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

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Date:	Thu, 5 Nov 2015 19:55:10 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Peter Zijlstra <peterz@...radead.org>
cc:	Arjan van de Ven <arjan@...ux.intel.com>,
	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, Peter Zijlstra wrote:
> On Thu, Nov 05, 2015 at 07:28:50AM -0800, Arjan van de Ven wrote:
> > 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....
> 
> The current code is/was broken, but when I tried fixing it, tglx
> objected to the entire approach yes...
> 
> Thomas, no arm twisting can convince you to reconsider the fake idle
> task approach?

As long as the thing just calls mwait or whatever twisting might be
successful, but I'm not going to change my mind on something calling
into the idle related routines (timers, rcu, etc..) and violates all
sensible assumptions we make in that code. It's complex enough already
and we really do not need subtle wreckage by half baken and unreviewed
drivers to add more complexity.

Thanks,

	tglx



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