1 /*
2 * Copyright (c) 2011, 2015, 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/g1/g1CollectedHeap.inline.hpp"
27 #include "gc/g1/heapRegionRemSet.hpp"
28 #include "gc/g1/heapRegionSet.inline.hpp"
29
30 uint FreeRegionList::_unrealistically_long_length = 0;
31
32 #ifndef PRODUCT
33 void HeapRegionSetBase::verify_region(HeapRegion* hr) {
34 assert(hr->containing_set() == this, "Inconsistent containing set for %u", hr->hrm_index());
35 assert(!hr->is_young(), "Adding young region %u", hr->hrm_index()); // currently we don't use these sets for young regions
36 assert(hr->is_humongous() == regions_humongous(), "Wrong humongous state for region %u and set %s", hr->hrm_index(), name());
37 assert(hr->is_free() == regions_free(), "Wrong free state for region %u and set %s", hr->hrm_index(), name());
38 assert(!hr->is_free() || hr->is_empty(), "Free region %u is not empty for set %s", hr->hrm_index(), name());
39 assert(!hr->is_empty() || hr->is_free() || hr->is_archive(),
40 "Empty region %u is not free or archive for set %s", hr->hrm_index(), name());
41 assert(hr->rem_set()->verify_ready_for_par_iteration(), "Wrong iteration state %u", hr->hrm_index());
42 }
43 #endif
44
45 void HeapRegionSetBase::verify() {
46 // It's important that we also observe the MT safety protocol even
47 // for the verification calls. If we do verification without the
48 // appropriate locks and the set changes underneath our feet
49 // verification might fail and send us on a wild goose chase.
50 check_mt_safety();
51
52 guarantee_heap_region_set(( is_empty() && length() == 0) ||
53 (!is_empty() && length() > 0),
54 "invariant");
55 }
56
57 void HeapRegionSetBase::verify_start() {
58 // See comment in verify() about MT safety and verification.
59 check_mt_safety();
60 assert_heap_region_set(!_verify_in_progress, "verification should not be in progress");
61
62 // Do the basic verification first before we do the checks over the regions.
63 HeapRegionSetBase::verify();
64
65 _verify_in_progress = true;
66 }
67
68 void HeapRegionSetBase::verify_end() {
69 // See comment in verify() about MT safety and verification.
70 check_mt_safety();
71 assert_heap_region_set(_verify_in_progress, "verification should be in progress");
72
73 _verify_in_progress = false;
74 }
75
76 void HeapRegionSetBase::print_on(outputStream* out, bool print_contents) {
77 out->cr();
78 out->print_cr("Set: %s (" PTR_FORMAT ")", name(), p2i(this));
79 out->print_cr(" Region Assumptions");
80 out->print_cr(" humongous : %s", BOOL_TO_STR(regions_humongous()));
81 out->print_cr(" free : %s", BOOL_TO_STR(regions_free()));
82 out->print_cr(" Attributes");
83 out->print_cr(" length : %14u", length());
84 }
85
86 HeapRegionSetBase::HeapRegionSetBase(const char* name, bool humongous, bool free, HRSMtSafeChecker* mt_safety_checker)
87 : _name(name), _verify_in_progress(false),
88 _is_humongous(humongous), _is_free(free), _mt_safety_checker(mt_safety_checker),
89 _length(0)
90 { }
91
92 void FreeRegionList::set_unrealistically_long_length(uint len) {
93 guarantee(_unrealistically_long_length == 0, "should only be set once");
94 _unrealistically_long_length = len;
95 }
96
97 void FreeRegionList::remove_all() {
98 check_mt_safety();
99 verify_optional();
100
101 HeapRegion* curr = _head;
102 while (curr != NULL) {
103 verify_region(curr);
104
105 HeapRegion* next = curr->next();
106 curr->set_next(NULL);
107 curr->set_prev(NULL);
108 curr->set_containing_set(NULL);
109 curr = next;
110 }
111 clear();
112
113 verify_optional();
114 }
115
116 void FreeRegionList::add_ordered(FreeRegionList* from_list) {
117 check_mt_safety();
118 from_list->check_mt_safety();
119
120 verify_optional();
121 from_list->verify_optional();
122
123 if (from_list->is_empty()) {
124 return;
125 }
126
127 #ifdef ASSERT
128 FreeRegionListIterator iter(from_list);
129 while (iter.more_available()) {
130 HeapRegion* hr = iter.get_next();
131 // In set_containing_set() we check that we either set the value
132 // from NULL to non-NULL or vice versa to catch bugs. So, we have
133 // to NULL it first before setting it to the value.
