[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20160414002503.GQ2906@worktop>
Date: Thu, 14 Apr 2016 02:25:03 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Waiman Long <waiman.long@....com>
Cc: Ingo Molnar <mingo@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
x86@...nel.org, Jiang Liu <jiang.liu@...ux.intel.com>,
Borislav Petkov <bp@...e.de>,
Andy Lutomirski <luto@...nel.org>,
Scott J Norton <scott.norton@....com>,
Douglas Hatch <doug.hatch@....com>,
Randy Wright <rwright@....com>
Subject: Re: [PATCH v4] x86/hpet: Reduce HPET counter read contention
On Wed, Apr 13, 2016 at 11:37:21AM -0400, Waiman Long wrote:
> The TSC clocksource, on the other hand, is per cpu. So there won't be much
> contention in accessing it. Normally TSC will be used the default clock
> source. However, if there is too much variation in the actual clock speeds
> of the individual CPUs,
Does the system actually have a clock rate skew? Not an offset?
> it will cause the TSC calibration to fail and revert
> to use hpet as the clock source. During bootup, hpet will usually be
> selected as the default clock source first. After a short time, the TSC will
> take over as the default clock source. Problem can happen during that short
> period of transition time too. In fact, we have 16-socket Broadwell-EX
> systems that has this soft lockup problem once in a few reboot cycles which
> prompted me to find a solution to fix it.
This 16 socket system is a completely broken trainwreck. Trying to use
HPET with _that_ many CPUs is absolutely insane.
Please tell your hardware engineers to fix the TSC clock domain.
Powered by blists - more mailing lists