Hello, On Thu, Dec 03, 2020 at 06:28:41PM +0800, Hillf Danton wrote: > + new_cpu = cpumask_any_and_distribute(wq_unbound_cpumask, > cpu_online_mask); > + if (new_cpu < nr_cpu_ids) > + return new_cpu; > + else > + return cpu; > } > > static void __queue_work(int cpu, struct workqueue_struct *wq, > @@ -1554,7 +1546,7 @@ static int workqueue_select_cpu_near(int > return cpu; > > /* Use "random" otherwise know as "first" online CPU of node */ > - cpu = cpumask_any_and(cpumask_of_node(node), cpu_online_mask); > + cpu = cpumask_any_and_distribute(cpumask_of_node(node), > cpu_online_mask);
This looks generally okay but I think there's a real risk of different cpumasks interfering with cpu selection. e.g. imagine a cpu issuing work items to two unbound workqueues consecutively, one numa-bound, the other not. The above change will basically confine the !numa one to the numa node. I think the right thing to do here is expanding the cpumask_any_and_distribute() so that the user can provide its own cursor similar to what we do with ratelimits. Thanks. -- tejun
