Re: [igt-dev] [PATCH i-g-t 1/3] tests/perf_pmu: Compare against requested freq in frequency subtest

["Dixit, Ashutosh" <ashutosh.dixit@intel.com>]

On Thu, 02 Mar 2023 05:50:36 -0800, Tvrtko Ursulin wrote:
>
> On 02/03/2023 13:37, Tvrtko Ursulin wrote:
> >

Hi Tvrtko,

> > On 15/02/2023 04:02, Dixit, Ashutosh wrote:
> >> On Wed, 11 Jan 2023 01:54:59 -0800, Tvrtko Ursulin wrote:
> >>>
> >> Sorry I completely missed your reply and only just saw it again. People
> >> needing a recap of the previous discussion can see it here:
> >>
> >> https://patchwork.freedesktop.org/patch/512274/?series=110574&rev=3#comment_933447
> >>
> >>> On 10/01/2023 19:47, Ashutosh Dixit wrote:
> >>>> After the i915 commit 95ccf312a1e4f ("drm/i915/guc/slpc: Allow SLPC to
> >>>> use
> >>>> efficient frequency"), FW uses the requested freq as the efficient freq
> >>>> which can exceed the max freq set. Therefore, in the "min freq" part
> >>>> of the
> >>>> igt@perf_pmu@frequency subtest, compare the requested freq reported by
> >>>> PMU
> >>>> not against the set freq but against the requested freq reported in
> >>>> sysfs.
> >>>>
> >>>> v2: Remove previously added delays. GuC FW is now updated to set
> >>>> min/max
> >>>>       freq in top half so delays are not needed
> >>>> v3: Increase tolerance between measured and requested freq to 10% to
> >>>>       account for sporadic failures due to dynamically changing
> >>>> efficient
> >>>>       freq. Also document the changes in code.
> >>>>
> >>>> Bug: https://gitlab.freedesktop.org/drm/intel/-/issues/6806
> >>>> Signed-off-by: Ashutosh Dixit <ashutosh.dixit@intel.com>
> >>>> ---
> >>>>    tests/i915/perf_pmu.c | 12 ++++++++++--
> >>>>    1 file changed, 10 insertions(+), 2 deletions(-)
> >>>>
> >>>> diff --git a/tests/i915/perf_pmu.c b/tests/i915/perf_pmu.c
> >>>> index f363db2ba13..f9ef89fb0b3 100644
> >>>> --- a/tests/i915/perf_pmu.c
> >>>> +++ b/tests/i915/perf_pmu.c
> >>>> @@ -1546,7 +1546,7 @@ test_interrupts_sync(int gem_fd)
> >>>>    static void
> >>>>    test_frequency(int gem_fd)
> >>>>    {
> >>>> -    uint32_t min_freq, max_freq, boost_freq;
> >>>> +    uint32_t min_freq, max_freq, boost_freq, min_req;
> >>>>     uint64_t val[2], start[2], slept;
> >>>>     double min[2], max[2];
> >>>>     igt_spin_t *spin;
> >>>> @@ -1587,6 +1587,7 @@ test_frequency(int gem_fd)
> >>>>         min[0] = 1e9*(val[0] - start[0]) / slept;
> >>>>     min[1] = 1e9*(val[1] - start[1]) / slept;
> >>>> +    min_req = igt_sysfs_get_u32(sysfs, "gt_cur_freq_mhz");
> >>>
> >>> So remove all of the above three igt_sysfs_set_u32 and test still passes
> >>> right? What it is testing then?
> >>
> >> Yes, so since enabling efficient freq (RPe) has broken the kernel ABI was
> >> cannot test that the PMU measured freq is min_freq. All we can do, fwiw,
> >> is
> >> test that the PMU measured freq matches the freq exposed via the sysfs
> >> interface (min_req) at this "min point".
> >>
> >> I believe what I was saying when we last discussed this was that we can
> >> have two sets of tests:
> >>
> >> 1. Current tests with RPe enabled
> >> 2. Expose a sysfs from i915 to disable RPe and then use that to go to the
> >>     previous versions of the tests here
> >>
> >> So these patches are for case 1.
> >>
> >> Now about 2., considering that we are moving to the xe driver soon, I am
> >> wondering if there is much ROI in exposing the RPe disabling sysfs from
> >> i915. We might as well do something like that in xe? Or should this still
> >> be done in i915?
> >>
> >> In any case, there is interest in closing out these two bugs if possible:
> >>
> >> Bug: https://gitlab.freedesktop.org/drm/intel/-/issues/6806
> >> Bug: https://gitlab.freedesktop.org/drm/intel/-/issues/6786
> >>
> >> If we are not going to merge these patches (and assuming we won't change
> >> i915), how about just saying that due to change in the kernel ABI these
> >> tests are no longer valid and therefore blocklisting these tests and
> >> closing the bugs as 'will not fix'?
> >
> > How about we drop any notion of min/max from the test and just check that
> > the PMU sees what sysfs sees?

Yes if this is acceptable this would be great.

> > Once with idle, once with busy (frequency-idle, frequency-busy; via
> > TEST_BUSY/!TEST_BUSY). Would that work and be acceptable?

"frequency-idle" is already there, so I can try coming up with a
"frequency-busy" without a notion of min/max.

> To clarify, my angle here is that perf_pmu is testing PMU and not the sysfs
> frequency control.

Hmm, but if there is no kernel ABI they would have to be compared against
each other.

> In a sense any ABI breakage gets swept under the carpet
> which sucks but I see zero willingness to unbreak it. Certainly adding more
> sysfs knobs to work around it shouldn't be the way.

I was tending this way but won't if you think it's not fruitful. Will save
some work.

> So either remove the test, with a clear admittance of why, or blacklist it
> on GuC platforms in the same way.

So most thinking of:

* Skip the "frequency" PMU subtest on GuC platforms
* Add a "frequency-busy"

Thanks.
--
Ashutosh