Thu, 03 Oct 2013 13:19:19 +0200
8025855: Simplify GenRemSet code slightly
Summary: Remove a few redundant switch-statements
Reviewed-by: jcoomes, tschatzl
1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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23 */
25 #include "precompiled.hpp"
26 #include "gc_implementation/shared/adaptiveSizePolicy.hpp"
27 #include "gc_implementation/shared/gcPolicyCounters.hpp"
28 #include "gc_implementation/shared/vmGCOperations.hpp"
29 #include "memory/cardTableRS.hpp"
30 #include "memory/collectorPolicy.hpp"
31 #include "memory/gcLocker.inline.hpp"
32 #include "memory/genCollectedHeap.hpp"
33 #include "memory/generationSpec.hpp"
34 #include "memory/space.hpp"
35 #include "memory/universe.hpp"
36 #include "runtime/arguments.hpp"
37 #include "runtime/globals_extension.hpp"
38 #include "runtime/handles.inline.hpp"
39 #include "runtime/java.hpp"
40 #include "runtime/thread.inline.hpp"
41 #include "runtime/vmThread.hpp"
42 #include "utilities/macros.hpp"
43 #if INCLUDE_ALL_GCS
44 #include "gc_implementation/concurrentMarkSweep/cmsAdaptiveSizePolicy.hpp"
45 #include "gc_implementation/concurrentMarkSweep/cmsGCAdaptivePolicyCounters.hpp"
46 #endif // INCLUDE_ALL_GCS
48 // CollectorPolicy methods.
50 // 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 }
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()));
63 if (MaxHeapSize < InitialHeapSize) {
64 vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
65 }
67 // Do not use FLAG_SET_ERGO to update MaxMetaspaceSize, since this will
68 // override if MaxMetaspaceSize was set on the command line or not.
69 // This information is needed later to conform to the specification of the
70 // java.lang.management.MemoryUsage API.
71 //
72 // Ideally, we would be able to set the default value of MaxMetaspaceSize in
73 // globals.hpp to the aligned value, but this is not possible, since the
74 // alignment depends on other flags being parsed.
75 MaxMetaspaceSize = restricted_align_down(MaxMetaspaceSize, max_alignment());
77 if (MetaspaceSize > MaxMetaspaceSize) {
78 MetaspaceSize = MaxMetaspaceSize;
79 }
81 MetaspaceSize = restricted_align_down(MetaspaceSize, min_alignment());
83 assert(MetaspaceSize <= MaxMetaspaceSize, "Must be");
85 MinMetaspaceExpansion = restricted_align_down(MinMetaspaceExpansion, min_alignment());
86 MaxMetaspaceExpansion = restricted_align_down(MaxMetaspaceExpansion, min_alignment());
88 MinHeapDeltaBytes = align_size_up(MinHeapDeltaBytes, min_alignment());
90 assert(MetaspaceSize % min_alignment() == 0, "metapace alignment");
91 assert(MaxMetaspaceSize % max_alignment() == 0, "maximum metaspace alignment");
92 if (MetaspaceSize < 256*K) {
93 vm_exit_during_initialization("Too small initial Metaspace size");
94 }
95 }
97 void CollectorPolicy::initialize_size_info() {
98 // User inputs from -mx and ms must be aligned
99 set_min_heap_byte_size(align_size_up(Arguments::min_heap_size(), min_alignment()));
100 set_initial_heap_byte_size(align_size_up(InitialHeapSize, min_alignment()));
101 set_max_heap_byte_size(align_size_up(MaxHeapSize, max_alignment()));
103 // Check heap parameter properties
104 if (initial_heap_byte_size() < M) {
105 vm_exit_during_initialization("Too small initial heap");
106 }
107 // Check heap parameter properties
108 if (min_heap_byte_size() < M) {
109 vm_exit_during_initialization("Too small minimum heap");
110 }
111 if (initial_heap_byte_size() <= NewSize) {
112 // make sure there is at least some room in old space
113 vm_exit_during_initialization("Too small initial heap for new size specified");
114 }
115 if (max_heap_byte_size() < min_heap_byte_size()) {
116 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified");
117 }
118 if (initial_heap_byte_size() < min_heap_byte_size()) {
119 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified");
120 }
121 if (max_heap_byte_size() < initial_heap_byte_size()) {
122 vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
123 }
125 if (PrintGCDetails && Verbose) {
126 gclog_or_tty->print_cr("Minimum heap " SIZE_FORMAT " Initial heap "
127 SIZE_FORMAT " Maximum heap " SIZE_FORMAT,
128 min_heap_byte_size(), initial_heap_byte_size(), max_heap_byte_size());
129 }
130 }
132 bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) {
133 bool result = _should_clear_all_soft_refs;
134 set_should_clear_all_soft_refs(false);
135 return result;
136 }
138 GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap,
139 int max_covered_regions) {
140 assert(rem_set_name() == GenRemSet::CardTable, "unrecognized GenRemSet::Name");
141 return new CardTableRS(whole_heap, max_covered_regions);
142 }
144 void CollectorPolicy::cleared_all_soft_refs() {
145 // If near gc overhear limit, continue to clear SoftRefs. SoftRefs may
146 // have been cleared in the last collection but if the gc overhear
147 // limit continues to be near, SoftRefs should still be cleared.
