From nobody Fri Dec 19 00:21:38 2025 Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C54DC228CB5 for ; Mon, 2 Jun 2025 18:06:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748887572; cv=none; b=eEXUgs8s0eRFUPw4EABI4WnuONC1OYfCYTIRkFNGRZz0WdCDVqt4O0O70f8kPMxbMTO2bY3EaCFocORcIacedUvMUP+jNOdir584vak08s1aQ3nPR/VzK58u7q9eVt+AReHcrmDoICw0EOWp48I9PqUhtD5wCT80oBLsH4PT+nc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1748887572; c=relaxed/simple; bh=xt14giH4H2Boj1LehC8v8p2UGvEQ5ROsW4o3kmI6NEs=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Tk0JxWB8gaJ+LR3DavUZ7fFLYWCAotKwqFKBMw31atCeBdg0O6U8QrSw6VDf9yFXVLUQaQKyel59KibVjm3vopdaeiicCGf4lm1Og4W6SZzVaYbUugaxMI3foGnoqleFSxFept7cF9hC3azuqCxOyr4Gd4BmixXaa5Mp/t3LK6w= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--zecheng.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=cDCgLPKc; arc=none smtp.client-ip=209.85.219.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--zecheng.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="cDCgLPKc" Received: by mail-yb1-f202.google.com with SMTP id 3f1490d57ef6-e812d1126deso2499508276.1 for ; Mon, 02 Jun 2025 11:06:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1748887568; x=1749492368; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=TCrDrn8l7ZQ01wUSaHvfLKKVmhd43n1nTteE9Ulczlg=; b=cDCgLPKcWRFllHkTi4FeWQ5onVOJOtDwIOQ2p1O2t/DZCXOC+uzdN1VHsGLRz3aShe yil294lM8LYZwb8bXiCW9xFyckN6tVwXQFnAA4pGKhkcWu1J+9XKbkvKIyWwPeglUsEg aR+1ppDndrWUX93xpUe8jhxQqmRDEE7QFEFUPxn4kYdcuj1FMIcimAbeNg1beV8dY43z fUWQjDM0sf3C2wEHlFxI7zOrad9zQHBdJnNUiTUVKLbKz/tkxPCztdgFXaju7sKvV6+8 gGeRFCccRdEnndF+QJYjt06ngNixMFcGexjVQC0wZLxpNvCjgKhKoDb1VU/tGjvyhlJc OBrQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1748887568; x=1749492368; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=TCrDrn8l7ZQ01wUSaHvfLKKVmhd43n1nTteE9Ulczlg=; b=vgq6HFKY/FydoJyk5YMsFY2OxqpEJhA3fvaD7CWVKoSAOasXwvHmBPgJN812vo3j3E Rlm5P5ZXXx8YMuXHtalY0efTfv5laeb5T5fRyfDW1VSqLNxis8RioMKaIKXupZTot08d 4N2fjEnzK3ABdJxHqupcDCAgsvzI0YUW4I4opfUvlO33tJh1RXq7CU2gjB5dFZg6bg16 MuFlguX6jWhBiiyhUdS7Lal3zRBDz3dL5O9whJYCTpO2d6IP56eJ+vK8XmZMtyThw5gr 85yOn7h1//7QjNo8E+xeBQy6vesL/5uBQRamXHaKQB2qPo0KX9z2xvYbPafveA+Jpy1O qKNg== X-Forwarded-Encrypted: i=1; AJvYcCVYLuqrdj/EPg5bfvMlqYxfQM5u7A9vrCDZCJ4ydyqCDInuDeamYku8vU8naHvbRnAnnTKuIi+dy3hCAIQ=@vger.kernel.org X-Gm-Message-State: AOJu0YyB4Nc8le7c2RNhGaKFhvjQ0nrnvGZB2euNqaN8A9vKohsmyDZJ L+q6SjPR+nbGKQDTKkjgMavTmJ70FjAs/N961hPdixlYlRyGSzoGzcIpgXfEI+t96wu2LQIeHR5 GD3OSE4+4ZA== X-Google-Smtp-Source: AGHT+IHcNb6bKXDTsa0HdCWFtVoy0XH/LU/dCeX+oRa/ab36fKnnncKj2TfD6Sgznxdk3pAEH4A7mfXJlwlp X-Received: from ybbgr8.prod.google.com ([2002:a05:6902:6208:b0:e7d:6f4c:cf59]) (user=zecheng job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6902:c04:b0:e7d:a6f8:2eb2 with SMTP id 3f1490d57ef6-e8128c7348dmr11955643276.35.1748887568266; Mon, 02 Jun 2025 11:06:08 -0700 (PDT) Date: Mon, 2 Jun 2025 18:05:43 +0000 In-Reply-To: <20250602180544.3626909-1-zecheng@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250602180544.3626909-1-zecheng@google.com> X-Mailer: git-send-email 2.49.0.1204.g71687c7c1d-goog Message-ID: <20250602180544.3626909-4-zecheng@google.com> Subject: [RFC PATCH v2 3/3] sched/fair: Reorder struct sched_entity From: Zecheng Li To: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot Cc: Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Xu Liu , Blake Jones , Josh Don , Madadi Vineeth Reddy , linux-kernel@vger.kernel.org, Zecheng Li Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Groups the mostly read fields in struct sched_entity to the head of the struct when `CONFIG_FAIR_GROUP_SCHED` is set. The additional fields from `CONFIG_FAIR_GROUP_SCHED` are related to CFS cgroup scheduling and were placed far away from the