652 lines
20 KiB
Diff
652 lines
20 KiB
Diff
From: Venkatesh Pallipadi <venki@google.com>
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Date: Sat, 22 May 2010 00:09:41 +0000 (-0700)
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Subject: sched: Change nohz idle load balancing logic to push model
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X-Git-Tag: v2.6.36-rc1~531^2~21
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X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git;a=commitdiff_plain;h=83cd4fe27ad8446619b2e030b171b858501de87d
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sched: Change nohz idle load balancing logic to push model
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In the new push model, all idle CPUs indeed go into nohz mode. There is
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still the concept of idle load balancer (performing the load balancing
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on behalf of all the idle cpu's in the system). Busy CPU kicks the nohz
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balancer when any of the nohz CPUs need idle load balancing.
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The kickee CPU does the idle load balancing on behalf of all idle CPUs
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instead of the normal idle balance.
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This addresses the below two problems with the current nohz ilb logic:
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* the idle load balancer continued to have periodic ticks during idle and
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wokeup frequently, even though it did not have any rebalancing to do on
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behalf of any of the idle CPUs.
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* On x86 and CPUs that have APIC timer stoppage on idle CPUs, this
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periodic wakeup can result in a periodic additional interrupt on a CPU
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doing the timer broadcast.
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Also currently we are migrating the unpinned timers from an idle to the cpu
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doing idle load balancing (when all the cpus in the system are idle,
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there is no idle load balancing cpu and timers get added to the same idle cpu
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where the request was made. So the existing optimization works only on semi idle
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system).
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And In semi idle system, we no longer have periodic ticks on the idle load
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balancer CPU. Using that cpu will add more delays to the timers than intended
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(as that cpu's timer base may not be uptodate wrt jiffies etc). This was
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causing mysterious slowdowns during boot etc.
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For now, in the semi idle case, use the nearest busy cpu for migrating timers
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from an idle cpu. This is good for power-savings anyway.
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Signed-off-by: Venkatesh Pallipadi <venki@google.com>
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Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
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Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
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Cc: Thomas Gleixner <tglx@linutronix.de>
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LKML-Reference: <1274486981.2840.46.camel@sbs-t61.sc.intel.com>
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Signed-off-by: Ingo Molnar <mingo@elte.hu>
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---
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[ backported for 2.6.35 ]
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diff --git a/include/linux/sched.h b/include/linux/sched.h
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index c2d4316..a3e5b1c 100644
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--- a/include/linux/sched.h
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+++ b/include/linux/sched.h
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@@ -271,13 +271,10 @@ extern int runqueue_is_locked(int cpu);
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extern cpumask_var_t nohz_cpu_mask;
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#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ)
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-extern int select_nohz_load_balancer(int cpu);
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-extern int get_nohz_load_balancer(void);
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+extern void select_nohz_load_balancer(int stop_tick);
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+extern int get_nohz_timer_target(void);
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#else
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-static inline int select_nohz_load_balancer(int cpu)
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-{
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- return 0;
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-}
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+static inline void select_nohz_load_balancer(int stop_tick) { }
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#endif
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/*
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diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
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index 5c69e99..e934339 100644
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--- a/kernel/hrtimer.c
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+++ b/kernel/hrtimer.c
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@@ -144,12 +144,8 @@ struct hrtimer_clock_base *lock_hrtimer_base(const struct hrtimer *timer,
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static int hrtimer_get_target(int this_cpu, int pinned)
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{
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#ifdef CONFIG_NO_HZ
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- if (!pinned && get_sysctl_timer_migration() && idle_cpu(this_cpu)) {
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- int preferred_cpu = get_nohz_load_balancer();
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-
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- if (preferred_cpu >= 0)
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- return preferred_cpu;
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- }
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+ if (!pinned && get_sysctl_timer_migration() && idle_cpu(this_cpu))
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+ return get_nohz_timer_target();
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#endif
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return this_cpu;
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}
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diff --git a/kernel/sched.c b/kernel/sched.c
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index a757f6b..132950b 100644
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--- a/kernel/sched.c
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+++ b/kernel/sched.c
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@@ -460,7 +460,7 @@ struct rq {
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unsigned long last_load_update_tick;
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#ifdef CONFIG_NO_HZ
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u64 nohz_stamp;
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- unsigned char in_nohz_recently;
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+ unsigned char nohz_balance_kick;
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#endif
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unsigned int skip_clock_update;
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@@ -1195,6 +1195,27 @@ static void resched_cpu(int cpu)
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#ifdef CONFIG_NO_HZ
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/*
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+ * In the semi idle case, use the nearest busy cpu for migrating timers
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+ * from an idle cpu. This is good for power-savings.
