x86: finding interrupts that aren't being accounted for?

[Adrian Chadd]

On 6 April 2015 at 14:15, Rui Paulo <rpaulo at me.com> wrote:
>
>> On Apr 6, 2015, at 13:38, Adrian Chadd <adrian at FreeBSD.org> wrote:
>>
>> On 6 April 2015 at 12:18, John Baldwin <jhb at freebsd.org> wrote:
>>> On Monday, April 06, 2015 12:21:29 AM Adrian Chadd wrote:
>>>> Hi,
>>>>
>>>> I have an .. odd problem on a Lenovo X230.
>>>>
>>>> I just threw in a very old wifi card (Intel 3945) into the expresscard
>>>> (pcie) slot. Now, we don't have any pcie-hp support in -HEAD just yet,
>>>> but i wasn't expecting the system to crawl to a halt.
>>>>
>>>> When I unplug it, everything returns to normal.
>>>>
>>>> Other cards don't do this.
>>>>
>>>> So, I figured it may be interrupt spam - but vmstat -ia shows no
>>>> interrupts going crazy.
>>>>
>>>> pmcstat -S CPU_CLK_UNHALTED_CORE -T -w 5 doesn't register anything
>>>> either - only a handful of background samples.
>>>>
>>>> However, /counter/ mode pmc tells a different story - pmcstat -s
>>>> CPU_CLK_UNHALTED_CORE -w 1 shows all four cores going at 110% when the
>>>> card is inserted, with brief periods of idle. Once I remove the card,
>>>> the counters go back down to zero.
>>>>
>>>> My working theory is: something is chewing CPU and it's likely
>>>> interrupts, but if it is, it's something far, far earlier than the x86
>>>> interrupt C code, which counts interrupts and spurious events.
>>>>
>>>> So - has anyone diagnosed this stuff on FreeBSD/x86 before? I was kind
>>>> of hoping we'd at least get accurate statistics about spurious
>>>> interrupts, and if we don't, I'd like to understand why.
>>>>
>>>> Thanks!
>>>
>>> SMM?  Perhaps SMM doesn't hide itself from PMC counters (but it can hide itself
>>> from samples).
>>>
>>> If it is SMM there's not really anything you can do about it.  Try getting a
>>> KTR_SCHED trace and looking at it in schedgraph.  When I've seen SMM isuses in
>>> the past it shows up as hole in the graph where nothing happens in the system.
>>>
>>> In your case you could perhaps be getting PCI errors that are triggering the
>>> SMM handler.  Perhaps compare pciconf -le before and after to see if there are
>>> any changes.
>>
>> Hm, ok. Can we extract PCIe errors yet?
>
> Yes, check pciconf.

I'll try, but the system is pretty unusable whilst the card is plugged in...

Thanks!



-a