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Date: Tue, 14 Jul 2009 09:23:01 -0700
Message-ID: <7d3530220907140923s590847dcs2128ca4e33dcc13f@mail.gmail.com>
From: John Floren <slawmaster@gmail.com>
To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net>
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Subject: Re: [9fans] ugliness in vesa
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On Tue, Jul 14, 2009 at 9:10 AM, erik quanstrom<quanstro@coraid.com> wrote:
>> I believe I properly applied the pat patch, but I'm not really seeing
>> any improvement. At least, it still takes fully two seconds to bring
>> one large window in front of another.
>
> that's because the screen is not double-buffered. =C2=A0pat or mtrr do
> not improve reads from video memory. =C2=A0there is no such thing
> as read combining. =C2=A0and on some nvidia cards, especially the pcie
> ones i have, reads from video memory are really slow.

I haven't done much graphics hacking, but I remember that implementing
double buffering in the few programs I wrote was extremely easy and
gave a really cheap performance boost. Would it be similarly easy to
add double-buffering to the driver? I'm willing to put in some time,
but not too much or Ron will smack me ;)

>
>> Did you change anything with the nvidia driver when applying the mtrr
>> patch? I was under the impression that the applied patch only affected
>> the vesa driver.
>
> only the one line previously posted. =C2=A0(a similar change was made to =
the
> vesa driver, of course.)
>
> - erik
>

As I'm reading it, the change to vganvidia.c you posted above
(re-pasted below) does pat stuff. Am I confused? I don't think pat and
mtrr are the same thing...

nv.dmabase =3D (void*)vmappat(scr->paddr + scr->storage - 128*1024,
128*1024, PATWT);


John
--=20
"I've tried programming Ruby on Rails, following TechCrunch in my RSS
reader, and drinking absinthe. It doesn't work. I'm going back to C,
Hunter S. Thompson, and cheap whiskey." -- Ted Dziuba