Messages in this thread | | | From | (Linus Torvalds) | Subject | Re: Intel P6 vs P7 system call performance | Date | Mon, 9 Dec 2002 17:48:45 +0000 (UTC) |
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In article <200212090830.gB98USW05593@flux.loup.net>, Mike Hayward <hayward@loup.net> wrote: > >I have been benchmarking Pentium 4 boxes against my Pentium III laptop >with the exact same kernel and executables as well as custom compiled >kernels. The Pentium III has a much lower clock rate and I have >noticed that system call performance (and hence io performance) is up >to an order of magnitude higher on my Pentium III laptop. 1k block IO >reads/writes are anemic on the Pentium 4, for example, so I'm trying >to figure out why and thought someone might have an idea.
P4's really suck at system calls. A 2.8GHz P4 does a simple system call a lot _slower_ than a 500MHz PIII.
The P4 has problems with some other things too, but the "int + iret" instruction combination is absolutely the worst I've seen. A 1.2GHz Athlon will be 5-10 times faster than the fastest P4 on system call overhead.
HOWEVER, the P4 is really good at a lot of other things. On average, a P4 tends to perform quite well on most loads, and hyperthreading (if you have a Xeon or one of the newer desktop CPU's) also tends to work quite well to smooth things out in real life.
In short: the P4 architecture excels at some things, and it sucks at others. It _mostly_ tends to excel more than suck.
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