From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephane Eranian Date: Wed, 18 Dec 2002 01:01:36 +0000 Subject: Re: [Linux-ia64] Spurious PMU Interrupt Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org Ray, On Tue, Dec 17, 2002 at 06:53:31PM -0600, Ray Bryant wrote: > Stephane, > > I am getting one log message of the following type per CPU every time I > run a system-wide sampling session: > > kernel: perfmon: Spurious PMU overflow interrupt on CPUxx: pmc0=0x1 > owner00000000000000 > This happens on McKinley only, this is not an error and can be ignored. In fact in the latest version of the kernel (2.4.20), I removed the printk() to avoid confusion. This is due do an erratum in the McKinley PMU. The problem is in fact a desired feature which got cast as an error due to a bug in the Itanium PMU. Basically, if you set the freeze bit when it is not set you'll get a PMU interrupt. This is what happens at the end of a monitoring session in the current perfmon codebase for both 2.4 and 2.5. I think you can see how this "bug" is in fact a feature which could be use during the context switch, for instance. So you can ignore the problem. The new perfmon codebase that I am working on will never set the freeze bit explicitely anymore, so the "problem" will go away. -- -Stephane