linux-kernel - Re: [RFC] nfs: use 2*rsize readahead size

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Message-ID: <20100224052409.GI16175@discord.disaster>
Date:	Wed, 24 Feb 2010 16:24:09 +1100
From:	Dave Chinner <david@...morbit.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Trond Myklebust <Trond.Myklebust@...app.com>,
	"linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	Linux Memory Management List <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC] nfs: use 2*rsize readahead size

On Wed, Feb 24, 2010 at 12:43:56PM +0800, Wu Fengguang wrote:
> On Wed, Feb 24, 2010 at 12:24:14PM +0800, Dave Chinner wrote:
> > On Wed, Feb 24, 2010 at 02:29:34PM +1100, Dave Chinner wrote:
> > > That's doing a cached read out of the server cache, right? You
> > > might find the results are different if the server has to read the
> > > file from disk. I would expect reads from the server cache not
> > > to require much readahead as there is no IO latency on the server
> > > side for the readahead to hide....
> > 
> > FWIW, if you mount the client with "-o rsize=32k" or the server only
> > supports rsize <= 32k then this will probably hurt throughput a lot
> > because then readahead will be capped at 64k instead of 480k....
> 
> I should have mentioned that in changelog.. Hope the updated one
> helps.

Sorry, my fault for not reading the code correctly.

Cheers,

Dave.
-- 
Dave Chinner
david@...morbit.com
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