36 #include "runtime/arguments.hpp"
37 #include "runtime/globals_extension.hpp"
38 #include "runtime/handles.inline.hpp"
39 #include "runtime/java.hpp"
40 #include "runtime/thread.inline.hpp"
41 #include "runtime/vmThread.hpp"
42 #include "utilities/macros.hpp"
43 #if INCLUDE_ALL_GCS
44 #include "gc_implementation/concurrentMarkSweep/cmsAdaptiveSizePolicy.hpp"
45 #include "gc_implementation/concurrentMarkSweep/cmsGCAdaptivePolicyCounters.hpp"
46 #endif // INCLUDE_ALL_GCS
47
48 // CollectorPolicy methods.
49
50 // Align down. If the aligning result in 0, return 'alignment'.
51 static size_t restricted_align_down(size_t size, size_t alignment) {
52 return MAX2(alignment, align_size_down_(size, alignment));
53 }
54
55 void CollectorPolicy::initialize_flags() {
56 assert(max_alignment() >= min_alignment(),
57 err_msg("max_alignment: " SIZE_FORMAT " less than min_alignment: " SIZE_FORMAT,
58 max_alignment(), min_alignment()));
59 assert(max_alignment() % min_alignment() == 0,
60 err_msg("max_alignment: " SIZE_FORMAT " not aligned by min_alignment: " SIZE_FORMAT,
61 max_alignment(), min_alignment()));
62
63 if (MaxHeapSize < InitialHeapSize) {
64 vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
65 }
66
67 if (!is_size_aligned(MaxMetaspaceSize, max_alignment())) {
68 FLAG_SET_ERGO(uintx, MaxMetaspaceSize,
69 restricted_align_down(MaxMetaspaceSize, max_alignment()));
70 }
71
72 if (MetaspaceSize > MaxMetaspaceSize) {
73 FLAG_SET_ERGO(uintx, MetaspaceSize, MaxMetaspaceSize);
74 }
75
76 if (!is_size_aligned(MetaspaceSize, min_alignment())) {
77 FLAG_SET_ERGO(uintx, MetaspaceSize,
78 restricted_align_down(MetaspaceSize, min_alignment()));
79 }
80
81 assert(MetaspaceSize <= MaxMetaspaceSize, "Must be");
82
83 MinMetaspaceExpansion = restricted_align_down(MinMetaspaceExpansion, min_alignment());
84 MaxMetaspaceExpansion = restricted_align_down(MaxMetaspaceExpansion, min_alignment());
85
86 MinHeapDeltaBytes = align_size_up(MinHeapDeltaBytes, min_alignment());
87
88 assert(MetaspaceSize % min_alignment() == 0, "metapace alignment");
89 assert(MaxMetaspaceSize % max_alignment() == 0, "maximum metaspace alignment");
90 if (MetaspaceSize < 256*K) {
91 vm_exit_during_initialization("Too small initial Metaspace size");
92 }
93 }
94
95 void CollectorPolicy::initialize_size_info() {
96 // User inputs from -mx and ms must be aligned
97 set_min_heap_byte_size(align_size_up(Arguments::min_heap_size(), min_alignment()));
98 set_initial_heap_byte_size(align_size_up(InitialHeapSize, min_alignment()));
99 set_max_heap_byte_size(align_size_up(MaxHeapSize, max_alignment()));
100
101 // Check heap parameter properties
102 if (initial_heap_byte_size() < M) {
103 vm_exit_during_initialization("Too small initial heap");
104 }
105 // Check heap parameter properties
106 if (min_heap_byte_size() < M) {
107 vm_exit_during_initialization("Too small minimum heap");
108 }
109 if (initial_heap_byte_size() <= NewSize) {
110 // make sure there is at least some room in old space
111 vm_exit_during_initialization("Too small initial heap for new size specified");
112 }
113 if (max_heap_byte_size() < min_heap_byte_size()) {
114 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified");
115 }
116 if (initial_heap_byte_size() < min_heap_byte_size()) {
117 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified");
118 }
119 if (max_heap_byte_size() < initial_heap_byte_size()) {
120 vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
121 }
122
123 if (PrintGCDetails && Verbose) {
124 gclog_or_tty->print_cr("Minimum heap " SIZE_FORMAT " Initial heap "
125 SIZE_FORMAT " Maximum heap " SIZE_FORMAT,
126 min_heap_byte_size(), initial_heap_byte_size(), max_heap_byte_size());
127 }
128 }
129
130 bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) {
131 bool result = _should_clear_all_soft_refs;
132 set_should_clear_all_soft_refs(false);
133 return result;
134 }
135
136 GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap,
137 int max_covered_regions) {
138 switch (rem_set_name()) {
139 case GenRemSet::CardTable: {
140 CardTableRS* res = new CardTableRS(whole_heap, max_covered_regions);
141 return res;
142 }
143 default:
144 guarantee(false, "unrecognized GenRemSet::Name");
145 return NULL;
146 }
147 }
148
149 void CollectorPolicy::cleared_all_soft_refs() {
150 // If near gc overhear limit, continue to clear SoftRefs. SoftRefs may
151 // have been cleared in the last collection but if the gc overhear
152 // limit continues to be near, SoftRefs should still be cleared.
153 if (size_policy() != NULL) {
154 _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near();
155 }
156 _all_soft_refs_clear = true;
157 }
158
159 size_t CollectorPolicy::compute_max_alignment() {
160 // The card marking array and the offset arrays for old generations are
161 // committed in os pages as well. Make sure they are entirely full (to
162 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
163 // byte entry and the os page size is 4096, the maximum heap size should
164 // be 512*4096 = 2MB aligned.
165
166 // There is only the GenRemSet in Hotspot and only the GenRemSet::CardTable
168 // Requirements of any new remembered set implementations must be added here.
169 size_t alignment = GenRemSet::max_alignment_constraint(GenRemSet::CardTable);
170
171 // Parallel GC does its own alignment of the generations to avoid requiring a
172 // large page (256M on some platforms) for the permanent generation. The
173 // other collectors should also be updated to do their own alignment and then
174 // this use of lcm() should be removed.
175 if (UseLargePages && !UseParallelGC) {
176 // in presence of large pages we have to make sure that our
177 // alignment is large page aware
178 alignment = lcm(os::large_page_size(), alignment);
179 }
180
181 return alignment;
182 }
183
184 // GenCollectorPolicy methods.
185
186 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {
187 size_t x = base_size / (NewRatio+1);
188 size_t new_gen_size = x > min_alignment() ?
