From nobody Sun Feb 8 12:57:56 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 BB323C0015E for ; Mon, 17 Jul 2023 12:57:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230348AbjGQM5P (ORCPT ); Mon, 17 Jul 2023 08:57:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38048 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230479AbjGQM5F (ORCPT ); Mon, 17 Jul 2023 08:57:05 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8B88419B7; Mon, 17 Jul 2023 05:56:33 -0700 (PDT) Date: Mon, 17 Jul 2023 12:56:12 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1689598572; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=UDv4HP9mRzXxcXfC+VJIpYPLsIPQeo902sc28kX/Cj0=; b=pEOLZYMbwtm4eVJOa9OSX/2kAHjuEDD7A4hmPFxgDBoVFbNvCflrlXyFDsJkrvlqF6n7XW jLY8vbRX/CXk0+pG6gm6q8LJW3qK/6x2GEsHKIZhYP73u33lP007Csdvd/aGfYNVio/nw7 4BgpuMJX2PRJA8sdqxnL3ygws3UtTYjQPf98W3fUKXIc/NZe4hOxJOtdpoL4UOyktzAYFM 2oHm2zCW/EgQDjonIMWrr8rhTVXNRx3mTwpcz0qwEM7G5FmqkFXcdZsZlapQe3sWdwUwKR IlMnYmBfP4SAX7fIAudoxngX/BMk/fJk1RLQ5BOETqmBC8GspIFJMxXamyFIEA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1689598572; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=UDv4HP9mRzXxcXfC+VJIpYPLsIPQeo902sc28kX/Cj0=; b=9tiZieivV41M2oV/0Lg4gDS+I7aPyb5F2Iptla/BqZPKtgoCjk8dSvPd0+w66WpTpPYUMz 3eABOqPauC77/RDg== From: "tip-bot2 for Tim C Chen" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] sched/fair: Implement prefer sibling imbalance calculation between asymmetric groups Cc: Tim Chen , "Peter Zijlstra (Intel)" , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: =?utf-8?q?=3C4eacbaa236e680687dae2958378a6173654113df=2E16887?= =?utf-8?q?70494=2Egit=2Etim=2Ec=2Echen=40linux=2Eintel=2Ecom=3E?= References: =?utf-8?q?=3C4eacbaa236e680687dae2958378a6173654113df=2E168877?= =?utf-8?q?0494=2Egit=2Etim=2Ec=2Echen=40linux=2Eintel=2Ecom=3E?= MIME-Version: 1.0 Message-ID: <168959857230.28540.6981196186824283885.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/core branch of tip: Commit-ID: 7ff1693236f5d97a939dbeb660c07671a2d57071 Gitweb: https://git.kernel.org/tip/7ff1693236f5d97a939dbeb660c07671a= 2d57071 Author: Tim C Chen AuthorDate: Fri, 07 Jul 2023 15:57:02 -07:00 Committer: Peter Zijlstra CommitterDate: Thu, 13 Jul 2023 15:21:52 +02:00 sched/fair: Implement prefer sibling imbalance calculation between asymmetr= ic groups In the current prefer sibling load balancing code, there is an implicit assumption that the busiest sched group and local sched group are equivalent, hence the tasks to be moved is simply the difference in number of tasks between the two groups (i.e. imbalance) divided by two. However, we may have different number of cores between the cluster groups, say when we take CPU offline or we have hybrid groups. In that case, we should balance between the two groups such that #tasks/#cores ratio is the same between the same between both groups. Hence the imbalance computed will need to reflect this. Adjust the sibling imbalance computation to take into account of the above considerations. Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/4eacbaa236e680687dae2958378a6173654113df.16= 88770494.git.tim.c.chen@linux.intel.com --- kernel/sched/fair.c | 41 +++++++++++++++++++++++++++++++++++++---- 1 file changed, 37 insertions(+), 4 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index accbfbb..c6246fb 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -9535,6 +9535,41 @@ static inline bool smt_balance(struct lb_env *env, s= truct sg_lb_stats *sgs, return false; } =20 +static inline long sibling_imbalance(struct lb_env *env, + struct sd_lb_stats *sds, + struct sg_lb_stats *busiest, + struct sg_lb_stats *local) +{ + int ncores_busiest, ncores_local; + long imbalance; + + if (env->idle =3D=3D CPU_NOT_IDLE || !busiest->sum_nr_running) + return 0; + + ncores_busiest =3D sds->busiest->cores; + ncores_local =3D sds->local->cores; + + if (ncores_busiest =3D=3D ncores_local) { + imbalance =3D busiest->sum_nr_running; + lsub_positive(&imbalance, local->sum_nr_running); + return imbalance; + } + + /* Balance such that nr_running/ncores ratio are same on both groups */ + imbalance =3D ncores_local * busiest->sum_nr_running; + lsub_positive(&imbalance, ncores_busiest * local->sum_nr_running); + /* Normalize imbalance and do rounding on normalization */ + imbalance =3D 2 * imbalance + ncores_local + ncores_busiest; + imbalance /=3D ncores_local + ncores_busiest; + + /* Take advantage of resource in an empty sched group */ + if (imbalance =3D=3D 0 && local->sum_nr_running =3D=3D 0 && + busiest->sum_nr_running > 1) + imbalance =3D 2; + + return imbalance; +} + static inline bool sched_reduced_capacity(struct rq *rq, struct sched_domain *sd) { @@ -10393,14 +10428,12 @@ static inline void calculate_imbalance(struct lb_= env *env, struct sd_lb_stats *s } =20 if (busiest->group_weight =3D=3D 1 || sds->prefer_sibling) { - unsigned int nr_diff =3D busiest->sum_nr_running; /* * When prefer sibling, evenly spread running tasks on * groups. */ env->migration_type =3D migrate_task; - lsub_positive(&nr_diff, local->sum_nr_running); - env->imbalance =3D nr_diff; + env->imbalance =3D sibling_imbalance(env, sds, busiest, local); } else { =20 /* @@ -10597,7 +10630,7 @@ static struct sched_group *find_busiest_group(struc= t lb_env *env) * group's child domain. */ if (sds.prefer_sibling && local->group_type =3D=3D group_has_spare && - busiest->sum_nr_running > local->sum_nr_running + 1) + sibling_imbalance(env, &sds, busiest, local) > 1) goto force_balance; =20 if (busiest->group_type !=3D group_overloaded) {