jdk8-mips64-public/hotspot: src/share/vm/gc_implementation/g1/concurrentG1Refine.cpp@e1162778c1c8 (annotated)

src/share/vm/gc_implementation/g1/concurrentG1Refine.cpp@e1162778c1c8 (annotated)

src/share/vm/gc_implementation/g1/concurrentG1Refine.cpp

Thu, 07 Apr 2011 09:53:20 -0700

author: johnc
date: Thu, 07 Apr 2011 09:53:20 -0700
changeset 2781: e1162778c1c8
parent 2716: c84ee870e0b9
child 3900: d2a62e0f25eb
child 3923: 922993931b3d
permissions: -rw-r--r--

7009266: G1: assert(obj->is_oop_or_null(true )) failed: Error
Summary: A referent object that is only weakly reachable at the start of concurrent marking but is re-attached to the strongly reachable object graph during marking may not be marked as live. This can cause the reference object to be processed prematurely and leave dangling pointers to the referent object. Implement a read barrier for the java.lang.ref.Reference::referent field by intrinsifying the Reference.get() method, and intercepting accesses though JNI, reflection, and Unsafe, so that when a non-null referent object is read it is also logged in an SATB buffer.
Reviewed-by: kvn, iveresov, never, tonyp, dholmes

 /*
  * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.
  *
  * This code is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  * version 2 for more details (a copy is included in the LICENSE file that
  * accompanied this code).
  *
  * You should have received a copy of the GNU General Public License version
  * 2 along with this work; if not, write to the Free Software Foundation,
  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  *
  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  * or visit www.oracle.com if you need additional information or have any
  * questions.
  *
  */
 #include "precompiled.hpp"
 #include "gc_implementation/g1/concurrentG1Refine.hpp"
 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
 #include "gc_implementation/g1/g1RemSet.hpp"
 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
 #include "memory/space.inline.hpp"
 #include "runtime/atomic.hpp"
 #include "runtime/java.hpp"
 #include "utilities/copy.hpp"
 // Possible sizes for the card counts cache: odd primes that roughly double in size.
 // (See jvmtiTagMap.cpp).
 #define MAX_SIZE ((size_t) -1)
 size_t ConcurrentG1Refine::_cc_cache_sizes[] = {
 ,    32771,    76831,    150001,   307261,
 ,  1228891,  2457733,   4915219,  9830479,
        19660831, 39321619, 78643219, 157286461,  MAX_SIZE
   };
 ConcurrentG1Refine::ConcurrentG1Refine() :
   _card_counts(NULL), _card_epochs(NULL),
   _n_card_counts(0), _max_cards(0), _max_n_card_counts(0),
   _cache_size_index(0), _expand_card_counts(false),
   _hot_cache(NULL),
   _def_use_cache(false), _use_cache(false),
   // We initialize the epochs of the array to 0. By initializing
   // _n_periods to 1 and not 0 we automatically invalidate all the
   // entries on the array. Otherwise we might accidentally think that
   // we claimed a card that was in fact never set (see CR7033292).
   _n_periods(1),
   _threads(NULL), _n_threads(0)
 {
   // Ergomonically select initial concurrent refinement parameters
   if (FLAG_IS_DEFAULT(G1ConcRefinementGreenZone)) {
     FLAG_SET_DEFAULT(G1ConcRefinementGreenZone, MAX2<int>(ParallelGCThreads, 1));
   }
   set_green_zone(G1ConcRefinementGreenZone);
   if (FLAG_IS_DEFAULT(G1ConcRefinementYellowZone)) {
     FLAG_SET_DEFAULT(G1ConcRefinementYellowZone, green_zone() * 3);
   }
   set_yellow_zone(MAX2<int>(G1ConcRefinementYellowZone, green_zone()));
   if (FLAG_IS_DEFAULT(G1ConcRefinementRedZone)) {
     FLAG_SET_DEFAULT(G1ConcRefinementRedZone, yellow_zone() * 2);
   }
   set_red_zone(MAX2<int>(G1ConcRefinementRedZone, yellow_zone()));
   _n_worker_threads = thread_num();
   // We need one extra thread to do the young gen rset size sampling.
