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List:       oprofile-list
Subject:    Re: Falls back to timer interrupt mode in a Pentium III desktop
From:       William Cohen <wcohen () redhat ! com>
Date:       2005-03-31 14:23:02
Message-ID: 424C07C6.5010605 () redhat ! com
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vijeta johri wrote:
> 
> I am trying to use oprofile on a Pentium III CPU 1400MHz desktop but I can't
> configure any events there as oprofile is running in timer interrupt mode. I
> think it should have hardware performance counters, but oprofile is not
> detecting them. Any ideas?
> Thanks,
> Vijeta

To use the performance monitoring hardware on the processor the 
interrupt routing APIC hardware needs to be available. On uniprocessor 
kernels CONFIG_X86_UP_APIC needs to be set. If the APIC interrupt 
hardware is not available, OProfile falls back on the timer interrupt 
mechanism.

A quick work around for this is to install the SMP kernel, which has the 
APIC support compiled in. The SMP kernels works on most machines. One 
notable exception to this is the Red Hat SMP kernels do not work on 
Pentium M processors because they do not have PAE support.

-Will


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