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/align.hpp"
44 #include "utilities/macros.hpp"
45
46 // CollectorPolicy methods
47
48 CollectorPolicy::CollectorPolicy() :
49 _space_alignment(0),
50 _heap_alignment(0),
51 _initial_heap_byte_size(InitialHeapSize),
52 _max_heap_byte_size(MaxHeapSize),
53 _min_heap_byte_size(Arguments::min_heap_size())
54 {}
55
56 #ifdef ASSERT
57 void CollectorPolicy::assert_flags() {
58 assert(InitialHeapSize <= MaxHeapSize, "Ergonomics decided on incompatible initial and maximum heap sizes");
59 assert(InitialHeapSize % _heap_alignment == 0, "InitialHeapSize alignment");
60 assert(MaxHeapSize % _heap_alignment == 0, "MaxHeapSize alignment");
61 }
62
63 void CollectorPolicy::assert_size_info() {
64 assert(InitialHeapSize == _initial_heap_byte_size, "Discrepancy between InitialHeapSize flag and local storage");
65 assert(MaxHeapSize == _max_heap_byte_size, "Discrepancy between MaxHeapSize flag and local storage");
66 assert(_max_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible minimum and maximum heap sizes");
67 assert(_initial_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible initial and minimum heap sizes");
68 assert(_max_heap_byte_size >= _initial_heap_byte_size, "Ergonomics decided on incompatible initial and maximum heap sizes");
69 assert(_min_heap_byte_size % _heap_alignment == 0, "min_heap_byte_size alignment");
70 assert(_initial_heap_byte_size % _heap_alignment == 0, "initial_heap_byte_size alignment");
71 assert(_max_heap_byte_size % _heap_alignment == 0, "max_heap_byte_size alignment");
72 }
73 #endif // ASSERT
74
75 void CollectorPolicy::initialize_flags() {
76 assert(_space_alignment != 0, "Space alignment not set up properly");
77 assert(_heap_alignment != 0, "Heap alignment not set up properly");
78 assert(_heap_alignment >= _space_alignment,
79 "heap_alignment: " SIZE_FORMAT " less than space_alignment: " SIZE_FORMAT,
80 _heap_alignment, _space_alignment);
81 assert(_heap_alignment % _space_alignment == 0,
82 "heap_alignment: " SIZE_FORMAT " not aligned by space_alignment: " SIZE_FORMAT,
83 _heap_alignment, _space_alignment);
84
85 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
86 if (FLAG_IS_CMDLINE(InitialHeapSize) && InitialHeapSize > MaxHeapSize) {
87 vm_exit_during_initialization("Initial heap size set to a larger value than the maximum heap size");
88 }
89 if (_min_heap_byte_size != 0 && MaxHeapSize < _min_heap_byte_size) {
90 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified");
91 }
92 }
93
94 // Check heap parameter properties
95 if (MaxHeapSize < 2 * M) {
96 vm_exit_during_initialization("Too small maximum heap");
97 }
98 if (InitialHeapSize < M) {
99 vm_exit_during_initialization("Too small initial heap");
100 }
101 if (_min_heap_byte_size < M) {
102 vm_exit_during_initialization("Too small minimum heap");
103 }
104
105 // User inputs from -Xmx and -Xms must be aligned
106 _min_heap_byte_size = align_up(_min_heap_byte_size, _heap_alignment);
107 size_t aligned_initial_heap_size = align_up(InitialHeapSize, _heap_alignment);
108 size_t aligned_max_heap_size = align_up(MaxHeapSize, _heap_alignment);
109
110 // Write back to flags if the values changed
111 if (aligned_initial_heap_size != InitialHeapSize) {
