linux-kernel - Re: [Documentation] State of CPU controller in cgroup v2

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Message-ID: <20160930090603.GD29207@mtj.duckdns.org>
Date:   Fri, 30 Sep 2016 11:06:03 +0200
From:   Tejun Heo <tj@...nel.org>
To:     Mike Galbraith <umgwanakikbuti@...il.com>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Ingo Molnar <mingo@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        kernel-team@...com,
        "open list:CONTROL GROUP (CGROUP)" <cgroups@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Paul Turner <pjt@...gle.com>, Li Zefan <lizefan@...wei.com>,
        Linux API <linux-api@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [Documentation] State of CPU controller in cgroup v2

Hello, Mike.

On Sat, Sep 10, 2016 at 12:08:57PM +0200, Mike Galbraith wrote:
> On Fri, 2016-09-09 at 18:57 -0400, Tejun Heo wrote:
> > > > As for your example, who performs the cgroup setup and configuration,
> > > > the application itself or an external entity?  If an external entity,
> > > > how does it know which thread is what?
> > > 
> > > In my case, it would be a little script that reads a config file that
> > > knows all kinds of internal information about the application and its
> > > threads.
> > 
> > I see.  One-of-a-kind custom setup.  This is a completely valid usage;
> > however, please also recognize that it's an extremely specific one
> > which is niche by definition.
> 
> This is the same pigeon hole you placed Google into.  So Google, my
> (also decidedly non-petite) users, and now Andy are all sharing the one
> of a kind extremely specific niche.. it's becoming a tad crowded.

I wasn't trying to say that these use cases are small in numbers when
added up, but that they're all isolated in their own small silos.
Facebook has a lot of these usages too but they're almost all mutually
exculsive.  Making workloads share machines or even adding resource
conrol for base system operations afterwards is extremely difficult.
There are cases these adhoc approaches make sense but insisting that
this is all there is to resource control is short-sighted.

Thanks.

-- 
tejun