About the cpu usage

sub320 · 06-27-2018, 02:07 AM

I found my server have a process that the cpu usage is over 100% , just would like to know why the % could be over 100 ? is it because there are over 1 CPU ?

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND

2223 root 20 0 15096 1172 468 S 122.4 0.0 6996:55 sysocpd

Keruskerfuerst · 06-27-2018, 02:14 AM

If your CPU has more than core, then the CPU can rise over 100%.

What CPU do you have?

syg00 · 06-27-2018, 02:30 AM

top display is non-normalised (each process is a percentage of one CPU), so a multi-threaded task can sum to over 100%.

Honest Abe · 06-27-2018, 02:31 AM

@OP, are you viewing CPU usage from top ?

Toggle the irix mode (inside top, press I (shift+i)) and see how the output changes. Again, press 1 and see how your individual cores are working.
The irix mode is explained nicely in the man page of top.

Example - (Irix Off)

Code:

top - 12:58:48 up 21 min,  2 users,  load average: 5.37, 4.03, 2.18
Tasks: 229 total,   2 running, 227 sleeping,   0 stopped,   0 zombie
%Cpu0  : 50.8 us,  8.5 sy,  0.0 ni, 29.8 id, 10.8 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu1  : 54.1 us,  5.7 sy,  0.0 ni, 24.3 id, 15.9 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu2  : 60.6 us,  4.7 sy,  0.0 ni, 10.1 id, 23.9 wa,  0.0 hi,  0.7 si,  0.0 st
%Cpu3  : 57.2 us,  5.0 sy,  0.0 ni, 32.4 id,  5.4 wa,  0.0 hi,  0.0 si,  0.0 st
KiB Mem : 16390404 total,  7944188 free,  3999300 used,  4446916 buff/cache
KiB Swap:  3170300 total,  3170300 free,        0 used. 11924736 avail Mem 

  PID USER      PR  NI    VIRT    RES    SHR S %CPU %MEM     TIME+ COMMAND      
 3174 qemu      20   0 2267032   1.1g  11496 S 20.5  7.1   8:10.03 qemu-kvm     
 3027 qemu      20   0 2265840   1.1g  11492 S 19.6  7.2   7:53.00 qemu-kvm     
 1474 root      20   0  347636  84836  64408 R  7.9  0.5   2:40.71 X            
 2771 root      20   0 2507372 373064  36344 S  6.9  2.3   3:15.79 virt-manager 
 2267 root      20   0 3652252 282352  71864 S  5.7  1.7   3:26.57 gnome-shell  
 1509 root     -51   0       0      0      0 S  0.9  0.0   0:21.35 irq/127-nvi+ 
 3306 root      20   0 2033192 199468  81080 S  0.3  1.2   0:45.17 Web Content

Example - (Irix On)

Code:

top - 12:59:23 up 21 min,  2 users,  load average: 5.16, 4.13, 2.28
Tasks: 228 total,   5 running, 223 sleeping,   0 stopped,   0 zombie
%Cpu0  : 53.8 us,  9.9 sy,  0.0 ni, 22.5 id, 13.7 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu1  : 53.0 us,  5.5 sy,  0.0 ni, 29.3 id, 12.2 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu2  : 48.6 us,  7.7 sy,  0.0 ni, 23.5 id, 19.7 wa,  0.0 hi,  0.5 si,  0.0 st
%Cpu3  : 47.0 us,  6.6 sy,  0.0 ni, 24.6 id, 21.9 wa,  0.0 hi,  0.0 si,  0.0 st
KiB Mem : 16390404 total,  7819608 free,  3998068 used,  4572728 buff/cache
KiB Swap:  3170300 total,  3170300 free,        0 used. 11920512 avail Mem 

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND     
 3174 qemu      20   0 2267032   1.1g  11496 S  81.8  7.1   8:38.51 qemu-kvm    
 3027 qemu      20   0 2265840   1.1g  11492 S  64.6  7.2   8:20.09 qemu-kvm    
 1474 root      20   0  347636  84836  64408 R  29.8  0.5   2:51.61 X           
 2771 root      20   0 2507372 373064  36344 R  26.0  2.3   3:25.75 virt-manag+ 
 2267 root      20   0 3652252 282660  71864 S  21.0  1.7   3:35.28 gnome-shell 
 1509 root     -51   0       0      0      0 S   3.9  0.0   0:22.70 irq/127-nv+ 
 2791 root      20   0  666936  26212  16664 D   0.6  0.2   0:01.16 gnome-term+ 
 3197 root      20   0 2610212 279036 100128 S   0.6  1.7   0:44.04 firefox

sub320 · 06-27-2018, 02:32 AM

Quote:

Originally Posted by Keruskerfuerst

If your CPU has more than core, then the CPU can rise over 100%.

What CPU do you have?

check by dmidecode -t 4 | grep CPU , I have 2 physical CPU .

sub320 · 06-27-2018, 02:48 AM

Quote:

Originally Posted by Honest Abe

@OP, are you viewing CPU usage from top ?

