[PATCH v5 00/10] Implement copy offload support

Nitesh Shetty
2022-11-23T06:14:57Z

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 v4[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
- copy_file_range for zonefs

4. In-kernel user
- dm-kcopyd
- copy_file_range in zonefs

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. zonefs copy_file_range

Emuation can be tested on any device.

Sample application to use IOCTL is present in patch desciption.
fio[3].

Performance
===========
With the async design of copy-emulation/offload using fio[3],
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.

Zonefs copy_file_range
======================
Sample tests for zonefs-tools[4]. Test 0118 and 0119 will test
basic CFR. Will raise a PR, once this series is finalized.

Future Work
===========
- nullblk: copy-offload emulation
- generic copy file range (CFR):
I did go through this, but couldn't find straight forward
way to plug in copy offload for all the cases. We are doing
detailed study, will address this future versions.
- 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=zT14mmPGMiVCzUgB33C60tbQ@mail.gmail.com/
[1] https://lore.kernel.org/lkml/20220426101241.30100-1-nj.shetty@samsung.com/
[2] https://qemu-project.gitlab.io/qemu/system/devices/nvme.html#simple-copy
[3] https://github.com/vincentkfu/fio/tree/copyoffload
[4] https://github.com/nitesh-shetty/zonefs-tools/tree/cfr

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 (10):
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
fs: add support for copy file range in zonefs

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/core.c | 106 ++++-
drivers/nvme/host/fc.c | 5 +
drivers/nvme/host/nvme.h | 7 +
drivers/nvme/host/pci.c | 28 +-
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 | 51 +++
drivers/nvme/target/loop.c | 6 +
drivers/nvme/target/nvmet.h | 2 +
fs/zonefs/super.c | 179 ++++++++
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, 1502 insertions(+), 18 deletions(-)

base-commit: e4cd8d3ff7f9efeb97330e5e9b99eeb2a68f5cf9
--
2.35.1.500.gb896f729e2