Can't setup io_uring for buffered IO

Can't setup io_uring for buffered IO

[Ming Lei]

Hello Guys,

I tried to use the following script to run buffered io with io_uring,
but looks it always complains with 'Operation not supported', and any
idea to make it working?

++ /root/git/fio/fio --readonly --name=onessd --filename=/dev/nvme0n1 --filesize=16m --rw=randread --bs=4k --direct=0 --overwrite=0 --numjobs=1 --iodepth=1 --time_based=1 --runtime=1 --ioengine=io_uring --registerfiles --fixedbufs --hipri=1 --gtod_reduce=1 --group_reporting
onessd: (g=0): rw=randread, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=io_uring, iodepth=1
fio-3.25-229-gdf9e8
Starting 1 process
fio: io_u error on file /dev/nvme0n1: Operation not supported: read offset=1011712, buflen=4096
fio: pid=3278, err=95/file:io_u.c:1841, func=io_u error, error=Operation not supported

onessd: (groupid=0, jobs=1): err=95 (file:io_u.c:1841, func=io_u error, error=Operation not supported): pid=3278: Mon Aug 16 12:01:17 2021



Thanks,
Ming

Re: Can't setup io_uring for buffered IO

[Ming Lei]

On Mon, Aug 16, 2021 at 08:02:27PM +0800, Ming Lei wrote:
> Hello Guys,
> 
> I tried to use the following script to run buffered io with io_uring,
> but looks it always complains with 'Operation not supported', and any
> idea to make it working?
> 
> ++ /root/git/fio/fio --readonly --name=onessd --filename=/dev/nvme0n1 --filesize=16m --rw=randread --bs=4k --direct=0 --overwrite=0 --numjobs=1 --iodepth=1 --time_based=1 --runtime=1 --ioengine=io_uring --registerfiles --fixedbufs --hipri=1 --gtod_reduce=1 --group_reporting
> onessd: (g=0): rw=randread, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=io_uring, iodepth=1
> fio-3.25-229-gdf9e8
> Starting 1 process
> fio: io_u error on file /dev/nvme0n1: Operation not supported: read offset=1011712, buflen=4096
> fio: pid=3278, err=95/file:io_u.c:1841, func=io_u error, error=Operation not supported
> 
> onessd: (groupid=0, jobs=1): err=95 (file:io_u.c:1841, func=io_u error, error=Operation not supported): pid=3278: Mon Aug 16 12:01:17 2021

Just figured out that --hipri can't be applied for buffered IO.

-- 
Ming

Re: Can't setup io_uring for buffered IO

[Jens Axboe]

On 8/16/21 8:50 AM, Ming Lei wrote:
> On Mon, Aug 16, 2021 at 08:02:27PM +0800, Ming Lei wrote:
>> Hello Guys,
>>
>> I tried to use the following script to run buffered io with io_uring,
>> but looks it always complains with 'Operation not supported', and any
>> idea to make it working?
>>
>> ++ /root/git/fio/fio --readonly --name=onessd --filename=/dev/nvme0n1 --filesize=16m --rw=randread --bs=4k --direct=0 --overwrite=0 --numjobs=1 --iodepth=1 --time_based=1 --runtime=1 --ioengine=io_uring --registerfiles --fixedbufs --hipri=1 --gtod_reduce=1 --group_reporting
>> onessd: (g=0): rw=randread, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=io_uring, iodepth=1
>> fio-3.25-229-gdf9e8
>> Starting 1 process
>> fio: io_u error on file /dev/nvme0n1: Operation not supported: read offset=1011712, buflen=4096
>> fio: pid=3278, err=95/file:io_u.c:1841, func=io_u error, error=Operation not supported
>>
>> onessd: (groupid=0, jobs=1): err=95 (file:io_u.c:1841, func=io_u error, error=Operation not supported): pid=3278: Mon Aug 16 12:01:17 2021
> 
> Just figured out that --hipri can't be applied for buffered IO.

Yes, and we may want to catch that in fio setup. But hipri (polled IO) is only
available with O_DIRECT.

-- 
Jens Axboe