1 /*
2 * Copyright (c) 2001, 2011, 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 "oops/instanceMirrorKlass.hpp"
32 #include "runtime/init.hpp"
33 #include "services/heapDumper.hpp"
34 #ifdef TARGET_OS_FAMILY_linux
35 # include "thread_linux.inline.hpp"
36 #endif
37 #ifdef TARGET_OS_FAMILY_solaris
38 # include "thread_solaris.inline.hpp"
39 #endif
40 #ifdef TARGET_OS_FAMILY_windows
41 # include "thread_windows.inline.hpp"
42 #endif
43 #ifdef TARGET_OS_FAMILY_bsd
44 # include "thread_bsd.inline.hpp"
45 #endif
46
47
48 #ifdef ASSERT
49 int CollectedHeap::_fire_out_of_memory_count = 0;
50 #endif
51
52 size_t CollectedHeap::_filler_array_max_size = 0;
53
54 // Memory state functions.
55
56
57 CollectedHeap::CollectedHeap() : _n_par_threads(0)
58
59 {
60 const size_t max_len = size_t(arrayOopDesc::max_array_length(T_INT));
61 const size_t elements_per_word = HeapWordSize / sizeof(jint);
62 _filler_array_max_size = align_object_size(filler_array_hdr_size() +
63 max_len * elements_per_word);
64
65 _barrier_set = NULL;
66 _is_gc_active = false;
67 _total_collections = _total_full_collections = 0;
68 _gc_cause = _gc_lastcause = GCCause::_no_gc;
69 NOT_PRODUCT(_promotion_failure_alot_count = 0;)
70 NOT_PRODUCT(_promotion_failure_alot_gc_number = 0;)
71
72 if (UsePerfData) {
73 EXCEPTION_MARK;
74
75 // create the gc cause jvmstat counters
76 _perf_gc_cause = PerfDataManager::create_string_variable(SUN_GC, "cause",
77 80, GCCause::to_string(_gc_cause), CHECK);
78
79 _perf_gc_lastcause =
80 PerfDataManager::create_string_variable(SUN_GC, "lastCause",
81 80, GCCause::to_string(_gc_lastcause), CHECK);
82 }
83 _defer_initial_card_mark = false; // strengthened by subclass in pre_initialize() below.
84 }
85
86 void CollectedHeap::pre_initialize() {
87 // Used for ReduceInitialCardMarks (when COMPILER2 is used);
88 // otherwise remains unused.
89 #ifdef COMPILER2
90 _defer_initial_card_mark = ReduceInitialCardMarks && can_elide_tlab_store_barriers()
91 && (DeferInitialCardMark || card_mark_must_follow_store());
92 #else
93 assert(_defer_initial_card_mark == false, "Who would set it?");
94 #endif
95 }
96
97 #ifndef PRODUCT
98 void CollectedHeap::check_for_bad_heap_word_value(HeapWord* addr, size_t size) {
99 if (CheckMemoryInitialization && ZapUnusedHeapArea) {
100 for (size_t slot = 0; slot < size; slot += 1) {
101 assert((*(intptr_t*) (addr + slot)) != ((intptr_t) badHeapWordVal),
102 "Found badHeapWordValue in post-allocation check");
103 }
104 }
105 }
106
107 void CollectedHeap::check_for_non_bad_heap_word_value(HeapWord* addr, size_t size) {
108 if (CheckMemoryInitialization && ZapUnusedHeapArea) {
109 for (size_t slot = 0; slot < size; slot += 1) {
110 assert((*(intptr_t*) (addr + slot)) == ((intptr_t) badHeapWordVal),
111 "Found non badHeapWordValue in pre-allocation check");
112 }
113 }
114 }
115 #endif // PRODUCT
116
117 #ifdef ASSERT
118 void CollectedHeap::check_for_valid_allocation_state() {
119 Thread *thread = Thread::current();
120 // How to choose between a pending exception and a potential
121 // OutOfMemoryError? Don't allow pending exceptions.
122 // This is a VM policy failure, so how do we exhaustively test it?
