Re: [Intel-gfx] [RFC 0/2] drm/i915/ttm: Evict and store of compressed object

["Hellstrom, Thomas" <thomas.hellstrom@intel.com>]

Hi, Christian,

On Mon, 2022-02-07 at 12:41 +0100, Christian König wrote:
> Am 07.02.22 um 10:37 schrieb Ramalingam C:
> > On flat-ccs capable platform we need to evict and resore the ccs data
> > along with the corresponding main memory.
> > 
> > This ccs data can only be access through BLT engine through a special
> > cmd ( )
> > 
> > To support above requirement of flat-ccs enabled i915 platforms this
> > series adds new param called ccs_pages_needed to the ttm_tt_init(),
> > to increase the ttm_tt->num_pages of system memory when the obj has
> > the
> > lmem placement possibility.
> 
> Well question is why isn't the buffer object allocated with the extra
> space in the first place?

That wastes precious VRAM. The extra space is needed only when the bo
is evicted.

We've had a previous short disussion on this here:
https://lists.freedesktop.org/archives/dri-devel/2021-August/321161.html

Thanks,
Thomas


> 
> Regards,
> Christian.
> 
> > 
> > This will be on top of the flat-ccs enabling series
> > https://patchwork.freedesktop.org/series/95686/
> > 
> > For more about flat-ccs feature please have a look at
> > https://patchwork.freedesktop.org/patch/471777/?series=95686&rev=5
> > 
> > Testing of the series is WIP and looking forward for the early review
> > on
> > the amendment to ttm_tt_init and the approach.
> > 
> > Ramalingam C (2):
> >    drm/i915/ttm: Add extra pages for handling ccs data
> >    drm/i915/migrate: Evict and restore the ccs data
> > 
> >   drivers/gpu/drm/drm_gem_vram_helper.c      |   2 +-
> >   drivers/gpu/drm/i915/gem/i915_gem_ttm.c    |  23 +-
> >   drivers/gpu/drm/i915/gt/intel_migrate.c    | 283 +++++++++++-------
> > ---
> >   drivers/gpu/drm/qxl/qxl_ttm.c              |   2 +-
> >   drivers/gpu/drm/ttm/ttm_agp_backend.c      |   2 +-
> >   drivers/gpu/drm/ttm/ttm_tt.c               |  12 +-
> >   drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c |   2 +-
> >   include/drm/ttm/ttm_tt.h                   |   4 +-
> >   8 files changed, 191 insertions(+), 139 deletions(-)
> > 
> 

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