From nobody Mon Dec 1 22:01:45 2025 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 152E628C00C for ; Mon, 1 Dec 2025 06:47:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764571638; cv=none; b=jHbjptznv5xEk6so2qCbziQl/Sot7wJFKn1fntoqCn9IVnst4yfeftKUCV6PPGr88YTHegML8OagSJ92vfTvjm0ZBfk1AeAbmYZMkXPRpBQEkqzOr0G5xbHuXDFtSQnCvhCKpWEfYvujTu9kwfgtkdao5v8LgljM40PwVz8kjfQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764571638; c=relaxed/simple; bh=bxmMoilf/XYowX5IImYa/h2tk2jPbflYVNMP1QhqnwM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ZDEP2vSkgMQU/nrIE/u/YN4WizAK+LMGjb3fpg5kgRpHlkDlXWs7eeaAXDLNtM2V8RtQmOm5GSpRCc5sgr6JAzPKeLsnJich6lDRocI5tCMmGEY+ABRJJAGukrGml2r2BloaCi21Ju/2Y85VEBx4AIzsTVbfUGkQwu/c3zmppSc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=CxiUcpU+; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="CxiUcpU+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 35E78C116D0; Mon, 1 Dec 2025 06:47:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764571638; bh=bxmMoilf/XYowX5IImYa/h2tk2jPbflYVNMP1QhqnwM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CxiUcpU+HBY2nRfFjmB+wkuDgUClRuKJLox7CBphfuoqPJ3/Mtf7dib7D4N6MKlNI Z4+3Ek/Rc7bJtA2986l8MazGKIvhlX/jwvPdqGdJ7gwjIw2K+wCbRIspkxgustBJAG dyVnrU5eCLoHrNrvgh83rezQpv2T5VOe2dinlCPgJJCWIyOy2OnaJnA6XbDETVGmMe Gg5rFN5jKRbbKmPQogPH0v6twqZkHkA9ZRmrVOX06R+ZqFkFK5NQ2fKrCBT0wTYlbx KAAy6VOyIjsCVSV+LC1RwsULeesX9tV8aEz/FRVibTRdA5jc7D2avRGppU81f2pEer /6EhPKqR8pgsg== From: Ingo Molnar To: linux-kernel@vger.kernel.org Cc: Peter Zijlstra , Juri Lelli , Dietmar Eggemann , Valentin Schneider , Vincent Guittot , Shrikanth Hegde , Linus Torvalds , Mel Gorman , Steven Rostedt , Thomas Gleixner , Ingo Molnar Subject: [PATCH 5/6] sched/fair: Rename cfs_rq::avg_load to cfs_rq::sum_weight Date: Mon, 1 Dec 2025 07:46:46 +0100 Message-ID: <20251201064647.1851919-6-mingo@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251201064647.1851919-1-mingo@kernel.org> References: <20251201064647.1851919-1-mingo@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The ::avg_load field is a long-standing misnomer: it says it's an 'average load', but in reality it's the momentary sum of the load of all currently runnable tasks. We'd have to also perform a division by nr_running (or use time-decay) to arrive at any sort of average value. This is clear from comments about the math of fair scheduling: * \Sum w_i :=3D cfs_rq->avg_load The sum of all weights is ... the sum of all weights, not the average of all weights. To make it doubly confusing, there's also an ::avg_load in the load-balancing struct sg_lb_stats, which *is* a true average. The second part of the field's name is a minor misnomer as well: it says 'load', and it is indeed a load_weight structure as it shares code with the load-balancer - but it's only in an SMP load-balancing context where load =3D weight, in the fair scheduling context the primary purpose is the weighting of different nice levels. So rename the field to ::sum_weight instead, which makes the terminology of the EEVDF math match up with our implementation of it: * \Sum w_i :=3D cfs_rq->sum_weight Signed-off-by: Ingo Molnar --- kernel/sched/fair.c | 16 ++++++++-------- kernel/sched/sched.h | 2 +- 2 files changed, 9 insertions(+), 9 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 3d6d551168aa..2ffd52a2e7a0 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -608,7 +608,7 @@ static inline s64 entity_key(struct cfs_rq *cfs_rq, str= uct sched_entity *se) * * v0 :=3D cfs_rq->zero_vruntime * \Sum (v_i - v0) * w_i :=3D cfs_rq->avg_vruntime - * \Sum w_i :=3D cfs_rq->avg_load + * \Sum w_i :=3D cfs_rq->sum_weight * * Since zero_vruntime closely tracks the per-task service, these * deltas: (v_i - v), will be in the order of the maximal (virtual) lag @@ -625,7 +625,7 @@ avg_vruntime_add(struct cfs_rq *cfs_rq, struct sched_en= tity *se) s64 key =3D entity_key(cfs_rq, se); =20 cfs_rq->avg_vruntime +=3D key * weight; - cfs_rq->avg_load +=3D weight; + cfs_rq->sum_weight +=3D weight; } =20 static void @@ -635,16 +635,16 @@ avg_vruntime_sub(struct cfs_rq *cfs_rq, struct sched_= entity *se) s64 key =3D entity_key(cfs_rq, se); =20 cfs_rq->avg_vruntime -=3D key * weight; - cfs_rq->avg_load -=3D weight; + cfs_rq->sum_weight -=3D weight; } =20 static inline void avg_vruntime_update(struct cfs_rq *cfs_rq, s64 delta) { /* - * v' =3D v + d =3D=3D> avg_vruntime' =3D avg_runtime - d*avg_load + * v' =3D v + d =3D=3D> avg_vruntime' =3D avg_runtime - d*sum_weight */ - cfs_rq->avg_vruntime -=3D cfs_rq->avg_load * delta; + cfs_rq->avg_vruntime -=3D cfs_rq->sum_weight * delta; } =20 /* @@ -655,7 +655,7 @@ u64 cfs_avg_vruntime(struct cfs_rq *cfs_rq) { struct sched_entity *curr =3D cfs_rq->curr; s64 avg =3D cfs_rq->avg_vruntime; - long load =3D cfs_rq->avg_load; + long load =3D cfs_rq->sum_weight; =20 if (curr && curr->on_rq) { unsigned long weight =3D scale_load_down(curr->load.weight); @@ -723,7 +723,7 @@ static int vruntime_eligible(struct cfs_rq *cfs_rq, u64= vruntime) { struct sched_entity *curr =3D cfs_rq->curr; s64 avg =3D cfs_rq->avg_vruntime; - long load =3D cfs_rq->avg_load; + long load =3D cfs_rq->sum_weight; =20 if (curr && curr->on_rq) { unsigned long weight =3D scale_load_down(curr->load.weight); @@ -5172,7 +5172,7 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_enti= ty *se, int flags) * * vl_i =3D (W + w_i)*vl'_i / W */ - load =3D cfs_rq->avg_load; + load =3D cfs_rq->sum_weight; if (curr && curr->on_rq) load +=3D scale_load_down(curr->load.weight); =20 diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 47f7b6df634c..54994d93958a 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -679,7 +679,7 @@ struct cfs_rq { unsigned int h_nr_idle; /* SCHED_IDLE */ =20 s64 avg_vruntime; - u64 avg_load; + u64 sum_weight; =20 u64 zero_vruntime; #ifdef CONFIG_SCHED_CORE --=20 2.51.0