From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752473AbdDEBuS (ORCPT ); Tue, 4 Apr 2017 21:50:18 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:46750 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751018AbdDEBuR (ORCPT ); Tue, 4 Apr 2017 21:50:17 -0400 Date: Wed, 5 Apr 2017 07:20:06 +0530 From: Srikar Dronamraju To: Mel Gorman Cc: Ingo Molnar , Peter Zijlstra , LKML , Rik van Riel Subject: Re: [PATCH] sched: Fix numabalancing to work with isolated cpus Reply-To: Srikar Dronamraju References: <1491326848-5748-1-git-send-email-srikar@linux.vnet.ibm.com> <20170404203714.c4mexerfq3ztanpm@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20170404203714.c4mexerfq3ztanpm@techsingularity.net> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable x-cbid: 17040501-0012-0000-0000-000003DC3F18 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17040501-0013-0000-0000-00001B624C23 Message-Id: <20170405015006.GA4941@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-04-05_01:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1702020001 definitions=main-1704050014 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > > > To avoid this, please check for isolated cpus before choosing a target > > cpu. > > > > Hmm, would this also prevent a task running inside a cgroup that is > allowed accessed to isolated CPUs from balancing? I severely doubt it Scheduler doesn't do any kind of load balancing for isolated cpus. # grep -o "isolcpus=.*" /proc/cmdline isolcpus=56,64,72,80,88 # taskset -c "56,64,72,80" ebizzy -S 100 -t 44 (on another terminal) # pgrep ebizzy 10437 # cat /proc/10437/status |grep Cpus_allowed_list Cpus_allowed_list: 56,64,72,80 # But the all the tasks would only run on cpu 56, even if its fully overloaded. Cpus 64,72,80 would be completely idle. So on isolated cpus, its the user who is in full control of scheduling the tasks on the cpu. > matters because if a process is isolated from interference then it > follows that automatic NUMA balancing should not be involved. If Yes, as an extension of the above, numa balancing should not be involved. > anything the protection should be absolute but either way; > > Acked-by: Mel Gorman > Thanks.