Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965046AbaFSUur (ORCPT ); Thu, 19 Jun 2014 16:50:47 -0400 Received: from mga03.intel.com ([143.182.124.21]:11721 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754837AbaFSUuq (ORCPT ); Thu, 19 Jun 2014 16:50:46 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.01,508,1400050800"; d="scan'208";a="447687141" Date: Thu, 19 Jun 2014 13:50:44 -0700 From: Andi Kleen To: "Paul E. McKenney" Cc: Christoph Lameter , Dave Hansen , LKML , Josh Triplett , "Chen, Tim C" Subject: Re: [bisected] pre-3.16 regression on open() scalability Message-ID: <20140619205044.GX8178@tassilo.jf.intel.com> References: <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> <20140619180916.GE4904@linux.vnet.ibm.com> <20140619204220.GJ4904@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140619204220.GJ4904@linux.vnet.ibm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 19, 2014 at 01:42:20PM -0700, Paul E. McKenney wrote: > On Thu, Jun 19, 2014 at 03:31:56PM -0500, Christoph Lameter wrote: > > On Thu, 19 Jun 2014, Paul E. McKenney wrote: > > > > > That is a separate issue, but unnecessary calls to cond_resched() > > > should of course be removed -- no argument there. > > > > It looks like we are fighting higher latencies by adding calls in most of > > the critical sections which will in turn increase the latencies that we > > are trying to reduce. > > That is on battle in a larger war. Another battle is to keep big systems > from choking and dying. We need to win both battles, though I understand If we really need cond_resched() now to stop systems from dying we did a really poor job at designing Linux. I hope it's not true, that would be really bad and point to some severe design problems elsewhere. -Andi -- 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/