[v6,0/9] Implement copy offload support

Message

Nitesh Shetty Jan. 12, 2023, 11:58 a.m. UTC

The patch series covers the points discussed in November 2021 virtual
call [LSF/MM/BFP TOPIC] Storage: Copy Offload [0].
We have covered the initial agreed requirements in this patchset and
further additional features suggested by community.
Patchset borrows Mikulas's token based approach for 2 bdev
implementation.

This is on top of our previous patchset v5[1].

Overall series supports:
========================
	1. Driver
		- NVMe Copy command (single NS, TP 4065), including support
		in nvme-target (for block and file backend).

	2. Block layer
		- Block-generic copy (REQ_COPY flag), with interface
		accommodating two block-devs, and multi-source/destination
		interface
		- Emulation, when offload is natively absent
		- dm-linear support (for cases not requiring split)

	3. User-interface
		- new ioctl

	4. In-kernel user
		- dm-kcopyd

Testing
=======
	Copy offload can be tested on:
	a. QEMU: NVME simple copy (TP 4065). By setting nvme-ns
		parameters mssrl,mcl, msrc. For more info [2].
	b. Fabrics loopback.
	c. blktests[3] (tests block/032,033, nvme/046,047,048,049)

	Emuation can be tested on any device.

	Sample application to use IOCTL is present in patch desciption.
	fio[4].

Performance
===========
	With the async design of copy-emulation/offload using fio[4],
	we were  able to see the following improvements as
	compared to userspace read and write on a NVMeOF TCP setup:
	Setup1: Network Speed: 1000Mb/s
		Host PC: Intel(R) Core(TM) i7-8700 CPU @ 3.20GHz
		Target PC: AMD Ryzen 9 5900X 12-Core Processor
		block size 8k, range 1:
			635% improvement in IO BW (107 MiB/s to 787 MiB/s).
			Network utilisation drops from  97% to 14%.
		block-size 2M, range 16:
			2555% improvement in IO BW (100 MiB/s to 2655 MiB/s).
			Network utilisation drops from 89% to 0.62%.
	Setup2: Network Speed: 100Gb/s
		Server: Intel(R) Xeon(R) Gold 6240 CPU @ 2.60GHz, 72 cores
			(host and target have the same configuration)
		block-size 8k, range 1:
			6.5% improvement in IO BW (791 MiB/s to 843 MiB/s).
			Network utilisation drops from  6.75% to 0.14%.
		block-size 2M, range 16:
			15% improvement in IO BW (1027 MiB/s to 1183 MiB/s).
			Network utilisation drops from 8.42% to ~0%.
		block-size 8k, 8 ranges:
			18% drop in IO BW (from 798 MiB/s to 647 MiB/s)
			Network utilisation drops from 6.66% to 0.13%.

		At present we see drop in performance for bs 8k,16k and
		higher ranges (8, 16), so something more to check there.
	Overall, in these tests, kernel copy emulation performs better than
	userspace read+write. 

Blktests[3]
======================
	tests/block/032,033: Runs copy offload and emulation on block device.
        tests/nvme/046,047,048,049 Create a loop backed fabrics device and
        run copy offload and emulation.

Future Work
===========
        - nullblk: copy-offload emulation.
	- generic copy file range (CFR):
		We explored the possibility of using block device
		def_blk_ops, but we saw a major disadvantage for in-kernel
		users. fd is not available for in-kernel user [5].
	- loopback device copy offload support
	- upstream fio to use copy offload

	These are to be taken up after we reach consensus on the
	plumbing of current elements that are part of this series.


