Re: [PATCH V6 0/8] io_uring: support sqe group and provide group kbuf

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

Hello Pavel, Jens and Guys,

On Thu, Sep 12, 2024 at 06:49:20PM +0800, Ming Lei wrote:
> Hello,
> 
> 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. sqe group changes nothing on
> IOSQE_IO_LINK.
> 
> The 5th 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 6th & 7th patches supports providing sqe group buffer via the sqe
> group variant.
> 
> The 8th patch supports ublk zero copy based on io_uring providing sqe
> group buffer.
> 
> Tests:
> 
> 1) pass liburing test
> - make runtests
> 
> 2) write/pass sqe group test case and sqe provide buffer case:
> 
> https://github.com/axboe/liburing/compare/master...ming1:liburing:sqe_group_v3
> 
> https://github.com/ming1/liburing/tree/sqe_group_v3
> 
> - 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
> 
> - covers IORING_PROVIDE_GROUP_KBUF by adding ublk-loop-zc
> 
> 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_v3
> 	make test T=loop/009:nbd/061	#ublk zc tests
> 
> When running 64KB/512KB block size test on ublk-loop('ublk add -t loop --buffered_io -f $backing'),
> it is observed that perf is doubled.
> 
> 
> V6:
> 	- follow Pavel's suggestion to disallow IOSQE_CQE_SKIP_SUCCESS &
> 	  LINK_TIMEOUT
> 	- kill __io_complete_group_member() (Pavel)
> 	- simplify link failure handling (Pavel)
> 	- move members' queuing out of completion lock (Pavel)
> 	- cleanup group io complete handler
> 	- add more comment
> 	- add ublk zc into liburing test for covering
> 	  IOSQE_SQE_GROUP & IORING_PROVIDE_GROUP_KBUF 

Any comments on V6? So that I may address them in next version since
v6 has small conflict with mainline.


thanks,
Ming