Subject: Re: Limiting disk I/O?
To: Tech-kern <email@example.com>
From: Joerg Sonnenberger <firstname.lastname@example.org>
Date: 11/12/2007 13:48:58
On Mon, Nov 12, 2007 at 02:44:40PM +0200, Jukka Marin wrote:
> On Mon, Nov 12, 2007 at 01:16:39PM +0100, Joerg Sonnenberger wrote:
> > Have you tried using a different IO scheduler?
> No, but I'm willing to try.
Look for BUFQ_PRIOCSCAN and BUFQ_READPRIO in GENERIC. They are not
enabled by default. kern.bufq.strategies lists the available strategies.
> # dkctl ld1 strategy
> dkctl: /dev/rld1d: DIOCGSTRATEGY: Inappropriate ioctl for device
I don't know whether a driver has to do anything to get this, others can
comment on that I guess.
> Softdep is a big win most of the time. Disabling it "fixes" the problem I
> described, but it also makes all disk I/O much slower.
It might help to modify vfs.sync in that case to force softdep to be
less aggressive. It can also help to increate kern.maxvnodes.