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From "Andrew Purtell (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-9857) Blockcache prefetch option
Date Tue, 20 May 2014 16:04:39 GMT

     [ https://issues.apache.org/jira/browse/HBASE-9857?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Andrew Purtell updated HBASE-9857:
----------------------------------

    Attachment: HBASE-9857-trunk.patch

TestHCM passes locally looped 10 times.

Updated the trunk patch with one more Javadoc fix, I used the 0.98 tree to fix issues and
trunk had an additional nit, a misplaced close tag for a @link. 

> Blockcache prefetch option
> --------------------------
>
>                 Key: HBASE-9857
>                 URL: https://issues.apache.org/jira/browse/HBASE-9857
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Andrew Purtell
>            Assignee: Andrew Purtell
>            Priority: Minor
>             Fix For: 0.99.0, 0.98.3
>
>         Attachments: 9857.patch, 9857.patch, HBASE-9857-0.98.patch, HBASE-9857-trunk.patch,
HBASE-9857-trunk.patch
>
>
> Attached patch implements a prefetching function for HFile (v3) blocks, if indicated
by a column family or regionserver property. The purpose of this change is to as rapidly after
region open as reasonable warm the blockcache with all the data and index blocks of (presumably
also in-memory) table data, without counting those block loads as cache misses. Great for
fast reads and keeping the cache hit ratio high. Can tune the IO impact versus time until
all data blocks are in cache. Works a bit like CompactSplitThread. Makes some effort not to
stampede.
> I have been using this for setting up various experiments and thought I'd polish it up
a bit and throw it out there. If the data to be preloaded will not fit in blockcache, or if
as a percentage of blockcache it is large, this is not a good idea, will just blow out the
cache and trigger a lot of useless GC activity. Might be useful as an expert tuning option
though. Or not.



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