From nobody Wed Dec 17 23:51:10 2025 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 3454AC77B73 for ; Sun, 16 Apr 2023 21:34:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229763AbjDPVeS (ORCPT ); Sun, 16 Apr 2023 17:34:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57640 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229458AbjDPVeP (ORCPT ); Sun, 16 Apr 2023 17:34:15 -0400 Received: from mail-yw1-x114a.google.com (mail-yw1-x114a.google.com [IPv6:2607:f8b0:4864:20::114a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5680F2113 for ; Sun, 16 Apr 2023 14:34:13 -0700 (PDT) Received: by mail-yw1-x114a.google.com with SMTP id 00721157ae682-552d922f0faso7865217b3.14 for ; Sun, 16 Apr 2023 14:34:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1681680852; x=1684272852; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=cP9JSIgzIwKlCqJpR4LA/JOVMTfnunGFo8i5nV2KCy4=; b=LAVowwSFzzEA0L+f0tMquJ92ekEc5sfLhZ9bBNxI7qWsRP7eKrMiUCBK69pdkwVPaK gDr2MHmCxALvq3RTf0hf+2lGikMDg3q6OC30WUUrOAyGnKbmUS3U9uBEqwgN2fRfLEi2 kutcf/cZ5P9ooCX9GdPt3RBNB6sCtXpXm7KNzxaQIEJ0sHZTRlj72Krr+LCC7uz5ql0B MZ4IyoYMChGStCfuLaqIS2/k4xZhV/EH3gpwd/ZU2fcr79qR1BBWd181mUJizmUvmkHC /PU6s+aI3mzGbgfhXq2yn/u/I5TP6R6qYXmFVHjGOmDkqiQFgwS7FPVDZeW1VjszCuVJ x3Lg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1681680852; x=1684272852; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=cP9JSIgzIwKlCqJpR4LA/JOVMTfnunGFo8i5nV2KCy4=; b=a47hscXsn7e6xTS2o3/Whg1rmau9CiMD/RiqoXF3fAvh4Tm1HNdJ/DGgWxSmMHcI6k iyIdMCIXx+ES8YuChU13IxmqCA6ca5SaQRFfZo0tEOTxkD4hQOCUjgC8QZPKz8Oe1Nqp s1pAu/+/+TX9AwI6BSFWWTEpO7Ak2Eo9291rTkKtetIfGXNFQMtNqYMcKdHh9gv9+cLO jM4lY6bajnz2CQnbYPO4BwVDTgnvY4x414Qr0U3gDsO5enJJSguyZlk2CWBpJlnQhJ85 bSxnmsLItWiwo3B/EU7wr8oEDzRFbutsa0iQ0ZHNwBhqisz0KULGE2n0o/TSGrjP49Kz VQgg== X-Gm-Message-State: AAQBX9eAwHD4M3pLl77v16igtRVV4gYDaEPGOE8TTl+Mm3p+B2ZfLQ3P RlfKicso9hbHrhgXavJEJkVjCCSYwDJG X-Google-Smtp-Source: AKy350YWot17ls0vE8VsKj6RzJTYf5B9iZn0jHLB0tn26sQ2C66qiY+SKQdmRNgmy8illcx6LlN3AQ607AQc X-Received: from davidai2.mtv.corp.google.com ([2620:15c:211:201:ebde:c661:1fa9:4737]) (user=davidai job=sendgmr) by 2002:a81:ae1a:0:b0:545:5b2c:4bf6 with SMTP id m26-20020a81ae1a000000b005455b2c4bf6mr8064815ywh.7.1681680852603; Sun, 16 Apr 2023 14:34:12 -0700 (PDT) Date: Sun, 16 Apr 2023 14:34:04 -0700 Mime-Version: 1.0 X-Mailer: git-send-email 2.40.0.634.g4ca3ef3211-goog Message-ID: <20230416213406.2966521-1-davidai@google.com> Subject: [RFC PATCH v1] sched/uclamp: Introduce SCHED_FLAG_RESET_UCLAMP_ON_FORK flag From: David Dai To: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Valentin Schneider Cc: David Dai , Qais Yousef , Quentin Perret , Saravana Kannan , kernel-team@android.com, linux-kernel@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" A userspace service may manage uclamp dynamically for individual tasks and a child task will unintentionally inherit a pesudo-random uclamp setting. This could result in the child task being stuck with a static uclamp value that results in poor performance or poor power. Using SCHED_FLAG_RESET_ON_FORK