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RDMA/core: 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.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
Link: https://patch.msgid.link/20251101163121.78400-3-marco.crivellari@suse.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>
This commit is contained in:
Marco Crivellari 2025-11-01 17:31:12 +01:00 committed by Leon Romanovsky
parent f673fb3449
commit e60c5583b6
2 changed files with 3 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
drivers/infiniband/core/cm.c
View File

@ -4517,7 +4517,7 @@ static int __init ib_cm_init(void)
get_random_bytes(&cm.random_id_operand, sizeof cm.random_id_operand);
INIT_LIST_HEAD(&cm.timewait_list);
cm.wq = alloc_workqueue("ib_cm", 0, 1);
cm.wq = alloc_workqueue("ib_cm", WQ_PERCPU, 1);
if (!cm.wq) {
ret = -ENOMEM;
goto error2;

4
drivers/infiniband/core/device.c
View File

@ -3021,7 +3021,7 @@ static int __init ib_core_init(void)
{
int ret = -ENOMEM;
ib_wq = alloc_workqueue("infiniband", 0, 0);
ib_wq = alloc_workqueue("infiniband", WQ_PERCPU, 0);
if (!ib_wq)
return -ENOMEM;
@ -3031,7 +3031,7 @@ static int __init ib_core_init(void)
goto err;
ib_comp_wq = alloc_workqueue("ib-comp-wq",
WQ_HIGHPRI | WQ_MEM_RECLAIM | WQ_SYSFS, 0);
WQ_HIGHPRI | WQ_MEM_RECLAIM | WQ_SYSFS | WQ_PERCPU, 0);
if (!ib_comp_wq)
goto err_unbound;