Hi Prateek... On Mon, Jan 16, 2012 at 11:48, Prateek Sharma <prateek3.14@xxxxxxxxx> wrote: > 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 % Which qemu version do you use now? AFAIK certain new qemu versions already uses iothreads by default. That should reduce I/O latency... AFAIK too iothreads is not enabled by default...but for qemu 1.0 above it's enabled by default. Are you compiling from source? Regarding the function sleep_on_page(). It's in turn io_schedule(). And here's the comment above the function declaration of io_schedule(): /* * This task is about to go to sleep on IO. Increment rq->nr_iowait so * that process accounting knows that this is a task in IO wait state. */ You can confirm it by yourself in: http://lxr.linux.no/#linux+v3.2.1/kernel/sched.c#L5872 Hope it helps.... -- regards, Mulyadi Santosa Freelance Linux trainer and consultant blog: the-hydra.blogspot.com training: mulyaditraining.blogspot.com _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
