--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/g1/g1HotCardCache.cpp	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,116 @@
+/*
+ * Copyright (c) 2013, 2017, 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/g1/dirtyCardQueue.hpp"
+#include "gc/g1/g1CollectedHeap.inline.hpp"
+#include "gc/g1/g1HotCardCache.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 = (size_t)1 << G1ConcRSLogCacheSize;
+    _hot_cache = ArrayAllocator<jbyte*>::allocate(_hot_cache_size, mtGC);
+
+    reset_hot_cache_internal();
+
+    // For refining the cards in the hot cache in parallel
+    _hot_cache_par_chunk_size = ClaimChunkSize;
+    _hot_cache_par_claimed_idx = 0;
+
+    _card_counts.initialize(card_counts_storage);
+  }
+}
+
+G1HotCardCache::~G1HotCardCache() {
+  if (default_use_cache()) {
+    assert(_hot_cache != NULL, "Logic");
+    ArrayAllocator<jbyte*>::free(_hot_cache, _hot_cache_size);
+    _hot_cache = NULL;
+  }
+}
+
+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.
+  size_t index = Atomic::add(1u, &_hot_cache_idx) - 1;
+  size_t masked_index = index & (_hot_cache_size - 1);
+  jbyte* current_ptr = _hot_cache[masked_index];
+
+  // Try to store the new card pointer into the cache. Compare-and-swap to guard
+  // against the unlikely event of a race resulting in another card pointer to
+  // have already been written to the cache. In this case we will return
+  // card_ptr in favor of the other option, which would be starting over. This
+  // should be OK since card_ptr will likely be the older card already when/if
+  // this ever happens.
+  jbyte* previous_ptr = (jbyte*)Atomic::cmpxchg_ptr(card_ptr,
+                                                    &_hot_cache[masked_index],
+                                                    current_ptr);
+  return (previous_ptr == current_ptr) ? previous_ptr : card_ptr;
+}
+
+void G1HotCardCache::drain(CardTableEntryClosure* cl, uint worker_i) {
+  assert(default_use_cache(), "Drain only necessary if we use the hot card cache.");
+
+  assert(_hot_cache != NULL, "Logic");
+  assert(!use_cache(), "cache should be disabled");
+
+  while (_hot_cache_par_claimed_idx < _hot_cache_size) {
+    size_t end_idx = Atomic::add(_hot_cache_par_chunk_size,
+                                 &_hot_cache_par_claimed_idx);
+    size_t start_idx = end_idx - _hot_cache_par_chunk_size;
+    // The current worker has successfully claimed the chunk [start_idx..end_idx)
+    end_idx = MIN2(end_idx, _hot_cache_size);
+    for (size_t i = start_idx; i < end_idx; i++) {
+      jbyte* card_ptr = _hot_cache[i];
+      if (card_ptr != NULL) {
+        bool result = cl->do_card_ptr(card_ptr, worker_i);
+        assert(result, "Closure should always return true");
+      } else {
+        break;
+      }
+    }
+  }
+
+  // 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();
+}