Interrupt storm with MSI in combination with em1

[Daan Vreeken]

Hi Jack,

On Friday 06 May 2011 17:36:52 Jack Vogel wrote:
> On Fri, May 6, 2011 at 8:32 AM, Daan Vreeken <Daan at vehosting.nl> wrote:
> > Hi Steven,
> >
> > On Friday 06 May 2011 17:20:15 Steven Hartland wrote:
> > > From: "Daan Vreeken" <Daan at vehosting.nl>
> > >
> > > > # vmstat -i
> > > > interrupt                          total       rate
> > > > irq3: uart1                       917384         63
> > > > --> irq16: ehci0                   809547235      55608
> > >
> > > Have you tried removing USB from the kernel?
> > >
> > > USB seems to be a common course of this behaviour and here at least
> > > removing it from the kernel fixes in all cases assuming you don't
> > > need it for something?
> >
> > No, I haven't tried that yet. I could disable USB to run some tests, but
> > I'll
> > eventually need it enabled again.
> > I'll wait for a couple of hours to see if anyone can come up with a test
> > to run on the machine while the interrupt is still storming. After that
> > I'll reboot it with USB disabled.
>
> I don't see why you are blaming em, you can see its on MSIX vectors
> that are NOT storming, its something with USB as noted. Trying to
> disable em from using MSIX is in exactly the wrong direction IMHO.

I'm not blaming this on 'em' per se. The only thing I've noticed in the tests 
that I've done so far is that I haven't seen the storms with MSI/MSIX 
disabled. With respect to the devices on IRQ 16, disabling MSI/MSIX only 
seems to change the way interrupts are delivered to the em0/em1 cards.
(This is what made me suspect the 'em' driver.)

At this moment all devices on IRQ 16 (including the PCI bridge itself) could 
be the source of the problem. I'm just trying to find a way to isolate the 
problem, either by finding a way to proof it is NOT device X, or by finding a 
way to proof it IS device Y.

I'll reboot the machine in a couple of minutes with USB disabled.


Regards,
-- 
Daan Vreeken
VEHosting
http://VEHosting.nl
tel: +31-(0)40-7113050 / +31-(0)6-46210825
KvK nr: 17174380