Quoting Mika Kuoppala (2020-06-16 10:03:19)
> Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
>
> > A couple of very simple tests to ensure that the basic properties of
> > per-engine busyness accounting [0% and 100% busy] are faithful.
> >
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/gt/selftest_engine_pm.c | 94 ++++++++++++++++++++
> > drivers/gpu/drm/i915/gt/selftest_rps.c | 5 ++
> > 2 files changed, 99 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/selftest_engine_pm.c b/drivers/gpu/drm/i915/gt/selftest_engine_pm.c
> > index cbf6b0735272..fb0fd8a7db9a 100644
> > --- a/drivers/gpu/drm/i915/gt/selftest_engine_pm.c
> > +++ b/drivers/gpu/drm/i915/gt/selftest_engine_pm.c
> > @@ -7,6 +7,99 @@
> > #include "i915_selftest.h"
> > #include "selftest_engine.h"
> > #include "selftests/igt_atomic.h"
> > +#include "selftests/igt_flush_test.h"
> > +#include "selftests/igt_spinner.h"
> > +
> > +static int live_engine_busy_stats(void *arg)
> > +{
> > + struct intel_gt *gt = arg;
> > + struct intel_engine_cs *engine;
> > + enum intel_engine_id id;
> > + struct igt_spinner spin;
> > + int err = 0;
> > +
> > + /*
> > + * Check that if an engine supports busy-stats, they tell the truth.
> > + */
> > +
> > + if (igt_spinner_init(&spin, gt))
> > + return -ENOMEM;
> > +
> > + GEM_BUG_ON(intel_gt_pm_is_awake(gt));
> > + for_each_engine(engine, gt, id) {
> > + struct i915_request *rq;
> > + ktime_t de;
> > + u64 dt;
> > +
> > + if (!intel_engine_supports_stats(engine))
> > + continue;
> > +
> > + if (!intel_engine_can_store_dword(engine))
> > + continue;
> > +
> > + if (intel_gt_pm_wait_for_idle(gt)) {
> > + err = -EBUSY;
> > + break;
> > + }
> > +
> > + preempt_disable();
> > + dt = ktime_to_ns(ktime_get());
> > + de = intel_engine_get_busy_time(engine);
> > + udelay(100);
> > + de = ktime_sub(intel_engine_get_busy_time(engine), de);
> > + dt = ktime_to_ns(ktime_get()) - dt;
> > + preempt_enable();
> > + if (de > 10) {
>
> 10 is from stetson?
>
> Well I would say it is strict enough.
>
> The signed de just makes me nervous, so de < 0 too?
de < 0 would be nasty, monotonic going backwards, so yeah.
-Chris
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