Re: SMP and CPU1 not showing interrupts in /proc/interrupts

From: dada1 (dada1@cosmosbay.com)
Date: Sun Feb 23 2003 - 05:52:01 EST


I too had such interrupt distribution...

In my case, absolutely no interrupts was taken by CPU1, even the timer...
and I recall that timer interrupts should hit all the CPUS or strange things
can appear.

But, curiously, a

echo 3 >/proc/irq/0/smp_affinity

solved the problem for me (for IRQ 0 only of course)

I say curiously because the old smp_affinity value was 0xffffffff, so
masking the unused bits should have no effect.

Eric

> somewhere between about 2.5.53 and 2.5.62 my /proc/interrupts has gone
> from an approximately even distribution of interrupts between CPU0 and
> CPU1 to grossly uneven:
>
> CPU0 CPU1
> 0: 13223321 2233217 IO-APIC-edge timer
> 1: 13442 0 IO-APIC-edge i8042
> 2: 0 0 XT-PIC cascade
> 3: 291874 0 IO-APIC-edge serial
> 8: 3 0 IO-APIC-edge rtc
> 9: 0 0 IO-APIC-edge acpi
> 14: 18932 0 IO-APIC-edge ide0
> 15: 14 0 IO-APIC-edge ide1
> 16: 190607 1 IO-APIC-level eth0, nvidia
> 17: 3214 0 IO-APIC-level bttv0
> 18: 14249 1 IO-APIC-level ide2
> 19: 121942 0 IO-APIC-level uhci-hcd, wlan0
> NMI: 0 0
> LOC: 15458218 15458423
> ERR: 0
> MIS: 0
>
> if i really hit the system hard then CPU1 will start accruing interrupts
> but in a mostly idle state CPU1 just sits on its bum and lets CPU0
> handle them all, with the exception of irq #0, for some reason.
>
> any ideas?
>
> thanks
>
> James
>

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