Re: Putrid Elevator Behavior 2.4.18/19

Mike Fedyk
2002-03-26T01:41:21Z

On Mon, Mar 25, 2002 at 06:16:45PM -0700, Jeff V. Merkey wrote:
> > > 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
> >
>
>
> Andrew,
>
> 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
> resurfaces.
>

That's good news.

Are you still working on the A/B list patch? I'd imagine that it could make
several problems easier to fix in the block layer.

> :-)
>

:)