[igt-dev] [PATCH i-g-t 1/4] i915/perf_pmu: Verify RC6 measurements before/after suspend

[Chris Wilson]

Quoting Tvrtko Ursulin (2020-12-14 15:42:20)
> 
> On 14/12/2020 10:51, Chris Wilson wrote:
> > RC6 should work before suspend, and continue to increment while idle
> > after suspend. Should.
> > 
> > v2: Include a longer sleep after suspend; it appears we are reticent to
> > idle so soon after waking up.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> > ---
> >   tests/i915/perf_pmu.c | 28 +++++++++++++++++++++++++---
> >   1 file changed, 25 insertions(+), 3 deletions(-)
> > 
> > diff --git a/tests/i915/perf_pmu.c b/tests/i915/perf_pmu.c
> > index cb7273142..0b470c1bc 100644
> > --- a/tests/i915/perf_pmu.c
> > +++ b/tests/i915/perf_pmu.c
> > @@ -170,6 +170,7 @@ static unsigned int measured_usleep(unsigned int usec)
> >   #define TEST_RUNTIME_PM (8)
> >   #define FLAG_LONG (16)
> >   #define FLAG_HANG (32)
> > +#define TEST_S3 (64)
> >   
> >   static igt_spin_t * __spin_poll(int fd, uint32_t ctx,
> >                               const struct intel_execution_engine2 *e)
> > @@ -1578,7 +1579,7 @@ test_frequency_idle(int gem_fd)
> >                    "Actual frequency should be 0 while parked!\n");
> >   }
> >   
> > -static bool wait_for_rc6(int fd)
> > +static bool wait_for_rc6(int fd, int timeout)
> >   {
> >       struct timespec tv = {};
> >       uint64_t start, now;
> > @@ -1594,7 +1595,7 @@ static bool wait_for_rc6(int fd)
> >               now = pmu_read_single(fd);
> >               if (now - start > 1e6)
> >                       return true;
> > -     } while (!igt_seconds_elapsed(&tv));
> > +     } while (igt_seconds_elapsed(&tv) <= timeout);
> >   
> >       return false;
> >   }
> > @@ -1636,14 +1637,32 @@ test_rc6(int gem_fd, unsigned int flags)
> >               }
> >       }
> >   
> > -     igt_require(wait_for_rc6(fd));
> > +     igt_require(wait_for_rc6(fd, 1));
> >   
> >       /* While idle check full RC6. */
> >       prev = __pmu_read_single(fd, &ts[0]);
> >       slept = measured_usleep(duration_ns / 1000);
> >       idle = __pmu_read_single(fd, &ts[1]);
> > +
> >       igt_debug("slept=%lu perf=%"PRIu64"\n", slept, ts[1] - ts[0]);
> > +     assert_within_epsilon(idle - prev, ts[1] - ts[0], tolerance);
> > +
> > +     if (flags & TEST_S3) {
> > +             prev = __pmu_read_single(fd, &ts[0]);
> > +             igt_system_suspend_autoresume(SUSPEND_STATE_MEM,
> > +                                           SUSPEND_TEST_NONE);
> > +             idle = __pmu_read_single(fd, &ts[1]);
> > +             igt_debug("suspend=%"PRIu64"\n", ts[1] - ts[0]);
> > +             //assert_within_epsilon(idle - prev, ts[1] - ts[0], tolerance);
> > +     }
> > +
> > +     igt_assert(wait_for_rc6(fd, 5));
> >   
> > +     prev = __pmu_read_single(fd, &ts[0]);
> > +     slept = measured_usleep(duration_ns / 1000);
> > +     idle = __pmu_read_single(fd, &ts[1]);
> > +
> > +     igt_debug("slept=%lu perf=%"PRIu64"\n", slept, ts[1] - ts[0]);
> 
> You plan to leave the C++ bit commented out above and just check it 
> here? Doesn't seem it harms to check twice in the non-S3 case anyway, 
> just asking.

My expectation is that we should have a momentary blip !rc6 during
suspend, and so across suspend we should find mono_raw ~= rc6

However, since it is taking a few seconds for us to start rc6 again
after resume, that clearly fails. I'm not sure why it takes so long, so
I suspect a bug. (Possibly something like we are not entering rc6 until
a heartbeat after resume????)

So the // is my expectation; the current test the reality.
How best to document that?
-Chris