148 if (size_policy() != NULL) {
149 _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near();
150 }
151 _all_soft_refs_clear = true;
152 }
154 size_t CollectorPolicy::compute_max_alignment() {
155 // The card marking array and the offset arrays for old generations are
156 // committed in os pages as well. Make sure they are entirely full (to
157 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
158 // byte entry and the os page size is 4096, the maximum heap size should
159 // be 512*4096 = 2MB aligned.
161 // There is only the GenRemSet in Hotspot and only the GenRemSet::CardTable
162 // is supported.
163 // Requirements of any new remembered set implementations must be added here.
164 size_t alignment = GenRemSet::max_alignment_constraint(GenRemSet::CardTable);
166 // Parallel GC does its own alignment of the generations to avoid requiring a
167 // large page (256M on some platforms) for the permanent generation. The
168 // other collectors should also be updated to do their own alignment and then
169 // this use of lcm() should be removed.
170 if (UseLargePages && !UseParallelGC) {
171 // in presence of large pages we have to make sure that our
172 // alignment is large page aware
173 alignment = lcm(os::large_page_size(), alignment);
174 }
176 return alignment;
177 }
179 // GenCollectorPolicy methods.
181 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {
182 size_t x = base_size / (NewRatio+1);
183 size_t new_gen_size = x > min_alignment() ?
184 align_size_down(x, min_alignment()) :
185 min_alignment();
186 return new_gen_size;
187 }
189 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,
190 size_t maximum_size) {
191 size_t alignment = min_alignment();
192 size_t max_minus = maximum_size - alignment;
193 return desired_size < max_minus ? desired_size : max_minus;
194 }
197 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size,
198 size_t init_promo_size,
199 size_t init_survivor_size) {
200 const double max_gc_pause_sec = ((double) MaxGCPauseMillis)/1000.0;
201 _size_policy = new AdaptiveSizePolicy(init_eden_size,
202 init_promo_size,
203 init_survivor_size,
204 max_gc_pause_sec,
205 GCTimeRatio);
206 }
208 void GenCollectorPolicy::initialize_flags() {
209 // All sizes must be multiples of the generation granularity.
210 set_min_alignment((uintx) Generation::GenGrain);
211 set_max_alignment(compute_max_alignment());
213 CollectorPolicy::initialize_flags();
215 // All generational heaps have a youngest gen; handle those flags here.
217 // Adjust max size parameters
218 if (NewSize > MaxNewSize) {
219 MaxNewSize = NewSize;
220 }
221 NewSize = align_size_down(NewSize, min_alignment());
222 MaxNewSize = align_size_down(MaxNewSize, min_alignment());
224 // Check validity of heap flags
225 assert(NewSize % min_alignment() == 0, "eden space alignment");
226 assert(MaxNewSize % min_alignment() == 0, "survivor space alignment");
228 if (NewSize < 3*min_alignment()) {
229 // make sure there room for eden and two survivor spaces
230 vm_exit_during_initialization("Too small new size specified");
231 }
232 if (SurvivorRatio < 1 || NewRatio < 1) {
233 vm_exit_during_initialization("Invalid heap ratio specified");
234 }
235 }
237 void TwoGenerationCollectorPolicy::initialize_flags() {
238 GenCollectorPolicy::initialize_flags();
240 OldSize = align_size_down(OldSize, min_alignment());
242 if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(NewSize)) {
243 // NewRatio will be used later to set the young generation size so we use
244 // it to calculate how big the heap should be based on the requested OldSize
245 // and NewRatio.