134 hr->set_containing_set(NULL);
135 hr->set_containing_set(this);
136 }
137 #endif // ASSERT
138
139 if (is_empty()) {
140 assert_free_region_list(length() == 0 && _tail == NULL, "invariant");
141 _head = from_list->_head;
142 _tail = from_list->_tail;
143 } else {
144 HeapRegion* curr_to = _head;
145 HeapRegion* curr_from = from_list->_head;
146
147 while (curr_from != NULL) {
148 while (curr_to != NULL && curr_to->hrm_index() < curr_from->hrm_index()) {
149 curr_to = curr_to->next();
150 }
151
152 if (curr_to == NULL) {
153 // The rest of the from list should be added as tail
154 _tail->set_next(curr_from);
155 curr_from->set_prev(_tail);
156 curr_from = NULL;
157 } else {
158 HeapRegion* next_from = curr_from->next();
159
160 curr_from->set_next(curr_to);
161 curr_from->set_prev(curr_to->prev());
162 if (curr_to->prev() == NULL) {
163 _head = curr_from;
164 } else {
165 curr_to->prev()->set_next(curr_from);
166 }
167 curr_to->set_prev(curr_from);
168
169 curr_from = next_from;
170 }
171 }
172
173 if (_tail->hrm_index() < from_list->_tail->hrm_index()) {
174 _tail = from_list->_tail;
175 }
176 }
177
178 _length += from_list->length();
179 from_list->clear();
180
181 verify_optional();
182 from_list->verify_optional();
183 }
184
185 void FreeRegionList::remove_starting_at(HeapRegion* first, uint num_regions) {
186 check_mt_safety();
187 assert_free_region_list(num_regions >= 1, "pre-condition");
188 assert_free_region_list(!is_empty(), "pre-condition");
189
190 verify_optional();
191 DEBUG_ONLY(uint old_length = length();)
192
193 HeapRegion* curr = first;
194 uint count = 0;
195 while (count < num_regions) {
196 verify_region(curr);
197 HeapRegion* next = curr->next();
198 HeapRegion* prev = curr->prev();
199
200 assert(count < num_regions,
201 "[%s] should not come across more regions "
202 "pending for removal than num_regions: %u",
203 name(), num_regions);
204
205 if (prev == NULL) {
206 assert_free_region_list(_head == curr, "invariant");
207 _head = next;
208 } else {
209 assert_free_region_list(_head != curr, "invariant");
210 prev->set_next(next);
211 }
212 if (next == NULL) {
213 assert_free_region_list(_tail == curr, "invariant");
214 _tail = prev;
215 } else {
216 assert_free_region_list(_tail != curr, "invariant");
217 next->set_prev(prev);
218 }
219 if (_last == curr) {
220 _last = NULL;
221 }
222
223 curr->set_next(NULL);
224 curr->set_prev(NULL);
225 remove(curr);
226
227 count++;
228 curr = next;
229 }
230
231 assert(count == num_regions,
232 "[%s] count: %u should be == num_regions: %u",
233 name(), count, num_regions);
234 assert(length() + num_regions == old_length,
235 "[%s] new length should be consistent "
236 "new length: %u old length: %u num_regions: %u",
237 name(), length(), old_length, num_regions);
238
239 verify_optional();
240 }
241
242 void FreeRegionList::verify() {
243 // See comment in HeapRegionSetBase::verify() about MT safety and
244 // verification.
