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Subject: Re: Intel P6 vs P7 system call performance
From: GrandMasterLee <masterlee@digitalroadkill.net>
To: Linus Torvalds <torvalds@transmeta.com>
Cc: Dave Jones <davej@codemonkey.org.uk>, Ingo Molnar <mingo@elte.hu>,
       linux-kernel@vger.kernel.org, hpa@transmeta.com
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Date: 17 Dec 2002 00:19:02 -0600
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On Tue, 2002-12-17 at 00:09, Linus Torvalds wrote:
> On Mon, 16 Dec 2002, Linus Torvalds wrote:
> >
> > On my P4 machine, a "getppid()" is 641 cycles with sysenter/sysexit, and
> > something like 1761 cycles with the old "int 0x80/iret" approach. That's a
> > noticeable improvement, but I have to say that I'm a bit disappointed in
> > the P4 still, it shouldn't be even that much.
> 
> On a slightly more real system call (gettimeofday - which actually matters
> in real life) the difference is still visible, but less so - because the
> system call itself takes more of the time, and the kernel entry overhead
> is thus not as clear.
> 
> For gettimeofday(), the results on my P4 are:
> 
> 	sysenter:	1280.425844 cycles
> 	int/iret:	2415.698224 cycles
> 			1135.272380 cycles diff
> 	factor 1.886637
> 
> ie sysenter makes that system call almost twice as fast.


I'm curious, if this is one of the Dual P4's non-Xeon(say, 2.4 Ghz+?) or
if this is one of the Xeons? There seems to be some perceived disparity
between which performs how. I think the biggest difference on the Xeon's
is the stepping and the cache,(pipeline too?), but not too much else.

[...]
> 			Linus
> 

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