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

[Ferry Meng <mengferry@linux.alibaba.com>]

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*.


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
>>