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?
Regards.
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