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From: Ming Lei <[email protected]>
To: Jens Axboe <[email protected]>,
	[email protected], [email protected]
Cc: Miklos Szeredi <[email protected]>,
	ZiyangZhang <[email protected]>,
	Xiaoguang Wang <[email protected]>,
	Bernd Schubert <[email protected]>,
	Pavel Begunkov <[email protected]>,
	Stefan Hajnoczi <[email protected]>
Subject: Re: [PATCH V3 00/16] io_uring/ublk: add IORING_OP_FUSED_CMD
Date: Tue, 21 Mar 2023 23:56:41 +0800	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On Tue, Mar 14, 2023 at 08:57:11PM +0800, Ming Lei wrote:
> Hello,
> 
> Add IORING_OP_FUSED_CMD, it is one special URING_CMD, which has to
> be SQE128. The 1st SQE(master) is one 64byte URING_CMD, and the 2nd
> 64byte SQE(slave) is another normal 64byte OP. For any OP which needs
> to support slave OP, io_issue_defs[op].fused_slave needs to be set as 1,
> and its ->issue() can retrieve/import buffer from master request's
> fused_cmd_kbuf. The slave OP is actually submitted from kernel, part of
> this idea is from Xiaoguang's ublk ebpf patchset, but this patchset
> submits slave OP just like normal OP issued from userspace, that said,
> SQE order is kept, and batching handling is done too.
> 
> Please see detailed design in commit log of the 2th patch, and one big
> point is how to handle buffer ownership.
> 
> With this way, it is easy to support zero copy for ublk/fuse device.
> 
> Basically userspace can specify any sub-buffer of the ublk block request
> buffer from the fused command just by setting 'offset/len'
> in the slave SQE for running slave OP. This way is flexible to implement
> io mapping: mirror, stripped, ...
> 
> The 3th & 4th patches enable fused slave support for the following OPs:
> 
> 	OP_READ/OP_WRITE
> 	OP_SEND/OP_RECV/OP_SEND_ZC
> 
> The other ublk patches cleans ublk driver and implement fused command
> for supporting zero copy.
> 
> Follows userspace code:
> 
> https://github.com/ming1/ubdsrv/tree/fused-cmd-zc-v2
> 
> All three(loop, nbd and qcow2) ublk targets have supported zero copy by passing:
> 
> 	ublk add -t [loop|nbd|qcow2] -z .... 
> 
> Basic fs mount/kernel building and builtin test are done, and also not
> observe regression on xfstest test over ublk-loop with zero copy.
> 
> Also add liburing test case for covering fused command based on miniublk
> of blktest:
> 
> https://github.com/ming1/liburing/commits/fused_cmd_miniublk
> 
> Performance improvement is obvious on memory bandwidth
> related workloads, such as, 1~2X improvement on 64K/512K BS
> IO test on loop with ramfs backing file.
> 
> Any comments are welcome!
> 
> V3:
> 	- fix build warning reported by kernel test robot
> 	- drop patch for checking fused flags on existed drivers with
> 	  ->uring_command(), which isn't necessary, since we do not do that
>       when adding new ioctl or uring command
>     - inline io_init_rq() for core code, so just export io_init_slave_req
> 	- return result of failed slave request unconditionally since REQ_F_CQE_SKIP
> 	will be cleared
> 	- pass xfstest over ublk-loop

BTW, I just wrote one ublk zero copy document, which describes technical requirement
for this feature, and explains why splice isn't good and how fused command solves it,
feel free to refer to it when working on candidate approach.

https://github.com/ming1/linux/blob/my_v6.3-io_uring_fuse_cmd_v4/Documentation/block/ublk.rst#zero-copy

Which will be included in V4.


