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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7755) Experiment with LAB in BlockEndcoding
Date Mon, 04 Feb 2013 06:28:12 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7755?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13570011#comment-13570011

Lars Hofhansl commented on HBASE-7755:

Hey Matt... Yeah. I'm seeing this as a 0.94-only change, whereas the bigger work on HBASE-7323
et al is the right long term fix.

> Experiment with LAB in BlockEndcoding
> -------------------------------------
>                 Key: HBASE-7755
>                 URL: https://issues.apache.org/jira/browse/HBASE-7755
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>         Attachments: 7755-0.94-WORK_IN_PROGRESS.txt
> I was looking at and profiling the BlockEncoding code to figure out how to make it faster.
One issue that jumped out was we call ByteBuffer.allocate(...) for each single KV.
> As an experiment I tried using the MemStoreLAB code to allocate those buffers.
> Here are some preliminary numbers, all scanning 10m rows (all in cache):
> * no encoding: 5.2s
> * FAST_DIFF without patch: 7.3s
> * FAST_DIFF with patch and small LAB: 4.1s
> * FAST_DIFF with patch and large LAB: 11s
> So this is very sensitive to the right sizing of the LAB.
> Need to do a bit more testing, but it seems that there is a chance to actually make scanning
with block encoding faster than without!

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