Date: Fri, 13 Jan 2006 10:16:31 -0800
From: thockin@hockin.org
To: Lee Revell <rlrevell@joe-job.com>
Cc: linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: Dual core Athlons and unsynced TSCs
Message-ID: <20060113181631.GA15366@hockin.org>
References: <1137104260.2370.85.camel@mindpipe> <20060113180620.GA14382@hockin.org> <1137175117.15108.18.camel@mindpipe>
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On Fri, Jan 13, 2006 at 12:58:36PM -0500, Lee Revell wrote:
> > If your BIOS has an ACPI "HPET" table, then the kernel can use the HPET
> > timer instead.  It doesn't solve the problem for apps or other kernel bits
> > that use rdtsc directly, but there are other fixes for that floating
> > around which will hopefully get consideration when they're mature.
> 
> The apps can be converted to use clock_gettime(), but that does not help
> if the kernel can't keep reasonable time on these machines. 

Some apps/users need higher resolution and lower overhead that only rdtsc
can offer currently.

> But if we just use "clock=pmtmr" by default on these machines the TSC is
> not a problem right?

I never tried it with pmtimer, we had HPET available.  Empirically TSC did
not work (and we had a simple test case to show how bad it could get).
HPET made that go away for users of gettimeofday().

We're exploring rdtsc-compatible solutions.
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