stan <stanl-fedorau...@vfemail.net> writes: > On Thu, 13 Dec 2018 17:24:21 +0100 > Tomasz Torcz <to...@pipebreaker.pl> 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? Cheers, Jeff _______________________________________________ devel mailing list -- devel@lists.fedoraproject.org To unsubscribe send an email to devel-le...@lists.fedoraproject.org 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@lists.fedoraproject.org
