Messages in this thread | | | Date | Thu, 01 Nov 2007 11:02:59 +0100 | From | Cyrus Massoumi <> | Subject | Re: aim7 -30% regression in 2.6.24-rc1 |
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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 <yanmin_zhang@linux.intel.com> 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 would be nice if you could provide some numbers for 2.6.22, 2.6.23 and 2.6.24-rc1.
> -yanmin
greetings Cyrus
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