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I'd like to clarify that I'm not trying to push this particular code to the kernel. I'm a researcher. My intent was to point out that we have a problem in the scheduler and my dwrr algorithm can potentially help fix it. The patch itself was merely a proof-of-concept. I'd be thrilled if the algorithm can be proven useful in the real world. I appreciate the people who have given me comments. Since then, I've revised my algorithm/code. Now it doesn't require global locking but retains strong fairness properties (which I was able to prove mathematically). Thank you, tong On Thu, 26 Jul 2007, Li, Tong N wrote: > On Thu, 2007-07-26 at 23:31 +0200, Ingo Molnar wrote: >> * Tong Li <tong.n.li@intel.com> wrote: >> >>>> you need to measure it over longer periods of time. Its not worth >>>> balancing for such a thing in any high-frequency manner. (we'd trash >>>> the cache constantly migrating tasks back and forth.) >>> >>> I have some data below, but before that, I'd like to say, at the same >>> load balancing rate, my proposed approach would allow us to have >>> fairness on the order of seconds. I'm less concerned about trashing >>> the cache. The important thing is to have a knob that allow users to >>> trade off fairness and performance based on their needs. [...] >> >> such a knob already exists to a certain degree, but i havent tested its >> full effects on SMP fairness yet. If you pull my scheduler tree: >> >> git://git.kernel.org/pub/scm/linux/kernel/git/mingo/linux-2.6-sched.git >> >> and if you enable CONFIG_SCHED_DEBUG, then all the sched-domain >> parameters become runtime tunable under /proc/sys/cpu*. >> >> Could you try to increase the cross-CPU rebalancing frequency and see >> how it impacts the precision of your measurement? Tune 'min_interval' >> and 'max_interval' down to increase the frequency of rebalancing. >> >> Ingo > > Yes, I'll do it when I find time. If anyone is willing to do the > testing, please let me know and I can post my benchmark. On the other > hand, I don't think tuning the existing knobs will help solve the > problem. The root of the problem is that the current load balancing > doesn't take into account how much time each task has been running and > how much it's entitled. This is why I'm proposing a new approach for > solving it. The new approach, as I said, will be much more fair/accurate > than the current one even without tuning those balancing intervals > (i.e., it's able to provide good fairness even if balancing is less > frequent). > > tong > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||||
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