Thu, 21 Aug 2014 16:44:41 +0200
8055098: WB API should be extended to provide information about size and age of object.
Summary: Extend the WhiteBox API to provide information about the size and age of objects. Further add a mechanism to trigger a young GC.
Reviewed-by: tschatzl, sjohanss
Contributed-by: Leonid Mesnik <leonid.mesnik@oracle.com>
1 /*
2 * Copyright (c) 2011, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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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).
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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23 */
25 #include "precompiled.hpp"
26 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
27 #include "gc_implementation/g1/heapRegionRemSet.hpp"
28 #include "gc_implementation/g1/heapRegionSet.inline.hpp"
30 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
32 uint FreeRegionList::_unrealistically_long_length = 0;
34 void HeapRegionSetBase::fill_in_ext_msg(hrs_ext_msg* msg, const char* message) {
35 msg->append("[%s] %s ln: %u cy: "SIZE_FORMAT,
36 name(), message, length(), total_capacity_bytes());
37 fill_in_ext_msg_extra(msg);
38 }
40 #ifndef PRODUCT
41 void HeapRegionSetBase::verify_region(HeapRegion* hr) {
42 assert(hr->containing_set() == this, err_msg("Inconsistent containing set for %u", hr->hrs_index()));
43 assert(!hr->is_young(), err_msg("Adding young region %u", hr->hrs_index())); // currently we don't use these sets for young regions
44 assert(hr->isHumongous() == regions_humongous(), err_msg("Wrong humongous state for region %u and set %s", hr->hrs_index(), name()));
45 assert(hr->is_empty() == regions_empty(), err_msg("Wrong empty state for region %u and set %s", hr->hrs_index(), name()));
46 assert(hr->rem_set()->verify_ready_for_par_iteration(), err_msg("Wrong iteration state %u", hr->hrs_index()));
47 }
48 #endif
50 void HeapRegionSetBase::verify() {
51 // It's important that we also observe the MT safety protocol even
52 // for the verification calls. If we do verification without the
53 // appropriate locks and the set changes underneath our feet
54 // verification might fail and send us on a wild goose chase.
55 check_mt_safety();
57 guarantee(( is_empty() && length() == 0 && total_capacity_bytes() == 0) ||
58 (!is_empty() && length() >= 0 && total_capacity_bytes() >= 0),
59 hrs_ext_msg(this, "invariant"));
60 }
62 void HeapRegionSetBase::verify_start() {
63 // See comment in verify() about MT safety and verification.
64 check_mt_safety();
65 assert(!_verify_in_progress,
66 hrs_ext_msg(this, "verification should not be in progress"));
68 // Do the basic verification first before we do the checks over the regions.
69 HeapRegionSetBase::verify();
71 _verify_in_progress = true;
72 }
74 void HeapRegionSetBase::verify_end() {
75 // See comment in verify() about MT safety and verification.
76 check_mt_safety();
77 assert(_verify_in_progress,
78 hrs_ext_msg(this, "verification should be in progress"));
80 _verify_in_progress = false;
81 }
83 void HeapRegionSetBase::print_on(outputStream* out, bool print_contents) {
84 out->cr();
85 out->print_cr("Set: %s ("PTR_FORMAT")", name(), this);
86 out->print_cr(" Region Assumptions");
87 out->print_cr(" humongous : %s", BOOL_TO_STR(regions_humongous()));
88 out->print_cr(" empty : %s", BOOL_TO_STR(regions_empty()));
89 out->print_cr(" Attributes");
90 out->print_cr(" length : %14u", length());
91 out->print_cr(" total capacity : "SIZE_FORMAT_W(14)" bytes",
92 total_capacity_bytes());
93 }
95 HeapRegionSetBase::HeapRegionSetBase(const char* name, bool humongous, bool empty, HRSMtSafeChecker* mt_safety_checker)
96 : _name(name), _verify_in_progress(false),
97 _is_humongous(humongous), _is_empty(empty), _mt_safety_checker(mt_safety_checker),
98 _count()
99 { }
101 void FreeRegionList::set_unrealistically_long_length(uint len) {
102 guarantee(_unrealistically_long_length == 0, "should only be set once");
103 _unrealistically_long_length = len;
104 }
106 void FreeRegionList::fill_in_ext_msg_extra(hrs_ext_msg* msg) {
107 msg->append(" hd: "PTR_FORMAT" tl: "PTR_FORMAT, _head, _tail);
108 }
110 void FreeRegionList::remove_all() {
111 check_mt_safety();
112 verify_optional();
114 HeapRegion* curr = _head;
115 while (curr != NULL) {
116 verify_region(curr);
118 HeapRegion* next = curr->next();
119 curr->set_next(NULL);
120 curr->set_prev(NULL);
121 curr->set_containing_set(NULL);
122 curr = next;
123 }
124 clear();
126 verify_optional();
127 }
129 void FreeRegionList::add_ordered(FreeRegionList* from_list) {
130 check_mt_safety();
131 from_list->check_mt_safety();
133 verify_optional();
134 from_list->verify_optional();
136 if (from_list->is_empty()) {
137 return;
138 }
140 #ifdef ASSERT
141 FreeRegionListIterator iter(from_list);
142 while (iter.more_available()) {
143 HeapRegion* hr = iter.get_next();
144 // In set_containing_set() we check that we either set the value
145 // from NULL to non-NULL or vice versa to catch bugs. So, we have
146 // to NULL it first before setting it to the value.
