linux-kernel - Re: [PATCH 1/2] writeback: add dirty_background

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Date:	Wed, 12 Sep 2012 07:25:37 +0800
From:	Fengguang Wu <fengguang.wu@...el.com>
To:	Namjae Jeon <linkinjeon@...il.com>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	Namjae Jeon <namjae.jeon@...sung.com>,
	Vivek Trivedi <t.vivek@...sung.com>
Subject: Re: [PATCH 1/2] writeback: add dirty_background_time per bdi variable

On Wed, Sep 12, 2012 at 08:12:40AM +0900, Namjae Jeon wrote:
> >>
> >> To be frank, no realistic NFS servers will use USB disk as backing
> >> storage. So that rational for reducing "initial" delays is weak.
> >> Continuous write performance to HDD is much more important. Do you
> >> have numbers for that?
> >
> > Actually, we use USB HDD and USB Flash devices at NFS server.
> > There can be other similar users as well. So it might be useful to
> > provide this tuning feature other.
> > As default value is zero, it is disabled by default and it should not
> > impact normal writeback.
> >
> > I will share large file writes test result on NFS client on USB HDD
> > with/without tuning with patch.
> Hi. Wu.
> I share 1GB continous write test result.
> 
> -> create a 1000 MB file
> For continuous write - create 1 GB file
> 
>  RecSize   WriteSpeed
> 10485760   10.47MB/sec
>  1048576   10.35MB/sec
>   524288   10.48MB/sec
>   262144   10.48MB/sec
>   131072   10.52MB/sec
>    65536   10.56MB/sec
>    32768   10.64MB/sec
>    16384   10.31MB/sec
>     8192   10.52MB/sec
>     4096   10.45MB/sec
> 
> I will update changelog in patch.

Thanks! What's the server side setting and can you give a comparison
of different background writeback thresholds? This is this patch's
target use cases, after all.

Thanks,
Fengguang
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