Re: why no IO-APIC?

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Re: why no IO-APIC?



Florin Andrei wrote:
What is the reason why IO-APIC is disabled in the RH kernels?

I have a desktop system, optimized for heavy multimedia work, which has
quite a few PCI controllers in it (IEEE1394, analog video capture, etc.)
besides the usual stuff (network, video). The normal IRQ space is quite
tight. Here's a sample of /proc/interrupts:

Due to IRQ overlaps, the performance of the system is quite suboptimal,
especially when devices using the same IRQ are working at the same time.

Enabling IO-APIC makes room above IRQ 15, potentially eliminating those
nasty interrupt overlaps. I've noticed that when using a vanilla 2.4.20
kernel with IO-APIC enabled.

The system has an AthlonXP proc, and an nForce1 motherboard.

https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=62295

I'm not sure if this is related, but "local apic" seems to cause problems for just about every mobile Athlon as well as several other Athlon machines.

When I enable APIC on 2.4.x and 2.5.x kernels on these machines it causes this kind of behavior, or sometimes worse (kernel panics).

Warren Togami
warren@togaim.com



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