On Thu, 2007-11-01 at 11:02 +0100, Cyrus Massoumi wrote: > Zhang, Yanmin wrote: > > On Wed, 2007-10-31 at 17:57 +0800, Zhang, Yanmin wrote: > >> On Tue, 2007-10-30 at 16:36 +0800, Zhang, Yanmin wrote: > >>> On Tue, 2007-10-30 at 08:26 +0100, Ingo Molnar wrote: > >>>> * Zhang, Yanmin <[EMAIL PROTECTED]> wrote: > >>>> > >>>>> sub-bisecting captured patch > >>>>> 38ad464d410dadceda1563f36bdb0be7fe4c8938(sched: uniform tunings) > >>>>> caused 20% regression of aim7. > >>>>> > >>>>> The last 10% should be also related to sched parameters, such like > >>>>> sysctl_sched_min_granularity. > >>>> ah, interesting. Since you have CONFIG_SCHED_DEBUG enabled, could you > >>>> please try to figure out what the best value for > >>>> /proc/sys/kernel_sched_latency, /proc/sys/kernel_sched_nr_latency and > >>>> /proc/sys/kernel_sched_min_granularity is? > >>>> > >>>> there's a tuning constraint for kernel_sched_nr_latency: > >>>> > >>>> - kernel_sched_nr_latency should always be set to > >>>> kernel_sched_latency/kernel_sched_min_granularity. (it's not a free > >>>> tunable) > >>>> > >>>> i suspect a good approach would be to double the value of > >>>> kernel_sched_latency and kernel_sched_nr_latency in each tuning > >>>> iteration, while keeping kernel_sched_min_granularity unchanged. That > >>>> will excercise the tuning values of the 2.6.23 kernel as well. > >>> I followed your idea to test 2.6.24-rc1. The improvement is slow. > >>> When sched_nr_latency=2560 and sched_latency_ns=640000000, the performance > >>> is still about 15% less than 2.6.23. > >> I got the aim7 30% regression on my new upgraded stoakley machine. I found > >> this mahcine is slower than the old one. Maybe BIOS has issues, or > >> memeory(Might not > >> be dual-channel?) is slow. So I retested it on the old machine and found > >> on the old > >> stoakley machine, the regression is about 6%, quite similiar to the > >> regression on tigerton > >> machine. > >> > >> By sched_nr_latency=640 and sched_latency_ns=640000000 on the old stoakley > >> machine, > >> the regression becomes about 2%. Other latency has more regression. > >> > >> On my tulsa machine, by sched_nr_latency=640 and > >> sched_latency_ns=640000000, > >> the regression becomes less than 1% (The original regression is about 20%). > > I rerun SPECjbb by ched_nr_latency=640 and sched_latency_ns=640000000. On > > tigerton, > > the regression is still more than 40%. On stoakley machine, it becomes > > worse (26%, > > original is 9%). I will do more investigation to make sure SPECjbb > > regression is > > also casued by the bad default values. > > > > We need a smarter method to calculate the best default values for the key > > tuning > > parameters. > > > > One interesting is sysbench+mysql(readonly) got the same result like 2.6.22 > > (no > > regression). Good job! > > Do you mean you couldn't reproduce the regression which was reported > with 2.6.23 (http://lkml.org/lkml/2007/10/30/53) with 2.6.24-rc1? It looks like you missed my emails.
Firstly, I reproduced (or just find the same myself :) ) the issue with kernel 2.6.22, 2.6.23-rc and 2.6.23. Ingo wrote a big patch to fix it and the new patch is in 2.6.24-rc1 now. Then I retested it with 2.6.24-rc1 on a couple of x86_64 machines. The issue disappeared. You could test it with 2.6.24-rc1. > It > would be nice if you could provide some numbers for 2.6.22, 2.6.23 and > 2.6.24-rc1. Sorry. Intel policy doesn't allow me to publish the numbers because only specific departments in Intel could do that. But I could talk the regression percentage. -yanmin - 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/
