Hi block/nvme communities, On 4.x kernels we used to be able to do: # echo 1 > /sys/block/nvme0n1/queue/io_poll And then run a polled_io job in fio with pvsync2 as our ioengine, with the hipri flag set. This is actually how we test the very best SSDs that depend on 3D xpoint media. On 5.x kernels we see the following error trying to write the device settings>>> -bash: echo: write error: Invalid argument We can reload the entire nvme module with nvme poll_queues but this is not well explained or written up anywhere? Or sorry "not found"? This is verifiable on 5.3, 5.4 kernels with fio 3.16 builds. What is the background on what has changed because Jens wrote this note back in 2015, which did work in the 4.x kernel era. But now things have changed, and there is not a new lwn article that has replaced the one here: https://lwn.net/Articles/663543/ More documentation can be found here on the confusion that exists today is here: https://stackoverflow.com/questions/55223883/echo-write-error-invalid-argument-while-setting-io-poll-for-nvme-ssd/ Can a new LWN article be written around design decisions, usage of these poll_queues? How come we cannot have a device/controller level setup of polled io today in 5.x kernels, all that exists is module based? Thank you! Frank Ober
