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Tue, 04 Nov 2025 03:25:46 -0800 (PST) Received: from linux ([2a00:6d43:105:c401:e307:1a37:2e76:ce91]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b723d6f33aesm184101266b.19.2025.11.04.03.25.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 04 Nov 2025 03:25:45 -0800 (PST) From: Marco Crivellari To: linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org Cc: Tejun Heo , Lai Jiangshan , Frederic Weisbecker , Sebastian Andrzej Siewior , Marco Crivellari , Michal Hocko , Christoph Hellwig , Sagi Grimberg , Chaitanya Kulkarni Subject: [PATCH 2/3] nvme: add WQ_PERCPU to alloc_workqueue users Date: Tue, 4 Nov 2025 12:25:27 +0100 Message-ID: <20251104112535.139450-3-marco.crivellari@suse.com> X-Mailer: git-send-email 2.51.1 In-Reply-To: <20251104112535.139450-1-marco.crivellari@suse.com> References: <20251104112535.139450-1-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 change adds a new WQ_PERCPU flag to explicitly request alloc_workqueue= () to be per-cpu when WQ_UNBOUND has not been specified. This patch continues the effort to refactor worqueue APIs, which has begun with the change introducing new workqueues and a new alloc_workqueue flag: commit 128ea9f6ccfb ("workqueue: Add system_percpu_wq and system_dfl_wq") commit 930c2ea566af ("workqueue: Add new WQ_PERCPU flag") 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 --- drivers/nvme/target/core.c | 5 +++-- drivers/nvme/target/tcp.c | 2 +- 2 files changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c index 5d7d483bfbe3..ae8e903b55ad 100644 --- a/drivers/nvme/target/core.c +++ b/drivers/nvme/target/core.c @@ -1943,12 +1943,13 @@ static int __init nvmet_init(void) if (!nvmet_bvec_cache) return -ENOMEM; =20 - zbd_wq =3D alloc_workqueue("nvmet-zbd-wq", WQ_MEM_RECLAIM, 0); + zbd_wq =3D alloc_workqueue("nvmet-zbd-wq", WQ_MEM_RECLAIM | WQ_PERCPU, + 0); if (!zbd_wq) goto out_destroy_bvec_cache; =20 buffered_io_wq =3D alloc_workqueue("nvmet-buffered-io-wq", - WQ_MEM_RECLAIM, 0); + WQ_MEM_RECLAIM | WQ_PERCPU, 0); if (!buffered_io_wq) goto out_free_zbd_work_queue; =20 diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c index 470bf37e5a63..fa7a56626bcc 100644 --- a/drivers/nvme/target/tcp.c +++ b/drivers/nvme/target/tcp.c @@ -2198,7 +2198,7 @@ static int __init nvmet_tcp_init(void) int ret; =20 nvmet_tcp_wq =3D alloc_workqueue("nvmet_tcp_wq", - WQ_MEM_RECLAIM | WQ_HIGHPRI, 0); + WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_PERCPU, 0); if (!nvmet_tcp_wq) return -ENOMEM; =20 --=20 2.51.1