Re: [Intel-gfx] [PATCH v2 05/21] drm/i915/gt: Skip TLB invalidations once wedged
From: Tvrtko Ursulin
Date: Tue Jul 19 2022 - 03:20:05 EST
On 18/07/2022 17:06, Mauro Carvalho Chehab wrote:
On Mon, 18 Jul 2022 14:45:22 +0100
Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx> wrote:
On 14/07/2022 13:06, Mauro Carvalho Chehab wrote:
From: Chris Wilson <chris.p.wilson@xxxxxxxxx>
Skip all further TLB invalidations once the device is wedged and
had been reset, as, on such cases, it can no longer process instructions
on the GPU and the user no longer has access to the TLB's in each engine.
That helps to reduce the performance regression introduced by TLB
invalidate logic.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 7938d61591d3 ("drm/i915: Flush TLBs before releasing backing store")
Is the claim of a performance regression this solved based on a wedged
GPU which does not work any more to the extend where mmio tlb
invalidation requests keep timing out? If so please clarify in the
commit text and then it looks good to me. Even if it is IMO a very
borderline situation to declare something a fix.
Indeed this helps on a borderline situation: if GT is wedged, TLB
invalidation will timeout, so it makes sense to keep the patch with a
comment like:
drm/i915/gt: Skip TLB invalidations once wedged
Skip all further TLB invalidations once the device is wedged and
had been reset, as, on such cases, it can no longer process instructions
on the GPU and the user no longer has access to the TLB's in each engine.
So, an attempt to do a TLB cache invalidation will produce a timeout.
That helps to reduce the performance regression introduced by TLB
invalidate logic.
Yeah that is better but whether bothering stable with it is the
question. Wedged GPU means constant endless -EIO to userspace so very
hard to imagine that after a TLB invalidation timeout or two there would
be further ones. But okay, it's tiny so fine I guess.
Regards,
Tvrtko