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Re: [PATCH] bump up nr_to_write in xfs_vm_writepage

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [PATCH] bump up nr_to_write in xfs_vm_writepage
From: Olaf Weber <olaf@xxxxxxx>
Date: Tue, 07 Jul 2009 13:37:05 +0200
Cc: Eric Sandeen <sandeen@xxxxxxxxxx>, linux-mm@xxxxxxxxx, "MASON, CHRISTOPHER" <CHRIS.MASON@xxxxxxxxxx>, xfs mailing list <xfs@xxxxxxxxxxx>
In-reply-to: <20090707101946.GB1934@xxxxxxxxxxxxx> (Christoph Hellwig's message of "Tue, 7 Jul 2009 06:19:46 -0400")
References: <4A4D26C5.9070606@xxxxxxxxxx> <bzyd48cc14d.fsf@xxxxxxxxxxxxxxxxxxxx> <20090707101946.GB1934@xxxxxxxxxxxxx>
User-agent: Gnus/5.1007 (Gnus v5.10.7) XEmacs/21.4.3 (irix)
Christoph Hellwig writes:
> On Tue, Jul 07, 2009 at 11:07:30AM +0200, Olaf Weber wrote:

>> If the nr_to_write calculation really yields a value that is too
>> small, shouldn't it be fixed elsewhere?

> In theory it should.  But given the amazing feedback of the VM people
> on this I'd rather make sure we do get the full HW bandwith on large
> arrays instead of sucking badly and not just wait forever.

So how do you feel about making the fudge factor tunable?  I don't
have a good sense myself of what the value should be, whether the
hard-coded 4 is good enough in general.

-- 
Olaf Weber                 SGI               Phone:  +31(0)30-6696752
                           Veldzigt 2b       Fax:    +31(0)30-6696799
Technical Lead             3454 PW de Meern  Vnet:   955-7151
Storage Software           The Netherlands   Email:  olaf@xxxxxxx

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