189 align_size_down(x, min_alignment()) :
190 min_alignment();
191 return new_gen_size;
192 }
193
194 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,
195 size_t maximum_size) {
196 size_t alignment = min_alignment();
197 size_t max_minus = maximum_size - alignment;
198 return desired_size < max_minus ? desired_size : max_minus;
199 }
200
201
202 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size,
203 size_t init_promo_size,
204 size_t init_survivor_size) {
205 const double max_gc_pause_sec = ((double) MaxGCPauseMillis)/1000.0;
206 _size_policy = new AdaptiveSizePolicy(init_eden_size,
207 init_promo_size,
208 init_survivor_size,
209 max_gc_pause_sec,
210 GCTimeRatio);
211 }
212
213 void GenCollectorPolicy::initialize_flags() {
214 // All sizes must be multiples of the generation granularity.
215 set_min_alignment((uintx) Generation::GenGrain);
216 set_max_alignment(compute_max_alignment());
217
218 CollectorPolicy::initialize_flags();
219
220 // All generational heaps have a youngest gen; handle those flags here.
221
222 // Adjust max size parameters
223 if (NewSize > MaxNewSize) {
224 MaxNewSize = NewSize;
225 }
226 NewSize = align_size_down(NewSize, min_alignment());
227 MaxNewSize = align_size_down(MaxNewSize, min_alignment());
228
229 // Check validity of heap flags
230 assert(NewSize % min_alignment() == 0, "eden space alignment");
231 assert(MaxNewSize % min_alignment() == 0, "survivor space alignment");
232
233 if (NewSize < 3*min_alignment()) {
234 // make sure there room for eden and two survivor spaces
235 vm_exit_during_initialization("Too small new size specified");
236 }
237 if (SurvivorRatio < 1 || NewRatio < 1) {
238 vm_exit_during_initialization("Invalid heap ratio specified");
239 }
240 }
241
242 void TwoGenerationCollectorPolicy::initialize_flags() {
243 GenCollectorPolicy::initialize_flags();
244
245 OldSize = align_size_down(OldSize, min_alignment());
246
247 if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(NewSize)) {
248 // NewRatio will be used later to set the young generation size so we use
249 // it to calculate how big the heap should be based on the requested OldSize
250 // and NewRatio.
251 assert(NewRatio > 0, "NewRatio should have been set up earlier");
252 size_t calculated_heapsize = (OldSize / NewRatio) * (NewRatio + 1);
253
254 calculated_heapsize = align_size_up(calculated_heapsize, max_alignment());
255 MaxHeapSize = calculated_heapsize;
256 InitialHeapSize = calculated_heapsize;
257 }
258 MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
259
260 // adjust max heap size if necessary
261 if (NewSize + OldSize > MaxHeapSize) {
262 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
263 // somebody set a maximum heap size with the intention that we should not
264 // exceed it. Adjust New/OldSize as necessary.
265 uintx calculated_size = NewSize + OldSize;
266 double shrink_factor = (double) MaxHeapSize / calculated_size;
267 // align
268 NewSize = align_size_down((uintx) (NewSize * shrink_factor), min_alignment());
269 // OldSize is already aligned because above we aligned MaxHeapSize to
270 // max_alignment(), and we just made sure that NewSize is aligned to
271 // min_alignment(). In initialize_flags() we verified that max_alignment()
272 // is a multiple of min_alignment().
273 OldSize = MaxHeapSize - NewSize;
274 } else {
275 MaxHeapSize = NewSize + OldSize;
276 }
277 }
278 // need to do this again
279 MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
280
281 // adjust max heap size if necessary
282 if (NewSize + OldSize > MaxHeapSize) {
283 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
284 // somebody set a maximum heap size with the intention that we should not
285 // exceed it. Adjust New/OldSize as necessary.
286 uintx calculated_size = NewSize + OldSize;
287 double shrink_factor = (double) MaxHeapSize / calculated_size;
288 // align
289 NewSize = align_size_down((uintx) (NewSize * shrink_factor), min_alignment());
290 // OldSize is already aligned because above we aligned MaxHeapSize to
291 // max_alignment(), and we just made sure that NewSize is aligned to
292 // min_alignment(). In initialize_flags() we verified that max_alignment()
293 // is a multiple of min_alignment().
294 OldSize = MaxHeapSize - NewSize;
295 } else {
296 MaxHeapSize = NewSize + OldSize;
297 }
298 }
299 // need to do this again
300 MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
301
302 always_do_update_barrier = UseConcMarkSweepGC;
303
304 // Check validity of heap flags
305 assert(OldSize % min_alignment() == 0, "old space alignment");
306 assert(MaxHeapSize % max_alignment() == 0, "maximum heap alignment");
307 }
308
309 // Values set on the command line win over any ergonomically
310 // set command line parameters.
311 // Ergonomic choice of parameters are done before this
312 // method is called. Values for command line parameters such as NewSize
313 // and MaxNewSize feed those ergonomic choices into this method.
314 // This method makes the final generation sizings consistent with
315 // themselves and with overall heap sizings.
316 // In the absence of explicitly set command line flags, policies
317 // such as the use of NewRatio are used to size the generation.
318 void GenCollectorPolicy::initialize_size_info() {
319 CollectorPolicy::initialize_size_info();
320
321 // min_alignment() is used for alignment within a generation.
322 // There is additional alignment done down stream for some
323 // collectors that sometimes causes unwanted rounding up of
324 // generations sizes.
325
326 // Determine maximum size of gen0
327
328 size_t max_new_size = 0;
329 if (FLAG_IS_CMDLINE(MaxNewSize) || FLAG_IS_ERGO(MaxNewSize)) {
330 if (MaxNewSize < min_alignment()) {
331 max_new_size = min_alignment();
332 }
333 if (MaxNewSize >= max_heap_byte_size()) {
334 max_new_size = align_size_down(max_heap_byte_size() - min_alignment(),
335 min_alignment());
336 warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or "
337 "greater than the entire heap (" SIZE_FORMAT "k). A "
338 "new generation size of " SIZE_FORMAT "k will be used.",
339 MaxNewSize/K, max_heap_byte_size()/K, max_new_size/K);
340 } else {
341 max_new_size = align_size_down(MaxNewSize, min_alignment());
342 }
343
344 // The case for FLAG_IS_ERGO(MaxNewSize) could be treated
345 // specially at this point to just use an ergonomically set
346 // MaxNewSize to set max_new_size. For cases with small
347 // heaps such a policy often did not work because the MaxNewSize
348 // was larger than the entire heap. The interpretation given
349 // to ergonomically set flags is that the flags are set
350 // by different collectors for their own special needs but
351 // are not allowed to badly shape the heap. This allows the
352 // different collectors to decide what's best for themselves
353 // without having to factor in the overall heap shape. It
354 // can be the case in the future that the collectors would
355 // only make "wise" ergonomics choices and this policy could
356 // just accept those choices. The choices currently made are
357 // not always "wise".
