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From "Anoop Sam John (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-9553) Pad HFile blocks to a fixed size before placing them into the blockcache
Date Tue, 17 Sep 2013 07:00:58 GMT

    [ https://issues.apache.org/jira/browse/HBASE-9553?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13769273#comment-13769273
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Anoop Sam John commented on HBASE-9553:
---------------------------------------

What abt when the on-cache encoding is enabled. Will the HFile block sizes can change much
from block to block?
                
> Pad HFile blocks to a fixed size before placing them into the blockcache
> ------------------------------------------------------------------------
>
>                 Key: HBASE-9553
>                 URL: https://issues.apache.org/jira/browse/HBASE-9553
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>
> In order to make it easy on the garbage collector and to avoid full compaction phases
we should make sure that all (or at least a large percentage) of the HFile blocks as cached
in the block cache are exactly the same size.
> Currently an HFile block is typically slightly larger than the declared block size, as
the block will accommodate that last KV on the block. The padding would be a ColumnFamily
option. In many cases 100 bytes would probably be a good value to make all blocks exactly
the same size (but of course it depends on the max size of the KVs).
> This does not have to be perfect. The more blocks evicted and replaced in the block cache
are of the exact same size the easier it should be on the GC.
> Thoughts?

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