Intel Xeon 1.7GHz: King of the High End?

Linux Performance

For Linux benchmarking, we used the classic kernel compilation tests. Kernel compilation tests have the advantage of being able to specify the number of processes to run concurrently as well as being both CPU and memory bandwidth bound. The Xeon with its quad-pumped FSB should make much better use of its memory bandwidth than the Pentium III which hopefully is demonstrated by the compilation times.

This test is easily reproducable on your own machine. We used the latest released Linux kernel, 2.4.4, with default options obtained by running 'make menuconfig' and exiting without changing any values. You could also type 'make config' and hold the return key down to get the same results. To specify the number of concurrent processes make will spawn for compiling, use the -j flag such as: 'make -j 2 vmlinux' which specifies two processes.

To limit the ammount of CPU time held up in disk usage, we made sure to double check Red Hat's disk settings and step them up to 32bit I/O and UltraDMA mode 4. To do this, we used the following hdparm command:

hdparm -c1 -d1 -k1 -X68 /dev/hda

Note that I/O access will still measure into these tests, but since we used the same drive on every machine, it should not be a factor favoring either machine. Also, 512MB of RAM should be enough to ensure that make, gcc and a good number of the core include files stay in Linux's file system cache.

After we finished all the Athlon benchmarks, we went to start on the Xeon scores and ran into a wall. Neither the Red Hat 7.1 install kernel nor their install CDs would boot. Neither would the 2.4.4 kernel. Upgrading to 2.4.4-ac9 finally worked and we managed to test with that. So, note that these scores were obtained using two different kernels.

What is very interesting about this is that the 2.4.4 kernel we compiled was compiled to support Pentium 4 class CPUs. Thus, the kernel already included support for the base Pentium 4. The Xeon does not vary enough to warrant a failure, and the i860 chipset is only a slightly modified i850. Still, this is brand new hardware and maybe it's asking too much to expect older kernels to run on first try.

The Athlon benchmarks are meant to provide a basis for comparison between platforms. If you'll notice, the performance of the Single processor Athlon platform doesn't increase as the number of concurrent processes increases. This is because there is only one CPU to handle the processes, so adding more doesn't help the single CPU out any. Dual AMD vs. Intel benchmarks will have to wait for a future article.

In comparison to the Pentium 4 and the Athlon, the Pentium III is rather FSB and memory bandwidth starved with only 1GB/s available. We actually expected the Xeon to show a larger improvement moving from 1-process to 2-process bulids in
comparison with the Pentium III. Here, we can see that both the Pentium III and Xeon took just under 60% as long as a single process build. This tells us that that remaining 10% must be related to inherent inefficiencies associated with SMP and that a kernel compile must not stress FSB and memory bandwidth enough to show the Pentium III's weakness.