Messages in this thread | | | Subject | Re: Intel P6 vs P7 system call performance | From | Terje Eggestad <> | Date | 13 Dec 2002 10:21:11 +0100 |
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On tor, 2002-12-12 at 21:56, J.A. Magallon wrote: > On 2002.12.12 Mark Mielke wrote: > >On Thu, Dec 12, 2002 at 10:42:56AM +0100, Terje Eggestad wrote: > >> On ons, 2002-12-11 at 19:50, H. Peter Anvin wrote: > >> > Terje Eggestad wrote: > >> > > PS: rdtsc on P4 is also painfully slow!!! > >> > Now that's just braindead... > >> It takes about 11 cycles on athlon, 34 on PII, and a whooping 84 on P4. > >> For a simple op like that, even 11 is a lot... Really makes you wonder. > > > >Some of this discussion is a little bit unfair. My understanding of what > >Intel has done with the P4, is create an architecture that allows for > >higher clock rates. Sure the P4 might take 84, vs PII 34, but how many > >PII 2.4 Ghz machines have you ever seen on the market? > > > >Certainly, some of their decisions seem to be a little odd on the surface. > > > >That doesn't mean the situation is black and white. > > > > No. The situation is just black. Each day Intel processors are a bigger > pile of crap and less intelligent, but MHz compensate for the average > office user. Think of what could a P4 do if the same effort put on > Hz was put on getting cheap a cache of 4Mb or 8Mb like MIPSes have. Or > closer, 1Mb like G4s. > If syscalls take 300% time but processor is also 300% faster 'nobody > notices'.
Well, it does make sense if Intel optimized away rdtsc for more commonly used things, but even that don't seem to be the case. I'm measuring the overhead of doing a syscall on Linux (int 80) to be ~280 cycles on PIII, and Athlon, while it's 1600 cycles on P4.
TJ
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Terje Eggestad mailto:terje.eggestad@scali.no Scali Scalable Linux Systems http://www.scali.com
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