Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1763179AbXHXNp2 (ORCPT ); Fri, 24 Aug 2007 09:45:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753172AbXHXNpV (ORCPT ); Fri, 24 Aug 2007 09:45:21 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:39948 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753015AbXHXNpU (ORCPT ); Fri, 24 Aug 2007 09:45:20 -0400 Date: Fri, 24 Aug 2007 15:45:10 +0200 From: Ingo Molnar To: Al Boldi Cc: Peter Zijlstra , Mike Galbraith , Andrew Morton , Linus Torvalds , linux-kernel@vger.kernel.org Subject: Re: CFS review Message-ID: <20070824134510.GA21382@elte.hu> References: <200708111344.42934.a1426z@gawab.com> <200708122243.05191.a1426z@gawab.com> <20070821105858.GC26598@elte.hu> <200708220127.30698.a1426z@gawab.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200708220127.30698.a1426z@gawab.com> User-Agent: Mutt/1.5.14 (2007-02-12) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.1.7-deb -1.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2519 Lines: 67 * Al Boldi wrote: > > > The problem is that consecutive runs don't give consistent results > > > and sometimes stalls. You may want to try that. > > > > well, there's a natural saturation point after a few hundred tasks > > (depending on your CPU's speed), at which point there's no idle time > > left. From that point on things get slower progressively (and the > > ability of the shell to start new ping tasks is impacted as well), > > but that's expected on an overloaded system, isnt it? > > Of course, things should get slower with higher load, but it should be > consistent without stalls. > > To see this problem, make sure you boot into /bin/sh with the normal > VGA console (ie. not fb-console). Then try each loop a few times to > show different behaviour; loops like: > > # for ((i=0; i<3333; i++)); do ping 10.1 -A > /dev/null & done > > # for ((i=0; i<3333; i++)); do nice -99 ping 10.1 -A > /dev/null & done > > # { for ((i=0; i<3333; i++)); do > ping 10.1 -A > /dev/null & > done } > /dev/null 2>&1 > > Especially the last one sometimes causes a complete console lock-up, > while the other two sometimes stall then surge periodically. ok. I think i might finally have found the bug causing this. Could you try the fix below, does your webserver thread-startup test work any better? Ingo ---------------------------> Subject: sched: fix startup penalty calculation From: Ingo Molnar fix task startup penalty miscalculation: sysctl_sched_granularity is unsigned int and wait_runtime is long so we first have to convert it to long before turning it negative ... Signed-off-by: Ingo Molnar --- kernel/sched_fair.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) Index: linux/kernel/sched_fair.c =================================================================== --- linux.orig/kernel/sched_fair.c +++ linux/kernel/sched_fair.c @@ -1048,7 +1048,7 @@ static void task_new_fair(struct rq *rq, * -granularity/2, so initialize the task with that: */ if (sysctl_sched_features & SCHED_FEAT_START_DEBIT) - p->se.wait_runtime = -(sysctl_sched_granularity / 2); + p->se.wait_runtime = -((long)sysctl_sched_granularity / 2); __enqueue_entity(cfs_rq, se); } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/