 | | | high context switching and high load averages slowing down system | high context switching and high load averages slowing down system 2005-08-02 - By BQ
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On 8/2/05, Tom Sightler <ttsig@(protected)> wrote:
> On Mon, 2005-08-01 at 19:52 +1200, BQ wrote:
> > Now that we're on this subject ... is there any way to check on what
> > does the system spend time, when we see a lot of system CPU%?
>
> The only way that I am aware of to pinpoint system time is to use a tool
> like oprofile. I think for this to work well you have to have the
> kernel-debuginfo package installed. So far I've not had good success
> trying to get oprofile to work correctly with Redhat kernels but it may
> be my inexperience with the package.
Thanks for this Tom, it was a useful pointer.
I did some research around oprofile and I managed to get it working on
a RHEL3 system. I also found a very interesting web page which
explains some things about RH and oprofile:
http://people.redhat.com/wcohen/OProfileFAQ.txt.
As noted, you need RHEL 3 U2 and a SMP kernel to run oprofile.
However, now I got into other problems :) Some of the systems I'm
trying to debug are running under VMWare ESX and oprofile can't use
performance counter interface when ran under VMWare (probably because
VMWares virtual CPU doesn't support it). The workaround for this is to
use RTC mode, but I can't get that working.
Also, the kernel option mentioned on the web page above, "nortc"
doesn't seem to work at all for me (and I can't see anything mentioned
about it in the kernel documentation).
Does anyone have experience on running oprofile in RTC mode on RHEL machines?
Cheers,
BQ
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