   _n_threads = _n_worker_threads + 1;
   reset_threshold_step();
   _threads = NEW_C_HEAP_ARRAY(ConcurrentG1RefineThread*, _n_threads);
   int worker_id_offset = (int)DirtyCardQueueSet::num_par_ids();
   ConcurrentG1RefineThread *next = NULL;
   for (int i = _n_threads - 1; i >= 0; i--) {
     ConcurrentG1RefineThread* t = new ConcurrentG1RefineThread(this, next, worker_id_offset, i);
     assert(t != NULL, "Conc refine should have been created");
     assert(t->cg1r() == this, "Conc refine thread should refer to this");
     _threads[i] = t;
     next = t;
   }
 }
 void ConcurrentG1Refine::reset_threshold_step() {
   if (FLAG_IS_DEFAULT(G1ConcRefinementThresholdStep)) {
     _thread_threshold_step = (yellow_zone() - green_zone()) / (worker_thread_num() + 1);
   } else {
     _thread_threshold_step = G1ConcRefinementThresholdStep;
   }
 }
 int ConcurrentG1Refine::thread_num() {
   return MAX2<int>((G1ConcRefinementThreads > 0) ? G1ConcRefinementThreads : ParallelGCThreads, 1);
 }
 void ConcurrentG1Refine::init() {
   if (G1ConcRSLogCacheSize > 0) {
     _g1h = G1CollectedHeap::heap();
     _max_cards = _g1h->max_capacity() >> CardTableModRefBS::card_shift;
     _max_n_card_counts = _max_cards * G1MaxHotCardCountSizePercent / 100;
     size_t max_card_num = ((size_t)1 << (sizeof(unsigned)*BitsPerByte-1)) - 1;
     guarantee(_max_cards < max_card_num, "card_num representation");
     // We need _n_card_counts to be less than _max_n_card_counts here
     // so that the expansion call (below) actually allocates the
     // _counts and _epochs arrays.
     assert(_n_card_counts == 0, "pre-condition");
     assert(_max_n_card_counts > 0, "pre-condition");
     // Find the index into cache size array that is of a size that's
     // large enough to hold desired_sz.
     size_t desired_sz = _max_cards / InitialCacheFraction;
     int desired_sz_index = 0;
     while (_cc_cache_sizes[desired_sz_index] < desired_sz) {
       desired_sz_index += 1;
       assert(desired_sz_index <  MAX_CC_CACHE_INDEX, "invariant");
     }
     assert(desired_sz_index <  MAX_CC_CACHE_INDEX, "invariant");
     // If the desired_sz value is between two sizes then
     // _cc_cache_sizes[desired_sz_index-1] < desired_sz <= _cc_cache_sizes[desired_sz_index]
     // we will start with the lower size in the optimistic expectation that
     // we will not need to expand up. Note desired_sz_index could also be 0.
     if (desired_sz_index > 0 &&
         _cc_cache_sizes[desired_sz_index] > desired_sz) {
       desired_sz_index -= 1;
     }
     if (!expand_card_count_cache(desired_sz_index)) {
       // Allocation was unsuccessful - exit
       vm_exit_during_initialization("Could not reserve enough space for card count cache");
     }
     assert(_n_card_counts > 0, "post-condition");
     assert(_cache_size_index == desired_sz_index, "post-condition");
     Copy::fill_to_bytes(&_card_counts[0],
                         _n_card_counts * sizeof(CardCountCacheEntry));
     Copy::fill_to_bytes(&_card_epochs[0], _n_card_counts * sizeof(CardEpochCacheEntry));
     ModRefBarrierSet* bs = _g1h->mr_bs();
     guarantee(bs->is_a(BarrierSet::CardTableModRef), "Precondition");
     _ct_bs = (CardTableModRefBS*)bs;
     _ct_bot = _ct_bs->byte_for_const(_g1h->reserved_region().start());
     _def_use_cache = true;
     _use_cache = true;
     _hot_cache_size = (1 << G1ConcRSLogCacheSize);
     _hot_cache = NEW_C_HEAP_ARRAY(jbyte*, _hot_cache_size);
     _n_hot = 0;
     _hot_cache_idx = 0;
     // For refining the cards in the hot cache in parallel
     int n_workers = (ParallelGCThreads > 0 ?