358 } else {
359 max_new_size = scale_by_NewRatio_aligned(max_heap_byte_size());
360 // Bound the maximum size by NewSize below (since it historically
361 // would have been NewSize and because the NewRatio calculation could
362 // yield a size that is too small) and bound it by MaxNewSize above.
363 // Ergonomics plays here by previously calculating the desired
364 // NewSize and MaxNewSize.
365 max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize);
366 }
367 assert(max_new_size > 0, "All paths should set max_new_size");
368
369 // Given the maximum gen0 size, determine the initial and
370 // minimum gen0 sizes.
371
372 if (max_heap_byte_size() == min_heap_byte_size()) {
373 // The maximum and minimum heap sizes are the same so
374 // the generations minimum and initial must be the
375 // same as its maximum.
376 set_min_gen0_size(max_new_size);
377 set_initial_gen0_size(max_new_size);
378 set_max_gen0_size(max_new_size);
379 } else {
380 size_t desired_new_size = 0;
381 if (!FLAG_IS_DEFAULT(NewSize)) {
382 // If NewSize is set ergonomically (for example by cms), it
383 // would make sense to use it. If it is used, also use it
384 // to set the initial size. Although there is no reason
385 // the minimum size and the initial size have to be the same,
386 // the current implementation gets into trouble during the calculation
387 // of the tenured generation sizes if they are different.
388 // Note that this makes the initial size and the minimum size
389 // generally small compared to the NewRatio calculation.
390 _min_gen0_size = NewSize;
391 desired_new_size = NewSize;
392 max_new_size = MAX2(max_new_size, NewSize);
393 } else {
394 // For the case where NewSize is the default, use NewRatio
395 // to size the minimum and initial generation sizes.
396 // Use the default NewSize as the floor for these values. If
397 // NewRatio is overly large, the resulting sizes can be too
398 // small.
399 _min_gen0_size = MAX2(scale_by_NewRatio_aligned(min_heap_byte_size()),
400 NewSize);
401 desired_new_size =
402 MAX2(scale_by_NewRatio_aligned(initial_heap_byte_size()),
403 NewSize);
404 }
405
406 assert(_min_gen0_size > 0, "Sanity check");
407 set_initial_gen0_size(desired_new_size);
408 set_max_gen0_size(max_new_size);
409
410 // At this point the desirable initial and minimum sizes have been
411 // determined without regard to the maximum sizes.
412
413 // Bound the sizes by the corresponding overall heap sizes.
414 set_min_gen0_size(
415 bound_minus_alignment(_min_gen0_size, min_heap_byte_size()));
416 set_initial_gen0_size(
417 bound_minus_alignment(_initial_gen0_size, initial_heap_byte_size()));
418 set_max_gen0_size(
419 bound_minus_alignment(_max_gen0_size, max_heap_byte_size()));
420
421 // At this point all three sizes have been checked against the
422 // maximum sizes but have not been checked for consistency
423 // among the three.
424
425 // Final check min <= initial <= max
426 set_min_gen0_size(MIN2(_min_gen0_size, _max_gen0_size));
427 set_initial_gen0_size(
428 MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size));
429 set_min_gen0_size(MIN2(_min_gen0_size, _initial_gen0_size));
430 }
431
432 if (PrintGCDetails && Verbose) {
433 gclog_or_tty->print_cr("1: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
434 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
435 min_gen0_size(), initial_gen0_size(), max_gen0_size());
436 }
437 }
438
439 // Call this method during the sizing of the gen1 to make
440 // adjustments to gen0 because of gen1 sizing policy. gen0 initially has
441 // the most freedom in sizing because it is done before the
442 // policy for gen1 is applied. Once gen1 policies have been applied,
443 // there may be conflicts in the shape of the heap and this method
444 // is used to make the needed adjustments. The application of the
445 // policies could be more sophisticated (iterative for example) but
446 // keeping it simple also seems a worthwhile goal.
447 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr,
448 size_t* gen1_size_ptr,
449 const size_t heap_size,
450 const size_t min_gen1_size) {
451 bool result = false;
452
453 if ((*gen1_size_ptr + *gen0_size_ptr) > heap_size) {
454 if ((heap_size < (*gen0_size_ptr + min_gen1_size)) &&
455 (heap_size >= min_gen1_size + min_alignment())) {
456 // Adjust gen0 down to accommodate min_gen1_size
457 *gen0_size_ptr = heap_size - min_gen1_size;
458 *gen0_size_ptr =
459 MAX2((uintx)align_size_down(*gen0_size_ptr, min_alignment()),
460 min_alignment());
461 assert(*gen0_size_ptr > 0, "Min gen0 is too large");
462 result = true;
463 } else {
464 *gen1_size_ptr = heap_size - *gen0_size_ptr;
465 *gen1_size_ptr =
466 MAX2((uintx)align_size_down(*gen1_size_ptr, min_alignment()),
467 min_alignment());
468 }
469 }
470 return result;
471 }
472
473 // Minimum sizes of the generations may be different than
474 // the initial sizes. An inconsistently is permitted here
475 // in the total size that can be specified explicitly by
476 // command line specification of OldSize and NewSize and
477 // also a command line specification of -Xms. Issue a warning
478 // but allow the values to pass.
479
480 void TwoGenerationCollectorPolicy::initialize_size_info() {
481 GenCollectorPolicy::initialize_size_info();
482
483 // At this point the minimum, initial and maximum sizes
484 // of the overall heap and of gen0 have been determined.
485 // The maximum gen1 size can be determined from the maximum gen0
486 // and maximum heap size since no explicit flags exits
487 // for setting the gen1 maximum.
488 _max_gen1_size = max_heap_byte_size() - _max_gen0_size;
489 _max_gen1_size =
490 MAX2((uintx)align_size_down(_max_gen1_size, min_alignment()),
491 min_alignment());
492 // If no explicit command line flag has been set for the
493 // gen1 size, use what is left for gen1.
494 if (FLAG_IS_DEFAULT(OldSize) || FLAG_IS_ERGO(OldSize)) {
495 // The user has not specified any value or ergonomics
496 // has chosen a value (which may or may not be consistent
497 // with the overall heap size). In either case make
498 // the minimum, maximum and initial sizes consistent
499 // with the gen0 sizes and the overall heap sizes.