112 FLAG_SET_ERGO(size_t, InitialHeapSize, aligned_initial_heap_size);
113 }
114 if (aligned_max_heap_size != MaxHeapSize) {
115 FLAG_SET_ERGO(size_t, MaxHeapSize, aligned_max_heap_size);
116 }
117
118 if (FLAG_IS_CMDLINE(InitialHeapSize) && _min_heap_byte_size != 0 &&
119 InitialHeapSize < _min_heap_byte_size) {
120 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified");
121 }
122 if (!FLAG_IS_DEFAULT(InitialHeapSize) && InitialHeapSize > MaxHeapSize) {
123 FLAG_SET_ERGO(size_t, MaxHeapSize, InitialHeapSize);
124 } else if (!FLAG_IS_DEFAULT(MaxHeapSize) && InitialHeapSize > MaxHeapSize) {
125 FLAG_SET_ERGO(size_t, InitialHeapSize, MaxHeapSize);
126 if (InitialHeapSize < _min_heap_byte_size) {
127 _min_heap_byte_size = InitialHeapSize;
128 }
129 }
130
131 _initial_heap_byte_size = InitialHeapSize;
132 _max_heap_byte_size = MaxHeapSize;
133
134 FLAG_SET_ERGO(size_t, MinHeapDeltaBytes, align_up(MinHeapDeltaBytes, _space_alignment));
135
136 DEBUG_ONLY(CollectorPolicy::assert_flags();)
137 }
138
139 void CollectorPolicy::initialize_size_info() {
140 log_debug(gc, heap)("Minimum heap " SIZE_FORMAT " Initial heap " SIZE_FORMAT " Maximum heap " SIZE_FORMAT,
141 _min_heap_byte_size, _initial_heap_byte_size, _max_heap_byte_size);
142
143 DEBUG_ONLY(CollectorPolicy::assert_size_info();)
144 }
145
146 size_t CollectorPolicy::compute_heap_alignment() {
147 // The card marking array and the offset arrays for old generations are
148 // committed in os pages as well. Make sure they are entirely full (to
149 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
150 // byte entry and the os page size is 4096, the maximum heap size should
151 // be 512*4096 = 2MB aligned.
152
153 size_t alignment = CardTableRS::ct_max_alignment_constraint();
154
155 if (UseLargePages) {
156 // In presence of large pages we have to make sure that our
157 // alignment is large page aware.
158 alignment = lcm(os::large_page_size(), alignment);
159 }
160
161 return alignment;
162 }
163
164 // GenCollectorPolicy methods
165
166 GenCollectorPolicy::GenCollectorPolicy() :
167 _min_young_size(0),
168 _initial_young_size(0),
169 _max_young_size(0),
170 _min_old_size(0),
171 _initial_old_size(0),
172 _max_old_size(0),
173 _gen_alignment(0),
174 _young_gen_spec(NULL),
175 _old_gen_spec(NULL)
176 {}
177
178 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {
179 return align_down_bounded(base_size / (NewRatio + 1), _gen_alignment);
180 }
181
182 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,
183 size_t maximum_size) {
184 size_t max_minus = maximum_size - _gen_alignment;
185 return desired_size < max_minus ? desired_size : max_minus;
186 }
187
188 size_t GenCollectorPolicy::young_gen_size_lower_bound() {
189 // The young generation must be aligned and have room for eden + two survivors
190 return align_up(3 * _space_alignment, _gen_alignment);
191 }
192
193 size_t GenCollectorPolicy::old_gen_size_lower_bound() {
194 return align_up(_space_alignment, _gen_alignment);
195 }
196
197 #ifdef ASSERT
198 void GenCollectorPolicy::assert_flags() {
199 CollectorPolicy::assert_flags();
200 assert(NewSize >= _min_young_size, "Ergonomics decided on a too small young gen size");
201 assert(NewSize <= MaxNewSize, "Ergonomics decided on incompatible initial and maximum young gen sizes");
