<html><head><meta name="color-scheme" content="light dark"></head><body><pre style="word-wrap: break-word; white-space: pre-wrap;">
From: Chen Shang &lt;shangcs@gmail.com&gt;

micro-optimize task requeueing in schedule() &amp; clean up recalc_task_prio().

Signed-off-by: Ingo Molnar &lt;mingo@elte.hu&gt;
Signed-off-by: Andrew Morton &lt;akpm@osdl.org&gt;
---

 kernel/sched.c |   19 ++++++++++++-------
 1 files changed, 12 insertions(+), 7 deletions(-)

diff -puN kernel/sched.c~sched-micro-optimize-task-requeueing-in-schedule kernel/sched.c
--- 25/kernel/sched.c~sched-micro-optimize-task-requeueing-in-schedule	Mon May 23 16:01:42 2005
+++ 25-akpm/kernel/sched.c	Mon May 23 16:01:42 2005
@@ -675,7 +675,7 @@ static inline void __activate_idle_task(
 	rq-&gt;nr_running++;
 }
 
-static void recalc_task_prio(task_t *p, unsigned long long now)
+static int recalc_task_prio(task_t *p, unsigned long long now)
 {
 	/* Caller must always ensure 'now &gt;= p-&gt;timestamp' */
 	unsigned long long __sleep_time = now - p-&gt;timestamp;
@@ -734,7 +734,7 @@ static void recalc_task_prio(task_t *p, 
 		}
 	}
 
-	p-&gt;prio = effective_prio(p);
+	return effective_prio(p);
 }
 
 /*
@@ -757,7 +757,7 @@ static void activate_task(task_t *p, run
 	}
 #endif
 
-	recalc_task_prio(p, now);
+	p-&gt;prio = recalc_task_prio(p, now);
 
 	/*
 	 * This checks to make sure it's not an uninterruptible task
@@ -2751,7 +2751,7 @@ asmlinkage void __sched schedule(void)
 	struct list_head *queue;
 	unsigned long long now;
 	unsigned long run_time;
-	int cpu, idx;
+	int cpu, idx, new_prio;
 
 	/*
 	 * Test if we are atomic.  Since do_exit() needs to call into
@@ -2873,9 +2873,14 @@ go_idle:
 			delta = delta * (ON_RUNQUEUE_WEIGHT * 128 / 100) / 128;
 
 		array = next-&gt;array;
-		dequeue_task(next, array);
-		recalc_task_prio(next, next-&gt;timestamp + delta);
-		enqueue_task(next, array);
+		new_prio = recalc_task_prio(next, next-&gt;timestamp + delta);
+
+		if (unlikely(next-&gt;prio != new_prio)) {
+			dequeue_task(next, array);
+			next-&gt;prio = new_prio;
+			enqueue_task(next, array);
+		} else
+			requeue_task(next, array);
 	}
 	next-&gt;activated = 0;
 switch_tasks:
_
</pre></body></html>