old
534 _initial_young_size = _min_young_size;
535 _initial_old_size = _initial_heap_byte_size - _min_young_size;
536 } else if (desired_young_size > _max_young_size) {
537 // Need to increase both young and old generation
538 _initial_young_size = _max_young_size;
539 _initial_old_size = _initial_heap_byte_size - _max_young_size;
540 } else if (desired_young_size < _min_young_size) {
541 // Need to decrease both young and old generation
542 _initial_young_size = _min_young_size;
543 _initial_old_size = _initial_heap_byte_size - _min_young_size;
544 } else {
545 // The young generation boundaries allow us to only update the
546 // young generation.
547 _initial_young_size = desired_young_size;
548 }
549
550 log_trace(gc, heap)("2: Minimum young " SIZE_FORMAT " Initial young " SIZE_FORMAT " Maximum young " SIZE_FORMAT,
551 _min_young_size, _initial_young_size, _max_young_size);
552 }
553
554 // Write back to flags if necessary.
555 if (NewSize != _initial_young_size) {
556 FLAG_SET_ERGO(size_t, NewSize, _initial_young_size);
557 }
558
559 if (MaxNewSize != _max_young_size) {
560 FLAG_SET_ERGO(size_t, MaxNewSize, _max_young_size);
561 }
562
563 if (OldSize != _initial_old_size) {
564 FLAG_SET_ERGO(size_t, OldSize, _initial_old_size);
565 }
566
567 log_trace(gc, heap)("Minimum old " SIZE_FORMAT " Initial old " SIZE_FORMAT " Maximum old " SIZE_FORMAT,
568 _min_old_size, _initial_old_size, _max_old_size);
569
570 DEBUG_ONLY(GenCollectorPolicy::assert_size_info();)
571 }
572
573 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
574 bool is_tlab,
575 bool* gc_overhead_limit_was_exceeded) {
576 GenCollectedHeap *gch = GenCollectedHeap::heap();
577
578 debug_only(gch->check_for_valid_allocation_state());
579 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
580
581 // In general gc_overhead_limit_was_exceeded should be false so
582 // set it so here and reset it to true only if the gc time
583 // limit is being exceeded as checked below.
584 *gc_overhead_limit_was_exceeded = false;
585
586 HeapWord* result = NULL;
587
588 // Loop until the allocation is satisfied, or unsatisfied after GC.
589 for (uint try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) {
590 HandleMark hm; // Discard any handles allocated in each iteration.
591
592 // First allocation attempt is lock-free.
593 Generation *young = gch->young_gen();
594 assert(young->supports_inline_contig_alloc(),
595 "Otherwise, must do alloc within heap lock");
596 if (young->should_allocate(size, is_tlab)) {
597 result = young->par_allocate(size, is_tlab);
598 if (result != NULL) {
599 assert(gch->is_in_reserved(result), "result not in heap");
600 return result;
601 }
602 }
603 uint gc_count_before; // Read inside the Heap_lock locked region.
604 {
605 MutexLocker ml(Heap_lock);
606 log_trace(gc, alloc)("GenCollectorPolicy::mem_allocate_work: attempting locked slow path allocation");
607 // Note that only large objects get a shot at being
608 // allocated in later generations.
609 bool first_only = ! should_try_older_generation_allocation(size);
610
611 result = gch->attempt_allocation(size, is_tlab, first_only);
612 if (result != NULL) {
613 assert(gch->is_in_reserved(result), "result not in heap");
614 return result;
615 }
616
617 if (GCLocker::is_active_and_needs_gc()) {
618 if (is_tlab) {
619 return NULL; // Caller will retry allocating individual object.
620 }
621 if (!gch->is_maximal_no_gc()) {
622 // Try and expand heap to satisfy request.
623 result = expand_heap_and_allocate(size, is_tlab);
624 // Result could be null if we are out of space.
625 if (result != NULL) {
626 return result;
627 }
628 }
629
630 if (gclocker_stalled_count > GCLockerRetryAllocationCount) {
631 return NULL; // We didn't get to do a GC and we didn't get any memory.
632 }
633
634 // If this thread is not in a jni critical section, we stall
635 // the requestor until the critical section has cleared and
636 // GC allowed. When the critical section clears, a GC is
637 // initiated by the last thread exiting the critical section; so
638 // we retry the allocation sequence from the beginning of the loop,
639 // rather than causing more, now probably unnecessary, GC attempts.
640 JavaThread* jthr = JavaThread::current();
641 if (!jthr->in_critical()) {
642 MutexUnlocker mul(Heap_lock);
643 // Wait for JNI critical section to be exited
644 GCLocker::stall_until_clear();
645 gclocker_stalled_count += 1;
646 continue;
647 } else {
648 if (CheckJNICalls) {
649 fatal("Possible deadlock due to allocating while"
650 " in jni critical section");
651 }
652 return NULL;
653 }
654 }
655
656 // Read the gc count while the heap lock is held.