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+ *
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+ * We don't do similar optimization for completely idle system, as
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+ * selecting an idle cpu will add more delays to the timers than intended
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+ * (as that cpu's timer base may not be uptodate wrt jiffies etc).
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+ */
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+int get_nohz_timer_target(void)
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+{
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+ int cpu = smp_processor_id();
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+ int i;
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+ struct sched_domain *sd;
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+
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+ for_each_domain(cpu, sd) {
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+ for_each_cpu(i, sched_domain_span(sd))
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+ if (!idle_cpu(i))
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+ return i;
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+ }
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+ return cpu;
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+}
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+/*
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* When add_timer_on() enqueues a timer into the timer wheel of an
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* idle CPU then this timer might expire before the next timer event
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* which is scheduled to wake up that CPU. In case of a completely
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@@ -7791,6 +7812,10 @@ void __init sched_init(void)
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rq->idle_stamp = 0;
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rq->avg_idle = 2*sysctl_sched_migration_cost;
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rq_attach_root(rq, &def_root_domain);
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+#ifdef CONFIG_NO_HZ
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+ rq->nohz_balance_kick = 0;
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+ init_sched_softirq_csd(&per_cpu(remote_sched_softirq_cb, i));
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+#endif
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#endif
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init_rq_hrtick(rq);
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atomic_set(&rq->nr_iowait, 0);
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@@ -7835,8 +7860,11 @@ void __init sched_init(void)
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zalloc_cpumask_var(&nohz_cpu_mask, GFP_NOWAIT);
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#ifdef CONFIG_SMP
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#ifdef CONFIG_NO_HZ
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- zalloc_cpumask_var(&nohz.cpu_mask, GFP_NOWAIT);
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- alloc_cpumask_var(&nohz.ilb_grp_nohz_mask, GFP_NOWAIT);
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+ zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
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+ alloc_cpumask_var(&nohz.grp_idle_mask, GFP_NOWAIT);
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+ atomic_set(&nohz.load_balancer, nr_cpu_ids);
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+ atomic_set(&nohz.first_pick_cpu, nr_cpu_ids);
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+ atomic_set(&nohz.second_pick_cpu, nr_cpu_ids);
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#endif
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/* May be allocated at isolcpus cmdline parse time */
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if (cpu_isolated_map == NULL)
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diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
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index 22b8b4f..6ee2e0a 100644
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--- a/kernel/sched_fair.c
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+++ b/kernel/sched_fair.c
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@@ -3091,13 +3091,40 @@ out_unlock:
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}
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#ifdef CONFIG_NO_HZ
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+
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+static DEFINE_PER_CPU(struct call_single_data, remote_sched_softirq_cb);
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+
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+static void trigger_sched_softirq(void *data)
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+{
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+ raise_softirq_irqoff(SCHED_SOFTIRQ);
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+}
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+
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+static inline void init_sched_softirq_csd(struct call_single_data *csd)
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+{
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+ csd->func = trigger_sched_softirq;
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+ csd->info = NULL;
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+ csd->flags = 0;
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+ csd->priv = 0;
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+}
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+
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+/*
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+ * idle load balancing details
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+ * - One of the idle CPUs nominates itself as idle load_balancer, while
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+ * entering idle.
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+ * - This idle load balancer CPU will also go into tickless mode when
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+ * it is idle, just like all other idle CPUs
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+ * - When one of the busy CPUs notice that there may be an idle rebalancing
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+ * needed, they will kick the idle load balancer, which then does idle
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+ * load balancing for all the idle CPUs.
