How to make the virtualbox get more cpu resource

[ranhui]

I have a Dell server with windows server 2012 and I installed a virtualbox to run a ubuntu 12.04 in it. The server have two cpu and each of them have six core.

But when I run some calcuation in the ubuntu, I found that the CPU in Windows never get a high rank, most of the time 10% CPU is used in the task manager. But in ubuntu, the htop show the CPU is 100% used.

So I think the virtualbox do not get access to all the cpu resource. I tried to change the CPU count in the virtualbox configuration but it did not work. So is there any way to make my virtualbox system get more resources from the windows server? I want to make full use of the Server not just 10% used.

Thank you.

[mpack]

You appear to misunderstand how multi-core CPUs work.

Applications generally can't be forced to use multiple cores, they have to be designed to work that way.

Most applications are not designed to require more than 1 core. Hence multiple cores are most useful for running multiple apps smoothly.

In short, multiple cores do not usually make a single application run any faster. Also, if an application is heavily dependant on I/O then multiple cores won't make it go faster even if it was designed to use them. These are facts that CPU sellers generally gloss over in order to maintain the fiction of Moore's law.

[ranhui]

You appear to misunderstand how multi-core CPUs work.

Applications generally can't be forced to use multiple cores, they have to be designed to work that way.

Most applications are not designed to require more than 1 core. Hence multiple cores are most useful for running multiple apps smoothly.

In short, multiple cores do not usually make a single application run any faster. Also, if an application is heavily dependant on I/O then multiple cores won't make it go faster even if it was designed to use them. These are facts that CPU sellers generally gloss over in order to maintain the fiction of Moore's law.

So it means that I can not improve the performance because virtualbox is just one program and can not make it use more than on core?

[socratis]

VirtualBox can and will use multiple cores. mpack was talking about the program in your guest (Ubuntu). What is the process in Ubuntu that is eating your CPU?

[ranhui]

VirtualBox can and will use multiple cores. mpack was talking about the program in your guest (Ubuntu). What is the process in Ubuntu that is eating your CPU?

Oh, it depends. Sometimes it may be a python script or some program to sort a big txt file.

[mpack]

Actually I was making observations about "most apps" without regard to whether they run on host or guest. VirtualBox is not "most apps": VBox has been designed to take advantage of multiple cores, in the sense that it makes them available to the guest OS.

However, even if VBox makes multiple cores available to the guest OS - "most apps" inside the guest are subject to the same observations. So, unless the guest app is designed to use multiple cores, then all but one of the cores assigned to the guest will be wasted, unless you run multiple guest apps, and none of heavily relying on I/O.

I doubt that a python script will ever use more than one core, unless it splits off subtasks and allows them to run asynchronously. If you start to work out the difficulties inherent in this you may understand why most apps are written to use a single core.