From: Josh Boyer <jwboyer@linux.vnet.ibm.com>
To: kvm-ppc@vger.kernel.org
Subject: Re: [kvm-ppc-devel] Oprofile kvmppc - mini howto and
Date: Fri, 04 Apr 2008 15:33:18 +0000 [thread overview]
Message-ID: <1207323199.6518.0.camel@weaponx> (raw)
On Fri, 2008-04-04 at 08:46 -0500, Hollis Blanchard wrote:
> On Friday 04 April 2008 06:01:41 Christian Ehrhardt wrote:
> > Note the bad thing, atm oprofile on ppc440 seems not to have hw perf
> > counters available. Therefore it is covered with the fallback
> > timer-interrupt. But this has drawbacks: =>from the oprfile info page:
> > "In 2.6 kernels on CPUs without OProfile support for the hardware
> > performance counters, the driver falls back to using the timer interrupt
> > for profiling. Like the RTC mode in 2.4 kernels, this is not able to
> > profile code that has interrupts disabled. Note that there are no
> > configuration parameters for setting this, unlike the RTC and hardware
> > performance counter setup."
> >
> > So oprofile works but without real cpu perf counters it will be nearly
> > useless, because we have interrupts disabled in most code we want to
> > profile. I need to look out for some beta support (or write my own) for
> > ppc440 cpu perf counters to enable that for us :(
>
> I don't see any performance counters in the 440 user manuals.
There aren't any that I'm aware of. The only performance monitor I've
seen on 440 chip is for the PLB, and I don't believe that is useful for
your purposes.
josh
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