Il giorno dom, 10/11/2019 alle 06.28 +0800, Ming Lei ha scritto: > Another thing we could try is to use 'none' via the following > command: > > echo none > /sys/block/sdh/queue/scheduler #suppose 'sdh' points > to the usb storage disk > > Because USB storage HBA is single hw queue, which depth is 1. This > way > should change to dispatch IO in the order of bio submission. > > Andrea, could you switch io scheduler to none and update us if > difference > can be made? Using the new kernel, there is indeed a difference because the time to copy a file is 1800 seconds with [mq-deadline], and 340 seconds with [none]. But that is still far away from the old kernel, which performs the copy of the same file in 76 seconds. Side notes: - The numbers above are average values calculated on 100 trials for each different situation. As previously noticed on this thread, with the new kernel the times are also very different among the different trials in the same situation. With the old kernel the standard deviation on the times in a set of 100 trials is much smaller (to give some mean/sigma values: m=1800->s=530; m=340->s=131; m=76->s=13; ). - The size of the transferred file has been 1GB in these trials. Smaller files don't always give appreciable differences, but if you want I can also provide those data. Of course, I can also provide the raw data of each set of trials. Thanks, and bye, Andrea
