Hello, I am measuring system latency using latencytop. I am using kernel version 3.0 with some minor changes. The latencytop output for the process doing the IO (qemu) is below: Process qemu-system-x86 (6239) Total: 31363.7 msec [sleep_on_page] 1966.5 msec 81.4 % Waiting for event (select) 5.0 msec 7.8 % [kvm_vcpu_block] 5.0 msec 8.5 % synchronous write 1.7 msec 0.0 % Userspace lock contention 1.5 msec 2.3 % Is the 2000 msec sleep_on_page delays normal ? I would also like to know what sleep_on_page exactly corresponds to. My understanding is that it is the time spent waiting for grabbing a lock on a page. Is this correct ? Thanks.