Re: [PATCH next v1 2/2] io_uring: limit local tw done

[Jens Axboe <axboe@kernel.dk>]

On 11/21/24 9:18 AM, Pavel Begunkov wrote:
> On 11/21/24 15:22, Jens Axboe wrote:
>> On 11/21/24 8:15 AM, Jens Axboe wrote:
>>> I'd rather entertain NOT using llists for this in the first place, as it
>>> gets rid of the reversing which is the main cost here. That won't change
>>> the need for a retry list necessarily, as I think we'd be better off
>>> with a lockless retry list still. But at least it'd get rid of the
>>> reversing. Let me see if I can dig out that patch... Totally orthogonal
>>> to this topic, obviously.
>>
>> It's here:
>>
>> https://lore.kernel.org/io-uring/20240326184615.458820-3-axboe@kernel.dk/
>>
>> I did improve it further but never posted it again, fwiw.
> 
> io_req_local_work_add() needs a smp_mb() after unlock, see comments,
> release/unlock doesn't do it.

Yep, current version I have adds a smp_mb__after_unlock_lock() for that.

Will do some quick testing, but then also try the double cmpxchg on top
of that if supported.

-- 
Jens Axboe