245 check_mt_safety();
246
247 // This will also do the basic verification too.
248 verify_start();
249
250 verify_list();
251
252 verify_end();
253 }
254
255 void FreeRegionList::clear() {
256 _length = 0;
257 _head = NULL;
258 _tail = NULL;
259 _last = NULL;
260 }
261
262 void FreeRegionList::verify_list() {
263 HeapRegion* curr = _head;
264 HeapRegion* prev1 = NULL;
265 HeapRegion* prev0 = NULL;
266 uint count = 0;
267 size_t capacity = 0;
268 uint last_index = 0;
269
270 guarantee(_head == NULL || _head->prev() == NULL, "_head should not have a prev");
271 while (curr != NULL) {
272 verify_region(curr);
273
274 count++;
275 guarantee(count < _unrealistically_long_length,
276 "[%s] the calculated length: %u seems very long, is there maybe a cycle? curr: " PTR_FORMAT " prev0: " PTR_FORMAT " " "prev1: " PTR_FORMAT " length: %u",
277 name(), count, p2i(curr), p2i(prev0), p2i(prev1), length());
278
279 if (curr->next() != NULL) {
280 guarantee(curr->next()->prev() == curr, "Next or prev pointers messed up");
281 }
282 guarantee(curr->hrm_index() == 0 || curr->hrm_index() > last_index, "List should be sorted");
283 last_index = curr->hrm_index();
284
285 capacity += curr->capacity();
286
287 prev1 = prev0;
288 prev0 = curr;
289 curr = curr->next();
290 }
291
292 guarantee(_tail == prev0, "Expected %s to end with %u but it ended with %u.", name(), _tail->hrm_index(), prev0->hrm_index());
293 guarantee(_tail == NULL || _tail->next() == NULL, "_tail should not have a next");
294 guarantee(length() == count, "%s count mismatch. Expected %u, actual %u.", name(), length(), count);
295 }
296
297 // Note on the check_mt_safety() methods below:
298 //
299 // Verification of the "master" heap region sets / lists that are
300 // maintained by G1CollectedHeap is always done during a STW pause and
301 // by the VM thread at the start / end of the pause. The standard
302 // verification methods all assert check_mt_safety(). This is
303 // important as it ensures that verification is done without
304 // concurrent updates taking place at the same time. It follows, that,
305 // for the "master" heap region sets / lists, the check_mt_safety()
306 // method should include the VM thread / STW case.
307
308 void MasterFreeRegionListMtSafeChecker::check() {
309 // Master Free List MT safety protocol:
310 // (a) If we're at a safepoint, operations on the master free list
311 // should be invoked by either the VM thread (which will serialize
312 // them) or by the GC workers while holding the
313 // FreeList_lock.
314 // (b) If we're not at a safepoint, operations on the master free
315 // list should be invoked while holding the Heap_lock.
316
317 if (SafepointSynchronize::is_at_safepoint()) {
318 guarantee(Thread::current()->is_VM_thread() ||
319 FreeList_lock->owned_by_self(), "master free list MT safety protocol at a safepoint");
320 } else {
321 guarantee(Heap_lock->owned_by_self(), "master free list MT safety protocol outside a safepoint");
322 }
323 }
324
325 void SecondaryFreeRegionListMtSafeChecker::check() {
326 // Secondary Free List MT safety protocol:
327 // Operations on the secondary free list should always be invoked
328 // while holding the SecondaryFreeList_lock.
329
330 guarantee(SecondaryFreeList_lock->owned_by_self(), "secondary free list MT safety protocol");
331 }
332
333 void OldRegionSetMtSafeChecker::check() {
334 // Master Old Set MT safety protocol:
335 // (a) If we're at a safepoint, operations on the master old set
336 // should be invoked:
337 // - by the VM thread (which will serialize them), or
338 // - by the GC workers while holding the FreeList_lock, if we're
339 // at a safepoint for an evacuation pause (this lock is taken
340 // anyway when an GC alloc region is retired so that a new one
341 // is allocated from the free list), or
342 // - by the GC workers while holding the OldSets_lock, if we're at a
343 // safepoint for a cleanup pause.
