From patchwork Mon Jul 12 06:05:43 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg Kroah-Hartman X-Patchwork-Id: 475816 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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT 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 33ADAC11F86 for ; Mon, 12 Jul 2021 07:09:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 167B4610FA for ; Mon, 12 Jul 2021 07:09:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245350AbhGLHMA (ORCPT ); Mon, 12 Jul 2021 03:12:00 -0400 Received: from mail.kernel.org ([198.145.29.99]:42086 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244159AbhGLHK2 (ORCPT ); Mon, 12 Jul 2021 03:10:28 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 591DB613CA; Mon, 12 Jul 2021 07:06:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626073602; bh=euOi7siJ/ayk1/8dY5MN8MN8sdkfhzc8bSkdEUPYp+k=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eB0rS2HejCaOAOJx/q76U/j5mroP0fHAiG6lhahqs5Df2WksKjmAqOIcvM82nuTJJ X517toxX3IFQ5D/YbfgXrpGI+5FiJQpFQtemPVzFQeF651ADMyzWhKfhewDRfJuWqO B0xEVsclDel5He+Y9v0wYa/dFceT6LEDZOlkYWcE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Qais Yousef , "Peter Zijlstra (Intel)" , Sasha Levin Subject: [PATCH 5.12 260/700] sched/uclamp: Fix wrong implementation of cpu.uclamp.min Date: Mon, 12 Jul 2021 08:05:43 +0200 Message-Id: <20210712061003.805408556@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210712060924.797321836@linuxfoundation.org> References: <20210712060924.797321836@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Qais Yousef [ Upstream commit 0c18f2ecfcc274a4bcc1d122f79ebd4001c3b445 ] cpu.uclamp.min is a protection as described in cgroup-v2 Resource Distribution Model Documentation/admin-guide/cgroup-v2.rst which means we try our best to preserve the minimum performance point of tasks in this group. See full description of cpu.uclamp.min in the cgroup-v2.rst. But the current implementation makes it a limit, which is not what was intended. For example: tg->cpu.uclamp.min = 20% p0->uclamp[UCLAMP_MIN] = 0 p1->uclamp[UCLAMP_MIN] = 50% Previous Behavior (limit): p0->effective_uclamp = 0 p1->effective_uclamp = 20% New Behavior (Protection): p0->effective_uclamp = 20% p1->effective_uclamp = 50% Which is inline with how protections should work. With this change the cgroup and per-task behaviors are the same, as expected. Additionally, we remove the confusing relationship between cgroup and !user_defined flag. We don't want for example RT tasks that are boosted by default to max to change their boost value when they attach to a cgroup. If a cgroup wants to limit the max performance point of tasks attached to it, then cpu.uclamp.max must be set accordingly. Or if they want to set different boost value based on cgroup, then sysctl_sched_util_clamp_min_rt_default must be used to NOT boost to max and set the right cpu.uclamp.min for each group to let the RT tasks obtain the desired boost value when attached to that group. As it stands the dependency on !user_defined flag adds an extra layer of complexity that is not required now cpu.uclamp.min behaves properly as a protection. The propagation model of effective cpu.uclamp.min in child cgroups as implemented by cpu_util_update_eff() is still correct. The parent protection sets an upper limit of what the child cgroups will effectively get. Fixes: 3eac870a3247 (sched/uclamp: Use TG's clamps to restrict TASK's clamps) Signed-off-by: Qais Yousef Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20210510145032.1934078-2-qais.yousef@arm.com Signed-off-by: Sasha Levin --- kernel/sched/core.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 17f612045271..3fe7daf9d31d 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1057,7 +1057,6 @@ uclamp_tg_restrict(struct task_struct *p, enum uclamp_id clamp_id) { struct uclamp_se uc_req = p->uclamp_req[clamp_id]; #ifdef CONFIG_UCLAMP_TASK_GROUP - struct uclamp_se uc_max; /* * Tasks in autogroups or root task group will be @@ -1068,9 +1067,23 @@ uclamp_tg_restrict(struct task_struct *p, enum uclamp_id clamp_id) if (task_group(p) == &root_task_group) return uc_req; - uc_max = task_group(p)->uclamp[clamp_id]; - if (uc_req.value > uc_max.value || !uc_req.user_defined) - return uc_max; + switch (clamp_id) { + case UCLAMP_MIN: { + struct uclamp_se uc_min = task_group(p)->uclamp[clamp_id]; + if (uc_req.value < uc_min.value) + return uc_min; + break; + } + case UCLAMP_MAX: { + struct uclamp_se uc_max = task_group(p)->uclamp[clamp_id]; + if (uc_req.value > uc_max.value) + return uc_max; + break; + } + default: + WARN_ON_ONCE(1); + break; + } #endif return uc_req;