Thanks, 
Ming


      parent reply	other threads:[~2023-03-21 15:58 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-03-14 12:57 [PATCH V3 00/16] io_uring/ublk: add IORING_OP_FUSED_CMD Ming Lei
2023-03-14 12:57 ` [PATCH V3 01/16] io_uring: increase io_kiocb->flags into 64bit Ming Lei
2023-03-14 12:57 ` [PATCH V3 02/16] io_uring: add IORING_OP_FUSED_CMD Ming Lei
2023-03-18 14:31   ` Jens Axboe
2023-03-18 15:24     ` Ming Lei
2023-03-18 16:00       ` Jens Axboe
2023-03-18 16:13       ` Ming Lei
2023-03-14 12:57 ` [PATCH V3 03/16] io_uring: support OP_READ/OP_WRITE for fused slave request Ming Lei
2023-03-14 12:57 ` [PATCH V3 04/16] io_uring: support OP_SEND_ZC/OP_RECV " Ming Lei
2023-03-14 12:57 ` [PATCH V3 05/16] block: ublk_drv: mark device as LIVE before adding disk Ming Lei
2023-03-14 12:57 ` [PATCH V3 06/16] block: ublk_drv: add common exit handling Ming Lei
2023-03-14 12:57 ` [PATCH V3 07/16] block: ublk_drv: don't consider flush request in map/unmap io Ming Lei
2023-03-14 12:57 ` [PATCH V3 08/16] block: ublk_drv: add two helpers to clean up map/unmap request Ming Lei
2023-03-14 12:57 ` [PATCH V3 09/16] block: ublk_drv: clean up several helpers Ming Lei
2023-03-14 12:57 ` [PATCH V3 10/16] block: ublk_drv: cleanup 'struct ublk_map_data' Ming Lei
2023-03-14 12:57 ` [PATCH V3 11/16] block: ublk_drv: cleanup ublk_copy_user_pages Ming Lei
2023-03-14 12:57 ` [PATCH V3 12/16] block: ublk_drv: grab request reference when the request is handled by userspace Ming Lei
2023-03-14 12:57 ` [PATCH V3 13/16] block: ublk_drv: support to copy any part of request pages Ming Lei
2023-03-14 12:57 ` [PATCH V3 14/16] block: ublk_drv: add read()/write() support for ublk char device Ming Lei
2023-03-14 12:57 ` [PATCH V3 15/16] block: ublk_drv: don't check buffer in case of zero copy Ming Lei
2023-03-14 12:57 ` [PATCH V3 16/16] block: ublk_drv: apply io_uring FUSED_CMD for supporting " Ming Lei
2023-03-16  3:13 ` [PATCH V3 00/16] io_uring/ublk: add IORING_OP_FUSED_CMD Xiaoguang Wang
2023-03-16  3:56   ` Ming Lei
2023-03-18 16:23   ` Pavel Begunkov
2023-03-18 16:39     ` Ming Lei
2023-03-21  9:17     ` Ziyang Zhang
2023-03-27 16:04       ` Pavel Begunkov
2023-03-28  1:01         ` Ming Lei
2023-03-28 11:01           ` Pavel Begunkov
2023-03-28  0:53       ` Ming Lei
2023-03-29  6:57         ` Ziyang Zhang
2023-03-29  8:52           ` Ming Lei
2023-03-25 14:15     ` Ming Lei
2023-03-17  8:14 ` Ming Lei
2023-03-18 12:59   ` Jens Axboe
2023-03-18 13:35     ` Ming Lei
2023-03-18 14:36       ` Jens Axboe
2023-03-18 15:06         ` Ming Lei
2023-03-18 16:51       ` Pavel Begunkov
2023-03-18 23:42         ` Ming Lei
2023-03-19  0:17           ` Ming Lei
2023-03-28 10:55           ` Pavel Begunkov
2023-03-28 13:01             ` Ming Lei
2023-03-29  6:59               ` Ziyang Zhang
2023-03-29 10:43               ` Pavel Begunkov
2023-03-29 11:55                 ` Ming Lei
2023-03-18 16:09 ` Jens Axboe
2023-03-18 17:01   ` Ming Lei
2023-03-21 15:56 ` Ming Lei [this message]

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