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https://issues.apache.org/jira/browse/HADOOP-2758?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12569166#action_12569166
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rangadi edited comment on HADOOP-2758 at 2/14/08 7:36 PM:
---------------------------------------------------------------
Thanks for the detailed review Konstatin.
Just a clarification to the readers: except 4, rest are not introduced by this
patch. I will try to fix some of them.
When this protocol was first introduced, it was described in the jira
(HADOOP-1134). Since then, it has evolved. I agree that it will be better to
have the ascii diagrams in the code comments itself. I will surely add that.
was (Author: rangadi):
Thanks for the detailed review Konstatin.
Just a clarification to the readers: except 4 and 7, rest are not introduced by
this patch. I will try to fix some of them.
When this protocol was first introduced, it was described in the jira
(HADOOP-1134). Since then, it has evolved. I agree that it will be better to
have the ascii diagrams in the code comments itself. I will surely add that.
> Reduce memory copies when data is read from DFS
> -----------------------------------------------
>
> Key: HADOOP-2758
> URL: https://issues.apache.org/jira/browse/HADOOP-2758
> Project: Hadoop Core
> Issue Type: Improvement
> Components: dfs
> Reporter: Raghu Angadi
> Assignee: Raghu Angadi
> Fix For: 0.17.0
>
> Attachments: HADOOP-2758.patch
>
>
> Currently datanode and client part of DFS perform multiple copies of data on
> the 'read path' (i.e. path from storage on datanode to user buffer on the
> client). This jira reduces these copies by enhancing data read protocol and
> implementation of read on both datanode and the client. I will describe the
> changes in next comment.
> Requirement is that this fix should reduce CPU used and should not cause
> regression in any benchmarks. It might not improve the benchmarks since most
> benchmarks are not cpu bound.
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