Re: Degregated I/O Performance since 3.4 - Regression in 3.4?

[Tobias Geiger <tobias.geiger@vido.info>]

Am Mittwoch, 25. April 2012, 17:05:26 schrieb Stefano Stabellini:
> On Wed, 25 Apr 2012, Tobias Geiger wrote:
> > Am Mittwoch, 25. April 2012, 15:44:44 schrieb Stefano Stabellini:
> > > On Wed, 25 Apr 2012, Tobias Geiger wrote:
> > > > Hi,
> > > > 
> > > > 9846ff10 was it!
> > > > after reverting it, performance returned to normal.
> > > 
> > > Argh, that is one of my commits, and is supposed to be a performance
> > > improvement!
> > > 
> > > I couldn't reproduce the regression you are seeing but the patch is
> > > pretty simple, so just by reading it again I think I manage to spot a
> > > possible error. Could you please try again with the appended patch?
> > > 
> > > 
> > > 
> > > diff --git a/drivers/xen/events.c b/drivers/xen/events.c
> > > index 4b33acd..0a8a17c 100644
> > > --- a/drivers/xen/events.c
> > > +++ b/drivers/xen/events.c
> > > @@ -274,7 +274,7 @@ static unsigned int cpu_from_evtchn(unsigned int
> > > evtchn)
> > > 
> > >  static bool pirq_check_eoi_map(unsigned irq)
> > >  {
> > > 
> > > -	return test_bit(irq, pirq_eoi_map);
> > > +	return test_bit(pirq_from_irq(irq), pirq_eoi_map);
> > > 
> > >  }
> > >  
> > >  static bool pirq_needs_eoi_flag(unsigned irq)
> > 
> > Looks good;
> > 
> > I applied it to 3.4.0-rc4 and the performance went to normal again.
> 
> I'll add your tested-by if it is OK for you

of course - thanks!