linux-kernel - [PATCH 3/5] hfi1: WQ_PERCPU added to alloc

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Message-ID: <20251101163121.78400-4-marco.crivellari@suse.com>
Date: Sat,  1 Nov 2025 17:31:13 +0100
From: Marco Crivellari <marco.crivellari@...e.com>
To: linux-kernel@...r.kernel.org,
	linux-rdma@...r.kernel.org
Cc: Tejun Heo <tj@...nel.org>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Frederic Weisbecker <frederic@...nel.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Marco Crivellari <marco.crivellari@...e.com>,
	Michal Hocko <mhocko@...e.com>,
	Jason Gunthorpe <jgg@...pe.ca>,
	Leon Romanovsky <leon@...nel.org>,
	Dennis Dalessandro <dennis.dalessandro@...nelisnetworks.com>
Subject: [PATCH 3/5] hfi1: WQ_PERCPU added to alloc_workqueue users

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’re 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’t explicitly specify WQ_UNBOUND
must now use WQ_PERCPU.

Once migration is complete, WQ_UNBOUND can be removed and unbound will
become the implicit default.

CC: Dennis Dalessandro <dennis.dalessandro@...nelisnetworks.com>
Suggested-by: Tejun Heo <tj@...nel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@...e.com>
---
 drivers/infiniband/hw/hfi1/init.c | 4 ++--
 drivers/infiniband/hw/hfi1/opfn.c | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/infiniband/hw/hfi1/init.c b/drivers/infiniband/hw/hfi1/init.c
index b35f92e7d865..e4aef102dac0 100644
--- a/drivers/infiniband/hw/hfi1/init.c
+++ b/drivers/infiniband/hw/hfi1/init.c
@@ -745,8 +745,8 @@ static int create_workqueues(struct hfi1_devdata *dd)
 			ppd->hfi1_wq =
 				alloc_workqueue(
 				    "hfi%d_%d",
-				    WQ_SYSFS | WQ_HIGHPRI | WQ_CPU_INTENSIVE |
-				    WQ_MEM_RECLAIM,
+				    WQ_SYSFS | WQ_HIGHPRI | WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM |
+				    WQ_PERCPU,
 				    HFI1_MAX_ACTIVE_WORKQUEUE_ENTRIES,
 				    dd->unit, pidx);
 			if (!ppd->hfi1_wq)
diff --git a/drivers/infiniband/hw/hfi1/opfn.c b/drivers/infiniband/hw/hfi1/opfn.c
index 370a5a8eaa71..6e0e3458d202 100644
--- a/drivers/infiniband/hw/hfi1/opfn.c
+++ b/drivers/infiniband/hw/hfi1/opfn.c
@@ -305,8 +305,8 @@ void opfn_trigger_conn_request(struct rvt_qp *qp, u32 bth1)
 int opfn_init(void)
 {
 	opfn_wq = alloc_workqueue("hfi_opfn",
-				  WQ_SYSFS | WQ_HIGHPRI | WQ_CPU_INTENSIVE |
-				  WQ_MEM_RECLAIM,
+				  WQ_SYSFS | WQ_HIGHPRI | WQ_CPU_INTENSIVE | WQ_MEM_RECLAIM |
+				  WQ_PERCPU,
 				  HFI1_MAX_ACTIVE_WORKQUEUE_ENTRIES);
 	if (!opfn_wq)
 		return -ENOMEM;
-- 
2.51.0