[linux-audio-user] IRQ settings and low latency

[Clemens Ladisch]

Mark Knecht wrote:
> The priority, as I understand it, is driven by the highest vector
> number.

Actually, lower vector numbers have higher priorities.  The priority
level is determined by the upper four bits of the vector number.

> *APPARENTLY* interrupts with no vector (like the system timer)

The system timer is redirected to interrupt 2.  Don't ask why.

> are either not handled by the APIC system, or are just higher
> priority than those with vectors.

Vector number 00 is reserved, so these entries are unused.

> Unfortunately I know of no method to tune the system interrupt
> priorities other than move cards ...

The kernel must be configured to assign different vector numbers to
specific interrupts.  The standard kernel cannot do this, but, as it
happens, I've just written a patch which adds this capability.  See
<http://www.informatik.uni-halle.de/~ladischc/linux_interrupt_priorities.html>.


HTH
Clemens