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From "Nick Dimiduk (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-10403) Simplify offheap cache configuration
Date Thu, 23 Jan 2014 17:18:38 GMT

     [ https://issues.apache.org/jira/browse/HBASE-10403?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Nick Dimiduk updated HBASE-10403:

    Attachment: HBASE-10403.0.patch

[~zjushch] you noticed :)

Here's a sketch of the direction I'm moving. A couple observation:
 - the logic in CacheConfig#instantiateBlockCache is pretty convoluted, with the different
implementations all configured (or partially so) by the same if block
 - CombinedBlockCache and DoubleBlockCache are actually strategies for implementing a 2-level
cache. It would be nice, for instance, for a SlabCache user to take advantage of the CombinedBlockCache
 - A little cleanup here will let us experiment with other caching strategies. IE, I'd like
to try a 3-level cache with different implementations for index blocks (L0), decompressed
hot blocks (L1), and compressed cold/speculatively read blocks (L2).

> Simplify offheap cache configuration
> ------------------------------------
>                 Key: HBASE-10403
>                 URL: https://issues.apache.org/jira/browse/HBASE-10403
>             Project: HBase
>          Issue Type: Bug
>          Components: io
>            Reporter: Nick Dimiduk
>            Assignee: Nick Dimiduk
>            Priority: Minor
>         Attachments: HBASE-10403.0.patch
> The BucketCache (HBASE-7404) is a very nice piece of functionality which is hidden behind
complex configuration. Enabling it currently requires manual calculation of L1 cache. It'd
be nice to make this easier to use and conform better with the existing heap management tools
we already have.
> Turning it on currently requires explicitly setting LruBlockCache (L1) instance size
and IOEngine (L2) size, making sure that L1 size isn't too big vs global memstore and total
heap. This is further confused by hbase.bucketcache.size accepting a percentage of total heap
OR explicit size in MB. Enabling SlabCache is slightly easier in that it just accepts whatever
LruBlockCache is provided.
> Turning on BucketCache using off-heap mode could look like:
> hbase-env.sh:
>   -Xmx5000m
>   -XX:MaxDirectMemorySize=15000m
> hbase-site.xml:
>  - hbase.regionserver.global.memstore.size = 0.7
>  - hbase.regionserver.onheap.blockcache.size = 0.1
>  - hbase.regionserver.blockcache.impl = BucketCache
>  - hbase.bucketcache.ioengine = offheap
> The result being a CombinedCache instance with 500m LruBlockCache + 15000m ByteBufferIOEngine
running in direct mode.
> This example does a couple things (mostly for the admin):
>  - knows NOT to enable SlabCache
>  - s/hfile.block.cache.size/hbase.regionserver.onheap.blockcache.size/
>  - maintains the validity of HBaseConfiguration's existing check that global MemStore
+ LruBlockCache == 0.8
>  - maps "BucketCache" into meaning "a CombinedCache instance with these implementations
for L1 and L2."
>  - Figures out appropriate values for hbase.bucketcache.size and hbase.bucketcache.percentage.in.combinedcache

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