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https://issues.apache.org/jira/browse/HBASE-1177?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12710021#action_12710021
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Jonathan Gray commented on HBASE-1177:
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I did misunderstand part of your explanation. The jump in CS is just in this
delayed case.
But we should still not close the issue. It's not the context switching caused
by additional concurrency that hurts us then, it's context switching because
there's something else happening. The jump in context switches is a symptom of
something happening differently along the way for this special range of
payloads.
> 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: Hadoop HBase
> Issue Type: Bug
> Affects Versions: 0.19.0
> Environment: Linux 2.6.25 x86_64
> Reporter: Jonathan Gray
> Assignee: Jim Kellerman
> Priority: Blocker
> Fix For: 0.20.0
>
> Attachments: ReadDelayTest.java
>
>
> 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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