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    SubjectRe: 2.6.36 io bring the system to its knees
    > So this sounds like the backup is just thrashing your cache.

    I think it's more than that. Starting an rxvt shouldn't take 8 seconds,
    even with a cold cache. Actually, it does take a while, so you do have
    a point. I just did

    echo 3 > /proc/sys/vm/drop_caches

    and then started rxvt. That takes about 3 seconds (which seems long,
    but I don't know wherein that slowness lies), of which maybe 0.25
    seconds is loading and running 'date':

    $ time rxvt -e date
    real 0m2.782s
    user 0m0.148s
    sys 0m0.032s

    The 8-second delay during the rsync must have at least two causes: (1)
    the cache is wiped out, and (2) the rxvt binary cannot be paged in
    quickly because the disk is doing lots of other I/O.

    Can the system someknow that paging in the rxvt binary and shared
    libraries is interactive I/O, because it was started by an interactive
    process, and therefore should take priority over the rsync?

    > Does rsync have the option to do an fadvise DONTNEED?

    I couldn't find one. It would be good to have a solution that is
    independent of the backup app. (The 'locate' cron job does a similar
    thrashing of the interactive response.)


    `Until lions have their historians, tales of the hunt shall always
    glorify the hunters.' --African Proverb

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