From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 88126C433DB for ; Mon, 1 Feb 2021 13:07:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4441564DDD for ; Mon, 1 Feb 2021 13:07:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231854AbhBANHV (ORCPT ); Mon, 1 Feb 2021 08:07:21 -0500 Received: from outbound-smtp15.blacknight.com ([46.22.139.232]:50133 "EHLO outbound-smtp15.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231873AbhBANHD (ORCPT ); Mon, 1 Feb 2021 08:07:03 -0500 Received: from mail.blacknight.com (pemlinmail03.blacknight.ie [81.17.254.16]) by outbound-smtp15.blacknight.com (Postfix) with ESMTPS id 0F44A1C4C90 for ; Mon, 1 Feb 2021 13:06:05 +0000 (GMT) Received: (qmail 23314 invoked from network); 1 Feb 2021 13:06:04 -0000 Received: from unknown (HELO techsingularity.net) (mgorman@techsingularity.net@[84.203.22.4]) by 81.17.254.9 with ESMTPSA (AES256-SHA encrypted, authenticated); 1 Feb 2021 13:06:04 -0000 Date: Mon, 1 Feb 2021 13:06:03 +0000 From: Mel Gorman To: "Li, Aubrey" Cc: Peter Zijlstra , Ingo Molnar , Vincent Guittot , Qais Yousef , LKML Subject: Re: [PATCH v5 0/4] Scan for an idle sibling in a single pass Message-ID: <20210201130603.GI3592@techsingularity.net> References: <20210127135203.19633-1-mgorman@techsingularity.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 01, 2021 at 09:13:16AM +0800, Li, Aubrey wrote: > > Peter's series tried to solve three problems at once, this subset addresses > > one problem. > > > > kernel/sched/fair.c | 151 +++++++++++++++++++--------------------- > > kernel/sched/features.h | 1 - > > 2 files changed, 70 insertions(+), 82 deletions(-) > > > > 4 benchmarks measured on a x86 4s system with 24 cores per socket and > 2 HTs per core, total 192 CPUs. > > The load level is [25%, 50%, 75%, 100%]. > > - hackbench almost has a universal win. > - netperf high load has notable changes, as well as tbench 50% load. > Ok, both netperf and tbench are somewhat expected as at those loads are rapidly idling. Previously I observed that rapidly idling loads can allow the has_idle_cores test pass for short durations and the double scanning means there is a greater chance of finding an idle CPU over the two passes. I think overall it's better to avoid double scanning even if there are counter examples as it's possible we'll get that back through better depth selection in the future. Thanks. -- Mel Gorman SUSE Labs