1 /*
2 * Copyright (c) 2013, 2015, Red Hat, Inc. and/or its affiliates.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation.
7 *
8 * This code is distributed in the hope that it will be useful, but WITHOUT
9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
11 * version 2 for more details (a copy is included in the LICENSE file that
12 * accompanied this code).
13 *
14 * You should have received a copy of the GNU General Public License version
15 * 2 along with this work; if not, write to the Free Software Foundation,
16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
17 *
18 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
19 * or visit www.oracle.com if you need additional information or have any
20 * questions.
21 *
22 */
23
24 #include "precompiled.hpp"
25 #include "memory/allocation.hpp"
26 #include "gc_implementation/shenandoah/brooksPointer.hpp"
27 #include "gc_implementation/shenandoah/shenandoahHeap.hpp"
28 #include "gc_implementation/shenandoah/shenandoahHeap.inline.hpp"
29 #include "gc_implementation/shenandoah/shenandoahHeapRegion.hpp"
30 #include "gc_implementation/shenandoah/shenandoahMarkingContext.inline.hpp"
31 #include "memory/space.inline.hpp"
32 #include "memory/universe.hpp"
33 #include "oops/oop.inline.hpp"
34 #include "runtime/java.hpp"
35 #include "runtime/mutexLocker.hpp"
36 #include "runtime/os.hpp"
37 #include "runtime/safepoint.hpp"
38
39 size_t ShenandoahHeapRegion::RegionCount = 0;
40 size_t ShenandoahHeapRegion::RegionSizeBytes = 0;
41 size_t ShenandoahHeapRegion::RegionSizeWords = 0;
42 size_t ShenandoahHeapRegion::RegionSizeBytesShift = 0;
43 size_t ShenandoahHeapRegion::RegionSizeWordsShift = 0;
44 size_t ShenandoahHeapRegion::RegionSizeBytesMask = 0;
45 size_t ShenandoahHeapRegion::RegionSizeWordsMask = 0;
46 size_t ShenandoahHeapRegion::HumongousThresholdBytes = 0;
47 size_t ShenandoahHeapRegion::HumongousThresholdWords = 0;
48 size_t ShenandoahHeapRegion::MaxTLABSizeBytes = 0;
49 size_t ShenandoahHeapRegion::MaxTLABSizeWords = 0;
50
51 ShenandoahHeapRegion::ShenandoahHeapRegion(ShenandoahHeap* heap, HeapWord* start,
52 size_t size_words, size_t index, bool committed) :
53 _heap(heap),
54 _region_number(index),
55 _live_data(0),
56 _reserved(MemRegion(start, size_words)),
57 _tlab_allocs(0),
58 _gclab_allocs(0),
59 _shared_allocs(0),
60 _new_top(NULL),
61 _critical_pins(0),
62 _state(committed ? _empty_committed : _empty_uncommitted),
63 _empty_time(os::elapsedTime()),
64 _pacer(ShenandoahPacing ? heap->pacer() : NULL) {
65
66 ContiguousSpace::initialize(_reserved, true, committed);
67 }
68
69 size_t ShenandoahHeapRegion::region_number() const {
70 return _region_number;
71 }
72
73 void ShenandoahHeapRegion::report_illegal_transition(const char *method) {
74 ResourceMark rm;
75 stringStream ss;
76 ss.print("Illegal region state transition from \"%s\", at %s\n ", region_state_to_string(_state), method);
77 print_on(&ss);
78 fatal(ss.as_string());
79 }
80
81 void ShenandoahHeapRegion::make_regular_allocation() {
82 _heap->assert_heaplock_owned_by_current_thread();
83 switch (_state) {
84 case _empty_uncommitted:
85 do_commit();
86 case _empty_committed:
87 _state = _regular;
88 case _regular:
89 case _pinned:
90 return;
91 default:
92 report_illegal_transition("regular allocation");
93 }
94 }
95
96 void ShenandoahHeapRegion::make_regular_bypass() {
97 _heap->assert_heaplock_owned_by_current_thread();
98 assert (_heap->is_full_gc_in_progress(), "only for full GC");
99
100 switch (_state) {
