1 /*
2 * Copyright (c) 1997, 2014, 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_implementation/shared/gcTimer.hpp"
27 #include "gc_implementation/shared/gcTrace.hpp"
28 #include "gc_implementation/shared/spaceDecorator.hpp"
29 #include "gc_interface/collectedHeap.inline.hpp"
30 #include "memory/allocation.inline.hpp"
31 #include "memory/blockOffsetTable.inline.hpp"
32 #include "memory/cardTableRS.hpp"
33 #include "memory/gcLocker.inline.hpp"
34 #include "memory/genCollectedHeap.hpp"
35 #include "memory/genMarkSweep.hpp"
36 #include "memory/genOopClosures.hpp"
37 #include "memory/genOopClosures.inline.hpp"
38 #include "memory/generation.hpp"
39 #include "memory/space.inline.hpp"
40 #include "oops/oop.inline.hpp"
41 #include "runtime/java.hpp"
42 #include "utilities/copy.hpp"
43 #include "utilities/events.hpp"
44
45 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
46
47 Generation::Generation(ReservedSpace rs, size_t initial_size, int level) :
48 _level(level),
49 _ref_processor(NULL) {
50 if (!_virtual_space.initialize(rs, initial_size)) {
51 vm_exit_during_initialization("Could not reserve enough space for "
52 "object heap");
53 }
54 // Mangle all of the the initial generation.
55 if (ZapUnusedHeapArea) {
56 MemRegion mangle_region((HeapWord*)_virtual_space.low(),
57 (HeapWord*)_virtual_space.high());
58 SpaceMangler::mangle_region(mangle_region);
59 }
60 _reserved = MemRegion((HeapWord*)_virtual_space.low_boundary(),
61 (HeapWord*)_virtual_space.high_boundary());
62 }
63
64 GenerationSpec* Generation::spec() {
65 GenCollectedHeap* gch = GenCollectedHeap::heap();
66 assert(0 <= level() && level() < gch->_n_gens, "Bad gen level");
67 return gch->_gen_specs[level()];
68 }
69
70 size_t Generation::max_capacity() const {
71 return reserved().byte_size();
72 }
73
74 void Generation::print_heap_change(size_t prev_used) const {
75 if (PrintGCDetails && Verbose) {
76 gclog_or_tty->print(" " SIZE_FORMAT
77 "->" SIZE_FORMAT
78 "(" SIZE_FORMAT ")",
79 prev_used, used(), capacity());
80 } else {
81 gclog_or_tty->print(" " SIZE_FORMAT "K"
82 "->" SIZE_FORMAT "K"
83 "(" SIZE_FORMAT "K)",
84 prev_used / K, used() / K, capacity() / K);
85 }
86 }
87
88 // By default we get a single threaded default reference processor;
89 // generations needing multi-threaded refs processing or discovery override this method.
90 void Generation::ref_processor_init() {
91 assert(_ref_processor == NULL, "a reference processor already exists");
92 assert(!_reserved.is_empty(), "empty generation?");
93 _ref_processor = new ReferenceProcessor(_reserved); // a vanilla reference processor
94 if (_ref_processor == NULL) {
95 vm_exit_during_initialization("Could not allocate ReferenceProcessor object");
96 }
97 }
98
99 void Generation::print() const { print_on(tty); }
100
101 void Generation::print_on(outputStream* st) const {
102 st->print(" %-20s", name());
103 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
104 capacity()/K, used()/K);
105 st->print_cr(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
106 _virtual_space.low_boundary(),
107 _virtual_space.high(),
108 _virtual_space.high_boundary());
109 }
110
111 void Generation::print_summary_info() { print_summary_info_on(tty); }
112
113 void Generation::print_summary_info_on(outputStream* st) {
114 StatRecord* sr = stat_record();
115 double time = sr->accumulated_time.seconds();
116 st->print_cr("[Accumulated GC generation %d time %3.7f secs, "
117 "%d GC's, avg GC time %3.7f]",
118 level(), time, sr->invocations,
119 sr->invocations > 0 ? time / sr->invocations : 0.0);
120 }
121
122 // Utility iterator classes
123
124 class GenerationIsInReservedClosure : public SpaceClosure {
125 public:
126 const void* _p;
127 Space* sp;
128 virtual void do_space(Space* s) {
129 if (sp == NULL) {
130 if (s->is_in_reserved(_p)) sp = s;
131 }
132 }
133 GenerationIsInReservedClosure(const void* p) : _p(p), sp(NULL) {}
134 };
135
136 class GenerationIsInClosure : public SpaceClosure {
137 public:
138 const void* _p;
139 Space* sp;
140 virtual void do_space(Space* s) {
141 if (sp == NULL) {
142 if (s->is_in(_p)) sp = s;
143 }
144 }
145 GenerationIsInClosure(const void* p) : _p(p), sp(NULL) {}
146 };
147
148 bool Generation::is_in(const void* p) const {
149 GenerationIsInClosure blk(p);
150 ((Generation*)this)->space_iterate(&blk);
151 return blk.sp != NULL;
152 }
153
154 Generation* Generation::next_gen() const {
155 GenCollectedHeap* gch = GenCollectedHeap::heap();
156 int next = level() + 1;
157 if (next < gch->_n_gens) {
158 return gch->_gens[next];
159 } else {
160 return NULL;
161 }
162 }
163
164 size_t Generation::max_contiguous_available() const {
165 // The largest number of contiguous free words in this or any higher generation.
