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From "Nick Dimiduk (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-10403) Simplify offheap cache configuration
Date Fri, 24 Jan 2014 18:25:41 GMT

    [ https://issues.apache.org/jira/browse/HBASE-10403?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13881251#comment-13881251
] 

Nick Dimiduk commented on HBASE-10403:
--------------------------------------

Thanks for the comments [~zjushch]! I'll include them in the next patch. This was just a WIP
I wanted to share to see if you liked the direct. So you like disentangling BlockCache instantiation
into the static factory methods? Any complaint about the reflection business? Is there need
for a more "concrete" factory type class, etc?

Especially now in light of HBASE-6048 resurfacing, I think it's a good idea to decouple the
multilevel cache strategies from the implementations they wrap. This will be more invasive,
but it would allow a user to use CombinedBlockCache with SlabCache via configuration.

What do you think about the idea of "named" configurations? IE, including some preset configuration
by the name "BucketCache offheap". Is that too much?

> 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:
>  Set HBASE_REGIONSERVER_OPTS:
>   -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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