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From "Andrew Purtell (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-9857) Blockcache prefetch for HFile V3
Date Tue, 29 Oct 2013 17:36:32 GMT
Andrew Purtell created HBASE-9857:
-------------------------------------

             Summary: Blockcache prefetch for HFile V3
                 Key: HBASE-9857
                 URL: https://issues.apache.org/jira/browse/HBASE-9857
             Project: HBase
          Issue Type: Improvement
            Reporter: Andrew Purtell
            Priority: Minor


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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