is too coarse for this usecase and will reset other useful scheduler attributes. Adding a SCHED_FLAG_RESET_UCLAMP_ON_FORK will allow userspace to have finer control over scheduler attributes of child processes. Cc: Qais Yousef Cc: Quentin Perret Cc: Saravana Kannan Signed-off-by: David Dai --- include/linux/sched.h | 3 +++ include/uapi/linux/sched.h | 4 +++- kernel/sched/core.c | 6 +++++- tools/include/uapi/linux/sched.h | 4 +++- 4 files changed, 14 insertions(+), 3 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 63d242164b1a..b1676b9381f9 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -885,6 +885,9 @@ struct task_struct { unsigned sched_reset_on_fork:1; unsigned sched_contributes_to_load:1; unsigned sched_migrated:1; +#ifdef CONFIG_UCLAMP_TASK + unsigned sched_reset_uclamp_on_fork:1; +#endif =20 /* Force alignment to the next boundary: */ unsigned :0; diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h index 3bac0a8ceab2..7515106e1f1a 100644 --- a/include/uapi/linux/sched.h +++ b/include/uapi/linux/sched.h @@ -132,12 +132,14 @@ struct clone_args { #define SCHED_FLAG_KEEP_PARAMS 0x10 #define SCHED_FLAG_UTIL_CLAMP_MIN 0x20 #define SCHED_FLAG_UTIL_CLAMP_MAX 0x40 +#define SCHED_FLAG_RESET_UCLAMP_ON_FORK 0x80 =20 #define SCHED_FLAG_KEEP_ALL (SCHED_FLAG_KEEP_POLICY | \ SCHED_FLAG_KEEP_PARAMS) =20 #define SCHED_FLAG_UTIL_CLAMP (SCHED_FLAG_UTIL_CLAMP_MIN | \ - SCHED_FLAG_UTIL_CLAMP_MAX) + SCHED_FLAG_UTIL_CLAMP_MAX | \ + SCHED_FLAG_RESET_UCLAMP_ON_FORK) =20 #define SCHED_FLAG_ALL (SCHED_FLAG_RESET_ON_FORK | \ SCHED_FLAG_RECLAIM | \ diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 0d18c3969f90..f2d5f7911855 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1943,6 +1943,10 @@ static void __setscheduler_uclamp(struct task_struct= *p, uclamp_se_set(&p->uclamp_req[UCLAMP_MAX], attr->sched_util_max, true); } + + p->sched_reset_uclamp_on_fork =3D !!(attr->sched_flags & + SCHED_FLAG_RESET_UCLAMP_ON_FORK); + } =20 static void uclamp_fork(struct task_struct *p) @@ -1956,7 +1960,7 @@ static void uclamp_fork(struct task_struct *p) for_each_clamp_id(clamp_id) p->uclamp[clamp_id].active =3D false; =20 - if (likely(!p->sched_reset_on_fork)) + if (likely(!p->sched_reset_on_fork && !p->sched_reset_uclamp_on_fork)) return; =20 for_each_clamp_id(clamp_id) { diff --git a/tools/include/uapi/linux/sched.h b/tools/include/uapi/linux/sc= hed.h index 3bac0a8ceab2..d52c59a2e0d0 100644 --- a/tools/include/uapi/linux/sched.h +++ b/tools/include/uapi/linux/sched.h @@ -132,12 +132,14 @@ struct clone_args { #define SCHED_FLAG_KEEP_PARAMS 0x10 #define SCHED_FLAG_UTIL_CLAMP_MIN 0x20 #define SCHED_FLAG_UTIL_CLAMP_MAX 0x40 +#define SCHED_FLAG_RESET_UCLAMP_ON_FORK 0x80 =20 #define SCHED_FLAG_KEEP_ALL (SCHED_FLAG_KEEP_POLICY | \ SCHED_FLAG_KEEP_PARAMS) =20 #define SCHED_FLAG_UTIL_CLAMP (SCHED_FLAG_UTIL_CLAMP_MIN | \ - SCHED_FLAG_UTIL_CLAMP_MAX) + SCHED_FLAG_UTIL_CLAMP_MAX | \ + SCHED_FLAG_RESET_UCLAMP_ON_FORK) =20 #define SCHED_FLAG_ALL (SCHED_FLAG_RESET_ON_FORK | \ SCHED_FLAG_RECLAIM | \ --=20 2.40.0.634.g4ca3ef3211-goog