246 assert(NewRatio > 0, "NewRatio should have been set up earlier");
247 size_t calculated_heapsize = (OldSize / NewRatio) * (NewRatio + 1);
249 calculated_heapsize = align_size_up(calculated_heapsize, max_alignment());
250 MaxHeapSize = calculated_heapsize;
251 InitialHeapSize = calculated_heapsize;
252 }
253 MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
255 // adjust max heap size if necessary
256 if (NewSize + OldSize > MaxHeapSize) {
257 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
258 // somebody set a maximum heap size with the intention that we should not
259 // exceed it. Adjust New/OldSize as necessary.
260 uintx calculated_size = NewSize + OldSize;
261 double shrink_factor = (double) MaxHeapSize / calculated_size;
262 // align
263 NewSize = align_size_down((uintx) (NewSize * shrink_factor), min_alignment());
264 // OldSize is already aligned because above we aligned MaxHeapSize to
265 // max_alignment(), and we just made sure that NewSize is aligned to
266 // min_alignment(). In initialize_flags() we verified that max_alignment()
267 // is a multiple of min_alignment().
268 OldSize = MaxHeapSize - NewSize;
269 } else {
270 MaxHeapSize = NewSize + OldSize;
271 }
272 }
273 // need to do this again
274 MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
276 // adjust max heap size if necessary
277 if (NewSize + OldSize > MaxHeapSize) {
278 if (FLAG_IS_CMDLINE(MaxHeapSize)) {
279 // somebody set a maximum heap size with the intention that we should not
280 // exceed it. Adjust New/OldSize as necessary.
281 uintx calculated_size = NewSize + OldSize;
282 double shrink_factor = (double) MaxHeapSize / calculated_size;
283 // align
284 NewSize = align_size_down((uintx) (NewSize * shrink_factor), min_alignment());
285 // OldSize is already aligned because above we aligned MaxHeapSize to
286 // max_alignment(), and we just made sure that NewSize is aligned to
287 // min_alignment(). In initialize_flags() we verified that max_alignment()
288 // is a multiple of min_alignment().
289 OldSize = MaxHeapSize - NewSize;
290 } else {
291 MaxHeapSize = NewSize + OldSize;
292 }
293 }
294 // need to do this again
295 MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
297 always_do_update_barrier = UseConcMarkSweepGC;
299 // Check validity of heap flags
300 assert(OldSize % min_alignment() == 0, "old space alignment");
301 assert(MaxHeapSize % max_alignment() == 0, "maximum heap alignment");
302 }
304 // Values set on the command line win over any ergonomically
305 // set command line parameters.
306 // Ergonomic choice of parameters are done before this
307 // method is called. Values for command line parameters such as NewSize
308 // and MaxNewSize feed those ergonomic choices into this method.
309 // This method makes the final generation sizings consistent with
310 // themselves and with overall heap sizings.
311 // In the absence of explicitly set command line flags, policies
312 // such as the use of NewRatio are used to size the generation.
313 void GenCollectorPolicy::initialize_size_info() {
314 CollectorPolicy::initialize_size_info();
316 // min_alignment() is used for alignment within a generation.
317 // There is additional alignment done down stream for some
318 // collectors that sometimes causes unwanted rounding up of
319 // generations sizes.
321 // Determine maximum size of gen0
323 size_t max_new_size = 0;
324 if (FLAG_IS_CMDLINE(MaxNewSize) || FLAG_IS_ERGO(MaxNewSize)) {
325 if (MaxNewSize < min_alignment()) {
326 max_new_size = min_alignment();
327 }
328 if (MaxNewSize >= max_heap_byte_size()) {
329 max_new_size = align_size_down(max_heap_byte_size() - min_alignment(),
330 min_alignment());
331 warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or "
332 "greater than the entire heap (" SIZE_FORMAT "k). A "
333 "new generation size of " SIZE_FORMAT "k will be used.",
334 MaxNewSize/K, max_heap_byte_size()/K, max_new_size/K);
335 } else {
336 max_new_size = align_size_down(MaxNewSize, min_alignment());
337 }
339 // The case for FLAG_IS_ERGO(MaxNewSize) could be treated
340 // specially at this point to just use an ergonomically set
341 // MaxNewSize to set max_new_size. For cases with small
342 // heaps such a policy often did not work because the MaxNewSize
343 // was larger than the entire heap. The interpretation given
344 // to ergonomically set flags is that the flags are set
345 // by different collectors for their own special needs but
346 // are not allowed to badly shape the heap. This allows the
347 // different collectors to decide what's best for themselves
348 // without having to factor in the overall heap shape. It
349 // can be the case in the future that the collectors would
350 // only make "wise" ergonomics choices and this policy could
351 // just accept those choices. The choices currently made are
352 // not always "wise".
