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

[Jens Axboe <axboe@kernel.dk>]

On 7/14/25 9:45 AM, Pavel Begunkov wrote:
> On 7/14/25 15:54, Jens Axboe wrote:
>> On 7/14/25 3:26 AM, Pavel Begunkov wrote:
>>> On 7/12/25 21:59, Jens Axboe wrote:
>>>> 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
> ...>>>> 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
>>>
>>> You know, I wrote this machinery and optimised it, I'm not saying it
>>> to just piss you off, I still need it to work well for zcrx :)
>>
>> This was not a critique of the code, it's just a generic statement on
>> the serialization around poll triggering is obviously a lot more
>> expensive than basic flag checking or setting. Every comment is not a
>> backhanded attack on someones code.
> 
> Not taken this way, it works well enough for such highly concurrent
> synchronisation.

Certainly, no complaints!

>>> Not going into details, but it's not such a simple unlocked or. And
>>> death by a thousand is never old either.
>>
>> That's obviously true, I was just trying to set expectations that a
>> single flag mask is not really a big deal. If the idea and feature was
>> fully solidified and useful, then arguing that adding a bit or is a
>> problem is nonsense.
> 
> Quite the opppsite, it should be argued about, and not because "or"
> is expensive, but because it's a write in a nuanced place.

I think that's orthogonal - should it be commented? Definitely yes. This
is sadly true for a lot of the code in there, but doesn't mean we should
add more.

But all moot so far, at least until it can move forward, if at all.

-- 
Jens Axboe