On Mon, 18 Jul 2022 14:39:17 +0100 Tvrtko Ursulin tvrtko.ursulin@linux.intel.com wrote:
On 14/07/2022 13:06, Mauro Carvalho Chehab wrote:
From: Chris Wilson chris.p.wilson@intel.com
Don't flush TLBs when the buffer is only used in the GGTT under full control of the kernel, as there's no risk of concurrent access and stale access from prefetch.
We only need to invalidate the TLB if they are accessible by the user. That helps to reduce the performance regression introduced by TLB invalidate logic.
Cc: stable@vger.kernel.org Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")
Do we really need or want stable and fixes on this one?
What do we think the performance improvement is, given there's very little in GGTT, which is not mapped via PPGTT as well?
I think it is safe, but part of me would ideally not even want to think about whether it is safe, if the performance improvement is non-existent. Which I can't imagine how there would be?
Makes sense. Patch 6 actually ends removing the code doing that, so I'll just fold this patch with patch 6, in order to avoid adding something that will later be removed.
Regards, Mauro