500 assert(min_heap_byte_size() > _min_gen0_size,
501 "gen0 has an unexpected minimum size");
502 set_min_gen1_size(min_heap_byte_size() - min_gen0_size());
503 set_min_gen1_size(
504 MAX2((uintx)align_size_down(_min_gen1_size, min_alignment()),
505 min_alignment()));
506 set_initial_gen1_size(initial_heap_byte_size() - initial_gen0_size());
507 set_initial_gen1_size(
508 MAX2((uintx)align_size_down(_initial_gen1_size, min_alignment()),
509 min_alignment()));
510
511 } else {
512 // It's been explicitly set on the command line. Use the
513 // OldSize and then determine the consequences.
514 set_min_gen1_size(OldSize);
515 set_initial_gen1_size(OldSize);
516
517 // If the user has explicitly set an OldSize that is inconsistent
518 // with other command line flags, issue a warning.
519 // The generation minimums and the overall heap mimimum should
520 // be within one heap alignment.
521 if ((_min_gen1_size + _min_gen0_size + min_alignment()) <
522 min_heap_byte_size()) {
523 warning("Inconsistency between minimum heap size and minimum "
524 "generation sizes: using minimum heap = " SIZE_FORMAT,
525 min_heap_byte_size());
526 }
527 if ((OldSize > _max_gen1_size)) {
528 warning("Inconsistency between maximum heap size and maximum "
529 "generation sizes: using maximum heap = " SIZE_FORMAT
530 " -XX:OldSize flag is being ignored",
531 max_heap_byte_size());
532 }
533 // If there is an inconsistency between the OldSize and the minimum and/or
534 // initial size of gen0, since OldSize was explicitly set, OldSize wins.
535 if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size,
536 min_heap_byte_size(), OldSize)) {
537 if (PrintGCDetails && Verbose) {
538 gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
539 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
540 min_gen0_size(), initial_gen0_size(), max_gen0_size());
541 }
542 }
543 // Initial size
544 if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,
545 initial_heap_byte_size(), OldSize)) {
546 if (PrintGCDetails && Verbose) {
547 gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
548 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
549 min_gen0_size(), initial_gen0_size(), max_gen0_size());
550 }
551 }
552 }
553 // Enforce the maximum gen1 size.
554 set_min_gen1_size(MIN2(_min_gen1_size, _max_gen1_size));
555
556 // Check that min gen1 <= initial gen1 <= max gen1
557 set_initial_gen1_size(MAX2(_initial_gen1_size, _min_gen1_size));
558 set_initial_gen1_size(MIN2(_initial_gen1_size, _max_gen1_size));
559
560 if (PrintGCDetails && Verbose) {
561 gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 "
562 SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT,
563 min_gen1_size(), initial_gen1_size(), max_gen1_size());
564 }
565 }
566
567 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
568 bool is_tlab,
569 bool* gc_overhead_limit_was_exceeded) {
570 GenCollectedHeap *gch = GenCollectedHeap::heap();
571
572 debug_only(gch->check_for_valid_allocation_state());
573 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
574
575 // In general gc_overhead_limit_was_exceeded should be false so
576 // set it so here and reset it to true only if the gc time
577 // limit is being exceeded as checked below.
578 *gc_overhead_limit_was_exceeded = false;
579
580 HeapWord* result = NULL;
581
582 // Loop until the allocation is satisified,
583 // or unsatisfied after GC.
584 for (int try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) {
585 HandleMark hm; // discard any handles allocated in each iteration
586
587 // First allocation attempt is lock-free.
588 Generation *gen0 = gch->get_gen(0);
589 assert(gen0->supports_inline_contig_alloc(),
590 "Otherwise, must do alloc within heap lock");
591 if (gen0->should_allocate(size, is_tlab)) {
592 result = gen0->par_allocate(size, is_tlab);
593 if (result != NULL) {
594 assert(gch->is_in_reserved(result), "result not in heap");
595 return result;
596 }
597 }
598 unsigned int gc_count_before; // read inside the Heap_lock locked region
599 {
600 MutexLocker ml(Heap_lock);
601 if (PrintGC && Verbose) {
602 gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:"
603 " attempting locked slow path allocation");
638 JavaThread* jthr = JavaThread::current();
639 if (!jthr->in_critical()) {
640 MutexUnlocker mul(Heap_lock);
641 // Wait for JNI critical section to be exited
642 GC_locker::stall_until_clear();
643 gclocker_stalled_count += 1;
644 continue;
645 } else {
646 if (CheckJNICalls) {
647 fatal("Possible deadlock due to allocating while"
648 " in jni critical section");
649 }
650 return NULL;
651 }
652 }
653
654 // Read the gc count while the heap lock is held.
655 gc_count_before = Universe::heap()->total_collections();
656 }
657
658 VM_GenCollectForAllocation op(size,
659 is_tlab,
660 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);
875 bool GenCollectorPolicy::should_try_older_generation_allocation(
876 size_t word_size) const {
877 GenCollectedHeap* gch = GenCollectedHeap::heap();
878 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();
879 return (word_size > heap_word_size(gen0_capacity))
880 || GC_locker::is_active_and_needs_gc()
881 || gch->incremental_collection_failed();
882 }
883
884
885 //
886 // MarkSweepPolicy methods
887 //
888
889 MarkSweepPolicy::MarkSweepPolicy() {
890 initialize_all();
891 }
892
893 void MarkSweepPolicy::initialize_generations() {
894 _generations = NEW_C_HEAP_ARRAY3(GenerationSpecPtr, number_of_generations(), mtGC, 0, AllocFailStrategy::RETURN_NULL);
895 if (_generations == NULL)
896 vm_exit_during_initialization("Unable to allocate gen spec");
897
898 if (UseParNewGC) {
899 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);
900 } else {
901 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);
902 }
903 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);
904
905 if (_generations[0] == NULL || _generations[1] == NULL)
906 vm_exit_during_initialization("Unable to allocate gen spec");
907 }
908
909 void MarkSweepPolicy::initialize_gc_policy_counters() {
910 // initialize the policy counters - 2 collectors, 3 generations
911 if (UseParNewGC) {
912 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);
913 } else {
914 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
915 }
916 }
|
36 #include "runtime/arguments.hpp"
37 #include "runtime/globals_extension.hpp"
38 #include "runtime/handles.inline.hpp"
39 #include "runtime/java.hpp"
40 #include "runtime/thread.inline.hpp"
41 #include "runtime/vmThread.hpp"
42 #include "utilities/macros.hpp"
43 #if INCLUDE_ALL_GCS
44 #include "gc_implementation/concurrentMarkSweep/cmsAdaptiveSizePolicy.hpp"
45 #include "gc_implementation/concurrentMarkSweep/cmsGCAdaptivePolicyCounters.hpp"
46 #endif // INCLUDE_ALL_GCS
47
48 // CollectorPolicy methods.
