Re: [PATCH 2/3] io_uring/poll: flag request as having gone through poll wake machinery

[Jens Axboe <axboe@kernel.dk>]

On 7/12/25 5:39 AM, Pavel Begunkov wrote:
> On 7/12/25 00:59, Jens Axboe wrote:
>> No functional changes in this patch, just in preparation for being able
>> to flag completions as having completed via being triggered from poll.
>>
>> Signed-off-by: Jens Axboe <axboe@kernel.dk>
>> ---
>>   include/linux/io_uring_types.h | 3 +++
>>   io_uring/poll.c                | 1 +
>>   2 files changed, 4 insertions(+)
>>
>> diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
>> index 80a178f3d896..b56fe2247077 100644
>> --- a/include/linux/io_uring_types.h
>> +++ b/include/linux/io_uring_types.h
>> @@ -505,6 +505,7 @@ enum {
>>       REQ_F_HAS_METADATA_BIT,
>>       REQ_F_IMPORT_BUFFER_BIT,
>>       REQ_F_SQE_COPIED_BIT,
>> +    REQ_F_POLL_WAKE_BIT,
>>         /* not a real bit, just to check we're not overflowing the space */
>>       __REQ_F_LAST_BIT,
>> @@ -596,6 +597,8 @@ enum {
>>       REQ_F_IMPORT_BUFFER    = IO_REQ_FLAG(REQ_F_IMPORT_BUFFER_BIT),
>>       /* ->sqe_copy() has been called, if necessary */
>>       REQ_F_SQE_COPIED    = IO_REQ_FLAG(REQ_F_SQE_COPIED_BIT),
>> +    /* request went through poll wakeup machinery */
>> +    REQ_F_POLL_WAKE        = IO_REQ_FLAG(REQ_F_POLL_WAKE_BIT),
>>   };
>>     typedef void (*io_req_tw_func_t)(struct io_kiocb *req, io_tw_token_t tw);
>> diff --git a/io_uring/poll.c b/io_uring/poll.c
>> index c7e9fb34563d..e1950b744f3b 100644
>> --- a/io_uring/poll.c
>> +++ b/io_uring/poll.c
>> @@ -423,6 +423,7 @@ static int io_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
>>               else
>>                   req->flags &= ~REQ_F_SINGLE_POLL;
>>           }
>> +        req->flags |= REQ_F_POLL_WAKE;
> 
> Same, it's overhead for all polled requests for a not clear gain.
> Just move it to the arming function. It's also not correct to
> keep it here, if that's what you care about.

Not too worried about overhead, for an unlocked or. The whole poll
machinery is pretty intense in that regard. But yeah, do agree that just
moving it to arming would be better and more appropriate too.

I'm still a bit split on whether this makes any sense at all, 2-3 really
should be RFC.

-- 
Jens Axboe