Re: vnode_has_large_blocks() (vnd.c rev 1.255)

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

On Sun, Sep 09, 2018 at 10:15:20AM -0000, Michael van Elst wrote:
> I'm about to commit a change that uses mnt_stat.f_iosize instead. For
> backing store on FFS that at least allows the faster method for virtual
> disks with sectors of at least the fragment size, and I don't think we
> can safely do smaller I/O.

I strongly dissagree. I have 512-byte-sectors domUs running for years on a
dom0 with 64k blocks/8k fragements. This works ! I'm I'm probably not the
only one, as this has been this way since we have dom0 support.
It's very unlikely that others have requested a 512-byte fragments FFS
for their domUs backing store.

The performance penaltly of VOP_READ/VOP_WRITE is just inacceptable
for a Xen setup.

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