166 size_t max = 0;
167 for (const Generation* gen = this; gen != NULL; gen = gen->next_gen()) {
168 size_t avail = gen->contiguous_available();
169 if (avail > max) {
170 max = avail;
171 }
172 }
173 return max;
174 }
175
176 bool Generation::promotion_attempt_is_safe(size_t max_promotion_in_bytes) const {
177 size_t available = max_contiguous_available();
178 bool res = (available >= max_promotion_in_bytes);
179 if (PrintGC && Verbose) {
180 gclog_or_tty->print_cr(
181 "Generation: promo attempt is%s safe: available("SIZE_FORMAT") %s max_promo("SIZE_FORMAT")",
182 res? "":" not", available, res? ">=":"<",
183 max_promotion_in_bytes);
184 }
185 return res;
186 }
187
188 // Ignores "ref" and calls allocate().
189 oop Generation::promote(oop obj, size_t obj_size) {
190 assert(obj_size == (size_t)obj->size(), "bad obj_size passed in");
191
192 #ifndef PRODUCT
193 if (Universe::heap()->promotion_should_fail()) {
194 return NULL;
195 }
196 #endif // #ifndef PRODUCT
197
198 HeapWord* result = allocate(obj_size, false);
199 if (result != NULL) {
200 Copy::aligned_disjoint_words((HeapWord*)obj, result, obj_size);
201 return oop(result);
202 } else {
203 GenCollectedHeap* gch = GenCollectedHeap::heap();
204 return gch->handle_failed_promotion(this, obj, obj_size);
205 }
206 }
207
208 oop Generation::par_promote(int thread_num,
209 oop obj, markOop m, size_t word_sz) {
210 // Could do a bad general impl here that gets a lock. But no.
211 ShouldNotCallThis();
212 return NULL;
213 }
214
215 Space* Generation::space_containing(const void* p) const {
216 GenerationIsInReservedClosure blk(p);
217 // Cast away const
218 ((Generation*)this)->space_iterate(&blk);
219 return blk.sp;
220 }
221
222 // Some of these are mediocre general implementations. Should be
223 // overridden to get better performance.
224
225 class GenerationBlockStartClosure : public SpaceClosure {
226 public:
227 const void* _p;
228 HeapWord* _start;
229 virtual void do_space(Space* s) {
230 if (_start == NULL && s->is_in_reserved(_p)) {
231 _start = s->block_start(_p);
232 }
233 }
234 GenerationBlockStartClosure(const void* p) { _p = p; _start = NULL; }
235 };
236
237 HeapWord* Generation::block_start(const void* p) const {
238 GenerationBlockStartClosure blk(p);
239 // Cast away const
240 ((Generation*)this)->space_iterate(&blk);
241 return blk._start;
242 }
243
244 class GenerationBlockSizeClosure : public SpaceClosure {
245 public:
246 const HeapWord* _p;
247 size_t size;
248 virtual void do_space(Space* s) {
249 if (size == 0 && s->is_in_reserved(_p)) {
250 size = s->block_size(_p);
251 }
252 }
253 GenerationBlockSizeClosure(const HeapWord* p) { _p = p; size = 0; }
254 };
255
256 size_t Generation::block_size(const HeapWord* p) const {
257 GenerationBlockSizeClosure blk(p);
258 // Cast away const
259 ((Generation*)this)->space_iterate(&blk);
260 assert(blk.size > 0, "seems reasonable");
261 return blk.size;
262 }
263
264 class GenerationBlockIsObjClosure : public SpaceClosure {
265 public:
266 const HeapWord* _p;
267 bool is_obj;
268 virtual void do_space(Space* s) {
269 if (!is_obj && s->is_in_reserved(_p)) {
270 is_obj |= s->block_is_obj(_p);
271 }
272 }
273 GenerationBlockIsObjClosure(const HeapWord* p) { _p = p; is_obj = false; }
274 };
275
276 bool Generation::block_is_obj(const HeapWord* p) const {
277 GenerationBlockIsObjClosure blk(p);
278 // Cast away const
279 ((Generation*)this)->space_iterate(&blk);
280 return blk.is_obj;
281 }
282
283 class GenerationOopIterateClosure : public SpaceClosure {
284 public:
