Hi! On 17/12/25 22:55, Andrea Righi wrote: > 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 included later to confirm that both DL servers are > functioning correctly: > > # ./runner -t rt_stall > ===== START ===== > TEST: rt_stall > DESCRIPTION: Verify that RT tasks cannot stall SCHED_EXT tasks > OUTPUT: > TAP version 13 > 1..1 > # Runtime of FAIR task (PID 1511) is 0.250000 seconds > # Runtime of RT task (PID 1512) is 4.750000 seconds > # FAIR task got 5.00% of total runtime > ok 1 PASS: FAIR task got more than 4.00% of runtime > TAP version 13 > 1..1 > # Runtime of EXT task (PID 1514) is 0.250000 seconds > # Runtime of RT task (PID 1515) is 4.750000 seconds > # EXT task got 5.00% of total runtime > ok 2 PASS: EXT task got more than 4.00% of runtime > TAP version 13 > 1..1 > # Runtime of FAIR task (PID 1517) is 0.250000 seconds > # Runtime of RT task (PID 1518) is 4.750000 seconds > # FAIR task got 5.00% of total runtime > ok 3 PASS: FAIR task got more than 4.00% of runtime > TAP version 13 > 1..1 > # Runtime of EXT task (PID 1521) is 0.250000 seconds > # Runtime of RT task (PID 1522) is 4.750000 seconds > # EXT task got 5.00% of total runtime > ok 4 PASS: EXT task got more than 4.00% of runtime > ok 1 rt_stall # > ===== END ===== > > v5: - do not restart the EXT server on switch_class() (Juri Lelli) > v4: - initialize EXT server bandwidth reservation at init time and > always keep it active (Andrea Righi) > - check for rq->nr_running == 1 to determine when to account idle > time (Juri Lelli) > v3: - clarify that fair is not the only dl_server (Juri Lelli) > - remove explicit stop to reduce timer reprogramming overhead > (Juri Lelli) > - do not restart pick_task() when it's invoked by the dl_server > (Tejun Heo) > - depend on CONFIG_SCHED_CLASS_EXT (Andrea Righi) > v2: - drop ->balance() now that pick_task() has an rf argument > (Andrea Righi) > > Tested-by: Christian Loehle <[email protected]> > Co-developed-by: Joel Fernandes <[email protected]> > Signed-off-by: Joel Fernandes <[email protected]> > Signed-off-by: Andrea Righi <[email protected]> > ---
This new version looks good to me, thanks! Reviewed-by: Juri Lelli <[email protected]> Best, Juri
