From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752652AbbAUJtL (ORCPT ); Wed, 21 Jan 2015 04:49:11 -0500 Received: from e39.co.us.ibm.com ([32.97.110.160]:50118 "EHLO e39.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751546AbbAUJtF (ORCPT ); Wed, 21 Jan 2015 04:49:05 -0500 Date: Wed, 21 Jan 2015 00:54:32 -0800 From: "Paul E. McKenney" To: Mike Galbraith Cc: Huang Ying , LKML , LKP ML Subject: Re: [LKP] [rcu] 00f5159aeb6: +55.3% will-it-scale.time.involuntary_context_switches Message-ID: <20150121085432.GD9719@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1421825564.6126.29.camel@intel.com> <20150121075254.GC9719@linux.vnet.ibm.com> <1421827607.5772.19.camel@marge.simpson.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1421827607.5772.19.camel@marge.simpson.net> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15012109-0033-0000-0000-00000366BB21 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 21, 2015 at 09:06:47AM +0100, Mike Galbraith wrote: > On Tue, 2015-01-20 at 23:52 -0800, Paul E. McKenney wrote: > > On Wed, Jan 21, 2015 at 03:32:44PM +0800, Huang Ying wrote: > > > FYI, we noticed the below changes on > > > > > > git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git stall.2015.01.06a > > > commit 00f5159aeb68f08ce29597be86be87d6db0c1ba1 ("rcu: Run grace-period kthreads at real-time priority") > > > > Glad this helps! > > The way I read it, it's hurting by increasing context switches... but if > you'll need a boot param to turn it on in the future, this is moot :) Heh! I guess I should read it more carefully. Anyway, the commit does help in some heavy-load situations, but something more deft is clearly required if it is to be enabled more generally. Thanx, Paul