From: Andrea Arcangeli <andrea@suse.de>
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
Date: Fri, 17 Nov 2000 16:18:33 +0100 [thread overview]
Message-ID: <20001117161833.A27098@athlon.random> (raw)
In-Reply-To: <E13wkLK-0000bP-00@the-village.bc.nu> <qwwpujuvk1s.fsf@sap.com>
In-Reply-To: <qwwpujuvk1s.fsf@sap.com>; from cr@sap.com on Fri, Nov 17, 2000 at 01:51:11PM +0100
On Fri, Nov 17, 2000 at 01:51:11PM +0100, Christoph Rohland wrote:
> 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.
During the x86-64 design I made sure that in x86-64 glibc will only know about
vgettimeofday (vsyscall).
If the machine is Asymetric MP with CPU running at different frequency (so that
you need to know on which CPU you're running on to use rdtsc) the kernel will
setup the vsyscall trampoline to fallback in the real slow syscall (but all SMP
and UP machines will not need to enter/exit kernel this way and the vsyscall
will be completly lock less... for obvious reasons :).
So as worse you'll have to wait x86-64 to get that lightweight vgettimeofday.
Andrea
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next prev parent reply other threads:[~2000-11-17 15:50 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2000-11-17 9:50 Error in x86 CPU capabilities starting with test5/6 Jordan
2000-11-17 11:39 ` Mikael Pettersson
2000-11-17 11:58 ` Tigran Aivazian
2000-11-17 12:10 ` Alan Cox
2000-11-17 12:51 ` Christoph Rohland
2000-11-17 13:08 ` Jeff Garzik
2000-11-17 13:21 ` Christoph Rohland
2000-11-17 13:31 ` Andi Kleen
2000-11-17 13:40 ` Jeff Garzik
2000-11-17 13:54 ` Andi Kleen
2000-11-17 14:02 ` Tigran Aivazian
2000-11-17 14:30 ` Christoph Rohland
2000-11-17 14:50 ` Alan Cox
2000-11-17 14:00 ` Arjan van de Ven
2000-11-17 15:18 ` Andrea Arcangeli [this message]
2000-11-17 16:06 ` Christoph Rohland
2000-11-17 18:28 ` Andrea Arcangeli
2000-11-18 9:57 ` Christoph Rohland
2000-11-19 10:31 ` Albert D. Cahalan
2000-11-17 13:38 ` Mikael Pettersson
2000-11-17 12:04 ` Andi Kleen
2000-11-17 12:14 ` Jan Niehusmann
2000-11-17 12:22 ` Andi Kleen
2000-11-17 13:26 ` Mohammad A. Haque
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