From nobody Thu Oct 2 17:00:10 2025 Received: from mail-wr1-f50.google.com (mail-wr1-f50.google.com [209.85.221.50]) (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 CA7CC1DE4CA for ; Sun, 14 Sep 2025 13:44:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.50 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757857476; cv=none; b=PgrE/qDf5b/zcQlC2+GL0lnMJxjEHIxl2lvJQEXHaDGOrye82l4i38WgF/pdnotMMrx1MKlv8ZN6gehQY1ZVlpzMgWbO4EexrUi/EduaoqXag+rSh7CQGduX7FWkpheb1mUycBSPuZF2p719/T4wDBFjjthFGlSH1BpGxkuhIsw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757857476; c=relaxed/simple; bh=gIeZApGTCwvtD7M1UghQoeDndvD7iONfL9+9xZQ0bRY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=XZ8td4lmiWfe1+3ERJOTOvtdUpoKMNd8ensgqKZ2kJfmzVAz6lRDQ2PVelVyXmfEdyA8tkMXRvAGRItCrYt2XjTvRGxSmlMAbAA0nuNy8DP8JbQLqvWJYLA9Z/61KR9AEIDk0+T8mkAcxYFpr1s7DLN7U7ZzICFq9vhLxgLHggw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=suse.com; spf=pass smtp.mailfrom=suse.com; dkim=pass (2048-bit key) header.d=suse.com header.i=@suse.com header.b=J2f43tdq; arc=none smtp.client-ip=209.85.221.50 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=suse.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=suse.com header.i=@suse.com header.b="J2f43tdq" Received: by mail-wr1-f50.google.com with SMTP id ffacd0b85a97d-3df15fdf0caso2666940f8f.0 for ; Sun, 14 Sep 2025 06:44:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=google; t=1757857473; x=1758462273; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=A/OI2IrFU0L9C9qBVFLLx/VxHOwRiUSqRs+R1r3rC/g=; b=J2f43tdqgLJcbr7iiS5teQaYfECRBvTPFOqhpmfHeoQBiKn8NwmoZ5nAm9P1tu1OTZ h8e5QJ7cbPyRA5MoEGhMwqjfTW7IGA2W/n0x/uwJ4YqBwbHJwknmdowohcVmYhcw025c ISnPWprlQ2KwSkjLjsE9j6rQvdkMo9NbUNZrw7cNUDa3uNMZcauVjp2tfsDj+Ac5Kad4 aH7hd7oYTDh1mztsQPU4juICecFVHBXLdSEjT4+ME7sN9ahUzmafzP/UzxAPu2+ScPjt ls3/YyXuGKn1IL5iAoBwNMIHqc+y/6q/vTNLjDQ6uiXVVrVcFfB3+IKWRgCEcZB5u0m6 6org== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1757857473; x=1758462273; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=A/OI2IrFU0L9C9qBVFLLx/VxHOwRiUSqRs+R1r3rC/g=; b=swG05JXmOab2YkBZuRlQBm7MdfiYw1A1reyQLevJUKXh7iZs+3/50HgcbNzt+cNQJP lEmxvbyPqSYiCRw3aQsahzaxQxFlwMuBCjYG2KwbswZSdTRMku67V5VVbQJUwHq+AY4C qPW/UcTp2KqatVXv2Ba5Ifu666frXbqQ/XfzTh801JLpK0ZdxMUB+Vlni02Kz5fwndO7 WvfJ1UFFPLLL4Kk6nRl/NtniYmTiIbSnpD7YvhkREleGLpwXlwto6mki4l2aMkYIk746 i5J6ciE3Qb8KtGKFbFN4w0/APeQ1ThqVoFw0G2TV6k+YauApUMRfR4D3kXZnQYj9yxFr cXXw== X-Gm-Message-State: AOJu0YyQBNz2E7kCx8ety7TTgHwEl7EYwWeYqQR3PpsSpIdQDuyMfBhE ZkH5pZohEY83VSaYH9nv0f51iBEGBZzECrpmc1pky4CiGGSAsV+udCg4dspfS85osMQFAAaFptv A3X6iQE8= X-Gm-Gg: ASbGncuTjnyWAQ8erFwTzQUZwPl5rOsuhByy5bI/QblfjXQnJXEjI0htpffdL6NouLo qwQSKJDaDklOtIIFLa8RSIlC8niDKacoOEc2GUkUmPXDXSXlb3UGEWMQYvYL5Kd+zmPpqo4H4Zh qpex5IGUMdEXr1y+3R+Bso3RXiLoIn6EeH0y9uaCXl7ySf9AWTX0TZo6AM6V/Pza0wTmbX8/8au fYqrjtoUTcfYP0jF19MUPIxCMlTkcX3wvlPjC0dEsGWjVDmn/G7URINbdqnzax+Vzyc8e5kjNwh XatEQqx44g/BAWjWdfFJsYLeKdghE/cY0aD8qLZMZk5PAt1vssu9c0UInmaco4ixintzX1/Xi1r uUp/FLvACqsUJ36rUgU3W/5WckWiXu92DnT67BCt+6KI825Q= X-Google-Smtp-Source: AGHT+IF3YfYKMBWsgTXNij7jgiY24DXO3RTVsSksMok16uzg//yaJeb+az/gY7raTFA3vyXOAItHsQ== X-Received: by 2002:a05:6000:61e:b0:3e7:4414:794b with SMTP id ffacd0b85a97d-3e765a018a5mr7370811f8f.50.1757857472960; Sun, 14 Sep 2025 06:44:32 -0700 (PDT) Received: from localhost.localdomain ([2a00:6d43:105:c401:e307:1a37:2e76:ce91]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3e86602a7d5sm6318876f8f.62.2025.09.14.06.44.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 14 Sep 2025 06:44:32 -0700 (PDT) From: Marco Crivellari To: linux-kernel@vger.kernel.org Cc: Tejun Heo , Lai Jiangshan , Frederic Weisbecker , Sebastian Andrzej Siewior , Marco Crivellari , Michal Hocko Subject: [PATCH v2 1/1] workqueue: WQ_PERCPU added to alloc_workqueue users Date: Sun, 14 Sep 2025 15:44:26 +0200 Message-ID: <20250914134426.43269-2-marco.crivellari@suse.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20250914134426.43269-1-marco.crivellari@suse.com> References: <20250914134426.43269-1-marco.crivellari@suse.