[LAD] Kontakt Spikes

[Clemens Ladisch]

Michael Ost wrote:
> On 10/10/2011 03:04 PM, Clemens Ladisch wrote:
>> I guess I can rule out SMIs because those should happen even when there
>> is one thread per core.
>
> Are these "System Management Interrupts"?

Yes.

>> How big are the latencies you're seeing?  They are not from being
>> interrupted by another RR thread at the same priority (see "man
>> sched_rr_get_interval")?
>
> We are wiring up the ftrace system in the kernel and cyclictest to find
> out for certain. It's looking like it could be 10s of milliseconds, when
> there is only 2.9 msecs to process (44.1k/128 samples).

Tens of millisconds looks too long for a SMI.  Anyway, the fact that the
delays occur only when there is CPU contention points to the kernel
scheduler.

What is the time quantum that sched_rr_get_interval() returns for these
threads?


Regards,
Clemens