From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Wilcox Date: Fri, 24 Oct 2003 15:35:43 +0000 Subject: Re: Itanium2@900MHz slower than alpha@666MHz ? Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org On Fri, Oct 24, 2003 at 05:14:50PM +0200, Ionut Georgescu wrote: > I am puzzled about the speed of a zx2000 workstation with a 900Mhz CPU. > According to the SPECfp2000 benchmarks, this workstation should be about > twice as fast as a DS10 alpha workstation and according to the fftw2 > benchmarks at least 50% faster (double precision, real data, 256x256 FFT > transforms). I ran the fftw2 benchmark myself and I could reproduce the > data on fftw.org > > However, my program is about 40% slower on the zx2000 as on the alpha. > It only does some Fourier transforms (fftw2, 256x256) and some matrix > operations (sort of an inner product). Both fftw2 and the program have > been compiled with ecc -O2 -ipo -limf. ecc is Version 7.1, Build > 20030307. This strikes me as possibly being a cache size thing. Do you have the 1.5MB cache or 3MB cache version of the 900MHz Itanium? The DS10 specs I found at http://www.spec.org/cpu2000/results/res2000q3/cpu2000-20000630-00134.asc say it has a 2MB cache, so if your data set fits in a 2MB cache and not in a 1.5MB cache, that would be a possible cause. What kind of fluctuations do you see between runs? Linux doesn't do cache-colouring, so high variation between runs could indicate a close-to-edge-of-cache scenario. -- "It's not Hollywood. War is real, war is primarily not about defeat or victory, it is about death. I've seen thousands and thousands of dead bodies. Do you think I want to have an academic debate on this subject?" -- Robert Fisk