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Thread-Topic: VFS/VM over-runs. Was: Apparent strange disk behaviour in 6.0
Thread-Index: AcWTT3USU9HS5o8OQuap+wkNy4bo4AAEzdwg
From: "Daniel Eriksson" <daniel_k_eriksson@telia.com>
To: "FreeBSD Current" <freebsd-current@FreeBSD.org>
Cc: Julian Elischer <julian@elischer.org>
Subject: RE: VFS/VM over-runs. Was: Apparent strange disk behaviour in 6.0
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Julian Elischer wrote:

> I wonder if there is some tunable that can be changed? or whether it's
> just a bug..
>=20
> I think that a write that finds no buffer space should first free old=20
> unused
> buffers, and if there aren't any it should just wait. =20
> Where's alan when=20
> you need him :-)

This problem has been reported before, both by me and by others.

I'm pretty sure all three of these are symptoms of the same problem:

* "Livelock seen on current with threaded processes"
  Kevin Oberman, June 5th
  http://docs.freebsd.org/cgi/mid.cgi?20050606032025.CC7A35D08

* "Serious I/O problems (bad performance and live-lock)"
  Daniel Eriksson, April 22nd
=20
http://docs.freebsd.org/cgi/mid.cgi?!~!UENERkVCMDkAAQACAAAAAAAAAAAAAAAAA
BgAAAAAAAAA0VcX9IoJqUaXPS8MjT1PdsKAAAAQAAAAKDq8qQ2O9UK7PKMOCt2NqwEAAAAA
  This one has some additional info:
=20
http://docs.freebsd.org/cgi/mid.cgi?!~!UENERkVCMDkAAQACAAAAAAAAAAAAAAAAA
BgAAAAAAAAA0VcX9IoJqUaXPS8MjT1PdsKAAAAQAAAA5xh4prxQBkmZLv9A9nCvPwEAAAAA

* "ciss(4): speed degradation for Compaq Smart Array [3rd edition]"
  Andrey Koklin, April 12th
  http://docs.freebsd.org/cgi/mid.cgi?20050412135029.2d81a216.aka

/Daniel Eriksson