1 /*
2 * Copyright (c) 2013, 2019, Red Hat, Inc. All rights reserved.
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/shenandoah/shenandoahHeapRegionSet.inline.hpp"
27 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
28 #include "gc/shenandoah/shenandoahHeapRegion.hpp"
29 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
30 #include "gc/shenandoah/shenandoahTraversalGC.hpp"
31 #include "gc/shared/space.inline.hpp"
32 #include "memory/iterator.inline.hpp"
33 #include "memory/resourceArea.hpp"
34 #include "memory/universe.hpp"
35 #include "oops/oop.inline.hpp"
36 #include "runtime/java.hpp"
37 #include "runtime/mutexLocker.hpp"
38 #include "runtime/os.hpp"
39 #include "runtime/safepoint.hpp"
40
41 size_t ShenandoahHeapRegion::RegionCount = 0;
42 size_t ShenandoahHeapRegion::RegionSizeBytes = 0;
43 size_t ShenandoahHeapRegion::RegionSizeWords = 0;
44 size_t ShenandoahHeapRegion::RegionSizeBytesShift = 0;
45 size_t ShenandoahHeapRegion::RegionSizeWordsShift = 0;
46 size_t ShenandoahHeapRegion::RegionSizeBytesMask = 0;
47 size_t ShenandoahHeapRegion::RegionSizeWordsMask = 0;
48 size_t ShenandoahHeapRegion::HumongousThresholdBytes = 0;
49 size_t ShenandoahHeapRegion::HumongousThresholdWords = 0;
50 size_t ShenandoahHeapRegion::MaxTLABSizeBytes = 0;
51 size_t ShenandoahHeapRegion::MaxTLABSizeWords = 0;
52
53 ShenandoahHeapRegion::PaddedAllocSeqNum ShenandoahHeapRegion::_alloc_seq_num;
54
55 ShenandoahHeapRegion::ShenandoahHeapRegion(ShenandoahHeap* heap, HeapWord* start,
56 size_t size_words, size_t index, bool committed) :
57 _heap(heap),
58 _reserved(MemRegion(start, size_words)),
59 _region_number(index),
60 _new_top(NULL),
61 _critical_pins(0),
62 _empty_time(os::elapsedTime()),
63 _state(committed ? _empty_committed : _empty_uncommitted),
64 _tlab_allocs(0),
65 _gclab_allocs(0),
66 _shared_allocs(0),
67 _seqnum_first_alloc_mutator(0),
68 _seqnum_first_alloc_gc(0),
69 _seqnum_last_alloc_mutator(0),
70 _seqnum_last_alloc_gc(0),
71 _live_data(0) {
72
73 ContiguousSpace::initialize(_reserved, true, committed);
74 }
75
76 size_t ShenandoahHeapRegion::region_number() const {
77 return _region_number;
78 }
79
80 void ShenandoahHeapRegion::report_illegal_transition(const char *method) {
81 ResourceMark rm;
82 stringStream ss;
83 ss.print("Illegal region state transition from \"%s\", at %s\n ", region_state_to_string(_state), method);
84 print_on(&ss);
85 fatal("%s", ss.as_string());
86 }
87
88 void ShenandoahHeapRegion::make_regular_allocation() {
89 _heap->assert_heaplock_owned_by_current_thread();
90
91 switch (_state) {
92 case _empty_uncommitted:
93 do_commit();
94 case _empty_committed:
95 _state = _regular;
96 case _regular:
97 case _pinned:
98 return;
99 default:
100 report_illegal_transition("regular allocation");
101 }
102 }
103
104 void ShenandoahHeapRegion::make_regular_bypass() {
105 _heap->assert_heaplock_owned_by_current_thread();
106 assert (_heap->is_full_gc_in_progress() || _heap->is_degenerated_gc_in_progress(),
107 "only for full or degen GC");
108
109 switch (_state) {
110 case _empty_uncommitted:
111 do_commit();
112 case _empty_committed:
113 case _cset:
114 case _humongous_start:
115 case _humongous_cont:
116 _state = _regular;
117 return;
118 case _pinned_cset:
119 _state = _pinned;
120 return;
121 case _regular:
122 case _pinned:
123 return;
124 default:
125 report_illegal_transition("regular bypass");
126 }
127 }
128
129 void ShenandoahHeapRegion::make_humongous_start() {
130 _heap->assert_heaplock_owned_by_current_thread();
131 switch (_state) {
132 case _empty_uncommitted:
133 do_commit();
134 case _empty_committed:
135 _state = _humongous_start;
136 return;
137 default:
138 report_illegal_transition("humongous start allocation");
