From: Andi Kleen <ak@suse.de>
To: thockin@hockin.org
Cc: Andi Kleen <ak@suse.de>, Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@elte.hu>, john stultz <johnstul@us.ibm.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RT] read_tsc: ACK! TSC went backward! Unsynced TSCs?
Date: Tue, 29 Nov 2005 17:48:58 +0100 [thread overview]
Message-ID: <20051129164858.GL19515@wotan.suse.de> (raw)
In-Reply-To: <20051129165219.GA12687@hockin.org>
On Tue, Nov 29, 2005 at 08:52:19AM -0800, thockin@hockin.org wrote:
> On Tue, Nov 29, 2005 at 07:06:24AM -0700, Andi Kleen wrote:
> > But I'm surprised you're saying 2.6.11 broke. At least 2.6.11 64bit should
> > have always used HPET in this case. I only broke it around 2.6.13
> > where I added an overeager optimization for single socket DC on my side based
> > on a misunderstanding. Earlier and later kernels should have been ok.
>
> we didn't have HPET enabled in BIOS until recently. Turning that on made
> all the TSC gettimeofday() crap disappear. Now to find and kill any
> straggling users of rdtsc
The newer kernels work around this too by using pmtimer when needed.
Of course it's slow.
Regarding straggling users of rdtsc - one way would be to optionally
trap them and log them in the kernel. That would work in ring 3 at least.
-Andi
prev parent reply other threads:[~2005-11-29 16:49 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-11-28 12:05 Steven Rostedt
2005-11-28 12:30 ` Jonas Oreland
2005-11-28 12:59 ` Steven Rostedt
2005-11-28 14:21 ` Ingo Molnar
2005-11-28 15:38 ` Lee Revell
2005-11-28 17:30 ` thockin
2005-11-28 17:39 ` Lee Revell
2005-11-28 18:30 ` Dave Jones
2005-11-28 18:35 ` thockin
2005-11-29 14:06 ` Andi Kleen
2005-11-29 16:52 ` thockin
2005-11-29 16:48 ` Andi Kleen [this message]
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