On 11/10/2019 16:11, Chris Wilson wrote:
Quoting Tvrtko Ursulin (2019-10-11 15:56:35)
On 10/10/2019 08:14, Chris Wilson wrote:
If we do find ourselves with an idle barrier inside our active while
waiting, attempt to flush it by emitting a pulse using the kernel
context.
The point of this one completely escapes me at the moment. Idle barriers
are kept in there to be consumed by the engine_pm parking, so if any
random waiter finds some (there will always be some, as long as the
engine executed some user context, right?),
Not any random waiter; the waiter has to be waiting on a context that
was active and so setup a barrier.
why would it want to handle
them? Again just to use the opportunity for some house keeping? But what
if the system is otherwise quite busy and a low-priority client just
happens to want to wait on something silly?
There's no guarantee that it will ever be flushed. So why wouldn't we
use a low priority request to give a semblance of forward progress and
give a guarantee that the wait will complete.
It's a hypothetical point, there are no waiters that need to wait upon
their own barriers at present. We are just completing the picture for
idle barrier tracking.
Hm I was mistakenly remembering things like rpcs reconfiguration would
wait on ce->active, but I forgot about your trick with putting kernel
context request on an user timeline.
I guess it is fine there, but since, and as you have said, it is
hypothetical, then this patch is dead code and can wait.
Regards,
Tvrtko
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