lkml.org 
[lkml]   [2021]   [Feb]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 6/7 v2] sched/fair: trigger the update of blocked load on newly idle cpu
Date
Instead of waking up a random and already idle CPU, we can take advantage
of this_cpu being about to enter idle to run the ILB and update the
blocked load.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
---
kernel/sched/fair.c | 20 +++++++++++++++++---
kernel/sched/idle.c | 6 ++++++
kernel/sched/sched.h | 3 +++
3 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 5d285d93e433..d11a632ea276 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -10453,6 +10453,20 @@ static bool nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
return true;
}

+void nohz_run_idle_balance(int cpu)
+{
+ unsigned int flags;
+
+ flags = atomic_fetch_andnot(NOHZ_KICK_MASK, nohz_flags(cpu));
+
+ if (flags && !need_resched()) {
+ struct rq *rq = cpu_rq(cpu);
+
+ rq->nohz_idle_balance = flags;
+ nohz_idle_balance(rq, CPU_IDLE);
+ }
+}
+
static void nohz_newidle_balance(struct rq *this_rq)
{
int this_cpu = this_rq->cpu;
@@ -10474,10 +10488,10 @@ static void nohz_newidle_balance(struct rq *this_rq)
return;

/*
- * Blocked load of idle CPUs need to be updated.
- * Kick an ILB to update statistics.
+ * Set the need to trigger ILB in order to update blocked load
+ * before entering idle state.
*/
- kick_ilb(NOHZ_STATS_KICK);
+ atomic_or(NOHZ_STATS_KICK, nohz_flags(this_cpu));
}

#else /* !CONFIG_NO_HZ_COMMON */
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index 305727ea0677..52a4e9ce2f9b 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -261,6 +261,12 @@ static void cpuidle_idle_call(void)
static void do_idle(void)
{
int cpu = smp_processor_id();
+
+ /*
+ * Check if we need to update some blocked load
+ */
+ nohz_run_idle_balance(cpu);
+
/*
* If the arch has a polling bit, we maintain an invariant:
*
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 6edc67df3554..a11ec9110992 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -2370,8 +2370,11 @@ extern void cfs_bandwidth_usage_dec(void);
#define nohz_flags(cpu) (&cpu_rq(cpu)->nohz_flags)

extern void nohz_balance_exit_idle(struct rq *rq);
+extern void nohz_run_idle_balance(int cpu);
#else
+
static inline void nohz_balance_exit_idle(struct rq *rq) { }
+static inline void nohz_run_idle_balance(int cpu) { }
#endif


--
2.17.1
\
 
 \ /
  Last update: 2021-02-12 14:35    [W:0.185 / U:0.132 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site