[Intel-gfx] [PATCH igt] igt/gem_exec_latency: Wire up an interloper for preemption

[Michał Winiarski]

On Thu, Oct 26, 2017 at 08:31:27AM +0100, Chris Wilson wrote:
> For measuring the cost of preemption, inject a low priority spinner
> between the two measurements; the difference between the preemption and
> the normal dispatch includes both the cost of the spinner dispatch and
> of preempting it. Close enough for us to estimate the cost of
> preemption, though we don't measure the cost of preemption on the local
> ring!

And as expected, we're seeing more delay with GuC, probably from worker
scheduling delay (~2ms on my SKL if I'm reading the results correctly).

Reviewed-by: Michał Winiarski <michal.winiarski at intel.com>

-Michał

> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> CC: Michał Winiarski <michal.winiarski at intel.com>
> ---
>  tests/gem_exec_latency.c | 88 ++++++++++++++++++++++++++++++++----------------
>  1 file changed, 59 insertions(+), 29 deletions(-)