linux-kernel - Re: [PATCH v4 6/7] sched: add function nr_running_cpu to expose number of tasks running on cpu

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Message-ID: <20140715133627.GS3588@twins.programming.kicks-ass.net>
Date:	Tue, 15 Jul 2014 15:36:27 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Tim Chen <tim.c.chen@...ux.intel.com>
Cc:	Herbert Xu <herbert@...dor.apana.org.au>,
	"H. Peter Anvin" <hpa@...or.com>,
	"David S.Miller" <davem@...emloft.net>,
	Ingo Molnar <mingo@...nel.org>,
	Chandramouli Narayanan <mouli@...ux.intel.com>,
	Vinodh Gopal <vinodh.gopal@...el.com>,
	James Guilford <james.guilford@...el.com>,
	Wajdi Feghali <wajdi.k.feghali@...el.com>,
	Jussi Kivilinna <jussi.kivilinna@....fi>,
	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
	tj@...nel.org
Subject: Re: [PATCH v4 6/7] sched: add function nr_running_cpu to expose
 number of tasks running on cpu

On Mon, Jul 14, 2014 at 09:15:04PM +0200, Peter Zijlstra wrote:
> I still loathe all the async work, because it makes a mockery of
> accounting etc.. but that's a story for another day I suppose :-(

So, just to expand on this, we're already getting 'bug' reports because
worker threads are not cgroup aware. If work gets generated inside some
cgroup, the worker doesn't care and runs the worker thread wherever
(typically the root cgroup).

This means that the 'work' escapes the cgroup confines and creates
resource inversion etc. The same is of course true for nice and RT
priorities.

TJ, are you aware of this and/or given it any throught?

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