[Intel-gfx] Time, where did it go?

[Chris Wilson]

Quoting Dave Airlie (2020-08-02 18:56:44)
> On Mon, 3 Aug 2020 at 02:44, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> >
> > Lots of small incremental improvements to reduce execution latency
> > which basically offsets the small regressions incurred when compared to
> > 5.7. And then there are some major fixes found while staring agape at
> > lockstat.
> 
> What introduced the 5.7 regressions? are they documented somewhere.

No. There's a 5.8-rc1 bisect (to the merge but not into rc1) for
something in the core causing perf fluctuations, but I have not yet
reproduced that one to bisect into the rc1 merge. [The system that showed
the issue has historically seen strong swings from p-state setup, might
be that again?]. This is from measuring simulated transcode workloads that
we've built up to track KPI. That we can then compare against the real
workloads run by other groups.
 
> What is the goal here, is there a benchmark or application that this
> benefits that you can quantify the benefits?

Entirely motivated by not wanting to have to explain why there's even a
1% regression in their client metrics. They wouldn't even notice for a
few releases by which point the problem is likely compounded and we
suddenly have crisis meetings.
 
> Is the lack of userspace command submission a problem vs other vendors here?

If you mean HW scheduling (which is the bit that we are most in dire need
of for replacing this series), not really, our closest equivalent has not
yet proven itself, at least in previous incarnations, adequate to their
requirements.
-Chris