Re: Linux 2.6 on P4 recognized as only timer interrupt mode

[William C. <wc...@re...>]

John Sasso wrote:
> I have a Pentium 4 box running Fedora Core 3, which I installed oprofile
> 0.9.1 on. 'opcontrol -l' says that only timer interrupt mode is
> supported.  
> 
> Prior to installing oprofile I rebuilt the kernel to include in the
> config:
> 
> CONFIG_PROFILING=y
> CONFIG_OPROFILE=m
> 
> With the running kernel with profiling enabled, I built and installed
> oprofile.  According to the manual, I should be able to access various
> events through the P4, including cache misses.  So why is just timer
> interrupt mode supported?  I should not that my Dell Inspiron 5000e
> laptop w/ Pentium 3 also running FC3 has the same problem.

If you are using an UP kernel, OProfile falls back to using the timer 
interrupt mode because the local APIC is not set up. A quick solution 
in most cases is to use the SMP kernels because they have the APIC 
support, allowing used of the performance monitoring hardware. Otherwise 
you can compile a UP kernel with:

CONFIG_X86_UP_APIC=y
CONFIG_X86_LOCAL_APIC=y

-Will