Messages in this thread | | | Date | Mon, 5 Apr 2010 13:52:13 -0700 | From | Dmitry Torokhov <> | Subject | Re: A few questions and issues with dynticks, NOHZ and powertop |
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On Mon, Apr 05, 2010 at 10:41:43PM +0200, Dominik Brodowski wrote: > On Sun, Apr 04, 2010 at 08:42:43PM -0700, Arjan van de Ven wrote: > > On 4/4/2010 3:47, Dominik Brodowski wrote: > > >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? > > > > yes and no. > > > > if you are very sure (95%+ or so) then absolutely it needs to know about this > > so that the C state selection code can make a better decision. > > Right now it tries to look at history to guess this delay. > > > > Unfortunately we do not currently have such a concept in the code to make this > > work... but it'd be really nice to have. > > Dmitry, are we "very sure" in this touchpad case? >
Psmouse driver tries to not rely on any timing data really... But yes, we do expect the next interrupt to arrive "shortly" and I guess the driver could do some data gathering to collect average time between interrupts. The question is - is it worth it?
-- Dmitry
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