Friday, July 31, 2009

VMware guest optimization: Linux

In an effort to squeeze every bit of performance and achieve maximum efficiency out of our vSphere farm, I came across adjusting "ticks" in recent kernel releases. As far as I understand it, ticks are the method in which the CPU(s) query the kernel activity. The more the ticking, the more the checking. Ticks can be favorable for desktop installations such as a user moving the mouse while compiling a program. Compiling is processor intensive but because of the ticks, the CPU looks for the mouse movement in order to fluidly paint the movement across the screen.

Most server installations don't use a mouse often. Therefore, the treadoff may be less variable but the kernel is able to process jobs longer. A side effect, among many, is less power consumption because the kernel isn't constantly nagging the processor(s). It is recommended that Linux VMs employ some sort of tick managment to reduce the activity. Here is a link from VMware showing the various distros that support tick management and how to enable it.

I changed a test CentOS VM and the results were interesting. Check out the idle CPU prior to reboot(spiked activity) and after. Changing this in 1 - 2 VMs, may not yield much for results. However, across 15-30 per host, as we consistently run on our hosts in the farm, we can gain back some needed processing powa!

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