Subject: Re: [RT] read_tsc: ACK! TSC went backward! Unsynced TSCs?
From: Lee Revell <rlrevell@joe-job.com>
To: thockin@hockin.org
Cc: Steven Rostedt <rostedt@goodmis.org>, Ingo Molnar <mingo@elte.hu>,
       john stultz <johnstul@us.ibm.com>, LKML <linux-kernel@vger.kernel.org>
In-Reply-To: <20051128173040.GA32547@hockin.org>
References: <1133179554.11491.3.camel@localhost.localdomain>
	 <20051128173040.GA32547@hockin.org>
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Date: Mon, 28 Nov 2005 12:39:28 -0500
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On Mon, 2005-11-28 at 09:30 -0800, thockin@hockin.org wrote:
> The kernel's use of TSC is wholly incorrect.  TSCs can ramp up and
> down and *do* vary between nodes as well as between cores within a
> node.  You really can not compare TSCs between cpu cores at all, as is
> (and the kernel assumes 1 global TSC in at least a few places). 

That's one way to look at it; another is that the AMD dual cores have a
broken TSC implementation.  The kernel's use of the TSC was never a
problem in the past...

Lee

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