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From "Andrew Purtell (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-14205) RegionCoprocessorHost System.nanoTime() performance bottleneck
Date Tue, 11 Aug 2015 18:56:47 GMT

    [ https://issues.apache.org/jira/browse/HBASE-14205?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14682302#comment-14682302
] 

Andrew Purtell commented on HBASE-14205:
----------------------------------------

On HBASE-13420 the suggestion (from John Leach) was remove entirely. I agree with that approach,
but Srikanth and I both thought that would amount to a functional regression if done in a
patch release. Yeah, the 'function' is a performance concern. The remainder of the issue focused
on mitigating John's issue. We could also turn it off with a config toggle I suppose and see
if someone complains about a functional regression. In any case, why not just remove this
entirely from 1.2 and up? 

> RegionCoprocessorHost System.nanoTime() performance bottleneck
> --------------------------------------------------------------
>
>                 Key: HBASE-14205
>                 URL: https://issues.apache.org/jira/browse/HBASE-14205
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Jan Van Besien
>            Priority: Critical
>             Fix For: 2.0.0, 1.2.0, 1.3.0
>
>
> The tracking of execution time of coprocessor methods introduced in HBASE-11516 introduces
2 calls to System.nanoTime() per coprocessor method per coprocessor. This is resulting in
a serious performance bottleneck in certain scenarios.
> For example consider the scenario where many rows are being ingested (PUT) in a table
which has multiple coprocessors (we have up to 20 coprocessors). This results in 8 extra calls
to System.nanoTime() per coprocessor (prePut, postPut, postStartRegionOperation and postCloseRegionOperation)
which has in total (i.e. times 20) been seen to result in a 50% increase of execution time.
> I think it is generally considered bad practice to measure execution times on such a
small scale (per single operation). Also note that measurements are taken even for coprocessors
that do not even have an actual implementation for certain operations, making the problem
worse.



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