From a4064fb614f83c0a097c5ff7fe433c4aa139c7af Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 21 Dec 2017 10:42:50 +0100 Subject: [PATCH] sched/fair: Add NOHZ stats balancing Teach the idle balancer about the need to update statistics which have a different periodicity from regular balancing. Suggested-by: Vincent Guittot Signed-off-by: Peter Zijlstra (Intel) Cc: Frederic Weisbecker Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar --- kernel/sched/fair.c | 31 +++++++++++++++++++------------ 1 file changed, 19 insertions(+), 12 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index fa483d889f07..d8693fa9e7c5 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -9053,6 +9053,7 @@ static struct { cpumask_var_t idle_cpus_mask; atomic_t nr_cpus; unsigned long next_balance; /* in jiffy units */ + unsigned long next_stats; } nohz ____cacheline_aligned; static inline int find_new_ilb(void) @@ -9087,9 +9088,8 @@ unlock: * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle * CPU (if there is one). */ -static void kick_ilb(void) +static void kick_ilb(unsigned int flags) { - unsigned int flags; int ilb_cpu; nohz.next_balance++; @@ -9099,7 +9099,7 @@ static void kick_ilb(void) if (ilb_cpu >= nr_cpu_ids) return; - flags = atomic_fetch_or(NOHZ_KICK_MASK, nohz_flags(ilb_cpu)); + flags = atomic_fetch_or(flags, nohz_flags(ilb_cpu)); if (flags & NOHZ_KICK_MASK) return; @@ -9129,7 +9129,7 @@ static void nohz_balancer_kick(struct rq *rq) struct sched_domain_shared *sds; struct sched_domain *sd; int nr_busy, i, cpu = rq->cpu; - bool kick = false; + unsigned int flags = 0; if (unlikely(rq->idle_balance)) return; @@ -9148,11 +9148,14 @@ static void nohz_balancer_kick(struct rq *rq) if (likely(!atomic_read(&nohz.nr_cpus))) return; + if (time_after(now, nohz.next_stats)) + flags = NOHZ_STATS_KICK; + if (time_before(now, nohz.next_balance)) - return; + goto out; if (rq->nr_running >= 2) { - kick = true; + flags = NOHZ_KICK_MASK; goto out; } @@ -9165,7 +9168,7 @@ static void nohz_balancer_kick(struct rq *rq) */ nr_busy = atomic_read(&sds->nr_busy_cpus); if (nr_busy > 1) { - kick = true; + flags = NOHZ_KICK_MASK; goto unlock; } @@ -9175,7 +9178,7 @@ static void nohz_balancer_kick(struct rq *rq) if (sd) { if ((rq->cfs.h_nr_running >= 1) && check_cpu_capacity(rq, sd)) { - kick = true; + flags = NOHZ_KICK_MASK; goto unlock; } } @@ -9188,7 +9191,7 @@ static void nohz_balancer_kick(struct rq *rq) continue; if (sched_asym_prefer(i, cpu)) { - kick = true; + flags = NOHZ_KICK_MASK; goto unlock; } } @@ -9196,8 +9199,8 @@ static void nohz_balancer_kick(struct rq *rq) unlock: rcu_read_unlock(); out: - if (kick) - kick_ilb(); + if (flags) + kick_ilb(flags); } void nohz_balance_exit_idle(unsigned int cpu) @@ -9389,7 +9392,9 @@ out: static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { /* Earliest time when we have to do rebalance again */ - unsigned long next_balance = jiffies + 60*HZ; + unsigned long now = jiffies; + unsigned long next_balance = now + 60*HZ; + unsigned long next_stats = now + msecs_to_jiffies(LOAD_AVG_PERIOD); int update_next_balance = 0; int this_cpu = this_rq->cpu; unsigned int flags; @@ -9449,6 +9454,8 @@ static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) if (flags & NOHZ_BALANCE_KICK) rebalance_domains(this_rq, CPU_IDLE); + nohz.next_stats = next_stats; + /* * next_balance will be updated only when there is a need. * When the CPU is attached to null domain for ex, it will not be