From: Andrew Theurer <habanero@us.ibm.com>
To: linux-kernel@vger.kernel.org
Subject: CAN_MIGRATE seems screwed up
Date: Wed, 27 Aug 2003 10:07:59 -0500
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OK, not sure how long this has been this way, but:

#define CAN_MIGRATE_TASK(p,rq,this_cpu)					\
	((!idle || (jiffies - (p)->last_run > cache_decay_ticks)) &&    \
		!task_running(rq, p) &&					\
			cpu_isset(this_cpu, (p)->cpus_allowed))		

Is broken.  Having !idle make no sense.  It should be just the opposite; an 
idle cpu should be able to have a more aggressive steal, and a busy cpu 
should not. 

diff -Naurp linux-2.6.0-test4/kernel/sched.c 
linux-2.6.0-test4-can_migrate/kernel/sched.c
--- linux-2.6.0-test4/kernel/sched.c	Fri Aug 22 18:58:43 2003
+++ linux-2.6.0-test4-can_migrate/kernel/sched.c	Wed Aug 27 11:32:46 2003
@@ -1064,7 +1064,7 @@ skip_queue:
 	 */
 
 #define CAN_MIGRATE_TASK(p,rq,this_cpu)					\
-	((!idle || (jiffies - (p)->last_run > cache_decay_ticks)) &&	\
+	((idle || (jiffies - (p)->last_run > cache_decay_ticks)) &&	\
 		!task_running(rq, p) &&					\
 			cpu_isset(this_cpu, (p)->cpus_allowed))
 

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