49
50 // Align down. If the aligning result in 0, return 'alignment'.
51 static size_t restricted_align_down(size_t size, size_t alignment) {
52 return MAX2(alignment, align_size_down_(size, alignment));
53 }
54
55 void CollectorPolicy::initialize_flags() {
56 assert(_max_alignment >= _min_alignment,
57 err_msg("max_alignment: " SIZE_FORMAT " less than min_alignment: " SIZE_FORMAT,
58 _max_alignment, _min_alignment));
59 assert(_max_alignment % _min_alignment == 0,
60 err_msg("max_alignment: " SIZE_FORMAT " not aligned by min_alignment: " SIZE_FORMAT,
61 _max_alignment, _min_alignment));
62
63 if (MaxHeapSize < InitialHeapSize) {
64 vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
65 }
66
67 if (!is_size_aligned(MaxMetaspaceSize, _max_alignment)) {
68 FLAG_SET_ERGO(uintx, MaxMetaspaceSize,
69 restricted_align_down(MaxMetaspaceSize, _max_alignment));
70 }
71
72 if (MetaspaceSize > MaxMetaspaceSize) {
73 FLAG_SET_ERGO(uintx, MetaspaceSize, MaxMetaspaceSize);
74 }
75
76 if (!is_size_aligned(MetaspaceSize, _min_alignment)) {
77 FLAG_SET_ERGO(uintx, MetaspaceSize,
78 restricted_align_down(MetaspaceSize, _min_alignment));
79 }
80
81 assert(MetaspaceSize <= MaxMetaspaceSize, "Must be");
82
83 MinMetaspaceExpansion = restricted_align_down(MinMetaspaceExpansion, _min_alignment);
84 MaxMetaspaceExpansion = restricted_align_down(MaxMetaspaceExpansion, _min_alignment);
85
86 MinHeapDeltaBytes = align_size_up(MinHeapDeltaBytes, _min_alignment);
87
88 assert(MetaspaceSize % _min_alignment == 0, "metapace alignment");
89 assert(MaxMetaspaceSize % _max_alignment == 0, "maximum metaspace alignment");
90 if (MetaspaceSize < 256*K) {
91 vm_exit_during_initialization("Too small initial Metaspace size");
92 }
93 }
94
95 void CollectorPolicy::initialize_size_info() {
96 // User inputs from -mx and ms must be aligned
97 _min_heap_byte_size = align_size_up(Arguments::min_heap_size(), _min_alignment);
98 _initial_heap_byte_size = align_size_up(InitialHeapSize, _min_alignment);
99 _max_heap_byte_size = align_size_up(MaxHeapSize, _max_alignment);
100
101 // Check heap parameter properties
102 if (_initial_heap_byte_size < M) {
103 vm_exit_during_initialization("Too small initial heap");
104 }
105 // Check heap parameter properties
106 if (_min_heap_byte_size < M) {
107 vm_exit_during_initialization("Too small minimum heap");
108 }
109 if (_initial_heap_byte_size <= NewSize) {
110 // make sure there is at least some room in old space
111 vm_exit_during_initialization("Too small initial heap for new size specified");
112 }
113 if (_max_heap_byte_size < _min_heap_byte_size) {
114 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified");
115 }
116 if (_initial_heap_byte_size < _min_heap_byte_size) {
117 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified");
118 }
119 if (_max_heap_byte_size < _initial_heap_byte_size) {
120 vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
121 }
122
123 if (PrintGCDetails && Verbose) {
124 gclog_or_tty->print_cr("Minimum heap " SIZE_FORMAT " Initial heap "
125 SIZE_FORMAT " Maximum heap " SIZE_FORMAT,
126 _min_heap_byte_size, _initial_heap_byte_size, _max_heap_byte_size);
127 }
128 }
129
130 bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) {
131 bool result = _should_clear_all_soft_refs;
132 set_should_clear_all_soft_refs(false);
133 return result;
134 }
135
136 GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap,
137 int max_covered_regions) {
138 assert(rem_set_name() == GenRemSet::CardTable, "unrecognized GenRemSet::Name");
139 return new CardTableRS(whole_heap, max_covered_regions);
140 }
141
142 void CollectorPolicy::cleared_all_soft_refs() {
143 // If near gc overhear limit, continue to clear SoftRefs. SoftRefs may
144 // have been cleared in the last collection but if the gc overhear
145 // limit continues to be near, SoftRefs should still be cleared.
146 if (size_policy() != NULL) {
147 _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near();
148 }
149 _all_soft_refs_clear = true;
150 }
151
152 size_t CollectorPolicy::compute_max_alignment() {
153 // The card marking array and the offset arrays for old generations are
154 // committed in os pages as well. Make sure they are entirely full (to
155 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
156 // byte entry and the os page size is 4096, the maximum heap size should
157 // be 512*4096 = 2MB aligned.
158
159 // There is only the GenRemSet in Hotspot and only the GenRemSet::CardTable
161 // Requirements of any new remembered set implementations must be added here.
162 size_t alignment = GenRemSet::max_alignment_constraint(GenRemSet::CardTable);
163
164 // Parallel GC does its own alignment of the generations to avoid requiring a
165 // large page (256M on some platforms) for the permanent generation. The
166 // other collectors should also be updated to do their own alignment and then
167 // this use of lcm() should be removed.
168 if (UseLargePages && !UseParallelGC) {
169 // in presence of large pages we have to make sure that our
170 // alignment is large page aware
171 alignment = lcm(os::large_page_size(), alignment);
172 }
173
174 return alignment;
175 }
176
177 // GenCollectorPolicy methods.
178
179 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {
180 size_t x = base_size / (NewRatio+1);
181 size_t new_gen_size = x > _min_alignment ?
182 align_size_down(x, _min_alignment) :
183 _min_alignment;
184 return new_gen_size;
185 }
186
187 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,
188 size_t maximum_size) {
189 size_t alignment = _min_alignment;
190 size_t max_minus = maximum_size - alignment;
191 return desired_size < max_minus ? desired_size : max_minus;
192 }
193
194
195 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size,
196 size_t init_promo_size,
197 size_t init_survivor_size) {
198 const double max_gc_pause_sec = ((double) MaxGCPauseMillis)/1000.0;
199 _size_policy = new AdaptiveSizePolicy(init_eden_size,
200 init_promo_size,
201 init_survivor_size,
202 max_gc_pause_sec,
203 GCTimeRatio);
204 }
205
206 void GenCollectorPolicy::initialize_flags() {
207 // All sizes must be multiples of the generation granularity.
