Re: [PATCH 8/8] io_uring: enable IORING_SETUP_ATTACH_WQ to attach to SQPOLL thread too

[Jens Axboe <axboe@kernel.dk>]

On 9/7/20 10:14 AM, Jens Axboe wrote:
> On 9/7/20 2:56 AM, Xiaoguang Wang wrote:
>> 3. When it's appropriate to set ctx's IORING_SQ_NEED_WAKEUP flag? In
>> your current implementation, if a ctx is marked as SQT_IDLE, this ctx
>> will be set IORING_SQ_NEED_WAKEUP flag, but if other ctxes have work
>> to do, then io_sq_thread is still running and does not need to be
>> waken up, then a later wakeup form userspace is unnecessary. I think
>> it maybe appropriate to set IORING_SQ_NEED_WAKEUP when all ctxes have
>> no work to do, you can have a look at my attached codes:)
> 
> That's a good point, any chance I can get you to submit a patch to fix
> that up?

Something like this?

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 4bd18e01ae89..80913973337a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6747,8 +6747,6 @@ static enum sq_ret __io_sq_thread(struct io_ring_ctx *ctx,
 			goto again;
 		}
 
-		io_ring_set_wakeup_flag(ctx);
-
 		to_submit = io_sqring_entries(ctx);
 		if (!to_submit || ret == -EBUSY)
 			return SQT_IDLE;
@@ -6825,6 +6823,8 @@ static int io_sq_thread(void *data)
 			io_run_task_work();
 			cond_resched();
 		} else if (ret == SQT_IDLE) {
+			list_for_each_entry(ctx, &sqd->ctx_list, sqd_list)
+				io_ring_set_wakeup_flag(ctx);
 			schedule();
 			start_jiffies = jiffies;
 		}

-- 
Jens Axboe