linux-kernel - Re: [PATCH] IO Controller: Add per-device weight and ioprio

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Date:	Wed, 20 May 2009 11:41:19 -0400
From:	"IKEDA, Munehiro" <m-ikeda@...jp.nec.com>
To:	Gui Jianfeng <guijianfeng@...fujitsu.com>
CC:	Vivek Goyal <vgoyal@...hat.com>, nauman@...gle.com,
	dpshah@...gle.com, lizf@...fujitsu.com, mikew@...gle.com,
	fchecconi@...il.com, paolo.valente@...more.it,
	jens.axboe@...cle.com, ryov@...inux.co.jp, fernando@....ntt.co.jp,
	s-uchida@...jp.nec.com, taka@...inux.co.jp, jmoyer@...hat.com,
	dhaval@...ux.vnet.ibm.com, balbir@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org, righi.andrea@...il.com,
	agk@...hat.com, dm-devel@...hat.com, snitzer@...hat.com,
	akpm@...ux-foundation.org
Subject: Re: [PATCH] IO Controller: Add per-device weight and ioprio_class
 handling

Gui Jianfeng wrote:
> IKEDA, Munehiro wrote:
>> Hi Gui,
>>
>> Gui Jianfeng wrote:
>>> Hi Vivek,
>>>
>>> This patch enables per-cgroup per-device weight and ioprio_class
>>> handling.
>>> A new cgroup interface "policy" is introduced. You can make use of
>>> this file to configure weight and ioprio_class for each device in a
>>> given cgroup.
>>> The original "weight" and "ioprio_class" files are still available. If
>>> you
>>> don't do special configuration for a particular device, "weight" and
>>> "ioprio_class" are used as default values in this device.
>>>
>>> You can use the following format to play with the new interface.
>>> #echo DEV:weight:ioprio_class > /patch/to/cgroup/policy
>>> weight=0 means removing the policy for DEV.
>>>
>>> Examples:
>>> Configure weight=300 ioprio_class=2 on /dev/hdb in this cgroup
>>> # echo /dev/hdb:300:2 > io.policy
>>> # cat io.policy
>>> dev weight class
>>> /dev/hdb 300 2
>> Users can specify a device file of a partition for io.policy.
>> In this case, io_policy_node::dev_name is set as a name of the
>> partition device like /dev/sda2.
>>
>> ex)
>>  # cd /mnt/cgroup
>>  # cat /dev/sda2:500:2 > io.policy
>>  # echo io.policy
>>    dev weight class
>>    /dev/sda2 500 2
>>
>> I believe io_policy_node::dev_name should be set a generic
>> device name like /dev/sda.
>> What do you think about it?
> 
>   Hi Ikeda-san,
> 
>   Sorry for the late reply. Thanks for pointing this out. 
>   yes, it does the right thing but shows a wrong name. 
>   IMHO, Inputing a sigle partition should not be allowed since the
>   policy is disk basis. So how about the following patch?
> 
> Signed-off-by: Gui Jianfeng <guijianfeng@...fujitsu.com>
> ---
> diff --git a/block/elevator-fq.c b/block/elevator-fq.c
> index 1a0ca07..b620768 100644
> --- a/block/elevator-fq.c
> +++ b/block/elevator-fq.c
> @@ -1650,6 +1650,9 @@ static int devname_to_devnum(const char *buf, dev_t *dev)
>  		return -ENODEV;
>  
>  	disk = get_gendisk(bdev->bd_dev, &part);
> +	if (part)
> +		return -EINVAL;
> +
>  	*dev = MKDEV(disk->major, disk->first_minor);
>  	bdput(bdev);
> 

It looks nicer and reasonable for me.
Thanks!



-- 
IKEDA, Munehiro
 NEC Corporation of America
   m-ikeda@...jp.nec.com


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