lkml.org 
[lkml]   [2010]   [Jan]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
Subjectintroduce NMI_AUTO as nmi_watchdog option
Hi Ingo,

To dig up an old thread last November:

======
* Aristeu Rozanski <aris@redhat.com> wrote:

> > > > > NMI_AUTO is a new nmi_watchdog option that makes LAPIC be tried
> > > > > first
> > > > > and if the CPU isn't supported, IOAPIC will be used. It's useful
> > > > > in
> > > > > cases where NMI watchdog is enabled by default in a kernel built
> > > > > for
> > > > > different machines. It can be configured by default or selected
> > > > > with
> > > > > nmi_watchdog=3 or nmi_watchdog=auto parameters.
> > > >
> > > > What i'd like to see for the NMI watchdog is much more ambitious
> > > > than
> > > > this: the use of perf events to run a periodic NMI callback.
> > > >
> > > > The NMI watchdog would cause the creation of a per-cpu perf_event
> > > > structure (in-kernel). All x86 CPUs that have perf event support
> > > > (the
> > > > majority of them) will thus be able to have an NMI
> > > > watchdog using a
> > > > nice, generic piece of code and we'd be able to phase out the
> > > > open-coded
> > > > NMI watchdog code.
> > > >
> > > > The user would not notice much from this: we'd still have the
> > > > /proc/sys/kernel/nmi_watchdog toggle to turn it on/off, and we'd
> > > > still
> > > > have the nmi_watchog= boot parameter as well. But the underlying
> > > > implementation would be far more generic and far more usable than
> > > > the
> > > > current code.
> > > >
> > > > Would you be interested in moving the NMI watchdog code in this
> > > > direction? Most of the perf events changes (callbacks, helpers for
> > > > in-kernel event allocations, etc.) are in latest
> > > > -tip already, so you
> > > > could use that as a base.
> > >
> > > but that would work only for LAPIC. You're suggesting killing IOAPIC
> > > mode too?
> >
> > Would it be a big loss, with all modern systems expected to have a
> > working lapic based NMI source? I wrote the IOAPIC mode originally but
> > i
> > dont feel too attached to it ;-)
>
> ok, fair enough. but since it'll be another implementation, do you
> mind applying the patches I submitted so they can be used until the
> new implementation is in place?

For that i need to see at least an RFC v1 version series of the new
implementation - otherwise we might end up sitting on this interim
version with no-one doing the better variant.

========

I was going to jump in and try to do this work. I wanted to make sure
what you were looking for here. When you say convert nmi watchdog to perf
events, I assume you mean merging over the bits of perfctr-watchdog.c to
perf_events.c, modify nmi.c to just register as a normal perf event and
probably cleanup the oprofile stuff to match, correct?

Cheers,
Don



\
 
 \ /
  Last update: 2010-01-11 20:19    [W:0.075 / U:3.872 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site