From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751255AbeDXWqV (ORCPT ); Tue, 24 Apr 2018 18:46:21 -0400 Received: from aserp2120.oracle.com ([141.146.126.78]:34008 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750995AbeDXWqS (ORCPT ); Tue, 24 Apr 2018 18:46:18 -0400 Subject: Re: [PATCH 3/3] sched: limit cpu search and rotate search window for scalability To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, daniel.lezcano@linaro.org, steven.sistare@oracle.com, dhaval.giani@oracle.com, rohit.k.jain@oracle.com References: <20180424004116.28151-1-subhra.mazumdar@oracle.com> <20180424004116.28151-4-subhra.mazumdar@oracle.com> <20180424124855.GT4082@hirez.programming.kicks-ass.net> From: Subhra Mazumdar Message-ID: Date: Tue, 24 Apr 2018 15:48:41 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180424124855.GT4082@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8873 signatures=668698 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=625 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1804240214 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/24/2018 05:48 AM, Peter Zijlstra wrote: > On Mon, Apr 23, 2018 at 05:41:16PM -0700, subhra mazumdar wrote: >> Lower the lower limit of idle cpu search in select_idle_cpu() and also put >> an upper limit. This helps in scalability of the search by restricting the >> search window. Also rotating the search window with help of next_cpu >> ensures any idle cpu is eventually found in case of high load. > So this patch does 2 (possibly 3) things, that's not good. During testing I did try with first only restricting the search window. That alone wasn't enough to give the full benefit, rotating search window was essential to get best results. I will break this up in next version.