353 } else {
354 max_new_size = scale_by_NewRatio_aligned(max_heap_byte_size());
355 // Bound the maximum size by NewSize below (since it historically
356 // would have been NewSize and because the NewRatio calculation could
357 // yield a size that is too small) and bound it by MaxNewSize above.
358 // Ergonomics plays here by previously calculating the desired
359 // NewSize and MaxNewSize.
360 max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize);
361 }
362 assert(max_new_size > 0, "All paths should set max_new_size");
364 // Given the maximum gen0 size, determine the initial and
365 // minimum gen0 sizes.
367 if (max_heap_byte_size() == min_heap_byte_size()) {
368 // The maximum and minimum heap sizes are the same so
369 // the generations minimum and initial must be the
370 // same as its maximum.
371 set_min_gen0_size(max_new_size);
372 set_initial_gen0_size(max_new_size);
373 set_max_gen0_size(max_new_size);
374 } else {
375 size_t desired_new_size = 0;
376 if (!FLAG_IS_DEFAULT(NewSize)) {
377 // If NewSize is set ergonomically (for example by cms), it
378 // would make sense to use it. If it is used, also use it
379 // to set the initial size. Although there is no reason
380 // the minimum size and the initial size have to be the same,
381 // the current implementation gets into trouble during the calculation
382 // of the tenured generation sizes if they are different.
383 // Note that this makes the initial size and the minimum size
384 // generally small compared to the NewRatio calculation.
385 _min_gen0_size = NewSize;
386 desired_new_size = NewSize;
387 max_new_size = MAX2(max_new_size, NewSize);
388 } else {
389 // For the case where NewSize is the default, use NewRatio
390 // to size the minimum and initial generation sizes.
391 // Use the default NewSize as the floor for these values. If
392 // NewRatio is overly large, the resulting sizes can be too
393 // small.
394 _min_gen0_size = MAX2(scale_by_NewRatio_aligned(min_heap_byte_size()),
395 NewSize);
396 desired_new_size =
397 MAX2(scale_by_NewRatio_aligned(initial_heap_byte_size()),
398 NewSize);
399 }
401 assert(_min_gen0_size > 0, "Sanity check");
402 set_initial_gen0_size(desired_new_size);
403 set_max_gen0_size(max_new_size);
405 // At this point the desirable initial and minimum sizes have been
406 // determined without regard to the maximum sizes.
408 // Bound the sizes by the corresponding overall heap sizes.
409 set_min_gen0_size(
410 bound_minus_alignment(_min_gen0_size, min_heap_byte_size()));
411 set_initial_gen0_size(
412 bound_minus_alignment(_initial_gen0_size, initial_heap_byte_size()));
413 set_max_gen0_size(
414 bound_minus_alignment(_max_gen0_size, max_heap_byte_size()));
416 // At this point all three sizes have been checked against the
417 // maximum sizes but have not been checked for consistency
418 // among the three.
420 // Final check min <= initial <= max
421 set_min_gen0_size(MIN2(_min_gen0_size, _max_gen0_size));
422 set_initial_gen0_size(
423 MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size));
424 set_min_gen0_size(MIN2(_min_gen0_size, _initial_gen0_size));
425 }
427 if (PrintGCDetails && Verbose) {
428 gclog_or_tty->print_cr("1: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
429 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
430 min_gen0_size(), initial_gen0_size(), max_gen0_size());
431 }
432 }
434 // Call this method during the sizing of the gen1 to make
435 // adjustments to gen0 because of gen1 sizing policy. gen0 initially has
436 // the most freedom in sizing because it is done before the
437 // policy for gen1 is applied. Once gen1 policies have been applied,
438 // there may be conflicts in the shape of the heap and this method
439 // is used to make the needed adjustments. The application of the
440 // policies could be more sophisticated (iterative for example) but
441 // keeping it simple also seems a worthwhile goal.
