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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2C375C0015E for ; Thu, 13 Jul 2023 23:28:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234016AbjGMX2P (ORCPT ); Thu, 13 Jul 2023 19:28:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58234 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231303AbjGMX2O (ORCPT ); Thu, 13 Jul 2023 19:28:14 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3AF1426B3 for ; Thu, 13 Jul 2023 16:27:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1689290846; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=MMEnf8rXxOUbhCoMjSDXkxxMaYDWouwwWK2L8mM+xTY=; b=PcjdwTIk15zmrkA0wf2cmB/fmJIK0+ZJ/NupIjP3Vt/hM37FcLiYGNbdyQFKh1ZB+paFSv 8IWdOm+WN7woPSDA2SFazLqbiuT+uu5x1ZBZM/hTY9WEd67A/KiRGAcpi/dlPORPbNib24 oMmLcc304zRJ2TDsMdiBbsWuy2fg9GY= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-573-D7yz2JQ4MiSjr_yOG0uqWw-1; Thu, 13 Jul 2023 19:27:23 -0400 X-MC-Unique: D7yz2JQ4MiSjr_yOG0uqWw-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 88C47800B35; Thu, 13 Jul 2023 23:27:22 +0000 (UTC) Received: from lorien.usersys.redhat.com (unknown [10.22.34.106]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E02EA492B01; Thu, 13 Jul 2023 23:27:21 +0000 (UTC) Date: Thu, 13 Jul 2023 19:27:19 -0400 From: Phil Auld To: Benjamin Segall Cc: linux-kernel@vger.kernel.org, Juri Lelli , Ingo Molnar , Daniel Bristot de Oliveira , Peter Zijlstra , Vincent Guittot , Dietmar Eggemann , Valentin Schneider , Steven Rostedt , Mel Gorman , Frederic Weisbecker , Tejun Heo Subject: Re: [PATCH v2 1/2] sched, cgroup: Restore meaning to hierarchical_quota Message-ID: <20230713232719.GA32912@lorien.usersys.redhat.com> References: <20230712133357.381137-1-pauld@redhat.com> <20230712133357.381137-2-pauld@redhat.com> <20230713132306.GA13342@lorien.usersys.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 13, 2023 at 01:12:04PM -0700 Benjamin Segall wrote: > Phil Auld writes: > > > On Wed, Jul 12, 2023 at 03:09:31PM -0700 Benjamin Segall wrote: > >> Phil Auld writes: > >> > >> > In cgroupv2 cfs_b->hierarchical_quota is set to -1 for all task > >> > groups due to the previous fix simply taking the min. It should > >> > reflect a limit imposed at that level or by an ancestor. Even > >> > though cgroupv2 does not require child quota to be less than or > >> > equal to that of its ancestors the task group will still be > >> > constrained by such a quota so this should be shown here. Cgroupv1 > >> > continues to set this correctly. > >> > > >> > In both cases, add initialization when a new task group is created > >> > based on the current parent's value (or RUNTIME_INF in the case of > >> > root_task_group). Otherwise, the field is wrong until a quota is > >> > changed after creation and __cfs_schedulable() is called. > >> > > >> > Fixes: c53593e5cb69 ("sched, cgroup: Don't reject lower cpu.max on ancestors") > >> > Signed-off-by: Phil Auld > >> > Reviewed-by: Ben Segall > >> > Cc: Ingo Molnar > >> > Cc: Peter Zijlstra > >> > Cc: Vincent Guittot > >> > Cc: Juri Lelli > >> > Cc: Dietmar Eggemann > >> > Cc: Valentin Schneider > >> > Cc: Ben Segall > >> > Cc: Frederic Weisbecker > >> > Cc: Tejun Heo > >> > --- > >> > > >> > v2: Improve comment about how setting hierarchical_quota correctly > >> > > >> > helps the scheduler. Remove extra parens. > >> > kernel/sched/core.c | 13 +++++++++---- > >> > kernel/sched/fair.c | 7 ++++--- > >> > kernel/sched/sched.h | 2 +- > >> > 3 files changed, 14 insertions(+), 8 deletions(-) > >> > > >> > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > >> > index a68d1276bab0..f80697a79baf 100644 > >> > --- a/kernel/sched/core.c > >> > +++ b/kernel/sched/core.c > >> > @@ -9904,7 +9904,7 @@ void __init sched_init(void) > >> > ptr += nr_cpu_ids * sizeof(void **); > >> > > >> > root_task_group.shares = ROOT_TASK_GROUP_LOAD; > >> > - init_cfs_bandwidth(&root_task_group.cfs_bandwidth); > >> > + init_cfs_bandwidth(&root_task_group.cfs_bandwidth, NULL); > >> > #endif /* CONFIG_FAIR_GROUP_SCHED */ > >> > #ifdef CONFIG_RT_GROUP_SCHED > >> > root_task_group.rt_se = (struct sched_rt_entity **)ptr; > >> > @@ -11038,11 +11038,16 @@ static int tg_cfs_schedulable_down(struct task_group *tg, void *data) > >> > > >> > /* > >> > * Ensure max(child_quota) <= parent_quota. On cgroup2, > >> > - * always take the min. On cgroup1, only inherit when no > >> > - * limit is set: > >> > + * always take the non-RUNTIME_INF min. On cgroup1, only > >> > + * inherit when no limit is set. In cgroup2 this is used > >> > + * by the scheduler to determine if a given CFS task has a > >> > + * bandwidth constraint at some higher level. > >> > */ > >> > >> It's still used for determining this on cgroup1 (and the cgroup1 code > >> still works for that), right? > >> > > > > It would, except that the enforcement of child quota <= parent quota > > means that cfs_rq->runtime_enabled will be set and we'll hit that first > > on cgroup1. So we don't really use it for this determination in > > cgroup1. > > cgroup1 tg_cfs_schedulable_down only constricts child quota when it's > set. You can set quota=RUNTIME_INF on any cgroup, no matter what its > parent is. (The schedulable constraint is a little silly) > Aargh :) I had "In both cases this ..." there before I talked myself out of it. I'll update this one. Cheers, Phil --