[Intel-gfx] [PATCH] drm/i915: Separate fence pin counting from normal bind pin counting

[Eugeni Dodonov]

On 06/06/2011 03:10 AM, Chris Wilson wrote:
> In order to correctly account for reserving space in the GTT and fences
> for a batch buffer, we need to independently track whether the fence is
> pinned due to a fenced GPU access in the batch from from whether the
> buffer is pinned in the aperture. Currently we count the fenced as
> pinned if the buffer has already been seen in the execbuffer. This leads
> to a false accounting of available fence registers, causing frequent
> mass evictions. Worse, if coupled with the change to make
> i915_gem_object_get_fence() report EDEADLK upon fence starvation, the
> batchbuffer can fail with only one fence required...
>
> In order to trigger the false accounting, one can simply submit two
> batches containing the same 18 [2*(num_avail_fences+1)] buffers. In the
> first batch, the first 9 buffers require a fence. In the second batch,
> the latter half require a fence. Due to prior pinning of all buffers,
> which also then pins the fence register, this results in the false
> starvation and forced eviction of the currently active buffers.
> Admittedly, such batch buffers require pipelined fencing...
>
> Note, this fixes a severe performance regression with heavy fenced BLT
> users such as the Cairo traces firefox-planet-gnome and midori-zoomed on
> gen3.
>
> Signed-off-by: Chris Wilson<chris at chris-wilson.co.uk>
> Cc: Daniel Vetter<daniel.vetter at ffwll.ch>
> Reviewed-by: Daniel Vetter<daniel.vetter at ffwll.ch>
> ---
>   drivers/gpu/drm/i915/i915_drv.h            |   21 ++++
>   drivers/gpu/drm/i915/i915_gem.c            |    7 +-
>   drivers/gpu/drm/i915/i915_gem_execbuffer.c |  161 +++++++++++++++++++---------
>   drivers/gpu/drm/i915/intel_display.c       |   21 +++-
>   4 files changed, 155 insertions(+), 55 deletions(-)
>

Bringing back this June's thread to live, I noticed that this patch 
never made it to the kernel.. is anything still pending on it by a 
chance, or it was just MIA?

-- 
Eugeni Dodonov