On Wed, 2007-10-31 at 17:57 +0800, Zhang, Yanmin wrote:On Tue, 2007-10-30 at 16:36 +0800, Zhang, Yanmin wrote:I rerun SPECjbb by ched_nr_latency=640 and sched_latency_ns=640000000. On tigerton,On Tue, 2007-10-30 at 08:26 +0100, Ingo Molnar wrote:I got the aim7 30% regression on my new upgraded stoakley machine. I found* Zhang, Yanmin <yanmin_zhang@xxxxxxxxxxxxxxx> wrote:I followed your idea to test 2.6.24-rc1. The improvement is slow.
sub-bisecting captured patch 38ad464d410dadceda1563f36bdb0be7fe4c8938(sched: uniform tunings) caused 20% regression of aim7.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?
The last 10% should be also related to sched parameters, such like sysctl_sched_min_granularity.
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.
When sched_nr_latency=2560 and sched_latency_ns=640000000, the performance
is still about 15% less than 2.6.23.
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
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%).
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
One interesting is sysbench+mysql(readonly) got the same result like 2.6.22 (no
regression). Good job!