Hi Prateek... On Mon, Jan 16, 2012 at 12:54, Prateek Sharma <prateek3.14@xxxxxxxxx> wrote: > I am using qemu-kvm 0.15, with KVM. Hmm, not sure whether it already enables iothreads or not. Sometimes KVM changes certain things from main Qemu tree. > My initial understanding was that sleep_on_page is 'called' by > __lock_page, which is usually called by file_read . > So, i assumed that sleep_on_page is for the page-lock contention. > My primary confusion is with the interpretation of latencytop output. > 2 seconds even for I/O to complete seems awfully long. Apologize, I haven't done complete call trace that leads to sleep_on_page(), so I can't offer my own personal view. The thing that cross my mind is to use tool like blktrace to confirm those numbers. AFAIK too, sometimes Qemu (or KVM) assume doing synchronized I/O. Maybe that also explain the numbers you get. Try to read qemu/kvm manual page and switch to async mode. NB: are you doing read from journalling filesystem? I guess so...if yes, which mode do you use i.e ext3 write back etc. -- 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