hot fields `load`, `on_rq` and `vruntime`. They are moved together to the head of the struct to exploit locality. Although `depth` is not as hot as other fields, we keep it here to avoid breaking the #ifdef boundaries. Adds enforced alignment of struct sched_entity to ensure the cache group works as intended. Also adds a compile time check when `CONFIG_FAIR_GROUP_SCHED` is set to check the placement of the hot fields. Signed-off-by: Zecheng Li --- include/linux/sched.h | 39 +++++++++++++++++++++------------------ kernel/sched/core.c | 20 ++++++++++++++++++++ 2 files changed, 41 insertions(+), 18 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index f96ac1982893..b20b2d590cf6 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -567,40 +567,43 @@ struct sched_statistics { } ____cacheline_aligned; =20 struct sched_entity { +#ifdef CONFIG_FAIR_GROUP_SCHED + /* Group the read most hot fields in sched_entity */ + __cacheline_group_begin(hot); + struct sched_entity *parent; + /* rq on which this entity is (to be) queued: */ + struct cfs_rq *cfs_rq; + /* rq "owned" by this entity/group: */ + struct cfs_rq *my_q; + /* cached value of my_q->h_nr_running */ + unsigned long runnable_weight; + int depth; +#endif + unsigned char on_rq; + unsigned char sched_delayed; + unsigned char rel_deadline; + unsigned char custom_slice; /* For load-balancing: */ struct load_weight load; + u64 vruntime; +#ifdef CONFIG_FAIR_GROUP_SCHED + __cacheline_group_end(hot); +#endif struct rb_node run_node; u64 deadline; u64 min_vruntime; u64 min_slice; =20 struct list_head group_node; - unsigned char on_rq; - unsigned char sched_delayed; - unsigned char rel_deadline; - unsigned char custom_slice; - /* hole */ =20 u64 exec_start; u64 sum_exec_runtime; u64 prev_sum_exec_runtime; - u64 vruntime; s64 vlag; u64 slice; =20 u64 nr_migrations; =20 -#ifdef CONFIG_FAIR_GROUP_SCHED - int depth; - struct sched_entity *parent; - /* rq on which this entity is (to be) queued: */ - struct cfs_rq *cfs_rq; - /* rq "owned" by this entity/group: */ - struct cfs_rq *my_q; - /* cached value of my_q->h_nr_running */ - unsigned long runnable_weight; -#endif - #ifdef CONFIG_SMP /* * Per entity load average tracking. @@ -610,7 +613,7 @@ struct sched_entity { */ struct sched_avg avg; #endif -}; +} ____cacheline_aligned; =20 struct sched_rt_entity { struct list_head run_list; diff --git a/kernel/sched/core.c b/kernel/sched/core.c index ba89cd4f2fac..dcc50df9e8ca 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -8525,6 +8525,7 @@ static struct kmem_cache *task_group_cache __ro_after= _init; #endif =20 static void __init cfs_rq_struct_check(void); +static void __init sched_entity_struct_check(void); =20 void __init sched_init(void) { @@ -8543,6 +8544,7 @@ void __init sched_init(void) BUG_ON(!sched_class_above(&ext_sched_class, &idle_sched_class)); #endif cfs_rq_struct_check(); + sched_entity_struct_check(); wait_bit_init(); =20 #ifdef CONFIG_FAIR_GROUP_SCHED @@ -10805,3 +10807,21 @@ static void __init cfs_rq_struct_check(void) #endif #endif } + +static void __init sched_entity_struct_check(void) +{ + /* + * The compile time check is only enabled with CONFIG_FAIR_GROUP_SCHED. + * We care about the placement of six hottest fields below. + */ +#ifdef CONFIG_FAIR_GROUP_SCHED + CACHELINE_ASSERT_GROUP_MEMBER(struct sched_entity, hot, parent); + CACHELINE_ASSERT_GROUP_MEMBER(struct sched_entity, hot, cfs_rq); + CACHELINE_ASSERT_GROUP_MEMBER(struct sched_entity, hot, my_q); + CACHELINE_ASSERT_GROUP_MEMBER(struct sched_entity, hot, + runnable_weight); + CACHELINE_ASSERT_GROUP_MEMBER(struct sched_entity, hot, on_rq); + CACHELINE_ASSERT_GROUP_MEMBER(struct sched_entity, hot, load); + CACHELINE_ASSERT_GROUP_MEMBER(struct sched_entity, hot, vruntime); +#endif +} --=20 2.49.0