Currently, SD_WAKE_AFFINE always takes priority over wakeup balancing if
SD_BALANCE_WAKE is set on the sched_domains. For asymmetric
configurations SD_WAKE_AFFINE is only desirable if the waking task's
compute demand (utilization) is suitable for the waking cpu and the
previous cpu, and all cpus within their respective
SD_SHARE_PKG_RESOURCES domains (sd_llc). If not, let wakeup balancing
take over (find_idlest_{group, cpu}()).This patch makes affine wake-ups conditional on whether both the waker cpu and prev_cpu has sufficient capacity for the waking task, or not, assuming that the cpu capacities within an SD_SHARE_PKG_RESOURCES domain (sd_llc) are homogeneous. cc: Ingo Molnar <[email protected]> cc: Peter Zijlstra <[email protected]> Acked-by: Vincent Guittot <[email protected]> Signed-off-by: Morten Rasmussen <[email protected]> --- kernel/sched/fair.c | 28 +++++++++++++++++++++++++++- 1 file changed, 27 insertions(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index c1c0aa8b300b..9e217eff3daf 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -114,6 +114,12 @@ unsigned int __read_mostly sysctl_sched_shares_window = 10000000UL; unsigned int sysctl_sched_cfs_bandwidth_slice = 5000UL; #endif +/* + * The margin used when comparing utilization with cpu capacity: + * util * 1024 < capacity * margin + */ +unsigned int capacity_margin = 1280; /* ~20% */ + static inline void update_load_add(struct load_weight *lw, unsigned long inc) { lw->weight += inc; @@ -5366,6 +5372,25 @@ static int cpu_util(int cpu) return (util >= capacity) ? capacity : util; } +static inline int task_util(struct task_struct *p) +{ + return p->se.avg.util_avg; +} + +static int wake_cap(struct task_struct *p, int cpu, int prev_cpu) +{ + long min_cap, max_cap; + + min_cap = min(capacity_orig_of(prev_cpu), capacity_orig_of(cpu)); + max_cap = cpu_rq(cpu)->rd->max_cpu_capacity; + + /* Minimum capacity is close to max, no need to abort wake_affine */ + if (max_cap - min_cap < max_cap >> 3) + return 0; + + return min_cap * 1024 < task_util(p) * capacity_margin; +} + /* * select_task_rq_fair: Select target runqueue for the waking task in domains * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE, @@ -5389,7 +5414,8 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f if (sd_flag & SD_BALANCE_WAKE) { record_wakee(p); - want_affine = !wake_wide(p) && cpumask_test_cpu(cpu, tsk_cpus_allowed(p)); + want_affine = !wake_wide(p) && !wake_cap(p, cpu, prev_cpu) + && cpumask_test_cpu(cpu, tsk_cpus_allowed(p)); } rcu_read_lock(); -- 1.9.1
