Messages in this thread | | | Subject | Re: [RFC PATCH 1/1] smi_detector: A System Management Interrupt detector | From | Jon Masters <> | Date | Tue, 02 Jun 2009 16:32:31 -0400 |
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On Tue, 2009-06-02 at 11:32 -0700, Paul E. McKenney wrote: > On Sun, May 31, 2009 at 12:31:18PM -0400, Jon Masters wrote: > > This patch introduces a new SMI (System Management Interrupt) detector module > > that can be used to detect high latencies within the system. It was originally > > written for use in the RT kernel, but has wider applications. > > This would have been extremely handy a few years back when we were > chasing some latency issues!!! ;-)
Thanks. One guy on IRC already asked why it didn't find all his SMIs. I'll add to the docs that this can obviously only detect when it's sampling - since we can't constantly sample without "locking up" the machine, it's a tradeoff. The defaults are intended so you could put them on a laptop and not notice - in practice, I've been running with 1 second window size and .5 second sample width - i.e. very meaty and highly disruptive, but great at catching the little so and sos :)
> I don't see how this handles CPU hotplug operations (see interspersed), > but I am OK with "don't do CPU-hotplug operations while running this > test."
It doesn't, good catch. Though in fairness, I don't think that's big issue - but having said that, the ring_buffer handles cpu hotplug nicely and I just need to think a bit harder, so I'll possibly do that in my next v3 posting...gonna go get that one ready now.
Thanks guys,
Jon.
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