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sgovind 03-02-2004 04:49 PM

CPU Utilization too Low With Cycle Hungry App

I am running kernel v 2.4.21-99 with suse 9.0 distribution.
Machine: P4 3 GHz with HT and 800 MHz FSB. 1GB RAM.

I find (from top) that my CPU is never utilized more than ~55% even
when I am running my most cycle hungry apps (e.g. xcorr in matlab ).
Approx 40 % of the CPU is idle.

Running the same code on a different Linux box (not sure which
kernel) shows 98% utilization so I don't believe that the
app is the issue here.

I would like to increase the utilization to make my app faster.
Is it possible that there is a hard limit set somewhere in the config
to prevent me from using the CPU further? Or, is there something
else I can do?



hw-tph 03-04-2004 07:56 AM

To make full use of your hyperthreading processor you should use a SMP kernel. SMP mean symmetrical multi-processing and usually means multi-CPU systems, but HT systems emulate two CPU's so try SMP to make use of the "second" CPU as well.


sgovind 03-09-2004 12:14 PM

Thanks for the info Hakan.

Actually I am running an SMP kernel. I didn't mention the whole
kernel version. It is 2.4.21-99-smp4G. That kernel should be
optimized for HT right?



hw-tph 03-09-2004 07:29 PM

I don't know if 2.4.21 had hyperthreading-specific support, but using a Xeon 2.4.21 kernel should make the system HT-aware. However, I do not have first hand experience with HT processors and I don't know when it was first introduced in the stable kernel. Is compiling the 2.6.3 kernel from scratch an option? If you do you could try whatever configurations and tricks you want.


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