diff options
Diffstat (limited to 'kernel/sched/fair.c')
| -rw-r--r-- | kernel/sched/fair.c | 39 |
1 files changed, 32 insertions, 7 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 46d64e4ccfde..0fe30e66aff1 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3181,17 +3181,25 @@ static inline void check_schedstat_required(void) static void enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) { + bool renorm = !(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING); + bool curr = cfs_rq->curr == se; + /* - * Update the normalized vruntime before updating min_vruntime - * through calling update_curr(). + * If we're the current task, we must renormalise before calling + * update_curr(). */ - if (!(flags & ENQUEUE_WAKEUP) || (flags & ENQUEUE_WAKING)) + if (renorm && curr) se->vruntime += cfs_rq->min_vruntime; + update_curr(cfs_rq); + /* - * Update run-time statistics of the 'current'. + * Otherwise, renormalise after, such that we're placed at the current + * moment in time, instead of some random moment in the past. */ - update_curr(cfs_rq); + if (renorm && !curr) + se->vruntime += cfs_rq->min_vruntime; + enqueue_entity_load_avg(cfs_rq, se); account_entity_enqueue(cfs_rq, se); update_cfs_shares(cfs_rq); @@ -3207,7 +3215,7 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) update_stats_enqueue(cfs_rq, se); check_spread(cfs_rq, se); } - if (se != cfs_rq->curr) + if (!curr) __enqueue_entity(cfs_rq, se); se->on_rq = 1; @@ -5071,7 +5079,19 @@ static int select_idle_sibling(struct task_struct *p, int target) return i; /* - * Otherwise, iterate the domains and find an elegible idle cpu. + * Otherwise, iterate the domains and find an eligible idle cpu. + * + * A completely idle sched group at higher domains is more + * desirable than an idle group at a lower level, because lower + * domains have smaller groups and usually share hardware + * resources which causes tasks to contend on them, e.g. x86 + * hyperthread siblings in the lowest domain (SMT) can contend + * on the shared cpu pipeline. + * + * However, while we prefer idle groups at higher domains + * finding an idle cpu at the lowest domain is still better than + * returning 'target', which we've already established, isn't + * idle. */ sd = rcu_dereference(per_cpu(sd_llc, target)); for_each_lower_domain(sd) { @@ -5081,11 +5101,16 @@ static int select_idle_sibling(struct task_struct *p, int target) tsk_cpus_allowed(p))) goto next; + /* Ensure the entire group is idle */ for_each_cpu(i, sched_group_cpus(sg)) { if (i == target || !idle_cpu(i)) goto next; } + /* + * It doesn't matter which cpu we pick, the + * whole group is idle. + */ target = cpumask_first_and(sched_group_cpus(sg), tsk_cpus_allowed(p)); goto done; |