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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 279D1C2BA2B for ; Thu, 16 Apr 2020 20:55:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 00310206D5 for ; Thu, 16 Apr 2020 20:54:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728570AbgDPUy7 (ORCPT ); Thu, 16 Apr 2020 16:54:59 -0400 Received: from foss.arm.com ([217.140.110.172]:41368 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727952AbgDPUy6 (ORCPT ); Thu, 16 Apr 2020 16:54:58 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 16C7F30E; Thu, 16 Apr 2020 13:54:58 -0700 (PDT) Received: from e113632-lin (e113632-lin.cambridge.arm.com [10.1.194.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 4B9BE3F237; Thu, 16 Apr 2020 13:54:57 -0700 (PDT) References: <20200415210512.805-1-valentin.schneider@arm.com> <20200415210512.805-10-valentin.schneider@arm.com> User-agent: mu4e 0.9.17; emacs 26.3 From: Valentin Schneider To: Vincent Guittot Cc: Dietmar Eggemann , linux-kernel , Ingo Molnar , Peter Zijlstra Subject: Re: [PATCH v3 9/9] sched/topology: Define and use shortcut pointers for wakeup sd_flag scan In-reply-to: Date: Thu, 16 Apr 2020 21:54:52 +0100 Message-ID: MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 16/04/20 16:58, Vincent Guittot wrote: >> --- >> if (wake_flags & WF_TTWU) { >> if (want_affine) { >> // We can cache that at topology buildup >> sd = highest_flag_domain(cpu, SD_WAKE_AFFINE); >> >> if (cpumask_test_cpu(prev_cpu, sched_domain_span(sd) && >> cpu != prev_cpu) >> new_cpu = wake_affine(); >> >> } >> // Directly go to select_idle_sibling() >> goto sis; >> } >> >> // !want_affine logic here >> --- >> >> This in turns mean we could get rid of SD_BALANCE_WAKE entirely... I'm a >> bit more reluctant to that only because the last SD_BALANCE_WAKE setter was > > For now, we should probably skip the additional test above: "if > (wake_flags & WF_TTWU) {" and keep SD_BALANCE_WAKE so we will continue > to loop in case of !want_affine. > > We can imagine that we might want at the end to be a bit more smart > for SD_BALANCE_WAKE and the slow path... like with the latency nice > proposal and latency-nice=19 as a example > Good point. I'll go for the first option and see where I end up; I'd like to cache the other domain pointers if possible, I'll do some benchmarking and see if I can do that without another switch case. >> removed fairly recently, see >> a526d466798d ("sched/topology: Remove SD_BALANCE_WAKE on asymmetric capacity systems")