Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934216AbaFSSJm (ORCPT ); Thu, 19 Jun 2014 14:09:42 -0400 Received: from e33.co.us.ibm.com ([32.97.110.151]:41513 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933531AbaFSSJk (ORCPT ); Thu, 19 Jun 2014 14:09:40 -0400 Date: Thu, 19 Jun 2014 11:09:16 -0700 From: "Paul E. McKenney" To: Christoph Lameter Cc: Andi Kleen , Dave Hansen , LKML , Josh Triplett , "Chen, Tim C" Subject: Re: [bisected] pre-3.16 regression on open() scalability Message-ID: <20140619180916.GE4904@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20140613224519.GV4581@linux.vnet.ibm.com> <53A0CAE5.9000702@intel.com> <20140618001836.GV4669@linux.vnet.ibm.com> <53A132D4.60408@intel.com> <20140618125831.GB4669@linux.vnet.ibm.com> <53A1CE19.7040103@intel.com> <20140618203052.GT4669@linux.vnet.ibm.com> <20140618235131.GA25946@linux.vnet.ibm.com> <20140619014200.GO8178@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14061918-0928-0000-0000-000002C46C25 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 19, 2014 at 09:42:18AM -0500, Christoph Lameter wrote: > On Wed, 18 Jun 2014, Andi Kleen wrote: > > > I still think it's totally the wrong direction to pollute so > > many fast paths with this obscure debugging check workaround > > unconditionally. > > > > cond_resched() is in EVERY sleeping lock and in EVERY memory allocation! > > And these are really critical paths for many workloads. > > > > If you really wanted to do this I think you would first need > > to define a cond_resched_i_am_not_fast() or somesuch. > > > > Or put it all behind some debugging ifdef. > > Again I am fully on Andi's side here. Please remove these frequent calls > to cond_resched. If one wants a fully preemptable kernel then please use > CONFIG_PREEMPT. That is a separate issue, but unnecessary calls to cond_resched() should of course be removed -- no argument there. Thanx, Paul -- 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/