Subject: "buffer cache locking" meets "soft updates"
To: None <>
From: Ethan Solomita <>
List: tech-kern
Date: 10/27/1999 00:32:41
	I've been trying to come up to speed with Soft Updates. The company I
work for is looking to use NetBSD, and we're hoping to be able to use
Soft Updates with it. If you don't know about it, the quicky summary:
Kirk McKusick is adding some sophistication to ffs which will eliminate
the need for nearly all synchronous meta-data writes, without switching
over to a log-based filesystem.

	McKusick's recent and upcoming development requires changes to the
buffer cache locking mechanism. Within FreeBSD, he has changed it so
that instead of being a pair of flags, it's a real lock_t. In
particular, he said that he is looking for their recursive, upgradeable,
downgradeable, shareable and drainable features.

	I understand that there's some major buffer cache work going on now,
but beyond that I'm ignorant of any (all?) details. However I'd *really*
like to see a number of the features which Kirk is planning come to
fruition within NetBSD. In particular, one of the features will allow an
un-clean filesystem to be mounted without first running fsck -- instead
fsck is run in the background. ie. the boot up performance of a
log-based file system with ffs.

	So, has this come up before? Opinions, anyone??

	-- Ethan

P.S. This *is* an offer to help with the implied coding