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Date: Tue, 17 Dec 2002 11:12:46 -0800
From: "H. Peter Anvin" <hpa@transmeta.com>
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To: Linus Torvalds <torvalds@transmeta.com>
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Subject: Re: Intel P6 vs P7 system call performance
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Linus Torvalds wrote:
> 
> It's not as good as a pure user-mode solution using tsc could be, but
> we've seen the kinds of complexities that has with multi-CPU systems, and
> they are so painful that I suspect the sysenter approach is a lot more
> palatable even if it doesn't allow for the absolute best theoretical
> numbers.
> 

The complexity only applies to nonsynchronized TSCs though, I would
assume.  I believe x86-64 uses a vsyscall using the TSC when it can
provide synchronized TSCs, and if it can't it puts a normal system call
inside the vsyscall in question.

	-hpa


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