Message-ID: <4567B0CC.4030802@saville.com>
Date: Fri, 24 Nov 2006 18:56:12 -0800
From: Wink Saville <wink@saville.com>
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To: Ingo Molnar <mingo@elte.hu>
CC: Andi Kleen <ak@suse.de>, linux-kernel@vger.kernel.org,
       Andrew Morton <akpm@osdl.org>, Arjan van de Ven <arjan@infradead.org>,
       Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [patch] x86: unify/rewrite SMP TSC sync code
References: <20061124170246.GA9956@elte.hu> <200611241813.13205.ak@suse.de> <20061124202514.GA7608@elte.hu>
In-Reply-To: <20061124202514.GA7608@elte.hu>
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Ingo Molnar wrote:
> * Andi Kleen <ak@suse.de> wrote:
> 
> a new CPU is added. If the TSC isnt sync on SMP then it quickly gets 
> pretty messy, and we should rather take a look at /why/ these apps are 
> using RDTSC.
> 
> 	Ingo
> -

I use RDTSC in get a cheap method of measuring time. What other choices are
there for a low overhead high frequency time source?

By low overhead a kernel call is way to expensive, I want to minimally impact
the code and have many of these calls through out the code. One of the
ways I use it is to instrument multi-threaded applications and then use
the TSC to compare when actions occur between threads. i.e. I use it as a
time stamp counter and neither precision or accuracy is too important.
On the other hand the more precise and accurate the better:)

Cheers,

Wink Saville


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