linux-kernel - Re: [RFC PATCH 3/3] sched: introduce synchronized idle injection

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Message-ID: <alpine.DEB.2.11.1511051944400.4032@nanos>
Date:	Thu, 5 Nov 2015 19:47:46 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Arjan van de Ven <arjan@...ux.intel.com>
cc:	Peter Zijlstra <peterz@...radead.org>,
	Jacob Pan <jacob.jun.pan@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Paul Turner <pjt@...gle.com>, Len Brown <len.brown@...el.com>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	Andi Kleen <andi.kleen@...el.com>,
	Rafael Wysocki <rafael.j.wysocki@...el.com>
Subject: Re: [RFC PATCH 3/3] sched: introduce synchronized idle injection

On Thu, 5 Nov 2015, Arjan van de Ven wrote:
> On 11/5/2015 6:33 AM, Peter Zijlstra wrote:
> 
> > It just grates at me a bit that we have to touch hot paths for such
> scenarios :/
> 
> well we have this as a driver right now that does not touch hot paths,
> but it seems you and tglx also hate that approach with a passion....

Right. It's a horror to deal with tasks which try to impersonate idle
while actually running as highest priority task in the system. We
really want the scheduler to know about it. Yes, we probably have to
pay the price for some extra check in the hot path, but that's way
more sensible than figuring out how 'want to be idle' RT tasks
wreckage the world and some more.

Thanks,

	tglx
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