[igt-dev] [PATCH i-g-t] tests/perf: add a test for OA data polling reads using "small" buffers

[Dixit, Ashutosh]

On Fri, 27 Mar 2020 12:49:22 -0700, Dixit, Ashutosh wrote:
>
> On Fri, 27 Mar 2020 12:06:13 -0700, Lionel Landwerlin wrote:
> >
> > On 27/03/2020 21:03, Dixit, Ashutosh wrote:
> > > On Fri, 27 Mar 2020 09:09:41 -0700, Lionel Landwerlin wrote:
> > >> On 27/03/2020 06:50, Dixit, Ashutosh wrote:
> > >>> On Thu, 26 Mar 2020 21:42:50 -0700, Ashutosh Dixit wrote:
> > >>>> diff --git a/tests/perf.c b/tests/perf.c
> > >>>> index 724f6f809..3dc757c3b 100644
> > >>>> --- a/tests/perf.c
> > >>>> +++ b/tests/perf.c
> > >>>> +static void test_polling_small_buf(void)
> > >>>> +{
> > >>> /snip/
> > >>>
> > >>>> +
> > >>>> +	igt_assert(abs(n_expect_read_bytes - n_bytes_read) < (0.10 * n_expect_read_bytes));
> > >>>> +}
> > >>>> +
> > >>> I'd be wary of a 90% match on slow platforms like Atom? Maybe 80% is safer?
> > >>
> > >> Do we have any experiment showing them behaving differently?
> > > No I don't have any data, but considering that in previous stable versions
> > > we can only read < 10% of the data, I think it should be ok to go down to
> > > 80%? So that we don't start getting unnecessary false alarms in CI, even
> > > when the issue is fixed.
> >
> > Okay, for the record I get somewhere between 93~95% of expected reports on
> > KBLGT2.
>
> Yes I tried it and saw that. I already gave a R-b so we could probably
> merge the patch after making that change (0.2 instead of 0.1 above), or do
> you want me to post a new version with the change? Thanks!

Actually there has been some change in the kernel, earlier like you I was
also getting around 94% with a 1 KB buffer, now I am getting about
87%. I am getting 94% with a 1 MB buffer. Does the amount of expected data
in the test need to be modified? I can try to bisect tomorrow and see what
has done this, unless you already know. Thanks!