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[Xen-devel] RE: [PATCH] only set scheduler timer for non-idle CPU

To: "Yu, Ke" <ke.yu@xxxxxxxxx>, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Subject: [Xen-devel] RE: [PATCH] only set scheduler timer for non-idle CPU
From: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
Date: Wed, 1 Apr 2009 22:02:09 +0800
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Thread-topic: [PATCH] only set scheduler timer for non-idle CPU
Keir, how's your thought on below change? It makes sense even
not in power context. Ask here in case you didn't not it :-)


>From: Yu, Ke 
>Sent: 2009年3月31日 11:14
>It is not necessary to set scheduler timer for idle CPU. so 
>this patch add conditional check for idle CPU.
>This patch remove the last idle periodic timer in xen, thus 
>enhance the idle average C state residency from two-digits ms 
>to three-digit ms.
>Signed-off-by:  Yu Ke <ke.yu@xxxxxxxxx>
>                Tian Kevin <kevin.tian@xxxxxxxxx>
>diff -r e4bfa70d587c xen/common/schedule.c
>--- a/xen/common/schedule.c
>+++ b/xen/common/schedule.c
>@@ -819,7 +819,10 @@ static void schedule(void)
>     sd->curr = next;
>-    set_timer(&sd->s_timer, now + r_time);
>+    if ( !is_idle_vcpu(next) )
>+    {
>+        set_timer(&sd->s_timer, now + r_time);
>+    }
>     if ( unlikely(prev == next) )
>     {
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