Additional links:
=================
	[0] https://lore.kernel.org/linux-nvme/CA+1E3rJ7BZ7LjQXXTdX+-0Edz=[e-mail]/
	[1] https://lore.kernel.org/lkml/20221130041450.GA17533@test-zns/T/
	[2] https://qemu-project.gitlab.io/qemu/system/devices/nvme.html#simple-copy
	[3] https://github.com/nitesh-shetty/blktests/tree/feat/copy_offload/v6
	[4] https://github.com/vincentkfu/fio/tree/copyoffload
	[5] https://lore.kernel.org/lkml/20221130041450.GA17533@test-zns/T/#m0e2754202fc2223e937c8e7ba3cf7336a93f97a3

Changes since v5:
=================
	- Addition of blktests (Chaitanya Kulkarni)
        - Minor fix for fabrics file backed path
        - Remove buggy zonefs copy file range implementation.

Changes since v4:
=================
	- make the offload and emulation design asynchronous (Hannes
	  Reinecke)
	- fabrics loopback support
	- sysfs naming improvements (Damien Le Moal)
	- use kfree() instead of kvfree() in cio_await_completion
	  (Damien Le Moal)
	- use ranges instead of rlist to represent range_entry (Damien
	  Le Moal)
	- change argument ordering in blk_copy_offload suggested (Damien
	  Le Moal)
	- removed multiple copy limit and merged into only one limit
	  (Damien Le Moal)
	- wrap overly long lines (Damien Le Moal)
	- other naming improvements and cleanups (Damien Le Moal)
	- correctly format the code example in description (Damien Le
	  Moal)
	- mark blk_copy_offload as static (kernel test robot)
	
Changes since v3:
=================
	- added copy_file_range support for zonefs
	- added documentation about new sysfs entries
	- incorporated review comments on v3
	- minor fixes

Changes since v2:
=================
	- fixed possible race condition reported by Damien Le Moal
	- new sysfs controls as suggested by Damien Le Moal
	- fixed possible memory leak reported by Dan Carpenter, lkp
	- minor fixes

Nitesh Shetty (9):
  block: Introduce queue limits for copy-offload support
  block: Add copy offload support infrastructure
  block: add emulation for copy
  block: Introduce a new ioctl for copy
  nvme: add copy offload support
  nvmet: add copy command support for bdev and file ns
  dm: Add support for copy offload.
  dm: Enable copy offload for dm-linear target
  dm kcopyd: use copy offload support

 Documentation/ABI/stable/sysfs-block |  36 ++
 block/blk-lib.c                      | 597 +++++++++++++++++++++++++++
 block/blk-map.c                      |   4 +-
 block/blk-settings.c                 |  24 ++
 block/blk-sysfs.c                    |  64 +++
 block/blk.h                          |   2 +
 block/ioctl.c                        |  36 ++
 drivers/md/dm-kcopyd.c               |  56 ++-
 drivers/md/dm-linear.c               |   1 +
 drivers/md/dm-table.c                |  42 ++
 drivers/md/dm.c                      |   7 +
 drivers/nvme/host/constants.c        |   1 +
 drivers/nvme/host/core.c             | 106 ++++-
 drivers/nvme/host/fc.c               |   5 +
 drivers/nvme/host/nvme.h             |   7 +
 drivers/nvme/host/pci.c              |  27 +-
 drivers/nvme/host/rdma.c             |   7 +
 drivers/nvme/host/tcp.c              |  16 +
 drivers/nvme/host/trace.c            |  19 +
 drivers/nvme/target/admin-cmd.c      |   9 +-
 drivers/nvme/target/io-cmd-bdev.c    |  79 ++++
 drivers/nvme/target/io-cmd-file.c    |  52 +++
 drivers/nvme/target/loop.c           |   6 +
 drivers/nvme/target/nvmet.h          |   2 +
 include/linux/blk_types.h            |  44 ++
 include/linux/blkdev.h               |  18 +
 include/linux/device-mapper.h        |   5 +
 include/linux/nvme.h                 |  43 +-
 include/uapi/linux/fs.h              |  27 ++
 29 files changed, 1324 insertions(+), 18 deletions(-)


base-commit: 469a89fd3bb73bb2eea628da2b3e0f695f80b7ce