linux-kernel - Re: [PATCH -tip 26/32] sched: Add a second-level tag for nested CGroup usecase

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Message-ID: <X8pZlZgSq4aoIqoF@mtj.duckdns.org>
Date:   Fri, 4 Dec 2020 10:45:25 -0500
From:   Tejun Heo <tj@...nel.org>
To:     Josh Don <joshdon@...gle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
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Subject: Re: [PATCH -tip 26/32] sched: Add a second-level tag for nested
 CGroup usecase

Hello,

On Thu, Dec 03, 2020 at 04:51:42PM -0800, Josh Don wrote:
> > So me the color thing reads like an end-run around the cgroup hierarchy.
> 
> Restructuring the cgroup resource hierarchy to incorporate the trust
> domains is not necessarily trivial (as is the case for us).  I agree
> though that that would be the ideal correct solution from the cgroup
> hierarchy perspective.

Yeah, it sure isn't. We (FB) had to go through a couple iterations and it's
looking like we need another adjustment, so I fully agree that these are
painful but at the same time I don't think it's difficult to see that how
piling up workarounds in the lowest layer is not the right thing to do. The
workarounds you guys need would be different from what we or others would
need. The kernel can't be maintained in any sustainable manner if we keep
piling on disjoint workarounds on it. Please consider long term trajectory
when proposing interface changes which often boils down to identifying the
core features which must be supported by the interface.

Thanks.

-- 
tejun