101 case _empty_uncommitted:
102 do_commit();
103 case _empty_committed:
104 case _cset:
105 case _humongous_start:
106 case _humongous_cont:
107 _state = _regular;
108 return;
109 case _pinned_cset:
110 _state = _pinned;
111 return;
112 case _regular:
113 case _pinned:
114 return;
115 default:
116 report_illegal_transition("regular bypass");
117 }
118 }
119
120 void ShenandoahHeapRegion::make_humongous_start() {
121 _heap->assert_heaplock_owned_by_current_thread();
122 switch (_state) {
123 case _empty_uncommitted:
124 do_commit();
125 case _empty_committed:
126 _state = _humongous_start;
127 return;
128 default:
129 report_illegal_transition("humongous start allocation");
130 }
131 }
132
133 void ShenandoahHeapRegion::make_humongous_start_bypass() {
134 _heap->assert_heaplock_owned_by_current_thread();
135 assert (_heap->is_full_gc_in_progress(), "only for full GC");
136
137 switch (_state) {
138 case _empty_committed:
139 case _regular:
140 case _humongous_start:
141 case _humongous_cont:
142 _state = _humongous_start;
143 return;
144 default:
145 report_illegal_transition("humongous start bypass");
146 }
147 }
148
149 void ShenandoahHeapRegion::make_humongous_cont() {
150 _heap->assert_heaplock_owned_by_current_thread();
151 switch (_state) {
152 case _empty_uncommitted:
153 do_commit();
154 case _empty_committed:
155 _state = _humongous_cont;
156 return;
157 default:
158 report_illegal_transition("humongous continuation allocation");
159 }
160 }
161
162 void ShenandoahHeapRegion::make_humongous_cont_bypass() {
163 _heap->assert_heaplock_owned_by_current_thread();
164 assert (_heap->is_full_gc_in_progress(), "only for full GC");
165
166 switch (_state) {
167 case _empty_committed:
168 case _regular:
169 case _humongous_start:
170 case _humongous_cont:
171 _state = _humongous_cont;
172 return;
173 default:
174 report_illegal_transition("humongous continuation bypass");
175 }
176 }
177
178 void ShenandoahHeapRegion::make_pinned() {
179 _heap->assert_heaplock_owned_by_current_thread();
180 switch (_state) {
181 case _regular:
182 assert (_critical_pins == 0, "sanity");
183 _state = _pinned;
184 case _pinned_cset:
185 case _pinned:
186 _critical_pins++;
187 return;
188 case _humongous_start:
189 assert (_critical_pins == 0, "sanity");
190 _state = _pinned_humongous_start;
191 case _pinned_humongous_start:
192 _critical_pins++;
193 return;
194 case _cset:
195 guarantee(_heap->cancelled_gc(), "only valid when evac has been cancelled");
196 assert (_critical_pins == 0, "sanity");
197 _state = _pinned_cset;
198 _critical_pins++;
199 return;
200 default:
201 report_illegal_transition("pinning");
202 }
203 }
204
205 void ShenandoahHeapRegion::make_unpinned() {
206 _heap->assert_heaplock_owned_by_current_thread();
207 switch (_state) {
208 case _pinned:
209 assert (_critical_pins > 0, "sanity");
210 _critical_pins--;
211 if (_critical_pins == 0) {
212 _state = _regular;
213 }
214 return;
215 case _regular:
216 case _humongous_start:
217 assert (_critical_pins == 0, "sanity");
218 return;
219 case _pinned_cset:
220 guarantee(_heap->cancelled_gc(), "only valid when evac has been cancelled");
221 assert (_critical_pins > 0, "sanity");
222 _critical_pins--;
223 if (_critical_pins == 0) {
224 _state = _cset;
225 }
226 return;
227 case _pinned_humongous_start:
228 assert (_critical_pins > 0, "sanity");
229 _critical_pins--;
230 if (_critical_pins == 0) {
231 _state = _humongous_start;
232 }
233 return;
234 default:
