On Tue, Apr 17, 2007 at 11:38:31PM -0500, Matt Mackall wrote: > On Wed, Apr 18, 2007 at 05:15:11AM +0200, Nick Piggin wrote: > > > > I don't know why this would be a useful feature (of course I'm talking > > about processes at the same nice level). One of the big problems with > > the current scheduler is that it is unfair in some corner cases. It > > works OK for most people, but when it breaks down it really hurts. At > > least if you start with a fair scheduler, you can alter priorities > > until it satisfies your need... with an unfair one your guess is as > > good as mine. > > > > So on what basis would you allow unfairness? On the basis that it doesn't > > seem to harm anyone? It doesn't seem to harm testers? > > On the basis that there's only anecdotal evidence thus far that > fairness is the right approach. > > It's not yet clear that a fair scheduler can do the right thing with X, > with various kernel threads, etc. without fiddling with nice levels. > Which makes it no longer "completely fair".
Of course I mean SCHED_OTHER tasks at the same nice level. Otherwise I would be arguing to make nice basically a noop. > It's also not yet clear that a scheduler can't be taught to do the > right thing with X without fiddling with nice levels. Being fair doesn't prevent that. Implicit unfairness is wrong though, because it will bite people. What's wrong with allowing X to get more than it's fair share of CPU time by "fiddling with nice levels"? That's what they're there for. > So I'm just not yet willing to completely rule out systems that aren't > "completely fair". > > But I think we should rule out schedulers that don't have rigid bounds on > that unfairness. That's where the really ugly behavior lies. Been a while since I really looked at the mainline scheduler, but I don't think it can permanently starve something, so I don't know what your bounded unfairness would help with. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
