From dadb3ebcf395ebee3626d88ac7e5e234f15bae2c Mon Sep 17 00:00:00 2001 From: Marco Crivellari Date: Sun, 14 Sep 2025 15:44:26 +0200 Subject: workqueue: WQ_PERCPU added to alloc_workqueue users MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 patch adds a new WQ_PERCPU flag to explicitly request the use of the per-CPU behavior. Both flags coexist for one release cycle to allow callers to transition their calls. Once migration is complete, WQ_UNBOUND can be removed and unbound will become the implicit default. 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. All existing users have been updated accordingly. Suggested-by: Tejun Heo Signed-off-by: Marco Crivellari Signed-off-by: Tejun Heo --- kernel/workqueue.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) (limited to 'kernel/workqueue.c') diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 90db8cf015c2..45320e27a16c 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -7828,22 +7828,22 @@ void __init workqueue_init_early(void) ordered_wq_attrs[i] = attrs; } - system_wq = alloc_workqueue("events", 0, 0); - system_percpu_wq = alloc_workqueue("events", 0, 0); - system_highpri_wq = alloc_workqueue("events_highpri", WQ_HIGHPRI, 0); - system_long_wq = alloc_workqueue("events_long", 0, 0); + system_wq = alloc_workqueue("events", WQ_PERCPU, 0); + system_percpu_wq = alloc_workqueue("events", WQ_PERCPU, 0); + system_highpri_wq = alloc_workqueue("events_highpri", + WQ_HIGHPRI | WQ_PERCPU, 0); + system_long_wq = alloc_workqueue("events_long", WQ_PERCPU, 0); system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND, WQ_MAX_ACTIVE); system_dfl_wq = alloc_workqueue("events_unbound", WQ_UNBOUND, WQ_MAX_ACTIVE); system_freezable_wq = alloc_workqueue("events_freezable", - WQ_FREEZABLE, 0); + WQ_FREEZABLE | WQ_PERCPU, 0); system_power_efficient_wq = alloc_workqueue("events_power_efficient", - WQ_POWER_EFFICIENT, 0); + WQ_POWER_EFFICIENT | WQ_PERCPU, 0); system_freezable_power_efficient_wq = alloc_workqueue("events_freezable_pwr_efficient", - WQ_FREEZABLE | WQ_POWER_EFFICIENT, - 0); - system_bh_wq = alloc_workqueue("events_bh", WQ_BH, 0); + WQ_FREEZABLE | WQ_POWER_EFFICIENT | WQ_PERCPU, 0); + system_bh_wq = alloc_workqueue("events_bh", WQ_BH | WQ_PERCPU, 0); system_bh_highpri_wq = alloc_workqueue("events_bh_highpri", - WQ_BH | WQ_HIGHPRI, 0); + WQ_BH | WQ_HIGHPRI | WQ_PERCPU, 0); BUG_ON(!system_wq || !system_percpu_wq|| !system_highpri_wq || !system_long_wq || !system_unbound_wq || !system_freezable_wq || !system_dfl_wq || !system_power_efficient_wq || -- cgit