linux-kernel - Re: PROBLEM: no cpu MHz in /proc/cpuinfo on 2.6.25.4-rt6

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Message-ID: <20080611135532.651fb5ae@infradead.org>
Date:	Wed, 11 Jun 2008 13:55:32 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	markh@...pro.net
Cc:	"linux-os (Dick Johnson)" <linux-os@...logic.com>,
	Jan Engelhardt <jengelh@...ozas.de>,
	"Kok, Auke" <auke-jan.h.kok@...el.com>,
	solsTiCe d'Hiver <solstice.dhiver@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: PROBLEM: no cpu MHz in /proc/cpuinfo on 2.6.25.4-rt6

On Wed, 11 Jun 2008 16:37:38 -0400
> > Mark 
> > 
> 
> Ok, what would one use besides the tsc to take a fast high-res time
> stamp in a kernel module that could also be used in user land (same
> time source) to for instance calculate  the the time between an event
> in the kernel to an event in user land?
> 
> do_gettimeofday / gettimeofday are not really acceptable.


why not? both of these (they're teh same) are the best the kernel can
do. If there was a better way to do it, gettimeofday() would use it.
It's not even a system call if we can get away with it
(although system calls are pretty cheap)

really, think about it. if there was a better way, gettimeofday() would
use it.


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