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From: Thomas Gleixner <tglx@linutronix.de>
To: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, Don Zickus <dzickus@redhat.com>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	Andi Kleen <ak@linux.intel.com>,
	Adrian Hunter <adrian.hunter@intel.com>,
	Anton Blanchard <anton@samba.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH v1] watchdog: Use a reference cycle counter to avoid scaling issues
Date: Thu, 23 Apr 2015 22:01:04 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.11.1504232153080.13914@nanos> (raw)
In-Reply-To: <1429801408-11309-1-git-send-email-alexander.shishkin@linux.intel.com>

On Thu, 23 Apr 2015, Alexander Shishkin wrote:

> The problem with using cycle counter for NMI watchdog is that its
> frequency changes with the corresponding core's frequency. This means
> that, in particular, if the core frequency scales up, watchdog NMI will
> arrive more frequently than what user requested through watchdog_thresh
> and also increasing the probability of setting off the hardlockup detector,
> because the corresponding hrtimer will keep firing at the same intervals
> regardless of the core frequency. And, if the core can turbo to up to 2.5x
> its base frequency (and therefore TSC) [1], we'll have the hrtimer and NMI

So you are saying that this M-5Y10 has a non-constant TSC again? You
really can't be serious about that.

Please provide the output of /proc/cpuinfo

Thanks,

	tglx

  reply	other threads:[~2015-04-23 20:01 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-23 15:03 Alexander Shishkin
2015-04-23 20:01 ` Thomas Gleixner [this message]
2015-04-23 20:32   ` Andi Kleen
2015-04-23 21:37     ` Thomas Gleixner
2015-04-24  0:51       ` Andi Kleen
2015-04-24  8:44         ` Thomas Gleixner
2015-04-24  9:35           ` Thomas Gleixner
2015-04-24  9:46             ` Alexander Shishkin
2015-04-24  9:48               ` Thomas Gleixner
2015-04-24  9:59           ` Andi Kleen
2015-04-24 11:50             ` Thomas Gleixner
2015-04-24  9:01         ` Borislav Petkov

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