235 report_illegal_transition("unpinning");
236 }
237 }
238
239 void ShenandoahHeapRegion::make_cset() {
240 _heap->assert_heaplock_owned_by_current_thread();
241 switch (_state) {
242 case _regular:
243 _state = _cset;
244 case _cset:
245 return;
246 default:
247 report_illegal_transition("cset");
248 }
249 }
250
251 void ShenandoahHeapRegion::make_trash() {
252 _heap->assert_heaplock_owned_by_current_thread();
253 switch (_state) {
254 case _cset:
255 // Reclaiming cset regions
256 case _humongous_start:
257 case _humongous_cont:
258 // Reclaiming humongous regions
259 case _regular:
260 // Immediate region reclaim
261 _state = _trash;
262 return;
263 default:
264 report_illegal_transition("trashing");
265 }
266 }
267
268 void ShenandoahHeapRegion::make_empty() {
269 _heap->assert_heaplock_owned_by_current_thread();
270 switch (_state) {
271 case _trash:
272 _state = _empty_committed;
273 _empty_time = os::elapsedTime();
274 return;
275 default:
276 report_illegal_transition("emptying");
277 }
278 }
279
280 void ShenandoahHeapRegion::make_uncommitted() {
281 _heap->assert_heaplock_owned_by_current_thread();
282 switch (_state) {
283 case _empty_committed:
284 do_uncommit();
285 _state = _empty_uncommitted;
286 return;
287 default:
288 report_illegal_transition("uncommiting");
289 }
290 }
291
292 void ShenandoahHeapRegion::make_committed_bypass() {
293 _heap->assert_heaplock_owned_by_current_thread();
294 assert (_heap->is_full_gc_in_progress(), "only for full GC");
295
296 switch (_state) {
297 case _empty_uncommitted:
298 do_commit();
299 _state = _empty_committed;
300 return;
301 default:
302 report_illegal_transition("commit bypass");
303 }
304 }
305
306 bool ShenandoahHeapRegion::rollback_allocation(uint size) {
307 set_top(top() - size);
308 return true;
309 }
310
311 void ShenandoahHeapRegion::clear_live_data() {
312 OrderAccess::release_store_fence((volatile jint*)&_live_data, 0);
313 }
314
315 void ShenandoahHeapRegion::reset_alloc_metadata() {
316 _tlab_allocs = 0;
317 _gclab_allocs = 0;
318 _shared_allocs = 0;
319 }
320
321 void ShenandoahHeapRegion::reset_alloc_metadata_to_shared() {
322 if (used() > 0) {
323 _tlab_allocs = 0;
324 _gclab_allocs = 0;
325 _shared_allocs = used() >> LogHeapWordSize;
326 } else {
327 reset_alloc_metadata();
328 }
329 }
330
331 size_t ShenandoahHeapRegion::get_shared_allocs() const {
332 return _shared_allocs * HeapWordSize;
333 }
334
335 size_t ShenandoahHeapRegion::get_tlab_allocs() const {
336 return _tlab_allocs * HeapWordSize;
337 }
338
339 size_t ShenandoahHeapRegion::get_gclab_allocs() const {
340 return _gclab_allocs * HeapWordSize;
341 }
342
343 void ShenandoahHeapRegion::set_live_data(size_t s) {
344 assert(Thread::current()->is_VM_thread(), "by VM thread");
345 size_t v = s >> LogHeapWordSize;
346 assert(v < (size_t)max_jint, "sanity");
347 _live_data = (jint)v;
348 }
349
350 size_t ShenandoahHeapRegion::get_live_data_words() const {
351 jint v = OrderAccess::load_acquire((volatile jint*)&_live_data);
352 assert(v >= 0, "sanity");
353 return (size_t)v;
354 }
355
356 size_t ShenandoahHeapRegion::get_live_data_bytes() const {
357 return get_live_data_words() * HeapWordSize;
358 }
359
360 bool ShenandoahHeapRegion::has_live() const {
361 return get_live_data_words() != 0;
362 }
363
364 size_t ShenandoahHeapRegion::garbage() const {
365 assert(used() >= get_live_data_bytes(), err_msg("Live Data must be a subset of used() live: "SIZE_FORMAT" used: "SIZE_FORMAT,
366 get_live_data_bytes(), used()));
