Re: Poor disk performance in NetBSD DomU, again

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

FYI, I'm making progress on this. It looks like some drives don't like
small requests, and a PV domU sends 32k requests while the same I/O
in the dom0 would send 64k ones.
For some reason, the pagedaemon sends completely disordoned write
requests, so even with disksort a full ring doens't have contigous write
requests and the backend can't aggregate these small requests in larger one
(this may be a problem by itself, even outside of the Xen context).
I'll see if i can make the frontend handle and split 64k requests, so
the domU could use a 64k MAXPHYS like other kernels do.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--