Re: [PATCH 06/14] sched_ext: Add a DL server for sched_ext tasks

[Andrea Righi <arighi@nvidia.com>]

On Fri, Oct 17, 2025 at 05:40:12AM -1000, Tejun Heo wrote:
> On Fri, Oct 17, 2025 at 11:25:53AM +0200, Andrea Righi wrote:
> > From: Joel Fernandes <joelagnelf@nvidia.com>
> > 
> > sched_ext currently suffers starvation due to RT. The same workload when
> > converted to EXT can get zero runtime if RT is 100% running, causing EXT
> > processes to stall. Fix it by adding a DL server for EXT.
> > 
> > A kselftest is also provided later to verify:
> > 
> > ./runner -t rt_stall
> > ===== START =====
> > TEST: rt_stall
> > DESCRIPTION: Verify that RT tasks cannot stall SCHED_EXT tasks
> > OUTPUT:
> > TAP version 13
> > 1..1
> > ok 1 PASS: CFS task got more than 4.00% of runtime
> > 
> > [ arighi: drop ->balance() now that pick_task() has an rf argument ]
> > 
> > Cc: Luigi De Matteis <ldematteis123@gmail.com>
> > Co-developed-by: Andrea Righi <arighi@nvidia.com>
> > Signed-off-by: Andrea Righi <arighi@nvidia.com>
> > Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
> 
> I don't see anything preventing this to come after patch 11 so that all
> sched_ext changes are at the end. Am I correct? That'd make applying the
> patches easier. All the debug and deadline changes can be applied to
> sched/core and I can pull that and apply sched_ext changes on top.

Oh yes, we can definitely move this one. I'll reorder the patches.

Thanks,
-Andrea