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.

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

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

> 
> 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
> 

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
>>

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
> > > 
> 

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.
> 
> 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

If WRITE is supported then FLUSH is also required so that written data
can be persisted without falling back to another API.

> 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

This iodepth=8 (submission/completion batching 4) result surprised me
because the io_uring calls are already batched but there is still a 4
microsecond improvement per request.

I was expecting to see less improvement when iodepth is increased
because the syscall, io_uring, and some block layer cost is amortized
thanks to batching and block plugging.

Is the virtio-blk driver submitting 4 requests at a time for both
passthru and block? I wonder if something else is going on here.

> 
> =======
> 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
>