Re: [igt-dev] [PATCH i-g-t v3] tests/kms_concurrent: Move bandwidth calculation to igt_fixture

["Kahola, Mika" <mika.kahola@intel.com>]

> -----Original Message-----
> From: igt-dev <igt-dev-bounces@lists.freedesktop.org> On Behalf Of Kahola,
> Mika
> Sent: Tuesday, March 31, 2020 11:22 AM
> To: Latvala, Petri <petri.latvala@intel.com>
> Cc: igt-dev@lists.freedesktop.org
> Subject: Re: [igt-dev] [PATCH i-g-t v3] tests/kms_concurrent: Move bandwidth
> calculation to igt_fixture
> 
> 
> 
> -----Original Message-----
> From: Latvala, Petri <petri.latvala@intel.com>
> Sent: Tuesday, March 31, 2020 9:45 AM
> To: Kahola, Mika <mika.kahola@intel.com>
> Cc: igt-dev@lists.freedesktop.org; juhapekka.heikkila@gmail.com; Lisovskiy,
> Stanislav <stanislav.lisovskiy@intel.com>
> Subject: Re: [PATCH i-g-t v3] tests/kms_concurrent: Move bandwidth calculation
> to igt_fixture
> 
> On Mon, Mar 30, 2020 at 02:02:29PM +0300, Mika Kahola wrote:
> > The commit 153b34b5353df8c18a87d ("tests/kms_concurrent:
> > Test maximum number of planes supported by the platform") caused
> > regression on HSW pipe B testing such as.
> >
> > IGT-Version: 1.25-gfd8248084 (x86_64) (Linux:
> > 5.6.0-rc7-CI-CI_DRM_8194+ x86_64) Starting subtest: pipe-B Testing
> > resolution with connector VGA-1 using pipe B with seed 1585245074
> > child 0 died with signal 11, Segmentation fault Subtest pipe-B: FAIL
> > (0.330s)
> >
> > To fix this, we need move bandwidth calculation routines into part of
> > igt_fixture instead of calculating it just before actual testing. The
> > patch takes the minimum of those maximum number of planes for given
> output.
> >
> > v2: Limit bandwidth check only gen11+ (CI)
> > v3: Loop child process 5x longer when running test with 1 iteration
> > (CI)
> >
> > Signed-off-by: Mika Kahola <mika.kahola@intel.com>
> > ---
> >  tests/kms_concurrent.c | 30 ++++++++++++++++--------------
> >  1 file changed, 16 insertions(+), 14 deletions(-)
> >
> > diff --git a/tests/kms_concurrent.c b/tests/kms_concurrent.c index
> > 1403e990..31c5620a 100644
> > --- a/tests/kms_concurrent.c
> > +++ b/tests/kms_concurrent.c
> > @@ -36,6 +36,7 @@ typedef struct {
> >  	igt_display_t display;
> >  	igt_plane_t **plane;
> >  	struct igt_fb *fb;
> > +	int max_planes;
> >  } data_t;
> >
> >  /* Command line parameters. */
> > @@ -223,13 +224,13 @@ test_plane_position_with_output(data_t *data,
> enum pipe pipe, int max_planes,
> >  				igt_output_t *output)
> >  {
> >  	int i;
> > -	int iterations = opt.iterations < 1 ? 1 : opt.iterations;
> > +	int iterations = opt.iterations < 5 ? 1 : opt.iterations;
> 
> This changes nothing though for CI. You still use 1. In fact this just limits the
> iterations to 1 for everyone who specifies more than 1, until they use 5 or more.
> 
> And still, this patch needs an actual explanation why the crash happened and
> why doing the same calculation in a fixture help. Otherwise there's no guarantee
> it won't happen again. Until proven otherwise, avoiding the crash is accidental.
> 
> I investigated this a bit further and I noticed that for yet unidentified reason the
> bandwidth calculation returned different number of planes for pipe B. This was
> too much to handle on actual test and therefore child exited too early.
> 
> There seems to be a simpler way of computing how many planes we can support
> with the given bandwidth. I propose that we disregard this patch and I will
> propose and test another kind of solution.

What would be to best approach here? Should I first revert the original patch i.e.

commit 2b65609b1de3 ("tests/kms_concurrent: Test maximum number of planes supported by the platform")

and then provide a new patch that has similar functionality but the approach is different or should I just a provide a fix that removes bandwidth calculations and replaces that with a different approach?

-Mika-
> 
> -Mika-
> --
> Petri Latvala
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