CPUSpeed scaling causing performance issues in some cases.

If your servers CPU seems to be running slow, it may be clocked down via the default installed CPUSPEED Daemon. This will re-clock your CPU (on supported models) to save power when it's not in use. The bad side effect is that some times it's not very good at determining any of that and will typically cause performance issues.

Here, you can see how this CPU is clocked down on my home server:

[dave@eos dave]$ cat /proc/cpuinfo | grep "model name\|cpu MHz\|proce"
processor	: 0
model name	: AMD Athlon(tm) II X3 435 Processor
cpu MHz		: 2900.000
processor	: 1
model name	: AMD Athlon(tm) II X3 435 Processor
cpu MHz		: 800.000
processor	: 2
model name	: AMD Athlon(tm) II X3 435 Processor
cpu MHz		: 800.000

Lets disable CPU Speed and turn off the daemon and then we'll check CPU Speeds again:

[dave@eos dave]$ sudo chkconfig cpuspeed off
[dave@eos dave]$ chkconfig --list | grep cpuspeed
cpuspeed       	0:off	1:on	2:off	3:off	4:off	5:off	6:off
[dave@eos dave]$ sudo service cpuspeed stop
Disabling ondemand cpu frequency scaling:                  [  OK  ]
[dave@eos dave]$ cat /proc/cpuinfo | grep "model name\|cpu MHz\|proce"
processor	: 0
model name	: AMD Athlon(tm) II X3 435 Processor
cpu MHz		: 2900.000
processor	: 1
model name	: AMD Athlon(tm) II X3 435 Processor
cpu MHz		: 2900.000
processor	: 2
model name	: AMD Athlon(tm) II X3 435 Processor
cpu MHz		: 2900.000

There you have it -- back to full speed.

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