442 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr,
443 size_t* gen1_size_ptr,
444 const size_t heap_size,
445 const size_t min_gen1_size) {
446 bool result = false;
448 if ((*gen1_size_ptr + *gen0_size_ptr) > heap_size) {
449 if ((heap_size < (*gen0_size_ptr + min_gen1_size)) &&
450 (heap_size >= min_gen1_size + min_alignment())) {
451 // Adjust gen0 down to accommodate min_gen1_size
452 *gen0_size_ptr = heap_size - min_gen1_size;
453 *gen0_size_ptr =
454 MAX2((uintx)align_size_down(*gen0_size_ptr, min_alignment()),
455 min_alignment());
456 assert(*gen0_size_ptr > 0, "Min gen0 is too large");
457 result = true;
458 } else {
459 *gen1_size_ptr = heap_size - *gen0_size_ptr;
460 *gen1_size_ptr =
461 MAX2((uintx)align_size_down(*gen1_size_ptr, min_alignment()),
462 min_alignment());
463 }
464 }
465 return result;
466 }
468 // Minimum sizes of the generations may be different than
469 // the initial sizes. An inconsistently is permitted here
470 // in the total size that can be specified explicitly by
471 // command line specification of OldSize and NewSize and
472 // also a command line specification of -Xms. Issue a warning
473 // but allow the values to pass.
475 void TwoGenerationCollectorPolicy::initialize_size_info() {
476 GenCollectorPolicy::initialize_size_info();
478 // At this point the minimum, initial and maximum sizes
479 // of the overall heap and of gen0 have been determined.
480 // The maximum gen1 size can be determined from the maximum gen0
481 // and maximum heap size since no explicit flags exits
482 // for setting the gen1 maximum.
483 _max_gen1_size = max_heap_byte_size() - _max_gen0_size;
484 _max_gen1_size =
485 MAX2((uintx)align_size_down(_max_gen1_size, min_alignment()),
486 min_alignment());
487 // If no explicit command line flag has been set for the
488 // gen1 size, use what is left for gen1.
489 if (FLAG_IS_DEFAULT(OldSize) || FLAG_IS_ERGO(OldSize)) {
490 // The user has not specified any value or ergonomics
491 // has chosen a value (which may or may not be consistent
492 // with the overall heap size). In either case make
493 // the minimum, maximum and initial sizes consistent
494 // with the gen0 sizes and the overall heap sizes.
495 assert(min_heap_byte_size() > _min_gen0_size,
496 "gen0 has an unexpected minimum size");
497 set_min_gen1_size(min_heap_byte_size() - min_gen0_size());
498 set_min_gen1_size(
499 MAX2((uintx)align_size_down(_min_gen1_size, min_alignment()),
500 min_alignment()));
501 set_initial_gen1_size(initial_heap_byte_size() - initial_gen0_size());
502 set_initial_gen1_size(
503 MAX2((uintx)align_size_down(_initial_gen1_size, min_alignment()),
504 min_alignment()));
506 } else {
507 // It's been explicitly set on the command line. Use the
508 // OldSize and then determine the consequences.
509 set_min_gen1_size(OldSize);
510 set_initial_gen1_size(OldSize);
512 // If the user has explicitly set an OldSize that is inconsistent
513 // with other command line flags, issue a warning.
514 // The generation minimums and the overall heap mimimum should
515 // be within one heap alignment.
516 if ((_min_gen1_size + _min_gen0_size + min_alignment()) <
517 min_heap_byte_size()) {
518 warning("Inconsistency between minimum heap size and minimum "
519 "generation sizes: using minimum heap = " SIZE_FORMAT,
520 min_heap_byte_size());
521 }
522 if ((OldSize > _max_gen1_size)) {
523 warning("Inconsistency between maximum heap size and maximum "
524 "generation sizes: using maximum heap = " SIZE_FORMAT
525 " -XX:OldSize flag is being ignored",
526 max_heap_byte_size());
527 }
528 // If there is an inconsistency between the OldSize and the minimum and/or
529 // initial size of gen0, since OldSize was explicitly set, OldSize wins.
