From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754095Ab1I1OTw (ORCPT ); Wed, 28 Sep 2011 10:19:52 -0400 Received: from e6.ny.us.ibm.com ([32.97.182.146]:47015 "EHLO e6.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752322Ab1I1OTv (ORCPT ); Wed, 28 Sep 2011 10:19:51 -0400 Date: Wed, 28 Sep 2011 19:47:01 +0530 From: Srivatsa Vaddagiri To: Venki Pallipadi Cc: Peter Zijlstra , Paul Turner , Ingo Molnar , Vaidyanathan Srinivasan , Kamalesh Babulal , linux-kernel@vger.kernel.org Subject: Re: [PATCH v1] sched: fix nohz idle load balancer issues Message-ID: <20110928141701.GF8593@linux.vnet.ibm.com> Reply-To: Srivatsa Vaddagiri References: <20110926115049.GA22604@linux.vnet.ibm.com> <20110928043427.GI4357@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20110928043427.GI4357@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Srivatsa Vaddagiri [2011-09-28 10:04:27]: > > Especially with higher number of logical CPUs. Likely cleaner way is to clear > > first_pick, second_pick on idle instead of clearing on tickless. > > I think I tried that (cleared first/second_pick_cpu in > nohz_kick_needed() upon idle) but didn't get the best results. Let me > try that again and post idle time numbers. So made some changes so that first/second_pick_cpu identifiers are cleared when corresponding cpus become idle. They are cleared in pick_next_task_idle() .. With that change, I don't see additional benefit of having a third busy cpu kick ilb_cpu when it has > 1 task. Idle time -> Avg. Std.Dev Min Max W/o third busy cpu kicking 4.57% 0.9 3% 8% With third busy cpu kicking 4.78% 1.1% 3% 8% So will go with your suggestion in the next version! - vatsa