CentOS - Jan 2012 - CPU Usage when idle

Hello guys,

Did anyone noticed how green CentOS 6 is compared to the previous
release?  I've been running a couple of "CentOS 6" VMs (on our
vSphere
environment) for the last couple of weeks and noticed a BIG difference
when it comes to CPU usage when the VM is completely idle.   I would
like to share what I've seen in our environment:

PfSense 2.0 (FreeBSD) VM:	40 Mhz
CentOS 5.7  VM:			60 Mhz
CentOS 6.2  VM:			5 Mhz

This is really wonderful.  They did a great job with RHEL6 and I'm
curious what was changed in order to accomplish this.

Regards,
Jorge

On 1/11/2012 6:42 PM, Jorge F?bregas wrote:
>
> They did a great job with RHEL6 and I'm
> curious what was changed in order to accomplish this.
It's probably the PowerTop work, primarily done to get better battery 
life on laptops by throttling the CPU down when it's idle:

	http://www.lesswatts.org/projects/powertop/

--- On Wed, 1/11/12, Warren Young <warren at etr-usa.com> wrote:

From: Warren Young <warren at etr-usa.com>
Subject: Re: [CentOS] CPU Usage when idle
To: "CentOS mailing list" <centos at centos.org>
Date: Wednesday, January 11, 2012, 8:14 PM

On 1/11/2012 6:42 PM, Jorge F?bregas wrote:
>
> They did a great job with RHEL6 and I'm
> curious what was changed in order to accomplish this.
It's probably the PowerTop work, primarily done to get better battery 
life on laptops by throttling the CPU down when it's idle:

??? http://www.lesswatts.org/projects/powertop/

powertop is just tool, similar to top command to see the top programs causing
the cpu to wake up. I think the main improvement that Redhat themselves have
provided is the use of tickless kernel. RHEL 5 used a periodic timer for each
CPU causing it to wake up every few milliseonds to process events and thus never
really entering idle state. The tickless kernel in RHEL6 allows the system to
enter idle state more often. If you see system consuming too much power, you can
install and run powertop to find the offending programs.

See section 1.2 in RHEL 6 power management guide.

Thanks
Sheraz