linux-kernel - Re: [RFC 3/3] blk-throttling: detect inactive cgroup

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Date:	Thu, 21 Jan 2016 16:09:53 -0500
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Shaohua Li <shli@...com>
Cc:	linux-kernel@...r.kernel.org, axboe@...nel.dk, tj@...nel.org,
	jmoyer@...hat.com, Kernel-team@...com, linux-block@...r.kernel.org
Subject: Re: [RFC 3/3] blk-throttling: detect inactive cgroup

On Thu, Jan 21, 2016 at 01:05:43PM -0800, Shaohua Li wrote:
> On Thu, Jan 21, 2016 at 03:44:05PM -0500, Vivek Goyal wrote:
> > On Wed, Jan 20, 2016 at 09:49:19AM -0800, Shaohua Li wrote:
> > > If a cgroup is inactive for some time, it should be excluded from
> > > bandwidth calculation.
> > 
> > I am not sure why do we require this patch. If group is inactive, it
> > will not be on service tree and will not contribute to weight hence
> > will not contrinute to share.
> 
> The share calculation is based on existing cgroups (with this patch,
> existing active cgroups). a cgroup is on service tree when it has pending
> bios, right? Not having pending bios isn't a condition we should exclude
> a cgroup.

If a cgroup is not doing IO and is not active, then it should not be
part of disk share calculation. Once cgroup is active, it should get
its fair share and reduce the share of peers.

Thanks
Vivek