[patch 1/2] fix perf. bug in wake-up load balancing for aim7 and db workload

["Chen, Kenneth W" <kenneth.w.chen@intel.com>]

Revert commit d7102e95b7b9c00277562c29aad421d2d521c5f6,
which causes more than 10% performance regression with aim7.


Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>

--- linux-2.6.16-rc2/include/linux/sched.h.orig	2006-02-13 18:15:09.660276655 -0800
+++ linux-2.6.16-rc2/include/linux/sched.h	2006-02-13 18:15:36.234495079 -0800
@@ -697,12 +697,9 @@ struct task_struct {
 
 	int lock_depth;		/* BKL lock depth */
 
-#if defined(CONFIG_SMP)
-	int last_waker_cpu;	/* CPU that last woke this task up */
-#if defined(__ARCH_WANT_UNLOCKED_CTXSW)
+#if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
 	int oncpu;
 #endif
-#endif
 	int prio, static_prio;
 	struct list_head run_list;
 	prio_array_t *array;
--- linux-2.6.16-rc2/kernel/sched.c.orig	2006-02-13 18:11:28.946412171 -0800
+++ linux-2.6.16-rc2/kernel/sched.c	2006-02-13 18:14:29.595824020 -0800
@@ -1294,9 +1294,6 @@ static int try_to_wake_up(task_t *p, uns
 		}
 	}
 
-	if (p->last_waker_cpu != this_cpu)
-		goto out_set_cpu;
-
 	if (unlikely(!cpu_isset(this_cpu, p->cpus_allowed)))
 		goto out_set_cpu;
 
@@ -1367,8 +1364,6 @@ out_set_cpu:
 		cpu = task_cpu(p);
 	}
 
-	p->last_waker_cpu = this_cpu;
-
 out_activate:
 #endif /* CONFIG_SMP */
 	if (old_state == TASK_UNINTERRUPTIBLE) {
@@ -1450,12 +1445,9 @@ void fastcall sched_fork(task_t *p, int 
 #ifdef CONFIG_SCHEDSTATS
 	memset(&p->sched_info, 0, sizeof(p->sched_info));
 #endif
-#if defined(CONFIG_SMP)
-	p->last_waker_cpu = cpu;
-#if defined(__ARCH_WANT_UNLOCKED_CTXSW)
+#if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW)
 	p->oncpu = 0;
 #endif
-#endif
 #ifdef CONFIG_PREEMPT
 	/* Want to start with kernel preemption disabled. */
 	task_thread_info(p)->preempt_count = 1;

-
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