From nobody Sat Apr 11 23:02:53 2026 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 5112DC19F2A for ; Thu, 4 Aug 2022 14:37:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239467AbiHDOhb (ORCPT ); Thu, 4 Aug 2022 10:37:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49736 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239988AbiHDOhC (ORCPT ); Thu, 4 Aug 2022 10:37:02 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id C7CCD52475 for ; Thu, 4 Aug 2022 07:36:57 -0700 (PDT) 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 3F16C1480; Thu, 4 Aug 2022 07:36:58 -0700 (PDT) Received: from localhost.localdomain (unknown [10.57.10.177]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 142293F73B; Thu, 4 Aug 2022 07:36:55 -0700 (PDT) From: Qais Yousef To: Ingo Molnar , "Peter Zijlstra (Intel)" , Vincent Guittot , Dietmar Eggemann Cc: linux-kernel@vger.kernel.org, Xuewen Yan , Lukasz Luba , Wei Wang , Jonathan JMChen , Hank , Qais Yousef Subject: [PATCH v2 9/9] sched/fair: Consider capacity inversion in util_fits_cpu() Date: Thu, 4 Aug 2022 15:36:09 +0100 Message-Id: <20220804143609.515789-10-qais.yousef@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220804143609.515789-1-qais.yousef@arm.com> References: <20220804143609.515789-1-qais.yousef@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" We do consider thermal pressure in util_fits_cpu() for uclamp_min only. With the exception of the biggest cores which by definition are the max performance point of the system and all tasks by definition should fit. Even under thermal pressure, the capacity of the biggest CPU is the highest in the system and should still fit every task. Except when it reaches capacity inversion point, then this is no longer true. We can handle this by using the inverted capacity as capacity_orig in util_fits_cpu(). Which not only addresses the problem above, but also ensure uclamp_max now considers the inverted capacity. Force fitting a task when a CPU is in this adverse state will contribute to making the thermal throttling last longer. Signed-off-by: Qais Yousef --- kernel/sched/fair.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index cb32dc9a057f..77ae343e32a3 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4293,12 +4293,16 @@ static inline int util_fits_cpu(unsigned long util, * For uclamp_max, we can tolerate a drop in performance level as the * goal is to cap the task. So it's okay if it's getting less. * - * In case of capacity inversion, which is not handled yet, we should - * honour the inverted capacity for both uclamp_min and uclamp_max all - * the time. + * In case of capacity inversion we should honour the inverted capacity + * for both uclamp_min and uclamp_max all the time. */ - capacity_orig =3D capacity_orig_of(cpu); - capacity_orig_thermal =3D capacity_orig - arch_scale_thermal_pressure(cpu= ); + capacity_orig =3D cpu_in_capacity_inversion(cpu); + if (capacity_orig) { + capacity_orig_thermal =3D capacity_orig; + } else { + capacity_orig =3D capacity_orig_of(cpu); + capacity_orig_thermal =3D capacity_orig - arch_scale_thermal_pressure(cp= u); + } =20 /* * We want to force a task to fit a cpu as implied by uclamp_max. --=20 2.25.1