139 }
140 }
141
142 void ShenandoahHeapRegion::make_humongous_start_bypass() {
143 _heap->assert_heaplock_owned_by_current_thread();
144 assert (_heap->is_full_gc_in_progress(), "only for full GC");
145
146 switch (_state) {
147 case _empty_committed:
148 case _regular:
149 case _humongous_start:
150 case _humongous_cont:
151 _state = _humongous_start;
152 return;
153 default:
154 report_illegal_transition("humongous start bypass");
155 }
156 }
157
158 void ShenandoahHeapRegion::make_humongous_cont() {
159 _heap->assert_heaplock_owned_by_current_thread();
160 switch (_state) {
161 case _empty_uncommitted:
162 do_commit();
163 case _empty_committed:
164 _state = _humongous_cont;
165 return;
166 default:
167 report_illegal_transition("humongous continuation allocation");
168 }
169 }
170
171 void ShenandoahHeapRegion::make_humongous_cont_bypass() {
172 _heap->assert_heaplock_owned_by_current_thread();
173 assert (_heap->is_full_gc_in_progress(), "only for full GC");
174
175 switch (_state) {
176 case _empty_committed:
177 case _regular:
178 case _humongous_start:
179 case _humongous_cont:
180 _state = _humongous_cont;
181 return;
182 default:
183 report_illegal_transition("humongous continuation bypass");
184 }
185 }
186
187 void ShenandoahHeapRegion::make_pinned() {
188 _heap->assert_heaplock_owned_by_current_thread();
189 switch (_state) {
190 case _regular:
191 assert (_critical_pins == 0, "sanity");
192 _state = _pinned;
193 case _pinned_cset:
194 case _pinned:
195 _critical_pins++;
196 return;
197 case _humongous_start:
198 assert (_critical_pins == 0, "sanity");
199 _state = _pinned_humongous_start;
200 case _pinned_humongous_start:
201 _critical_pins++;
202 return;
203 case _cset:
204 guarantee(_heap->cancelled_gc(), "only valid when evac has been cancelled");
205 assert (_critical_pins == 0, "sanity");
206 _state = _pinned_cset;
207 _critical_pins++;
208 return;
209 default:
210 report_illegal_transition("pinning");
211 }
212 }
213
214 void ShenandoahHeapRegion::make_unpinned() {
215 _heap->assert_heaplock_owned_by_current_thread();
216 switch (_state) {
217 case _pinned:
218 assert (_critical_pins > 0, "sanity");
219 _critical_pins--;
220 if (_critical_pins == 0) {
221 _state = _regular;
222 }
223 return;
224 case _regular:
225 case _humongous_start:
226 assert (_critical_pins == 0, "sanity");
227 return;
228 case _pinned_cset:
229 guarantee(_heap->cancelled_gc(), "only valid when evac has been cancelled");
230 assert (_critical_pins > 0, "sanity");
231 _critical_pins--;
232 if (_critical_pins == 0) {
233 _state = _cset;
234 }
235 return;
236 case _pinned_humongous_start:
237 assert (_critical_pins > 0, "sanity");
238 _critical_pins--;
239 if (_critical_pins == 0) {
240 _state = _humongous_start;
241 }
242 return;
243 default:
244 report_illegal_transition("unpinning");
245 }
246 }
247
248 void ShenandoahHeapRegion::make_cset() {
249 _heap->assert_heaplock_owned_by_current_thread();
250 switch (_state) {
251 case _regular:
252 _state = _cset;
253 case _cset:
254 return;
255 default:
256 report_illegal_transition("cset");
257 }
258 }
259
260 void ShenandoahHeapRegion::make_trash() {
261 _heap->assert_heaplock_owned_by_current_thread();
262 switch (_state) {
263 case _cset:
264 // Reclaiming cset regions
265 case _humongous_start:
266 case _humongous_cont:
267 // Reclaiming humongous regions
268 case _regular:
269 // Immediate region reclaim
270 _state = _trash;
271 return;
272 default:
273 report_illegal_transition("trashing");
274 }
275 }
276
277 void ShenandoahHeapRegion::make_trash_immediate() {
278 make_trash();
279
280 // On this path, we know there are no marked objects in the region,
281 // tell marking context about it to bypass bitmap resets.
