linux-kernel - Re: [patch 0/9] x86_64: reliable TSC-based gettimeofday

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Message-Id: <200702011302.41963.ak@suse.de>
Date:	Thu, 1 Feb 2007 13:02:41 +0100
From:	Andi Kleen <ak@...e.de>
To:	Andrea Arcangeli <andrea@...e.de>
Cc:	jbohac@...e.cz, linux-kernel@...r.kernel.org,
	Vojtech Pavlik <vojtech@...e.cz>, ssouhlal@...ebsd.org,
	arjan@...radead.org, tglx@...utronix.de, johnstul@...ibm.com,
	zippel@...ux-m68k.org
Subject: Re: [patch 0/9] x86_64: reliable TSC-based gettimeofday

On Thursday 01 February 2007 12:53, Andrea Arcangeli wrote:
> On Thu, Feb 01, 2007 at 12:20:59PM +0100, Andi Kleen wrote:
> > I think a better way to do this would be to define a new CLOCK_THREAD_MONOTONOUS
> > (or better name) timer for clock_gettime(). 
> > 
> > [and my currently stalled vdso patches that implement clock_gettime
> > as a vsyscall]
> > 
> > Then also an application could easily use it with LD_PRELOAD
> 
> I think a prctl to enable the non monothone mode is better than any
> LD_PRELOAD trick.

I don't think so because having per process state in a vsyscall
is quite costly. You would need to allocate at least one more
page to each process, which I think would be excessive.

-Andi
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