jdk8-mips64-public/hotspot: src/share/vm/gc_implementation/g1/g1HotCardCache.cpp@e7d0505c8a30 (annotated)

src/share/vm/gc_implementation/g1/g1HotCardCache.cpp@e7d0505c8a30 (annotated)

src/share/vm/gc_implementation/g1/g1HotCardCache.cpp

Fri, 10 Oct 2014 15:51:58 +0200

author: tschatzl
date: Fri, 10 Oct 2014 15:51:58 +0200
changeset 7257: e7d0505c8a30
parent 7195: c02ec279b062
child 7535: 7ae4e26cb1e0
child 7652: ae374055ebce
permissions: -rw-r--r--

8059758: Footprint regressions with JDK-8038423
Summary: Changes in JDK-8038423 always initialize (zero out) virtual memory used for auxiliary data structures. This causes a footprint regression for G1 in startup benchmarks. This is because they do not touch that memory at all, so the operating system does not actually commit these pages. The fix is to, if the initialization value of the data structures matches the default value of just committed memory (=0), do not do anything.
Reviewed-by: jwilhelm, brutisso

 /*
  * Copyright (c) 2013, 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/dirtyCardQueue.hpp"
 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
 #include "gc_implementation/g1/g1HotCardCache.hpp"
 #include "gc_implementation/g1/g1RemSet.hpp"
 #include "runtime/atomic.hpp"
 G1HotCardCache::G1HotCardCache(G1CollectedHeap *g1h):
   _g1h(g1h), _hot_cache(NULL), _use_cache(false), _card_counts(g1h) {}
 void G1HotCardCache::initialize(G1RegionToSpaceMapper* card_counts_storage) {
   if (default_use_cache()) {
     _use_cache = true;
     _hot_cache_size = (1 << G1ConcRSLogCacheSize);
     _hot_cache = NEW_C_HEAP_ARRAY(jbyte*, _hot_cache_size, mtGC);
     _n_hot = 0;
     _hot_cache_idx = 0;
     // For refining the cards in the hot cache in parallel
     uint n_workers = (ParallelGCThreads > 0 ?
                         _g1h->workers()->total_workers() : 1);
     _hot_cache_par_chunk_size = MAX2(1, _hot_cache_size / (int)n_workers);
     _hot_cache_par_claimed_idx = 0;
     _card_counts.initialize(card_counts_storage);
   }
 }
 G1HotCardCache::~G1HotCardCache() {
   if (default_use_cache()) {
     assert(_hot_cache != NULL, "Logic");
     FREE_C_HEAP_ARRAY(jbyte*, _hot_cache, mtGC);
   }
 }
 jbyte* G1HotCardCache::insert(jbyte* card_ptr) {
   uint count = _card_counts.add_card_count(card_ptr);
   if (!_card_counts.is_hot(count)) {
     // The card is not hot so do not store it in the cache;
     // return it for immediate refining.
     return card_ptr;
   }
   // Otherwise, the card 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] = card_ptr;
   _hot_cache_idx++;
   if (_hot_cache_idx == _hot_cache_size) {
     // Wrap around
     _hot_cache_idx = 0;
   }
   _n_hot++;
   return res;
 }
 void G1HotCardCache::drain(uint worker_i,
                            G1RemSet* g1rs,
                            DirtyCardQueue* into_cset_dcq) {
   if (!default_use_cache()) {
     assert(_hot_cache == NULL, "Logic");
     return;
   }
   assert(_hot_cache != NULL, "Logic");
   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* card_ptr = _hot_cache[i];
         if (card_ptr != NULL) {
           if (g1rs->refine_card(card_ptr, worker_i, true)) {
             // The part of the heap spanned by the card contains references
             // that point into the current collection set.
             // We need to record the card pointer in the DirtyCardQueueSet
             // that we use for such cards.
             //
             // 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(), "Should be at a safepoint");
             assert(worker_i < (ParallelGCThreads == 0 ? 1 : ParallelGCThreads),
                    err_msg("incorrect worker id: "UINT32_FORMAT, worker_i));
             into_cset_dcq->enqueue(card_ptr);
           }
         }
       }
     }
   }
   // The existing entries in the hot card cache, which were just refined
   // above, are discarded prior to re-enabling the cache near the end of the GC.
 }
 void G1HotCardCache::reset_card_counts(HeapRegion* hr) {
   _card_counts.clear_region(hr);
 }
 void G1HotCardCache::reset_card_counts() {
   _card_counts.clear_all();
 }

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/gc_implementation/g1/g1HotCardCache.cpp@e7d0505c8a30 (annotated)

src/share/vm/gc_implementation/g1/g1HotCardCache.cpp