Re: [PATCH RFC cgroup/for-3.7] cgroup: mark subsystems with brokenhierarchy support and whine if cgroups are nested for them

From: Tejun Heo
Date: Wed Sep 12 2012 - 13:09:32 EST

Hello, Glauber.

On Wed, Sep 12, 2012 at 01:56:09PM +0400, Glauber Costa wrote:
> "Being able to provide hierarchical support" is an example of such
> restrictions. And as Vivek said himself, for the CFQ case should be doable.

Yeah, it's mostly that cfq was already a hairy monster before blkcg
was added to it and unfortunately we didn't make it any cleaner in the
process and blkcg itself has a lot of other issues including being
completely broken w.r.t. writeback writes. In addition there are two
sub-controllers - the cfq one and blk-throttle. So, it's just that
there are too many scary things to do and not enough man power or
maybe interest. I hope we could just declare cgroup isn't supported
on block devices but that doesn't seem feasible at this point either.

I might / probably work on it and am hoping to coerce Vivek into it
too. If you wanna jump in, please be my guest.


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