Hi, I notice a bug report on Bugzilla [1]. Quoting from it: > Noticed that under 6.5.6 (Fedora build, 6.5.6-100.fc37.x86_64) the queue/scheduler attr is not visible under namespace block device connected over nvme-fabrics. > > # readlink -f /sys/block/nvme0n1 > /sys/devices/virtual/nvme-subsystem/nvme-subsys0/nvme0n1 > # grep . /sys/devices/virtual/nvme-subsystem/nvme-subsys0/*/transport > /sys/devices/virtual/nvme-subsystem/nvme-subsys0/nvme0/transport:rdma > /sys/devices/virtual/nvme-subsystem/nvme-subsys0/nvme1/transport:rdma > # [[ -e /sys/block/nvme0n1/queue/scheduler ]] || echo oops > oops > > What's a bit confusing is that each of the ctrls attached to this subsystem also expose nvme*c*n1 device. These are marked as hidden under sysfs, hence not available as an actual block device (i.e. not present under /dev/). That said, these devices actually do have queue/scheduler attr available under sysfs. > > # readlink -f /sys/block/nvme0*c* > /sys/devices/virtual/nvme-fabrics/ctl/nvme0/nvme0c0n1 > /sys/devices/virtual/nvme-fabrics/ctl/nvme1/nvme0c1n1 > # readlink -f /sys/block/nvme0*c*/queue/scheduler > /sys/devices/virtual/nvme-fabrics/ctl/nvme0/nvme0c0n1/queue/scheduler > /sys/devices/virtual/nvme-fabrics/ctl/nvme1/nvme0c1n1/queue/scheduler > # grep . /sys/block/nvme0*c*/queue/scheduler > /sys/block/nvme0c0n1/queue/scheduler:[none] mq-deadline kyber bfq > /sys/block/nvme0c1n1/queue/scheduler:[none] mq-deadline kyber bfq > > > I have a little test infra which normally, after the nvmef got connected, would take the namespace device, set some sysfs attributes to specific values (that would include queue/scheduler) and then execute fio, targeting this namespace device. > > The only clue I got is this https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6d85ebf95c44e, but then again I am not sure what to make of it. Initially, my thought was "ok, queue/scheduler is gone, so just don't try to touch it". But if the c*n* devices still do have this attribute available, are they meant to be used instead of the actual namespace device, to tweak these specific sysfs attributes? > > The problem here is that I have two c*n* devices but only single block device (multipath setup). Would that mean that changing either of those devices' attributes would affect the actual namespace device? Or is each path independent here? > > Any hints would be appreciated. :) See Bugzilla for the full thread. Thanks. [1]: https://bugzilla.kernel.org/show_bug.cgi?id=218042 -- An old man doll... just what I always wanted! - Clara
