[RFC PATCH v2 2/2] scheduler: add scheduler level for clusters

[Song Bao Hua (Barry Song)]

> 
> Sorry. Please ignore this. I added some printk here while testing
> one numa. Will update you the data in another email.

Re-tested in one NUMA node(cpu0-cpu23):

g=1
Running in threaded mode with 1 groups using 40 file descriptors
Each sender will pass 100000 messages of 100 bytes
w/o: 7.689 7.485 7.485 7.458 7.524 7.539 7.738 7.693 7.568 7.674=7.5853
w/ : 7.516 7.941 7.374 7.963 7.881 7.910 7.420 7.556 7.695 7.441=7.6697
w/ but dropped select_idle_cluster:
     7.752 7.739 7.739 7.571 7.545 7.685 7.407 7.580 7.605 7.487=7.611

g=2
Running in threaded mode with 2 groups using 40 file descriptors
Each sender will pass 100000 messages of 100 bytes
w/o: 10.127 10.119 10.070 10.196 10.057 10.111 10.045 10.164 10.162
9.955=10.1006
w/ : 9.694 9.654 9.612 9.649 9.686 9.734 9.607 9.842 9.690 9.710=9.6878
w/ but dropped select_idle_cluster:
     9.877 10.069 9.951 9.918 9.947 9.790 9.906 9.820 9.863 9.906=9.9047

g=3
Running in threaded mode with 3 groups using 40 file descriptors
Each sender will pass 100000 messages of 100 bytes
w/o: 15.885 15.254 15.932 15.647 16.120 15.878 15.857 15.759 15.674
15.721=15.7727
w/ : 14.974 14.657 13.969 14.985 14.728 15.665 15.191 14.995 14.946
14.895=14.9005
w/ but dropped select_idle_cluster:
     15.405 15.177 15.373 15.187 15.450 15.540 15.278 15.628 15.228 15.325=15.3591

g=4
Running in threaded mode with 4 groups using 40 file descriptors
Each sender will pass 100000 messages of 100 bytes
w/o: 20.014 21.025 21.119 21.235 19.767 20.971 20.962 20.914 21.090 21.090=20.8187
w/ : 20.331 20.608 20.338 20.445 20.456 20.146 20.693 20.797 21.381 20.452=20.5647
w/ but dropped select_idle_cluster:
     19.814 20.126 20.229 20.350 20.750 20.404 19.957 19.888 20.226 20.562=20.2306

Thanks
Barry