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

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Date:	Wed, 12 Sep 2012 08:43:04 +0900
From:	Namjae Jeon <linkinjeon@...il.com>
To:	Fengguang Wu <fengguang.wu@...el.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

2012/9/12, Fengguang Wu <fengguang.wu@...el.com>:
> 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
I missed server side setting.. I set dirty_background_centisecs to 1 sec.
> and can you give a comparison of different background writeback thresholds?
Okay, I will measure peformance per setting value of
dirty_background_centisecs in nfs server.

This is this patch's
> target use cases, after all.
Sure.
Thanks.
>
> Thanks,
> Fengguang
>
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