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https://issues.apache.org/jira/browse/HDFS-3697?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13421075#comment-13421075
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Brandon Li commented on HDFS-3697:
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Hey Todd, I've seen some performance improvement in my branch-1 test with the
fadvise support enabled. I think should commit it to branch-1.
The thing I am not sure is the readahead step size since I didn't try out with
enough workloads and step sizes in my tests. Given 4MB is good in your
experiments and it's also configurable, we can start with it.
I just feel it's not trivial sometimes to guess out a good step size
beforehand. :-) If it's possible in the future, we might want to make readahead
adjust its step size based on observed access pattern(however, tracking
multiple parallel streams' access pattern can be same challenging :-( ).
> Enable fadvise readahead by default
> -----------------------------------
>
> Key: HDFS-3697
> URL: https://issues.apache.org/jira/browse/HDFS-3697
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: data-node, performance
> Affects Versions: 3.0.0, 2.2.0-alpha
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Priority: Minor
> Fix For: 3.0.0, 2.2.0-alpha
>
> Attachments: hdfs-3697-branch-1.txt, hdfs-3697.txt, hdfs-3697.txt
>
>
> The fadvise features have been implemented for some time, and we've enabled
> them in production at a lot of customer sites without difficulty. I'd like to
> enable the readahead feature by default in future versions so that users get
> this benefit without any manual configuration required.
> The other fadvise features seem to be more workload-dependent and need
> further testing before enabling by default.
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