Mailing-List: contact hdfs-issues-help@hadoop.apache.org; run by ezmlm
Precedence: bulk
Reply-To: hdfs-issues@hadoop.apache.org
Message-ID: <28491065.251561278552352175.JavaMail.jira@thor>
Date: Wed, 7 Jul 2010 21:25:52 -0400 (EDT)
From: "Todd Lipcon (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Subject: [jira] Commented: (HDFS-1140) Speedup INode.getPathComponents
In-Reply-To: <22042367.5701273528950268.JavaMail.jira@thor>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit


    [ https://issues.apache.org/jira/browse/HDFS-1140?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12886177#action_12886177 ] 

Todd Lipcon commented on HDFS-1140:
-----------------------------------

Hmm, TestFileAppend4 passes for me on a trunk checkout. It seems like some test that ran prior to it didn't close resources properly? Does it fail on your machine?

> Speedup INode.getPathComponents
> -------------------------------
>
>                 Key: HDFS-1140
>                 URL: https://issues.apache.org/jira/browse/HDFS-1140
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>    Affects Versions: 0.22.0
>            Reporter: Dmytro Molkov
>            Assignee: Dmytro Molkov
>            Priority: Minor
>             Fix For: 0.22.0
>
>         Attachments: HDFS-1140.2.patch, HDFS-1140.3.patch, HDFS-1140.4.patch, HDFS-1140.patch
>
>
> When the namenode is loading the image there is a significant amount of time being spent in the DFSUtil.string2Bytes. We have a very specific workload here. The path that namenode does getPathComponents for shares N - 1 component with the previous path this method was called for (assuming current path has N components).
> Hence we can improve the image load time by caching the result of previous conversion.
> We thought of using some simple LRU cache for components, but the reality is, String.getBytes gets optimized during runtime and LRU cache doesn't perform as well, however using just the latest path components and their translation to bytes in two arrays gives quite a performance boost.
> I could get another 20% off of the time to load the image on our cluster (30 seconds vs 24) and I wrote a simple benchmark that tests performance with and without caching.

-- 
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.