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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-9488) Improve performance for small scan
Date Wed, 11 Sep 2013 17:14:54 GMT

    [ https://issues.apache.org/jira/browse/HBASE-9488?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13764506#comment-13764506
] 

stack commented on HBASE-9488:
------------------------------

Agree that we should add this -- as it is progress -- but that yes, it would be better if
you did not have to explicitly flip the switch.

We probably should flip and enable pread as default since it seems we want it more often than
not especially as gains are not that great and seek+read improperly used causes large degradation.
 We can flip on seek+read doing compactions as our fb brothers and sisters have done (they
also added pooling to dfsclient it seems).

Ditto for working to make it so scan is one rpc only.

                
> 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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