Philippe Gerum wrote:
> > I rather think, also when looking at Julien's second trace, that we have
> > some issue with X in user-space here, probably in combination with weird
> > VIA hardware stalling IRQ delivery for a "few" microseconds. Let's see
> > if the irqbench gives similar results.
> >
>
> The problem is that I can reproduce X-related jittery (> 2 ms in a row)
> on one of my test boxen when dragging windows over the screen, without
> triggering the NMI watchdog set to 100 us (and guess what, the chipset
> in question is from VIA).
IMHO there are two reasons why the NMI watchdog may not trig:
- its code is broken (we already have an unsolved bug that shows us that
maybe it does not work as we believe)
- the NMI watchdog only counts busy cycles, so maybe the CPU is not busy
during these 2 ms, it is spinning, waiting for the GPU to finish the
work using the rep; nop instruction in order to allow power
saving. But with interrupts off.
Maybe disabling hardware acceleration in your X server configuration
would help ?
--
Gilles Chanteperdrix.
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