Re: [PATCH V8 0/8] io_uring: support sqe group and leased group kbuf

[Jens Axboe <axboe@kernel.dk>]

On 10/29/24 11:01 AM, Pavel Begunkov wrote:
> On 10/25/24 13:22, Ming Lei wrote:
>> The 1st 3 patches are cleanup, and prepare for adding sqe group.
>>
>> The 4th patch supports generic sqe group which is like link chain, but
>> allows each sqe in group to be issued in parallel and the group shares
>> same IO_LINK & IO_DRAIN boundary, so N:M dependency can be supported with
>> sqe group & io link together.
>>
>> The 5th & 6th patches supports to lease other subsystem's kbuf to
>> io_uring for use in sqe group wide.
>>
>> The 7th patch supports ublk zero copy based on io_uring sqe group &
>> leased kbuf.
>>
>> Tests:
>>
>> 1) pass liburing test
>> - make runtests
>>
>> 2) write/pass sqe group test case and sqe provide buffer case:
>>
>> https://github.com/ming1/liburing/tree/uring_group
>>
>> - covers related sqe flags combination and linking groups, both nop and
>> one multi-destination file copy.
>>
>> - cover failure handling test: fail leader IO or member IO in both single
>>    group and linked groups, which is done in each sqe flags combination
>>    test
>>
>> - cover io_uring with leased group kbuf by adding ublk-loop-zc
> 
> To make my position clear, I think the table approach will turn
> much better API-wise if the performance suffices, and we can only know
> that experimentally. I tried that idea with sockets back then, and it
> was looking well. It'd be great if someone tries to implement and
> compare it, though I don't believe I should be trying it, so maybe Ming
> or Jens can, especially since Jens already posted a couple series for
> problems standing in the way, i.e global rsrc nodes and late buffer
> binding. In any case, I'm not opposing to the series if Jens decides to
> merge it.

With the rsrc node stuff sorted out, I was thinking last night that I
should take another look at this. While that work was (mostly) done
because of the lingering closes, it does nicely enable ephemeral buffers
too.

I'll take a stab at it... While I would love to make progress on this
feature proposed in this series, it's arguably more important to do it
in such a way that we can live with it, long term.

-- 
Jens Axboe