367 size_t result = used() - get_live_data_bytes();
368 return result;
369 }
370
371 bool ShenandoahHeapRegion::in_collection_set() const {
372 return _heap->region_in_collection_set(_region_number);
373 }
374
375 void ShenandoahHeapRegion::print_on(outputStream* st) const {
376 st->print("|");
377 st->print(SIZE_FORMAT_W(5), this->_region_number);
378
379 switch (_state) {
380 case _empty_uncommitted:
381 st->print("|EU ");
382 break;
383 case _empty_committed:
384 st->print("|EC ");
385 break;
386 case _regular:
387 st->print("|R ");
388 break;
389 case _humongous_start:
390 st->print("|H ");
391 break;
392 case _pinned_humongous_start:
393 st->print("|HP ");
394 break;
395 case _humongous_cont:
396 st->print("|HC ");
397 break;
398 case _cset:
399 st->print("|CS ");
400 break;
401 case _trash:
402 st->print("|T ");
403 break;
404 case _pinned:
405 st->print("|P ");
406 break;
407 case _pinned_cset:
408 st->print("|CSP");
409 break;
410 default:
411 ShouldNotReachHere();
412 }
413 st->print("|BTE " INTPTR_FORMAT_W(12) ", " INTPTR_FORMAT_W(12) ", " INTPTR_FORMAT_W(12),
414 p2i(bottom()), p2i(top()), p2i(end()));
415 st->print("|TAMS " INTPTR_FORMAT_W(12) ", " INTPTR_FORMAT_W(12),
416 p2i(_heap->complete_marking_context()->top_at_mark_start(region_number())),
417 p2i(_heap->next_marking_context()->top_at_mark_start(region_number())));
418 st->print("|U " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(used()), proper_unit_for_byte_size(used()));
419 st->print("|T " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(get_tlab_allocs()), proper_unit_for_byte_size(get_tlab_allocs()));
420 st->print("|G " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(get_gclab_allocs()), proper_unit_for_byte_size(get_gclab_allocs()));
421 st->print("|S " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(get_shared_allocs()), proper_unit_for_byte_size(get_shared_allocs()));
422 st->print("|L " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(get_live_data_bytes()), proper_unit_for_byte_size(get_live_data_bytes()));
423 st->print("|CP " SIZE_FORMAT_W(3), _critical_pins);
424
425 st->cr();
426 }
427
428 void ShenandoahHeapRegion::fill_region() {
429 if (free() > (BrooksPointer::word_size() + CollectedHeap::min_fill_size())) {
430 HeapWord* filler = allocate(BrooksPointer::word_size(), ShenandoahHeap::_alloc_shared);
431 HeapWord* obj = allocate(end() - top(), ShenandoahHeap::_alloc_shared);
432 _heap->fill_with_object(obj, end() - obj);
433 BrooksPointer::initialize(oop(obj));
434 }
435 }
436
437 ShenandoahHeapRegion* ShenandoahHeapRegion::humongous_start_region() const {
438 assert(is_humongous(), "Must be a part of the humongous region");
439 size_t reg_num = region_number();
440 ShenandoahHeapRegion* r = const_cast<ShenandoahHeapRegion*>(this);
441 while (!r->is_humongous_start()) {
442 assert(reg_num > 0, "Sanity");
443 reg_num --;
444 r = _heap->get_region(reg_num);
445 assert(r->is_humongous(), "Must be a part of the humongous region");
446 }
447 assert(r->is_humongous_start(), "Must be");
448 return r;
449 }
450
451 void ShenandoahHeapRegion::recycle() {
452 ContiguousSpace::clear(false);
453 if (ZapUnusedHeapArea) {
454 ContiguousSpace::mangle_unused_area_complete();
455 }
456 clear_live_data();
457 reset_alloc_metadata();
458
459 ShenandoahMarkingContext* const compl_ctx = _heap->complete_marking_context();
460
461 // Reset C-TAMS pointer to ensure size-based iteration, everything
462 // in that regions is going to be new objects.
