How to identify CPU resource problem?

vmstat command helps us to determine if a server is running short of CPU resources.

First, let us determine the number of CPUs available

Linux:

$ grep -i processor /proc/cpuinfo | wc -l

FreeBSD:

$ sysctl -a ‘hw.ncpu’
Run vmstat command 10 times with an interval of 5 seconds

$ vmstat 5 10
procs ———–memory———- —swap– —–io—- –system– —–cpu—–
r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
1  0      0 186044 123220 1006872    0    0   182   103  509 1194 13  5 78  4  0
2  0      0 185812 123236 1006728    0    0     0    26  350 1046  6  2 83  9  0
2  0      0 185812 123244 1006788    0    0     0    13  410 1111  9  2 87  2  0
1  0      0 185508 123252 1007452    0    0     0    12  358  909  6  2 91  2  0
1  0      0 185656 123260 1006784    0    0     0    27  340  784  5  1 92  2  0
0  0      0 185656 123276 1006784    0    0     0    28  323  660  4  2 93  2  0
1  0      0 185656 123284 1006784    0    0     0    11  289  610  3  1 95  2  0
1  0      0 185656 123284 1006784    0    0     0     0  296  629  3  1 96  0  0
2  0      0 185688 123292 1006784    0    0     0     5  371  905  5  2 84  9  0
1  0      0 185532 123308 1006784    0    0     0    16  403  870  8  2 88  3  0

In the above command, under the heading procs, there is a column named r, which stands for runqueue

As per the man page of vmstat, “r” stands for the number of processes waiting for run time. If the value of the runqueue, r, exceeds the number of CPUs on the server, then the tasks are forced to wait for execution.

So, in this case we need to figure out the process hogging the CPU time and either suspend it or limit it’s access to CPU by changing it’s “nice” value.