[igt-dev] [PATCH i-g-t] lib/i915: Trim ring measurement by one

[Chris Wilson]

Quoting Mika Kuoppala (2019-08-12 12:52:56)
> Chris Wilson <chris at chris-wilson.co.uk> writes:
> 
> > Be a little more conservative in our ring measurement and exclude one
> > batch to leave room in case our user needs to wrap (where a request will
> > be expanded to cover the unused space at the end of the ring).
> >
> 
> did read the wrapping part and that seems to be the case that
> we enlarge the wrapping request.
> 
> However do we lose some coverage on the actual wrap tests?

There's only one with that idea in mind, gem_ringfill(). Which is
already "broken" because it assumes that all engines have the same ring
size, so we will be underfilling most. Could also do with an ALL_ENGINES
mode.

There's nothing that explicitly tries to hit all the possible ways in
which ring wrapping occurs, it tends to fallout of faux-stress tests
like gem_exec_parallel or gem_ctx_create.
-Chris