Subject: Re: BUFQ_FCFS for XENU kernels?
To: Thor Lancelot Simon <>
From: Manuel Bouyer <>
List: tech-kern
Date: 03/01/2006 22:03:16
On Wed, Mar 01, 2006 at 03:19:13PM -0500, Thor Lancelot Simon wrote:
> I *think* requests passing through xbd will always be sorted by the
> underlying device driver in the dom0 OS.  Certainly if the requests
> are heading for something like a vnd, sorting them in the domU kernel
> is not the right thing to do, since they could then be sorted *three*
> times.
> But I cannot build a domU kernel (on the 3.0) branch with "options BUFQ_FCFS"
> defined.  The other BUFQ options seem to work (READPRIO, PRIOCSCAN) but FCFS
> produces a compile-time error in xbd.  I do not quite see why.
> Does xbd already default to BUFQ_FCFS?  We should either make it so or
> make BUFQ_FCFS the default with "options BUFQ_FCFS" in the XENU kernel.

If I read xbdinit() properly, fcfs is already the default, and can't be
changed. Maybe xbd didn't get updated when these options were added.

Manuel Bouyer <>
     NetBSD: 26 ans d'experience feront toujours la difference