Here's another version, fleshed out a little more from Nathan's comments. Test Case 1: What happens to disk controller interrupts when you offline a CPU on a multiprossor system? 1. Note the current smp_affinity mask for the disk controller to stress. Set the IRQ smp_affinity mask for the disk controller to all CPU's. Echo the appropriate hex mask into /proc/irq/IRQ#/smp_affinity Verify the smp_affinity mask. 2. Start watching the interrupt counts in /proc/interrupts. Is it worth verifying tools such as sar at the same time? 3. Start writing to a disk. while true; do echo 1 > dud; sleep 1; done Suggestions for what to do in order to be able to verify all writes are completed and correct? 4. Offline a CPU, pick on cpu1. echo 0 > /sys/devices/system/cpu/cpu1/online cpu0 is not hotswappable on some architectures and will not have an online attribute. Can we pinpoint when a CPU goes offline? It's my understanding that timeslice overrun prevents 'time echo 0 > /sys/devices/system/cpu/cpu1/online' from being an accurate measure of how long it takes to offline a CPU. A turn of 0 (zero) signified the successful complettion of offlining the CPU from the kernel's point of view. Verify the smp_affinity mask of the affected disk controller. 5. Analyze data collected from /proc/interrupts? Relevent messages in /var/log/messages regarding the procedure will occur depending on the architecture tested on.
