On Tue, Apr 17, 2007 at 03:32:56PM -0700, William Lee Irwin III wrote: > On Tue, Apr 17, 2007 at 11:24:22AM +0200, Ingo Molnar wrote: > >> yeah. If you could come up with a sane definition that also translates > >> into low overhead on the algorithm side that would be great! > > On Tue, Apr 17, 2007 at 05:08:09PM -0500, Matt Mackall wrote: > > How's this: > > If you're running two identical CPU hog tasks A and B differing only by nice > > level (Anice, Bnice), the ratio cputime(A)/cputime(B) should be a > > constant f(Anice - Bnice). > > Other definitions make things hard to analyze and probably not > > well-bounded when confronted with > 2 tasks. > > I -think- this implies keeping a separate scaled CPU usage counter, > > where the scaling factor is a trivial exponential function of nice > > level where f(0) == 1. Then you schedule based on this scaled usage > > counter rather than unscaled. > > I also suspect we want to keep the exponential base small so that the > > maximal difference is 10x-100x. > > I'm already working with this as my assumed nice semantics (actually > something with a specific exponential base, suggested in other emails) > until others start saying they want something different and agree.
Good. This has a couple nice mathematical properties, including "bounded unfairness" which I mentioned earlier. What base are you looking at? -- Mathematics is the supreme nostalgia of our time. - 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/