208 _min_alignment = (uintx) Generation::GenGrain;
209 _max_alignment = compute_max_alignment();
210
211 CollectorPolicy::initialize_flags();
212
213 // All generational heaps have a youngest gen; handle those flags here.
214
215 // Adjust max size parameters
216 if (NewSize > MaxNewSize) {
217 MaxNewSize = NewSize;
218 }
219 NewSize = align_size_down(NewSize, _min_alignment);
220 MaxNewSize = align_size_down(MaxNewSize, _min_alignment);
221
222 // Check validity of heap flags
223 assert(NewSize % _min_alignment == 0, "eden space alignment");
224 assert(MaxNewSize % _min_alignment == 0, "survivor space alignment");
225
226 if (NewSize < 3 * _min_alignment) {
227 // make sure there room for eden and two survivor spaces
228 vm_exit_during_initialization("Too small new size specified");
229 }
230 if (SurvivorRatio < 1 || NewRatio < 1) {
231 vm_exit_during_initialization("Invalid young gen ratio specified");
232 }
233 }
234
235 void TwoGenerationCollectorPolicy::initialize_flags() {
236 GenCollectorPolicy::initialize_flags();
237
238 OldSize = align_size_down(OldSize, _min_alignment);
239
240 if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(NewSize)) {
241 // NewRatio will be used later to set the young generation size so we use
242 // it to calculate how big the heap should be based on the requested OldSize
243 // and NewRatio.
244 assert(NewRatio > 0, "NewRatio should have been set up earlier");
245 size_t calculated_heapsize = (OldSize / NewRatio) * (NewRatio + 1);
246
247 calculated_heapsize = align_size_up(calculated_heapsize, _max_alignment);
248 MaxHeapSize = calculated_heapsize;
249 InitialHeapSize = calculated_heapsize;
250 }
251 MaxHeapSize = align_size_up(MaxHeapSize, _max_alignment);
252
253 // adjust max heap size if necessary
254 if (NewSize + OldSize > MaxHeapSize) {
255 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
256 // somebody set a maximum heap size with the intention that we should not
257 // exceed it. Adjust New/OldSize as necessary.
258 uintx calculated_size = NewSize + OldSize;
259 double shrink_factor = (double) MaxHeapSize / calculated_size;
260 // align
261 NewSize = align_size_down((uintx) (NewSize * shrink_factor), _min_alignment);
262 // OldSize is already aligned because above we aligned MaxHeapSize to
263 // _max_alignment, and we just made sure that NewSize is aligned to
264 // _min_alignment. In initialize_flags() we verified that _max_alignment
265 // is a multiple of _min_alignment.
266 OldSize = MaxHeapSize - NewSize;
267 } else {
268 MaxHeapSize = NewSize + OldSize;
269 }
270 }
271 // need to do this again
272 MaxHeapSize = align_size_up(MaxHeapSize, _max_alignment);
273
274 // adjust max heap size if necessary
275 if (NewSize + OldSize > MaxHeapSize) {
276 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
277 // somebody set a maximum heap size with the intention that we should not
278 // exceed it. Adjust New/OldSize as necessary.
279 uintx calculated_size = NewSize + OldSize;
280 double shrink_factor = (double) MaxHeapSize / calculated_size;
281 // align
282 NewSize = align_size_down((uintx) (NewSize * shrink_factor), _min_alignment);
283 // OldSize is already aligned because above we aligned MaxHeapSize to
284 // _max_alignment, and we just made sure that NewSize is aligned to
285 // _min_alignment. In initialize_flags() we verified that _max_alignment
286 // is a multiple of _min_alignment.
287 OldSize = MaxHeapSize - NewSize;
288 } else {
289 MaxHeapSize = NewSize + OldSize;
290 }
291 }
292 // need to do this again
293 MaxHeapSize = align_size_up(MaxHeapSize, _max_alignment);
294
295 always_do_update_barrier = UseConcMarkSweepGC;
296
297 // Check validity of heap flags
298 assert(OldSize % _min_alignment == 0, "old space alignment");
299 assert(MaxHeapSize % _max_alignment == 0, "maximum heap alignment");
300 }
301
302 // Values set on the command line win over any ergonomically
303 // set command line parameters.
304 // Ergonomic choice of parameters are done before this
305 // method is called. Values for command line parameters such as NewSize
306 // and MaxNewSize feed those ergonomic choices into this method.
307 // This method makes the final generation sizings consistent with
308 // themselves and with overall heap sizings.
309 // In the absence of explicitly set command line flags, policies
310 // such as the use of NewRatio are used to size the generation.
311 void GenCollectorPolicy::initialize_size_info() {
312 CollectorPolicy::initialize_size_info();
313
314 // _min_alignment is used for alignment within a generation.
315 // There is additional alignment done down stream for some
316 // collectors that sometimes causes unwanted rounding up of
317 // generations sizes.
318
319 // Determine maximum size of gen0
320
321 size_t max_new_size = 0;
322 if (FLAG_IS_CMDLINE(MaxNewSize) || FLAG_IS_ERGO(MaxNewSize)) {
323 if (MaxNewSize < _min_alignment) {
324 max_new_size = _min_alignment;
325 }
326 if (MaxNewSize >= _max_heap_byte_size) {
327 max_new_size = align_size_down(_max_heap_byte_size - _min_alignment,
328 _min_alignment);
329 warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or "
330 "greater than the entire heap (" SIZE_FORMAT "k). A "
331 "new generation size of " SIZE_FORMAT "k will be used.",
332 MaxNewSize/K, _max_heap_byte_size/K, max_new_size/K);
333 } else {
334 max_new_size = align_size_down(MaxNewSize, _min_alignment);
335 }
336
337 // The case for FLAG_IS_ERGO(MaxNewSize) could be treated
338 // specially at this point to just use an ergonomically set
339 // MaxNewSize to set max_new_size. For cases with small
340 // heaps such a policy often did not work because the MaxNewSize
341 // was larger than the entire heap. The interpretation given
342 // to ergonomically set flags is that the flags are set
343 // by different collectors for their own special needs but
344 // are not allowed to badly shape the heap. This allows the
345 // different collectors to decide what's best for themselves
346 // without having to factor in the overall heap shape. It
347 // can be the case in the future that the collectors would
348 // only make "wise" ergonomics choices and this policy could
349 // just accept those choices. The choices currently made are
350 // not always "wise".
