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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9482FC433F5 for ; Tue, 16 Nov 2021 23:48:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7D20661C15 for ; Tue, 16 Nov 2021 23:48:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232391AbhKPXvj (ORCPT ); Tue, 16 Nov 2021 18:51:39 -0500 Received: from mga07.intel.com ([134.134.136.100]:14843 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229791AbhKPXvi (ORCPT ); Tue, 16 Nov 2021 18:51:38 -0500 X-IronPort-AV: E=McAfee;i="6200,9189,10170"; a="297271832" X-IronPort-AV: E=Sophos;i="5.87,239,1631602800"; d="scan'208";a="297271832" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Nov 2021 15:48:40 -0800 X-IronPort-AV: E=Sophos;i="5.87,239,1631602800"; d="scan'208";a="506668644" Received: from schen9-mobl.amr.corp.intel.com ([10.209.94.155]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Nov 2021 15:48:40 -0800 Message-ID: <41d0d7cbd3e292eb89b12d27d9beb576be3531bf.camel@linux.intel.com> Subject: Re: [PATCH 0/2] avoid spurious blocked load update From: Tim Chen To: Vincent Guittot , mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, linux-kernel@vger.kernel.org Cc: joel@joelfernandes.org Date: Tue, 16 Nov 2021 15:48:40 -0800 In-Reply-To: <20211112095857.7016-1-vincent.guittot@linaro.org> References: <20211112095857.7016-1-vincent.guittot@linaro.org> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.34.4 (3.34.4-1.fc31) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2021-11-12 at 10:58 +0100, Vincent Guittot wrote: > This patchset is a follow up of : > https://lore.kernel.org/lkml/20211019123537.17146-1-vincent.guittot@linaro.org/ > > It ensures that newly idle load balance will not kick the update of > blocked load if it skips the load balance because avg_idle is too > short. > It also makes sure that rq->next_balance doesn't go in the past when > updated. > > Tim Chen (1): > sched: sched: Fix rq->next_balance time updated to earlier than > current time > > Vincent Guittot (1): > sched/fair: skip newidle update stats > > kernel/sched/fair.c | 25 ++++++++++++++++++++----- > 1 file changed, 20 insertions(+), 5 deletions(-) > Vincent, Got some data back from the benchmark team. To my surprise, the skip_new_idle_update_stats patch actually makes things a little worse. Relative Performance (higher better) 5.15 rc4 vanilla (cgroup disabled) 100% 5.15 rc4 vanilla (cgroup enabled) 96% patch v2 96% patch v3 96% patch v3 +skip_new_idle_update_stats 93.7% patch v3 +skip_new_idle_update_stats +Fix rq->next_balance_time 93.7% The cpu utilization actually is the similar compared with having just the v3 patch. In both cases they are 81% user 12% kernel 2% idle 5% waiting for IO Profile on key functions in load balancing shows a little more cpu utilization, which is unexpected as we are cutting short the newidle_balance. patch v3 0.56% [k] __update_load_avg_cfs_rq 0.51% [k] update_load_avg 0.39% [k] update_blocked_averages 0.36% [k] __update_load_avg_se 0.05% [k] newidle_balance patch v3 + skip_new_idle_update_stats 0.58% [k] __update_load_avg_cfs_rq 0.53% [k] update_load_avg 0.40% [k] update_blocked_averages 0.37% [k] __update_load_avg_se 0.06% [k] newidle_balance Context switch frequency is lower by 4% with the skip_new_idle_update_stats patch. Thanks. Tim