linux-kernel - Re: AMD X2 unsynced TSC fix?

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Message-ID: <20061027201820.GA8394@dreamland.darkstar.lan>
Date:	Fri, 27 Oct 2006 22:18:20 +0200
From:	Luca Tettamanti <kronos.it@...il.com>
To:	Lee Revell <rlrevell@...-job.com>
Cc:	linux-kernel@...r.kernel.org, Andi Kleen <ak@...e.de>,
	john stultz <johnstul@...ibm.com>
Subject: Re: AMD X2 unsynced TSC fix?

Lee Revell <rlrevell@...-job.com> ha scritto:
> Someone recently pointed out to me that a Windows "CPU driver update"
> supplied by AMD fixes the unsynced TSC problem on dual core AMD64
> systems.
[...]
> other incorrect timing effects that these applications may experience on
> dual-core processor systems, by periodically adjusting the core
> time-stamp-counters, so that they are synchronized."
> 
> What are the chances of Linux getting a similar fix?

Zero? ;)
There's always a window where the TSCs are not in sync (and userspace may
see a non-monotonic counter); furthermore when C'n'Q is active TSCs
aren't updated at a fixed frequency, userspace cannot use TSC for timing
anyway.


Luca
-- 
> While we're on all of this, are we going to change "tained" to some
> other less alarmist word?
"screwed" -- Alexander Viro
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