463 compl_ctx->set_top_at_mark_start(region_number(), bottom());
464 // We can only safely reset the C-TAMS pointer if the bitmap is clear for that region.
465 assert(compl_ctx->is_bitmap_clear_range(bottom(), end()), "must be clear");
466
467 make_empty();
468 }
469
470 HeapWord* ShenandoahHeapRegion::block_start_const(const void* p) const {
471 assert(MemRegion(bottom(), end()).contains(p),
472 err_msg("p ("PTR_FORMAT") not in space ["PTR_FORMAT", "PTR_FORMAT")",
473 p2i(p), p2i(bottom()), p2i(end())));
474 if (p >= top()) {
475 return top();
476 } else {
477 HeapWord* last = bottom() + BrooksPointer::word_size();
478 HeapWord* cur = last;
479 while (cur <= p) {
480 last = cur;
481 cur += oop(cur)->size() + BrooksPointer::word_size();
482 }
483 shenandoah_assert_correct(NULL, oop(last));
484 return last;
485 }
486 }
487
488 void ShenandoahHeapRegion::setup_sizes(size_t initial_heap_size, size_t max_heap_size) {
489 // Absolute minimums we should not ever break:
490 static const size_t MIN_REGION_SIZE = 256*K;
491 static const size_t MIN_NUM_REGIONS = 10;
492
493 size_t region_size;
494 if (FLAG_IS_DEFAULT(ShenandoahHeapRegionSize)) {
495 if (ShenandoahMinRegionSize > initial_heap_size / MIN_NUM_REGIONS) {
496 err_msg message("Initial heap size (" SIZE_FORMAT "K) is too low to afford the minimum number "
497 "of regions (" SIZE_FORMAT ") of minimum region size (" SIZE_FORMAT "K).",
498 initial_heap_size/K, MIN_NUM_REGIONS, ShenandoahMinRegionSize/K);
499 vm_exit_during_initialization("Invalid -XX:ShenandoahMinRegionSize option", message);
500 }
501 if (ShenandoahMinRegionSize < MIN_REGION_SIZE) {
502 err_msg message("" SIZE_FORMAT "K should not be lower than minimum region size (" SIZE_FORMAT "K).",
503 ShenandoahMinRegionSize/K, MIN_REGION_SIZE/K);
504 vm_exit_during_initialization("Invalid -XX:ShenandoahMinRegionSize option", message);
505 }
506 if (ShenandoahMinRegionSize < MinTLABSize) {
507 err_msg message("" SIZE_FORMAT "K should not be lower than TLAB size size (" SIZE_FORMAT "K).",
508 ShenandoahMinRegionSize/K, MinTLABSize/K);
509 vm_exit_during_initialization("Invalid -XX:ShenandoahMinRegionSize option", message);
510 }
511 if (ShenandoahMaxRegionSize < MIN_REGION_SIZE) {
512 err_msg message("" SIZE_FORMAT "K should not be lower than min region size (" SIZE_FORMAT "K).",
513 ShenandoahMaxRegionSize/K, MIN_REGION_SIZE/K);
514 vm_exit_during_initialization("Invalid -XX:ShenandoahMaxRegionSize option", message);
515 }
516 if (ShenandoahMinRegionSize > ShenandoahMaxRegionSize) {
517 err_msg message("Minimum (" SIZE_FORMAT "K) should be larger than maximum (" SIZE_FORMAT "K).",
518 ShenandoahMinRegionSize/K, ShenandoahMaxRegionSize/K);
519 vm_exit_during_initialization("Invalid -XX:ShenandoahMinRegionSize or -XX:ShenandoahMaxRegionSize", message);
520 }
521
522 // We rapidly expand to max_heap_size in most scenarios, so that is the measure
523 // for usual heap sizes. Do not depend on initial_heap_size here.