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+ */
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static struct {
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atomic_t load_balancer;
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- cpumask_var_t cpu_mask;
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- cpumask_var_t ilb_grp_nohz_mask;
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-} nohz ____cacheline_aligned = {
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- .load_balancer = ATOMIC_INIT(-1),
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-};
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+ atomic_t first_pick_cpu;
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+ atomic_t second_pick_cpu;
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+ cpumask_var_t idle_cpus_mask;
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+ cpumask_var_t grp_idle_mask;
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+ unsigned long next_balance; /* in jiffy units */
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+} nohz ____cacheline_aligned;
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int get_nohz_load_balancer(void)
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{
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@@ -3151,17 +3178,17 @@ static inline struct sched_domain *lowest_flag_domain(int cpu, int flag)
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*/
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static inline int is_semi_idle_group(struct sched_group *ilb_group)
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{
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- cpumask_and(nohz.ilb_grp_nohz_mask, nohz.cpu_mask,
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+ cpumask_and(nohz.grp_idle_mask, nohz.idle_cpus_mask,
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sched_group_cpus(ilb_group));
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/*
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* A sched_group is semi-idle when it has atleast one busy cpu
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* and atleast one idle cpu.
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*/
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- if (cpumask_empty(nohz.ilb_grp_nohz_mask))
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+ if (cpumask_empty(nohz.grp_idle_mask))
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return 0;
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- if (cpumask_equal(nohz.ilb_grp_nohz_mask, sched_group_cpus(ilb_group)))
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+ if (cpumask_equal(nohz.grp_idle_mask, sched_group_cpus(ilb_group)))
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return 0;
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return 1;
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@@ -3194,7 +3221,7 @@ static int find_new_ilb(int cpu)
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* Optimize for the case when we have no idle CPUs or only one
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* idle CPU. Don't walk the sched_domain hierarchy in such cases
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*/
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- if (cpumask_weight(nohz.cpu_mask) < 2)
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+ if (cpumask_weight(nohz.idle_cpus_mask) < 2)
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goto out_done;
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for_each_flag_domain(cpu, sd, SD_POWERSAVINGS_BALANCE) {
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@@ -3202,7 +3229,7 @@ static int find_new_ilb(int cpu)
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do {
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if (is_semi_idle_group(ilb_group))
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- return cpumask_first(nohz.ilb_grp_nohz_mask);
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+ return cpumask_first(nohz.grp_idle_mask);
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ilb_group = ilb_group->next;
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@@ -3210,98 +3237,116 @@ static int find_new_ilb(int cpu)
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}
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out_done:
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- return cpumask_first(nohz.cpu_mask);
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+ return nr_cpu_ids;
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}
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#else /* (CONFIG_SCHED_MC || CONFIG_SCHED_SMT) */
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static inline int find_new_ilb(int call_cpu)
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{
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- return cpumask_first(nohz.cpu_mask);
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+ return nr_cpu_ids;
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}
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#endif
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/*
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+ * Kick a CPU to do the nohz balancing, if it is time for it. We pick the
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+ * nohz_load_balancer CPU (if there is one) otherwise fallback to any idle
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+ * CPU (if there is one).
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+ */
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+static void nohz_balancer_kick(int cpu)
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+{
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+ int ilb_cpu;
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+
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+ nohz.next_balance++;
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+
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+ ilb_cpu = get_nohz_load_balancer();
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+
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+ if (ilb_cpu >= nr_cpu_ids) {
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+ ilb_cpu = cpumask_first(nohz.idle_cpus_mask);
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+ if (ilb_cpu >= nr_cpu_ids)
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+ return;
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+ }
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+
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+ if (!cpu_rq(ilb_cpu)->nohz_balance_kick) {
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+ struct call_single_data *cp;
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+
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+ cpu_rq(ilb_cpu)->nohz_balance_kick = 1;
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+ cp = &per_cpu(remote_sched_softirq_cb, cpu);
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+ __smp_call_function_single(ilb_cpu, cp, 0);
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+ }
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+ return;
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+}
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+
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+/*
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* This routine will try to nominate the ilb (idle load balancing)
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* owner among the cpus whose ticks are stopped. ilb owner will do the idle
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- * load balancing on behalf of all those cpus. If all the cpus in the system
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- * go into this tickless mode, then there will be no ilb owner (as there is
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- * no need for one) and all the cpus will sleep till the next wakeup event
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- * arrives...
