On 2017.02.22 at 11:44 -0700, Jens Axboe wrote: > On 02/22/2017 11:42 AM, Linus Torvalds wrote: > > On Wed, Feb 22, 2017 at 10:26 AM, Linus Torvalds > > <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > >> > >> And dammit, IF YOU DON'T EVEN KNOW, WHY THE HELL ARE YOU ASKING THE POOR USER? > > > > Basically, I'm pushing back on config options that I can't personally > > even sanely answer. > > I got that much, and I don't disagree on that part. > > > If it's a config option about "do I have a particular piece of > > hardware", it makes sense. But these new ones were just complete > > garbage. > > > > The whole "default IO scheduler" thing is a disease. We should stop > > making up these shit schedulers and then say "we don't know which one > > works best for you". > > > > All it does is encourage developers to make shortcuts and create crap > > that isn't generically useful, and then blame the user and say "well, > > you should have picked a different scheduler" when they say "this does > > not work well for me". > > > > We have had too many of those kinds of broken choices. And when the > > new Kconfig options get so confusing and so esoteric that I go "Hmm, I > > have no idea if my hardware does a single queue or not", I put my foot > > down. > > > > When the IO scheduler questions were about a generic IO scheduler for > > everything, I can kind of understand them. I think it was still a > > mistake (for the reasons outline above), but at least it was a > > comprehensible question to ask. > > > > But when it gets to "what should I do about a single-queue version of > > a MQ scheduler", the question is no longer even remotely sensible. The > > question should simply NOT EXIST. There is no possible valid reason to > > ask that kind of crap. > > OK, so here's what I'll do: > > 1) We'll kill the default scheduler choices. sq blk-mq will default to > mq-deadline, mq blk-mq will default to "none" (at least for now, until > the new scheduler is done). But what about e.g. SATA SSDs? Wouldn't they be better off without any scheduler? So perhaps setting "none" for queue/rotational==0 and mq-deadline for spinning drives automatically in the sq blk-mq case? -- Markus