202 assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize < MaxHeapSize, "Ergonomics decided on incompatible maximum young gen and heap sizes");
203 assert(NewSize % _gen_alignment == 0, "NewSize alignment");
204 assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize % _gen_alignment == 0, "MaxNewSize alignment");
205 assert(OldSize + NewSize <= MaxHeapSize, "Ergonomics decided on incompatible generation and heap sizes");
206 assert(OldSize % _gen_alignment == 0, "OldSize alignment");
207 }
208
209 void GenCollectorPolicy::assert_size_info() {
210 CollectorPolicy::assert_size_info();
211 // GenCollectorPolicy::initialize_size_info may update the MaxNewSize
212 assert(MaxNewSize < MaxHeapSize, "Ergonomics decided on incompatible maximum young and heap sizes");
213 assert(NewSize == _initial_young_size, "Discrepancy between NewSize flag and local storage");
214 assert(MaxNewSize == _max_young_size, "Discrepancy between MaxNewSize flag and local storage");
215 assert(OldSize == _initial_old_size, "Discrepancy between OldSize flag and local storage");
216 assert(_min_young_size <= _initial_young_size, "Ergonomics decided on incompatible minimum and initial young gen sizes");
217 assert(_initial_young_size <= _max_young_size, "Ergonomics decided on incompatible initial and maximum young gen sizes");
218 assert(_min_young_size % _gen_alignment == 0, "_min_young_size alignment");
219 assert(_initial_young_size % _gen_alignment == 0, "_initial_young_size alignment");
220 assert(_max_young_size % _gen_alignment == 0, "_max_young_size alignment");
221 assert(_min_young_size <= bound_minus_alignment(_min_young_size, _min_heap_byte_size),
222 "Ergonomics made minimum young generation larger than minimum heap");
223 assert(_initial_young_size <= bound_minus_alignment(_initial_young_size, _initial_heap_byte_size),
224 "Ergonomics made initial young generation larger than initial heap");
225 assert(_max_young_size <= bound_minus_alignment(_max_young_size, _max_heap_byte_size),
226 "Ergonomics made maximum young generation lager than maximum heap");
227 assert(_min_old_size <= _initial_old_size, "Ergonomics decided on incompatible minimum and initial old gen sizes");
228 assert(_initial_old_size <= _max_old_size, "Ergonomics decided on incompatible initial and maximum old gen sizes");
229 assert(_max_old_size % _gen_alignment == 0, "_max_old_size alignment");
230 assert(_initial_old_size % _gen_alignment == 0, "_initial_old_size alignment");
231 assert(_max_heap_byte_size <= (_max_young_size + _max_old_size), "Total maximum heap sizes must be sum of generation maximum sizes");
232 assert(_min_young_size + _min_old_size <= _min_heap_byte_size, "Minimum generation sizes exceed minimum heap size");
233 assert(_initial_young_size + _initial_old_size == _initial_heap_byte_size, "Initial generation sizes should match initial heap size");
234 assert(_max_young_size + _max_old_size == _max_heap_byte_size, "Maximum generation sizes should match maximum heap size");
235 }
236 #endif // ASSERT
237
238 void GenCollectorPolicy::initialize_flags() {
239 CollectorPolicy::initialize_flags();
240
241 assert(_gen_alignment != 0, "Generation alignment not set up properly");
242 assert(_heap_alignment >= _gen_alignment,
