From nobody Tue Sep 9 17:14:39 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 A847CC61DA3 for ; Tue, 21 Feb 2023 08:24:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233320AbjBUIYo (ORCPT ); Tue, 21 Feb 2023 03:24:44 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40228 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229835AbjBUIYm (ORCPT ); Tue, 21 Feb 2023 03:24:42 -0500 Received: from mail-ed1-x52c.google.com (mail-ed1-x52c.google.com [IPv6:2a00:1450:4864:20::52c]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0681C1EFF4 for ; Tue, 21 Feb 2023 00:24:41 -0800 (PST) Received: by mail-ed1-x52c.google.com with SMTP id o12so14171479edb.9 for ; Tue, 21 Feb 2023 00:24:40 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=cc:to:subject:message-id:date:from:mime-version:from:to:cc:subject :date:message-id:reply-to; bh=oPBARR1XQLY58c737UTH5eoRSYkaY0yhf7AxAKsB3Ys=; b=FTilw8opE7NXkwjgsqlx6udSECCNGFBY5jaRwzj4cGQKeJb5vWv+kxlubSWOd+ugd3 YUoiba4n0y27qNw2IG7TyFincOVCdOnSS5o8Yt1r6jLDQ5C8uD/cOa/FWgdTkS9ZXfok 0Vvy9OT547060nJLz8ilID+aiMbTrxQlPVicHnmM06nMDACwhPUPfzJAIymM56uUXkX+ dI9ixC3Q47KBiisYcvISlL28WTmCHZS2MXFAB87dPSsWVA9CXUtTFR9LRuuwcMtXqet4 Gvpy0DSSTvGany6XHc+Fn2uEUf/Jdn8z8BXax70b58KSU+SHVNnvXaVDYMvhemsre1kM PITw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:mime-version:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=oPBARR1XQLY58c737UTH5eoRSYkaY0yhf7AxAKsB3Ys=; b=GJAXKdGMS+9Ems/DSAHBjx7eBa1ZIFPCD1kyWhd5eOF/ScnfA6tM3RBjWOpcaCp/Uy Mg4DQchM+oqaRt1lEkdFHxWqZ6V5vXqvvgoilzjnBV79D3tNLxUcv88usIqq5fROTYQq yoEy3dhbwBOpcwmOGnm8w6haPfH3x+XynJzWC+H1q4LwSRPb7ySLBzNEmLAebuYn8ktO NKhHr+D3Lzsk0HPlr2R5Nev8boWjPT+/28EfgjGjYuamhrFfD0RS40g8h95TBVJyMVl6 Y84U/NMQd6yg+G+41YmEneAhfhp6tSa9LCiTnpIxdxXdhZxDC3EHEj/M0wDmz495znSc SyAQ== X-Gm-Message-State: AO0yUKWJqOL5D4/NSVN4e9eZ4oHO5d6JQRksKGwDoHvxz2Y37ycTrpLY lTI9kigtewpSmhzRlUcxvGDG51GVYbbauOu8jwRg4Fhgu6A= X-Google-Smtp-Source: AK7set92wsZHs0StkibTXHBpXgiS8paznGlOif4P/bhC35luKsT8XnDF1ma7j/vFpwvdwEWrkJLvTn4C10ASjMixMm4= X-Received: by 2002:a17:906:d966:b0:889:8b2f:75d1 with SMTP id rp6-20020a170906d96600b008898b2f75d1mr5350016ejb.10.1676967879345; Tue, 21 Feb 2023 00:24:39 -0800 (PST) MIME-Version: 1.0 From: JaeJoon Jung Date: Tue, 21 Feb 2023 17:24:27 +0900 Message-ID: Subject: [PATCH] kernel/sched/core.c: Modified prio_less(). To: Peter Zijlstra , Ingo Molnar Cc: 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" The sched_class structure is defined to be sorted by pointer size. You can see it in the macro definition like this: kernel/sched/sched.h #define DEFINE_SCHED_CLASS(name) const struct sched_class name##_sched_class \ __aligned(__alignof__(struct sched_class)) \ __section("__" #name "_sched_class") include/asm-generic/vmlinux.lds.h #define SCHED_DATA \ STRUCT_ALIGN(); \ __sched_class_highest =3D .; \ *(__stop_sched_class) \ *(__dl_sched_class) \ *(__rt_sched_class) \ *(__fair_sched_class) \ *(__idle_sched_class) \ __sched_class_lowest =3D .; And in the System.map file, you can see that they are arranged in memory address order. System.map ---------------------------------------------------------------- ffffffff8260d520 R __sched_class_highest ffffffff8260d520 R stop_sched_class ffffffff8260d5f0 R dl_sched_class ffffffff8260d6c0 R rt_sched_class ffffffff8260d790 R fair_sched_class ffffffff8260d860 R idle_sched_class ffffffff8260d930 R __sched_class_lowest ---------------------------------------------------------------- This matches the sched class priority. In the prio_less() function in kernel/sched/core.c, the less value can be determined by pointer operation as follows. If the prio_less() function is modified as follows, the __task_prio() function is not required. Thanks, Signed-off-by: JaeJoon Jung --- kernel/sched/core.c | 42 +++++++++++------------------------------- 1 file changed, 11 insertions(+), 31 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 2a4918a1faa9..75075d92a198 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -151,21 +151,6 @@ __read_mostly int scheduler_running; DEFINE_STATIC_KEY_FALSE(__sched_core_enabled); -/* kernel prio, less is more */ -static inline int __task_prio(struct task_struct *p) -{ - if (p->sched_class =3D=3D &stop_sched_class) /* trumps deadline */ - return -2; - - if (rt_prio(p->prio)) /* includes deadline */ - return p->prio; /* [-1, 99] */ - - if (p->sched_class =3D=3D &idle_sched_class) - return MAX_RT_PRIO + NICE_WIDTH; /* 140 */ - - return MAX_RT_PRIO + MAX_NICE; /* 120, squash fair */ -} - /* * l(a,b) * le(a,b) :=3D !l(b,a) @@ -176,22 +161,17 @@ static inline int __task_prio(struct task_struct *p) /* real prio, less is less */ static inline bool prio_less(struct task_struct *a, struct task_struct *b, bool in_fi) { - - int pa =3D __task_prio(a), pb =3D __task_prio(b); - - if (-pa < -pb) - return true; - - if (-pb < -pa) - return false; - - if (pa =3D=3D -1) /* dl_prio() doesn't work because of stop_class above */ - return !dl_time_before(a->dl.deadline, b->dl.deadline); - - if (pa =3D=3D MAX_RT_PRIO + MAX_NICE) /* fair */ - return cfs_prio_less(a, b, in_fi); - - return false; + int less =3D a->sched_class - b->sched_class; + if (less =3D=3D 0) { + if (a->sched_class =3D=3D &dl_sched_class) + return !dl_time_before(a->dl.deadline, b->dl.deadl= ine); + + else if (a->sched_class =3D=3D &fair_sched_class) + return cfs_prio_less(a, b, in_fi); + else + return false; + } else + return (less > 0) ? true : false; } static inline bool __sched_core_less(struct task_struct *a, struct task_struct *b) --=20 2.17.1