linux-kernel - [RFC PATCH v2 7/7] sched/idle: update poll time when wakeup from idle

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Date:   Tue, 29 Aug 2017 11:46:41 +0000
From:   Yang Zhang <yang.zhang.wz@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     kvm@...r.kernel.org, wanpeng.li@...mail.com, mst@...hat.com,
        pbonzini@...hat.com, tglx@...utronix.de, rkrcmar@...hat.com,
        dmatlack@...gle.com, agraf@...e.de, peterz@...radead.org,
        linux-doc@...r.kernel.org, Yang Zhang <yang.zhang.wz@...il.com>,
        Quan Xu <quan.xu0@...il.com>, Ingo Molnar <mingo@...hat.com>
Subject: [RFC PATCH v2 7/7] sched/idle: update poll time when wakeup from idle

In ttwu_do_wakeup, it will update avg_idle when wakeup from idle. Here
we just reuse this logic to update the poll time. It may be a little
late to update the poll in ttwu_do_wakeup, but the test result shows no
obvious performance gap compare with updating poll in irq handler.

one problem is that idle_stamp only used when using CFS scheduler. But
it is ok since it is the default policy for scheduler and only consider
it should enough.

Signed-off-by: Yang Zhang <yang.zhang.wz@...il.com>
Signed-off-by: Quan Xu <quan.xu0@...il.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: linux-kernel@...r.kernel.org
---
 include/linux/sched/idle.h | 4 ++++
 kernel/sched/core.c        | 4 ++++
 kernel/sched/idle.c        | 7 +++++++
 3 files changed, 15 insertions(+)

diff --git a/include/linux/sched/idle.h b/include/linux/sched/idle.h
index 5ca63eb..6e0554d 100644
--- a/include/linux/sched/idle.h
+++ b/include/linux/sched/idle.h
@@ -12,6 +12,10 @@ enum cpu_idle_type {
 
 extern void wake_up_if_idle(int cpu);
 
+#if defined(CONFIG_SMP) && defined(CONFIG_PARAVIRT)
+extern void update_poll_duration(unsigned long idle_duration);
+#endif
+
 /*
  * Idle thread specific functions to determine the need_resched
  * polling state.
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 0869b20..25be9a3 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1678,6 +1678,10 @@ static void ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags,
 		if (rq->avg_idle > max)
 			rq->avg_idle = max;
 
+#if defined(CONFIG_PARAVIRT)
+		update_poll_duration(rq->avg_idle);
+#endif
+
 		rq->idle_stamp = 0;
 	}
 #endif
diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index b374744..7eb8559 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -101,6 +101,13 @@ void __cpuidle default_idle_call(void)
 	}
 }
 
+#if defined(CONFIG_SMP) && defined(CONFIG_PARAVIRT)
+void update_poll_duration(unsigned long idle_duration)
+{
+	paravirt_idle_update_poll_duration(idle_duration);
+}
+#endif
+
 static int call_cpuidle(struct cpuidle_driver *drv, struct cpuidle_device *dev,
 		      int next_state)
 {
-- 
1.8.3.1