243 "heap_alignment: " SIZE_FORMAT " less than gen_alignment: " SIZE_FORMAT,
244 _heap_alignment, _gen_alignment);
245 assert(_gen_alignment % _space_alignment == 0,
246 "gen_alignment: " SIZE_FORMAT " not aligned by space_alignment: " SIZE_FORMAT,
247 _gen_alignment, _space_alignment);
248 assert(_heap_alignment % _gen_alignment == 0,
249 "heap_alignment: " SIZE_FORMAT " not aligned by gen_alignment: " SIZE_FORMAT,
250 _heap_alignment, _gen_alignment);
251
252 // All generational heaps have a young gen; handle those flags here
253
254 // Make sure the heap is large enough for two generations
255 size_t smallest_new_size = young_gen_size_lower_bound();
256 size_t smallest_heap_size = align_up(smallest_new_size + old_gen_size_lower_bound(),
257 _heap_alignment);
258 if (MaxHeapSize < smallest_heap_size) {
259 FLAG_SET_ERGO(size_t, MaxHeapSize, smallest_heap_size);
260 _max_heap_byte_size = MaxHeapSize;
261 }
262 // If needed, synchronize _min_heap_byte size and _initial_heap_byte_size
263 if (_min_heap_byte_size < smallest_heap_size) {
264 _min_heap_byte_size = smallest_heap_size;
265 if (InitialHeapSize < _min_heap_byte_size) {
266 FLAG_SET_ERGO(size_t, InitialHeapSize, smallest_heap_size);
267 _initial_heap_byte_size = smallest_heap_size;
268 }
269 }
270
271 // Make sure NewSize allows an old generation to fit even if set on the command line
272 if (FLAG_IS_CMDLINE(NewSize) && NewSize >= _initial_heap_byte_size) {
273 log_warning(gc, ergo)("NewSize was set larger than initial heap size, will use initial heap size.");
274 FLAG_SET_ERGO(size_t, NewSize, bound_minus_alignment(NewSize, _initial_heap_byte_size));
275 }
276
277 // Now take the actual NewSize into account. We will silently increase NewSize
278 // if the user specified a smaller or unaligned value.
279 size_t bounded_new_size = bound_minus_alignment(NewSize, MaxHeapSize);
280 bounded_new_size = MAX2(smallest_new_size, align_down(bounded_new_size, _gen_alignment));
281 if (bounded_new_size != NewSize) {
282 FLAG_SET_ERGO(size_t, NewSize, bounded_new_size);
283 }
284 _min_young_size = smallest_new_size;
285 _initial_young_size = NewSize;
286
287 if (!FLAG_IS_DEFAULT(MaxNewSize)) {
288 if (MaxNewSize >= MaxHeapSize) {
289 // Make sure there is room for an old generation
290 size_t smaller_max_new_size = MaxHeapSize - _gen_alignment;
291 if (FLAG_IS_CMDLINE(MaxNewSize)) {
292 log_warning(gc, ergo)("MaxNewSize (" SIZE_FORMAT "k) is equal to or greater than the entire "
293 "heap (" SIZE_FORMAT "k). A new max generation size of " SIZE_FORMAT "k will be used.",
294 MaxNewSize/K, MaxHeapSize/K, smaller_max_new_size/K);
295 }
296 FLAG_SET_ERGO(size_t, MaxNewSize, smaller_max_new_size);
297 if (NewSize > MaxNewSize) {
298 FLAG_SET_ERGO(size_t, NewSize, MaxNewSize);
299 _initial_young_size = NewSize;
300 }
301 } else if (MaxNewSize < _initial_young_size) {
302 FLAG_SET_ERGO(size_t, MaxNewSize, _initial_young_size);
303 } else if (!is_aligned(MaxNewSize, _gen_alignment)) {
304 FLAG_SET_ERGO(size_t, MaxNewSize, align_down(MaxNewSize, _gen_alignment));
305 }
306 _max_young_size = MaxNewSize;
307 }
308
309 if (NewSize > MaxNewSize) {
310 // At this point this should only happen if the user specifies a large NewSize and/or
311 // a small (but not too small) MaxNewSize.
