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=-9.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS 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 8A094C4363A for ; Tue, 27 Oct 2020 10:47:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2BEAF22384 for ; Tue, 27 Oct 2020 10:47:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1418648AbgJ0Kry (ORCPT ); Tue, 27 Oct 2020 06:47:54 -0400 Received: from foss.arm.com ([217.140.110.172]:38104 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1418632AbgJ0KrU (ORCPT ); Tue, 27 Oct 2020 06:47:20 -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 EA5F730E; Tue, 27 Oct 2020 03:47:19 -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 7D1C63F66E; Tue, 27 Oct 2020 03:47:18 -0700 (PDT) References: <1603769572-8193-1-git-send-email-xuewen.yan94@gmail.com> <69257e98-2d93-673a-5dac-e11b6d5610be@arm.com> User-agent: mu4e 0.9.17; emacs 26.3 From: Valentin Schneider To: Dietmar Eggemann Cc: Xuewen Yan , xuewen.yan@unisoc.com, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] sched: sched_domain fix highest_flag_domain function In-reply-to: <69257e98-2d93-673a-5dac-e11b6d5610be@arm.com> Date: Tue, 27 Oct 2020 10:47:13 +0000 Message-ID: MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 27/10/20 09:57, Dietmar Eggemann wrote: > On 27/10/2020 04:32, Xuewen Yan wrote: >> the highest_flag_domain is to search the highest sched_domain >> containing flag, but if the lower sched_domain didn't contain >> the flag, but the higher sched_domain contains the flag, the >> function will return NULL instead of the higher sched_domain. >> >> For example: >> In MC domain : no SD_ASYM_CPUCAPACITY flag; >> In DIE domain : containing SD_ASYM_CPUCAPACITY flag; >> the "highest_flag_domain(cpu, SD_ASYM_CPUCAPACITY)" will return NULL. >> >> Signed-off-by: Xuewen Yan >> --- >> kernel/sched/sched.h | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h >> index 28709f6..2c7c566 100644 >> --- a/kernel/sched/sched.h >> +++ b/kernel/sched/sched.h >> @@ -1427,7 +1427,7 @@ static inline struct sched_domain *highest_flag_domain(int cpu, int flag) >> >> for_each_domain(cpu, sd) { >> if (!(sd->flags & flag)) >> - break; >> + continue; >> hsd = sd; >> } > > We distinguish between SDF_SHARED_PARENT and SDF_SHARED_CHILD SD flags. > > 1 SD_FLAG(*SD_ASYM_CPUCAPACITY*, SDF_SHARED_PARENT | SDF_NEEDS_GROUPS) > 2 SD_FLAG(SD_SERIALIZE, SDF_SHARED_PARENT | SDF_NEEDS_GROUPS) > 3 SD_FLAG(SD_OVERLAP, SDF_SHARED_PARENT | SDF_NEEDS_GROUPS) > 4 SD_FLAG(SD_NUMA, SDF_SHARED_PARENT | SDF_NEEDS_GROUPS) > > 1 SD_FLAG(SD_BALANCE_NEWIDLE, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS) > 2 SD_FLAG(SD_BALANCE_EXEC, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS) > 3 SD_FLAG(SD_BALANCE_FORK, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS) > 4 SD_FLAG(SD_BALANCE_WAKE, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS) > 5 82 SD_FLAG(SD_WAKE_AFFINE, SDF_SHARED_CHILD) > 6 SD_FLAG(SD_SHARE_CPUCAPACITY, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS) > 7 SD_FLAG(SD_SHARE_PKG_RESOURCES, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS) > 8 SD_FLAG(SD_ASYM_PACKING, SDF_SHARED_CHILD | SDF_NEEDS_GROUPS) > > We call lowest_flag_domain() on SDF_SHARED_PARENT and > highest_flag_domain() on SDF_SHARED_CHILD SD flags. > > 1 sd = lowest_flag_domain(cpu, SD_NUMA); > 2 sd = lowest_flag_domain(cpu, *SD_ASYM_CPUCAPACITY*); > > 1 sd = highest_flag_domain(cpu, SD_SHARE_PKG_RESOURCES); > 2 sd = highest_flag_domain(cpu, SD_ASYM_PACKING); Spot on! In some of my earliest instrumentation patches I had a SCHED_WARN_ON() for when highest_flag_domain() is passed an SDF_SHARED_PARENT flag (for some reason I don't have the equivalent for lowest_flag_domain() in that branch). I had ditched that as it didn't seem that useful, but perhaps that wasn't so accurate :)