linux-kernel - Re: [PATCH 0/6 v4] cfq-iosched: Introduce CFQ group hierarchical scheduling and "use

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Date:	Tue, 15 Feb 2011 11:13:48 +0800
From:	Gui Jianfeng <guijianfeng@...fujitsu.com>
To:	Vivek Goyal <vgoyal@...hat.com>
CC:	Chad Talbott <ctalbott@...gle.com>, Jens Axboe <axboe@...nel.dk>,
	Shaohua Li <shaohua.li@...el.com>,
	lkml <linux-kernel@...r.kernel.org>,
	Divyesh Shah <dpshah@...gle.com>
Subject: Re: [PATCH 0/6 v4] cfq-iosched: Introduce CFQ group hierarchical
 scheduling and "use_hierarchy" interface

Vivek Goyal wrote:
> On Sat, Feb 12, 2011 at 02:08:54PM +0800, Gui Jianfeng wrote:
>> Vivek Goyal wrote:
>>> On Thu, Feb 10, 2011 at 03:45:45PM +0800, Gui Jianfeng wrote:
>>>> Hi
>>>>
>>>> Previously, I posted a patchset to add support of CFQ group hierarchical scheduling
>>>> in the way that it puts all CFQ queues in a hidden group and schedules with other 
>>>> CFQ group under their parent. The patchset is available here,
>>>> http://lkml.org/lkml/2010/8/30/30
>>>>
>>>> Vivek think this approach isn't so instinct that we should treat CFQ queues
>>>> and groups at the same level. Here is the new approach for hierarchical 
>>>> scheduling based on Vivek's suggestion. The most big change of CFQ is that
>>>> it gets rid of cfq_slice_offset logic, and makes use of vdisktime for CFQ
>>>> queue scheduling just like CFQ group does. But I still give cfqq some jump 
>>>> in vdisktime based on ioprio, thanks for Vivek to point out this. Now CFQ 
>>>> queue and CFQ group use the same scheduling algorithm. 
>>>>
>>>> "use_hierarchy" interface is now added to switch between hierarchical mode
>>>> and flat mode. It works as memcg.
>>>>
>>>> --
>>>> V3 -> V4 Changes:
>>>> - Take io class into account when calculating the boost value.
>>>> - Refine the vtime boosting logic as Vivek's Suggestion.
>>> Hi Gui,
>>>
>>> What testing did you do to make sure that this vtime boosting logic is working
>>> and is good replacement for slice_offset() logic for cfqq?
>>>
>>> Secondly, did you get a chance to look at chad's patch of keeping track
>>> of previous assigned vdisktime and keeping track of genrations. I think
>>> his patch is going to coflict with yours, so one of you will have to
>>> make adjustments. I think both the boost logic and keeping track of generation
>>> logic can be combined.
>> Hi Vivek,
>>
>> For the time being, boosting logic only works for cfq queue, and keepinging track of
>> generation works for cfq group.
>> I think when we introduce boosting logic for cfq group, we can combine these two logic
>> together.
> 
> Ok, I am assuming that now you are introducing another patch in the series
> to get boosting logic working for groups also.
> 
> Also, it might be easier to test it with group_idle=0, as right now groups
> don't preempt each other.

Vivek,

If you don't object, I'd like to introduce this in a seperate patch when this series
gets merged. For I don't want to add more complexity for this seires. ;) 
I'll post v5.

Thanks,
Gui

> 
> Thanks
> Vivek
> 
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