Mailing-List: contact hbase-dev-help@hadoop.apache.org; run by ezmlm
Precedence: bulk
Reply-To: hbase-dev@hadoop.apache.org
Message-ID: <1515176036.527821267115668034.JavaMail.jira@brutus.apache.org>
Date: Thu, 25 Feb 2010 16:34:28 +0000 (UTC)
From: "Erik Rozendaal (JIRA)" <jira@apache.org>
To: hbase-dev@hadoop.apache.org
Subject: [jira] Commented: (HBASE-2180) Bad random read performance from
 synchronizing hfile.fddatainputstream
In-Reply-To: <555111303.35671265148738898.JavaMail.jira@brutus.apache.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit


    [ https://issues.apache.org/jira/browse/HBASE-2180?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12838399#action_12838399 ] 

Erik Rozendaal commented on HBASE-2180:
---------------------------------------

I saw both CLOSE_WAIT and TIME_WAIT. Maybe CLOSE_WAIT was in the majority. Connections were mostly to the data node.

$ uname -a
Linux inrdb-worker1.ripe.net 2.6.18-164.11.1.el5 #1 SMP Wed Jan 20 07:32:21 EST 2010 x86_64 x86_64 x86_64 GNU/Linux

They do go after a while, since after a few of the "Cannot assign requested address" exceptions the server starts working again.

Unfortunately I'll be away for the weekend and won't be able to investigate further. I wonder why so many connections are being opened so quickly that the server runs out of ports within a few minutes of starting the gets/puts?

> Bad random read performance from synchronizing hfile.fddatainputstream
> ----------------------------------------------------------------------
>
>                 Key: HBASE-2180
>                 URL: https://issues.apache.org/jira/browse/HBASE-2180
>             Project: Hadoop HBase
>          Issue Type: Bug
>            Reporter: ryan rawson
>            Assignee: stack
>             Fix For: 0.20.4, 0.21.0
>
>         Attachments: 2180-v2.patch, 2180.patch
>
>
> deep in the HFile read path, there is this code:
>     synchronized (in) {
>       in.seek(pos);
>       ret = in.read(b, off, n);
>     }
> this makes it so that only 1 read per file per thread is active. this prevents the OS and hardware from being able to do IO scheduling by optimizing lots of concurrent reads. 
> We need to either use a reentrant API (pread may be partially reentrant according to Todd) or use multiple stream objects, 1 per scanner/thread.

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