530 if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size,
531 min_heap_byte_size(), OldSize)) {
532 if (PrintGCDetails && Verbose) {
533 gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
534 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
535 min_gen0_size(), initial_gen0_size(), max_gen0_size());
536 }
537 }
538 // Initial size
539 if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,
540 initial_heap_byte_size(), OldSize)) {
541 if (PrintGCDetails && Verbose) {
542 gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
543 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
544 min_gen0_size(), initial_gen0_size(), max_gen0_size());
545 }
546 }
547 }
548 // Enforce the maximum gen1 size.
549 set_min_gen1_size(MIN2(_min_gen1_size, _max_gen1_size));
551 // Check that min gen1 <= initial gen1 <= max gen1
552 set_initial_gen1_size(MAX2(_initial_gen1_size, _min_gen1_size));
553 set_initial_gen1_size(MIN2(_initial_gen1_size, _max_gen1_size));
555 if (PrintGCDetails && Verbose) {
556 gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 "
557 SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT,
558 min_gen1_size(), initial_gen1_size(), max_gen1_size());
559 }
560 }
562 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
563 bool is_tlab,
564 bool* gc_overhead_limit_was_exceeded) {
565 GenCollectedHeap *gch = GenCollectedHeap::heap();
567 debug_only(gch->check_for_valid_allocation_state());
568 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
570 // In general gc_overhead_limit_was_exceeded should be false so
571 // set it so here and reset it to true only if the gc time
572 // limit is being exceeded as checked below.
573 *gc_overhead_limit_was_exceeded = false;
575 HeapWord* result = NULL;
577 // Loop until the allocation is satisified,
578 // or unsatisfied after GC.
579 for (int try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) {
580 HandleMark hm; // discard any handles allocated in each iteration
582 // First allocation attempt is lock-free.
583 Generation *gen0 = gch->get_gen(0);
584 assert(gen0->supports_inline_contig_alloc(),
585 "Otherwise, must do alloc within heap lock");
586 if (gen0->should_allocate(size, is_tlab)) {
587 result = gen0->par_allocate(size, is_tlab);
588 if (result != NULL) {
589 assert(gch->is_in_reserved(result), "result not in heap");
590 return result;
591 }
592 }
593 unsigned int gc_count_before; // read inside the Heap_lock locked region
594 {
595 MutexLocker ml(Heap_lock);
596 if (PrintGC && Verbose) {
597 gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:"
598 " attempting locked slow path allocation");
599 }
600 // Note that only large objects get a shot at being
601 // allocated in later generations.
602 bool first_only = ! should_try_older_generation_allocation(size);
604 result = gch->attempt_allocation(size, is_tlab, first_only);
605 if (result != NULL) {
606 assert(gch->is_in_reserved(result), "result not in heap");
607 return result;
608 }
610 if (GC_locker::is_active_and_needs_gc()) {
611 if (is_tlab) {
612 return NULL; // Caller will retry allocating individual object
613 }
614 if (!gch->is_maximal_no_gc()) {
615 // Try and expand heap to satisfy request
616 result = expand_heap_and_allocate(size, is_tlab);
617 // result could be null if we are out of space
618 if (result != NULL) {
619 return result;
620 }
621 }
623 if (gclocker_stalled_count > GCLockerRetryAllocationCount) {
624 return NULL; // we didn't get to do a GC and we didn't get any memory
625 }
627 // If this thread is not in a jni critical section, we stall
628 // the requestor until the critical section has cleared and
629 // GC allowed. When the critical section clears, a GC is
630 // initiated by the last thread exiting the critical section; so
631 // we retry the allocation sequence from the beginning of the loop,
632 // rather than causing more, now probably unnecessary, GC attempts.
633 JavaThread* jthr = JavaThread::current();
634 if (!jthr->in_critical()) {
635 MutexUnlocker mul(Heap_lock);
636 // Wait for JNI critical section to be exited
637 GC_locker::stall_until_clear();
638 gclocker_stalled_count += 1;
639 continue;
640 } else {
641 if (CheckJNICalls) {
642 fatal("Possible deadlock due to allocating while"
643 " in jni critical section");
644 }
645 return NULL;
646 }
647 }
649 // Read the gc count while the heap lock is held.
