From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <waiman.long@hpe.com>
Cc: Ingo Molnar <mingo@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
linux-kernel@vger.kernel.org, x86@kernel.org,
Jiang Liu <jiang.liu@linux.intel.com>,
Borislav Petkov <bp@suse.de>, Andy Lutomirski <luto@kernel.org>,
Scott J Norton <scott.norton@hpe.com>,
Douglas Hatch <doug.hatch@hpe.com>,
Randy Wright <rwright@hpe.com>
Subject: Re: [PATCH v4] x86/hpet: Reduce HPET counter read contention
Date: Thu, 14 Apr 2016 02:25:03 +0200 [thread overview]
Message-ID: <20160414002503.GQ2906@worktop> (raw)
In-Reply-To: <570E67B1.3000708@hpe.com>
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.
next prev parent reply other threads:[~2016-04-14 0:25 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-12 18:46 [PATCH v4] x86/hpet: Reduce HPET counter read contention Waiman Long
2016-04-13 6:18 ` Ingo Molnar
2016-04-13 15:37 ` Waiman Long
2016-04-14 0:25 ` Peter Zijlstra [this message]
2016-04-14 2:10 ` Waiman Long
2016-05-12 23:20 ` Waiman Long
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20160414002503.GQ2906@worktop \
--to=peterz@infradead.org \
--cc=bp@suse.de \
--cc=doug.hatch@hpe.com \
--cc=hpa@zytor.com \
--cc=jiang.liu@linux.intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=mingo@kernel.org \
--cc=mingo@redhat.com \
--cc=rwright@hpe.com \
--cc=scott.norton@hpe.com \
--cc=tglx@linutronix.de \
--cc=waiman.long@hpe.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).