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Date: Mon, 16 Dec 2002 22:18:27 -0800 (PST)
From: Linus Torvalds <torvalds@transmeta.com>
To: Dave Jones <davej@codemonkey.org.uk>
cc: Ingo Molnar <mingo@elte.hu>, <linux-kernel@vger.kernel.org>,
       <hpa@transmeta.com>
Subject: Re: Intel P6 vs P7 system call performance
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On Mon, 16 Dec 2002, Linus Torvalds wrote:
>
> 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.

Final comparison for the evening: a PIII looks very different, since the
system call overhead is much smaller to begin with. On a PIII, the above
ends up looking like

   gettimeofday() testing:
	sysenter:	561.697236 cycles
	int/iret:	686.170463 cycles
			124.473227 cycles diff
	factor 1.221602

ie the speedup is much less because the original int/iret numbers aren't
nearly as embarrassing as the P4 ones. It's still a win, though.

		Linus

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