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: Latvala, Petri <petri.latvala@intel.com>
> Sent: Tuesday, March 31, 2020 2:05 PM
> To: Kahola, Mika <mika.kahola@intel.com>
> Cc: igt-dev@lists.freedesktop.org
> Subject: Re: [PATCH i-g-t v3] tests/kms_concurrent: Move bandwidth calculation
> to igt_fixture
> 
> On Tue, Mar 31, 2020 at 01:12:31PM +0300, Kahola, Mika wrote:
> > > -----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?
> 
> 
> Yeah if you want to revert and try a different approach, fine by me.
> 
Ok, I'll just revert the one and send a patch with different approach. Let's see what CI thinks this time.

> 
> --
> Petri Latvala
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