351 } else {
352 max_new_size = scale_by_NewRatio_aligned(_max_heap_byte_size);
353 // Bound the maximum size by NewSize below (since it historically
354 // would have been NewSize and because the NewRatio calculation could
355 // yield a size that is too small) and bound it by MaxNewSize above.
356 // Ergonomics plays here by previously calculating the desired
357 // NewSize and MaxNewSize.
358 max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize);
359 }
360 assert(max_new_size > 0, "All paths should set max_new_size");
361
362 // Given the maximum gen0 size, determine the initial and
363 // minimum gen0 sizes.
364
365 if (_max_heap_byte_size == _min_heap_byte_size) {
366 // The maximum and minimum heap sizes are the same so
367 // the generations minimum and initial must be the
368 // same as its maximum.
369 _min_gen0_size = max_new_size;
370 _initial_gen0_size = max_new_size;
371 _max_gen0_size = max_new_size;
372 } else {
373 size_t desired_new_size = 0;
374 if (!FLAG_IS_DEFAULT(NewSize)) {
375 // If NewSize is set ergonomically (for example by cms), it
376 // would make sense to use it. If it is used, also use it
377 // to set the initial size. Although there is no reason
378 // the minimum size and the initial size have to be the same,
379 // the current implementation gets into trouble during the calculation
380 // of the tenured generation sizes if they are different.
381 // Note that this makes the initial size and the minimum size
382 // generally small compared to the NewRatio calculation.
383 _min_gen0_size = NewSize;
384 desired_new_size = NewSize;
385 max_new_size = MAX2(max_new_size, NewSize);
386 } else {
387 // For the case where NewSize is the default, use NewRatio
388 // to size the minimum and initial generation sizes.
389 // Use the default NewSize as the floor for these values. If
390 // NewRatio is overly large, the resulting sizes can be too
391 // small.
392 _min_gen0_size = MAX2(scale_by_NewRatio_aligned(_min_heap_byte_size), NewSize);
393 desired_new_size =
394 MAX2(scale_by_NewRatio_aligned(_initial_heap_byte_size), NewSize);
395 }
396
397 assert(_min_gen0_size > 0, "Sanity check");
398 _initial_gen0_size = desired_new_size;
399 _max_gen0_size = max_new_size;
400
401 // At this point the desirable initial and minimum sizes have been
402 // determined without regard to the maximum sizes.
403
404 // Bound the sizes by the corresponding overall heap sizes.
405 _min_gen0_size = bound_minus_alignment(_min_gen0_size, _min_heap_byte_size);
406 _initial_gen0_size = bound_minus_alignment(_initial_gen0_size, _initial_heap_byte_size);
407 _max_gen0_size = bound_minus_alignment(_max_gen0_size, _max_heap_byte_size);
408
409 // At this point all three sizes have been checked against the
410 // maximum sizes but have not been checked for consistency
411 // among the three.
412
413 // Final check min <= initial <= max
414 _min_gen0_size = MIN2(_min_gen0_size, _max_gen0_size);
415 _initial_gen0_size = MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size);
416 _min_gen0_size = MIN2(_min_gen0_size, _initial_gen0_size);
417 }
418
419 if (PrintGCDetails && Verbose) {
420 gclog_or_tty->print_cr("1: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
421 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
422 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
423 }
424 }
425
426 // Call this method during the sizing of the gen1 to make
427 // adjustments to gen0 because of gen1 sizing policy. gen0 initially has
428 // the most freedom in sizing because it is done before the
429 // policy for gen1 is applied. Once gen1 policies have been applied,
430 // there may be conflicts in the shape of the heap and this method
431 // is used to make the needed adjustments. The application of the
432 // policies could be more sophisticated (iterative for example) but
433 // keeping it simple also seems a worthwhile goal.
434 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr,
435 size_t* gen1_size_ptr,
436 const size_t heap_size,
437 const size_t min_gen1_size) {
438 bool result = false;
439
440 if ((*gen1_size_ptr + *gen0_size_ptr) > heap_size) {
441 if ((heap_size < (*gen0_size_ptr + min_gen1_size)) &&
442 (heap_size >= min_gen1_size + _min_alignment)) {
443 // Adjust gen0 down to accommodate min_gen1_size
444 *gen0_size_ptr = heap_size - min_gen1_size;
445 *gen0_size_ptr =
446 MAX2((uintx)align_size_down(*gen0_size_ptr, _min_alignment), _min_alignment);
447 assert(*gen0_size_ptr > 0, "Min gen0 is too large");
448 result = true;
449 } else {
450 *gen1_size_ptr = heap_size - *gen0_size_ptr;
451 *gen1_size_ptr =
452 MAX2((uintx)align_size_down(*gen1_size_ptr, _min_alignment), _min_alignment);
453 }
454 }
455 return result;
456 }
457
458 // Minimum sizes of the generations may be different than
459 // the initial sizes. An inconsistency is permitted here
460 // in the total size that can be specified explicitly by
461 // command line specification of OldSize and NewSize and
462 // also a command line specification of -Xms. Issue a warning
463 // but allow the values to pass.
464
465 void TwoGenerationCollectorPolicy::initialize_size_info() {
466 GenCollectorPolicy::initialize_size_info();
467
468 // At this point the minimum, initial and maximum sizes
469 // of the overall heap and of gen0 have been determined.
470 // The maximum gen1 size can be determined from the maximum gen0
471 // and maximum heap size since no explicit flags exist
472 // for setting the gen1 maximum.
473 _max_gen1_size = _max_heap_byte_size - _max_gen0_size;
474 _max_gen1_size =
475 MAX2((uintx)align_size_down(_max_gen1_size, _min_alignment), _min_alignment);
476 // If no explicit command line flag has been set for the
477 // gen1 size, use what is left for gen1.
478 if (FLAG_IS_DEFAULT(OldSize) || FLAG_IS_ERGO(OldSize)) {
479 // The user has not specified any value or ergonomics
480 // has chosen a value (which may or may not be consistent
481 // with the overall heap size). In either case make
482 // the minimum, maximum and initial sizes consistent
483 // with the gen0 sizes and the overall heap sizes.
