linux-kernel - Re: sched: deep power-saving states

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Message-Id: <1224705925.20069.76.camel@twins>
Date:	Wed, 22 Oct 2008 22:05:25 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Gregory Haskins <ghaskins@...ell.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>,
	Jon Masters <jonathan@...masters.org>
Subject: Re: sched: deep power-saving states

On Wed, 2008-10-22 at 12:55 -0700, Arjan van de Ven wrote:
> On Wed, 22 Oct 2008 21:49:52 +0200
> Peter Zijlstra <peterz@...radead.org> wrote:
> > 
> > This still leaves us with the worst case IRQ response as given by the
> > deepest C state. Which might be un-desirable.
> 
> that's a different problem in a different problem space.

Ah right, so the only point was trying to wake shallow cpus so as to try
and let deep cpus idle longer?

> > jcm was, once upon a time, working on dynamically changing the idle
> > routine, so that people who care about wakeup latency can run
> > idle=poll while their application runs, and the acpi C state stuff
> > when nobody cares.
> > 
> > This could of course then be tied into the PM QoS stuff Mark has been
> > doing.
> 
> in fact you already have this *exactly* today; this isn't future
> technology.

Interesting, what knob do I turn to get idle=poll dynamically?
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