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Date: Tue, 17 Dec 2002 11:37:04 -0800 (PST)
From: Linus Torvalds <torvalds@transmeta.com>
To: "H. Peter Anvin" <hpa@transmeta.com>
cc: Ulrich Drepper <drepper@redhat.com>, Alan Cox <alan@lxorguk.ukuu.org.uk>,
       Matti Aarnio <matti.aarnio@zmailer.org>,
       Hugh Dickins <hugh@veritas.com>, Dave Jones <davej@codemonkey.org.uk>,
       Ingo Molnar <mingo@elte.hu>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Intel P6 vs P7 system call performance
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On Tue, 17 Dec 2002, H. Peter Anvin wrote:
>
> Let's see... it works fine on UP and on *most* SMP, and on the ones
> where it doesn't work you just fill in a system call into the vsyscall
> slot.  It just means that gettimeofday() needs a different vsyscall slot.

The thing is, gettimeofday() isn't _that_ special. It's just not worth a
vsyscall of it's own, I feel. Where do you stop? Do we do getpid() too?
Just because we can?

This is especially true since the people who _really_ might care about
gettimeofday() are exactly the people who wouldn't be able to use the fast
user-space-only version.

How much do you think gettimeofday() really matters on a desktop? Sure, X
apps do gettimeofday() calls, but they do a whole lot more of _other_
calls, and gettimeofday() is really far far down in the noise for them.
The people who really call for gettimeofday() as a performance thing seem
to be database people who want it as a timestamp. But those are the same
people who also want NUMA machines which don't necessarily have
synchronized clocks.

		Linus

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