RE: Regression seen for patch "sched:dont decrease idle sleep avg"

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

Con Kolivas wrote on Wednesday, May 17, 2006 10:52 PM
> The relationship between INTERACTIVE_SLEEP and the ceiling is not perfect
> and not explicit enough. The sleep boost is not supposed to be any larger
> than without this code and the comment is not clear enough about what exactly
> it does, just the reason it does it.
> 
> There is a ceiling to the priority beyond which tasks that only ever sleep
> for very long periods cannot surpass.
> 
> Opportunity to micro-optimise and re-use the ceiling variable.


More opportunity to micro-optimize: now that you've put the clamp code of
p->sleep_avg in the common path, there is no need to clamp sleep_time at
the beginning of that function.  Just let the calculation go through and
clamp the final value of p->sleep_avg to NS_MAX_SLEEP_AVG at the end.

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

--- ./kernel/sched.c.orig	2006-05-18 12:51:45.000000000 -0700
+++ ./kernel/sched.c	2006-05-18 14:53:47.000000000 -0700
@@ -731,17 +731,10 @@
 static int recalc_task_prio(task_t *p, unsigned long long now)
 {
 	/* Caller must always ensure 'now >= p->timestamp' */
-	unsigned long long __sleep_time = now - p->timestamp;
-	unsigned long sleep_time;
+	unsigned long sleep_time = now - p->timestamp;
 
 	if (batch_task(p))
 		sleep_time = 0;
-	else {
-		if (__sleep_time > NS_MAX_SLEEP_AVG)
-			sleep_time = NS_MAX_SLEEP_AVG;
-		else
-			sleep_time = (unsigned long)__sleep_time;
-	}
 
 	if (likely(sleep_time > 0)) {
 		/*