Re: [PATCH V3 0/9] io_uring: support sqe group and provide group kbuf

[Ming Lei <ming.lei@redhat.com>]

On Sat, May 11, 2024 at 08:12:03AM +0800, Ming Lei wrote:
> Hello,
> 
> The 1st 4 patches are cleanup, and prepare for adding sqe group.
> 
> The 5th 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. sqe group changes nothing on
> IOSQE_IO_LINK.
> 
> The 6th patch supports one variant of sqe group: allow members to depend
> on group leader, so that kernel resource lifetime can be aligned with
> group leader or group, then any kernel resource can be shared in this
> sqe group, and can be used in generic device zero copy.
> 
> The 7th & 8th patches supports providing sqe group buffer via the sqe
> group variant.
> 
> The 9th patch supports ublk zero copy based on io_uring providing sqe
> group buffer.
> 
> Tests:
> 
> 1) pass liburing test
> - make runtests
> 
> 2) write/pass two sqe group test cases:
> 
> https://github.com/axboe/liburing/compare/master...ming1:liburing:sqe_group_v2
> 
> - 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
> 
> 3) ublksrv zero copy:
> 
> ublksrv userspace implements zero copy by sqe group & provide group
> kbuf:
> 
> 	git clone https://github.com/ublk-org/ublksrv.git -b group-provide-buf_v2
> 	make test T=loop/009:nbd/061:nbd/062	#ublk zc tests
> 
> When running 64KB block size test on ublk-loop('ublk add -t loop --buffered_io -f $backing'),
> it is observed that perf is doubled.
> 
> Any comments are welcome!
> 
> V3:
> 	- add IORING_FEAT_SQE_GROUP
> 	- simplify group completion, and minimize change on io_req_complete_defer()
> 	- simplify & cleanup io_queue_group_members()
> 	- fix many failure handling issues
> 	- cover failure handling code in added liburing tests
> 	- remove RFC

Hello Jens and Pavel,

V3 should address all your comments, would you mind to take a look at
this version?

Thanks,
Ming