Since clock_gettime() should be a fixed overhead that adds to the
latency result, subtract it from the result.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
In order to keep the latency as low as possible for the idle load, we
need to keep the CPU awake. Otherwise we end up with the busy workload
having lower latency than the idle workload!
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Also useful to know how much worse than baseline the latency is when the
gem load is applied. For slower systems, presenting in nanoseconds makes
it hard to read, so switch to microseconds for output.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Instead of measuring the wakeup latency of a GEM client, we turn the
tables here and ask what is the wakeup latency of a normal process
competing with GEM. In particular, a realtime process that expects
deterministic latency.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
