From: Andi Kleen <ak@suse.de>
To: Stephane Eranian <eranian@hpl.hp.com>
Cc: Andi Kleen <ak@suse.de>, Nicholas Miell <nmiell@comcast.net>,
Ray Bryant <raybry@mpdtxmail.amd.com>,
discuss@x86-64.org, linux-kernel@vger.kernel.org,
perfctr-devel@lists.sourceforge.net
Subject: Re: [discuss] Re: [Perfctr-devel] Re: Enabling RDPMC in user space by default
Date: Fri, 2 Dec 2005 01:07:37 +0100 [thread overview]
Message-ID: <20051202000737.GG997@wotan.suse.de> (raw)
In-Reply-To: <20051201234150.GE3291@frankl.hpl.hp.com>
On Thu, Dec 01, 2005 at 03:41:50PM -0800, Stephane Eranian wrote:
> On Wed, Nov 30, 2005 at 05:23:15PM +0100, Andi Kleen wrote:
> > > to count elapsed cycles while executing a ring 0 and ring 3. The watchdog
> > > works by polling on the counter and after a certain delta is reached it
> > > triggers an NMI interrupt which, in turn, causes a kernel crash and the
> > > (bug) report. Is that the correct behavior?
> >
> > The watchdog is driven by the performance counter (this means
> > it has varying frequency, but that's not a big issue for the watchdog)
> >
> > It underflows every second in the fastest case or very slowly
> > (if the machine is idle). Every time it underflows it checks if
> > the per CPU timer has been ticking, and if it hasn't for some time
> > it triggers an oops.
>
> How is the checking for underflows done? Polling?
There is a bit in the perfctr MSRs to cause an interrupt if it underflows.
That is programmed to be an NMI.
-Andi
next prev parent reply other threads:[~2005-12-02 0:07 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-11-29 15:15 Enabling RDPMC in user space by default Andi Kleen
2005-11-29 16:04 ` Mikael Pettersson
2005-11-29 16:17 ` Andi Kleen
2005-11-29 16:56 ` Ray Bryant
2005-11-29 16:15 ` Andi Kleen
2005-11-29 18:09 ` [Perfctr-devel] " Stephane Eranian
2005-11-29 18:13 ` Andi Kleen
2005-11-29 18:29 ` John Reiser
2005-11-29 18:38 ` Andi Kleen
2005-11-29 19:05 ` Lee Revell
2005-11-29 21:43 ` Nicholas Miell
2005-11-29 21:52 ` Andi Kleen
2005-11-29 22:19 ` Stephane Eranian
2005-11-29 22:51 ` [discuss] " Andi Kleen
2005-11-30 16:01 ` Stephane Eranian
2005-11-30 16:23 ` Andi Kleen
2005-12-01 23:41 ` Stephane Eranian
2005-12-02 0:07 ` Andi Kleen [this message]
2005-12-02 7:09 ` Stephane Eranian
2005-12-02 11:36 ` Andi Kleen
2005-11-29 22:33 ` Nicholas Miell
2005-11-29 22:43 ` Andi Kleen
2005-11-29 23:02 ` Nicholas Miell
2005-11-29 23:17 ` Andi Kleen
2005-11-29 23:29 ` Nicholas Miell
2005-11-29 23:39 ` Andi Kleen
2005-11-29 23:56 ` David Gibson
2005-11-30 0:34 ` Andi Kleen
2005-11-30 0:52 ` David Gibson
2005-11-30 1:04 ` [discuss] " Andi Kleen
2005-11-30 0:50 ` Ray Bryant
2005-11-30 0:38 ` Andi Kleen
2005-11-30 7:38 ` Stephane Eranian
2005-11-30 8:22 ` Nicholas Miell
2005-11-30 15:48 ` Stephane Eranian
2005-11-29 23:07 ` David Gibson
2005-11-29 23:18 ` [discuss] " Andi Kleen
2005-11-29 23:28 ` Bernd Schmidt
2005-11-29 23:46 ` [discuss] " Andi Kleen
2005-11-30 2:39 ` Zwane Mwaikambo
2005-11-30 3:38 ` Andi Kleen
2005-12-01 4:08 ` Zwane Mwaikambo
2005-12-01 13:05 ` Andi Kleen
2005-12-01 17:01 ` Zwane Mwaikambo
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