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    SubjectRe: Strange load spikes on 2.4.19 kernel
    Rob Mueller wrote:
    >
    > > > Filesystem is ext3 with one big / partition (that's a mistake
    > > > we won't repeat, but too late now). This should be mounted
    > > > with data=journal given the kernel command line above, though
    > > > it's a bit hard to tell from the dmesg log:
    > > >
    > >
    > > It's possible tht the journal keeps on filling. When that happens,
    > > everything has to wait for writeback into the main filesystem.
    > > Completion of that writeback frees up journal space and then everything
    > > can unblock.
    > >
    > > Suggest you try data=ordered.
    >
    > We have a 192M journal, and from the dmesg log it's saying that it's got a 5
    > second flush interval, so I can't imagine that the journal is filling, but
    > we'll try it and see I guess.
    >
    > What I don't understand is why the spike is so sudden, and decays so slowly.
    > It's Friday night now, so the load is fairly low. I setup a loop to dump
    > uptime information every 10 seconds and attached the result below. It's
    > running smoothly, then 'bam', it's hit with something big, which then slowly
    > decays off.
    >
    > A few extra things:
    > 1. It happens every couple of minutes or so, but not exactly on any time, so
    > it's not a cron job or anything
    > 2. Viewing 'top', there are no extra processes obviously running when it
    > happens
    >

    If it was this, one would expect it to happen every time you'd written
    0.75 * 192 Mbytes to the filesystem. Which seems about right.

    Easy enough to test though.
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