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Wed, 12 Nov 2025 04:01:33 -0800 (PST) Received: from linux.fritz.box ([2a00:6d43:105:c401:e307:1a37:2e76:ce91]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-42ac6794f6esm38158832f8f.41.2025.11.12.04.01.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 Nov 2025 04:01:33 -0800 (PST) From: Marco Crivellari To: linux-kernel@vger.kernel.org, linux1394-devel@lists.sourceforge.net Cc: Tejun Heo , Lai Jiangshan , Frederic Weisbecker , Sebastian Andrzej Siewior , Marco Crivellari , Michal Hocko , Takashi Sakamoto Subject: [PATCH v2] firewire: core: add WQ_UNBOUND to alloc_workqueue users Date: Wed, 12 Nov 2025 13:01:25 +0100 Message-ID: <20251112120125.124578-1-marco.crivellari@suse.com> X-Mailer: git-send-email 2.51.1 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 enqueues 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 consistency 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 continues the effort to refactor workqueue APIs, which began with the introduction of new workqueues and a new alloc_workqueue flag in: commit 128ea9f6ccfb ("workqueue: Add system_percpu_wq and system_dfl_wq") commit 930c2ea566af ("workqueue: Add new WQ_PERCPU flag") This change adds the WQ_UNBOUND flag to explicitly request alloc_workqueue() to be unbound, because this specific workload has no benefit being per-cpu. 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. Once migration is complete, WQ_UNBOUND can be removed and unbound will become the implicit default. Suggested-by: Tejun Heo Signed-off-by: Marco Crivellari --- Changes in v2: - This workload benefit from an unbound workqueue. So change WQ_PERCPU with WQ_UNBOUND_WQ. - Rebased on 6.18-rc5 --- drivers/firewire/core-transaction.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/firewire/core-transaction.c b/drivers/firewire/core-tr= ansaction.c index c65f491c54d0..a9677a8affb7 100644 --- a/drivers/firewire/core-transaction.c +++ b/drivers/firewire/core-transaction.c @@ -1437,7 +1437,8 @@ static int __init fw_core_init(void) { int ret; =20 - fw_workqueue =3D alloc_workqueue("firewire", WQ_MEM_RECLAIM, 0); + fw_workqueue =3D alloc_workqueue("firewire", WQ_MEM_RECLAIM | WQ_UNBOUND, + 0); if (!fw_workqueue) return -ENOMEM; =20 --=20 2.51.1