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Message-ID: <3A152DC1.21B35324@mandrakesoft.com>
Date: Fri, 17 Nov 2000 08:08:17 -0500
From: Jeff Garzik <jgarzik@mandrakesoft.com>
Organization: MandrakeSoft
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To: Christoph Rohland <cr@sap.com>
CC: Alan Cox <alan@lxorguk.ukuu.org.uk>, Tigran Aivazian <tigran@veritas.com>,
        Mikael Pettersson <mikpe@csd.uu.se>, Jordan <ledzep37@home.com>,
        Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: Error in x86 CPU capabilities starting with test5/6
In-Reply-To: <E13wkLK-0000bP-00@the-village.bc.nu> <qwwpujuvk1s.fsf@sap.com>
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Christoph Rohland wrote:
> 
> Hi Alan,
> 
> On Fri, 17 Nov 2000, Alan Cox wrote:
> > Even checking the cpuinfo for the TSC should be done with care, and
> > its far far better to use gettimeofday unless doing very tiny
> > timings (eg for optimising code paths)
> 
> gettimeofday is _way_ to slow for a lot of every day uses. So
> applications will use rdtsc until we have some really fast
> (non-syscall) way to have high resolution time diffs.

IIRC, this came up a long time ago WRT Apache, which made a lot of
gettimeofday() calls.  Someone (Linus?) proposed the solution of a
'magic page' which holds information like gettimeofday() stuff, but
could be handled much more rapidly than a standard syscall.

-- 
Jeff Garzik             |
Building 1024           | The chief enemy of creativity is "good" sense
MandrakeSoft            |          -- Picasso
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