Re: Serious WAPL performance problems

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

> I suggest trying the latest 5.1 sources
So I set up a test machine with the latest 5.1_STABLE snapshot.
It differs from the real server in a couple of points[*], but exhibits similar 
behaviour.
On a 16k fsbsize FFSv2, 5.1 softdep takes 1.25s for the svn update. Ten
seconds later, there is a two second burst of disc activity.
5.1 log takes about 5s, 6.0 log also.
On a 8k fsbsize FFSv1, 5.1 softdep also takes 1.25s, log takes 7s as on 6.0.

I would regard this as a major performance regression.
So, what can I tune to improve ist?


* The following differences come to my mind:
The server is amd64, the test machine i386. The server uses RAIDs accross 
mpt(4) SAS discs, the test machine one plain SATA drive.
Above, "6.0" means a 6.0_RELEASE kernel with 5.1_STABLE userland.