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[PATCH 0/3] sched: A few nohz_full improvements

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  [PATCH 0/3] sched: A few nohz_full improvements Frederic Weisbecker <fweisbec@gmail.com> - 2017-06-19 04:20 +0200
    [PATCH 2/3] nohz: Move idle balancer registration to idle path Frederic Weisbecker <fweisbec@gmail.com> - 2017-06-19 04:20 +0200

#1668723 — [PATCH 0/3] sched: A few nohz_full improvements

Hi,

As I was working on removing the remaining 1Hz, I stepped in the last
(AFAIK) remaining buggy bits in scheduler_tick() on nohz_full.

Hopefully I can finally offload this tick in the next patchsets.

git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git
	nohz/0hz

HEAD: c1811204f1fd1d170223c0d548a57456685e831d

Thanks,
	Frederic
---

Frederic Weisbecker (3):
      sched/loadavg: Generalize idle naming to nohz
      nohz: Move idle balancer registration to idle path
      sched: Spare idle load balancing on nohz_full CPUs


 Documentation/trace/ftrace.txt |  2 +-
 include/linux/sched/nohz.h     |  8 +++----
 kernel/sched/fair.c            |  4 ++++
 kernel/sched/loadavg.c         | 51 +++++++++++++++++++++---------------------
 kernel/time/tick-sched.c       |  9 ++++----
 5 files changed, 40 insertions(+), 34 deletions(-)

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#1668725 — [PATCH 2/3] nohz: Move idle balancer registration to idle path

The idle load balancing registration path assumes that we only stop the
tick when the CPU is idle, ignoring the nohz full case. As a result, a
nohz full CPU that is running a task may be chosen to perform idle load
balancing.

Lets make sure that only CPUs in dynticks idle mode can be picked as
idle load balancers.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
---
 kernel/time/tick-sched.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 1c9a508..77c3be5 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -785,7 +785,6 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
 	 * the scheduler tick in nohz_restart_sched_tick.
 	 */
 	if (!ts->tick_stopped) {
-		nohz_balance_enter_idle(cpu);
 		calc_load_nohz_start();
 		cpu_load_update_nohz_start();
 
@@ -938,8 +937,10 @@ static void __tick_nohz_idle_enter(struct tick_sched *ts)
 			ts->idle_expires = expires;
 		}
 
-		if (!was_stopped && ts->tick_stopped)
+		if (!was_stopped && ts->tick_stopped) {
 			ts->idle_jiffies = ts->last_jiffies;
+			nohz_balance_enter_idle(cpu);
+		}
 	}
 }
 
-- 
2.7.4

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