On 10/16/20 5:49 AM, Stefan Metzmacher wrote: > Hi Jens, > >> Thanks for sending this, very interesting! As per this email, I took a >> look at the NUMA bindings. If you can, please try this one-liner below. >> I'd be interested to know if that removes the fluctuations you're seeing >> due to bad locality. >> >> Looks like kthread_create_on_node() doesn't actually do anything (at >> least in terms of binding). >> >> >> diff --git a/fs/io-wq.c b/fs/io-wq.c >> index 74b84e8562fb..7bebb198b3df 100644 >> --- a/fs/io-wq.c >> +++ b/fs/io-wq.c >> @@ -676,6 +676,7 @@ static bool create_io_worker(struct io_wq *wq, struct io_wqe *wqe, int index) >> kfree(worker); >> return false; >> } >> + kthread_bind_mask(worker->task, cpumask_of_node(wqe->node)); >> >> raw_spin_lock_irq(&wqe->lock); >> hlist_nulls_add_head_rcu(&worker->nulls_node, &wqe->free_list); >> > > I no longer have access to that system, but I guess it will help, thanks! I queued up it when I sent it out, and it'll go into stable as well. I since verified on NUMA here that it does the right thing, and that things weren't affinitized properly before. So pretty confident that it will indeed solve this issue! > With this: > > worker->task = kthread_create_on_node(io_wqe_worker, worker, wqe->node, > "io_wqe_worker-%d/%d", index, wqe->node); > > I see only "io_wqe_worker-0" and "io_wqe_worker-1" in top, without '/0' or '/1' at the end, > this is because set_task_comm() truncates to 15 characters. > > As developer I think 'io_wqe' is really confusing, just from reading I thought it > means "work queue entry", but it's a per numa node worker pool container... > 'struct io_wq_node *wqn' would be easier to understand for me... > > Would it make sense to give each io_wq a unique identifier and use names like this: > (fdinfo of the io_uring fd could also include the io_wq id) > > "io_wq-%u-%u%c", wq->id, wqn->node, index == IO_WQ_ACCT_BOUND ? 'B' : 'U') > > io_wq-500-M > io_wq-500-0B > io_wq-500-0B > io_wq-500-1B > io_wq-500-0U > io_wq-200-M > io_wq-200-0B > io_wq-200-0B > io_wq-200-1B > io_wq-200-0U > > I'm not sure how this interacts with workers moving between bound and unbound > and maybe a worker id might also be useful (or we rely on their pid) I don't think that's too important, as it's just a snapshot in time. So it'll fluctuate based on the role of the worker. > I just found that proc_task_name() handles PF_WQ_WORKER special > and cat /proc/$pid/comm can expose something like: > kworker/u17:2-btrfs-worker-high Yep, that's how they do fancier names. It's been on my agenda for a while to do something about this, I'll try and cook something up for 5.11. -- Jens Axboe