123 assert(!thread->has_pending_exception(),
124 "shouldn't be allocating with pending exception");
125 if (StrictSafepointChecks) {
126 assert(thread->allow_allocation(),
127 "Allocation done by thread for which allocation is blocked "
128 "by No_Allocation_Verifier!");
129 // Allocation of an oop can always invoke a safepoint,
130 // hence, the true argument
131 thread->check_for_valid_safepoint_state(true);
132 }
133 }
134 #endif
135
136 HeapWord* CollectedHeap::allocate_from_tlab_slow(Thread* thread, size_t size) {
137
138 // Retain tlab and allocate object in shared space if
139 // the amount free in the tlab is too large to discard.
140 if (thread->tlab().free() > thread->tlab().refill_waste_limit()) {
141 thread->tlab().record_slow_allocation(size);
142 return NULL;
143 }
144
145 // Discard tlab and allocate a new one.
146 // To minimize fragmentation, the last TLAB may be smaller than the rest.
147 size_t new_tlab_size = thread->tlab().compute_size(size);
148
149 thread->tlab().clear_before_allocation();
150
151 if (new_tlab_size == 0) {
152 return NULL;
153 }
154
155 // Allocate a new TLAB...
156 HeapWord* obj = Universe::heap()->allocate_new_tlab(new_tlab_size);
157 if (obj == NULL) {
158 return NULL;
159 }
160 if (ZeroTLAB) {
161 // ..and clear it.
162 Copy::zero_to_words(obj, new_tlab_size);
163 } else {
164 // ...and zap just allocated object.
165 #ifdef ASSERT
166 // Skip mangling the space corresponding to the object header to
167 // ensure that the returned space is not considered parsable by
168 // any concurrent GC thread.
169 size_t hdr_size = oopDesc::header_size();
170 Copy::fill_to_words(obj + hdr_size, new_tlab_size - hdr_size, badHeapWordVal);
171 #endif // ASSERT
172 }
173 thread->tlab().fill(obj, obj + size, new_tlab_size);
174 return obj;
175 }
176
177 void CollectedHeap::flush_deferred_store_barrier(JavaThread* thread) {
178 MemRegion deferred = thread->deferred_card_mark();
179 if (!deferred.is_empty()) {
180 assert(_defer_initial_card_mark, "Otherwise should be empty");
181 {
182 // Verify that the storage points to a parsable object in heap
183 DEBUG_ONLY(oop old_obj = oop(deferred.start());)
184 assert(is_in(old_obj), "Not in allocated heap");
185 assert(!can_elide_initializing_store_barrier(old_obj),
186 "Else should have been filtered in new_store_pre_barrier()");
187 assert(!is_in_permanent(old_obj), "Sanity: not expected");
188 assert(old_obj->is_oop(true), "Not an oop");
189 assert(old_obj->is_parsable(), "Will not be concurrently parsable");
190 assert(deferred.word_size() == (size_t)(old_obj->size()),
191 "Mismatch: multiple objects?");
192 }
193 BarrierSet* bs = barrier_set();
194 assert(bs->has_write_region_opt(), "No write_region() on BarrierSet");
195 bs->write_region(deferred);
196 // "Clear" the deferred_card_mark field
197 thread->set_deferred_card_mark(MemRegion());
198 }
199 assert(thread->deferred_card_mark().is_empty(), "invariant");
200 }
201
202 // Helper for ReduceInitialCardMarks. For performance,
203 // compiled code may elide card-marks for initializing stores
204 // to a newly allocated object along the fast-path. We
205 // compensate for such elided card-marks as follows:
206 // (a) Generational, non-concurrent collectors, such as
207 // GenCollectedHeap(ParNew,DefNew,Tenured) and
208 // ParallelScavengeHeap(ParallelGC, ParallelOldGC)
209 // need the card-mark if and only if the region is
210 // in the old gen, and do not care if the card-mark
211 // succeeds or precedes the initializing stores themselves,
212 // so long as the card-mark is completed before the next
213 // scavenge. For all these cases, we can do a card mark
214 // at the point at which we do a slow path allocation
215 // in the old gen, i.e. in this call.
216 // (b) GenCollectedHeap(ConcurrentMarkSweepGeneration) requires
217 // in addition that the card-mark for an old gen allocated
218 // object strictly follow any associated initializing stores.
