Re: Intel P6 vs P7 system call performance

From: Terje Eggestad (
Date: Fri Dec 13 2002 - 16:57:55 EST

I haven't tried the vsyscall patch, but there was a sysenter patch
floating around that I tried. It reduced the syscall overhead with 1/3
to 1/4, but I never tried it on P4.

FYI: Just note that I say overhead, which I assume to be the time it
take to do someting like getpid(), write(-1,...), select(-1, ...) (etc
that is immediatlely returned with -EINVAL by the kernel).
Since the kernel do execute a quite afew instructions beside the
int/iret sysenter/sysexit, it's an assumption that the int 80 is the

I would be nice if someone bothered to try this on an windoze box.
(Un)fortunatly I live in a windoze free environment. :-)


On Fri, 2002-12-13 at 16:58, Ville Herva wrote:
    On Fri, Dec 13, 2002 at 10:21:11AM +0100, you [Terje Eggestad] wrote:
> 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.
    Just out of interest, how much would sysenter (or syscall on amd) cost,
    then? (Supposing it can be feasibly implemented.)
    I think I heard WinXP (W2k too?) is using sysenter?
    -- v --


Terje Eggestad Scali Scalable Linux Systems

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