Messages in this thread | | | Date | Fri, 12 Oct 2007 12:58:09 +0200 | From | John Sigler <> | Subject | Re: NMI watchdog |
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Björn Steinbrink wrote:
> John Sigler wrote: > >> I'm experiencing a full system lockup. I'm using an out-of-tree driver >> which I suspect is responsible. I'm trying to enable the NMI watchdog. >> >> # cat /proc/version >> Linux version 2.6.22.1-rt9 (gcc version 3.4.6) #1 PREEMPT RT Tue Oct 9 >> 12:25:47 CEST 2007 >> >> # cat /proc/cmdline >> ro root=/dev/hdc1 console=ttyS0,57600n8 console=tty0 panic=3 apic=debug >> nmi_watchdog=2 >> >> However, after boot, the NMI count does not change. >> >> # cat /proc/interrupts ; sleep 10 ; cat /proc/interrupts > > Try running some cpu hog in the background. The performance counters get > increased only when the CPU is actually doing something. On a mostly > idle system, it can take quite a while for the next NMI to show up.
You are right. In another shell, I ran while true; do : ; done
# cat /proc/interrupts ; sleep 10 ; cat /proc/interrupts CPU0 0: 100 IO-APIC-edge timer 4: 82 IO-APIC-edge serial 8: 1 IO-APIC-edge rtc 9: 0 IO-APIC-fasteoi acpi 15: 13648 IO-APIC-edge ide1 16: 1303 IO-APIC-fasteoi eth0 17: 575 IO-APIC-fasteoi eth1 18: 575 IO-APIC-fasteoi eth2 19: 575 IO-APIC-fasteoi eth3 NMI: 2889 LOC: 115768 ERR: 0 MIS: 0
CPU0 0: 100 IO-APIC-edge timer 4: 82 IO-APIC-edge serial 8: 1 IO-APIC-edge rtc 9: 0 IO-APIC-fasteoi acpi 15: 13672 IO-APIC-edge ide1 16: 1310 IO-APIC-fasteoi eth0 17: 580 IO-APIC-fasteoi eth1 18: 580 IO-APIC-fasteoi eth2 19: 580 IO-APIC-fasteoi eth3 NMI: 2899 LOC: 116770 ERR: 0 MIS: 0
The performance counter appears to be configured to fire when the event count for CPU_CLK_UNHALTED reaches 2,400,000,000 (I have a 2.4 GHz CPU) i.e. one NMI per second when the CPU is 100% busy. Is that correct?
On a related note, I have a Pentium 3 which counts CPU_CLK_UNHALTED cycles even when the CPU is halted. I was told this is a bug, but it actually sounds like a a nice feature!
Is there really no way to have the event counter increment with every tick (even when the CPU is halted) on a P4?
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