Unmapped I/O

[Konstantin Belousov]

On Tue, Dec 25, 2012 at 08:42:27PM +0000, Robert Watson wrote:
> On Wed, 19 Dec 2012, Alan Cox wrote:
> 
> >> Are the machines that don't have a direct map performance critical? My 
> >> expectation is that they are legacy or embedded.  This seems like a great 
> >> project to do when the rest of the pieces are stable and fast. Until then 
> >> they could just use something like pbufs?
> >
> > I think the answer to your first question depends entirely on who you are. 
> > :-)  Also, at the low-end of the server space, there are many people trying 
> > to promote arm-based systems.  While FreeBSD may never run on your arm-based 
> > phone, I think that ceding the arm-based server market to others will be a 
> > strategic mistake.
> >
> > Alan
> >
> > P.S. I think we're moving the discussion to far away from kib's original, so 
> > I suggest changing the subject line on any follow ups.
> 
> Despite moving the discussion a little further away: MIPS-based
> systems, a direct mapped map segment (e.g., kseg, xkphys, etc) is part
> of the underlying design and doesn't rely on any TLB entries at all.
> We run much of the kernel from direct map regions to avoid causing TLB
> pressure.
Yes, as it was noted already, 32bit mips kseg is not much usable on
the mips systems with more than 1GB of RAM. But Alan' another patch,
with, I believe, small modification, could provide the gain there too.
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