282 _heap->complete_marking_context()->reset_top_bitmap(this);
283 }
284
285 void ShenandoahHeapRegion::make_empty() {
286 _heap->assert_heaplock_owned_by_current_thread();
287 switch (_state) {
288 case _trash:
289 _state = _empty_committed;
290 _empty_time = os::elapsedTime();
291 return;
292 default:
293 report_illegal_transition("emptying");
294 }
295 }
296
297 void ShenandoahHeapRegion::make_uncommitted() {
298 _heap->assert_heaplock_owned_by_current_thread();
299 switch (_state) {
300 case _empty_committed:
301 do_uncommit();
302 _state = _empty_uncommitted;
303 return;
304 default:
305 report_illegal_transition("uncommiting");
306 }
307 }
308
309 void ShenandoahHeapRegion::make_committed_bypass() {
310 _heap->assert_heaplock_owned_by_current_thread();
311 assert (_heap->is_full_gc_in_progress(), "only for full GC");
312
313 switch (_state) {
314 case _empty_uncommitted:
315 do_commit();
316 _state = _empty_committed;
317 return;
318 default:
319 report_illegal_transition("commit bypass");
320 }
321 }
322
323 void ShenandoahHeapRegion::clear_live_data() {
324 OrderAccess::release_store_fence<size_t>(&_live_data, 0);
325 }
326
327 void ShenandoahHeapRegion::reset_alloc_metadata() {
328 _tlab_allocs = 0;
329 _gclab_allocs = 0;
330 _shared_allocs = 0;
331 _seqnum_first_alloc_mutator = 0;
332 _seqnum_last_alloc_mutator = 0;
333 _seqnum_first_alloc_gc = 0;
334 _seqnum_last_alloc_gc = 0;
335 }
336
337 void ShenandoahHeapRegion::reset_alloc_metadata_to_shared() {
338 if (used() > 0) {
339 _tlab_allocs = 0;
340 _gclab_allocs = 0;
341 _shared_allocs = used() >> LogHeapWordSize;
342 uint64_t next = _alloc_seq_num.value++;
343 _seqnum_first_alloc_mutator = next;
344 _seqnum_last_alloc_mutator = next;
345 _seqnum_first_alloc_gc = 0;
346 _seqnum_last_alloc_gc = 0;
347 } else {
348 reset_alloc_metadata();
349 }
350 }
351
352 size_t ShenandoahHeapRegion::get_shared_allocs() const {
353 return _shared_allocs * HeapWordSize;
354 }
355
356 size_t ShenandoahHeapRegion::get_tlab_allocs() const {
357 return _tlab_allocs * HeapWordSize;
358 }
359
360 size_t ShenandoahHeapRegion::get_gclab_allocs() const {
361 return _gclab_allocs * HeapWordSize;
362 }
363
364 void ShenandoahHeapRegion::set_live_data(size_t s) {
365 assert(Thread::current()->is_VM_thread(), "by VM thread");
366 _live_data = (s >> LogHeapWordSize);
367 }
368
369 size_t ShenandoahHeapRegion::get_live_data_words() const {
370 return OrderAccess::load_acquire(&_live_data);
371 }
372
373 size_t ShenandoahHeapRegion::get_live_data_bytes() const {
374 return get_live_data_words() * HeapWordSize;
375 }
376
377 bool ShenandoahHeapRegion::has_live() const {
378 return get_live_data_words() != 0;
379 }
380
381 size_t ShenandoahHeapRegion::garbage() const {
382 assert(used() >= get_live_data_bytes(), "Live Data must be a subset of used() live: " SIZE_FORMAT " used: " SIZE_FORMAT,