219 // In these cases, the memRegion remembered below is
220 // used to card-mark the entire region either just before the next
221 // slow-path allocation by this thread or just before the next scavenge or
222 // CMS-associated safepoint, whichever of these events happens first.
223 // (The implicit assumption is that the object has been fully
224 // initialized by this point, a fact that we assert when doing the
225 // card-mark.)
226 // (c) G1CollectedHeap(G1) uses two kinds of write barriers. When a
227 // G1 concurrent marking is in progress an SATB (pre-write-)barrier is
228 // is used to remember the pre-value of any store. Initializing
229 // stores will not need this barrier, so we need not worry about
230 // compensating for the missing pre-barrier here. Turning now
231 // to the post-barrier, we note that G1 needs a RS update barrier
232 // which simply enqueues a (sequence of) dirty cards which may
233 // optionally be refined by the concurrent update threads. Note
234 // that this barrier need only be applied to a non-young write,
235 // but, like in CMS, because of the presence of concurrent refinement
236 // (much like CMS' precleaning), must strictly follow the oop-store.
237 // Thus, using the same protocol for maintaining the intended
238 // invariants turns out, serendepitously, to be the same for both
239 // G1 and CMS.
240 //
241 // For any future collector, this code should be reexamined with
242 // that specific collector in mind, and the documentation above suitably
243 // extended and updated.
244 oop CollectedHeap::new_store_pre_barrier(JavaThread* thread, oop new_obj) {
245 // If a previous card-mark was deferred, flush it now.
246 flush_deferred_store_barrier(thread);
247 if (can_elide_initializing_store_barrier(new_obj)) {
248 // The deferred_card_mark region should be empty
249 // following the flush above.
250 assert(thread->deferred_card_mark().is_empty(), "Error");
251 } else {
252 MemRegion mr((HeapWord*)new_obj, new_obj->size());
253 assert(!mr.is_empty(), "Error");
254 if (_defer_initial_card_mark) {
255 // Defer the card mark
256 thread->set_deferred_card_mark(mr);
257 } else {
258 // Do the card mark
259 BarrierSet* bs = barrier_set();
260 assert(bs->has_write_region_opt(), "No write_region() on BarrierSet");
261 bs->write_region(mr);
262 }
263 }
264 return new_obj;
265 }
266
267 size_t CollectedHeap::filler_array_hdr_size() {
268 return size_t(align_object_offset(arrayOopDesc::header_size(T_INT))); // align to Long
269 }
270
271 size_t CollectedHeap::filler_array_min_size() {
272 return align_object_size(filler_array_hdr_size()); // align to MinObjAlignment
273 }
274
275 size_t CollectedHeap::filler_array_max_size() {
276 return _filler_array_max_size;
277 }
278
279 #ifdef ASSERT
280 void CollectedHeap::fill_args_check(HeapWord* start, size_t words)
281 {
282 assert(words >= min_fill_size(), "too small to fill");
283 assert(words % MinObjAlignment == 0, "unaligned size");
284 assert(Universe::heap()->is_in_reserved(start), "not in heap");
285 assert(Universe::heap()->is_in_reserved(start + words - 1), "not in heap");
286 }
287
288 void CollectedHeap::zap_filler_array(HeapWord* start, size_t words, bool zap)
289 {
290 if (ZapFillerObjects && zap) {
291 Copy::fill_to_words(start + filler_array_hdr_size(),
292 words - filler_array_hdr_size(), 0XDEAFBABE);
293 }
294 }
295 #endif // ASSERT
296
297 void
298 CollectedHeap::fill_with_array(HeapWord* start, size_t words, bool zap)
299 {
300 assert(words >= filler_array_min_size(), "too small for an array");
301 assert(words <= filler_array_max_size(), "too big for a single object");
302
303 const size_t payload_size = words - filler_array_hdr_size();
304 const size_t len = payload_size * HeapWordSize / sizeof(jint);
305
306 // Set the length first for concurrent GC.
