[CentOS] CPU usage from top

William Warren hescominsoon at emmanuelcomputerconsulting.com
Fri Dec 9 16:52:43 UTC 2005


94.2% id

that's 94 percent idle.  Looks good here and your load averages are low 
as well.  Where's the problem?


Bowie Bailey wrote:
> I'm seeing some strange results from top on CentOS 4.0.  When it first
> starts, it reports low CPU usage.  The next refresh (and subsequent)
> refreshes, it shows high CPU usage.  In both cases, there is nothing
> shown in the process list that is using much CPU.  What is causing
> this?
> 
> Here is some truncated output from a single run of "top -b -n 2":
> 
> ----------------------------------------------------------------------------
> --
> top - 10:22:02 up 34 days, 14:36,  2 users,  load average: 0.98, 0.56, 0.51
> Tasks: 116 total,   1 running, 115 sleeping,   0 stopped,   0 zombie
> Cpu(s):  3.7% us,  0.7% sy,  0.0% ni, 94.2% id,  1.3% wa,  0.0% hi,  0.0% si
> Mem:   1034676k total,   610804k used,   423872k free,    35796k buffers
> Swap:  1052248k total,    14220k used,  1038028k free,   314524k cached
> 
>   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
> 16412 root      16   0  2280  864  664 R  5.6  0.1   0:00.06 top
>     1 root      16   0  3148  516  464 S  0.0  0.0   0:01.91 init
>     2 root      RT   0     0    0    0 S  0.0  0.0   0:04.32 migration/0
>     3 root      34  19     0    0    0 S  0.0  0.0   0:00.34 ksoftirqd/0
>     4 root      RT   0     0    0    0 S  0.0  0.0   0:02.32 migration/1
>     5 root      34  19     0    0    0 S  0.0  0.0   0:00.39 ksoftirqd/1
>     6 root       5 -10     0    0    0 S  0.0  0.0   0:00.13 events/0
>     7 root       5 -10     0    0    0 S  0.0  0.0   0:00.00 events/1
>     8 root       5 -10     0    0    0 S  0.0  0.0   0:00.18 khelper
>     9 root       5 -10     0    0    0 S  0.0  0.0   0:00.00 kblockd/0
> 
> 
> top - 10:22:05 up 34 days, 14:36,  2 users,  load average: 0.98, 0.56, 0.51
> Tasks: 116 total,   1 running, 115 sleeping,   0 stopped,   0 zombie
> Cpu(s): 49.1% us,  1.6% sy,  0.0% ni, 48.8% id,  0.2% wa,  0.2% hi,  0.2% si
> Mem:   1034676k total,   610804k used,   423872k free,    35800k buffers
> Swap:  1052248k total,    14220k used,  1038028k free,   314520k cached
> 
>   PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
> 16412 root      17   0  2288  960  748 R  1.6  0.1   0:00.11 top
> 16052 bowieb    16   0  8288 2232 1812 S  0.3  0.2   0:03.04 sshd
>     1 root      16   0  3148  516  464 S  0.0  0.0   0:01.91 init
>     2 root      RT   0     0    0    0 S  0.0  0.0   0:04.32 migration/0
>     3 root      34  19     0    0    0 S  0.0  0.0   0:00.34 ksoftirqd/0
>     4 root      RT   0     0    0    0 S  0.0  0.0   0:02.32 migration/1
>     5 root      34  19     0    0    0 S  0.0  0.0   0:00.39 ksoftirqd/1
>     6 root       5 -10     0    0    0 S  0.0  0.0   0:00.13 events/0
>     7 root       5 -10     0    0    0 S  0.0  0.0   0:00.00 events/1
>     8 root       5 -10     0    0    0 S  0.0  0.0   0:00.18 khelper
>     9 root       5 -10     0    0    0 S  0.0  0.0   0:00.00 kblockd/0
> ----------------------------------------------------------------------------
> --
> 
> Notice 3.7% usage on the first one and 49.1% usage on the second.
> 
> I suspect that top isn't showing me everything.  I know that some
> versions of top had problems with showing proper CPU usage for
> threaded applications.  Is that still a problem with the current
> version of top?
> 
> Bowie
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> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos
> 

-- 
My "Foundation" verse:
Isa 54:17  No weapon that is formed against thee shall prosper; and 
every tongue that shall rise against thee in judgment thou shalt 
condemn. This is the heritage of the servants of the LORD, and their 
righteousness is of me, saith the LORD.

-- carpe ductum -- "Grab the tape"
CDTT (Certified Duct Tape Technician)

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