Re: [PATCH for-next 0/7] reworking io_uring's poll and internal poll

Pavel Begunkov
2021-12-17T19:41:23Z

On 12/17/21 15:02, Hao Xu wrote:
> 在 2021/12/16 上午6:08, Pavel Begunkov 写道:
>> That's mostly a bug fixing set, some of the problems are listed in 5/7.
>> The main part is 5/7, which is bulky but at this point it's hard (if
>> possible) to do anything without breaking a dozen of things on the
>> way, so I consider it necessary evil.
>> It also addresses one of two problems brought up by Eric Biggers
>> for aio, specifically poll rewait. There is no poll-free support yet.
>>
>> As a side effect it also changes performance characteristics, adding
>> extra atomics but removing io_kiocb referencing, improving rewait, etc.
>> There are also drafts on optimising locking needed for hashing, those
>> will go later.
> Great, seems now we can have per node bit lock for hash list.

Yeah, might be. One idea is to put it under mutex_lock. Interesting
what kind of performance difference it'd make, e.g. [1] but would need
some combined approach. Also was thinking for getting rid of hashing at
all for polling fixed files, may be promising, but would need some extra
bits for fixed files removal.

[1] https://github.com/isilence/linux/commit/5613ffd53141df98ae4a4a75b043b4d7ad252b2b

>> Performance measurements is a TODO, but the main goal lies in
>> correctness and maintainability.
>>
>> Pavel Begunkov (7):
>>    io_uring: remove double poll on poll update
>>    io_uring: refactor poll update
>>    io_uring: move common poll bits
>>    io_uring: kill poll linking optimisation
>>    io_uring: poll rework
>>    io_uring: single shot poll removal optimisation
>>    io_uring: use completion batching for poll rem/upd
>>
>>   fs/io_uring.c | 649 ++++++++++++++++++++++----------------------------
>>   1 file changed, 287 insertions(+), 362 deletions(-)
>>

--
Pavel Begunkov