On Fri, Dec 14, 2018 at 11:34 AM Jeff Moyer <jmoyer@xxxxxxxxxx> wrote: > > stan <stanl-fedorauser@xxxxxxxxxxx> writes: > > > On Thu, 13 Dec 2018 17:24:21 +0100 > > Tomasz Torcz <tomek@xxxxxxxxxxxxxx> wrote: > > > >> On Wed, Dec 12, 2018 at 04:30:20PM -0700, stan wrote: > > > >> > Enabled deadline and cfq again, but still no bfq available. > >> > $ cat /sys/block/sda/queue/scheduler > >> > noop deadline [cfq] > >> > >> Those are single-queue scheduler. Multiqueue uses different > >> schedulers: bfq, kyber, mq-deadline. MQ schedulers won't appear on > >> single-queue devices even if you modprobe such schedulers. > >> You probably need “scsi_mod.use_blk_mq=y dm_mod.use_blk_mq=y” kernel > >> commandline options, although I think those are default in recent > >> kernels. > > > > Thanks. I got the impression from the documentation I read that BFQ > > operated for both mq and single queue. In fact, IIRC it actually > > degraded mq performance slightly, but enhanced single queue > > performance. I guess I was wrong. I'll try the above to see if it > > enables me to use bfq on single queue devices. > > Yes, it is confusing. Basically, the block layer (and scsi) support a > legacy path and multi-queue (blk-mq, scsi-mq). However, even if you are > using blk-mq and scsi-mq, there are two types of devices: those that > support a single hardware queue, and those that support multiple > hardware queues. > > So, mq schedulers (such as kyber, mq-deadline and bfq) require blk-mq, > but they can be used on hardware that supports only a single queue. > This is the distinction that was being made in the bfq documentation. > > Clear as mud? In everything I've read, scsi_mod.use_blk_mq=1 boot param is required if kernel config # CONFIG_SCSI_MQ_DEFAULT is not set, and on Fedora kernels it is not set. So far, when I insmod bfq, that will make it show up as an option for nvme drives, but not hard drives. I haven't figured out to make it show up for hard drives. -- Chris Murphy _______________________________________________ devel mailing list -- devel@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to devel-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://getfedora.org/code-of-conduct.html List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/devel@xxxxxxxxxxxxxxxxxxxxxxx
