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J . Bottomley" , "Martin K . Petersen" Subject: [PATCH 4/4] scsi: scsi_transport_fc: WQ_PERCPU added to alloc_workqueue users Date: Fri, 31 Oct 2025 10:56:43 +0100 Message-ID: <20251031095643.74246-5-marco.crivellari@suse.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251031095643.74246-1-marco.crivellari@suse.com> References: <20251031095643.74246-1-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. 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 Reviewed-by: Justin Tee --- drivers/scsi/scsi_transport_fc.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/scsi/scsi_transport_fc.c b/drivers/scsi/scsi_transport= _fc.c index 3a821afee9bc..987befb02408 100644 --- a/drivers/scsi/scsi_transport_fc.c +++ b/drivers/scsi/scsi_transport_fc.c @@ -441,7 +441,8 @@ static int fc_host_setup(struct transport_container *tc= , struct device *dev, fc_host->next_vport_number =3D 0; fc_host->npiv_vports_inuse =3D 0; =20 - fc_host->work_q =3D alloc_workqueue("fc_wq_%d", 0, 0, shost->host_no); + fc_host->work_q =3D alloc_workqueue("fc_wq_%d", WQ_PERCPU, 0, + shost->host_no); if (!fc_host->work_q) return -ENOMEM; =20 @@ -3088,7 +3089,7 @@ fc_remote_port_create(struct Scsi_Host *shost, int ch= annel, =20 spin_unlock_irqrestore(shost->host_lock, flags); =20 - rport->devloss_work_q =3D alloc_workqueue("fc_dl_%d_%d", 0, 0, + rport->devloss_work_q =3D alloc_workqueue("fc_dl_%d_%d", WQ_PERCPU, 0, shost->host_no, rport->number); if (!rport->devloss_work_q) { printk(KERN_ERR "FC Remote Port alloc_workqueue failed\n"); --=20 2.51.0