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

Chris Wilson
2012-11-15T15:37:06Z

On Thu, 15 Nov 2012 16:20:49 +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.
>
> v2: i915_gem_clflush_object already checks whether the object is
> coherent and if so, drops the flushing. Hence we don't need to check
> that ourselves, simplifying the condition.
>
Getting clearer, certainly. How about reversing the order of the
checks so that it reads as
if (used-fast-path && fast-path-no-longer-valid) do_fixup()?
-Chris

--
Chris Wilson, Intel Open Source Technology Centre