* [Xenomai] perf nmi on x86
@ 2015-08-24 18:14 Gilles Chanteperdrix
2015-08-24 18:24 ` Jan Kiszka
0 siblings, 1 reply; 3+ messages in thread
From: Gilles Chanteperdrix @ 2015-08-24 18:14 UTC (permalink / raw)
To: Jan Kiszka, Xenomai
Hi Jan,
running Xenomai on an x86 machine, I noticed that the perf NMI was
ticking. It seems CONFIG_PERF can not be disabled in the kernel
configuration.
So, the first question is:
is there a way of disabling the NMI ?
second question is:
if not, what do we do about it?
I mean, on the one hand, disabling the NMI is probably mandatory on
a system where latency matters, but on the other hand, some users
may want it enabled and do not care for the additional latency.
Regards.
--
Gilles.
https://click-hack.org
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [Xenomai] perf nmi on x86
2015-08-24 18:14 [Xenomai] perf nmi on x86 Gilles Chanteperdrix
@ 2015-08-24 18:24 ` Jan Kiszka
2015-08-24 18:36 ` Gilles Chanteperdrix
0 siblings, 1 reply; 3+ messages in thread
From: Jan Kiszka @ 2015-08-24 18:24 UTC (permalink / raw)
To: Gilles Chanteperdrix, Xenomai
On 2015-08-24 20:14, Gilles Chanteperdrix wrote:
> Hi Jan,
>
> running Xenomai on an x86 machine, I noticed that the perf NMI was
> ticking. It seems CONFIG_PERF can not be disabled in the kernel
> configuration.
>
> So, the first question is:
> is there a way of disabling the NMI ?
> second question is:
> if not, what do we do about it?
>
> I mean, on the one hand, disabling the NMI is probably mandatory on
> a system where latency matters, but on the other hand, some users
> may want it enabled and do not care for the additional latency.
Does "echo 0 > /proc/sys/kernel/nmi_watchdog" change the picture? It did
so for me on a distro kernel, though re-enabling it again didn't make
the PMIs reappear.
Jan
--
Siemens AG, Corporate Technology, CT RTC ITP SES-DE
Corporate Competence Center Embedded Linux
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [Xenomai] perf nmi on x86
2015-08-24 18:24 ` Jan Kiszka
@ 2015-08-24 18:36 ` Gilles Chanteperdrix
0 siblings, 0 replies; 3+ messages in thread
From: Gilles Chanteperdrix @ 2015-08-24 18:36 UTC (permalink / raw)
To: Jan Kiszka; +Cc: Xenomai
On Mon, Aug 24, 2015 at 08:24:17PM +0200, Jan Kiszka wrote:
> On 2015-08-24 20:14, Gilles Chanteperdrix wrote:
> > Hi Jan,
> >
> > running Xenomai on an x86 machine, I noticed that the perf NMI was
> > ticking. It seems CONFIG_PERF can not be disabled in the kernel
> > configuration.
> >
> > So, the first question is:
> > is there a way of disabling the NMI ?
> > second question is:
> > if not, what do we do about it?
> >
> > I mean, on the one hand, disabling the NMI is probably mandatory on
> > a system where latency matters, but on the other hand, some users
> > may want it enabled and do not care for the additional latency.
>
> Does "echo 0 > /proc/sys/kernel/nmi_watchdog" change the picture? It did
> so for me on a distro kernel, though re-enabling it again didn't make
> the PMIs reappear.
Works for me, and writing 1 seems to re-enable it. Thanks. This
should really be documented somewhere, though.
--
Gilles.
https://click-hack.org
^ permalink raw reply [flat|nested] 3+ messages in thread
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2015-08-24 18:14 [Xenomai] perf nmi on x86 Gilles Chanteperdrix
2015-08-24 18:24 ` Jan Kiszka
2015-08-24 18:36 ` Gilles Chanteperdrix
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