Messages in this thread | | | Date | Tue, 12 Jul 2022 09:25:32 -0700 | Subject | Re: [PATCH v4 4/4] pseries/mobility: set NMI watchdog factor during LPM | From | Randy Dunlap <> |
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Hi--
On 7/12/22 07:32, Laurent Dufour wrote: > During a LPM, while the memory transfer is in progress on the arrival side, > some latencies is generated when accessing not yet transferred pages on the
are
> arrival side. Thus, the NMI watchdog may be triggered too frequently, which > increases the risk to hit a NMI interrupt in a bad place in the kernel,
an NMI
> leading to a kernel panic. > > Disabling the Hard Lockup Watchdog until the memory transfer could be a too > strong work around, some users would want this timeout to be eventually > triggered if the system is hanging even during LPM. > > Introduce a new sysctl variable nmi_watchdog_factor. It allows to apply > a factor to the NMI watchdog timeout during a LPM. Just before the CPU are
an LPM. the CPU is
> stopped for the switchover sequence, the NMI watchdog timer is set to > watchdog_tresh + factor%
watchdog_thresh
> > A value of 0 has no effect. The default value is 200, meaning that the NMI > watchdog is set to 30s during LPM (based on a 10s watchdog_tresh value).
watchdog_thresh
> Once the memory transfer is achieved, the factor is reset to 0. > > Setting this value to a high number is like disabling the NMI watchdog > during a LPM.
an LPM.
> > Reviewed-by: Nicholas Piggin <npiggin@gmail.com> > Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com> > --- > Documentation/admin-guide/sysctl/kernel.rst | 12 ++++++ > arch/powerpc/platforms/pseries/mobility.c | 43 +++++++++++++++++++++ > 2 files changed, 55 insertions(+) > > diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst > index ddccd1077462..0bb0b7f27e96 100644 > --- a/Documentation/admin-guide/sysctl/kernel.rst > +++ b/Documentation/admin-guide/sysctl/kernel.rst > @@ -592,6 +592,18 @@ to the guest kernel command line (see > Documentation/admin-guide/kernel-parameters.rst). >
This entire block should be in kernel-parameters.txt, not .rst, and it should be formatted like everything else in the .txt file.
> > +nmi_watchdog_factor (PPC only) > +================================== > + > +Factor apply to to the NMI watchdog timeout (only when ``nmi_watchdog`` is
Factor to apply to the NMI
> +set to 1). This factor represents the percentage added to > +``watchdog_thresh`` when calculating the NMI watchdog timeout during a
during an
> +LPM. The soft lockup timeout is not impacted. > + > +A value of 0 means no change. The default value is 200 meaning the NMI > +watchdog is set to 30s (based on ``watchdog_thresh`` equal to 10). > + > + > numa_balancing > ============== >
-- ~Randy
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