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Message-ID: <20120323114913.GB24489@umich.edu>
Date:	Fri, 23 Mar 2012 07:49:13 -0400
From:	Jim Rees <rees@...ch.edu>
To:	Vivek Trivedi <vtrivedi018@...il.com>
Cc:	"Myklebust, Trond" <Trond.Myklebust@...app.com>,
	linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	Namjae Jeon <linkinjeon@...il.com>, amit.sahrawat83@...il.com
Subject: Re: NFS: low read/stat performance on small files

Vivek Trivedi wrote:

  204800 bytes (200.0KB) copied, 0.027074 seconds, 7.2MB/s
  Read speed for 200KB file is 7.2 MB

  104857600 bytes (100.0MB) copied, 9.351221 seconds, 10.7MB/s
  Read speed for 100MB file is 10.7 MB
  
  As you see read speed for 200KB file is only 7.2MB/sec while it is
  10.7 MB/sec when we read 100MB file.
  Why there is so much difference in read performance ?
  Is there any way to achieve high read speed for small files ?

That seems excellent to me.  204800 bytes at 11213252 per sec would be 18.2
msec, so your per-file overhead is around 9 msec.  The disk latency alone
would normally be more than that.
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