From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752979AbbC0HBz (ORCPT ); Fri, 27 Mar 2015 03:01:55 -0400 Received: from mga09.intel.com ([134.134.136.24]:63874 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751579AbbC0HBv (ORCPT ); Fri, 27 Mar 2015 03:01:51 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.11,477,1422950400"; d="scan'208";a="686430290" Date: Fri, 27 Mar 2015 14:43:31 +0800 From: Wanpeng Li To: Jason Low Cc: Preeti U Murthy , peterz@infradead.org, mingo@kernel.org, riel@redhat.com, daniel.lezcano@linaro.org, vincent.guittot@linaro.org, srikar@linux.vnet.ibm.com, pjt@google.com, benh@kernel.crashing.org, efault@gmx.de, linux-kernel@vger.kernel.org, iamjoonsoo.kim@lge.com, svaidy@linux.vnet.ibm.com, tim.c.chen@linux.intel.com, morten.rasmussen@arm.com, Wanpeng Li Subject: Re: [PATCH V2] sched: Improve load balancing in the presence of idle CPUs Message-ID: <20150327064331.GA5419@kernel> Reply-To: Wanpeng Li References: <20150326130014.21532.17158.stgit@preeti.in.ibm.com> <20150327021201.GA4491@kernel> <1427432841.2788.10.camel@j-VirtualBox> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1427432841.2788.10.camel@j-VirtualBox> 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 On Thu, Mar 26, 2015 at 10:07:21PM -0700, Jason Low wrote: >On Fri, 2015-03-27 at 10:12 +0800, Wanpeng Li wrote: >> Hi Preeti, >> On Thu, Mar 26, 2015 at 06:32:44PM +0530, Preeti U Murthy wrote: >> > >> >1. An ILB CPU was chosen from the first numa domain to trigger nohz idle >> >load balancing [Given the experiment, upto 6 CPUs per core could be >> >potentially idle in this domain.] >> > >> >2. However the ILB CPU would call load_balance() on itself before >> >initiating nohz idle load balancing. >> > >> >3. Given cores are SMT8, the ILB CPU had enough opportunities to pull >> >tasks from its sibling cores to even out load. >> > >> >4. Now that the ILB CPU was no longer idle, it would abort nohz idle >> >load balancing >> >> I don't see abort nohz idle load balancing when ILB CPU was no longer idle >> in nohz_idle_balance(), could you explain more in details? > >Hi Wanpeng, > >In nohz_idle_balance(), there is a check for need_resched() so if the >cpu has something to run, it should exit nohz_idle_balance(), which may >cause it to not do the idle balancing on the other CPUs. Got it, thanks. ;) Regards, Wanpeng Li > >