Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

This is the CPU usage graph of a server:

enter image description here

It seems that the CPU usage reached a hard limit at 24. This is a 32-core server so it should be able to go beyond 24 with ease. But that's not the case.

Is it possible that there's a cap on CPU usage on this server. How do I find out?

By the way, this is a database server running Percona (MySQL) Server 5.1 on CentOS 5.5

share|improve this question
Does top actually show eight CPU's "at rest" or just 75% load? – Mark Mar 5 '11 at 20:13

You might be I/O or memory limited, rather than cpu limited. Your cpu won't burn cycles just to burn cycles if it's stuck waiting on disk, network, or memory. It could also be a software limitation, if you're using something that's not written to be aware of more than 24 cores.

share|improve this answer

You have to see the CPU utilization for each CPU. I am using dstat -ta 10 to see that. Because the graph is a straight line it rules out that the load could be I/O bound. Now you have to see why MySQL is not using all CPUs. See also:

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.