147 hr->set_containing_set(NULL);
148 hr->set_containing_set(this);
149 }
150 #endif // ASSERT
152 if (is_empty()) {
153 assert(length() == 0 && _tail == NULL, hrs_ext_msg(this, "invariant"));
154 _head = from_list->_head;
155 _tail = from_list->_tail;
156 } else {
157 HeapRegion* curr_to = _head;
158 HeapRegion* curr_from = from_list->_head;
160 while (curr_from != NULL) {
161 while (curr_to != NULL && curr_to->hrs_index() < curr_from->hrs_index()) {
162 curr_to = curr_to->next();
163 }
165 if (curr_to == NULL) {
166 // The rest of the from list should be added as tail
167 _tail->set_next(curr_from);
168 curr_from->set_prev(_tail);
169 curr_from = NULL;
170 } else {
171 HeapRegion* next_from = curr_from->next();
173 curr_from->set_next(curr_to);
174 curr_from->set_prev(curr_to->prev());
175 if (curr_to->prev() == NULL) {
176 _head = curr_from;
177 } else {
178 curr_to->prev()->set_next(curr_from);
179 }
180 curr_to->set_prev(curr_from);
182 curr_from = next_from;
183 }
184 }
186 if (_tail->hrs_index() < from_list->_tail->hrs_index()) {
187 _tail = from_list->_tail;
188 }
189 }
191 _count.increment(from_list->length(), from_list->total_capacity_bytes());
192 from_list->clear();
194 verify_optional();
195 from_list->verify_optional();
196 }
198 void FreeRegionList::remove_starting_at(HeapRegion* first, uint num_regions) {
199 check_mt_safety();
200 assert(num_regions >= 1, hrs_ext_msg(this, "pre-condition"));
201 assert(!is_empty(), hrs_ext_msg(this, "pre-condition"));
203 verify_optional();
204 DEBUG_ONLY(uint old_length = length();)
206 HeapRegion* curr = first;
207 uint count = 0;
208 while (count < num_regions) {
209 verify_region(curr);
210 HeapRegion* next = curr->next();
211 HeapRegion* prev = curr->prev();
213 assert(count < num_regions,
214 hrs_err_msg("[%s] should not come across more regions "
215 "pending for removal than num_regions: %u",
216 name(), num_regions));
218 if (prev == NULL) {
219 assert(_head == curr, hrs_ext_msg(this, "invariant"));
220 _head = next;
221 } else {
222 assert(_head != curr, hrs_ext_msg(this, "invariant"));
223 prev->set_next(next);
224 }
225 if (next == NULL) {
226 assert(_tail == curr, hrs_ext_msg(this, "invariant"));
227 _tail = prev;
228 } else {
229 assert(_tail != curr, hrs_ext_msg(this, "invariant"));
230 next->set_prev(prev);
231 }
232 if (_last = curr) {
233 _last = NULL;
234 }
236 curr->set_next(NULL);
237 curr->set_prev(NULL);
238 remove(curr);
240 count++;
241 curr = next;
242 }
244 assert(count == num_regions,
245 hrs_err_msg("[%s] count: %u should be == num_regions: %u",
246 name(), count, num_regions));
247 assert(length() + num_regions == old_length,
248 hrs_err_msg("[%s] new length should be consistent "
249 "new length: %u old length: %u num_regions: %u",
250 name(), length(), old_length, num_regions));
252 verify_optional();
253 }
255 void FreeRegionList::verify() {
256 // See comment in HeapRegionSetBase::verify() about MT safety and
257 // verification.
