Re: Disturbing wide variation in execution time

[Philippe Troin <phil@fifi.org>]

Sheo Shanker Prasad <ssp@creativeresearch.org> writes:

> I will appreciate your help in eliminating a disturbing wide
> variation (by a factors of 2 to 2.5) in the execution time of a test
> (execution benchmark) program under identical conditions even when
> the machine is freshly started (rebooted) and no other user program
> is running (not even e-mail or Internet browser).
> 
> I have a dual Opteron 250 (2.4 GHz) running SuSE 9.3 Pro & Linux
> version 2.6.11.4-21.7-smp (geeko@buildhost) (gcc version 3.3.5
> 20050117 (prerelease) (SUSE Linux)) #1 SMP Thu Jun 2 14:23:14 UTC
> 2005. The motherboard is Tyan Thunder K8W (S2885 ANRF) with AMI BIOS
> 
> The machine has 4GB of PC3200 DDR RAM, two dimms on each CPU.
> 
> The original machine bought from a vendor about 6 months ago. At
> that time it was running SuSE 9.1 Pro and the execution time for the
> same test program was consistently the same (around 2m 37s +/- a few
> %). Then the mother board failed and the machine went totally
> dead. The vendor then replaced the failed motherboard with a new
> Tyan Thunder K8W and installed the SuSE 9.3. I am not sure whether
> or not the AMI BIOS was also replaced.
> 
> When the repaired machine was started, I began to notice the
> disturbing wide variation and the frequect significant slow down of
> the machine as exhibited by the factor of 2 to 2.5 increased
> execution time of the test program as described above.  Sometimes it
> would be quite fast (executing at the original 2m 40s) and sometime
> a factor of 2.5 slow, and sometimes with speed in between.

8< snip >8

 1. Are you running an i386 kernel or an x86_64 kernel?

 2. Which BIOS version?

 3. Is node interleaving enabled in the BIOS?

Phil.