[Intel-gfx] [PATCH] drm/i915: Only initialize partially filled pagetables

[Matthew Auld]

On 8 September 2017 at 19:16, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> If we know that we will completely fill a pagetable (i.e. we are
> inserting a complete set of 512 pages), we can skip prefilling that PT
> with scratch entries. If we have to abort the insertion prior to writing
> the real entries, we will teardown the pagetable and remove it from the
> page directory (so that we will restart the allocation next time).
>
> We could do similar tricks for the PD and PDP, but the likelihood of a
> single insertion covering the entire 512 entries diminishes, as do the
> cycle savings. The saving are even greater (relatively) when we are
> preallocating page tables for huge pages, as then we never need to fill
> the page table.
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Matthew Auld <matthew.auld at intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Reviewed-by: Matthew Auld <matthew.auld at intel.com>