From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761453AbXGKRsR (ORCPT ); Wed, 11 Jul 2007 13:48:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755509AbXGKRsI (ORCPT ); Wed, 11 Jul 2007 13:48:08 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:37364 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752419AbXGKRsG (ORCPT ); Wed, 11 Jul 2007 13:48:06 -0400 Date: Wed, 11 Jul 2007 19:47:59 +0200 From: Ingo Molnar To: Martin Bligh Cc: LKML , Andy Whitcroft Subject: Re: Performance regression in 2.6.22-git1 (new sched code?) Message-ID: <20070711174759.GA17471@elte.hu> References: <4693C3D2.9020005@mbligh.org> <20070710210945.GA4231@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070710210945.GA4231@elte.hu> 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=3.0.3 -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 * Ingo Molnar wrote: > > http://test.kernel.org/perf/kernbench.elm3b132.png > > thx! I'll check this tomorrow, meanwhile here are a few quick ideas. ok, i've re-tested this, and could you please try the fix attached below, combined with a CONFIG_HZ=100 run and with SCHED_DEBUG disabled? I think a fair bit of the overhead comes from granularity being capped to 10 msecs instead of the intended 100 msecs. Ingo ---------------------------------------------> Subject: [patch] sched: allow larger granularity From: Ingo Molnar allow granularity up to 100 msecs, instead of 10 msecs. (needed on larger boxes) Signed-off-by: Ingo Molnar --- kernel/sched.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) Index: linux/kernel/sched.c =================================================================== --- linux.orig/kernel/sched.c +++ linux/kernel/sched.c @@ -4772,7 +4772,7 @@ cpumask_t nohz_cpu_mask = CPU_MASK_NONE; static inline void sched_init_granularity(void) { unsigned int factor = 1 + ilog2(num_online_cpus()); - const unsigned long gran_limit = 10000000; + const unsigned long gran_limit = 100000000; sysctl_sched_granularity *= factor; if (sysctl_sched_granularity > gran_limit)