Messages in this thread | | | Subject | Re: [PATCH v2 0/4] sched/fair: Active balancer RT/DL preemption fix | From | Valentin Schneider <> | Date | Tue, 1 Oct 2019 11:29:43 +0100 |
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(expanded the Cc list) RT/DL folks, any thought on the thing?
On 15/08/2019 15:51, Valentin Schneider wrote: > Vincent's load balance rework [1] got me thinking about how and where we > use rq.nr_running vs rq.cfs.h_nr_running checks, and this lead me to > stare intently at the active load balancer. > > I haven't seen it happen (yet), but from reading the code it really looks > like we can have some scenarios where the cpu_stopper ends up preempting > a > CFS class task, since we never actually look at what's the remote rq's > running task. > > This series shuffles things around the CFS active load balancer to prevent > this from happening. > > - Patch 1 is a freebie cleanup > - Patch 2 is a preparatory code move > - Patch 3 adds h_nr_running checks > - Patch 4 adds a sched class check + detach_one_task() to the active balance > > This is based on top of today's tip/sched/core: > a46d14eca7b7 ("sched/fair: Use rq_lock/unlock in online_fair_sched_group") > > v1 -> v2: > - (new patch) Added need_active_balance() cleanup > > - Tweaked active balance code move to respect existing > sd->nr_balance_failed modifications > - Added explicit checks of active_load_balance()'s return value > > - Added an h_nr_running < 1 check before kicking the cpu_stopper > > - Added a detach_one_task() call in active_load_balance() when the remote > rq's running task is > CFS > > [1]: https://lore.kernel.org/lkml/1564670424-26023-1-git-send-email-vincent.guittot@linaro.org/ > > Valentin Schneider (4): > sched/fair: Make need_active_balance() return bools > sched/fair: Move active balance logic to its own function > sched/fair: Check for CFS tasks before detach_one_task() > sched/fair: Prevent active LB from preempting higher sched classes > > kernel/sched/fair.c | 151 ++++++++++++++++++++++++++++---------------- > 1 file changed, 95 insertions(+), 56 deletions(-) > > -- > 2.22.0 >
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