285 ExtendedOopClosure* _cl;
286 virtual void do_space(Space* s) {
287 s->oop_iterate(_cl);
288 }
289 GenerationOopIterateClosure(ExtendedOopClosure* cl) :
290 _cl(cl) {}
291 };
292
293 void Generation::oop_iterate(ExtendedOopClosure* cl) {
294 GenerationOopIterateClosure blk(cl);
295 space_iterate(&blk);
296 }
297
298 void Generation::younger_refs_in_space_iterate(Space* sp,
299 OopsInGenClosure* cl) {
300 GenRemSet* rs = SharedHeap::heap()->rem_set();
301 rs->younger_refs_in_space_iterate(sp, cl);
302 }
303
304 class GenerationObjIterateClosure : public SpaceClosure {
305 private:
306 ObjectClosure* _cl;
307 public:
308 virtual void do_space(Space* s) {
309 s->object_iterate(_cl);
310 }
311 GenerationObjIterateClosure(ObjectClosure* cl) : _cl(cl) {}
312 };
313
314 void Generation::object_iterate(ObjectClosure* cl) {
315 GenerationObjIterateClosure blk(cl);
316 space_iterate(&blk);
317 }
318
319 class GenerationSafeObjIterateClosure : public SpaceClosure {
320 private:
321 ObjectClosure* _cl;
322 public:
323 virtual void do_space(Space* s) {
324 s->safe_object_iterate(_cl);
325 }
326 GenerationSafeObjIterateClosure(ObjectClosure* cl) : _cl(cl) {}
327 };
328
329 void Generation::safe_object_iterate(ObjectClosure* cl) {
330 GenerationSafeObjIterateClosure blk(cl);
331 space_iterate(&blk);
332 }
333
334 void Generation::prepare_for_compaction(CompactPoint* cp) {
335 // Generic implementation, can be specialized
336 CompactibleSpace* space = first_compaction_space();
337 while (space != NULL) {
338 space->prepare_for_compaction(cp);
339 space = space->next_compaction_space();
340 }
341 }
342
343 class AdjustPointersClosure: public SpaceClosure {
344 public:
345 void do_space(Space* sp) {
346 sp->adjust_pointers();
347 }
348 };
349
350 void Generation::adjust_pointers() {
351 // Note that this is done over all spaces, not just the compactible
352 // ones.
353 AdjustPointersClosure blk;
354 space_iterate(&blk, true);
355 }
356
357 void Generation::compact() {
358 CompactibleSpace* sp = first_compaction_space();
359 while (sp != NULL) {
360 sp->compact();
361 sp = sp->next_compaction_space();
362 }
363 }
364
365 CardGeneration::CardGeneration(ReservedSpace rs, size_t initial_byte_size,
366 int level,
367 GenRemSet* remset) :
368 Generation(rs, initial_byte_size, level), _rs(remset),
369 _shrink_factor(0), _min_heap_delta_bytes(), _capacity_at_prologue(),
370 _used_at_prologue()
371 {
372 HeapWord* start = (HeapWord*)rs.base();
373 size_t reserved_byte_size = rs.size();
374 assert((uintptr_t(start) & 3) == 0, "bad alignment");
375 assert((reserved_byte_size & 3) == 0, "bad alignment");
376 MemRegion reserved_mr(start, heap_word_size(reserved_byte_size));
377 _bts = new BlockOffsetSharedArray(reserved_mr,
378 heap_word_size(initial_byte_size));
379 MemRegion committed_mr(start, heap_word_size(initial_byte_size));
380 _rs->resize_covered_region(committed_mr);
381 if (_bts == NULL)
382 vm_exit_during_initialization("Could not allocate a BlockOffsetArray");
383
384 // Verify that the start and end of this generation is the start of a card.
385 // If this wasn't true, a single card could span more than on generation,
386 // which would cause problems when we commit/uncommit memory, and when we
387 // clear and dirty cards.
388 guarantee(_rs->is_aligned(reserved_mr.start()), "generation must be card aligned");
389 if (reserved_mr.end() != Universe::heap()->reserved_region().end()) {
390 // Don't check at the very end of the heap as we'll assert that we're probing off
391 // the end if we try.