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- *
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- * For the ilb owner, tick is not stopped. And this tick will be used
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- * for idle load balancing. ilb owner will still be part of
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- * nohz.cpu_mask..
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+ * load balancing on behalf of all those cpus.
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*
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- * While stopping the tick, this cpu will become the ilb owner if there
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- * is no other owner. And will be the owner till that cpu becomes busy
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- * or if all cpus in the system stop their ticks at which point
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- * there is no need for ilb owner.
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+ * When the ilb owner becomes busy, we will not have new ilb owner until some
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+ * idle CPU wakes up and goes back to idle or some busy CPU tries to kick
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+ * idle load balancing by kicking one of the idle CPUs.
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*
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- * When the ilb owner becomes busy, it nominates another owner, during the
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- * next busy scheduler_tick()
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+ * Ticks are stopped for the ilb owner as well, with busy CPU kicking this
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+ * ilb owner CPU in future (when there is a need for idle load balancing on
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+ * behalf of all idle CPUs).
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*/
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-int select_nohz_load_balancer(int stop_tick)
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+void select_nohz_load_balancer(int stop_tick)
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{
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int cpu = smp_processor_id();
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if (stop_tick) {
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- cpu_rq(cpu)->in_nohz_recently = 1;
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-
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if (!cpu_active(cpu)) {
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if (atomic_read(&nohz.load_balancer) != cpu)
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- return 0;
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+ return;
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/*
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* If we are going offline and still the leader,
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* give up!
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*/
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- if (atomic_cmpxchg(&nohz.load_balancer, cpu, -1) != cpu)
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+ if (atomic_cmpxchg(&nohz.load_balancer, cpu,
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+ nr_cpu_ids) != cpu)
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BUG();
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- return 0;
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+ return;
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}
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- cpumask_set_cpu(cpu, nohz.cpu_mask);
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+ cpumask_set_cpu(cpu, nohz.idle_cpus_mask);
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- /* time for ilb owner also to sleep */
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- if (cpumask_weight(nohz.cpu_mask) == num_active_cpus()) {
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- if (atomic_read(&nohz.load_balancer) == cpu)
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- atomic_set(&nohz.load_balancer, -1);
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- return 0;
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- }
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+ if (atomic_read(&nohz.first_pick_cpu) == cpu)
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+ atomic_cmpxchg(&nohz.first_pick_cpu, cpu, nr_cpu_ids);
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+ if (atomic_read(&nohz.second_pick_cpu) == cpu)
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+ atomic_cmpxchg(&nohz.second_pick_cpu, cpu, nr_cpu_ids);
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- if (atomic_read(&nohz.load_balancer) == -1) {
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- /* make me the ilb owner */
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- if (atomic_cmpxchg(&nohz.load_balancer, -1, cpu) == -1)
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- return 1;
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- } else if (atomic_read(&nohz.load_balancer) == cpu) {
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+ if (atomic_read(&nohz.load_balancer) >= nr_cpu_ids) {
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int new_ilb;
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- if (!(sched_smt_power_savings ||
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- sched_mc_power_savings))
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- return 1;
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+ /* make me the ilb owner */
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+ if (atomic_cmpxchg(&nohz.load_balancer, nr_cpu_ids,
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+ cpu) != nr_cpu_ids)
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+ return;
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+
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/*
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* Check to see if there is a more power-efficient
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* ilb.
