[jira] [Commented] (HBASE-1177) Delay when client is located on the same node as the regionserver

["Lars Hofhansl (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-1177?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13279943#comment-13279943 ] 

Lars Hofhansl commented on HBASE-1177:
--------------------------------------

If this caused by Nagles it should happen regardless of whether the DN is local to the RS or not, right? (Or maybe we're seeing an issue different from the OP's).

                
> Delay when client is located on the same node as the regionserver
> -----------------------------------------------------------------
>
>                 Key: HBASE-1177
>                 URL: https://issues.apache.org/jira/browse/HBASE-1177
>             Project: HBase
>          Issue Type: Bug
>          Components: performance
>    Affects Versions: 0.19.0
>         Environment: Linux 2.6.25 x86_64
>            Reporter: Jonathan Gray
>              Labels: noob
>         Attachments: Contribution of getClosest to getRow time.jpg, Contribution of next to getRow time.jpg, Contribution of seekTo to getClosest time.jpg, Elapsed time of RowResults.readFields.jpg, ReadDelayTest.java, RowResults.readFields zoomed.jpg, getRow + round-trip vs # columns.jpg, getRow times.jpg, screenshot-1.jpg, screenshot-2.jpg, screenshot-3.jpg, screenshot-4.jpg, zoom of columns vs round-trip blowup.jpg
>
>
> During testing of HBASE-80, we uncovered a strange 40ms delay for random reads.  We ran a series of tests and found that it only happens when the client is on the same node as the RS and for a certain range of payloads (not specifically related to number of columns or size of them, only total payload).  It appears to be precisely 40ms every time.
> Unsure if this is particular to our architecture, but it does happen on all nodes we've tried.  Issue completely goes away with very large payloads or moving the client.
> Will post a test program tomorrow if anyone can test on a different architecture.
> Making a blocker for 0.20.  Since this happens when you have an MR task running local to the RS, and this is what we try to do, might also consider making this a blocker for 0.19.1.

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