1 /*
2 * Copyright (c) 2001, 2010, 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 "classfile/systemDictionary.hpp"
27 #include "gc_implementation/shared/vmGCOperations.hpp"
28 #include "gc_interface/collectedHeap.hpp"
29 #include "gc_interface/collectedHeap.inline.hpp"
30 #include "oops/oop.inline.hpp"
31 #include "runtime/init.hpp"
32 #include "services/heapDumper.hpp"
33 #ifdef TARGET_OS_FAMILY_linux
34 # include "thread_linux.inline.hpp"
35 #endif
36 #ifdef TARGET_OS_FAMILY_solaris
37 # include "thread_solaris.inline.hpp"
38 #endif
39 #ifdef TARGET_OS_FAMILY_windows
40 # include "thread_windows.inline.hpp"
41 #endif
42
43
44 #ifdef ASSERT
45 int CollectedHeap::_fire_out_of_memory_count = 0;
46 #endif
47
48 size_t CollectedHeap::_filler_array_max_size = 0;
49
50 // Memory state functions.
51
52
53 CollectedHeap::CollectedHeap() : _n_par_threads(0)
54
55 {
56 const size_t max_len = size_t(arrayOopDesc::max_array_length(T_INT));
57 const size_t elements_per_word = HeapWordSize / sizeof(jint);
58 _filler_array_max_size = align_object_size(filler_array_hdr_size() +
59 max_len * elements_per_word);
60
61 _barrier_set = NULL;
62 _is_gc_active = false;
63 _total_collections = _total_full_collections = 0;
64 _gc_cause = _gc_lastcause = GCCause::_no_gc;
65 NOT_PRODUCT(_promotion_failure_alot_count = 0;)
66 NOT_PRODUCT(_promotion_failure_alot_gc_number = 0;)
67
68 if (UsePerfData) {
69 EXCEPTION_MARK;
70
71 // create the gc cause jvmstat counters
72 _perf_gc_cause = PerfDataManager::create_string_variable(SUN_GC, "cause",
73 80, GCCause::to_string(_gc_cause), CHECK);
74
75 _perf_gc_lastcause =
76 PerfDataManager::create_string_variable(SUN_GC, "lastCause",
77 80, GCCause::to_string(_gc_lastcause), CHECK);
78 }
79 _defer_initial_card_mark = false; // strengthened by subclass in pre_initialize() below.
80 }
81
82 void CollectedHeap::pre_initialize() {
83 // Used for ReduceInitialCardMarks (when COMPILER2 is used);
84 // otherwise remains unused.
85 #ifdef COMPILER2
86 _defer_initial_card_mark = ReduceInitialCardMarks && can_elide_tlab_store_barriers()
87 && (DeferInitialCardMark || card_mark_must_follow_store());
88 #else
89 assert(_defer_initial_card_mark == false, "Who would set it?");
90 #endif
91 }
92
93 #ifndef PRODUCT
94 void CollectedHeap::check_for_bad_heap_word_value(HeapWord* addr, size_t size) {
95 if (CheckMemoryInitialization && ZapUnusedHeapArea) {
96 for (size_t slot = 0; slot < size; slot += 1) {
97 assert((*(intptr_t*) (addr + slot)) != ((intptr_t) badHeapWordVal),
98 "Found badHeapWordValue in post-allocation check");
99 }
100 }
101 }
102
103 void CollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr, size_t size)
104 {
105 if (CheckMemoryInitialization && ZapUnusedHeapArea) {
106 for (size_t slot = 0; slot < size; slot += 1) {
107 assert((*(intptr_t*) (addr + slot)) == ((intptr_t) badHeapWordVal),
108 "Found non badHeapWordValue in pre-allocation check");
109 }
110 }
111 }
112 #endif // PRODUCT
113
114 #ifdef ASSERT
115 void CollectedHeap::check_for_valid_allocation_state() {
116 Thread *thread = Thread::current();
117 // How to choose between a pending exception and a potential
118 // OutOfMemoryError? Don't allow pending exceptions.
119 // This is a VM policy failure, so how do we exhaustively test it?