524 region_size = max_heap_size / ShenandoahTargetNumRegions;
525
526 // Now make sure that we don't go over or under our limits.
527 region_size = MAX2(ShenandoahMinRegionSize, region_size);
528 region_size = MIN2(ShenandoahMaxRegionSize, region_size);
529
530 } else {
531 if (ShenandoahHeapRegionSize > initial_heap_size / MIN_NUM_REGIONS) {
532 err_msg message("Initial heap size (" SIZE_FORMAT "K) is too low to afford the minimum number "
533 "of regions (" SIZE_FORMAT ") of requested size (" SIZE_FORMAT "K).",
534 initial_heap_size/K, MIN_NUM_REGIONS, ShenandoahHeapRegionSize/K);
535 vm_exit_during_initialization("Invalid -XX:ShenandoahHeapRegionSize option", message);
536 }
537 if (ShenandoahHeapRegionSize < ShenandoahMinRegionSize) {
538 err_msg message("Heap region size (" SIZE_FORMAT "K) should be larger than min region size (" SIZE_FORMAT "K).",
539 ShenandoahHeapRegionSize/K, ShenandoahMinRegionSize/K);
540 vm_exit_during_initialization("Invalid -XX:ShenandoahHeapRegionSize option", message);
541 }
542 if (ShenandoahHeapRegionSize > ShenandoahMaxRegionSize) {
543 err_msg message("Heap region size (" SIZE_FORMAT "K) should be lower than max region size (" SIZE_FORMAT "K).",
544 ShenandoahHeapRegionSize/K, ShenandoahMaxRegionSize/K);
545 vm_exit_during_initialization("Invalid -XX:ShenandoahHeapRegionSize option", message);
546 }
547 region_size = ShenandoahHeapRegionSize;
548 }
549
550 if (1 > ShenandoahHumongousThreshold || ShenandoahHumongousThreshold > 100) {
551 vm_exit_during_initialization("Invalid -XX:ShenandoahHumongousThreshold option, should be within [1..100]");
552 }
553
554 // Make sure region size is at least one large page, if enabled.
555 // Otherwise, mem-protecting one region may falsely protect the adjacent
556 // regions too.
557 if (UseLargePages) {
558 region_size = MAX2(region_size, os::large_page_size());
559 }
560
561 int region_size_log = log2_long((jlong) region_size);
562 // Recalculate the region size to make sure it's a power of
563 // 2. This means that region_size is the largest power of 2 that's
564 // <= what we've calculated so far.
565 region_size = (size_t(1) << region_size_log);
566
567 // Now, set up the globals.
