Re: [PATCH v1 0/3] virtio-blk: add io_uring passthrough support.

[Stefan Hajnoczi <stefanha@redhat.com>]

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On Wed, Feb 26, 2025 at 07:10:36PM +0800, Ferry Meng wrote:
> 
> On 2/19/25 10:01 AM, Stefan Hajnoczi wrote:
> > On Wed, Dec 18, 2024 at 05:24:32PM +0800, Ferry Meng wrote:
> > > This patchset implements io_uring passthrough surppot in virtio-blk
> > > driver, bypass vfs and part of block layer logic, resulting in lower
> > > submit latency and increased flexibility when utilizing virtio-blk.
> > Hi,
> > What is the status of this patch series?
> > 
> > Stefan
> 
> I apologize for the delayed response. It seems that the maintainer has not
> yet provided feedback on this patch series, and I was actually waiting for
> his comments before proceeding. I have received the feedback from the other
> reviewers & have already discovered some obvious mistakes in v1 series.
> 
> 
> Although I'm occupied with other tasks recently, I expect to send out v2
> patches *in a week*.

Great. I'll review the next revision in more detail.

Thanks,
Stefan

> 
> 
> Thanks.
> 
> > > In this version, currently only supports READ/WRITE vec/no-vec operations,
> > > others like discard or zoned ops not considered in. So the userspace-related
> > > struct is not complicated.
> > > 
> > > struct virtblk_uring_cmd {
> > > 	__u32 type;
> > > 	__u32 ioprio;
> > > 	__u64 sector;
> > > 	/* above is related to out_hdr */
> > > 	__u64 data;  // user buffer addr or iovec base addr.
> > > 	__u32 data_len; // user buffer length or iovec count.
> > > 	__u32 flag;  // only contains whether a vector rw or not.
> > > };
> > > 
> > > To test this patch series, I changed fio's code:
> > > 1. Added virtio-blk support to engines/io_uring.c.
> > > 2. Added virtio-blk support to the t/io_uring.c testing tool.
> > > Link: https://github.com/jdmfr/fio
> > > 
> > > 
> > > ===========
> > > Performance
> > > ===========
> > > 
> > > Using t/io_uring-vblk, the performance of virtio-blk based on uring-cmd
> > > scales better than block device access. (such as below, Virtio-Blk with QEMU,
> > > 1-depth fio)
> > > (passthru) read: IOPS=17.2k, BW=67.4MiB/s (70.6MB/s)
> > > slat (nsec): min=2907, max=43592, avg=3981.87, stdev=595.10
> > > clat (usec): min=38, max=285,avg=53.47, stdev= 8.28
> > > lat (usec): min=44, max=288, avg=57.45, stdev= 8.28
> > > (block) read: IOPS=15.3k, BW=59.8MiB/s (62.7MB/s)
> > > slat (nsec): min=3408, max=35366, avg=5102.17, stdev=790.79
> > > clat (usec): min=35, max=343, avg=59.63, stdev=10.26
> > > lat (usec): min=43, max=349, avg=64.73, stdev=10.21
> > > 
> > > Testing the virtio-blk device with fio using 'engines=io_uring_cmd'
> > > and 'engines=io_uring' also demonstrates improvements in submit latency.
> > > (passthru) taskset -c 0 t/io_uring-vblk -b4096 -d8 -c4 -s4 -p0 -F1 -B0 -O0 -n1 -u1 /dev/vdcc0
> > > IOPS=189.80K, BW=741MiB/s, IOS/call=4/3
> > > IOPS=187.68K, BW=733MiB/s, IOS/call=4/3
> > > (block) taskset -c 0 t/io_uring-vblk -b4096 -d8 -c4 -s4 -p0 -F1 -B0 -O0 -n1 -u0 /dev/vdc
> > > IOPS=101.51K, BW=396MiB/s, IOS/call=4/3
> > > IOPS=100.01K, BW=390MiB/s, IOS/call=4/4
> > > 
> > > =======
> > > Changes
> > > =======
> > > 
> > > Changes in v1:
> > > --------------
> > > * remove virtblk_is_write() helper
> > > * fix rq_flags type definition (blk_opf_t), add REQ_ALLOC_CACHE flag.
> > > https://lore.kernel.org/io-uring/202412042324.uKQ5KdkE-lkp@intel.com/
> > > 
> > > RFC discussion:
> > > ---------------
> > > https://lore.kernel.org/io-uring/20241203121424.19887-1-mengferry@linux.alibaba.com/
> > > 
> > > Ferry Meng (3):
> > >    virtio-blk: add virtio-blk chardev support.
> > >    virtio-blk: add uring_cmd support for I/O passthru on chardev.
> > >    virtio-blk: add uring_cmd iopoll support.
> > > 
> > >   drivers/block/virtio_blk.c      | 320 +++++++++++++++++++++++++++++++-
> > >   include/uapi/linux/virtio_blk.h |  16 ++
> > >   2 files changed, 331 insertions(+), 5 deletions(-)
> > > 
> > > -- 
> > > 2.43.5
> > > 
> 

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