linux-kernel - Re: A few questions and issues with dynticks, NOHZ and powertop

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Date:	Sun, 4 Apr 2010 12:47:08 +0200
From:	Dominik Brodowski <linux@...inikbrodowski.net>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Adam Belay <abelay@...ell.com>, Len Brown <len.brown@...el.com>
Cc:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Arjan van de Ven <arjan@...ux.intel.com>
Subject: Re: A few questions and issues with dynticks, NOHZ and powertop

Hey,

On Sat, Apr 03, 2010 at 04:53:26PM -0700, Dmitry Torokhov wrote:
> On Sun, Apr 04, 2010 at 12:33:28AM +0200, Dominik Brodowski wrote:
> > 
> > 4) SynPS/2 touchpad: 
> > Why does moving the touchpad lead to sooo many IRQs? I can't look as fast
> > as the mouse pointer seems to get new data:
> >   62,5% (473,1)       <interrupt> : PS/2 keyboard/mouse/touchpad 
> > 
> 
> 80 pps @ 6 bytes/packet = 480 interrupts/sec.
> 
> You can try using psmouse.rate=40 to limit it to 40 pps which should
> bring it to the rate of standard PS/2 mouse at the expense of
> sensitivity...

as a sidenote: if we know -- like here -- that the next IRQ will be issued
soon, in approximately 1.75 ms (well, at least on my system), might it make
sense to make tick_nohz_get_sleep_length() smarter to know about this?

Best,
	Dominik
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