307 ((arrayOop)start)->set_length((int)len);
308 post_allocation_setup_common(Universe::intArrayKlassObj(), start, words);
309 DEBUG_ONLY(zap_filler_array(start, words, zap);)
310 }
311
312 void
313 CollectedHeap::fill_with_object_impl(HeapWord* start, size_t words, bool zap)
314 {
315 assert(words <= filler_array_max_size(), "too big for a single object");
316
317 if (words >= filler_array_min_size()) {
318 fill_with_array(start, words, zap);
319 } else if (words > 0) {
320 assert(words == min_fill_size(), "unaligned size");
321 post_allocation_setup_common(SystemDictionary::Object_klass(), start,
322 words);
323 }
324 }
325
326 void CollectedHeap::fill_with_object(HeapWord* start, size_t words, bool zap)
327 {
328 DEBUG_ONLY(fill_args_check(start, words);)
329 HandleMark hm; // Free handles before leaving.
330 fill_with_object_impl(start, words, zap);
331 }
332
333 void CollectedHeap::fill_with_objects(HeapWord* start, size_t words, bool zap)
334 {
335 DEBUG_ONLY(fill_args_check(start, words);)
336 HandleMark hm; // Free handles before leaving.
337
338 #ifdef _LP64
339 // A single array can fill ~8G, so multiple objects are needed only in 64-bit.
340 // First fill with arrays, ensuring that any remaining space is big enough to
341 // fill. The remainder is filled with a single object.
342 const size_t min = min_fill_size();
343 const size_t max = filler_array_max_size();
344 while (words > max) {
345 const size_t cur = words - max >= min ? max : max - min;
346 fill_with_array(start, cur, zap);
347 start += cur;
348 words -= cur;
349 }
350 #endif
351
352 fill_with_object_impl(start, words, zap);
353 }
354
355 HeapWord* CollectedHeap::allocate_new_tlab(size_t size) {
356 guarantee(false, "thread-local allocation buffers not supported");
357 return NULL;
358 }
359
360 void CollectedHeap::ensure_parsability(bool retire_tlabs) {
361 // The second disjunct in the assertion below makes a concession
362 // for the start-up verification done while the VM is being
363 // created. Callers be careful that you know that mutators
364 // aren't going to interfere -- for instance, this is permissible
365 // if we are still single-threaded and have either not yet
366 // started allocating (nothing much to verify) or we have
367 // started allocating but are now a full-fledged JavaThread
368 // (and have thus made our TLAB's) available for filling.
369 assert(SafepointSynchronize::is_at_safepoint() ||
370 !is_init_completed(),
371 "Should only be called at a safepoint or at start-up"
372 " otherwise concurrent mutator activity may make heap "
373 " unparsable again");
374 const bool use_tlab = UseTLAB;
375 const bool deferred = _defer_initial_card_mark;
376 // The main thread starts allocating via a TLAB even before it
377 // has added itself to the threads list at vm boot-up.
378 assert(!use_tlab || Threads::first() != NULL,
379 "Attempt to fill tlabs before main thread has been added"
380 " to threads list is doomed to failure!");
381 for (JavaThread *thread = Threads::first(); thread; thread = thread->next()) {
382 if (use_tlab) thread->tlab().make_parsable(retire_tlabs);
383 #ifdef COMPILER2
384 // The deferred store barriers must all have been flushed to the
385 // card-table (or other remembered set structure) before GC starts
386 // processing the card-table (or other remembered set).
387 if (deferred) flush_deferred_store_barrier(thread);
388 #else
389 assert(!deferred, "Should be false");
390 assert(thread->deferred_card_mark().is_empty(), "Should be empty");
391 #endif
392 }
393 }
394
395 void CollectedHeap::accumulate_statistics_all_tlabs() {
396 if (UseTLAB) {
397 assert(SafepointSynchronize::is_at_safepoint() ||
398 !is_init_completed(),
399 "should only accumulate statistics on tlabs at safepoint");
400
401 ThreadLocalAllocBuffer::accumulate_statistics_before_gc();
402 }
403 }
404
405 void CollectedHeap::resize_all_tlabs() {
406 if (UseTLAB) {
407 assert(SafepointSynchronize::is_at_safepoint() ||
408 !is_init_completed(),
409 "should only resize tlabs at safepoint");
410
411 ThreadLocalAllocBuffer::resize_all_tlabs();
412 }
413 }
414
415 void CollectedHeap::pre_full_gc_dump() {
416 if (HeapDumpBeforeFullGC) {
417 TraceTime tt("Heap Dump (before full gc): ", PrintGCDetails, false, gclog_or_tty);
418 // We are doing a "major" collection and a heap dump before
419 // major collection has been requested.
