linux-kernel - Re: [RFC] [PATCH 0/3] Add group fairness to CFS

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Date:	Fri, 25 May 2007 13:15:00 +0530
From:	Srivatsa Vaddagiri <vatsa@...ibm.com>
To:	Guillaume Chazarain <guichaz@...oo.fr>
Cc:	Ingo Molnar <mingo@...e.hu>, Nick Piggin <nickpiggin@...oo.com.au>,
	efault@....de, kernel@...ivas.org, containers@...ts.osdl.org,
	ckrm-tech@...ts.sourceforge.net, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, pwil3058@...pond.net.au,
	tingy@...umass.edu, tong.n.li@...el.com, wli@...omorphy.com,
	linux-kernel@...r.kernel.org, Balbir Singh <balbir@...ibm.com>
Subject: Re: [RFC] [PATCH 0/3] Add group fairness to CFS

On Thu, May 24, 2007 at 12:26:16AM +0200, Guillaume Chazarain wrote:
> As a sidenote, while in CFS-v13 a nice=0 tasks seems to get 10x more CPU 
> than a nice=10 one, with the group fairness patch, the ratio drops to 
> less than 2x (for tasks with the same UID).

gah ..silly me.

Can you repeat your tests with this patch pls? With the patch applied, I am
now getting the same split between nice 0 and nice 10 task as CFS-v13
provides (90:10 as reported by top )

 5418 guest     20   0  2464  304  236 R   90  0.0   5:41.40 3 hog
 5419 guest     30  10  2460  304  236 R   10  0.0   0:43.62 3 nice10hog



Fix a stupid bug, where I was not calling __check_preempt_curr_fair()
at task level during task_tick ..

Signed-off-by : Srivatsa Vaddagiri <vatsa@...ibm.com>


---


diff -puN kernel/sched_fair.c~fix kernel/sched_fair.c
--- linux-2.6.22-rc1-cfs-group/kernel/sched_fair.c~fix	2007-05-25 12:28:52.000000000 +0530
+++ linux-2.6.22-rc1-cfs-group-vatsa/kernel/sched_fair.c	2007-05-25 12:30:06.000000000 +0530
@@ -577,11 +577,12 @@ static void entity_tick(struct lrq *lrq,
 				   *n = task_entity(next);
 
 		if ((c == lrq->rq->idle) || (rt_prio(n->prio) &&
-						(n->prio < c->prio)))
+						(n->prio < c->prio))) {
 			resched_task(c);
-	} else
-		__check_preempt_curr_fair(lrq, next, curr,
-					  *(lrq->sched_granularity));
+			return;
+		}
+	}
+	__check_preempt_curr_fair(lrq, next, curr, *(lrq->sched_granularity));
 }
 
 static void _update_load(struct lrq *this_rq)
_


-- 
Regards,
vatsa
-
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