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Subject: Re: gettimeofday() system call timing curiosity
To: root@chaos.analogic.com
Date: Fri, 8 Mar 2002 19:19:55 +0000 (GMT)
Cc: lk@tantalophile.demon.co.uk (Jamie Lokier), hpa@zytor.com (H. Peter Anvin),
        linux-kernel@vger.kernel.org, alan@lxorguk.ukuu.org.uk (Alan Cox),
        terje.eggestad@scali.com (Terje Eggestad),
        greearb@candelatech.com (Ben Greear),
        davidel@xmailserver.org (Davide Libenzi),
        george@mvista.com (george anzinger)
In-Reply-To: <Pine.LNX.3.95.1020308134552.6627A-100000@chaos.analogic.com> from "Richard B. Johnson" at Mar 08, 2002 01:54:16 PM
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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
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> The following program clearly shows that Linux will not return the
> same gettimeofday values twice in succession. Since it provably takes
> less than 1 microsecond to make a system call on a modern machine,

We don't wait. Your computer just sucks 8)

More seriously even on a processor with a TSC we have to take a lock and
do several computations.

Alan
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