Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756635AbaFWRe3 (ORCPT ); Mon, 23 Jun 2014 13:34:29 -0400 Received: from mga09.intel.com ([134.134.136.24]:26933 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756157AbaFWRe1 (ORCPT ); Mon, 23 Jun 2014 13:34:27 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.01,531,1400050800"; d="scan'208";a="561998520" Message-ID: <53A8651B.4010607@intel.com> Date: Mon, 23 Jun 2014 10:34:19 -0700 From: Dave Hansen User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: paulmck@linux.vnet.ibm.com CC: linux-kernel@vger.kernel.org, mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, ak@linux.intel.com, cl@gentwo.org, umgwanakikbuti@gmail.com Subject: Re: [PATCH tip/core/rcu] Reduce overhead of cond_resched() checks for RCU References: <20140621025958.GA7185@linux.vnet.ibm.com> <53A85BF9.7030006@intel.com> <20140623171644.GH4603@linux.vnet.ibm.com> In-Reply-To: <20140623171644.GH4603@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/23/2014 10:16 AM, Paul E. McKenney wrote: > On Mon, Jun 23, 2014 at 09:55:21AM -0700, Dave Hansen wrote: >> This still has a regression. Commit 1ed70de (from Paul's git tree), >> gets a result of 52231880. If I back up two commits to v3.16-rc1 and >> revert ac1bea85 (the original culprit) the result goes back up to 57308512. >> >> So something is still going on here. > > And commit 1ed70de is in fact the right one, so... > > The rcutree.jiffies_till_sched_qs boot/sysfs parameter controls how > long RCU waits before asking for quiescent states. The default is > currently HZ/20. Does increasing this parameter help? Easy for me to > increase the default if it does. Making it an insane value: echo 12 > /sys/module/rcutree/parameters/jiffies_till_sched_qs average:52248706 echo 9999999 > /sys/module/rcutree/parameters/jiffies_till_sched_qs average:55712533 gets us back up _closer_ to our original 57M number, but it's still not quite there. -- 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/