Re: Putrid Elevator Behavior 2.4.18/19

Jeff V. Merkey (
Mon, 25 Mar 2002 18:16:45 -0700

> > The elevator starvation change went into 2.4.19-pre1 I think.
> > It shouldn't affect the problem which you've described - that
> > change improved the situation where tasks were sleeping for
> > long periods when they want to insert new requests. But the
> > problem which you're observing appears to affect already-inserted
> > requests.
> >
> > "Several minutes" is downright odd. From your description
> > it seems that all the requests are writes, but some of the
> > writes (at a remote end of the disk) are being bypassed far
> > too many times.
> >
> > The bypass count _is_ tunable. Although it sounds like the logic
> > has come unstuck in some manner, it would be interesting if
> > changing the elevator latency parameters for that queue affected
> > the situation.
> >
> > Have you experimented with `elvtune -r NNN /dev/foo' and
> > `elvtune -w NNN /dev/foo'?
> No, but I will test this tonight. I am in tonight working on
> this problem until I run it down.
> Jeff


I have been running a test run against 2.4.19-pre4 (and later) for
over a week non-stop and the elevator problem appears to have been
corrected by this fix. I will update further if the problem



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