Re: Measuring tools - top and interrupts

[Mike Galbraith <efault@gmx.de>]

On Sat, 2006-06-24 at 11:21 +0200, Björn Steinbrink wrote:
> On 2006.06.24 08:26:23 +0200, Mike Galbraith wrote:
> > On Sat, 2006-06-24 at 07:59 +0200, Mike Galbraith wrote:
> > > On Thu, 2006-06-22 at 09:58 -0700, Danial Thom wrote:
> > > 
> > > > And 75K pps may not be "much", but its still at
> > > > least 10% of what the system can handle, so it
> > > > should measure around a 10% load. 2.4 measures
> > > > about 12% load. So the only conclusion is that
> > > > load accounting is broken in 2.6.
> > > 
> > > For UP, yes.  SMP kernel accounts irq processing time properly.
> 
> Do you actually see 100% idle?

Yes.

>  On both, UP and SMP, I see non-zero hi/si
> values using "top". With IO-APIC enabled, I see only non-zero si values
> for my tg3 NICs, and non-zero hi and si values for the nVidia NIC. With
> IO-APIC disabled, I also see a non-zero hi value for the tg3 on UP,
> guess that's normal... But I never see 100% idle while flooding the box
> with pings.

I have APIC and IO-APIC enabled.

> > For my little box, the below cures it.
> > 
> > --- linux-2.6.17x/arch/i386/kernel/apic.c.org	2006-06-24 08:08:46.000000000 +0200
> > +++ linux-2.6.17x/arch/i386/kernel/apic.c	2006-06-24 08:09:16.000000000 +0200
> > @@ -1175,9 +1175,7 @@ EXPORT_SYMBOL(switch_ipi_to_APIC_timer);
> >  inline void smp_local_timer_interrupt(struct pt_regs * regs)
> >  {
> >  	profile_tick(CPU_PROFILING, regs);
> > -#ifdef CONFIG_SMP
> >  	update_process_times(user_mode_vm(regs));
> > -#endif
> >  
> >  	/*
> >  	 * We take the 'long' return path, and there every subsystem
> 
> The non-SMP call to update_process_times() is in do_timer_interrupt_hook(),
> so I guess the above is not the Right Thing to do.

Ah, there it is.  That's what I was looking for.  I figured that doing
what I did had to be wrong, but tried it for grins anyway... was pretty
surprised when it worked (kinda).

	-Mike