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*/
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new_ilb = find_new_ilb(cpu);
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if (new_ilb < nr_cpu_ids && new_ilb != cpu) {
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- atomic_set(&nohz.load_balancer, -1);
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+ atomic_set(&nohz.load_balancer, nr_cpu_ids);
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resched_cpu(new_ilb);
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- return 0;
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+ return;
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}
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- return 1;
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+ return;
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}
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} else {
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- if (!cpumask_test_cpu(cpu, nohz.cpu_mask))
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- return 0;
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+ if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
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+ return;
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- cpumask_clear_cpu(cpu, nohz.cpu_mask);
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+ cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
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if (atomic_read(&nohz.load_balancer) == cpu)
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- if (atomic_cmpxchg(&nohz.load_balancer, cpu, -1) != cpu)
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+ if (atomic_cmpxchg(&nohz.load_balancer, cpu,
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+ nr_cpu_ids) != cpu)
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BUG();
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}
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- return 0;
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+ return;
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}
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#endif
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@@ -3383,11 +3428,101 @@ out:
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rq->next_balance = next_balance;
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}
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+#ifdef CONFIG_NO_HZ
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/*
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- * run_rebalance_domains is triggered when needed from the scheduler tick.
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- * In CONFIG_NO_HZ case, the idle load balance owner will do the
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+ * In CONFIG_NO_HZ case, the idle balance kickee will do the
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* rebalancing for all the cpus for whom scheduler ticks are stopped.
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*/
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+static void nohz_idle_balance(int this_cpu, enum cpu_idle_type idle)
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+{
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+ struct rq *this_rq = cpu_rq(this_cpu);
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+ struct rq *rq;
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+ int balance_cpu;
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+
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+ if (idle != CPU_IDLE || !this_rq->nohz_balance_kick)
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+ return;
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+
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+ for_each_cpu(balance_cpu, nohz.idle_cpus_mask) {
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+ if (balance_cpu == this_cpu)
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+ continue;
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+
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+ /*
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+ * If this cpu gets work to do, stop the load balancing
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+ * work being done for other cpus. Next load
|
|
+ * balancing owner will pick it up.
|
|
+ */
|
|
+ if (need_resched()) {
|
|
+ this_rq->nohz_balance_kick = 0;
|
|
+ break;
|
|
+ }
|
|
+
|
|
+ raw_spin_lock_irq(&this_rq->lock);
|
|
+ update_cpu_load(this_rq);
|
|
+ raw_spin_unlock_irq(&this_rq->lock);
|
|
+
|
|
+ rebalance_domains(balance_cpu, CPU_IDLE);
|
|
+
|
|
+ rq = cpu_rq(balance_cpu);
|
|
+ if (time_after(this_rq->next_balance, rq->next_balance))
|
|
+ this_rq->next_balance = rq->next_balance;
|
|
+ }
|
|
+ nohz.next_balance = this_rq->next_balance;
|
|
+ this_rq->nohz_balance_kick = 0;
|
|
+}
|
|
+
|
|
+/*
|
|
+ * Current heuristic for kicking the idle load balancer
|
|
+ * - first_pick_cpu is the one of the busy CPUs. It will kick
|
|
+ * idle load balancer when it has more than one process active. This
|
|
+ * eliminates the need for idle load balancing altogether when we have
|
|
+ * only one running process in the system (common case).
|
|
+ * - If there are more than one busy CPU, idle load balancer may have
|
|
+ * to run for active_load_balance to happen (i.e., two busy CPUs are
|
|
+ * SMT or core siblings and can run better if they move to different
|
|
+ * physical CPUs). So, second_pick_cpu is the second of the busy CPUs
|
|
+ * which will kick idle load balancer as soon as it has any load.