383 get_live_data_bytes(), used());
384
385 size_t result = used() - get_live_data_bytes();
386 return result;
387 }
388
389 void ShenandoahHeapRegion::print_on(outputStream* st) const {
390 st->print("|");
391 st->print(SIZE_FORMAT_W(5), this->_region_number);
392
393 switch (_state) {
394 case _empty_uncommitted:
395 st->print("|EU ");
396 break;
397 case _empty_committed:
398 st->print("|EC ");
399 break;
400 case _regular:
401 st->print("|R ");
402 break;
403 case _humongous_start:
404 st->print("|H ");
405 break;
406 case _pinned_humongous_start:
407 st->print("|HP ");
408 break;
409 case _humongous_cont:
410 st->print("|HC ");
411 break;
412 case _cset:
413 st->print("|CS ");
414 break;
415 case _trash:
416 st->print("|T ");
417 break;
418 case _pinned:
419 st->print("|P ");
420 break;
421 case _pinned_cset:
422 st->print("|CSP");
423 break;
424 default:
425 ShouldNotReachHere();
426 }
427 st->print("|BTE " INTPTR_FORMAT_W(12) ", " INTPTR_FORMAT_W(12) ", " INTPTR_FORMAT_W(12),
428 p2i(bottom()), p2i(top()), p2i(end()));
429 st->print("|TAMS " INTPTR_FORMAT_W(12),
430 p2i(_heap->marking_context()->top_at_mark_start(const_cast<ShenandoahHeapRegion*>(this))));
431 st->print("|U " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(used()), proper_unit_for_byte_size(used()));
432 st->print("|T " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(get_tlab_allocs()), proper_unit_for_byte_size(get_tlab_allocs()));
433 st->print("|G " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(get_gclab_allocs()), proper_unit_for_byte_size(get_gclab_allocs()));
434 st->print("|S " SIZE_FORMAT_W(5) "%1s", byte_size_in_proper_unit(get_shared_allocs()), proper_unit_for_byte_size(get_shared_allocs()));
435 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()));
436 st->print("|CP " SIZE_FORMAT_W(3), _critical_pins);
437 st->print("|SN " UINT64_FORMAT_X_W(12) ", " UINT64_FORMAT_X_W(8) ", " UINT64_FORMAT_X_W(8) ", " UINT64_FORMAT_X_W(8),
438 seqnum_first_alloc_mutator(), seqnum_last_alloc_mutator(),
439 seqnum_first_alloc_gc(), seqnum_last_alloc_gc());
440 st->cr();
441 }
442
443 void ShenandoahHeapRegion::oop_iterate(OopIterateClosure* blk) {
444 if (!is_active()) return;
445 if (is_humongous()) {
446 oop_iterate_humongous(blk);
447 } else {
448 oop_iterate_objects(blk);
449 }
450 }
451
452 void ShenandoahHeapRegion::oop_iterate_objects(OopIterateClosure* blk) {
453 assert(! is_humongous(), "no humongous region here");
454 HeapWord* obj_addr = bottom();
455 HeapWord* t = top();
456 // Could call objects iterate, but this is easier.
457 while (obj_addr < t) {
458 oop obj = oop(obj_addr);
459 obj_addr += obj->oop_iterate_size(blk);
460 }
461 }
462
463 void ShenandoahHeapRegion::oop_iterate_humongous(OopIterateClosure* blk) {
464 assert(is_humongous(), "only humongous region here");
465 // Find head.
