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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-9488) Improve performance for small scan
Date Thu, 12 Sep 2013 04:00:52 GMT

    [ https://issues.apache.org/jira/browse/HBASE-9488?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13765150#comment-13765150
] 

Lars Hofhansl commented on HBASE-9488:
--------------------------------------

I don't see how we can reliably default this. (I have the same problem for the parallel scanning
stuff). In order to do that we need statistics (we're actually working on this here - on the
backburner).

The only scans we know for sure will be small are META scans.
                
> Improve performance for small scan
> ----------------------------------
>
>                 Key: HBASE-9488
>                 URL: https://issues.apache.org/jira/browse/HBASE-9488
>             Project: HBase
>          Issue Type: Improvement
>          Components: Client, Performance, Scanners
>            Reporter: chunhui shen
>            Assignee: chunhui shen
>             Fix For: 0.98.0, 0.94.13
>
>         Attachments: hbase-9488-94-v3.patch, HBASE-9488-trunk.patch, HBASE-9488-trunkV2.patch,
HBASE-9488-trunkV3.patch, HBASE-9488-trunkV4.patch, HBASE-9488-trunkV4.patch, mergeRpcCallForScan.patch,
test results.jpg
>
>
> review board:
> https://reviews.apache.org/r/14059/
> *Performance Improvement*
> Test shows about 1.5~3X improvement for small scan where limit<=50 under cache hit
ratio=100%.
> See more performance test result from the picture attachment
> *Usage:*
> Scan scan = new Scan(startRow,stopRow);
> scan.setSmall(true);
> ResultScanner scanner = table.getScanner(scan);
> Set the new 'small' attribute as true for scan object, others are the same
> Now, one scan operation would call 3 RPC at least:
> openScanner();
> next();
> closeScanner();
> I think we could reduce the RPC call to one for small scan to get better performance
> Also using pread is better than seek+read for small scan (For this point, see more on
HBASE-7266)
> Implements such a small scan as the patch, and take the performance test as following:
> a.Environment´╝Ü
> patched on 0.94 version
> one regionserver; 
> one client with 50 concurrent threads;
> KV size:50/100;
> 100% LRU cache hit ratio;
> Random start row of scan
> b.Results:
> See the picture attachment
>  

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