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    SubjectRe: Intel P6 vs P7 system call performance
    It get even worse with Hammer. When you run hammer in compatibility mode
    (32 bit app on a 64 bit OS) the sysenter is an illegal instruction.
    Since Intel don't implement syscall, there is no portable sys*
    instruction for 32 bit apps. You could argue that libc hides it for you
    and you just need libc to test the host at startup (do I get a sigill if
    I try to do getpid() with sysenter? syscall? if so we uses int80 for
    syscalls). But not all programs are linked dyn.

    Too bad really, I tried the sysenter patch once, and the gain (on PIII
    and athlon) was significant.

    Fortunately the 64bit libc for hammer uses syscall.

    PS: rdtsc on P4 is also painfully slow!!!


    On man, 2002-12-09 at 20:46, H. Peter Anvin wrote:
    > Followup to: <>
    > By author: Dave Jones <>
    > In newsgroup:
    > >
    > > On Mon, Dec 09, 2002 at 05:48:45PM +0000, Linus Torvalds wrote:
    > >
    > > > 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.
    > >
    > > Time to look into an alternative like SYSCALL perhaps ?
    > >
    > SYSCALL is AMD. SYSENTER is Intel, and is likely to be significantly
    > faster. Unfortunately SYSENTER is also extremely braindamaged, in
    > that it destroys *both* the EIP and the ESP beyond recovery, and
    > because it's allowed in V86 and 16-bit modes (where it will cause
    > permanent data loss) which means that it needs to be able to be turned
    > off for things like DOSEMU and WINE to work correctly.
    > -hpa


    Terje Eggestad
    Scali Scalable Linux Systems

    Olaf Helsets Vei 6 tel: +47 22 62 89 61 (OFFICE)
    P.O.Box 150, Oppsal +47 975 31 574 (MOBILE)
    N-0619 Oslo fax: +47 22 62 89 51

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