312 if (FLAG_IS_CMDLINE(MaxNewSize)) {
313 log_warning(gc, ergo)("NewSize (" SIZE_FORMAT "k) is greater than the MaxNewSize (" SIZE_FORMAT "k). "
314 "A new max generation size of " SIZE_FORMAT "k will be used.",
315 NewSize/K, MaxNewSize/K, NewSize/K);
316 }
317 FLAG_SET_ERGO(size_t, MaxNewSize, NewSize);
318 _max_young_size = MaxNewSize;
319 }
320
321 if (SurvivorRatio < 1 || NewRatio < 1) {
322 vm_exit_during_initialization("Invalid young gen ratio specified");
323 }
324
325 if (OldSize < old_gen_size_lower_bound()) {
326 FLAG_SET_ERGO(size_t, OldSize, old_gen_size_lower_bound());
327 }
328 if (!is_aligned(OldSize, _gen_alignment)) {
329 FLAG_SET_ERGO(size_t, OldSize, align_down(OldSize, _gen_alignment));
330 }
331
332 if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(MaxHeapSize)) {
333 // NewRatio will be used later to set the young generation size so we use
334 // it to calculate how big the heap should be based on the requested OldSize
335 // and NewRatio.
336 assert(NewRatio > 0, "NewRatio should have been set up earlier");
337 size_t calculated_heapsize = (OldSize / NewRatio) * (NewRatio + 1);
338
339 calculated_heapsize = align_up(calculated_heapsize, _heap_alignment);
340 FLAG_SET_ERGO(size_t, MaxHeapSize, calculated_heapsize);
341 _max_heap_byte_size = MaxHeapSize;
342 FLAG_SET_ERGO(size_t, InitialHeapSize, calculated_heapsize);
343 _initial_heap_byte_size = InitialHeapSize;
344 }
345
346 // Adjust NewSize and OldSize or MaxHeapSize to match each other
347 if (NewSize + OldSize > MaxHeapSize) {
348 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
349 // Somebody has set a maximum heap size with the intention that we should not
350 // exceed it. Adjust New/OldSize as necessary.
351 size_t calculated_size = NewSize + OldSize;
352 double shrink_factor = (double) MaxHeapSize / calculated_size;
353 size_t smaller_new_size = align_down((size_t)(NewSize * shrink_factor), _gen_alignment);
354 FLAG_SET_ERGO(size_t, NewSize, MAX2(young_gen_size_lower_bound(), smaller_new_size));
355 _initial_young_size = NewSize;
356
357 // OldSize is already aligned because above we aligned MaxHeapSize to
358 // _heap_alignment, and we just made sure that NewSize is aligned to
359 // _gen_alignment. In initialize_flags() we verified that _heap_alignment
360 // is a multiple of _gen_alignment.
361 FLAG_SET_ERGO(size_t, OldSize, MaxHeapSize - NewSize);
362 } else {
363 FLAG_SET_ERGO(size_t, MaxHeapSize, align_up(NewSize + OldSize, _heap_alignment));
364 _max_heap_byte_size = MaxHeapSize;
365 }
366 }
367
368 // Update NewSize, if possible, to avoid sizing the young gen too small when only
369 // OldSize is set on the command line.
370 if (FLAG_IS_CMDLINE(OldSize) && !FLAG_IS_CMDLINE(NewSize)) {
371 if (OldSize < _initial_heap_byte_size) {
372 size_t new_size = _initial_heap_byte_size - OldSize;
373 // Need to compare against the flag value for max since _max_young_size
374 // might not have been set yet.
375 if (new_size >= _min_young_size && new_size <= MaxNewSize) {
376 FLAG_SET_ERGO(size_t, NewSize, new_size);
377 _initial_young_size = NewSize;
378 }
379 }
380 }
381
382 always_do_update_barrier = UseConcMarkSweepGC;
383
384 DEBUG_ONLY(GenCollectorPolicy::assert_flags();)
385 }
386
387 // Values set on the command line win over any ergonomically
388 // set command line parameters.
389 // Ergonomic choice of parameters are done before this
390 // method is called. Values for command line parameters such as NewSize
391 // and MaxNewSize feed those ergonomic choices into this method.
392 // This method makes the final generation sizings consistent with
393 // themselves and with overall heap sizings.
394 // In the absence of explicitly set command line flags, policies
395 // such as the use of NewRatio are used to size the generation.