657 gc_count_before = gch->total_collections();
658 }
659
660 VM_GenCollectForAllocation op(size, is_tlab, gc_count_before);
661 VMThread::execute(&op);
662 if (op.prologue_succeeded()) {
663 result = op.result();
664 if (op.gc_locked()) {
665 assert(result == NULL, "must be NULL if gc_locked() is true");
666 continue; // Retry and/or stall as necessary.
667 }
668
669 // Allocation has failed and a collection
670 // has been done. If the gc time limit was exceeded the
671 // this time, return NULL so that an out-of-memory
672 // will be thrown. Clear gc_overhead_limit_exceeded
673 // so that the overhead exceeded does not persist.
674
675 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
676 const bool softrefs_clear = all_soft_refs_clear();
677
678 if (limit_exceeded && softrefs_clear) {
679 *gc_overhead_limit_was_exceeded = true;
680 size_policy()->set_gc_overhead_limit_exceeded(false);
681 if (op.result() != NULL) {
682 CollectedHeap::fill_with_object(op.result(), size);
683 }
684 return NULL;
685 }
686 assert(result == NULL || gch->is_in_reserved(result),
687 "result not in heap");
688 return result;
689 }
690
691 // Give a warning if we seem to be looping forever.
692 if ((QueuedAllocationWarningCount > 0) &&
693 (try_count % QueuedAllocationWarningCount == 0)) {
694 log_warning(gc, ergo)("GenCollectorPolicy::mem_allocate_work retries %d times,"
695 " size=" SIZE_FORMAT " %s", try_count, size, is_tlab ? "(TLAB)" : "");
696 }
697 }
698 }
699
700 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size,
701 bool is_tlab) {
702 GenCollectedHeap *gch = GenCollectedHeap::heap();
703 HeapWord* result = NULL;
704 Generation *old = gch->old_gen();
705 if (old->should_allocate(size, is_tlab)) {
706 result = old->expand_and_allocate(size, is_tlab);
707 }
708 if (result == NULL) {
709 Generation *young = gch->young_gen();
710 if (young->should_allocate(size, is_tlab)) {
711 result = young->expand_and_allocate(size, is_tlab);
712 }
713 }
714 assert(result == NULL || gch->is_in_reserved(result), "result not in heap");
715 return result;
716 }
717
718 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size,
719 bool is_tlab) {
720 GenCollectedHeap *gch = GenCollectedHeap::heap();
721 GCCauseSetter x(gch, GCCause::_allocation_failure);
722 HeapWord* result = NULL;
723
724 assert(size != 0, "Precondition violated");
725 if (GCLocker::is_active_and_needs_gc()) {
726 // GC locker is active; instead of a collection we will attempt
727 // to expand the heap, if there's room for expansion.
728 if (!gch->is_maximal_no_gc()) {
729 result = expand_heap_and_allocate(size, is_tlab);
730 }
731 return result; // Could be null if we are out of space.
732 } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) {
733 // Do an incremental collection.
734 gch->do_collection(false, // full
735 false, // clear_all_soft_refs
736 size, // size
737 is_tlab, // is_tlab
738 GenCollectedHeap::OldGen); // max_generation
739 } else {
740 log_trace(gc)(" :: Trying full because partial may fail :: ");
741 // Try a full collection; see delta for bug id 6266275
742 // for the original code and why this has been simplified
743 // with from-space allocation criteria modified and
744 // such allocation moved out of the safepoint path.
745 gch->do_collection(true, // full
746 false, // clear_all_soft_refs
747 size, // size
748 is_tlab, // is_tlab
749 GenCollectedHeap::OldGen); // max_generation
750 }
751
752 result = gch->attempt_allocation(size, is_tlab, false /*first_only*/);
753
754 if (result != NULL) {
755 assert(gch->is_in_reserved(result), "result not in heap");
756 return result;
757 }
758
759 // OK, collection failed, try expansion.
760 result = expand_heap_and_allocate(size, is_tlab);
761 if (result != NULL) {
762 return result;
763 }
764
765 // If we reach this point, we're really out of memory. Try every trick
766 // we can to reclaim memory. Force collection of soft references. Force
767 // a complete compaction of the heap. Any additional methods for finding
768 // free memory should be here, especially if they are expensive. If this
769 // attempt fails, an OOM exception will be thrown.
