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From: "Rob Mueller" <robm@fastmail.fm>
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Subject: Re: Strange load spikes on 2.4.19 kernel
Date: Sat, 12 Oct 2002 12:25:47 +1000
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> > 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

Rob