396
397 // Minimum sizes of the generations may be different than
398 // the initial sizes. An inconsistency is permitted here
399 // in the total size that can be specified explicitly by
400 // command line specification of OldSize and NewSize and
401 // also a command line specification of -Xms. Issue a warning
402 // but allow the values to pass.
403 void GenCollectorPolicy::initialize_size_info() {
404 CollectorPolicy::initialize_size_info();
405
406 _initial_young_size = NewSize;
407 _max_young_size = MaxNewSize;
408 _initial_old_size = OldSize;
409
410 // Determine maximum size of the young generation.
411
412 if (FLAG_IS_DEFAULT(MaxNewSize)) {
413 _max_young_size = scale_by_NewRatio_aligned(_max_heap_byte_size);
414 // Bound the maximum size by NewSize below (since it historically
415 // would have been NewSize and because the NewRatio calculation could
416 // yield a size that is too small) and bound it by MaxNewSize above.
417 // Ergonomics plays here by previously calculating the desired
418 // NewSize and MaxNewSize.
419 _max_young_size = MIN2(MAX2(_max_young_size, _initial_young_size), MaxNewSize);
420 }
421
422 // Given the maximum young size, determine the initial and
423 // minimum young sizes.
424
425 if (_max_heap_byte_size == _initial_heap_byte_size) {
426 // The maximum and initial heap sizes are the same so the generation's
427 // initial size must be the same as it maximum size. Use NewSize as the
428 // size if set on command line.
429 _max_young_size = FLAG_IS_CMDLINE(NewSize) ? NewSize : _max_young_size;
430 _initial_young_size = _max_young_size;
431
432 // Also update the minimum size if min == initial == max.
433 if (_max_heap_byte_size == _min_heap_byte_size) {
434 _min_young_size = _max_young_size;
435 }
436 } else {
437 if (FLAG_IS_CMDLINE(NewSize)) {
438 // If NewSize is set on the command line, we should use it as
439 // the initial size, but make sure it is within the heap bounds.
440 _initial_young_size =
441 MIN2(_max_young_size, bound_minus_alignment(NewSize, _initial_heap_byte_size));
442 _min_young_size = bound_minus_alignment(_initial_young_size, _min_heap_byte_size);
443 } else {
444 // For the case where NewSize is not set on the command line, use
445 // NewRatio to size the initial generation size. Use the current
446 // NewSize as the floor, because if NewRatio is overly large, the resulting
447 // size can be too small.
448 _initial_young_size =
449 MIN2(_max_young_size, MAX2(scale_by_NewRatio_aligned(_initial_heap_byte_size), NewSize));
450 }
451 }
452
453 log_trace(gc, heap)("1: Minimum young " SIZE_FORMAT " Initial young " SIZE_FORMAT " Maximum young " SIZE_FORMAT,
454 _min_young_size, _initial_young_size, _max_young_size);
455
456 // At this point the minimum, initial and maximum sizes
457 // of the overall heap and of the young generation have been determined.
458 // The maximum old size can be determined from the maximum young
459 // and maximum heap size since no explicit flags exist
460 // for setting the old generation maximum.
461 _max_old_size = MAX2(_max_heap_byte_size - _max_young_size, _gen_alignment);
462
463 // If no explicit command line flag has been set for the
464 // old generation size, use what is left.
465 if (!FLAG_IS_CMDLINE(OldSize)) {
466 // The user has not specified any value but the ergonomics
467 // may have chosen a value (which may or may not be consistent
468 // with the overall heap size). In either case make
469 // the minimum, maximum and initial sizes consistent
470 // with the young sizes and the overall heap sizes.
471 _min_old_size = _gen_alignment;
472 _initial_old_size = MIN2(_max_old_size, MAX2(_initial_heap_byte_size - _initial_young_size, _min_old_size));
473 // _max_old_size has already been made consistent above.
474 } else {
475 // OldSize has been explicitly set on the command line. Use it
476 // for the initial size but make sure the minimum allow a young
477 // generation to fit as well.
