On Mon, Apr 23, 2007 at 04:55:53AM +0200, Ingo Molnar wrote: > > * Nick Piggin <[EMAIL PROTECTED]> wrote: > > > > the biggest user-visible change in -v5 are various interactivity > > > improvements (especially under higher load) to fix reported > > > regressions, and an improved way of handling nice levels. There's > > > also a new sys_sched_yield_to() syscall implementation for i686 and > > > x86_64. > > > > > > All known regressions have been fixed. (knock on wood) > > > > I think the granularity is still much too low. Why not increase it to > > something more reasonable as a default? > > note that CFS's "granularity" value is not directly comparable to > "timeslice length":
Right, but it does introduce the kbuild regression, and as we discussed, this will be only worse on newer CPUs with bigger caches or less naturally context switchy workloads. > > [ Note: while CFS's default preemption granularity is currently set to > > 5 msecs, this value does not directly transform into timeslices: for > > example two CPU-intense tasks will have effective timeslices of 10 > > msecs with this setting. ] > > also, i just checked SD: 0.46 defaults to 8 msecs rr_interval (on 1 CPU > systems), which is lower than the 10 msecs effective timeslice length > CVS-v5 achieves on two CPU-bound tasks. This is about an order of magnitude more than the current scheduler, so I still think it is too small. > (in -v6 i'll scale the granularity up a bit with the number of CPUs, > like SD does. That should get the right result on larger SMP boxes too.) I don't really like the scaling with SMP thing. The cache effects are still going to be significant on small systems, and there are lots of non-desktop users of those (eg. clusters). > while i agree it's a tad too finegrained still, I agree with Con's > choice: rather err on the side of being too finegrained and lose some > small amount of throughput on cache-intense workloads like compile jobs, > than err on the side of being visibly too choppy for users on the > desktop. So cfs gets too choppy if you make the effective timeslice comparable to mainline? My approach is completely the opposite. For testing, I prefer to make the timeslice as large as possible so any problems or regressions are really noticable and will be reported; it can be scaled back to be smaller once those kinks are ironed out. - 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/