392 guarantee(_rs->is_aligned(reserved_mr.end()), "generation must be card aligned");
393 }
394 _min_heap_delta_bytes = MinHeapDeltaBytes;
395 _capacity_at_prologue = initial_byte_size;
396 _used_at_prologue = 0;
397 }
398
399 bool CardGeneration::expand(size_t bytes, size_t expand_bytes) {
400 assert_locked_or_safepoint(Heap_lock);
401 if (bytes == 0) {
402 return true; // That's what grow_by(0) would return
403 }
404 size_t aligned_bytes = ReservedSpace::page_align_size_up(bytes);
405 if (aligned_bytes == 0){
406 // The alignment caused the number of bytes to wrap. An expand_by(0) will
407 // return true with the implication that an expansion was done when it
408 // was not. A call to expand implies a best effort to expand by "bytes"
409 // but not a guarantee. Align down to give a best effort. This is likely
410 // the most that the generation can expand since it has some capacity to
411 // start with.
412 aligned_bytes = ReservedSpace::page_align_size_down(bytes);
413 }
414 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
415 bool success = false;
416 if (aligned_expand_bytes > aligned_bytes) {
417 success = grow_by(aligned_expand_bytes);
418 }
419 if (!success) {
420 success = grow_by(aligned_bytes);
421 }
422 if (!success) {
423 success = grow_to_reserved();
424 }
425 if (PrintGC && Verbose) {
426 if (success && GC_locker::is_active_and_needs_gc()) {
427 gclog_or_tty->print_cr("Garbage collection disabled, expanded heap instead");
428 }
429 }
430
431 return success;
432 }
433
434
435 // No young generation references, clear this generation's cards.
436 void CardGeneration::clear_remembered_set() {
437 _rs->clear(reserved());
438 }
439
440
441 // Objects in this generation may have moved, invalidate this
442 // generation's cards.
443 void CardGeneration::invalidate_remembered_set() {
444 _rs->invalidate(used_region());
445 }
446
447
448 void CardGeneration::compute_new_size() {
449 assert(_shrink_factor <= 100, "invalid shrink factor");
450 size_t current_shrink_factor = _shrink_factor;
451 _shrink_factor = 0;
452
453 // We don't have floating point command-line arguments
454 // Note: argument processing ensures that MinHeapFreeRatio < 100.
455 const double minimum_free_percentage = MinHeapFreeRatio / 100.0;
456 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
457
458 // Compute some numbers about the state of the heap.
459 const size_t used_after_gc = used();
460 const size_t capacity_after_gc = capacity();
461
462 const double min_tmp = used_after_gc / maximum_used_percentage;
463 size_t minimum_desired_capacity = (size_t)MIN2(min_tmp, double(max_uintx));
464 // Don't shrink less than the initial generation size
465 minimum_desired_capacity = MAX2(minimum_desired_capacity,
466 spec()->init_size());
467 assert(used_after_gc <= minimum_desired_capacity, "sanity check");
468
469 if (PrintGC && Verbose) {
470 const size_t free_after_gc = free();
471 const double free_percentage = ((double)free_after_gc) / capacity_after_gc;
472 gclog_or_tty->print_cr("TenuredGeneration::compute_new_size: ");
473 gclog_or_tty->print_cr(" "
474 " minimum_free_percentage: %6.2f"
475 " maximum_used_percentage: %6.2f",
476 minimum_free_percentage,
477 maximum_used_percentage);
478 gclog_or_tty->print_cr(" "
479 " free_after_gc : %6.1fK"
480 " used_after_gc : %6.1fK"
481 " capacity_after_gc : %6.1fK",
482 free_after_gc / (double) K,
483 used_after_gc / (double) K,
484 capacity_after_gc / (double) K);
485 gclog_or_tty->print_cr(" "
486 " free_percentage: %6.2f",
487 free_percentage);
488 }
489
490 if (capacity_after_gc < minimum_desired_capacity) {
491 // If we have less free space than we want then expand
492 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
493 // Don't expand unless it's significant
494 if (expand_bytes >= _min_heap_delta_bytes) {
495 expand(expand_bytes, 0); // safe if expansion fails
496 }
497 if (PrintGC && Verbose) {
498 gclog_or_tty->print_cr(" expanding:"
499 " minimum_desired_capacity: %6.1fK"
500 " expand_bytes: %6.1fK"
