Hacker News Reader

Comment by tanelpoder | Hacker News Reader

That would explain it. Do you recommend any docs/links I should read about allocating queues for polled IO?

It's terribly documented :(. You need to set the nvme.poll_queues to the number of queues you want, before the disks are attached. I.e. either at boot, or you need to set the parameter and then cause the NVMe to be rescanned (you can do that in sysfs, but I can't immediately recall the steps with high confidence).

Ah, yes, shell history ftw. Of course you should ensure no filesystem is mounted or such:

    root@awork3:~# echo 4 > /sys/module/nvme/parameters/poll_queues
    root@awork3:~# echo 1 > /sys/block/nvme1n1/device/reset_controller
    root@awork3:~# dmesg -c
    [749717.253101] nvme nvme1: 12/0/4 default/read/poll queues
    root@awork3:~# echo 8 > /sys/module/nvme/parameters/poll_queues
    root@awork3:~# dmesg -c
    root@awork3:~# echo 1 > /sys/block/nvme1n1/device/reset_controller
    root@awork3:~# dmesg -c
    [749736.513102] nvme nvme1: 8/0/8 default/read/poll queues

Thanks for the pointers, I'll bookmark this and will try it out someday.

Reply on news.ycombinator.com