Toggle the irix mode (inside top, press I (shift+i)) and see how the output changes. Again, press 1 and see how your individual cores are working.
The irix mode is explained nicely in the man page of top.

Example - (Irix Off)

Code:

top - 12:58:48 up 21 min,  2 users,  load average: 5.37, 4.03, 2.18
Tasks: 229 total,   2 running, 227 sleeping,   0 stopped,   0 zombie
%Cpu0  : 50.8 us,  8.5 sy,  0.0 ni, 29.8 id, 10.8 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu1  : 54.1 us,  5.7 sy,  0.0 ni, 24.3 id, 15.9 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu2  : 60.6 us,  4.7 sy,  0.0 ni, 10.1 id, 23.9 wa,  0.0 hi,  0.7 si,  0.0 st
%Cpu3  : 57.2 us,  5.0 sy,  0.0 ni, 32.4 id,  5.4 wa,  0.0 hi,  0.0 si,  0.0 st
KiB Mem : 16390404 total,  7944188 free,  3999300 used,  4446916 buff/cache
KiB Swap:  3170300 total,  3170300 free,        0 used. 11924736 avail Mem 

  PID USER      PR  NI    VIRT    RES    SHR S %CPU %MEM     TIME+ COMMAND      
 3174 qemu      20   0 2267032   1.1g  11496 S 20.5  7.1   8:10.03 qemu-kvm     
 3027 qemu      20   0 2265840   1.1g  11492 S 19.6  7.2   7:53.00 qemu-kvm     
 1474 root      20   0  347636  84836  64408 R  7.9  0.5   2:40.71 X            
 2771 root      20   0 2507372 373064  36344 S  6.9  2.3   3:15.79 virt-manager 
 2267 root      20   0 3652252 282352  71864 S  5.7  1.7   3:26.57 gnome-shell  
 1509 root     -51   0       0      0      0 S  0.9  0.0   0:21.35 irq/127-nvi+ 
 3306 root      20   0 2033192 199468  81080 S  0.3  1.2   0:45.17 Web Content

Example - (Irix On)

Code:

top - 12:59:23 up 21 min,  2 users,  load average: 5.16, 4.13, 2.28
Tasks: 228 total,   5 running, 223 sleeping,   0 stopped,   0 zombie
%Cpu0  : 53.8 us,  9.9 sy,  0.0 ni, 22.5 id, 13.7 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu1  : 53.0 us,  5.5 sy,  0.0 ni, 29.3 id, 12.2 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu2  : 48.6 us,  7.7 sy,  0.0 ni, 23.5 id, 19.7 wa,  0.0 hi,  0.5 si,  0.0 st
%Cpu3  : 47.0 us,  6.6 sy,  0.0 ni, 24.6 id, 21.9 wa,  0.0 hi,  0.0 si,  0.0 st
KiB Mem : 16390404 total,  7819608 free,  3998068 used,  4572728 buff/cache
KiB Swap:  3170300 total,  3170300 free,        0 used. 11920512 avail Mem 

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND     
 3174 qemu      20   0 2267032   1.1g  11496 S  81.8  7.1   8:38.51 qemu-kvm    
 3027 qemu      20   0 2265840   1.1g  11492 S  64.6  7.2   8:20.09 qemu-kvm    
 1474 root      20   0  347636  84836  64408 R  29.8  0.5   2:51.61 X           
 2771 root      20   0 2507372 373064  36344 R  26.0  2.3   3:25.75 virt-manag+ 
 2267 root      20   0 3652252 282660  71864 S  21.0  1.7   3:35.28 gnome-shell 
 1509 root     -51   0       0      0      0 S   3.9  0.0   0:22.70 irq/127-nv+ 
 2791 root      20   0  666936  26212  16664 D   0.6  0.2   0:01.16 gnome-term+ 
 3197 root      20   0 2610212 279036 100128 S   0.6  1.7   0:44.04 firefox

I used your way to check , the output is below , CPU% is 432.5 , is it mean the process is run by different cores , they sum up into one total cpu usage , so it is much over 100% ?

2223 root 20 0 15096 1172 468 S 432.5 0.0 6996:55 sysocpd

Honest Abe · 06-27-2018, 03:06 AM

yes, the process is using multiple CPU cores.

There's a simple way to validate this. See my example of PID 4424-

Code:

[root@AB-Cent7OS ~]# ps -o pid,psr,comm -p 4424
  PID PSR COMMAND
 4424   2 qemu-kvm
[root@AB-Cent7OS ~]# ps -o pid,psr,comm -p 4424
  PID PSR COMMAND
 4424   3 qemu-kvm
[root@AB-Cent7OS ~]# ps -o pid,psr,comm -p 4424
  PID PSR COMMAND
 4424   0 qemu-kvm

See how the PSR changes ?

You can wrap the command in a endless loop (or use watch) and see for yourself. Substitute 4424 with your PID.