650 gc_count_before = Universe::heap()->total_collections();
651 }
653 VM_GenCollectForAllocation op(size,
654 is_tlab,
655 gc_count_before);
656 VMThread::execute(&op);
657 if (op.prologue_succeeded()) {
658 result = op.result();
659 if (op.gc_locked()) {
660 assert(result == NULL, "must be NULL if gc_locked() is true");
661 continue; // retry and/or stall as necessary
662 }
664 // Allocation has failed and a collection
665 // has been done. If the gc time limit was exceeded the
666 // this time, return NULL so that an out-of-memory
667 // will be thrown. Clear gc_overhead_limit_exceeded
668 // so that the overhead exceeded does not persist.
670 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
671 const bool softrefs_clear = all_soft_refs_clear();
673 if (limit_exceeded && softrefs_clear) {
674 *gc_overhead_limit_was_exceeded = true;
675 size_policy()->set_gc_overhead_limit_exceeded(false);
676 if (op.result() != NULL) {
677 CollectedHeap::fill_with_object(op.result(), size);
678 }
679 return NULL;
680 }
681 assert(result == NULL || gch->is_in_reserved(result),
682 "result not in heap");
683 return result;
684 }
686 // Give a warning if we seem to be looping forever.
687 if ((QueuedAllocationWarningCount > 0) &&
688 (try_count % QueuedAllocationWarningCount == 0)) {
689 warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t"
690 " size=%d %s", try_count, size, is_tlab ? "(TLAB)" : "");
691 }
692 }
693 }
695 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size,
696 bool is_tlab) {
697 GenCollectedHeap *gch = GenCollectedHeap::heap();
698 HeapWord* result = NULL;
699 for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) {
700 Generation *gen = gch->get_gen(i);
701 if (gen->should_allocate(size, is_tlab)) {
702 result = gen->expand_and_allocate(size, is_tlab);
703 }
704 }
705 assert(result == NULL || gch->is_in_reserved(result), "result not in heap");
706 return result;
707 }
709 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size,
710 bool is_tlab) {
711 GenCollectedHeap *gch = GenCollectedHeap::heap();
712 GCCauseSetter x(gch, GCCause::_allocation_failure);
713 HeapWord* result = NULL;
715 assert(size != 0, "Precondition violated");
716 if (GC_locker::is_active_and_needs_gc()) {
717 // GC locker is active; instead of a collection we will attempt
718 // to expand the heap, if there's room for expansion.
719 if (!gch->is_maximal_no_gc()) {
720 result = expand_heap_and_allocate(size, is_tlab);
721 }
722 return result; // could be null if we are out of space
723 } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) {
724 // Do an incremental collection.
725 gch->do_collection(false /* full */,
726 false /* clear_all_soft_refs */,
727 size /* size */,
728 is_tlab /* is_tlab */,
729 number_of_generations() - 1 /* max_level */);
730 } else {
731 if (Verbose && PrintGCDetails) {
732 gclog_or_tty->print(" :: Trying full because partial may fail :: ");
733 }
734 // Try a full collection; see delta for bug id 6266275
735 // for the original code and why this has been simplified
736 // with from-space allocation criteria modified and
737 // such allocation moved out of the safepoint path.
738 gch->do_collection(true /* full */,
739 false /* clear_all_soft_refs */,
740 size /* size */,
741 is_tlab /* is_tlab */,
742 number_of_generations() - 1 /* max_level */);
743 }
745 result = gch->attempt_allocation(size, is_tlab, false /*first_only*/);
747 if (result != NULL) {
748 assert(gch->is_in_reserved(result), "result not in heap");
749 return result;
750 }
752 // OK, collection failed, try expansion.
753 result = expand_heap_and_allocate(size, is_tlab);
754 if (result != NULL) {
755 return result;
756 }
758 // If we reach this point, we're really out of memory. Try every trick
759 // we can to reclaim memory. Force collection of soft references. Force
760 // a complete compaction of the heap. Any additional methods for finding
761 // free memory should be here, especially if they are expensive. If this
762 // attempt fails, an OOM exception will be thrown.
763 {
764 UIntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
766 gch->do_collection(true /* full */,
767 true /* clear_all_soft_refs */,
768 size /* size */,
769 is_tlab /* is_tlab */,
770 number_of_generations() - 1 /* max_level */);
771 }
773 result = gch->attempt_allocation(size, is_tlab, false /* first_only */);
774 if (result != NULL) {
775 assert(gch->is_in_reserved(result), "result not in heap");
776 return result;
777 }
779 assert(!should_clear_all_soft_refs(),
780 "Flag should have been handled and cleared prior to this point");
782 // What else? We might try synchronous finalization later. If the total
783 // space available is large enough for the allocation, then a more
784 // complete compaction phase than we've tried so far might be
785 // appropriate.
