linux-kernel - [RFC PATCH 4/4] sched/nohz_full: give correct cpu load for nohz

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Date:	Fri, 22 Nov 2013 14:37:15 +0800
From:	Alex Shi <alex.shi@...aro.org>
To:	mingo@...hat.com, peterz@...radead.org, morten.rasmussen@....com,
	vincent.guittot@...aro.org, daniel.lezcano@...aro.org,
	fweisbec@...il.com, linux@....linux.org.uk, tony.luck@...el.com,
	fenghua.yu@...el.com, tglx@...utronix.de,
	akpm@...ux-foundation.org, arjan@...ux.intel.com, pjt@...gle.com,
	fengguang.wu@...el.com
Cc:	james.hogan@...tec.com, alex.shi@...aro.org, jason.low2@...com,
	gregkh@...uxfoundation.org, hanjun.guo@...aro.org,
	linux-kernel@...r.kernel.org
Subject: [RFC PATCH 4/4] sched/nohz_full: give correct cpu load for nohz_full cpu

When a nohz_full cpu in tickless mode, it may update cpu_load in
following chain:
__tick_nohz_full_check
    tick_nohz_restart_sched_tick
        update_cpu_load_nohz
then it will be set a incorrect cpu_load: 0.
This patch try to fix it and give it the correct cpu_load value.

Signed-off-by: Alex Shi <alex.shi@...aro.org>
---
 kernel/sched/proc.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/proc.c b/kernel/sched/proc.c
index 057bb9b..5058e6a 100644
--- a/kernel/sched/proc.c
+++ b/kernel/sched/proc.c
@@ -477,10 +477,16 @@ void update_cpu_load_nohz(void)
 	if (pending_updates) {
 		this_rq->last_load_update_tick = curr_jiffies;
 		/*
-		 * We were idle, this means load 0, the current load might be
-		 * !0 due to remote wakeups and the sort.
+		 * We may has one task and in NO_HZ_FULL, then use normal
+		 * cfs load.
+		 * Or 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);
+		if (this_rq->cfs.h_nr_running) {
+			unsigned load = get_rq_runnable_load(this_rq);
+			__update_cpu_load(this_rq, load);
+		} else
+			__update_cpu_load(this_rq, 0);
 	}
 	raw_spin_unlock(&this_rq->lock);
 }
-- 
1.8.1.2

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