120 assert(!thread->has_pending_exception(),
121 "shouldn't be allocating with pending exception");
122 if (StrictSafepointChecks) {
123 assert(thread->allow_allocation(),
124 "Allocation done by thread for which allocation is blocked "
125 "by No_Allocation_Verifier!");
126 // Allocation of an oop can always invoke a safepoint,
127 // hence, the true argument
128 thread->check_for_valid_safepoint_state(true);
129 }
130 }
131 #endif
132
133 HeapWord* CollectedHeap::allocate_from_tlab_slow(Thread* thread, size_t size) {
134
135 // Retain tlab and allocate object in shared space if
136 // the amount free in the tlab is too large to discard.
137 if (thread->tlab().free() > thread->tlab().refill_waste_limit()) {
138 thread->tlab().record_slow_allocation(size);
139 return NULL;
140 }
141
142 // Discard tlab and allocate a new one.
143 // To minimize fragmentation, the last TLAB may be smaller than the rest.
144 size_t new_tlab_size = thread->tlab().compute_size(size);
145
146 thread->tlab().clear_before_allocation();
147
148 if (new_tlab_size == 0) {
149 return NULL;
150 }
151
152 // Allocate a new TLAB...
153 HeapWord* obj = Universe::heap()->allocate_new_tlab(new_tlab_size);
154 if (obj == NULL) {
155 return NULL;
156 }
157 if (ZeroTLAB) {
158 // ..and clear it.
159 Copy::zero_to_words(obj, new_tlab_size);
160 } else {
161 // ...and clear just the allocated object.
162 Copy::zero_to_words(obj, size);
163 }
164 thread->tlab().fill(obj, obj + size, new_tlab_size);
165 return obj;
166 }
167
168 void CollectedHeap::flush_deferred_store_barrier(JavaThread* thread) {
169 MemRegion deferred = thread->deferred_card_mark();
170 if (!deferred.is_empty()) {
171 assert(_defer_initial_card_mark, "Otherwise should be empty");
172 {
173 // Verify that the storage points to a parsable object in heap
174 DEBUG_ONLY(oop old_obj = oop(deferred.start());)
175 assert(is_in(old_obj), "Not in allocated heap");
176 assert(!can_elide_initializing_store_barrier(old_obj),
177 "Else should have been filtered in new_store_pre_barrier()");
178 assert(!is_in_permanent(old_obj), "Sanity: not expected");
179 assert(old_obj->is_oop(true), "Not an oop");
180 assert(old_obj->is_parsable(), "Will not be concurrently parsable");
181 assert(deferred.word_size() == (size_t)(old_obj->size()),
182 "Mismatch: multiple objects?");
183 }
184 BarrierSet* bs = barrier_set();
185 assert(bs->has_write_region_opt(), "No write_region() on BarrierSet");
186 bs->write_region(deferred);
187 // "Clear" the deferred_card_mark field
188 thread->set_deferred_card_mark(MemRegion());
189 }
190 assert(thread->deferred_card_mark().is_empty(), "invariant");
191 }
192
193 // Helper for ReduceInitialCardMarks. For performance,
194 // compiled code may elide card-marks for initializing stores
195 // to a newly allocated object along the fast-path. We
196 // compensate for such elided card-marks as follows:
197 // (a) Generational, non-concurrent collectors, such as
198 // GenCollectedHeap(ParNew,DefNew,Tenured) and
199 // ParallelScavengeHeap(ParallelGC, ParallelOldGC)
200 // need the card-mark if and only if the region is
201 // in the old gen, and do not care if the card-mark
202 // succeeds or precedes the initializing stores themselves,
203 // so long as the card-mark is completed before the next
204 // scavenge. For all these cases, we can do a card mark
205 // at the point at which we do a slow path allocation
206 // in the old gen, i.e. in this call.
207 // (b) GenCollectedHeap(ConcurrentMarkSweepGeneration) requires
208 // in addition that the card-mark for an old gen allocated
209 // object strictly follow any associated initializing stores.
210 // In these cases, the memRegion remembered below is
211 // used to card-mark the entire region either just before the next
212 // slow-path allocation by this thread or just before the next scavenge or
213 // CMS-associated safepoint, whichever of these events happens first.
214 // (The implicit assumption is that the object has been fully
215 // initialized by this point, a fact that we assert when doing the
216 // card-mark.)
217 // (c) G1CollectedHeap(G1) uses two kinds of write barriers. When a
218 // G1 concurrent marking is in progress an SATB (pre-write-)barrier is
219 // is used to remember the pre-value of any store. Initializing
220 // stores will not need this barrier, so we need not worry about
221 // compensating for the missing pre-barrier here. Turning now
222 // to the post-barrier, we note that G1 needs a RS update barrier
223 // which simply enqueues a (sequence of) dirty cards which may
224 // optionally be refined by the concurrent update threads. Note
225 // that this barrier need only be applied to a non-young write,
226 // but, like in CMS, because of the presence of concurrent refinement
227 // (much like CMS' precleaning), must strictly follow the oop-store.