770 {
771 UIntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
772
773 gch->do_collection(true, // full
774 true, // clear_all_soft_refs
775 size, // size
776 is_tlab, // is_tlab
777 GenCollectedHeap::OldGen); // max_generation
778 }
779
780 result = gch->attempt_allocation(size, is_tlab, false /* first_only */);
781 if (result != NULL) {
782 assert(gch->is_in_reserved(result), "result not in heap");
783 return result;
784 }
785
786 assert(!should_clear_all_soft_refs(),
787 "Flag should have been handled and cleared prior to this point");
788
789 // What else? We might try synchronous finalization later. If the total
790 // space available is large enough for the allocation, then a more
791 // complete compaction phase than we've tried so far might be
792 // appropriate.
793 return NULL;
794 }
795
796 MetaWord* CollectorPolicy::satisfy_failed_metadata_allocation(
797 ClassLoaderData* loader_data,
798 size_t word_size,
799 Metaspace::MetadataType mdtype) {
800 uint loop_count = 0;
801 uint gc_count = 0;
802 uint full_gc_count = 0;
803
804 assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock");
805
806 do {
807 MetaWord* result = loader_data->metaspace_non_null()->allocate(word_size, mdtype);
808 if (result != NULL) {
809 return result;
810 }
811
812 if (GCLocker::is_active_and_needs_gc()) {
813 // If the GCLocker is active, just expand and allocate.
814 // If that does not succeed, wait if this thread is not
815 // in a critical section itself.
816 result =
817 loader_data->metaspace_non_null()->expand_and_allocate(word_size,
818 mdtype);
819 if (result != NULL) {
820 return result;
821 }
822 JavaThread* jthr = JavaThread::current();
823 if (!jthr->in_critical()) {
824 // Wait for JNI critical section to be exited
825 GCLocker::stall_until_clear();
826 // The GC invoked by the last thread leaving the critical
827 // section will be a young collection and a full collection
828 // is (currently) needed for unloading classes so continue
829 // to the next iteration to get a full GC.
830 continue;
831 } else {
832 if (CheckJNICalls) {
833 fatal("Possible deadlock due to allocating while"
834 " in jni critical section");
835 }
836 return NULL;
837 }
838 }
839
840 { // Need lock to get self consistent gc_count's
841 MutexLocker ml(Heap_lock);
842 gc_count = Universe::heap()->total_collections();
843 full_gc_count = Universe::heap()->total_full_collections();
844 }
845
846 // Generate a VM operation
847 VM_CollectForMetadataAllocation op(loader_data,
848 word_size,
849 mdtype,
850 gc_count,
851 full_gc_count,
852 GCCause::_metadata_GC_threshold);
853 VMThread::execute(&op);
854
855 // If GC was locked out, try again. Check before checking success because the
856 // prologue could have succeeded and the GC still have been locked out.
857 if (op.gc_locked()) {
858 continue;
859 }
860
861 if (op.prologue_succeeded()) {
862 return op.result();
863 }
864 loop_count++;
865 if ((QueuedAllocationWarningCount > 0) &&
866 (loop_count % QueuedAllocationWarningCount == 0)) {
867 log_warning(gc, ergo)("satisfy_failed_metadata_allocation() retries %d times,"
868 " size=" SIZE_FORMAT, loop_count, word_size);
869 }
870 } while (true); // Until a GC is done
871 }
872
873 // Return true if any of the following is true:
874 // . the allocation won't fit into the current young gen heap
875 // . gc locker is occupied (jni critical section)
876 // . heap memory is tight -- the most recent previous collection
877 // was a full collection because a partial collection (would
878 // have) failed and is likely to fail again
879 bool GenCollectorPolicy::should_try_older_generation_allocation(
880 size_t word_size) const {
881 GenCollectedHeap* gch = GenCollectedHeap::heap();
882 size_t young_capacity = gch->young_gen()->capacity_before_gc();
883 return (word_size > heap_word_size(young_capacity))
884 || GCLocker::is_active_and_needs_gc()
885 || gch->incremental_collection_failed();
886 }
887
888
889 //
890 // MarkSweepPolicy methods
891 //
892
893 void MarkSweepPolicy::initialize_alignments() {
894 _space_alignment = _gen_alignment = (size_t)Generation::GenGrain;
895 _heap_alignment = compute_heap_alignment();
896 }
897
898 void MarkSweepPolicy::initialize_generations() {
899 _young_gen_spec = new GenerationSpec(Generation::DefNew, _initial_young_size, _max_young_size, _gen_alignment);
900 _old_gen_spec = new GenerationSpec(Generation::MarkSweepCompact, _initial_old_size, _max_old_size, _gen_alignment);
901 }
902
903 void MarkSweepPolicy::initialize_gc_policy_counters() {
904 // Initialize the policy counters - 2 collectors, 3 generations.
905 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
906 }