466 ShenandoahHeapRegion* r = humongous_start_region();
467 assert(r->is_humongous_start(), "need humongous head here");
468 oop obj = oop(r->bottom());
469 obj->oop_iterate(blk, MemRegion(bottom(), top()));
470 }
471
472 ShenandoahHeapRegion* ShenandoahHeapRegion::humongous_start_region() const {
473 assert(is_humongous(), "Must be a part of the humongous region");
474 size_t reg_num = region_number();
475 ShenandoahHeapRegion* r = const_cast<ShenandoahHeapRegion*>(this);
476 while (!r->is_humongous_start()) {
477 assert(reg_num > 0, "Sanity");
478 reg_num --;
479 r = _heap->get_region(reg_num);
480 assert(r->is_humongous(), "Must be a part of the humongous region");
481 }
482 assert(r->is_humongous_start(), "Must be");
483 return r;
484 }
485
486 void ShenandoahHeapRegion::recycle() {
487 ContiguousSpace::clear(false);
488 if (ZapUnusedHeapArea) {
489 ContiguousSpace::mangle_unused_area_complete();
490 }
491 clear_live_data();
492
493 reset_alloc_metadata();
494
495 _heap->marking_context()->reset_top_at_mark_start(this);
496
497 make_empty();
498 }
499
500 HeapWord* ShenandoahHeapRegion::block_start_const(const void* p) const {
501 assert(MemRegion(bottom(), end()).contains(p),
502 "p (" PTR_FORMAT ") not in space [" PTR_FORMAT ", " PTR_FORMAT ")",
503 p2i(p), p2i(bottom()), p2i(end()));
504 if (p >= top()) {
505 return top();
506 } else {
507 HeapWord* last = bottom();
508 HeapWord* cur = last;
509 while (cur <= p) {
510 last = cur;
511 cur += oop(cur)->size();
512 }
513 shenandoah_assert_correct(NULL, oop(last));
514 return last;
515 }
516 }
517
518 void ShenandoahHeapRegion::setup_sizes(size_t initial_heap_size, size_t max_heap_size) {
519 // Absolute minimums we should not ever break.
520 static const size_t MIN_REGION_SIZE = 256*K;
521
522 if (FLAG_IS_DEFAULT(ShenandoahMinRegionSize)) {
523 FLAG_SET_DEFAULT(ShenandoahMinRegionSize, MIN_REGION_SIZE);
524 }
525
526 size_t region_size;
527 if (FLAG_IS_DEFAULT(ShenandoahHeapRegionSize)) {
528 if (ShenandoahMinRegionSize > initial_heap_size / MIN_NUM_REGIONS) {
529 err_msg message("Initial heap size (" SIZE_FORMAT "K) is too low to afford the minimum number "
530 "of regions (" SIZE_FORMAT ") of minimum region size (" SIZE_FORMAT "K).",
531 initial_heap_size/K, MIN_NUM_REGIONS, ShenandoahMinRegionSize/K);
532 vm_exit_during_initialization("Invalid -XX:ShenandoahMinRegionSize option", message);
533 }
534 if (ShenandoahMinRegionSize < MIN_REGION_SIZE) {
535 err_msg message("" SIZE_FORMAT "K should not be lower than minimum region size (" SIZE_FORMAT "K).",
536 ShenandoahMinRegionSize/K, MIN_REGION_SIZE/K);
537 vm_exit_during_initialization("Invalid -XX:ShenandoahMinRegionSize option", message);
538 }
539 if (ShenandoahMinRegionSize < MinTLABSize) {
540 err_msg message("" SIZE_FORMAT "K should not be lower than TLAB size size (" SIZE_FORMAT "K).",
541 ShenandoahMinRegionSize/K, MinTLABSize/K);
542 vm_exit_during_initialization("Invalid -XX:ShenandoahMinRegionSize option", message);
543 }
544 if (ShenandoahMaxRegionSize < MIN_REGION_SIZE) {
545 err_msg message("" SIZE_FORMAT "K should not be lower than min region size (" SIZE_FORMAT "K).",
546 ShenandoahMaxRegionSize/K, MIN_REGION_SIZE/K);
547 vm_exit_during_initialization("Invalid -XX:ShenandoahMaxRegionSize option", message);
548 }
549 if (ShenandoahMinRegionSize > ShenandoahMaxRegionSize) {
550 err_msg message("Minimum (" SIZE_FORMAT "K) should be larger than maximum (" SIZE_FORMAT "K).",
551 ShenandoahMinRegionSize/K, ShenandoahMaxRegionSize/K);
552 vm_exit_during_initialization("Invalid -XX:ShenandoahMinRegionSize or -XX:ShenandoahMaxRegionSize", message);
553 }
554
555 // We rapidly expand to max_heap_size in most scenarios, so that is the measure
556 // for usual heap sizes. Do not depend on initial_heap_size here.