|
|
+ */
|
|
+static inline int nohz_kick_needed(struct rq *rq, int cpu)
|
|
+{
|
|
+ unsigned long now = jiffies;
|
|
+ int ret;
|
|
+ int first_pick_cpu, second_pick_cpu;
|
|
+
|
|
+ if (time_before(now, nohz.next_balance))
|
|
+ return 0;
|
|
+
|
|
+ if (!rq->nr_running)
|
|
+ return 0;
|
|
+
|
|
+ first_pick_cpu = atomic_read(&nohz.first_pick_cpu);
|
|
+ second_pick_cpu = atomic_read(&nohz.second_pick_cpu);
|
|
+
|
|
+ if (first_pick_cpu < nr_cpu_ids && first_pick_cpu != cpu &&
|
|
+ second_pick_cpu < nr_cpu_ids && second_pick_cpu != cpu)
|
|
+ return 0;
|
|
+
|
|
+ ret = atomic_cmpxchg(&nohz.first_pick_cpu, nr_cpu_ids, cpu);
|
|
+ if (ret == nr_cpu_ids || ret == cpu) {
|
|
+ atomic_cmpxchg(&nohz.second_pick_cpu, cpu, nr_cpu_ids);
|
|
+ if (rq->nr_running > 1)
|
|
+ return 1;
|
|
+ } else {
|
|
+ ret = atomic_cmpxchg(&nohz.second_pick_cpu, nr_cpu_ids, cpu);
|
|
+ if (ret == nr_cpu_ids || ret == cpu) {
|
|
+ if (rq->nr_running)
|
|
+ return 1;
|
|
+ }
|
|
+ }
|
|
+ return 0;
|
|
+}
|
|
+#else
|
|
+static void nohz_idle_balance(int this_cpu, enum cpu_idle_type idle) { }
|
|
+#endif
|
|
+
|
|
+/*
|
|
+ * run_rebalance_domains is triggered when needed from the scheduler tick.
|
|
+ * Also triggered for nohz idle balancing (with nohz_balancing_kick set).
|
|
+ */
|
|
static void run_rebalance_domains(struct softirq_action *h)
|
|
{
|
|
int this_cpu = smp_processor_id();
|
|
@@ -3397,40 +3532,12 @@ static void run_rebalance_domains(struct softirq_action *h)
|
|
|
|
rebalance_domains(this_cpu, idle);
|
|
|
|
-#ifdef CONFIG_NO_HZ
|
|
/*
|
|
- * If this cpu is the owner for idle load balancing, then do the
|
|
+ * If this cpu has a pending nohz_balance_kick, then do the
|
|
* balancing on behalf of the other idle cpus whose ticks are
|
|
* stopped.
|
|
*/
|
|
- if (this_rq->idle_at_tick &&
|
|
- atomic_read(&nohz.load_balancer) == this_cpu) {
|
|
- struct rq *rq;
|
|
- int balance_cpu;
|
|
-
|
|
- for_each_cpu(balance_cpu, nohz.cpu_mask) {
|
|
- if (balance_cpu == this_cpu)
|
|
- continue;
|
|
-
|
|
- /*
|
|
- * If this cpu gets work to do, stop the load balancing
|
|
- * work being done for other cpus. Next load
|
|
- * balancing owner will pick it up.
|
|
- */
|
|
- if (need_resched())
|
|
- break;
|
|
-
|
|
- rq = cpu_rq(balance_cpu);
|
|
- raw_spin_lock_irq(&rq->lock);
|
|
- update_cpu_load(rq);
|
|
- raw_spin_unlock_irq(&rq->lock);
|
|
- rebalance_domains(balance_cpu, CPU_IDLE);
|
|
-
|
|
- if (time_after(this_rq->next_balance, rq->next_balance))
|
|
- this_rq->next_balance = rq->next_balance;
|
|
- }
|
|
- }
|
|
-#endif
|
|
+ nohz_idle_balance(this_cpu, idle);
|
|
}
|
|
|
|
static inline int on_null_domain(int cpu)
|
|
@@ -3440,57 +3547,17 @@ static inline int on_null_domain(int cpu)
|
|
|
|
/*
|
|
* Trigger the SCHED_SOFTIRQ if it is time to do periodic load balancing.
|
|
- *
|
|
- * In case of CONFIG_NO_HZ, this is the place where we nominate a new
|
|
- * idle load balancing owner or decide to stop the periodic load balancing,
|
|
- * if the whole system is idle.
|
|
*/
|
|
static inline void trigger_load_balance(struct rq *rq, int cpu)
|
|
{
|
|
-#ifdef CONFIG_NO_HZ
|
|
- /*
|
|
- * If we were in the nohz mode recently and busy at the current
|
|
- * scheduler tick, then check if we need to nominate new idle
|
|
- * load balancer.