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Currently if a user enqueue a work item using schedule_delayed_work() the used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to schedule_work() that is using system_wq and queue_work(), that makes use again of WORK_CPU_UNBOUND. This lack of consistentcy cannot be addressed without refactoring the API. alloc_workqueue() treats all queues as per-CPU by default, while unbound workqueues must opt-in via WQ_UNBOUND. This default is suboptimal: most workloads benefit from unbound queues, allowing the scheduler to place worker threads where they=E2=80=99re needed= and reducing noise when CPUs are isolated. This patch adds a new WQ_PERCPU flag to explicitly request the use of the per-CPU behavior. Both flags coexist for one release cycle to allow callers to transition their calls. Once migration is complete, WQ_UNBOUND can be removed and unbound will become the implicit default. With the introduction of the WQ_PERCPU flag (equivalent to !WQ_UNBOUND), any alloc_workqueue() caller that doesn=E2=80=99t explicitly specify WQ_UNB= OUND must now use WQ_PERCPU. All existing users have been updated accordingly. Suggested-by: Tejun Heo Signed-off-by: Marco Crivellari --- include/linux/workqueue.h | 4 ++-- kernel/workqueue.c | 20 ++++++++++---------- 2 files changed, 12 insertions(+), 12 deletions(-) diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h index 45d5dd470ff6..70db0acf74fc 100644 --- a/include/linux/workqueue.h +++ b/include/linux/workqueue.h @@ -410,7 +410,7 @@ enum wq_flags { __WQ_LEGACY =3D 1 << 18, /* internal: create*_workqueue() */ =20 /* BH wq only allows the following flags */ - __WQ_BH_ALLOWS =3D WQ_BH | WQ_HIGHPRI, + __WQ_BH_ALLOWS =3D WQ_BH | WQ_HIGHPRI | WQ_PERCPU, }; =20 enum wq_consts { @@ -570,7 +570,7 @@ alloc_workqueue_lockdep_map(const char *fmt, unsigned i= nt flags, int max_active, alloc_workqueue(fmt, WQ_UNBOUND | __WQ_ORDERED | (flags), 1, ##args) =20 #define create_workqueue(name) \ - alloc_workqueue("%s", __WQ_LEGACY | WQ_MEM_RECLAIM, 1, (name)) + alloc_workqueue("%s", __WQ_LEGACY | WQ_MEM_RECLAIM | WQ_PERCPU, 1, (name)) #define create_freezable_workqueue(name) \ alloc_workqueue("%s", __WQ_LEGACY | WQ_FREEZABLE | WQ_UNBOUND | \ WQ_MEM_RECLAIM, 1, (name)) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index c6b79b3675c3..5a1cb3026b31 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -7802,22 +7802,22 @@ void __init workqueue_init_early(void) ordered_wq_attrs[i] =3D attrs; } =20 - system_wq =3D alloc_workqueue("events", 0, 0); - system_percpu_wq =3D alloc_workqueue("events", 0, 0); - system_highpri_wq =3D alloc_workqueue("events_highpri", WQ_HIGHPRI, 0); - system_long_wq =3D alloc_workqueue("events_long", 0, 0); + system_wq =3D alloc_workqueue("events", WQ_PERCPU, 0); + system_percpu_wq =3D alloc_workqueue("events", WQ_PERCPU, 0); + system_highpri_wq =3D alloc_workqueue("events_highpri", + WQ_HIGHPRI | WQ_PERCPU, 0); + system_long_wq =3D alloc_workqueue("events_long", WQ_PERCPU, 0); system_unbound_wq =3D alloc_workqueue("events_unbound", WQ_UNBOUND, WQ_MA= X_ACTIVE); system_dfl_wq =3D alloc_workqueue("events_unbound", WQ_UNBOUND, WQ_MAX_AC= TIVE); system_freezable_wq =3D alloc_workqueue("events_freezable", - WQ_FREEZABLE, 0); + WQ_FREEZABLE | WQ_PERCPU, 0); system_power_efficient_wq =3D alloc_workqueue("events_power_efficient", - WQ_POWER_EFFICIENT, 0); + WQ_POWER_EFFICIENT | WQ_PERCPU, 0); system_freezable_power_efficient_wq =3D alloc_workqueue("events_freezable= _pwr_efficient", - WQ_FREEZABLE | WQ_POWER_EFFICIENT, - 0); - system_bh_wq =3D alloc_workqueue("events_bh", WQ_BH, 0); + WQ_FREEZABLE | WQ_POWER_EFFICIENT | WQ_PERCPU, 0); + system_bh_wq =3D alloc_workqueue("events_bh", WQ_BH | WQ_PERCPU, 0); system_bh_highpri_wq =3D alloc_workqueue("events_bh_highpri", - WQ_BH | WQ_HIGHPRI, 0); + WQ_BH | WQ_HIGHPRI | WQ_PERCPU, 0); BUG_ON(!system_wq || !system_percpu_wq|| !system_highpri_wq || !system_lo= ng_wq || !system_unbound_wq || !system_freezable_wq || !system_dfl_wq || !system_power_efficient_wq || --=20 2.51.0