linux-kernel - Re: [RFC 0/2] optimise local-tw task resheduling

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Message-ID: <c433f8cf-57dc-52c9-9959-f6a21297d1b0@kernel.dk>
Date:   Mon, 13 Mar 2023 08:16:51 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Pavel Begunkov <asml.silence@...il.com>, io-uring@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [RFC 0/2] optimise local-tw task resheduling

On 3/12/23 9:45?PM, Pavel Begunkov wrote:
>>>> Didn't take a closer look just yet, but I grok the concept. One
>>>> immediate thing I'd want to change is the FACILE part of it. Let's call
>>>> it something a bit more straightforward, perhaps LIGHT? Or LIGHTWEIGHT?
>>>
>>> I don't really care, will change, but let me also ask why?
>>> They're more or less synonyms, though facile is much less
>>> popular. Is that your reasoning?
>>
>> Yep, it's not very common and the name should be self-explanatory
>> immediately for most people.
> 
> That's exactly the problem. Someone will think that it's
> like normal tw but "better" and blindly apply it. Same happened
> before with priority tw lists.

But the way to fix that is not through obscure naming, it's through
better and more frequent review. Naming is hard, but naming should be
basically self-explanatory in terms of why it differs from not setting
that flag. LIGHTWEIGHT and friends isn't great either, maybe it should
just be explicit in that this task_work just posts a CQE and hence it's
pointless to wake the task to run it unless it'll then meet the criteria
of having that task exit its wait loop as it now has enough CQEs
available. IO_UF_TWQ_CQE_POST or something like that. Then if it at some
point gets modified to also encompass different types of task_work that
should not cause wakes, then it can change again. Just tossing
suggestions out there...

-- 
Jens Axboe