228 // Thus, using the same protocol for maintaining the intended
229 // invariants turns out, serendepitously, to be the same for both
230 // G1 and CMS.
231 //
232 // For any future collector, this code should be reexamined with
233 // that specific collector in mind, and the documentation above suitably
234 // extended and updated.
235 oop CollectedHeap::new_store_pre_barrier(JavaThread* thread, oop new_obj) {
236 // If a previous card-mark was deferred, flush it now.
237 flush_deferred_store_barrier(thread);
238 if (can_elide_initializing_store_barrier(new_obj)) {
239 // The deferred_card_mark region should be empty
240 // following the flush above.
241 assert(thread->deferred_card_mark().is_empty(), "Error");
242 } else {
243 MemRegion mr((HeapWord*)new_obj, new_obj->size());
244 assert(!mr.is_empty(), "Error");
245 if (_defer_initial_card_mark) {
246 // Defer the card mark
247 thread->set_deferred_card_mark(mr);
248 } else {
249 // Do the card mark
250 BarrierSet* bs = barrier_set();
251 assert(bs->has_write_region_opt(), "No write_region() on BarrierSet");
252 bs->write_region(mr);
253 }
254 }
255 return new_obj;
256 }
257
258 size_t CollectedHeap::filler_array_hdr_size() {
259 return size_t(align_object_offset(arrayOopDesc::header_size(T_INT))); // align to Long
260 }
261
262 size_t CollectedHeap::filler_array_min_size() {
263 return align_object_size(filler_array_hdr_size()); // align to MinObjAlignment
264 }
265
266 size_t CollectedHeap::filler_array_max_size() {
267 return _filler_array_max_size;
268 }
269
270 #ifdef ASSERT
271 void CollectedHeap::fill_args_check(HeapWord* start, size_t words)
272 {
273 assert(words >= min_fill_size(), "too small to fill");
274 assert(words % MinObjAlignment == 0, "unaligned size");
275 assert(Universe::heap()->is_in_reserved(start), "not in heap");
276 assert(Universe::heap()->is_in_reserved(start + words - 1), "not in heap");
277 }
278
279 void CollectedHeap::zap_filler_array(HeapWord* start, size_t words, bool zap)
280 {
281 if (ZapFillerObjects && zap) {
282 Copy::fill_to_words(start + filler_array_hdr_size(),
283 words - filler_array_hdr_size(), 0XDEAFBABE);
284 }
285 }
286 #endif // ASSERT
287
288 void
289 CollectedHeap::fill_with_array(HeapWord* start, size_t words, bool zap)
290 {
291 assert(words >= filler_array_min_size(), "too small for an array");
292 assert(words <= filler_array_max_size(), "too big for a single object");
293
294 const size_t payload_size = words - filler_array_hdr_size();
295 const size_t len = payload_size * HeapWordSize / sizeof(jint);
296
297 // Set the length first for concurrent GC.
298 ((arrayOop)start)->set_length((int)len);
299 post_allocation_setup_common(Universe::intArrayKlassObj(), start, words);
300 DEBUG_ONLY(zap_filler_array(start, words, zap);)
301 }
302
303 void
304 CollectedHeap::fill_with_object_impl(HeapWord* start, size_t words, bool zap)
305 {
306 assert(words <= filler_array_max_size(), "too big for a single object");
307
308 if (words >= filler_array_min_size()) {
309 fill_with_array(start, words, zap);
310 } else if (words > 0) {
311 assert(words == min_fill_size(), "unaligned size");
312 post_allocation_setup_common(SystemDictionary::Object_klass(), start,
313 words);
314 }
315 }
316
317 void CollectedHeap::fill_with_object(HeapWord* start, size_t words, bool zap)
318 {
319 DEBUG_ONLY(fill_args_check(start, words);)
320 HandleMark hm; // Free handles before leaving.
321 fill_with_object_impl(start, words, zap);
322 }
323
324 void CollectedHeap::fill_with_objects(HeapWord* start, size_t words, bool zap)
325 {
326 DEBUG_ONLY(fill_args_check(start, words);)
327 HandleMark hm; // Free handles before leaving.
328
329 #ifdef _LP64
330 // A single array can fill ~8G, so multiple objects are needed only in 64-bit.
