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 /*

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  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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  * This code is free software; you can redistribute it and/or modify it

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  * 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.

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  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 #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[] = {

           16381,    32771,    76831,    150001,   307261,

          614563,  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();

   }

 }