| From foo@baz Sun Aug 26 09:13:00 CEST 2018 |
| From: Hailong Liu <liu.hailong6@zte.com.cn> |
| Date: Wed, 18 Jul 2018 08:46:55 +0800 |
| Subject: sched/rt: Restore rt_runtime after disabling RT_RUNTIME_SHARE |
| |
| From: Hailong Liu <liu.hailong6@zte.com.cn> |
| |
| [ Upstream commit f3d133ee0a17d5694c6f21873eec9863e11fa423 ] |
| |
| NO_RT_RUNTIME_SHARE feature is used to prevent a CPU borrow enough |
| runtime with a spin-rt-task. |
| |
| However, if RT_RUNTIME_SHARE feature is enabled and rt_rq has borrowd |
| enough rt_runtime at the beginning, rt_runtime can't be restored to |
| its initial bandwidth rt_runtime after we disable RT_RUNTIME_SHARE. |
| |
| E.g. on my PC with 4 cores, procedure to reproduce: |
| 1) Make sure RT_RUNTIME_SHARE is enabled |
| cat /sys/kernel/debug/sched_features |
| GENTLE_FAIR_SLEEPERS START_DEBIT NO_NEXT_BUDDY LAST_BUDDY |
| CACHE_HOT_BUDDY WAKEUP_PREEMPTION NO_HRTICK NO_DOUBLE_TICK |
| LB_BIAS NONTASK_CAPACITY TTWU_QUEUE NO_SIS_AVG_CPU SIS_PROP |
| NO_WARN_DOUBLE_CLOCK RT_PUSH_IPI RT_RUNTIME_SHARE NO_LB_MIN |
| ATTACH_AGE_LOAD WA_IDLE WA_WEIGHT WA_BIAS |
| 2) Start a spin-rt-task |
| ./loop_rr & |
| 3) set affinity to the last cpu |
| taskset -p 8 $pid_of_loop_rr |
| 4) Observe that last cpu have borrowed enough runtime. |
| cat /proc/sched_debug | grep rt_runtime |
| .rt_runtime : 950.000000 |
| .rt_runtime : 900.000000 |
| .rt_runtime : 950.000000 |
| .rt_runtime : 1000.000000 |
| 5) Disable RT_RUNTIME_SHARE |
| echo NO_RT_RUNTIME_SHARE > /sys/kernel/debug/sched_features |
| 6) Observe that rt_runtime can not been restored |
| cat /proc/sched_debug | grep rt_runtime |
| .rt_runtime : 950.000000 |
| .rt_runtime : 900.000000 |
| .rt_runtime : 950.000000 |
| .rt_runtime : 1000.000000 |
| |
| This patch help to restore rt_runtime after we disable |
| RT_RUNTIME_SHARE. |
| |
| Signed-off-by: Hailong Liu <liu.hailong6@zte.com.cn> |
| Signed-off-by: Jiang Biao <jiang.biao2@zte.com.cn> |
| Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> |
| Cc: Linus Torvalds <torvalds@linux-foundation.org> |
| Cc: Peter Zijlstra <peterz@infradead.org> |
| Cc: Thomas Gleixner <tglx@linutronix.de> |
| Cc: zhong.weidong@zte.com.cn |
| Link: http://lkml.kernel.org/r/1531874815-39357-1-git-send-email-liu.hailong6@zte.com.cn |
| Signed-off-by: Ingo Molnar <mingo@kernel.org> |
| Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| kernel/sched/rt.c | 2 ++ |
| 1 file changed, 2 insertions(+) |
| |
| --- a/kernel/sched/rt.c |
| +++ b/kernel/sched/rt.c |
| @@ -837,6 +837,8 @@ static int do_sched_rt_period_timer(stru |
| * can be time-consuming. Try to avoid it when possible. |
| */ |
| raw_spin_lock(&rt_rq->rt_runtime_lock); |
| + if (!sched_feat(RT_RUNTIME_SHARE) && rt_rq->rt_runtime != RUNTIME_INF) |
| + rt_rq->rt_runtime = rt_b->rt_runtime; |
| skip = !rt_rq->rt_time && !rt_rq->rt_nr_running; |
| raw_spin_unlock(&rt_rq->rt_runtime_lock); |
| if (skip) |