[PATCH] nohz: Remove update_ts_time_stat from tick_nohz_start_idle

[PATCH] nohz: Remove update_ts_time_stat from tick_nohz_start_idle

[Michal Hocko]

There is no reason to call update_ts_time_stat from tick_nohz_start_idle
anymore (after e0e37c20 sched: Eliminate the ts->idle_lastupdate field)
when we updated idle_lastupdate unconditionally.

We haven't set idle_active yet and do not provide last_update_time so
the whole call end up being just 2 wasted branches.

Signed-off-by: Michal Hocko <mhocko@suse.cz>
CC: Arjan van de Ven <arjan@linux.intel.com>
CC: Thomas Gleixner <tglx@linutronix.de>
---
 kernel/time/tick-sched.c |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 4042064..be3cab0 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -186,8 +186,6 @@ static ktime_t tick_nohz_start_idle(int cpu, struct tick_sched *ts)
 
 	now = ktime_get();
 
-	update_ts_time_stats(cpu, ts, now, NULL);
-
 	ts->idle_entrytime = now;
 	ts->idle_active = 1;
 	sched_clock_idle_sleep_event();
-- 
1.7.7.3

Re: [PATCH] nohz: Remove update_ts_time_stat from tick_nohz_start_idle

[Frederic Weisbecker]

On Thu, Dec 01, 2011 at 05:00:22PM +0100, Michal Hocko wrote:
> There is no reason to call update_ts_time_stat from tick_nohz_start_idle
> anymore (after e0e37c20 sched: Eliminate the ts->idle_lastupdate field)
> when we updated idle_lastupdate unconditionally.
> 
> We haven't set idle_active yet and do not provide last_update_time so
> the whole call end up being just 2 wasted branches.
> 
> Signed-off-by: Michal Hocko <mhocko@suse.cz>
> CC: Arjan van de Ven <arjan@linux.intel.com>
> CC: Thomas Gleixner <tglx@linutronix.de>

Reviewed-by Frederic Weisbecker <fweisbec@gmail.com>

Re: [PATCH] nohz: Remove update_ts_time_stat from tick_nohz_start_idle

[Kamalesh Babulal]

* Michal Hocko <mhocko@suse.cz> [2011-12-01 17:00:22]:

> There is no reason to call update_ts_time_stat from tick_nohz_start_idle
> anymore (after e0e37c20 sched: Eliminate the ts->idle_lastupdate field)
> when we updated idle_lastupdate unconditionally.
> 
> We haven't set idle_active yet and do not provide last_update_time so
> the whole call end up being just 2 wasted branches.
> 
> Signed-off-by: Michal Hocko <mhocko@suse.cz>
> CC: Arjan van de Ven <arjan@linux.intel.com>
> CC: Thomas Gleixner <tglx@linutronix.de>

Reviewed-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>

[tip:timers/core] nohz: Remove update_ts_time_stat from tick_nohz_start_idle

[tip-bot for Michal Hocko]

Commit-ID:  430ee8819553f66fe00e36f676a45886d76e7e8b
Gitweb:     http://git.kernel.org/tip/430ee8819553f66fe00e36f676a45886d76e7e8b
Author:     Michal Hocko <mhocko@suse.cz>
AuthorDate: Thu, 1 Dec 2011 17:00:22 +0100
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Wed, 15 Feb 2012 15:23:09 +0100

nohz: Remove update_ts_time_stat from tick_nohz_start_idle

There is no reason to call update_ts_time_stat from tick_nohz_start_idle
anymore (after e0e37c20 sched: Eliminate the ts->idle_lastupdate field)
when we updated idle_lastupdate unconditionally.

We haven't set idle_active yet and do not provide last_update_time so
the whole call end up being just 2 wasted branches.

Signed-off-by: Michal Hocko <mhocko@suse.cz>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Link: http://lkml.kernel.org/r/1322755222-6951-1-git-send-email-mhocko@suse.cz
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 kernel/time/tick-sched.c |    6 +-----
 1 files changed, 1 insertions(+), 5 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 7656642..8cfffd9 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -182,11 +182,7 @@ static void tick_nohz_stop_idle(int cpu, ktime_t now)
 
 static ktime_t tick_nohz_start_idle(int cpu, struct tick_sched *ts)
 {
-	ktime_t now;
-
-	now = ktime_get();
-
-	update_ts_time_stats(cpu, ts, now, NULL);
+	ktime_t now = ktime_get();
 
 	ts->idle_entrytime = now;
 	ts->idle_active = 1;