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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, 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 04524C48BD1 for ; Fri, 11 Jun 2021 16:43:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E2C1C61357 for ; Fri, 11 Jun 2021 16:43:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230188AbhFKQpg (ORCPT ); Fri, 11 Jun 2021 12:45:36 -0400 Received: from foss.arm.com ([217.140.110.172]:34888 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229517AbhFKQp2 (ORCPT ); Fri, 11 Jun 2021 12:45:28 -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 3B7F9D6E; Fri, 11 Jun 2021 09:43:30 -0700 (PDT) Received: from [192.168.178.6] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D3A2F3F719; Fri, 11 Jun 2021 09:43:27 -0700 (PDT) Subject: Re: [PATCH] sched: cgroup SCHED_IDLE support To: Josh Don Cc: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Paul Turner , David Rientjes , Oleg Rombakh , Viresh Kumar , Steve Sistare , Tejun Heo , linux-kernel@vger.kernel.org References: <20210608231132.32012-1-joshdon@google.com> From: Dietmar Eggemann Message-ID: <7222c20a-5cbb-d443-a2fd-19067652a38e@arm.com> Date: Fri, 11 Jun 2021 18:43:04 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/06/2021 21:14, Josh Don wrote: > Hey Dietmar, > > On Thu, Jun 10, 2021 at 5:53 AM Dietmar Eggemann > wrote: >> >> Any reason why this should only work on cgroup-v2? > > My (perhaps incorrect) assumption that new development should not > extend v1. I'd actually prefer making this work on v1 as well; I'll > add that support. > >> struct cftype cpu_legacy_files[] vs. cpu_files[] >> >> [...] >> >>> @@ -11340,10 +11408,14 @@ void init_tg_cfs_entry(struct task_group *tg, struct cfs_rq *cfs_rq, >>> >>> static DEFINE_MUTEX(shares_mutex); >>> >>> -int sched_group_set_shares(struct task_group *tg, unsigned long shares) >>> +#define IDLE_WEIGHT sched_prio_to_weight[ARRAY_SIZE(sched_prio_to_weight) - 1] >> >> Why not 3 ? Like for tasks (WEIGHT_IDLEPRIO)? >> >> [...] > > Went back and forth on this; on second look, I do think it makes sense > to use the IDLEPRIO weight of 3 here. This gets converted to a 0, > rather than a 1 for display of cpu.weight, which is also actually a > nice property. I'm struggling to see the benefit here. For a taskgroup A: Why setting A/cpu.idle=1 to force a minimum A->shares when you can set it directly via A/cpu.weight (to 1 (minimum))? WEIGHT cpu.weight tg->shares 3 0 3072 15 1 15360 1 10240 `A/cpu.weight` follows cgroup-v2's `weights` `resource distribution model`* but I can only see `A/cpu.idle` as a layer on top of it forcing `A/cpu.weight` to get its minimum value? *Documentation/admin-guide/cgroup-v2.rst