When cpu is marked as non preferred, any load pulled towards it is pointless since in the next tick task will be pushed out again. So, Consider only preferred CPUs for load balance.
This makes it not fight against the push task mechanism which happens at tick. Also, this stops active balance to happen on non-preferred CPU pulling the load. This means there is no load balancing if the task is pinned only to non-preferred CPUs. They will continue to run where they were previously running before the CPUs was marked as non-preferred. Bailout early for NEWIDLE and IDLE balance as load balancing is done only on preferred CPUs. Signed-off-by: Shrikanth Hegde <[email protected]> --- kernel/sched/fair.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index df8c9c2c7918..12f5b7de28d2 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -13399,7 +13399,7 @@ static int sched_balance_rq(int this_cpu, struct rq *this_rq, }; bool need_unlock = false; - cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask); + cpumask_and(cpus, sched_domain_span(sd), cpu_preferred_mask); schedstat_inc(sd->lb_count[idle]); @@ -14337,7 +14337,8 @@ static void _nohz_idle_balance(struct rq *this_rq, unsigned int flags) update_rq_clock(rq); rq_unlock_irqrestore(rq, &rf); - if (flags & NOHZ_BALANCE_KICK) + if (flags & NOHZ_BALANCE_KICK && + cpu_preferred(balance_cpu)) sched_balance_domains(rq, CPU_IDLE); } @@ -14481,10 +14482,8 @@ static int sched_balance_newidle(struct rq *this_rq, struct rq_flags *rf) */ this_rq->idle_stamp = rq_clock(this_rq); - /* - * Do not pull tasks towards !active CPUs... - */ - if (!cpu_active(this_cpu)) + /* Do not pull tasks towards !preferred CPUs */ + if (!cpu_preferred(this_cpu)) return 0; /* -- 2.47.3
