high system load when using i915kms

[Max Brazhnikov]

On Fri, 08 Mar 2013 11:38:13 -0800 Kevin Oberman wrote:
> On Fri, Mar 8, 2013 at 10:03 AM, Max Brazhnikov <makc at freebsd.org> wrote:
> >   PID USERNAME     THR PRI NICE   SIZE    RES STATE   C   TIME   WCPU
> > COMMAND
> >    11 root           2 155 ki31     0K    32K RUN     1   4:16 120.35% 
idle
> >    12 root          18 -84    -     0K   288K WAIT    0   0:57 76.34% intr
> >
> > I've got this after second boot today, although I couldn't reproduce it
> > yesterday even after ten attempts. But sometimes it's quite nasty and I
> > have
> > to reboot the system several times to get rid of it.
> >
> > Max
> >
> 
> So the issue is that that the interrupts from one or another of the USB
> devices has exploded from near zero to around 40K when the kernel module is
> loaded?

Exactly.

> A couple of possibly irrelevant questions. Do you normally manually load
> the module? I did not research the issue, but when I manually load the
> module I was seeing things just grind to a halt. If I started Gnome, the
> module was loaded automatically by X, and things worked.

No I don't usually load it manually, I was just wondering what causes the 
interrupt storm.

> Why loading the Intel KMS module would cause a massive increase in
> interrupts on a USB interface completely baffles me, but I suspect some
> sort of race is going on when the module is pre-loaded.

It happens if I allow X to load the module also, the problem is not due to 
pre-loading.

Max