478 // If the user has explicitly set an OldSize that is inconsistent
479 // with other command line flags, issue a warning.
480 // The generation minimums and the overall heap minimum should
481 // be within one generation alignment.
482 if (_initial_old_size > _max_old_size) {
483 log_warning(gc, ergo)("Inconsistency between maximum heap size and maximum "
484 "generation sizes: using maximum heap = " SIZE_FORMAT
485 ", -XX:OldSize flag is being ignored",
486 _max_heap_byte_size);
487 _initial_old_size = _max_old_size;
488 }
489
490 _min_old_size = MIN2(_initial_old_size, _min_heap_byte_size - _min_young_size);
491 }
492
493 // The initial generation sizes should match the initial heap size,
494 // if not issue a warning and resize the generations. This behavior
495 // differs from JDK8 where the generation sizes have higher priority
496 // than the initial heap size.
497 if ((_initial_old_size + _initial_young_size) != _initial_heap_byte_size) {
498 log_warning(gc, ergo)("Inconsistency between generation sizes and heap size, resizing "
499 "the generations to fit the heap.");
500
501 size_t desired_young_size = _initial_heap_byte_size - _initial_old_size;
502 if (_initial_heap_byte_size < _initial_old_size) {
503 // Old want all memory, use minimum for young and rest for old
504 _initial_young_size = _min_young_size;
505 _initial_old_size = _initial_heap_byte_size - _min_young_size;
506 } else if (desired_young_size > _max_young_size) {
507 // Need to increase both young and old generation
508 _initial_young_size = _max_young_size;
509 _initial_old_size = _initial_heap_byte_size - _max_young_size;
510 } else if (desired_young_size < _min_young_size) {
511 // Need to decrease both young and old generation
512 _initial_young_size = _min_young_size;
513 _initial_old_size = _initial_heap_byte_size - _min_young_size;
514 } else {
515 // The young generation boundaries allow us to only update the
516 // young generation.
517 _initial_young_size = desired_young_size;
518 }
519
520 log_trace(gc, heap)("2: Minimum young " SIZE_FORMAT " Initial young " SIZE_FORMAT " Maximum young " SIZE_FORMAT,
521 _min_young_size, _initial_young_size, _max_young_size);
522 }
523
524 // Write back to flags if necessary.
525 if (NewSize != _initial_young_size) {
526 FLAG_SET_ERGO(size_t, NewSize, _initial_young_size);
527 }
528
529 if (MaxNewSize != _max_young_size) {
530 FLAG_SET_ERGO(size_t, MaxNewSize, _max_young_size);
531 }
532
533 if (OldSize != _initial_old_size) {
534 FLAG_SET_ERGO(size_t, OldSize, _initial_old_size);
535 }
536
537 log_trace(gc, heap)("Minimum old " SIZE_FORMAT " Initial old " SIZE_FORMAT " Maximum old " SIZE_FORMAT,
538 _min_old_size, _initial_old_size, _max_old_size);
539
540 DEBUG_ONLY(GenCollectorPolicy::assert_size_info();)
541 }
542
543 //
544 // MarkSweepPolicy methods
545 //
546
547 void MarkSweepPolicy::initialize_alignments() {
548 _space_alignment = _gen_alignment = (size_t)Generation::GenGrain;
549 _heap_alignment = compute_heap_alignment();
550 }
551
552 void MarkSweepPolicy::initialize_generations() {
553 _young_gen_spec = new GenerationSpec(Generation::DefNew, _initial_young_size, _max_young_size, _gen_alignment);
554 _old_gen_spec = new GenerationSpec(Generation::MarkSweepCompact, _initial_old_size, _max_old_size, _gen_alignment);
555 }
556
557 void MarkSweepPolicy::initialize_gc_policy_counters() {
558 // Initialize the policy counters - 2 collectors, 2 generations.
559 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 2);
560 }