484 assert(_min_heap_byte_size > _min_gen0_size,
485 "gen0 has an unexpected minimum size");
486 _min_gen1_size = _min_heap_byte_size - _min_gen0_size;
487 _min_gen1_size = MAX2((uintx)align_size_down(_min_gen1_size, _min_alignment),
488 _min_alignment);
489 _initial_gen1_size = _initial_heap_byte_size - _initial_gen0_size;
490 _initial_gen1_size = MAX2((uintx)align_size_down(_initial_gen1_size, _min_alignment),
491 _min_alignment);
492 } else {
493 // OldSize has been explicitly set on the command line. Use the
494 // OldSize and then determine the consequences.
495 _min_gen1_size = OldSize;
496 _initial_gen1_size = OldSize;
497
498 // If the user has explicitly set an OldSize that is inconsistent
499 // with other command line flags, issue a warning.
500 // The generation minimums and the overall heap minimum should
501 // be within one heap alignment.
502 if ((_min_gen1_size + _min_gen0_size + _min_alignment) < _min_heap_byte_size) {
503 warning("Inconsistency between minimum heap size and minimum "
504 "generation sizes: using minimum heap = " SIZE_FORMAT,
505 _min_heap_byte_size);
506 }
507 if (OldSize > _max_gen1_size) {
508 warning("Inconsistency between maximum heap size and maximum "
509 "generation sizes: using maximum heap = " SIZE_FORMAT
510 " -XX:OldSize flag is being ignored",
511 _max_heap_byte_size);
512 }
513 // If there is an inconsistency between the OldSize and the minimum and/or
514 // initial size of gen0, since OldSize was explicitly set, OldSize wins.
515 if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size,
516 _min_heap_byte_size, OldSize)) {
517 if (PrintGCDetails && Verbose) {
518 gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
519 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
520 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
521 }
522 }
523 // The same as above for the old gen initial size
524 if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,
525 _initial_heap_byte_size, OldSize)) {
526 if (PrintGCDetails && Verbose) {
527 gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
528 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
529 _min_gen0_size, _initial_gen0_size, _max_gen0_size);
530 }
531 }
532 }
533
534 _min_gen1_size = MIN2(_min_gen1_size, _max_gen1_size);
535
536 // Make sure that min gen1 <= initial gen1 <= max gen1
537 _initial_gen1_size = MAX2(_initial_gen1_size, _min_gen1_size);
538 _initial_gen1_size = MIN2(_initial_gen1_size, _max_gen1_size);
539
540 if (PrintGCDetails && Verbose) {
541 gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 "
542 SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT,
543 _min_gen1_size, _initial_gen1_size, _max_gen1_size);
544 }
545 }
546
547 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
548 bool is_tlab,
549 bool* gc_overhead_limit_was_exceeded) {
550 GenCollectedHeap *gch = GenCollectedHeap::heap();
551
552 debug_only(gch->check_for_valid_allocation_state());
553 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
554
555 // In general gc_overhead_limit_was_exceeded should be false so
556 // set it so here and reset it to true only if the gc time
557 // limit is being exceeded as checked below.
558 *gc_overhead_limit_was_exceeded = false;
559
560 HeapWord* result = NULL;
561
562 // Loop until the allocation is satisfied, or unsatisfied after GC.
563 for (int try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) {
564 HandleMark hm; // discard any handles allocated in each iteration
565
566 // First allocation attempt is lock-free.
567 Generation *gen0 = gch->get_gen(0);
568 assert(gen0->supports_inline_contig_alloc(),
569 "Otherwise, must do alloc within heap lock");
570 if (gen0->should_allocate(size, is_tlab)) {
571 result = gen0->par_allocate(size, is_tlab);
572 if (result != NULL) {
573 assert(gch->is_in_reserved(result), "result not in heap");
574 return result;
575 }
576 }
577 unsigned int gc_count_before; // read inside the Heap_lock locked region
578 {
579 MutexLocker ml(Heap_lock);
580 if (PrintGC && Verbose) {
581 gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:"
582 " attempting locked slow path allocation");
617 JavaThread* jthr = JavaThread::current();
618 if (!jthr->in_critical()) {
619 MutexUnlocker mul(Heap_lock);
620 // Wait for JNI critical section to be exited
621 GC_locker::stall_until_clear();
622 gclocker_stalled_count += 1;
623 continue;
624 } else {
625 if (CheckJNICalls) {
626 fatal("Possible deadlock due to allocating while"
627 " in jni critical section");
628 }
629 return NULL;
630 }
631 }
632
633 // Read the gc count while the heap lock is held.
634 gc_count_before = Universe::heap()->total_collections();
635 }
636
637 VM_GenCollectForAllocation op(size, is_tlab, gc_count_before);
638 VMThread::execute(&op);
639 if (op.prologue_succeeded()) {
640 result = op.result();
641 if (op.gc_locked()) {
642 assert(result == NULL, "must be NULL if gc_locked() is true");
643 continue; // retry and/or stall as necessary
644 }
645
646 // Allocation has failed and a collection
647 // has been done. If the gc time limit was exceeded the
648 // this time, return NULL so that an out-of-memory
649 // will be thrown. Clear gc_overhead_limit_exceeded
650 // so that the overhead exceeded does not persist.
651
652 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
653 const bool softrefs_clear = all_soft_refs_clear();
654
655 if (limit_exceeded && softrefs_clear) {
656 *gc_overhead_limit_was_exceeded = true;
657 size_policy()->set_gc_overhead_limit_exceeded(false);
852 bool GenCollectorPolicy::should_try_older_generation_allocation(
853 size_t word_size) const {
854 GenCollectedHeap* gch = GenCollectedHeap::heap();
855 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();
856 return (word_size > heap_word_size(gen0_capacity))
857 || GC_locker::is_active_and_needs_gc()
858 || gch->incremental_collection_failed();
859 }
860
861
862 //
863 // MarkSweepPolicy methods
864 //
865
866 MarkSweepPolicy::MarkSweepPolicy() {
867 initialize_all();
868 }
869
870 void MarkSweepPolicy::initialize_generations() {
871 _generations = NEW_C_HEAP_ARRAY3(GenerationSpecPtr, number_of_generations(), mtGC, 0, AllocFailStrategy::RETURN_NULL);
872 if (_generations == NULL) {
873 vm_exit_during_initialization("Unable to allocate gen spec");
874 }
875
876 if (UseParNewGC) {
877 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);
878 } else {
879 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);
880 }
881 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);
882
883 if (_generations[0] == NULL || _generations[1] == NULL) {
884 vm_exit_during_initialization("Unable to allocate gen spec");
885 }
886 }
887
888 void MarkSweepPolicy::initialize_gc_policy_counters() {
889 // initialize the policy counters - 2 collectors, 3 generations
890 if (UseParNewGC) {
891 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);
892 } else {
893 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
894 }
895 }
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