User guide

D–Troubleshooting

Performance Issues

IB0054606-02 A D-11

This method is not the first choice because, on some systems, there may be two

rows of ib_qib output, and you will not know which one of the two numbers to

choose. However, if you cannot find $my_irq listed under /proc/irq

(Method 1), this type of system most likely has only one line for ib_qib listed in

/proc/interrupts, so you can use Method 2.

Here is an example:

# cat /sys/class/infiniband/ipath*/device/irq

# ls /proc/irq

0 10 11 13 15 233 4 50 7 8 90

1 106 12 14 2 3 5 58 66 74 9

(Note that you cannot find 98.)

# cat /proc/interrupts|grep ib_qib|awk \

’{print $1}’|sed -e ’s/://’

106

# echo 01 > /proc/irq/106/smp_affinity

Using the echo command immediately changes the processor affinity of an IRQ.

You can look at the stats in /proc/interrupts while the adapter is active to

observe which CPU is fielding ib_qib interrupts.

Immediately change the processor affinity of an IRQ

To immediately change the processor affinity of an IRQ, execute a command

similar to the following, as a root user:

echo 01 > /proc/irq/$my_irq/smp_affinity

The contents of the smp_affinity file may not reflect the expected values, even

though the affinity change has taken place. If the driver is reloaded, the affinity

assignment will revert to the default, so you will need to reset it to the desired

value. Look at the stats in /proc/interrupts while the adapter is active to see

which CPU is fielding ib_qib interrupts.

NOTE

 The contents of the smp_affinity file may not reflect the expected

values, even though the affinity change has taken place.

 If the driver is reloaded, the affinity assignment will revert to the default,

so you will need to reset it to the desired value.