|
|
- */
|
|
- if (rq->in_nohz_recently && !rq->idle_at_tick) {
|
|
- rq->in_nohz_recently = 0;
|
|
-
|
|
- if (atomic_read(&nohz.load_balancer) == cpu) {
|
|
- cpumask_clear_cpu(cpu, nohz.cpu_mask);
|
|
- atomic_set(&nohz.load_balancer, -1);
|
|
- }
|
|
-
|
|
- if (atomic_read(&nohz.load_balancer) == -1) {
|
|
- int ilb = find_new_ilb(cpu);
|
|
-
|
|
- if (ilb < nr_cpu_ids)
|
|
- resched_cpu(ilb);
|
|
- }
|
|
- }
|
|
-
|
|
- /*
|
|
- * If this cpu is idle and doing idle load balancing for all the
|
|
- * cpus with ticks stopped, is it time for that to stop?
|
|
- */
|
|
- if (rq->idle_at_tick && atomic_read(&nohz.load_balancer) == cpu &&
|
|
- cpumask_weight(nohz.cpu_mask) == num_online_cpus()) {
|
|
- resched_cpu(cpu);
|
|
- return;
|
|
- }
|
|
-
|
|
- /*
|
|
- * If this cpu is idle and the idle load balancing is done by
|
|
- * someone else, then no need raise the SCHED_SOFTIRQ
|
|
- */
|
|
- if (rq->idle_at_tick && atomic_read(&nohz.load_balancer) != cpu &&
|
|
- cpumask_test_cpu(cpu, nohz.cpu_mask))
|
|
- return;
|
|
-#endif
|
|
/* Don't need to rebalance while attached to NULL domain */
|
|
if (time_after_eq(jiffies, rq->next_balance) &&
|
|
likely(!on_null_domain(cpu)))
|
|
raise_softirq(SCHED_SOFTIRQ);
|
|
+#ifdef CONFIG_NO_HZ
|
|
+ else if (nohz_kick_needed(rq, cpu) && likely(!on_null_domain(cpu)))
|
|
+ nohz_balancer_kick(cpu);
|
|
+#endif
|
|
}
|
|
|
|
static void rq_online_fair(struct rq *rq)
|
|
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
|
|
index 1d7b9bc..5f171f0 100644
|
|
--- a/kernel/time/tick-sched.c
|
|
+++ b/kernel/time/tick-sched.c
|
|
@@ -408,13 +408,7 @@ void tick_nohz_stop_sched_tick(int inidle)
|
|
* the scheduler tick in nohz_restart_sched_tick.
|
|
*/
|
|
if (!ts->tick_stopped) {
|
|
- if (select_nohz_load_balancer(1)) {
|
|
- /*
|
|
- * sched tick not stopped!
|
|
- */
|
|
- cpumask_clear_cpu(cpu, nohz_cpu_mask);
|
|
- goto out;
|
|
- }
|
|
+ select_nohz_load_balancer(1);
|
|
|
|
ts->idle_tick = hrtimer_get_expires(&ts->sched_timer);
|
|
ts->tick_stopped = 1;
|
|
diff --git a/kernel/timer.c b/kernel/timer.c
|
|
index ee305c8..48d6aec 100644
|
|
--- a/kernel/timer.c
|
|
+++ b/kernel/timer.c
|
|
@@ -679,12 +679,8 @@ __mod_timer(struct timer_list *timer, unsigned long expires,
|
|
cpu = smp_processor_id();
|
|
|
|
#if defined(CONFIG_NO_HZ) && defined(CONFIG_SMP)
|
|
- if (!pinned && get_sysctl_timer_migration() && idle_cpu(cpu)) {
|
|
- int preferred_cpu = get_nohz_load_balancer();
|
|
-
|
|
- if (preferred_cpu >= 0)
|
|
- cpu = preferred_cpu;
|
|
- }
|
|
+ if (!pinned && get_sysctl_timer_migration() && idle_cpu(cpu))
|
|
+ cpu = get_nohz_timer_target();
|
|
#endif
|
|
new_base = per_cpu(tvec_bases, cpu);
|
|
|