Re: [PATCH 2/2] drm/i915: optimize the shmem_pwrite slowpath handling

Chris Wilson
2012-11-15T15:02:09Z

On Thu, 15 Nov 2012 15:40:06 +0100, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> Since we drop dev->struct_mutex when going through the slowpath, the
> object might have been moved out of the cpu domain. Hence we need to
> clflush the entire object to ensure that after the ioctl returns,
> everything is coherent again (interwoven writes are ill-defined
> anyway).
>
> But we only need to do this if we start in the cpu domain and the
> object requires flushing for coherency. So don't do the flushing if
> the object is coherent anyway or if we've done in-line clfushing
> already.
>
> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Technically true, but we do we care enough to add the extra line of
confusion? Not sold on this one yet, maybe it will be neater in future?
-Chris

--
Chris Wilson, Intel Open Source Technology Centre