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.
-yanmin
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