Messages in this thread | | | From | "M. Edward Borasky" <> | Subject | RE: smp cputime issues | Date | Wed, 2 Jan 2002 07:07:03 -0800 |
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> Second - you mention that you see the effect mainly on linear algebra > stuff. Could it be that you are memory bandwidth limited if you run two > of them together? Are you using Intel CPUs (my guess) which have the FSB > concept that may make memory bandwidth scaling a problem, or AMD Athlons > which use the Alpha/EV6 bus and should be a bit more friendly.
Hmmm ... linear algebra ... are you by any chance using Atlas? Atlas is highly optimized for the chips and as many other architectural features as it can discover, such as cache size. I'm sure a well-tuned Atlas application is quite capable of bending a machine to its own purposes, quite possibly to the discomfort of other users attempting to use the system. If the issue is sharing of resources between the linear algebra code and other users, perhaps the thing to do is get Atlas, if you're not currently using it, and then "nice" the linear algebra code.
I run Atlas on my (UP) 1.333 GHz Athlon Thunderbird and it screams. I can get 4+ GFLOPS in the 3DNOW 32-bit code and well over 1 GFLOP in 64 bits. -- M. Edward Borasky
znmeb@borasky-research.net http://www.borasky-research.net
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