501 " _min_heap_delta_bytes: %6.1fK",
502 minimum_desired_capacity / (double) K,
503 expand_bytes / (double) K,
504 _min_heap_delta_bytes / (double) K);
505 }
506 return;
507 }
508
509 // No expansion, now see if we want to shrink
510 size_t shrink_bytes = 0;
511 // We would never want to shrink more than this
512 size_t max_shrink_bytes = capacity_after_gc - minimum_desired_capacity;
513
514 if (MaxHeapFreeRatio < 100) {
515 const double maximum_free_percentage = MaxHeapFreeRatio / 100.0;
516 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
517 const double max_tmp = used_after_gc / minimum_used_percentage;
518 size_t maximum_desired_capacity = (size_t)MIN2(max_tmp, double(max_uintx));
519 maximum_desired_capacity = MAX2(maximum_desired_capacity,
520 spec()->init_size());
521 if (PrintGC && Verbose) {
522 gclog_or_tty->print_cr(" "
523 " maximum_free_percentage: %6.2f"
524 " minimum_used_percentage: %6.2f",
525 maximum_free_percentage,
526 minimum_used_percentage);
527 gclog_or_tty->print_cr(" "
528 " _capacity_at_prologue: %6.1fK"
529 " minimum_desired_capacity: %6.1fK"
530 " maximum_desired_capacity: %6.1fK",
531 _capacity_at_prologue / (double) K,
532 minimum_desired_capacity / (double) K,
533 maximum_desired_capacity / (double) K);
534 }
535 assert(minimum_desired_capacity <= maximum_desired_capacity,
536 "sanity check");
537
538 if (capacity_after_gc > maximum_desired_capacity) {
539 // Capacity too large, compute shrinking size
540 shrink_bytes = capacity_after_gc - maximum_desired_capacity;
541 // We don't want shrink all the way back to initSize if people call
542 // System.gc(), because some programs do that between "phases" and then
543 // we'd just have to grow the heap up again for the next phase. So we
544 // damp the shrinking: 0% on the first call, 10% on the second call, 40%
545 // on the third call, and 100% by the fourth call. But if we recompute
546 // size without shrinking, it goes back to 0%.
547 shrink_bytes = shrink_bytes / 100 * current_shrink_factor;
548 assert(shrink_bytes <= max_shrink_bytes, "invalid shrink size");
549 if (current_shrink_factor == 0) {
550 _shrink_factor = 10;
551 } else {
552 _shrink_factor = MIN2(current_shrink_factor * 4, (size_t) 100);
553 }
554 if (PrintGC && Verbose) {
555 gclog_or_tty->print_cr(" "
556 " shrinking:"
557 " initSize: %.1fK"
558 " maximum_desired_capacity: %.1fK",
559 spec()->init_size() / (double) K,
560 maximum_desired_capacity / (double) K);
561 gclog_or_tty->print_cr(" "
562 " shrink_bytes: %.1fK"
563 " current_shrink_factor: " SIZE_FORMAT
564 " new shrink factor: " SIZE_FORMAT
565 " _min_heap_delta_bytes: %.1fK",
566 shrink_bytes / (double) K,
567 current_shrink_factor,
568 _shrink_factor,
569 _min_heap_delta_bytes / (double) K);
570 }
571 }
572 }
573
574 if (capacity_after_gc > _capacity_at_prologue) {
575 // We might have expanded for promotions, in which case we might want to
576 // take back that expansion if there's room after GC. That keeps us from
577 // stretching the heap with promotions when there's plenty of room.
578 size_t expansion_for_promotion = capacity_after_gc - _capacity_at_prologue;
579 expansion_for_promotion = MIN2(expansion_for_promotion, max_shrink_bytes);
580 // We have two shrinking computations, take the largest
581 shrink_bytes = MAX2(shrink_bytes, expansion_for_promotion);
582 assert(shrink_bytes <= max_shrink_bytes, "invalid shrink size");
583 if (PrintGC && Verbose) {
584 gclog_or_tty->print_cr(" "
585 " aggressive shrinking:"
586 " _capacity_at_prologue: %.1fK"
587 " capacity_after_gc: %.1fK"
588 " expansion_for_promotion: %.1fK"
589 " shrink_bytes: %.1fK",
590 capacity_after_gc / (double) K,
591 _capacity_at_prologue / (double) K,
592 expansion_for_promotion / (double) K,
593 shrink_bytes / (double) K);
594 }
595 }
596 // Don't shrink unless it's significant
597 if (shrink_bytes >= _min_heap_delta_bytes) {
598 shrink(shrink_bytes);
599 }
600 }
601
602 // Currently nothing to do.
603 void CardGeneration::prepare_for_verify() {}
604