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https://issues.apache.org/jira/browse/HBASE-10403?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13882146#comment-13882146
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chunhui shen commented on HBASE-10403:
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As my personal thought, I'd like to fix the usage of BlockCache, Two much
combination would confuse the general users.
In current configuration implementation with patch, user should config the
class name of "hbase.block.cache.impl". For me, class name is hard to remember.
Also setting it as 'CombinedBlockCache' or 'DoubleBlockCache' seems unfamiliar.
So, should we use the 'type' instead of 'class name', just like Compression
algorithm and DataBlockEncoding algorithm.
For example,
hbase.block.cache.type='LruCache', default value, use LruBlockCache.
hbase.block.cache.type='BucketCache', according to the value of
'hbase.bucketcache.ioengine', construct the BlockCache.('heap' or 'offheap'
use CombinedBlockCache, 'file' use BucketCache directly as the L2 cache)
hbase.block.cache.type='SlabCache', use DoubleBlockCache.
Finally, I think the patch is quite well now. If we could set an familiar type
value for BlockCache instead of detail class name, it will be better if I'm a
general user.
> 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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