557 region_size = max_heap_size / ShenandoahTargetNumRegions;
558
559 // Now make sure that we don't go over or under our limits.
560 region_size = MAX2(ShenandoahMinRegionSize, region_size);
561 region_size = MIN2(ShenandoahMaxRegionSize, region_size);
562
563 } else {
564 if (ShenandoahHeapRegionSize > initial_heap_size / MIN_NUM_REGIONS) {
565 err_msg message("Initial heap size (" SIZE_FORMAT "K) is too low to afford the minimum number "
566 "of regions (" SIZE_FORMAT ") of requested size (" SIZE_FORMAT "K).",
567 initial_heap_size/K, MIN_NUM_REGIONS, ShenandoahHeapRegionSize/K);
568 vm_exit_during_initialization("Invalid -XX:ShenandoahHeapRegionSize option", message);
569 }
570 if (ShenandoahHeapRegionSize < ShenandoahMinRegionSize) {
571 err_msg message("Heap region size (" SIZE_FORMAT "K) should be larger than min region size (" SIZE_FORMAT "K).",
572 ShenandoahHeapRegionSize/K, ShenandoahMinRegionSize/K);
573 vm_exit_during_initialization("Invalid -XX:ShenandoahHeapRegionSize option", message);
574 }
575 if (ShenandoahHeapRegionSize > ShenandoahMaxRegionSize) {
576 err_msg message("Heap region size (" SIZE_FORMAT "K) should be lower than max region size (" SIZE_FORMAT "K).",
577 ShenandoahHeapRegionSize/K, ShenandoahMaxRegionSize/K);
578 vm_exit_during_initialization("Invalid -XX:ShenandoahHeapRegionSize option", message);
579 }
580 region_size = ShenandoahHeapRegionSize;
581 }
582
583 // Make sure region size is at least one large page, if enabled.
584 // Otherwise, uncommitting one region may falsely uncommit the adjacent
585 // regions too.
586 // Also see shenandoahArguments.cpp, where it handles UseLargePages.
587 if (UseLargePages && ShenandoahUncommit) {
588 region_size = MAX2(region_size, os::large_page_size());
589 }
590
591 int region_size_log = log2_long((jlong) region_size);
592 // Recalculate the region size to make sure it's a power of
593 // 2. This means that region_size is the largest power of 2 that's
594 // <= what we've calculated so far.
595 region_size = size_t(1) << region_size_log;
596
597 // Now, set up the globals.
