[v3.9][regression] a simple ' time vmstat 1 11 ' can takes up 25s+!

[feng xiangjun]

Hi guys,
I wonder if anyone see this problem.

When running 3.9-rc3+,  the system is very sluggish.
For example, on an almost idle system,

~$ time vmstat 1 11
procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
 0  0      0 6046296  28716 1576096    0    0  1245   391  260 1034 11  3 72 15
 4  0      0 6046172  28716 1576172    0    0     0     0  318  761  0  0 99  0
 6  0      0 6049892  28716 1571844    0    0     0    28  439 1036  0  0 99  0
 5  0      0 6049944  28716 1571844    0    0     0     0  265  717  0  0 99  0
 2  0      0 6050016  28716 1571844    0    0     0     0   90  327  2  0 98  0
 1  0      0 6049892  28716 1571848    0    0     0     0   60  126  1  0 99  0
 0  0      0 6049892  28716 1571848    0    0     0     0   62  157  1  0 99  0
 1  0      0 6049892  28716 1571848    0    0     0     0   66  127  1  0 99  0
 0  0      0 6049892  28716 1571848    0    0     0     0   75  158  2  0 98  0
 1  0      0 6049892  28716 1571848    0    0     0     0   59  124  1  0 100  0
 0  0      0 6049892  28716 1571848    0    0     0     0   62  155  2  0 99  0

real    0m25.061s
user    0m0.000s
sys     0m0.000s

It should be 10s.

Dmesg and kernel config attached.
It's a non preempt kernel(CONFIG_PREEMPT_NONE=y),
maybe these days no one running non preempt on their system?

I've not tried 3.9-rc1/rc2, will try to bisect this ...
3.8.x works fine.

Attachment: 3.9.config.gz
Description: GNU Zip compressed data

Attachment: dmesg.gz
Description: GNU Zip compressed data