Re: 2.6.17.1 new perfmon code base, libpfm, pfmon available

[Grant Grundler <iod00d@hp.com>]

On Tue, Jun 27, 2006 at 07:32:04AM -0700, Stephane Eranian wrote:
...
> > 5006 hardware interrupts in 10 seconds, 16359 interrupt-disable events =>
> > the kernel disabled interrupts 11353 times for critical sections.  To get
> > useful results it looks like booting with idle=poll and disabling cpufreq
> > is needed, though, since interrupts_masked_cycles (non-edge mode) counts
> > even when the CPU is halted:
> 
> Yes, I think you need to be careful with the idle thread, some events may or
> may not count when going low-power. I think it is best to avoid going
> low-power for measurements.

Any benchmarking that involves IA64 idle thread is strongly reccomended
to use "nohalt" option. It's about a 15-20% performance difference
on some interrupt intensive benchmarks (e.g. netperf TCP_RR).

If someone has measured the delta for other architectures that
go into a "low power" state in idle thread, I'd be grateful if
they posted the results or mailed them to me.

thanks,
grant