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https://issues.apache.org/jira/browse/HDFS-2465?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13137374#comment-13137374
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Eli Collins commented on HDFS-2465:
-----------------------------------
Looked at the patch, think this is a reasonable first DN-wide heuristic.
Comments follow:
* There isn't any config that enables syncBehindWrites in BlockerRecevier.
* Would it be more clear to express LONG_READ_THRESHOLD in terms of a multiple
of the packet size or the IO file buffer size? Seems like the host readahead
should match the implicit HDFS readahead.
* In BlockerSender#sendBlock by the 1st fadvise a comment like "advice applies
to the entire file" would help
* Nit: add _BYTES to LONG_READ_THRESHOLD and CACHE_DROP_INTERVAL.
Otherwise looks great.
> Add HDFS support for fadvise readahead and drop-behind
> ------------------------------------------------------
>
> Key: HDFS-2465
> URL: https://issues.apache.org/jira/browse/HDFS-2465
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: data-node
> Affects Versions: 0.23.0
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Attachments: hdfs-2465.txt
>
>
> This is the HDFS side of HADOOP-7714. The initial implementation is heuristic
> based and should be considered experimental, as discussed in the parent JIRA.
> It should be off by default until better heuristics, APIs, and tuning
> experience is developed.
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