                         _g1h->workers()->total_workers() : 1);
     _hot_cache_par_chunk_size = MAX2(1, _hot_cache_size / n_workers);
     _hot_cache_par_claimed_idx = 0;
   }
 }
 void ConcurrentG1Refine::stop() {
   if (_threads != NULL) {
     for (int i = 0; i < _n_threads; i++) {
       _threads[i]->stop();
     }
   }
 }
 void ConcurrentG1Refine::reinitialize_threads() {
   reset_threshold_step();
   if (_threads != NULL) {
     for (int i = 0; i < _n_threads; i++) {
       _threads[i]->initialize();
     }
   }
 }
 ConcurrentG1Refine::~ConcurrentG1Refine() {
   if (G1ConcRSLogCacheSize > 0) {
     // Please see the comment in allocate_card_count_cache
     // for why we call os::malloc() and os::free() directly.
     assert(_card_counts != NULL, "Logic");
     os::free(_card_counts);
     assert(_card_epochs != NULL, "Logic");
     os::free(_card_epochs);
     assert(_hot_cache != NULL, "Logic");
     FREE_C_HEAP_ARRAY(jbyte*, _hot_cache);
   }
   if (_threads != NULL) {
     for (int i = 0; i < _n_threads; i++) {
       delete _threads[i];
     }
     FREE_C_HEAP_ARRAY(ConcurrentG1RefineThread*, _threads);
   }
 }
 void ConcurrentG1Refine::threads_do(ThreadClosure *tc) {
   if (_threads != NULL) {
     for (int i = 0; i < _n_threads; i++) {
       tc->do_thread(_threads[i]);
     }
   }
 }
 bool ConcurrentG1Refine::is_young_card(jbyte* card_ptr) {
   HeapWord* start = _ct_bs->addr_for(card_ptr);
   HeapRegion* r = _g1h->heap_region_containing(start);
   if (r != NULL && r->is_young()) {
     return true;
   }
   // This card is not associated with a heap region
   // so can't be young.
   return false;
 }
 jbyte* ConcurrentG1Refine::add_card_count(jbyte* card_ptr, int* count, bool* defer) {
   unsigned new_card_num = ptr_2_card_num(card_ptr);
   unsigned bucket = hash(new_card_num);
   assert(0 <= bucket && bucket < _n_card_counts, "Bounds");
   CardCountCacheEntry* count_ptr = &_card_counts[bucket];
   CardEpochCacheEntry* epoch_ptr = &_card_epochs[bucket];
   // We have to construct a new entry if we haven't updated the counts
   // during the current period, or if the count was updated for a
   // different card number.
   unsigned int new_epoch = (unsigned int) _n_periods;
   julong new_epoch_entry = make_epoch_entry(new_card_num, new_epoch);
   while (true) {
     // Fetch the previous epoch value
     julong prev_epoch_entry = epoch_ptr->_value;
     julong cas_res;
     if (extract_epoch(prev_epoch_entry) != new_epoch) {
       // This entry has not yet been updated during this period.
       // Note: we update the epoch value atomically to ensure
       // that there is only one winner that updates the cached
       // card_ptr value even though all the refine threads share
       // the same epoch value.
       cas_res = (julong) Atomic::cmpxchg((jlong) new_epoch_entry,
                                          (volatile jlong*)&epoch_ptr->_value,
                                          (jlong) prev_epoch_entry);
       if (cas_res == prev_epoch_entry) {
         // We have successfully won the race to update the
         // epoch and card_num value. Make it look like the
         // count and eviction count were previously cleared.
         count_ptr->_count = 1;
         count_ptr->_evict_count = 0;
         *count = 0;
         // We can defer the processing of card_ptr
         *defer = true;
         return card_ptr;
       }
       // We did not win the race to update the epoch field, so some other
       // thread must have done it. The value that gets returned by CAS
       // should be the new epoch value.
       assert(extract_epoch(cas_res) == new_epoch, "unexpected epoch");
       // We could 'continue' here or just re-read the previous epoch value
       prev_epoch_entry = epoch_ptr->_value;
     }
     // The epoch entry for card_ptr has been updated during this period.
     unsigned old_card_num = extract_card_num(prev_epoch_entry);
     // The card count that will be returned to caller
     *count = count_ptr->_count;
     // Are we updating the count for the same card?
     if (new_card_num == old_card_num) {
       // Same card - just update the count. We could have more than one
       // thread racing to update count for the current card. It should be
       // OK not to use a CAS as the only penalty should be some missed
       // increments of the count which delays identifying the card as "hot".
       if (*count < max_jubyte) count_ptr->_count++;
       // We can defer the processing of card_ptr
       *defer = true;
       return card_ptr;
     }
     // Different card - evict old card info
     if (count_ptr->_evict_count < max_jubyte) count_ptr->_evict_count++;
     if (count_ptr->_evict_count > G1CardCountCacheExpandThreshold) {
       // Trigger a resize the next time we clear
       _expand_card_counts = true;
     }
     cas_res = (julong) Atomic::cmpxchg((jlong) new_epoch_entry,
                                        (volatile jlong*)&epoch_ptr->_value,
                                        (jlong) prev_epoch_entry);
     if (cas_res == prev_epoch_entry) {
       // We successfully updated the card num value in the epoch entry
       count_ptr->_count = 0; // initialize counter for new card num
       jbyte* old_card_ptr = card_num_2_ptr(old_card_num);
       // Even though the region containg the card at old_card_num was not
       // in the young list when old_card_num was recorded in the epoch
       // cache it could have been added to the free list and subsequently
       // added to the young list in the intervening time. See CR 6817995.
