Date: Tue, 15 Feb 2011 09:29:19 -0500
From: Vivek Goyal <vgoyal@redhat.com>
To: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Cc: Chad Talbott <ctalbott@google.com>, Jens Axboe <axboe@kernel.dk>,
        Shaohua Li <shaohua.li@intel.com>, lkml <linux-kernel@vger.kernel.org>,
        Divyesh Shah <dpshah@google.com>
Subject: Re: [PATCH 0/6 v4] cfq-iosched: Introduce CFQ group hierarchical
 scheduling and "use_hierarchy" interface
Message-ID: <20110215142919.GD27296@redhat.com>
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On Tue, Feb 15, 2011 at 11:13:48AM +0800, Gui Jianfeng wrote:
> 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.

Ok, that's fine. We can implement boosting logic for groups later.

I think Chad's patch of remembering generation should help in getting service
differentiation even with idiling disabled.

Thanks
Vivek
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