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    SubjectRe: 2.6.36 io bring the system to its knees
    On Tue, Nov 02, 2010 at 07:47:15AM -0400, Sanjoy Mahajan wrote:
    > Chris Mason <> wrote:
    > > > This has the appearance of some really bad IO or VM latency
    > > > problem. Unfixed and present in stable kernel versions going from
    > > > years ago all the way to v2.6.36.
    > >
    > > Hmmm, the workload you're describing here has two special parts.
    > > First it dramatically overloads the disk, and then it has guis doing
    > > things waiting for the disk.
    > I think I see this same issue every few days when I back up my hard
    > drive to a USB hard drive using rsync. While the backup is running, the
    > interactive response is bad. A reproducible measurement of the badness
    > is starting an rxvt with F8 (bound to "rxvt &" in my .twmrc). Often it
    > takes 8 seconds for the window to appear (as it just did about 2 minutes
    > ago)! (Starting a subsequent rxvt is quick.)

    So this sounds like the backup is just thrashing your cache. Latencies
    starting an app are less surprising than latencies where a running app
    doesn't respond at all.

    Does rsync have the option to do an fadvise DONTNEED?


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