420 HeapDumper::dump_heap();
421 }
422 if (PrintClassHistogramBeforeFullGC) {
423 TraceTime tt("Class Histogram (before full gc): ", PrintGCDetails, true, gclog_or_tty);
424 VM_GC_HeapInspection inspector(gclog_or_tty, false /* ! full gc */, false /* ! prologue */);
425 inspector.doit();
426 }
427 }
428
429 void CollectedHeap::post_full_gc_dump() {
430 if (HeapDumpAfterFullGC) {
431 TraceTime tt("Heap Dump (after full gc): ", PrintGCDetails, false, gclog_or_tty);
432 HeapDumper::dump_heap();
433 }
434 if (PrintClassHistogramAfterFullGC) {
435 TraceTime tt("Class Histogram (after full gc): ", PrintGCDetails, true, gclog_or_tty);
436 VM_GC_HeapInspection inspector(gclog_or_tty, false /* ! full gc */, false /* ! prologue */);
437 inspector.doit();
438 }
439 }
440
441 oop CollectedHeap::Class_obj_allocate(KlassHandle klass, int size, KlassHandle real_klass, TRAPS) {
442 debug_only(check_for_valid_allocation_state());
443 assert(!Universe::heap()->is_gc_active(), "Allocation during gc not allowed");
444 assert(size >= 0, "int won't convert to size_t");
445 HeapWord* obj;
446 if (JavaObjectsInPerm) {
447 obj = common_permanent_mem_allocate_init(size, CHECK_NULL);
448 } else {
449 assert(ScavengeRootsInCode > 0, "must be");
450 obj = common_mem_allocate_init(size, CHECK_NULL);
451 }
452 post_allocation_setup_common(klass, obj, size);
453 assert(Universe::is_bootstrapping() ||
454 !((oop)obj)->blueprint()->oop_is_array(), "must not be an array");
455 NOT_PRODUCT(Universe::heap()->check_for_bad_heap_word_value(obj, size));
456 oop mirror = (oop)obj;
457
458 java_lang_Class::set_oop_size(mirror, size);
459
460 // Setup indirections
461 if (!real_klass.is_null()) {
462 java_lang_Class::set_klass(mirror, real_klass());
463 real_klass->set_java_mirror(mirror);
464 }
465
466 instanceMirrorKlass* mk = instanceMirrorKlass::cast(mirror->klass());
467 assert(size == mk->instance_size(real_klass), "should have been set");
468
469 // notify jvmti and dtrace
470 post_allocation_notify(klass, (oop)obj);
471
472 return mirror;
473 }
474
475 /////////////// Unit tests ///////////////
476
477 #ifndef PRODUCT
478 void CollectedHeap::test_is_in() {
479 CollectedHeap* heap = Universe::heap();
480
481 // Test that NULL is not in the heap.
482 assert(!heap->is_in(NULL), "NULL is unexpectedly in the heap");
483
484 // Test that a pointer to before the heap start is reported as outside the heap.
485 assert(heap->_reserved.start() >= (void*)(uintptr_t)MinObjAlignment, "sanity");
486 void* before_heap = (void*)((uintptr_t)heap->_reserved.start() - MinObjAlignment);
487 assert(!heap->is_in(before_heap),
488 err_msg("before_heap: " PTR_FORMAT " is unexpectedly in the heap", before_heap));
489
490 // Test that a pointer to after the heap end is reported as outside the heap.
491 assert(heap->_reserved.end() <= (void*)(uintptr_t(-1) - MinObjAlignment), "sanity");
492 void* after_heap = (void*)((uintptr_t)heap->_reserved.end() + MinObjAlignment);
493 assert(!heap->is_in(after_heap),
494 err_msg("after_heap: " PTR_FORMAT " is unexpectedly in the heap", after_heap));
495 }
496 #endif