       // We do not deal with this case here - it will be handled in
       // HeapRegion::oops_on_card_seq_iterate_careful after it has been
       // determined that the region containing the card has been allocated
       // to, and it's safe to check the young type of the region.
       // We do not want to defer processing of card_ptr in this case
       // (we need to refine old_card_ptr and card_ptr)
       *defer = false;
       return old_card_ptr;
     }
     // Someone else beat us - try again.
   }
 }
 jbyte* ConcurrentG1Refine::cache_insert(jbyte* card_ptr, bool* defer) {
   int count;
   jbyte* cached_ptr = add_card_count(card_ptr, &count, defer);
   assert(cached_ptr != NULL, "bad cached card ptr");
   // We've just inserted a card pointer into the card count cache
   // and got back the card that we just inserted or (evicted) the
   // previous contents of that count slot.
   // The card we got back could be in a young region. When the
   // returned card (if evicted) was originally inserted, we had
   // determined that its containing region was not young. However
   // it is possible for the region to be freed during a cleanup
   // pause, then reallocated and tagged as young which will result
   // in the returned card residing in a young region.
   //
   // We do not deal with this case here - the change from non-young
   // to young could be observed at any time - it will be handled in
   // HeapRegion::oops_on_card_seq_iterate_careful after it has been
   // determined that the region containing the card has been allocated
   // to.
   // The card pointer we obtained from card count cache is not hot
   // so do not store it in the cache; return it for immediate
   // refining.
   if (count < G1ConcRSHotCardLimit) {
     return cached_ptr;
   }
   // Otherwise, the pointer we got from the _card_counts cache is hot.
   jbyte* res = NULL;
   MutexLockerEx x(HotCardCache_lock, Mutex::_no_safepoint_check_flag);
   if (_n_hot == _hot_cache_size) {
     res = _hot_cache[_hot_cache_idx];
     _n_hot--;
   }
   // Now _n_hot < _hot_cache_size, and we can insert at _hot_cache_idx.
   _hot_cache[_hot_cache_idx] = cached_ptr;
   _hot_cache_idx++;
   if (_hot_cache_idx == _hot_cache_size) _hot_cache_idx = 0;
   _n_hot++;
   // The card obtained from the hot card cache could be in a young
   // region. See above on how this can happen.
   return res;
 }
 void ConcurrentG1Refine::clean_up_cache(int worker_i,
                                         G1RemSet* g1rs,
                                         DirtyCardQueue* into_cset_dcq) {
   assert(!use_cache(), "cache should be disabled");
   int start_idx;
   while ((start_idx = _hot_cache_par_claimed_idx) < _n_hot) { // read once
     int end_idx = start_idx + _hot_cache_par_chunk_size;
     if (start_idx ==
         Atomic::cmpxchg(end_idx, &_hot_cache_par_claimed_idx, start_idx)) {
       // The current worker has successfully claimed the chunk [start_idx..end_idx)
       end_idx = MIN2(end_idx, _n_hot);
       for (int i = start_idx; i < end_idx; i++) {
         jbyte* entry = _hot_cache[i];
         if (entry != NULL) {
           if (g1rs->concurrentRefineOneCard(entry, worker_i, true)) {
             // 'entry' contains references that point into the current
             // collection set. We need to record 'entry' in the DCQS
             // that's used for that purpose.
             //
             // The only time we care about recording cards that contain
             // references that point into the collection set is during
             // RSet updating while within an evacuation pause.
             // In this case worker_i should be the id of a GC worker thread
             assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");
             assert(worker_i < (int) (ParallelGCThreads == 0 ? 1 : ParallelGCThreads), "incorrect worker id");
             into_cset_dcq->enqueue(entry);
           }
         }
       }
     }
   }
 }
 // The arrays used to hold the card counts and the epochs must have
 // a 1:1 correspondence. Hence they are allocated and freed together
 // Returns true if the allocations of both the counts and epochs
 // were successful; false otherwise.
 bool ConcurrentG1Refine::allocate_card_count_cache(size_t n,
                                                    CardCountCacheEntry** counts,
                                                    CardEpochCacheEntry** epochs) {
   // We call the allocation/free routines directly for the counts
   // and epochs arrays. The NEW_C_HEAP_ARRAY/FREE_C_HEAP_ARRAY
   // macros call AllocateHeap and FreeHeap respectively.
