[CentOS] CPU usage over estimated?
Theo Band
theo.band at greenpeak.com
Fri Jun 5 07:38:35 UTC 2009
Filipe Brandenburger wrote:
> Hi,
>
> On Thu, Jun 4, 2009 at 08:37, Theo Band <theo.band at greenpeak.com> wrote:
>
>> When I use top, I see that running processes use 245% instead of 100%.
>> If I use gkrellm, I just see one core being used 100%.
>> There are all single threaded programs, so it's not that more cores are
>> being used.
>>
>
> Are you sure?
>
> You can type "H" in top to show separate threads, that way it would
> show up if you have more than one thread running in one of those
> programs
Yes I'm quite sure. For instance cpuburn on two machines, the only
difference is hardware (two versus four cores). The H option does not
show more threads:
Machine a (dual core Centos5 64 bit)
Intel(R) Core(TM)2 Duo CPU E8400
2.6.18-128.1.6.el5 #1 SMP Wed Apr 1 09:10:25 EDT 2009 x86_64 x86_64
x86_64 GNU/Linux
top - 09:26:00 up 62 days, 21:43, 1 user, load average: 0.30, 0.16, 0.17
Tasks: 120 total, 3 running, 117 sleeping, 0 stopped, 0 zombie
Cpu(s): 50.0%us, 0.2%sy, 0.0%ni, 49.8%id, 0.0%wa, 0.0%hi, 0.0%si,
0.0%st
Mem: 4050728k total, 2448800k used, 1601928k free, 405860k buffers
Swap: 3538936k total, 22172k used, 3516764k free, 1762448k cached
PID USER PR NI VIRT RES SWAP SHR S %CPU %MEM TIME+ COMMAND
16916 thba 25 0 2068 988 1080 308 R 100.2 0.0 0:11.48
cpuburn-in
Machine b (quad core Centos5 64 bit)
Intel(R) Core(TM) i7 CPU 940 @ 2.93GHz
2.6.18-128.1.6.el5 #1 SMP Wed Apr 1 09:10:25 EDT 2009 x86_64 x86_64
x86_64 GNU/Linux
top - 09:28:24 up 25 days, 40 min, 2 users, load average: 1.44, 1.83, 1.83
Tasks: 165 total, 3 running, 162 sleeping, 0 stopped, 0 zombie
Cpu(s): 25.1%us, 0.5%sy, 25.0%ni, 49.4%id, 0.0%wa, 0.0%hi, 0.0%si,
0.0%st
Mem: 6097924k total, 4366540k used, 1731384k free, 152248k buffers
Swap: 4194296k total, 112k used, 4194184k free, 3322344k cached
PID USER PR NI VIRT RES SWAP SHR S %CPU %MEM TIME+ COMMAND
13873 thba 25 0 2068 988 1080 308 R 243.8 0.0 0:26.97
cpuburn-in
The total cpu reported is about correct (for the second machine two jobs
ran, one cpuburn-in=25% and one other with nice15=25%). It's just the
individual process on this quad core machine that's way off.
When I build the machine a couple of months ago, I did benchmarks and
used top as well. It did show "normal" results, most of the time 100%
for a process and sometimes a little more. So I guess an update in the
mean time has changed something.
Theo
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