linux-kernel - Re: [PATCH 0/2] Make the TSC safe to be used by gettimeofday().

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Message-Id: <200611140250.57160.ak@suse.de>
Date:	Tue, 14 Nov 2006 02:50:57 +0100
From:	Andi Kleen <ak@...e.de>
To:	Suleiman Souhlal <ssouhlal@...ebsd.org>
Cc:	Linux Kernel ML <linux-kernel@...r.kernel.org>, vojtech@...e.cz,
	Jiri Bohac <jbohac@...e.cz>
Subject: Re: [PATCH 0/2] Make the TSC safe to be used by gettimeofday().

On Tuesday 14 November 2006 02:06, Suleiman Souhlal wrote:
> I've had a proof-of-concept for this since August, and finally got around to
> somewhat cleaning it up.

Thanks. 

I got a competing implementation for this unfortunately now from Vojtech & Jiri

Yours is simpler, but I'm not sure as complete. What are your assurances
against non monoticity for example?

> 
> It can certainly still be improved, namely by using vgetcpu() instead of CPUID
> to find the cpu number (but I couldn't get it to work, when I tried).

What did not work?

> Another possible improvement would be to use RDTSCP when available.
> There's also a small race in do_gettimeofday(), vgettimeofday() and
> vmonotonic_clock() but I've never seen it happen.

I did a vposix_getclock with monotonic clock support on my own already, was about to 
be merged with the vDSO. It still used global synchronized TSC though.

-Andi 
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