568 guarantee(RegionSizeBytesShift == 0, "we should only set it once");
569 RegionSizeBytesShift = (size_t)region_size_log;
570
571 guarantee(RegionSizeWordsShift == 0, "we should only set it once");
572 RegionSizeWordsShift = RegionSizeBytesShift - LogHeapWordSize;
573
574 guarantee(RegionSizeBytes == 0, "we should only set it once");
575 RegionSizeBytes = region_size;
576 RegionSizeWords = RegionSizeBytes >> LogHeapWordSize;
577 assert (RegionSizeWords*HeapWordSize == RegionSizeBytes, "sanity");
578
579 guarantee(RegionSizeWordsMask == 0, "we should only set it once");
580 RegionSizeWordsMask = RegionSizeWords - 1;
581
582 guarantee(RegionSizeBytesMask == 0, "we should only set it once");
583 RegionSizeBytesMask = RegionSizeBytes - 1;
584
585 guarantee(RegionCount == 0, "we should only set it once");
586 RegionCount = max_heap_size / RegionSizeBytes;
587
588 guarantee(HumongousThresholdWords == 0, "we should only set it once");
589 HumongousThresholdWords = RegionSizeWords * ShenandoahHumongousThreshold / 100;
590 assert (HumongousThresholdWords <= RegionSizeWords, "sanity");
591
592 guarantee(HumongousThresholdBytes == 0, "we should only set it once");
593 HumongousThresholdBytes = HumongousThresholdWords * HeapWordSize;
594 assert (HumongousThresholdBytes <= RegionSizeBytes, "sanity");
595
596 // The rationale for trimming the TLAB sizes has to do with the raciness in
597 // TLAB allocation machinery. It may happen that TLAB sizing policy polls Shenandoah
598 // about next free size, gets the answer for region #N, goes away for a while, then
599 // tries to allocate in region #N, and fail because some other thread have claimed part
600 // of the region #N, and then the freeset allocation code has to retire the region #N,
601 // before moving the allocation to region #N+1.
602 //
603 // The worst case realizes when "answer" is "region size", which means it could
604 // prematurely retire an entire region. Having smaller TLABs does not fix that
605 // completely, but reduces the probability of too wasteful region retirement.
606 // With current divisor, we will waste no more than 1/8 of region size in the worst
607 // case. This also has a secondary effect on collection set selection: even under
608 // the race, the regions would be at least 7/8 used, which allows relying on
609 // "used" - "live" for cset selection. Otherwise, we can get the fragmented region
610 // below the garbage threshold that would never be considered for collection.
611 //
612 // The whole thing would be mitigated if Elastic TLABs were enabled, but there
613 // is no support in this JDK.
614 //
615 guarantee(MaxTLABSizeBytes == 0, "we should only set it once");
616 MaxTLABSizeBytes = MIN2(RegionSizeBytes / 8, HumongousThresholdBytes);
617 assert (MaxTLABSizeBytes > MinTLABSize, "should be larger");
618
619 guarantee(MaxTLABSizeWords == 0, "we should only set it once");
620 MaxTLABSizeWords = MaxTLABSizeBytes / HeapWordSize;
621
622 log_info(gc, init)("Regions: " SIZE_FORMAT " x " SIZE_FORMAT "%s",
623 RegionCount, byte_size_in_proper_unit(RegionSizeBytes), proper_unit_for_byte_size(RegionSizeBytes));
624 log_info(gc, init)("Humongous object threshold: " SIZE_FORMAT "%s",
625 byte_size_in_proper_unit(HumongousThresholdBytes), proper_unit_for_byte_size(HumongousThresholdBytes));
626 log_info(gc, init)("Max TLAB size: " SIZE_FORMAT "%s",
627 byte_size_in_proper_unit(MaxTLABSizeBytes), proper_unit_for_byte_size(MaxTLABSizeBytes));
628 }
629
630 void ShenandoahHeapRegion::do_commit() {
631 if (!os::commit_memory((char *) _reserved.start(), _reserved.byte_size(), false)) {
632 report_java_out_of_memory("Unable to commit region");
633 }
634 if (!_heap->commit_bitmap_slice(this)) {
635 report_java_out_of_memory("Unable to commit bitmaps for region");
636 }
637 _heap->increase_committed(ShenandoahHeapRegion::region_size_bytes());
638 }
639
640 void ShenandoahHeapRegion::do_uncommit() {
641 if (!os::uncommit_memory((char *) _reserved.start(), _reserved.byte_size())) {
642 report_java_out_of_memory("Unable to uncommit region");
643 }
644 if (!_heap->uncommit_bitmap_slice(this)) {
645 report_java_out_of_memory("Unable to uncommit bitmaps for region");
646 }
647 _heap->decrease_committed(ShenandoahHeapRegion::region_size_bytes());
648 }