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 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 --- kernel/bpf/cgroup.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c index b8699ec4d766..f3da9400c178 100644 --- a/kernel/bpf/cgroup.c +++ b/kernel/bpf/cgroup.c @@ -34,7 +34,8 @@ static struct workqueue_struct *cgroup_bpf_destroy_wq; static int __init cgroup_bpf_wq_init(void) { - cgroup_bpf_destroy_wq = alloc_workqueue("cgroup_bpf_destroy", 0, 1); + cgroup_bpf_destroy_wq = alloc_workqueue("cgroup_bpf_destroy", + WQ_PERCPU, 1); if (!cgroup_bpf_destroy_wq) panic("Failed to alloc workqueue for cgroup bpf destroy.\n"); return 0; -- 2.51.0