The scheduler already favours moving tasks towards its preferred node but does nothing special if the destination node is anything else. This patch favours moving tasks towards a destination node if more NUMA hinting faults were recorded on it. Similarly if migrating to a destination node would degrade locality based on NUMA hinting faults then it will be resisted.
Signed-off-by: Peter Zijlstra <pet...@infradead.org> Signed-off-by: Mel Gorman <mgor...@suse.de> --- kernel/sched/fair.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 48 insertions(+), 6 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index e8d9b3e..e451859 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3967,22 +3967,54 @@ task_hot(struct task_struct *p, u64 now, struct sched_domain *sd) } #ifdef CONFIG_NUMA_BALANCING + +static bool migrate_locality_prepare(struct task_struct *p, struct lb_env *env, + int *src_nid, int *dst_nid) +{ + if (!p->numa_faults || !(env->sd->flags & SD_NUMA)) + return false; + + *src_nid = cpu_to_node(env->src_cpu); + *dst_nid = cpu_to_node(env->dst_cpu); + + if (*src_nid == *dst_nid || + p->numa_migrate_seq >= sysctl_numa_balancing_settle_count) + return false; + + return true; +} + /* Returns true if the destination node has incurred more faults */ static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env) { int src_nid, dst_nid; - if (!p->numa_faults || !(env->sd->flags & SD_NUMA)) + if (!migrate_locality_prepare(p, env, &src_nid, &dst_nid)) return false; - src_nid = cpu_to_node(env->src_cpu); - dst_nid = cpu_to_node(env->dst_cpu); + /* Move towards node if it is the preferred node */ + if (p->numa_preferred_nid == dst_nid) + return true; - if (src_nid == dst_nid || - p->numa_migrate_seq >= sysctl_numa_balancing_settle_count) + /* + * Move towards node if there were a higher number of private + * NUMA hinting faults recorded on it + */ + if (p->numa_faults[task_faults_idx(dst_nid, 1)] > + p->numa_faults[task_faults_idx(src_nid, 1)]) + return true; + + return false; +} + +static bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env) +{ + int src_nid, dst_nid; + + if (!migrate_locality_prepare(p, env, &src_nid, &dst_nid)) return false; - if (p->numa_preferred_nid == dst_nid) + if (p->numa_faults[src_nid] > p->numa_faults[dst_nid]) return true; return false; @@ -3993,6 +4025,14 @@ static inline bool migrate_improves_locality(struct task_struct *p, { return false; } + + +static inline bool migrate_degrades_locality(struct task_struct *p, + struct lb_env *env) +{ + return false; +} + #endif /* @@ -4048,6 +4088,8 @@ int can_migrate_task(struct task_struct *p, struct lb_env *env) * 3) too many balance attempts have failed. */ tsk_cache_hot = task_hot(p, env->src_rq->clock_task, env->sd); + if (!tsk_cache_hot) + tsk_cache_hot = migrate_degrades_locality(p, env); if (migrate_improves_locality(p, env)) { #ifdef CONFIG_SCHEDSTATS -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/