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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-13871) ITestS3AInputStreamPerformance.testTimeToOpenAndReadWholeFileBlocks performance on branch-2.8 awful
Date Thu, 08 Dec 2016 20:06:59 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-13871?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15733274#comment-15733274

Steve Loughran commented on HADOOP-13871:

Video appears to show that everything is coming in out of order. 

Having a tight timeout and expanded rx buffer isn't enough, as there's enough capacity for
OOO packets to be buffered, so less discarded, hence pauses waiting for other bits of data
to get resent.

This almost argues for a smaller Rx buffer so it blockes faster, triggering timeouts. But
that's some bits of TCP there that I'm not knowledgeable of. After all: ooo packets do appear
to be arriving, so the channel is live, just not delivering data to the caller.

We could collect effective read stats (as the test does) within the input stream...just do
nanotime counts before and after each read, and build up long-term stats of the current stream,
which can then be queried. although they could be aggregated, I tried that with the output
and it doesn't work: if a network is full due to to many parallel connections, the effective
bandwidth of each one is low; aggregating via just total bytes/total elapsed time doesn't
work, as it generates false statistics implying very low bandwidth, rather than a saturated,
shared, network link

> ITestS3AInputStreamPerformance.testTimeToOpenAndReadWholeFileBlocks performance on branch-2.8
> ---------------------------------------------------------------------------------------------------
>                 Key: HADOOP-13871
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13871
>             Project: Hadoop Common
>          Issue Type: Sub-task
>          Components: fs/s3
>    Affects Versions: 2.8.0, 2.9.0, 3.0.0-alpha2
>         Environment: landsat bucket from the UK
>            Reporter: Steve Loughran
>            Assignee: Steve Loughran
>         Attachments: HADOOP-13871-001.patch, org.apache.hadoop.fs.s3a.scale.ITestS3AInputStreamPerformance-output.txt
> The ITestS3AInputStreamPerformance.testTimeToOpenAndReadWholeFileBlocks takes 15s on
branch-2, but is now taking minutes.
> This is a regression, and it's surfacing on some internal branches too. Even where the
code hasn't changed. -It does not happen on branch-2, which has a later SDK.-

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