On Tue, Sep 22, 2020 at 12:04 PM Daniel Bristot de Oliveira <bris...@redhat.com> wrote: > > On 9/22/20 7:14 PM, Wei Wang wrote: > > On Mon, Sep 21, 2020 at 7:40 AM Daniel Bristot de Oliveira > > <bris...@redhat.com> wrote: > >> > >> The RT_RUNTIME_SHARE sched feature enables the sharing of rt_runtime > >> between CPUs, allowing a CPU to run a real-time task up to 100% of the > >> time while leaving more space for non-real-time tasks to run on the CPU > >> that lend rt_runtime. > >> > >> The problem is that a CPU can easily borrow enough rt_runtime to allow > >> a spinning rt-task to run forever, starving per-cpu tasks like kworkers, > >> which are non-real-time by design. > >> > >> This patch disables RT_RUNTIME_SHARE by default, avoiding this problem. > >> The feature will still be present for users that want to enable it, > >> though. > >> > >> Signed-off-by: Daniel Bristot de Oliveira <bris...@redhat.com> > >> Cc: Ingo Molnar <mi...@redhat.com> > >> Cc: Peter Zijlstra <pet...@infradead.org> > >> Cc: Juri Lelli <juri.le...@redhat.com> > >> Cc: Vincent Guittot <vincent.guit...@linaro.org> > >> Cc: Dietmar Eggemann <dietmar.eggem...@arm.com> > >> Cc: Steven Rostedt <rost...@goodmis.org> > >> Cc: Ben Segall <bseg...@google.com> > >> Cc: Mel Gorman <mgor...@suse.de> > >> Cc: Daniel Bristot de Oliveira <bris...@redhat.com> > >> Cc: Thomas Gleixner <t...@linutronix.de> > >> Cc: linux-kernel@vger.kernel.org > >> --- > >> kernel/sched/features.h | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >> diff --git a/kernel/sched/features.h b/kernel/sched/features.h > >> index 7481cd96f391..68d369cba9e4 100644 > >> --- a/kernel/sched/features.h > >> +++ b/kernel/sched/features.h > >> @@ -77,7 +77,7 @@ SCHED_FEAT(WARN_DOUBLE_CLOCK, false) > >> SCHED_FEAT(RT_PUSH_IPI, true) > >> #endif > >> > >> -SCHED_FEAT(RT_RUNTIME_SHARE, true) > >> +SCHED_FEAT(RT_RUNTIME_SHARE, false) > >> SCHED_FEAT(LB_MIN, false) > >> SCHED_FEAT(ATTACH_AGE_LOAD, true) > >> > >> -- > >> 2.26.2 > >> > > > > Tested on an Android device and can no longer see long running RT > > tasks (yes, Android have those for reasons). > > > > So: > > Tested-by: Wei Wang <w...@google.com> > > ?
Yup, thanks for pushing this. > > Thanks! > -- Daniel >