598 guarantee(RegionSizeBytesShift == 0, "we should only set it once");
599 RegionSizeBytesShift = (size_t)region_size_log;
600
601 guarantee(RegionSizeWordsShift == 0, "we should only set it once");
602 RegionSizeWordsShift = RegionSizeBytesShift - LogHeapWordSize;
603
604 guarantee(RegionSizeBytes == 0, "we should only set it once");
605 RegionSizeBytes = region_size;
606 RegionSizeWords = RegionSizeBytes >> LogHeapWordSize;
607 assert (RegionSizeWords*HeapWordSize == RegionSizeBytes, "sanity");
608
609 guarantee(RegionSizeWordsMask == 0, "we should only set it once");
610 RegionSizeWordsMask = RegionSizeWords - 1;
611
612 guarantee(RegionSizeBytesMask == 0, "we should only set it once");
613 RegionSizeBytesMask = RegionSizeBytes - 1;
614
615 guarantee(RegionCount == 0, "we should only set it once");
616 RegionCount = max_heap_size / RegionSizeBytes;
617 guarantee(RegionCount >= MIN_NUM_REGIONS, "Should have at least minimum regions");
618
619 guarantee(HumongousThresholdWords == 0, "we should only set it once");
620 HumongousThresholdWords = RegionSizeWords * ShenandoahHumongousThreshold / 100;
621 assert (HumongousThresholdWords <= RegionSizeWords, "sanity");
622
623 guarantee(HumongousThresholdBytes == 0, "we should only set it once");
624 HumongousThresholdBytes = HumongousThresholdWords * HeapWordSize;
625 assert (HumongousThresholdBytes <= RegionSizeBytes, "sanity");
626
627 // The rationale for trimming the TLAB sizes has to do with the raciness in
628 // TLAB allocation machinery. It may happen that TLAB sizing policy polls Shenandoah
629 // about next free size, gets the answer for region #N, goes away for a while, then
630 // tries to allocate in region #N, and fail because some other thread have claimed part
631 // of the region #N, and then the freeset allocation code has to retire the region #N,
632 // before moving the allocation to region #N+1.
633 //
634 // The worst case realizes when "answer" is "region size", which means it could
635 // prematurely retire an entire region. Having smaller TLABs does not fix that
636 // completely, but reduces the probability of too wasteful region retirement.
637 // With current divisor, we will waste no more than 1/8 of region size in the worst
638 // case. This also has a secondary effect on collection set selection: even under
639 // the race, the regions would be at least 7/8 used, which allows relying on
640 // "used" - "live" for cset selection. Otherwise, we can get the fragmented region
641 // below the garbage threshold that would never be considered for collection.
642 //
643 // The whole thing is mitigated if Elastic TLABs are enabled.
644 //
645 guarantee(MaxTLABSizeBytes == 0, "we should only set it once");
646 MaxTLABSizeBytes = MIN2(ShenandoahElasticTLAB ? RegionSizeBytes : (RegionSizeBytes / 8), HumongousThresholdBytes);
647 assert (MaxTLABSizeBytes > MinTLABSize, "should be larger");
648
649 guarantee(MaxTLABSizeWords == 0, "we should only set it once");
650 MaxTLABSizeWords = MaxTLABSizeBytes / HeapWordSize;
651
652 log_info(gc, init)("Regions: " SIZE_FORMAT " x " SIZE_FORMAT "%s",
653 RegionCount, byte_size_in_proper_unit(RegionSizeBytes), proper_unit_for_byte_size(RegionSizeBytes));
654 log_info(gc, init)("Humongous object threshold: " SIZE_FORMAT "%s",
655 byte_size_in_proper_unit(HumongousThresholdBytes), proper_unit_for_byte_size(HumongousThresholdBytes));
656 log_info(gc, init)("Max TLAB size: " SIZE_FORMAT "%s",
657 byte_size_in_proper_unit(MaxTLABSizeBytes), proper_unit_for_byte_size(MaxTLABSizeBytes));
658 }
659
660 void ShenandoahHeapRegion::do_commit() {
661 if (!_heap->is_heap_region_special() && !os::commit_memory((char *) _reserved.start(), _reserved.byte_size(), false)) {
662 report_java_out_of_memory("Unable to commit region");
663 }
664 if (!_heap->commit_bitmap_slice(this)) {
665 report_java_out_of_memory("Unable to commit bitmaps for region");
666 }
667 _heap->increase_committed(ShenandoahHeapRegion::region_size_bytes());
668 }
669
670 void ShenandoahHeapRegion::do_uncommit() {
671 if (!_heap->is_heap_region_special() && !os::uncommit_memory((char *) _reserved.start(), _reserved.byte_size())) {
672 report_java_out_of_memory("Unable to uncommit region");
673 }
674 if (!_heap->uncommit_bitmap_slice(this)) {
675 report_java_out_of_memory("Unable to uncommit bitmaps for region");
676 }
677 _heap->decrease_committed(ShenandoahHeapRegion::region_size_bytes());
678 }