Hi Daniel, Intel uses pvsync2 for QD1 testing so if you cannot use spdk or io_uring (these are the fastest ways to test a device), you can switch your engine to pvsync2 on this kernel and this will work. Here's what I tried on PCIe Gen3 system with an Optane drive and your drive. [root@fm42adsdemo001 block]# fio --bs=1M --rw=randwrite --numjobs=1 --iodepth=1 --size=10000M \ > --filename=/dev/nvme6n1 --name=mylittletest --direct=1 --fsync=1 \ > --refill_buffers --ioengine=pvsync2 --group_reporting \ > --fallocate=none --runtime=60 --time_based --hipri mylittletest: (g=0): rw=randwrite, bs=(R) 1024KiB-1024KiB, (W) 1024KiB-1024KiB, (T) 1024KiB-1024KiB, ioengine=pvsync2, iodepth=1 fio-3.24-5-g2ee2 Starting 1 process Jobs: 1 (f=1): [w(1)][100.0%][w=2048MiB/s][w=2048 IOPS][eta 00m:00s] I ran the same exact job on this mid-range Intel Xeon cpu and found io_uring only very slightly faster than pvsync2 Jobs: 1 (f=1): [w(1)][100.0%][w=2057MiB/s][w=2057 IOPS][eta 00m:00s] HTH, Frank Ober -----Original Message----- From: Jens Axboe <axboe@xxxxxxxxx> Sent: Sunday, February 14, 2021 8:50 AM To: Daniel Menzel <daniel.menzel@xxxxxxxxxxxxx>; fio@xxxxxxxxxxxxxxx Subject: Re: io_uring on CentOS8? On 2/14/21 8:17 AM, Daniel Menzel wrote: > /Somehow it seems as if I'm receiving messages from the mailing list - > but mine do not seem to get through. So I'm trying again./ > > Hi, > > currently I started testing fairly fast NVMe-drives and I for the first time I dealt with the question whether the io engine is sufficient (up till now I just the default /libaio/). I found some information on io_uring online and now tried to switch to that engine: > > fio --bs=1M --rw=randwrite --numjobs=1 --iodepth=1 --size=10000M > --filename=/dev/nvme0n1 --name=mylittletest --direct=1 --fsync=1 > --refill_buffers --ioengine=io_uring --group_reporting > --fallocate=none --runtime=60 --time_based --hipri > > But it crashes with the following information: fio: pid=2490, > err=38/file:engines/io_uring.c:699, func=io_queue_init, error=Function > not implemented > > My system: > > 1. fio-3.25 > 2. CentOS8 (Kernel 4.18.0-240.1.1.el8_3.x86_64) 3. I have installed > the packes liburing and liburing-devel > > Am I doing something wrong? You are not, but since you get -ENOSYS from the system call, that means that the kernel doesn't support io_uring. It was officially added with the 5.1 kernel, so 4.18 predates that. -- Jens Axboe
