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Subject: Re: Intel P6 vs P7 system call performance
From: Terje Eggestad <terje.eggestad@scali.com>
To: Ville Herva <vherva@niksula.hut.fi>
Cc: "J.A. Magallon" <jamagallon@able.es>, Mark Mielke <mark@mark.mielke.cc>,
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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
culprit. 

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

TJ


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 --
    
v@iki.fi
-- 
_________________________________________________________________________

Terje Eggestad                  mailto:terje.eggestad@scali.no
Scali Scalable Linux Systems    http://www.scali.com

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
NORWAY            
_________________________________________________________________________

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