On Sun, 2009-08-02 at 16:08 +0200, Michel Dänzer wrote:
> On Sun, 2009-08-02 at 15:56 +0200, Jerome Glisse wrote:
> > On Sun, 2009-08-02 at 08:53 +1000, Dave Airlie wrote:
> > > On Sun, Aug 2, 2009 at 12:48 AM, Jerome Glisse<gli...@freedesktop.org> 
> > > wrote:
> > > >
> > > > Corollary the TTM priority stuff is i believe a wrong idea
> > > > for radeon (could be usefull for others GPU but i don't have
> > > > such feeling). So i would like to be able to disable it and
> > > > move the knowledge in radeon kernel driver, here is my thinking
> > > > on that :
> > > >
> > > > domain provided by userspace is a tip given to the kernel
> > > > Then the kernel driver will be the one to choose where to
> > > > put the buffer. For instance userspace can create an object
> > > > in GTT space because this object will routinely accessed
> > > > by the CPU, but at one point the GPU might need to write to
> > > > it and most of the time we really want to put all buffer
> > > > the GPU write to into VRAM. So kernel could move the object
> > > > to VRAM for doing the rendering.
> > > >
> > > > Any thoughts on that ?
> > > 
> > > The whole problem with aperture sizing and when to flush
> > > optimally is quite messy when things are just hints. Maybe
> > >  you need to redesign CS with stream break points, I think
> > > Thomas did or was thinking about this for Openchrome.
> > 
> > Nothings change for counting how memory a cs needs, it makes
> > the code simpler as there is only one domain and its up to
> > ddx to properly ask for vram on object which are dst. So
> > accounting for gtt/vram use is the same, code is just simpler.
> 
> The way it's done now, the kernel can transparently put a source BO in
> GTT if there's no space in VRAM. How would that be handled with your
> idea?

Same, kernel can decide to put things in vram or gtt, domain given
by userspace is just a hint, moreover i added creation time stamp
while adding statistics stuff to kms and i think kernel could use
that to decide wether it's worth it or not to put a bo in vram,
also kernel could use others informations for that such as if
the buffer is a render buffer, ... Well given enough informations
(object life time, is it a render buffer, hint given by userspace,
...) kernel could make a good guess on where it's best to put a bo.

> > Also while testing, it seems current code space checking
> > fails hard with 16M vram, 16M gtt
> > VRAM usage:
> > 7M for fbcon, 7M for front buffer, so pretty much no vram left
> 
> I'm working on fixing the fbcon BO always being pinned in VRAM, almost
> done. :)

Thanks a lot for looking into that :)

Cheers,
Jerome


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