linux-kernel - Re: [PATCH 13/14] selftests/sched_ext: Add test for sched_ext dl

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Message-ID: <aPY_YHK-oWZp0KK1@gpd4>
Date: Mon, 20 Oct 2025 15:55:44 +0200
From: Andrea Righi <arighi@...dia.com>
To: Christian Loehle <christian.loehle@....com>
Cc: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>,
	Joel Fernandes <joelagnelf@...dia.com>, Tejun Heo <tj@...nel.org>,
	David Vernet <void@...ifault.com>,
	Changwoo Min <changwoo@...lia.com>, Shuah Khan <shuah@...nel.org>,
	sched-ext@...ts.linux.dev, bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 13/14] selftests/sched_ext: Add test for sched_ext
 dl_server

Hi Christian,

On Mon, Oct 20, 2025 at 02:26:17PM +0100, Christian Loehle wrote:
> On 10/17/25 10:26, Andrea Righi wrote:
> > Add a selftest to validate the correct behavior of the deadline server
> > for the ext_sched_class.
> > 
> > [ Joel: Replaced occurences of CFS in the test with EXT. ]
> > 
> > Co-developed-by: Joel Fernandes <joelagnelf@...dia.com>
> > Signed-off-by: Joel Fernandes <joelagnelf@...dia.com>
> > Signed-off-by: Andrea Righi <arighi@...dia.com>
> > ---
> >  tools/testing/selftests/sched_ext/Makefile    |   1 +
> >  .../selftests/sched_ext/rt_stall.bpf.c        |  23 ++
> >  tools/testing/selftests/sched_ext/rt_stall.c  | 214 ++++++++++++++++++
> >  3 files changed, 238 insertions(+)
> >  create mode 100644 tools/testing/selftests/sched_ext/rt_stall.bpf.c
> >  create mode 100644 tools/testing/selftests/sched_ext/rt_stall.c
> 
> 
> Does this pass consistently for you?
> For a loop of 1000 runs I'm getting total runtime numbers for the EXT task of:
> 
>    0.000 -    0.261 |  (7)
>    0.261 -    0.522 | ###### (86)
>    0.522 -    4.437 |  (0)
>    4.437 -    4.698 |  (1)
>    4.698 -    4.959 | ################### (257)
>    4.959 -    5.220 | ################################################## (649)
> 
> I'll try to see what's going wrong here...

Is that 1000 runs of total_bw? Yeah, the small ones don't look right at
all, unless they're caused by some errors in the measurement (or something
wrong in the test itself). Still better than without the dl_server, but
it'd be nice to understand what's going on. :)

I'll try to reproduce that on my side as well.

Thanks,
-Andrea