From nobody Mon Dec 1 22:00:24 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 8E24E28C00C for ; Mon, 1 Dec 2025 06:47:21 +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=1764571641; cv=none; b=d6yYseCYJRj6m4pk3vsGOoxaXKN2TNohVJy7ZFYKAUHusDAx8qAkYJY9LRIenp3RrYiyAcqLj5AQBvWh6zxAxbLE0N9VvRX+gqD2hFVfVB2v9flgFlvvmWsjcdqxx7P2dMIvlZ68fni56jDa8cRJDksT+HG3if1EGZMTga0/ReI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764571641; c=relaxed/simple; bh=9XQI05SugEXGwU+xaX3it0tNYIdIhWS4ca01IHavz9I=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Y79aLk8KvtAiYNOnY2Ou4fwQ1XptXMW9kNoN2Pn1SLkMKA8jTiSEVJzUsMnNz/5O5kfIg4EMTEa5WqNGEsS5vEVsZeKMwRJnFd/ggOSkwWkLwxZWfxgkVgRklUPr8x/dvhqaGm9BaPpLuqohUfVwQbTfMrp7a1Ck2BgWsI60mOI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=b1DfgIvd; 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="b1DfgIvd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6D1B7C4CEF1; Mon, 1 Dec 2025 06:47:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1764571641; bh=9XQI05SugEXGwU+xaX3it0tNYIdIhWS4ca01IHavz9I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=b1DfgIvdGilNmzBhRV73GZAfAQo7+KQOu7HIjG7GVxd6Fqy8RUSBQh9WTW5wVVzgq A1EJ9ZUvOGi5LR+/TVo9Bkc2VeIFH6ZqNzBXcEYH7M/+zXnlznEbI3w4DjKGgQJs/b Y7HuR3sxL6StEArxaIvsYzo965EzeCQEhfR2qMQM0vt+i6IilIanZ8enuiUX47/0eF n89CTlOZ06/ndPZZ47ek3/4DZBtYfbD+mOBc/jF8bsPbvaVUQEhNdG+rsbkXnVYE62 yTuNQijIKQDHsmarMYflsWoWrpsch8K6rvkiPJSP5tMABYFL2+jS9t0uMvV7XBZYGj UYwO4VgD2Bw/w== 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 6/6] sched/fair: Rename cfs_rq::avg_vruntime to ::sum_w_vruntime, and helper functions Date: Mon, 1 Dec 2025 07:46:47 +0100 Message-ID: <20251201064647.1851919-7-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_vruntime field is a misnomer: it says it's an 'average vruntime', but in reality it's the momentary sum of the weighted vruntimes of all queued tasks, which is at least a division away from being an average. This is clear from comments about the math of fair scheduling: * \Sum (v_i - v0) * w_i :=3D cfs_rq->avg_vruntime This confusion is increased by the cfs_avg_vruntime() function, which does perform the division and returns a true average. The sum of all weighted vruntimes should be named thusly, so rename the field to ::sum_w_vruntime. (As arguably ::sum_weighted_vruntime would be a bit of a mouthful.) Understanding the scheduler is hard enough already, without extra layers of obfuscated naming. ;-) Also rename related helper functions: sum_vruntime_add() =3D> sum_w_vruntime_add() sum_vruntime_sub() =3D> sum_w_vruntime_sub() sum_vruntime_update() =3D> sum_w_vruntime_update() With the notable exception of cfs_avg_vruntime(), which was named accurately. Signed-off-by: Ingo Molnar --- kernel/sched/debug.c | 2 +- kernel/sched/fair.c | 26 +++++++++++++------------- kernel/sched/sched.h | 2 +- 3 files changed, 15 insertions(+), 15 deletions(-) diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index a6ceda12bd35..b6fa5ca6a932 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -828,7 +828,7 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct c= fs_rq *cfs_rq) SPLIT_NS(left_vruntime)); SEQ_printf(m, " .%-30s: %Ld.%06ld\n", "zero_vruntime", SPLIT_NS(zero_vruntime)); - SEQ_printf(m, " .%-30s: %Ld.%06ld\n", "avg_vruntime", + SEQ_printf(m, " .%-30s: %Ld.%06ld\n", "sum_w_vruntime", SPLIT_NS(cfs_avg_vruntime(cfs_rq))); SEQ_printf(m, " .%-30s: %Ld.