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Liang Xie commented on HBASE-7404: ---------------------------------- [~liyin], so far as i know, most are them related with hdfs layer, the existing unfinished jiras(1. hedged read; 2 two wal writers) should be expected to alleviate somehow, but still have other works need to do, e.g. HDFS io qos or request priority(HDFS-5727). i am a late entry to the hbase+hdfs percentile latency tuning game, but i have an intuitive sense of still having lots of improvement space. > Bucket Cache:A solution about CMS,Heap Fragment and Big Cache on HBASE > ---------------------------------------------------------------------- > > Key: HBASE-7404 > URL: https://issues.apache.org/jira/browse/HBASE-7404 > Project: HBase > Issue Type: New Feature > Affects Versions: 0.94.3 > Reporter: chunhui shen > Assignee: chunhui shen > Fix For: 0.95.0 > > Attachments: 7404-0.94-fixed-lines.txt, 7404-trunk-v10.patch, > 7404-trunk-v11.patch, 7404-trunk-v12.patch, 7404-trunk-v13.patch, > 7404-trunk-v13.txt, 7404-trunk-v14.patch, BucketCache.pdf, > HBASE-7404-backport-0.94.patch, Introduction of Bucket Cache.pdf, > hbase-7404-94v2.patch, hbase-7404-trunkv2.patch, hbase-7404-trunkv9.patch > > > First, thanks @neil from Fusion-IO share the source code. > Usage: > 1.Use bucket cache as main memory cache, configured as the following: > –"hbase.bucketcache.ioengine" "heap" (or "offheap" if using offheap memory to > cache block ) > –"hbase.bucketcache.size" 0.4 (size for bucket cache, 0.4 is a percentage of > max heap size) > 2.Use bucket cache as a secondary cache, configured as the following: > –"hbase.bucketcache.ioengine" "file:/disk1/hbase/cache.data"(The file path > where to store the block data) > –"hbase.bucketcache.size" 1024 (size for bucket cache, unit is MB, so 1024 > means 1GB) > –"hbase.bucketcache.combinedcache.enabled" false (default value being true) > See more configurations from org.apache.hadoop.hbase.io.hfile.CacheConfig and > org.apache.hadoop.hbase.io.hfile.bucket.BucketCache > What's Bucket Cache? > It could greatly decrease CMS and heap fragment by GC > It support a large cache space for High Read Performance by using high speed > disk like Fusion-io > 1.An implementation of block cache like LruBlockCache > 2.Self manage blocks' storage position through Bucket Allocator > 3.The cached blocks could be stored in the memory or file system > 4.Bucket Cache could be used as a mainly block cache(see CombinedBlockCache), > combined with LruBlockCache to decrease CMS and fragment by GC. > 5.BucketCache also could be used as a secondary cache(e.g. using Fusionio to > store block) to enlarge cache space > How about SlabCache? > We have studied and test SlabCache first, but the result is bad, because: > 1.SlabCache use SingleSizeCache, its use ratio of memory is low because kinds > of block size, especially using DataBlockEncoding > 2.SlabCache is uesd in DoubleBlockCache, block is cached both in SlabCache > and LruBlockCache, put the block to LruBlockCache again if hit in SlabCache , > it causes CMS and heap fragment don't get any better > 3.Direct heap performance is not good as heap, and maybe cause OOM, so we > recommend using "heap" engine > See more in the attachment and in the patch -- This message was sent by Atlassian JIRA (v6.1.5#6160)