Hi, On Wed, 18 Dec 2019 at 19:02, Ober, Frank <frank.ober@xxxxxxxxx> wrote: > > Hi fio community, > 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. > > On 5.x kernels we see the following error trying to write the device settings>>> > -bash: echo: write error: Invalid argument Wouldn't this be better asked on the linux-block mailing list (http://vger.kernel.org/vger-lists.html#linux-block )? If you're saying "This worked in 4.20 but not in 5.0" (after all since you can see this clearly bisection is always an option for you) then a quick search (https://github.com/torvalds/linux/search?o=desc&p=2&q=%22io_poll%22&s=committer-date&type=Commits ) finds this commit - https://github.com/torvalds/linux/commit/cd19181bf9ad4b7f40f2a4e0355d052109c76529 which might have something to do with the change of behaviour... > 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 once upon a time. > But now things have changed, but none of us here in the Intel SSD group and OSS Driver team really know why. > > https://lwn.net/Articles/663543/ Note: this is just an excerpt from a mailing list post that LWN happened to highlight. See https://lore.kernel.org/lkml/1446830423-25027-1-git-send-email-axboe@xxxxxx/ for the post and its thread... > More documentation can be found here: https://stackoverflow.com/questions/55223883/echo-write-error-invalid-argument-while-setting-io-poll-for-nvme-ssd/ Isn't stackoverflow for programming questions rather than "where's a kernel option gone?" style question? Maybe https://unix.stackexchange.com/ would have been a better home? > Here is a good sample A / B test: > [global] > direct=1 > filename=/dev/nvme1n1 > log_avg_msec=500 > time_based > percentile_list=1:5:10:20:30:40:50:60:70:80:90:95:99:99.5:99.9:99.95:99.99:99.999:99.9999 > > > [rand-read-4k-qd1] > runtime=120 > bs=4K > iodepth=1 > numjobs=1 > cpus_allowed=0 > ioengine=io_uring > hipri > rw=randread > Works! > > [global] > direct=1 > filename=/dev/nvme1n1 > log_avg_msec=500 > time_based > percentile_list=1:5:10:20:30:40:50:60:70:80:90:95:99:99.5:99.9:99.95:99.99:99.999:99.9999 > > > [rand-read-4k-qd1] > runtime=120 > bs=4K > iodepth=1 > numjobs=1 > cpus_allowed=0 > ioengine=pvsync2 > hipri > rw=randread > Does not work... you do not see the CPU spin up to 100% (kernel/sys usage) on hipri with pvsync2 on a 5.x kernel. > > Why not? Glancing at https://fio.readthedocs.io/en/latest/fio_doc.html#i-o-engine-specific-parameters , hipri on the pvsync2 ioengine means something different to hipri on io_uring ioengine... > And what changed here? Just to check, do you get the same "full CPU" utilisation when you remove hipri from your pvsync job on a 4.x kernel? > Is it possible to get a new LWN article? That sounds like one for Jon Corbet (LWN.net editor) and the block maintainers but as mentioned above what you linked to was just a mailing list excerpt... > Thank you! > Frank Ober Good luck! -- Sitsofe | http://sucs.org/~sits/
