linux-kernel - [PATCH v4 2/2] sched: consider missed ticks in full NOHZ

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Date:	Wed, 14 Oct 2015 18:47:36 +0900
From:	<byungchul.park@....com>
To:	mingo@...nel.org, peterz@...radead.org
CC:	linux-kernel@...r.kernel.org, fweisbec@...il.com,
	tglx@...utronix.de, Byungchul Park <byungchul.park@....com>
Subject: [PATCH v4 2/2] sched: consider missed ticks in full NOHZ

From: Byungchul Park <byungchul.park@....com>

Even though the cpu is non-idle when its tick is stoped in full NOHZ,
current "update_cpu_load" code considers as if the cpu has been idle
unconditionally. It's wrong. This patch makes the "update_cpu_load"
code know if the calling path comes from full NOHZ or idle NOHZ.

Signed-off-by: Byungchul Park <byungchul.park@....com>
---
 include/linux/sched.h    |    4 ++--
 kernel/sched/fair.c      |    4 ++--
 kernel/time/tick-sched.c |    8 ++++----
 3 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 699228b..f1b59aa 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -177,9 +177,9 @@ extern void get_iowait_load(unsigned long *nr_waiters, unsigned long *load);
 extern void calc_global_load(unsigned long ticks);
 
 #if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
-extern void update_cpu_load_nohz(void);
+extern void update_cpu_load_nohz(int active);
 #else
-static inline void update_cpu_load_nohz(void) { }
+static inline void update_cpu_load_nohz(int active) { }
 #endif
 
 extern unsigned long get_parent_ip(unsigned long addr);
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 26473fc..63c5ffd 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4428,7 +4428,7 @@ static void update_idle_cpu_load(struct rq *this_rq)
 /*
  * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
  */
-void update_cpu_load_nohz(void)
+void update_cpu_load_nohz(int active)
 {
 	struct rq *this_rq = this_rq();
 	unsigned long curr_jiffies = READ_ONCE(jiffies);
@@ -4445,7 +4445,7 @@ void update_cpu_load_nohz(void)
 		 * We were idle, this means load 0, the current load might be
 		 * !0 due to remote wakeups and the sort.
 		 */
-		__update_cpu_load(this_rq, 0, pending_updates, 0);
+		__update_cpu_load(this_rq, 0, pending_updates, active);
 	}
 	raw_spin_unlock(&this_rq->lock);
 }
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 7c7ec45..515edf3 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -694,11 +694,11 @@ out:
 	return tick;
 }
 
-static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
+static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now, int active)
 {
 	/* Update jiffies first */
 	tick_do_update_jiffies64(now);
-	update_cpu_load_nohz();
+	update_cpu_load_nohz(active);
 
 	calc_load_exit_idle();
 	touch_softlockup_watchdog();
@@ -725,7 +725,7 @@ static void tick_nohz_full_update_tick(struct tick_sched *ts)
 	if (can_stop_full_tick())
 		tick_nohz_stop_sched_tick(ts, ktime_get(), cpu);
 	else if (ts->tick_stopped)
-		tick_nohz_restart_sched_tick(ts, ktime_get());
+		tick_nohz_restart_sched_tick(ts, ktime_get(), 1);
 #endif
 }
 
@@ -916,7 +916,7 @@ void tick_nohz_idle_exit(void)
 		tick_nohz_stop_idle(ts, now);
 
 	if (ts->tick_stopped) {
-		tick_nohz_restart_sched_tick(ts, now);
+		tick_nohz_restart_sched_tick(ts, now, 0);
 		tick_nohz_account_idle_ticks(ts);
 	}
 
-- 
1.7.9.5

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