344 // (b) If we're not at a safepoint, operations on the master old set
345 // should be invoked while holding the Heap_lock.
346
347 if (SafepointSynchronize::is_at_safepoint()) {
348 guarantee(Thread::current()->is_VM_thread()
349 || FreeList_lock->owned_by_self() || OldSets_lock->owned_by_self(),
350 "master old set MT safety protocol at a safepoint");
351 } else {
352 guarantee(Heap_lock->owned_by_self(), "master old set MT safety protocol outside a safepoint");
353 }
354 }
355
356 void HumongousRegionSetMtSafeChecker::check() {
357 // Humongous Set MT safety protocol:
358 // (a) If we're at a safepoint, operations on the master humongous
359 // set should be invoked by either the VM thread (which will
360 // serialize them) or by the GC workers while holding the
361 // OldSets_lock.
362 // (b) If we're not at a safepoint, operations on the master
363 // humongous set should be invoked while holding the Heap_lock.
364
365 if (SafepointSynchronize::is_at_safepoint()) {
366 guarantee(Thread::current()->is_VM_thread() ||
367 OldSets_lock->owned_by_self(),
368 "master humongous set MT safety protocol at a safepoint");
369 } else {
370 guarantee(Heap_lock->owned_by_self(),
371 "master humongous set MT safety protocol outside a safepoint");
372 }
373 }
374
375 void FreeRegionList_test() {
376 FreeRegionList l("test");
377
378 const uint num_regions_in_test = 5;
379 // Create a fake heap. It does not need to be valid, as the HeapRegion constructor
380 // does not access it.
381 MemRegion heap(NULL, num_regions_in_test * HeapRegion::GrainWords);
382 // Allocate a fake BOT because the HeapRegion constructor initializes
383 // the BOT.
384 size_t bot_size = G1BlockOffsetTable::compute_size(heap.word_size());
385 HeapWord* bot_data = NEW_C_HEAP_ARRAY(HeapWord, bot_size, mtGC);
386 ReservedSpace bot_rs(G1BlockOffsetTable::compute_size(heap.word_size()));
387 G1RegionToSpaceMapper* bot_storage =
388 G1RegionToSpaceMapper::create_mapper(bot_rs,
389 bot_rs.size(),
390 os::vm_page_size(),
391 HeapRegion::GrainBytes,
392 G1BlockOffsetTable::N_bytes,
393 mtGC);
394 G1BlockOffsetTable bot(heap, bot_storage);
395 bot_storage->commit_regions(0, num_regions_in_test);
396
397 // Set up memory regions for the heap regions.
398 MemRegion mr0(heap.start(), HeapRegion::GrainWords);
399 MemRegion mr1(mr0.end(), HeapRegion::GrainWords);
400 MemRegion mr2(mr1.end(), HeapRegion::GrainWords);
401 MemRegion mr3(mr2.end(), HeapRegion::GrainWords);
402 MemRegion mr4(mr3.end(), HeapRegion::GrainWords);
403
404 HeapRegion hr0(0, &bot, mr0);
405 HeapRegion hr1(1, &bot, mr1);
406 HeapRegion hr2(2, &bot, mr2);
407 HeapRegion hr3(3, &bot, mr3);
408 HeapRegion hr4(4, &bot, mr4);
409 l.add_ordered(&hr1);
410 l.add_ordered(&hr0);
411 l.add_ordered(&hr3);
412 l.add_ordered(&hr4);
413 l.add_ordered(&hr2);
414 assert(l.length() == num_regions_in_test, "wrong length");
415 l.verify_list();
416
417 bot_storage->uncommit_regions(0, num_regions_in_test);
418 delete bot_storage;
419 FREE_C_HEAP_ARRAY(HeapWord, bot_data);
420 }