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

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Message-ID: <20100405205455.GB4576@core.coreip.homeip.net>
Date:	Mon, 5 Apr 2010 13:54:56 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Dominik Brodowski <linux@...inikbrodowski.net>, power@...host.org,
	linux-kernel@...r.kernel.org,
	Arjan van de Ven <arjan@...ux.intel.com>
Subject: Re: A few questions and issues with dynticks, NOHZ and powertop

On Sun, Apr 04, 2010 at 12:35:15PM +0200, Dominik Brodowski wrote:
> Hi Dmitry,
> 
> 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...
> 
> Excellent. Maybe this could be added to the Tips&Tricks section at the
> Powertop website?
> 

Do not see the point - the touchpad does not generate interrupts while
you are not touching it and while you are touching it the machine is not
going to sleep. The only reason I see for lowering the rate is if your
keyboard contrioller can not handle it (some Toshibas couldn't).

> I guess obtaining all 6 bytes at once is not really possible?

No. i8042 is byte-oriented.

> It
> seems a new byte only appears ~1.75 ms after the last one, at least on my
> notebook, so waiting for this is not an option...
> 
> Best,
> 	Dominik
> 
> 
> PS: Dmitry, got something small for you in return:

Thanks, will apply.
> 
> 
> [PATCH] i8042: spelling fix
> 
> Signed-off-by: Dominik Brodowski <linux@...inikbrodowski.net>
> 
> diff --git a/drivers/input/serio/i8042.c b/drivers/input/serio/i8042.c
> index 9302ba0..f61233e 100644
> --- a/drivers/input/serio/i8042.c
> +++ b/drivers/input/serio/i8042.c
> @@ -38,7 +38,7 @@ MODULE_PARM_DESC(noaux, "Do not probe or use AUX (mouse) port.");
>  
>  static bool i8042_nomux;
>  module_param_named(nomux, i8042_nomux, bool, 0);
> -MODULE_PARM_DESC(nomux, "Do not check whether an active multiplexing conrtoller is present.");
> +MODULE_PARM_DESC(nomux, "Do not check whether an active multiplexing controller is present.");
>  
>  static bool i8042_unlock;
>  module_param_named(unlock, i8042_unlock, bool, 0);

-- 
Dmitry
--
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