331 // First fill with arrays, ensuring that any remaining space is big enough to
332 // fill. The remainder is filled with a single object.
333 const size_t min = min_fill_size();
334 const size_t max = filler_array_max_size();
335 while (words > max) {
336 const size_t cur = words - max >= min ? max : max - min;
337 fill_with_array(start, cur, zap);
338 start += cur;
339 words -= cur;
340 }
341 #endif
342
343 fill_with_object_impl(start, words, zap);
344 }
345
346 HeapWord* CollectedHeap::allocate_new_tlab(size_t size) {
347 guarantee(false, "thread-local allocation buffers not supported");
348 return NULL;
349 }
350
351 void CollectedHeap::ensure_parsability(bool retire_tlabs) {
352 // The second disjunct in the assertion below makes a concession
353 // for the start-up verification done while the VM is being
354 // created. Callers be careful that you know that mutators
355 // aren't going to interfere -- for instance, this is permissible
356 // if we are still single-threaded and have either not yet
357 // started allocating (nothing much to verify) or we have
358 // started allocating but are now a full-fledged JavaThread
359 // (and have thus made our TLAB's) available for filling.
360 assert(SafepointSynchronize::is_at_safepoint() ||
361 !is_init_completed(),
362 "Should only be called at a safepoint or at start-up"
363 " otherwise concurrent mutator activity may make heap "
364 " unparsable again");
365 const bool use_tlab = UseTLAB;
366 const bool deferred = _defer_initial_card_mark;
367 // The main thread starts allocating via a TLAB even before it
368 // has added itself to the threads list at vm boot-up.
369 assert(!use_tlab || Threads::first() != NULL,
370 "Attempt to fill tlabs before main thread has been added"
371 " to threads list is doomed to failure!");
372 for (JavaThread *thread = Threads::first(); thread; thread = thread->next()) {
373 if (use_tlab) thread->tlab().make_parsable(retire_tlabs);
374 #ifdef COMPILER2
375 // The deferred store barriers must all have been flushed to the
376 // card-table (or other remembered set structure) before GC starts
377 // processing the card-table (or other remembered set).
378 if (deferred) flush_deferred_store_barrier(thread);
379 #else
380 assert(!deferred, "Should be false");
381 assert(thread->deferred_card_mark().is_empty(), "Should be empty");
382 #endif
383 }
384 }
385
386 void CollectedHeap::accumulate_statistics_all_tlabs() {
387 if (UseTLAB) {
388 assert(SafepointSynchronize::is_at_safepoint() ||
389 !is_init_completed(),
390 "should only accumulate statistics on tlabs at safepoint");
391
392 ThreadLocalAllocBuffer::accumulate_statistics_before_gc();
393 }
394 }
395
396 void CollectedHeap::resize_all_tlabs() {
397 if (UseTLAB) {
398 assert(SafepointSynchronize::is_at_safepoint() ||
399 !is_init_completed(),
400 "should only resize tlabs at safepoint");
401
402 ThreadLocalAllocBuffer::resize_all_tlabs();
403 }
404 }
405
406 void CollectedHeap::pre_full_gc_dump() {
407 if (HeapDumpBeforeFullGC) {
408 TraceTime tt("Heap Dump: ", PrintGCDetails, false, gclog_or_tty);
409 // We are doing a "major" collection and a heap dump before
410 // major collection has been requested.
411 HeapDumper::dump_heap();
412 }
413 if (PrintClassHistogramBeforeFullGC) {
414 TraceTime tt("Class Histogram: ", PrintGCDetails, true, gclog_or_tty);
415 VM_GC_HeapInspection inspector(gclog_or_tty, false /* ! full gc */, false /* ! prologue */);
416 inspector.doit();
417 }
418 }
419
420 void CollectedHeap::post_full_gc_dump() {
421 if (HeapDumpAfterFullGC) {
422 TraceTime tt("Heap Dump", PrintGCDetails, false, gclog_or_tty);
423 HeapDumper::dump_heap();
424 }
425 if (PrintClassHistogramAfterFullGC) {
426 TraceTime tt("Class Histogram", PrintGCDetails, true, gclog_or_tty);
427 VM_GC_HeapInspection inspector(gclog_or_tty, false /* ! full gc */, false /* ! prologue */);
428 inspector.doit();
429 }
430 }