[Intel-gfx] [PATCH i-g-t 01/10] gem_wsim: Rip out userspace balancing

[Chris Wilson]

Quoting Tvrtko Ursulin (2020-06-18 08:40:25)
> 
> On 18/06/2020 08:14, Chris Wilson wrote:
> > Quoting Tvrtko Ursulin (2020-06-17 17:01:11)
> >> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> >>
> >> Evaluation of userspace load balancing options was how this tool started
> >> but since we have settled on doing it in the kernel.
> >>
> >> Tomorrow we will want to update the tool for new engine interfaces and all
> >> this legacy code will just be a distraction.
> >>
> >> Rip out everything not related to explicit load balancing implemented via
> >> context engine maps and adjust the workloads to use it.
> > 
> > Hmm, if this is on the table, should we also then restrict
> > load-balancing wsim to gen11+ so that we can use the timed loops rather
> > nop batches? That would be a huge selling point, and I'll just keep an
> > old checkout around for nop load balancing with all the trimmings.
> 
> That was my plan for the next step yes. Just taking your patch without 
> further changes would already make it work I think. But also at some 
> point I want to convert the engine selection (and engine naming in 
> descriptors) to class:instance.
> 
> Why do you need the nop/old balancing stuff? I would hope going forward 
> we only need to compare current balancing against any changes. So I'd 
> really like to remoev the userspace balancing stuff.

There are still some cases where i915 is beaten by plain old contexts,
usually that is a combination of semaphores and interrupt latency, but
some I just don't understand. There is still an uncomfortably large
variation between kernel releases, and comparing the regressions in
different balancers is useful to narrow down the problem.
-Chris