   // AllocateHeap will call vm_exit_out_of_memory in the event
   // of an allocation failure and abort the JVM. With the
   // _counts/epochs arrays we only need to abort the JVM if the
   // initial allocation of these arrays fails.
   //
   // Additionally AllocateHeap/FreeHeap do some tracing of
   // allocate/free calls so calling one without calling the
   // other can cause inconsistencies in the tracing. So we
   // call neither.
   assert(*counts == NULL, "out param");
   assert(*epochs == NULL, "out param");
   size_t counts_size = n * sizeof(CardCountCacheEntry);
   size_t epochs_size = n * sizeof(CardEpochCacheEntry);
   *counts = (CardCountCacheEntry*) os::malloc(counts_size);
   if (*counts == NULL) {
     // allocation was unsuccessful
     return false;
   }
   *epochs = (CardEpochCacheEntry*) os::malloc(epochs_size);
   if (*epochs == NULL) {
     // allocation was unsuccessful - free counts array
     assert(*counts != NULL, "must be");
     os::free(*counts);
     *counts = NULL;
     return false;
   }
   // We successfully allocated both counts and epochs
   return true;
 }
 // Returns true if the card counts/epochs cache was
 // successfully expanded; false otherwise.
 bool ConcurrentG1Refine::expand_card_count_cache(int cache_size_idx) {
   // Can we expand the card count and epoch tables?
   if (_n_card_counts < _max_n_card_counts) {
     assert(cache_size_idx >= 0 && cache_size_idx  < MAX_CC_CACHE_INDEX, "oob");
     size_t cache_size = _cc_cache_sizes[cache_size_idx];
     // Make sure we don't go bigger than we will ever need
     cache_size = MIN2(cache_size, _max_n_card_counts);
     // Should we expand the card count and card epoch tables?
     if (cache_size > _n_card_counts) {
       // We have been asked to allocate new, larger, arrays for
       // the card counts and the epochs. Attempt the allocation
       // of both before we free the existing arrays in case
       // the allocation is unsuccessful...
       CardCountCacheEntry* counts = NULL;
       CardEpochCacheEntry* epochs = NULL;
       if (allocate_card_count_cache(cache_size, &counts, &epochs)) {
         // Allocation was successful.
         // We can just free the old arrays; we're
         // not interested in preserving the contents
         if (_card_counts != NULL) os::free(_card_counts);
         if (_card_epochs != NULL) os::free(_card_epochs);
         // Cache the size of the arrays and the index that got us there.
         _n_card_counts = cache_size;
         _cache_size_index = cache_size_idx;
         _card_counts = counts;
         _card_epochs = epochs;
         // We successfully allocated/expanded the caches.
         return true;
       }
     }
   }
   // We did not successfully expand the caches.
   return false;
 }
 void ConcurrentG1Refine::clear_and_record_card_counts() {
   if (G1ConcRSLogCacheSize == 0) return;
 #ifndef PRODUCT
   double start = os::elapsedTime();
 #endif
   if (_expand_card_counts) {
     int new_idx = _cache_size_index + 1;
     if (expand_card_count_cache(new_idx)) {
       // Allocation was successful and  _n_card_counts has
       // been updated to the new size. We only need to clear
       // the epochs so we don't read a bogus epoch value
       // when inserting a card into the hot card cache.
       Copy::fill_to_bytes(&_card_epochs[0], _n_card_counts * sizeof(CardEpochCacheEntry));
     }
     _expand_card_counts = false;
   }
   int this_epoch = (int) _n_periods;
   assert((this_epoch+1) <= max_jint, "to many periods");
   // Update epoch
   _n_periods++;
 #ifndef PRODUCT
   double elapsed = os::elapsedTime() - start;
   _g1h->g1_policy()->record_cc_clear_time(elapsed * 1000.0);
 #endif
 }
 void ConcurrentG1Refine::print_worker_threads_on(outputStream* st) const {
   for (int i = 0; i < _n_threads; ++i) {
     _threads[i]->print_on(st);
     st->cr();
   }
 }

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src/share/vm/gc_implementation/g1/concurrentG1Refine.cpp@e1162778c1c8 (annotated)

src/share/vm/gc_implementation/g1/concurrentG1Refine.cpp