258 check_mt_safety();
260 // This will also do the basic verification too.
261 verify_start();
263 verify_list();
265 verify_end();
266 }
268 void FreeRegionList::clear() {
269 _count = HeapRegionSetCount();
270 _head = NULL;
271 _tail = NULL;
272 _last = NULL;
273 }
275 void FreeRegionList::print_on(outputStream* out, bool print_contents) {
276 HeapRegionSetBase::print_on(out, print_contents);
277 out->print_cr(" Linking");
278 out->print_cr(" head : "PTR_FORMAT, _head);
279 out->print_cr(" tail : "PTR_FORMAT, _tail);
281 if (print_contents) {
282 out->print_cr(" Contents");
283 FreeRegionListIterator iter(this);
284 while (iter.more_available()) {
285 HeapRegion* hr = iter.get_next();
286 hr->print_on(out);
287 }
288 }
290 out->cr();
291 }
293 void FreeRegionList::verify_list() {
294 HeapRegion* curr = _head;
295 HeapRegion* prev1 = NULL;
296 HeapRegion* prev0 = NULL;
297 uint count = 0;
298 size_t capacity = 0;
299 uint last_index = 0;
301 guarantee(_head == NULL || _head->prev() == NULL, "_head should not have a prev");
302 while (curr != NULL) {
303 verify_region(curr);
305 count++;
306 guarantee(count < _unrealistically_long_length,
307 hrs_err_msg("[%s] the calculated length: %u seems very long, is there maybe a cycle? curr: "PTR_FORMAT" prev0: "PTR_FORMAT" " "prev1: "PTR_FORMAT" length: %u", name(), count, curr, prev0, prev1, length()));
309 if (curr->next() != NULL) {
310 guarantee(curr->next()->prev() == curr, "Next or prev pointers messed up");
311 }
312 guarantee(curr->hrs_index() == 0 || curr->hrs_index() > last_index, "List should be sorted");
313 last_index = curr->hrs_index();
315 capacity += curr->capacity();
317 prev1 = prev0;
318 prev0 = curr;
319 curr = curr->next();
320 }
322 guarantee(_tail == prev0, err_msg("Expected %s to end with %u but it ended with %u.", name(), _tail->hrs_index(), prev0->hrs_index()));
323 guarantee(_tail == NULL || _tail->next() == NULL, "_tail should not have a next");
324 guarantee(length() == count, err_msg("%s count mismatch. Expected %u, actual %u.", name(), length(), count));
325 guarantee(total_capacity_bytes() == capacity, err_msg("%s capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
326 name(), total_capacity_bytes(), capacity));
327 }
329 // Note on the check_mt_safety() methods below:
330 //
331 // Verification of the "master" heap region sets / lists that are
332 // maintained by G1CollectedHeap is always done during a STW pause and
333 // by the VM thread at the start / end of the pause. The standard
334 // verification methods all assert check_mt_safety(). This is
335 // important as it ensures that verification is done without
336 // concurrent updates taking place at the same time. It follows, that,
337 // for the "master" heap region sets / lists, the check_mt_safety()
338 // method should include the VM thread / STW case.
340 void MasterFreeRegionListMtSafeChecker::check() {
341 // Master Free List MT safety protocol:
342 // (a) If we're at a safepoint, operations on the master free list
343 // should be invoked by either the VM thread (which will serialize
344 // them) or by the GC workers while holding the
345 // FreeList_lock.
346 // (b) If we're not at a safepoint, operations on the master free
347 // list should be invoked while holding the Heap_lock.
