linux-kernel - Re: [PATCH] fixes to drm-next

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Message-ID: <20111213164031.GA32052@phenom.dumpdata.com>
Date:	Tue, 13 Dec 2011 11:40:31 -0500
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Thomas Hellstrom <thellstrom@...are.com>
Cc:	Jerome Glisse <j.glisse@...il.com>, linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org, bskeggs@...hat.com
Subject: Re: [PATCH] fixes to drm-next - TTM DMA code (v1)

On Tue, Dec 13, 2011 at 05:23:30PM +0100, Thomas Hellstrom wrote:
> On 12/13/2011 05:07 PM, Jerome Glisse wrote:
> >On Mon, Dec 12, 2011 at 03:09:26PM -0500, Konrad Rzeszutek Wilk wrote:
> >>Jerome pointed me to some accounting error in the DMA API debugging code and
> >>while I can't figure it out yet, I did notice some extreme slowness - which
> >>is due to the nouveau driver calling the unpopulate (now that unbind +
> >>unpopulate are squashed) quite a lot (this is using Gnome Shell - I think GNOME2
> >>did not have those issues but I can't recall).
> >>
> >>Anyhow these patches fix the 50% perf regression I saw and also some minor bugs
> >>that I noticed.
> >>
> >Gonna review those today and test them.
> >
> >Cheers,
> >Jerome
> Hi!
> 
> I'm not whether any drivers are still using the AGP backend?

Uh, probably they do if the cards are AGP?
The problem I encountered was with an PCIe Nvidia card:

01:00.0 VGA compatible controller: nVidia Corporation G84 [GeForce 8600 GT] (rev a1

> Calling unpopulate / (previous clear) each time unbind is done
> should be quite
> inefficient with that one, as AGP sets up its own data structures
> and copies page tables
> on each populate. That should really be avoided unless there is a
> good reason to have it.

nouveau_bo_rd32 and nv50_crtc_cursor_set showed up as the callers that
were causing the unpopulate calls. It did happen _a lot_ when I moved the
cursor madly.
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