Re: [PATCH 2/2] io_uring: switch local task_work to a mpscq

On 6/11/26 7:14 PM, Caleb Sander Mateos wrote:
> This is great stuff! I had also observed these hotspots on a ublk
> workload. Since incoming ublk requests post task work to the ublk
> server's io_urings and completed ublk requests post task work to the
> client's io_urings, there is significant cross-CPU contention on the
> task work queues.

Glad you like it! Once I post v2 tomorrow, perhaps you can try and run
some tests with and without and see how it does for you?

>> @@ -185,55 +183,47 @@ void io_req_local_work_add(struct io_kiocb *req, unsigned flags)
>>
>>         guard(rcu)();
> 
> Is the RCU guard still required now that a work list element can't be
> accessed after the consumer has popped it?

It's actually not. Might need the :

	if (prev == &ctx->work_list.stub) {
		io_ctx_mark_taskrun(ctx);

parts to just grab it in there, as lower down we'd still need it. But
the task_work part itself should not. I'll make that change.

Thanks for the reviews!

-- 
Jens Axboe