349 if (SafepointSynchronize::is_at_safepoint()) {
350 guarantee(Thread::current()->is_VM_thread() ||
351 FreeList_lock->owned_by_self(), "master free list MT safety protocol at a safepoint");
352 } else {
353 guarantee(Heap_lock->owned_by_self(), "master free list MT safety protocol outside a safepoint");
354 }
355 }
357 void SecondaryFreeRegionListMtSafeChecker::check() {
358 // Secondary Free List MT safety protocol:
359 // Operations on the secondary free list should always be invoked
360 // while holding the SecondaryFreeList_lock.
362 guarantee(SecondaryFreeList_lock->owned_by_self(), "secondary free list MT safety protocol");
363 }
365 void OldRegionSetMtSafeChecker::check() {
366 // Master Old Set MT safety protocol:
367 // (a) If we're at a safepoint, operations on the master old set
368 // should be invoked:
369 // - by the VM thread (which will serialize them), or
370 // - by the GC workers while holding the FreeList_lock, if we're
371 // at a safepoint for an evacuation pause (this lock is taken
372 // anyway when an GC alloc region is retired so that a new one
373 // is allocated from the free list), or
374 // - by the GC workers while holding the OldSets_lock, if we're at a
375 // safepoint for a cleanup pause.
376 // (b) If we're not at a safepoint, operations on the master old set
377 // should be invoked while holding the Heap_lock.
379 if (SafepointSynchronize::is_at_safepoint()) {
380 guarantee(Thread::current()->is_VM_thread()
381 || FreeList_lock->owned_by_self() || OldSets_lock->owned_by_self(),
382 "master old set MT safety protocol at a safepoint");
383 } else {
384 guarantee(Heap_lock->owned_by_self(), "master old set MT safety protocol outside a safepoint");
385 }
386 }
388 void HumongousRegionSetMtSafeChecker::check() {
389 // Humongous Set MT safety protocol:
390 // (a) If we're at a safepoint, operations on the master humongous
391 // set should be invoked by either the VM thread (which will
392 // serialize them) or by the GC workers while holding the
393 // OldSets_lock.
394 // (b) If we're not at a safepoint, operations on the master
395 // humongous set should be invoked while holding the Heap_lock.
397 if (SafepointSynchronize::is_at_safepoint()) {
398 guarantee(Thread::current()->is_VM_thread() ||
399 OldSets_lock->owned_by_self(),
400 "master humongous set MT safety protocol at a safepoint");
401 } else {
402 guarantee(Heap_lock->owned_by_self(),
403 "master humongous set MT safety protocol outside a safepoint");
404 }
405 }
407 void FreeRegionList_test() {
408 FreeRegionList l("test");
410 const uint num_regions_in_test = 5;
411 // Create a fake heap. It does not need to be valid, as the HeapRegion constructor
412 // does not access it.
413 MemRegion heap(NULL, num_regions_in_test * HeapRegion::GrainWords);
414 // Allocate a fake BOT because the HeapRegion constructor initializes
415 // the BOT.
416 size_t bot_size = G1BlockOffsetSharedArray::compute_size(heap.word_size());
417 HeapWord* bot_data = NEW_C_HEAP_ARRAY(HeapWord, bot_size, mtGC);
418 ReservedSpace bot_rs(G1BlockOffsetSharedArray::compute_size(heap.word_size()));
419 G1RegionToSpaceMapper* bot_storage =
420 G1RegionToSpaceMapper::create_mapper(bot_rs,
421 os::vm_page_size(),
422 HeapRegion::GrainBytes,
423 G1BlockOffsetSharedArray::N_bytes,
424 mtGC);
425 G1BlockOffsetSharedArray oa(heap, bot_storage);
426 bot_storage->commit_regions(0, num_regions_in_test);
427 HeapRegion hr0(0, &oa, heap);
428 HeapRegion hr1(1, &oa, heap);
429 HeapRegion hr2(2, &oa, heap);
430 HeapRegion hr3(3, &oa, heap);
431 HeapRegion hr4(4, &oa, heap);
432 l.add_ordered(&hr1);
433 l.add_ordered(&hr0);
434 l.add_ordered(&hr3);
435 l.add_ordered(&hr4);
436 l.add_ordered(&hr2);
437 assert(l.length() == num_regions_in_test, "wrong length");
438 l.verify_list();
440 bot_storage->uncommit_regions(0, num_regions_in_test);
441 delete bot_storage;
442 FREE_C_HEAP_ARRAY(HeapWord, bot_data, mtGC);
443 }