On Mon, Apr 16, 2007 at 11:26:21PM -0700, William Lee Irwin III wrote: > On Mon, Apr 16, 2007 at 11:09:55PM -0700, William Lee Irwin III wrote: > >> All things are not equal; they all have different properties. I like > > On Tue, Apr 17, 2007 at 08:15:03AM +0200, Nick Piggin wrote: > > Exactly. So we have to explore those properties and evaluate performance > > (in all meanings of the word). That's only logical. > > Any chance you'd be willing to put down a few thoughts on what sorts > of standards you'd like to set for both correctness (i.e. the bare > minimum a scheduler implementation must do to be considered valid > beyond not oopsing) and performance metrics (i.e. things that produce > numbers for each scheduler you can compare to say "this scheduler is > better than this other scheduler at this.").
Yeah I guess that's the hard part :) For correctness, I guess fairness is an easy one. I think that unfairness is basically a bug and that it would be very unfortunate to merge something unfair. But this is just within the context of a single runqueue... for better or worse, we allow some unfairness in multiprocessors for performance reasons of course. Latency. Given N tasks in the system, an arbitrary task should get onto the CPU in a bounded amount of time (excluding events like freak IRQ holdoffs and such, obviously -- ie. just considering the context of the scheduler's state machine). I wouldn't like to see a significant drop in any micro or macro benchmarks or even worse real workloads, but I could accept some if it means haaving a fair scheduler by default. Now it isn't actually too hard to achieve the above, I think. The hard bit is trying to compare interactivity. Ideally, we'd be able to get scripted dumps of login sessions, and measure scheduling latencies of key proceses (sh/X/wm/xmms/firefox/etc). People would send a dump if they were having problems with any scheduler, and we could compare all of them against it. Wishful thinking! - 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/
