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From "Daryn Sharp (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-9260) Improve the performance and GC friendliness of NameNode startup and full block reports
Date Fri, 31 Mar 2017 18:30:42 GMT

    [ https://issues.apache.org/jira/browse/HDFS-9260?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15951459#comment-15951459

Daryn Sharp commented on HDFS-9260:

I have no doubt this patch "works".  If you are collecting GC metrics check if you see elevation
or spikes in frequency or cpu over historic levels.  Roughly what are the specs for the "highest
scale" you have observed?

This blocks HDFS-7967 which is a critical feature for our clusters - It's been a deployment
blocker since 2.6.  The balancer is unusable with 500 million to over 1 billion replicas on
dense storages.  I have detailed in a comment on HDFS-7967 that getBlocks will take hundreds
of ms.  Sustaining 20-40k average ops/sec is impossible.

Rolling upgrades also already place very high GC pressure on the NN, some narrowly escaping
a full GC.  I'm very worried if the NN has to re-sort FBRs during the upgrade.

I'd like to stop internally maintaining HDFS-7967 and let the community benefit.  May we please

> Improve the performance and GC friendliness of NameNode startup and full block reports
> --------------------------------------------------------------------------------------
>                 Key: HDFS-9260
>                 URL: https://issues.apache.org/jira/browse/HDFS-9260
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: datanode, namenode, performance
>    Affects Versions: 2.7.1
>            Reporter: Staffan Friberg
>            Assignee: Staffan Friberg
>             Fix For: 3.0.0-alpha1
>         Attachments: FBR processing.png, HDFS-7435.001.patch, HDFS-7435.002.patch, HDFS-7435.003.patch,
HDFS-7435.004.patch, HDFS-7435.005.patch, HDFS-7435.006.patch, HDFS-7435.007.patch, HDFS-9260.008.patch,
HDFS-9260.009.patch, HDFS-9260.010.patch, HDFS-9260.011.patch, HDFS-9260.012.patch, HDFS-9260.013.patch,
HDFS-9260.014.patch, HDFS-9260.015.patch, HDFS-9260.016.patch, HDFS-9260.017.patch, HDFS-9260.018.patch,
HDFSBenchmarks2.zip, HDFSBenchmarks.zip, HDFS Block and Replica Management 20151013.pdf
> This patch changes the datastructures used for BlockInfos and Replicas to keep them sorted.
This allows faster and more GC friendly handling of full block reports.
> Would like to hear peoples feedback on this change.

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