| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| /** |
| * Provides implementations of {@link org.apache.hadoop.hbase.io.hfile.HFile} and HFile |
| * {@link org.apache.hadoop.hbase.io.hfile.BlockCache}. Caches are configured (and instantiated) |
| * by {@link org.apache.hadoop.hbase.io.hfile.CacheConfig}. See head of the |
| * {@link org.apache.hadoop.hbase.io.hfile.CacheConfig} class for constants that define |
| * cache options and configuration keys to use setting cache options. Cache implementations |
| * include the default, native on-heap {@link org.apache.hadoop.hbase.io.hfile.LruBlockCache} and a |
| * {@link org.apache.hadoop.hbase.io.hfile.bucket.BucketCache} that has a bunch of deploy formats |
| * including acting as a L2 for LruBlockCache -- when a block is evicted from LruBlockCache, it |
| * goes to the BucketCache and when we search a block, we look in both places -- or, the |
| * most common deploy type, |
| * using {@link org.apache.hadoop.hbase.io.hfile.CombinedBlockCache}, BucketCache is used as |
| * a host for data blocks with meta blocks in an instance of LruBlockCache. BucketCache |
| * can also be onheap, offheap, and file-backed. |
| * |
| * <h1>Which BlockCache should I use?</h1> |
| * By default LruBlockCache is on. If you would like to cache more, and offheap (offheap |
| * usually means less GC headache), try enabling * BucketCache. Fetching will always |
| * be slower when fetching from BucketCache but latencies tend to be less erratic over time |
| * (roughly because GC is less). See Nick Dimiduk's |
| * <a href="http://www.n10k.com/blog/blockcache-101/">BlockCache 101</a> for some numbers. |
| * |
| * <h1>Enabling {@link org.apache.hadoop.hbase.io.hfile.bucket.BucketCache}</h1> |
| * See the HBase Reference Guide <a href="http://hbase.apache.org/book.html#enable.bucketcache">Enable BucketCache</a>. |
| * |
| */ |
| package org.apache.hadoop.hbase.io.hfile; |