%06ld\n", "right_vruntime", SPLIT_NS(right_vruntime)); diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 2ffd52a2e7a0..41ede30b74cd 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -607,7 +607,7 @@ static inline s64 entity_key(struct cfs_rq *cfs_rq, str= uct sched_entity *se) * Which we track using: * * v0 :=3D cfs_rq->zero_vruntime - * \Sum (v_i - v0) * w_i :=3D cfs_rq->avg_vruntime + * \Sum (v_i - v0) * w_i :=3D cfs_rq->sum_w_vruntime * \Sum w_i :=3D cfs_rq->sum_weight * * Since zero_vruntime closely tracks the per-task service, these @@ -619,32 +619,32 @@ static inline s64 entity_key(struct cfs_rq *cfs_rq, s= truct sched_entity *se) * As measured, the max (key * weight) value was ~44 bits for a kernel bui= ld. */ static void -avg_vruntime_add(struct cfs_rq *cfs_rq, struct sched_entity *se) +sum_w_vruntime_add(struct cfs_rq *cfs_rq, struct sched_entity *se) { unsigned long weight =3D scale_load_down(se->load.weight); s64 key =3D entity_key(cfs_rq, se); =20 - cfs_rq->avg_vruntime +=3D key * weight; + cfs_rq->sum_w_vruntime +=3D key * weight; cfs_rq->sum_weight +=3D weight; } =20 static void -avg_vruntime_sub(struct cfs_rq *cfs_rq, struct sched_entity *se) +sum_w_vruntime_sub(struct cfs_rq *cfs_rq, struct sched_entity *se) { unsigned long weight =3D scale_load_down(se->load.weight); s64 key =3D entity_key(cfs_rq, se); =20 - cfs_rq->avg_vruntime -=3D key * weight; + cfs_rq->sum_w_vruntime -=3D key * weight; cfs_rq->sum_weight -=3D weight; } =20 static inline -void avg_vruntime_update(struct cfs_rq *cfs_rq, s64 delta) +void sum_w_vruntime_update(struct cfs_rq *cfs_rq, s64 delta) { /* - * v' =3D v + d =3D=3D> avg_vruntime' =3D avg_runtime - d*sum_weight + * v' =3D v + d =3D=3D> sum_w_vruntime' =3D sum_runtime - d*sum_weight */ - cfs_rq->avg_vruntime -=3D cfs_rq->sum_weight * delta; + cfs_rq->sum_w_vruntime -=3D cfs_rq->sum_weight * delta; } =20 /* @@ -654,7 +654,7 @@ void avg_vruntime_update(struct cfs_rq *cfs_rq, s64 del= ta) u64 cfs_avg_vruntime(struct cfs_rq *cfs_rq) { struct sched_entity *curr =3D cfs_rq->curr; - s64 avg =3D cfs_rq->avg_vruntime; + s64 avg =3D cfs_rq->sum_w_vruntime; long load =3D cfs_rq->sum_weight; =20 if (curr && curr->on_rq) { @@ -722,7 +722,7 @@ static void update_entity_lag(struct cfs_rq *cfs_rq, st= ruct sched_entity *se) 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; + s64 avg =3D cfs_rq->sum_w_vruntime; long load =3D cfs_rq->sum_weight; =20 if (curr && curr->on_rq) { @@ -745,7 +745,7 @@ static void update_zero_vruntime(struct cfs_rq *cfs_rq) u64 vruntime =3D cfs_avg_vruntime(cfs_rq); s64 delta =3D (s64)(vruntime - cfs_rq->zero_vruntime); =20 - avg_vruntime_update(cfs_rq, delta); + sum_w_vruntime_update(cfs_rq, delta); =20 cfs_rq->zero_vruntime =3D vruntime; } @@ -819,7 +819,7 @@ RB_DECLARE_CALLBACKS(static, min_vruntime_cb, struct sc= hed_entity, */ static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *s= e) { - avg_vruntime_add(cfs_rq, se); + sum_w_vruntime_add(cfs_rq, se); update_zero_vruntime(cfs_rq); se->min_vruntime =3D se->vruntime; se->min_slice =3D se->slice; @@ -831,7 +831,7 @@ static void __dequeue_entity(struct cfs_rq *cfs_rq, str= uct sched_entity *se) { rb_erase_augmented_cached(&se->run_node, &cfs_rq->tasks_timeline, &min_vruntime_cb); - avg_vruntime_sub(cfs_rq, se); + sum_w_vruntime_sub(cfs_rq, se); update_zero_vruntime(cfs_rq); } =20 diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 54994d93958a..f0eb58458ff3 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -678,7 +678,7 @@ struct cfs_rq { unsigned int h_nr_runnable; /* SCHED_{NORMAL,BATCH,IDLE} */ unsigned int h_nr_idle; /* SCHED_IDLE */ =20 - s64 avg_vruntime; + s64 sum_w_vruntime; u64 sum_weight; =20 u64 zero_vruntime; --=20 2.51.0