linux-kernel - [RFC PATCH 3/4] linsched: avoid invoke tick_nohz_idle

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Message-ID: <50442AD2.6060109@linux.vnet.ibm.com>
Date:	Mon, 03 Sep 2012 11:58:10 +0800
From:	Michael Wang <wangyun@...ux.vnet.ibm.com>
To:	LKML <linux-kernel@...r.kernel.org>
CC:	Paul Turner <pjt@...gle.com>,
	Dhaval Giani <dhaval.giani@...il.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: [RFC PATCH 3/4] linsched: avoid invoke tick_nohz_idle_enter() multiple
 times in idle

From: Michael Wang <wangyun@...ux.vnet.ibm.com>

In real world, tick_nohz_idle_enter() will be invoked by idle thread 
when the cpu change from active to idle, and will only be invoked
again after tick_nohz_idle_exit() was invoked by idle thread when
cpu is going to recover, invoke it multiple times in one idle may
cause unexpected troubles.

The patch add a check to avoid invoke tick_nohz_idle_enter() again
after idle.

Signed-off-by: Michael Wang <wangyun@...ux.vnet.ibm.com>
---
 tools/linsched/hrtimer.c |   11 ++++++++++-
 1 files changed, 10 insertions(+), 1 deletions(-)

diff --git a/tools/linsched/hrtimer.c b/tools/linsched/hrtimer.c
index de88b25..3203253 100644
--- a/tools/linsched/hrtimer.c
+++ b/tools/linsched/hrtimer.c
@@ -149,6 +149,15 @@ void linsched_check_idle_cpu(void)
        } 
 }
 
+void linsched_enter_idle(void)
+{
+       int cpu = smp_processor_id();
+       struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+
+       if (!ts->inidle && idle_cpu(cpu))
+               tick_nohz_idle_enter();
+}              
+
 /* Run a simulation for some number of ticks. Each tick,
  * scheduling and load balancing decisions are made. Obviously, we
  * could create tasks, change priorities, etc., at certain ticks
@@ -210,7 +219,7 @@ void linsched_run_sim(int sim_ticks)
 
                        BUG_ON(irqs_disabled());
                        if (idle_cpu(active_cpu) && !need_resched()) {
-                               tick_nohz_idle_enter();
+                               linsched_enter_idle();
                        } else {
                                linsched_current_handler();
                        }
-- 
1.7.1

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