Unmapped I/O

[Konstantin Belousov]

On Wed, Dec 19, 2012 at 04:52:40PM +0000, Poul-Henning Kamp wrote:
> --------
> In message <50D1ECC5.2070209 at freebsd.org>, Julian Elischer writes:
> 
> >yeah.. Bill Jolitz had patches for this in 92 ... that disappeared 
> >with him.
> 
> You know, I've never seen a shred of evidence supporting that claim
> or any of the many similarly improbable claims Bill Jolitz made, and
> in this particular case I very much did look for such evidence.

This is definitely not a discussion I hoped for.

Still, the i386 cannot have much benefit from the unmapped buffers,
just because thre is no facilities similar to the direct map for amd64.
i386 must use transient mapping even for unmapped buffers to copy
the data to the usermode.

Also, as I understand the history, VMIO buffers, or unified page/buffer
cache, only appeared in the FreeBSD.
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