Mailing-List: contact hbase-dev-help@hadoop.apache.org; run by ezmlm
Precedence: bulk
Reply-To: hbase-dev@hadoop.apache.org
Message-ID: <1774631705.35711265148858768.JavaMail.jira@brutus.apache.org>
Date: Tue, 2 Feb 2010 22:14:18 +0000 (UTC)
From: "ryan rawson (JIRA)" <jira@apache.org>
To: hbase-dev@hadoop.apache.org
Subject: [jira] Assigned: (HBASE-2180) 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:all-tabpanel ]

ryan rawson reassigned HBASE-2180:
----------------------------------

    Assignee: ryan rawson

> 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: ryan rawson
>             Fix For: 0.21.0
>
>
> 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.