This article explains why the idle Weighted CPU (WCPU) is above 100% on an EX9200 switch. This behavior is expected in Junos version 15.1 and above.

From Junos version 15.1, Symmetric Multi-Processing (SMP) is enabled by default.

The EX9200 switch has four CPU cores and all of the core is used. Thus, idle CPU is seen as more than 100%.

This behavior is by design in Junos version 15.1 and above for on EX9200 switch.

root> show system processes extensive
last pid:  8633;  load averages:  0.27,  0.23,  0.17  up 0+00:24:55    04:43:20
117 processes: 2 running, 114 sleeping, 1 waiting
 
Mem: 448M Active, 744M Inact, 506M Wired, 1648M Buf, 14G Free
Swap: 8192M Total, 8192M Free
  PID USERNAME  THR PRI NICE   SIZE    RES STATE   C   TIME    WCPU COMMAND
   10 root        4 155 ki31     0K    64K RUN     3  96:30 398.88% idle
 8457 root        2 -26  r26   780M 23312K nanslp  3   1:19   3.27% chassisd
   12 root        3  -8    -     0K    48K -       3   0:11   0.00% geom
   11 root       25 -72    -     0K   400K WAIT   255   0:08   0.00% intr
 8500 root        1  20    0   876M 50140K select  0   0:03   0.00% authd
 8477 root        1  20    0   720M  5924K select  2   0:02   0.00% clksyncd
    0 root       22 -100    -     0K   352K -       0   0:02   0.00% kernel
   13 root        1 -16    -     0K    16K -       0   0:01   0.00% rand_harvestq
 8565 root        1  20    0   823M 25892K select  1   0:01   0.00% pfed
 8542 root        3  21    0   799M 45200K sigwai  3   0:01   0.00% pppoed
    4 root        2 -16    -     0K    32K -       0   0:01   0.00% cam
 
 
root> show system processes summary
last pid:  8634;  load averages:  0.15,  0.20,  0.16  up 0+00:25:29    04:43:54
180 processes: 5 running, 150 sleeping, 25 waiting
 
Mem: 448M Active, 744M Inact, 506M Wired, 1648M Buf, 14G Free
Swap: 8192M Total, 8192M Free
  PID USERNAME PRI NICE   SIZE    RES STATE   C   TIME    WCPU COMMAND
   10 root     155 ki31     0K    64K CPU3    3  24:41 100.00% idle{idle: cpu3}
   10 root     155 ki31     0K    64K RUN     1  24:40 100.00% idle{idle: cpu1}
   10 root     155 ki31     0K    64K CPU0    0  24:37 100.00% idle{idle: cpu0}
   10 root     155 ki31     0K    64K CPU2    2  24:44  98.10% idle{idle: cpu2}
 8457 root      23    0   780M 23312K select  0   1:20   4.39% chassisd{CHASSISD.EN_US}
 

To check the number of CPU cores, execute the following command from shell:

root@:~ # sysctl -n hw.ncpu
4
root@:~ # sysctl hw.ncpu
hw.ncpu: 4

2020-08-10: Article reviewed for accuracy and no changes needed