786 return NULL;
787 }
789 MetaWord* CollectorPolicy::satisfy_failed_metadata_allocation(
790 ClassLoaderData* loader_data,
791 size_t word_size,
792 Metaspace::MetadataType mdtype) {
793 uint loop_count = 0;
794 uint gc_count = 0;
795 uint full_gc_count = 0;
797 assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock");
799 do {
800 MetaWord* result = NULL;
801 if (GC_locker::is_active_and_needs_gc()) {
802 // If the GC_locker is active, just expand and allocate.
803 // If that does not succeed, wait if this thread is not
804 // in a critical section itself.
805 result =
806 loader_data->metaspace_non_null()->expand_and_allocate(word_size,
807 mdtype);
808 if (result != NULL) {
809 return result;
810 }
811 JavaThread* jthr = JavaThread::current();
812 if (!jthr->in_critical()) {
813 // Wait for JNI critical section to be exited
814 GC_locker::stall_until_clear();
815 // The GC invoked by the last thread leaving the critical
816 // section will be a young collection and a full collection
817 // is (currently) needed for unloading classes so continue
818 // to the next iteration to get a full GC.
819 continue;
820 } else {
821 if (CheckJNICalls) {
822 fatal("Possible deadlock due to allocating while"
823 " in jni critical section");
824 }
825 return NULL;
826 }
827 }
829 { // Need lock to get self consistent gc_count's
830 MutexLocker ml(Heap_lock);
831 gc_count = Universe::heap()->total_collections();
832 full_gc_count = Universe::heap()->total_full_collections();
833 }
835 // Generate a VM operation
836 VM_CollectForMetadataAllocation op(loader_data,
837 word_size,
838 mdtype,
839 gc_count,
840 full_gc_count,
841 GCCause::_metadata_GC_threshold);
842 VMThread::execute(&op);
844 // If GC was locked out, try again. Check
845 // before checking success because the prologue
846 // could have succeeded and the GC still have
847 // been locked out.
848 if (op.gc_locked()) {
849 continue;
850 }
852 if (op.prologue_succeeded()) {
853 return op.result();
854 }
855 loop_count++;
856 if ((QueuedAllocationWarningCount > 0) &&
857 (loop_count % QueuedAllocationWarningCount == 0)) {
858 warning("satisfy_failed_metadata_allocation() retries %d times \n\t"
859 " size=%d", loop_count, word_size);
860 }
861 } while (true); // Until a GC is done
862 }
864 // Return true if any of the following is true:
865 // . the allocation won't fit into the current young gen heap
866 // . gc locker is occupied (jni critical section)
867 // . heap memory is tight -- the most recent previous collection
868 // was a full collection because a partial collection (would
869 // have) failed and is likely to fail again
870 bool GenCollectorPolicy::should_try_older_generation_allocation(
871 size_t word_size) const {
872 GenCollectedHeap* gch = GenCollectedHeap::heap();
873 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();
874 return (word_size > heap_word_size(gen0_capacity))
875 || GC_locker::is_active_and_needs_gc()
876 || gch->incremental_collection_failed();
877 }
880 //
881 // MarkSweepPolicy methods
882 //
884 MarkSweepPolicy::MarkSweepPolicy() {
885 initialize_all();
886 }
888 void MarkSweepPolicy::initialize_generations() {
889 _generations = NEW_C_HEAP_ARRAY3(GenerationSpecPtr, number_of_generations(), mtGC, 0, AllocFailStrategy::RETURN_NULL);
890 if (_generations == NULL)
891 vm_exit_during_initialization("Unable to allocate gen spec");
893 if (UseParNewGC) {
894 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);
895 } else {
896 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);
897 }
898 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);
900 if (_generations[0] == NULL || _generations[1] == NULL)
901 vm_exit_during_initialization("Unable to allocate gen spec");
902 }
904 void MarkSweepPolicy::initialize_gc_policy_counters() {
905 // initialize the policy counters - 2 collectors, 3 generations
906 if (UseParNewGC) {
907 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);
908 } else {
909 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
910 }
911 }