Re: Fixing excessive shootdowns during FFS read (kern/53124) on x86

[Joerg Sonnenberger <joerg%bec.de@localhost>]

On Sun, Mar 25, 2018 at 07:24:25PM +0200, Maxime Villard wrote:
> Le 25/03/2018 à 17:27, Joerg Sonnenberger a écrit :
> > The other question is whether we can't just use the direct map for this
> > on amd64 and similar platforms?
> 
> no, because nothing guarantees the physical pages are contiguous.

At least for ubc_zerorange, they certainly don't have to be. For
ubc_uiomove, it's a bit more work to split the IO vector, but certainly
feasible as well. Alternatively, propagate it down to uiomove to allow
using *two* IO vectors.

Joerg