Hi Mike, On Sat, Feb 09, 2008 at 08:58:39AM +0100, Mike Galbraith wrote: > > On Fri, 2008-02-08 at 18:04 -0600, Olof Johansson wrote: > > Hi, > > > > I ended up with a customer benchmark in my lap this week that doesn't > > do well on recent kernels. :( > > > > After cutting it down to a simple testcase/microbenchmark, it seems like > > recent kernels don't do as well with short-lived threads competing > > with the thread it's cloned off of. The CFS scheduler changes come to > > mind, but I suppose it could be caused by something else as well. > > > > The pared-down testcase is included below. Reported runtime for the > > testcase has increased almost 3x between 2.6.22 and 2.6.24: > > > > 2.6.22: 3332 ms > > 2.6.23: 4397 ms > > 2.6.24: 8953 ms > > 2.6.24-git19: 8986 ms > > My 3GHz P4 shows disjointed results. > > 2.6.22.17-smp > time 798 ms > time 780 ms > time 702 ms > > 2.6.22.17-cfs-v24.1-smp > time 562 ms > time 551 ms > time 551 ms > > 2.6.23.15-smp > time 254 ms > time 254 ms > time 293 ms > > 2.6.23.15-cfs-v24-smp > time 764 ms > time 791 ms > time 780 ms > > 2.6.24.1-smp > time 815 ms > time 820 ms > time 771 ms
How many CPUs do you have ? It's impressive to see such important variations. I would guess from the numbers that you sometimes have 1 or 2 CPUs doing nothing. I've already observed strange CPU usage patterns while building kernels (bound to 50% usage on a dual-athlon), but I can't say for sure that it was only on 2.6, so it may be related to make dependencies instead (at least it's what I've been suspecting till now). > 2.6.25-smp (git today) > time 29 ms > time 61 ms > time 72 ms These ones look rather strange. What type of workload is it ? Can you publish the program for others to test it ? Regards, Willy -- 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/