Re: [PATCH] io_uring: get rid of intermediate aux cqe caches

[Pavel Begunkov <asml.silence@gmail.com>]

On 2/29/24 18:03, David Wei wrote:
> On 2024-02-29 16:36, Pavel Begunkov wrote:
>> With defer taskrun we store aux cqes into a cache array and then flush
>> into the CQ, and we also maintain the ordering so aux cqes are flushed
>> before request completions. Why do we need the cache instead of pushing
>> them directly? We acutally don't, so let's kill it.
>>
>> One nuance is synchronisation -- the path we touch here is only for
>> DEFER_TASKRUN and guaranteed to be executed in the task context, and
>> all cqe posting is serialised by that. We also don't need locks because
>> of that, see __io_cq_lock().
> 
> Overall the change looks good to me. Are there any tests that check
> corner cases for multishot recv() CQE ordering?

In short, recv-multishot.c:test_enobuf() should do

And it's pretty safe, we want aux cqes first -- we get them
first. They're posted immediately, and it's hard to imagine
it to be any earlier, i.e. posting before anyone even asked
to post them.

-- 
Pavel Begunkov