[Nouveau] [PATCH 1/3] drm/radeon: remove AGP support

Michel Dänzer michel at daenzer.net
Wed May 13 07:52:28 UTC 2020

On 2020-05-13 9:46 a.m., Christian König wrote:
> Am 12.05.20 um 23:12 schrieb Alex Deucher:
>> On Tue, May 12, 2020 at 4:52 PM Roy Spliet <nouveau at spliet.org> wrote:
>>> I'll volunteer to be the one asking: how big is this performance
>>> difference? Have any benchmarks been run before and after removal of AGP
>>> GART code on affected nouveau/radeon systems? Or is this code being
>>> dropped _just_ because it's cumbersome, with no regard for metrics that
>>> determine the value of AGP GART support?
>> I don't think anyone has any solid numbers, just anecdotal from
>> memory.  I certainly don't have any functional AGP systems at this
>> point.  It's mostly just cumbersome and would allow us to clean ttm
>> and probably improve stability at the same time.  At least on the
>> radeon side, the only native AGP cards were r1xx, r2xx, and some of
>> the early r3xx boards.  Once we switched to pcie mid-way through r3xx,
>> everything was native pcie and the AGP cards used a pcie to AGP bridge
>> chip so they had a decent on chip MMU.  Those older cards topped out
>> at maybe 32 or 64 MB of vram, so they are going to be hard pressed to
>> deal with modern desktops anyway.  No idea what sort of GART
>> capabilities NV AGP hardware at this time had.
> I could only test with an old x86 Mac and an r3xx generation hw and in
> this case making the switch didn't had any noticeable effect at all.
> But I didn't do more than playing around with the desktop effects and
> playing a video.

Yeah, that's not enough to see a difference. Try an OpenGL game, or even
just glxgears.

Earthling Michel Dänzer               |               https://redhat.com
Libre software enthusiast             |             Mesa and X developer

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