Extremely poor performance with VMWare hosted build server

We are running TeamCity on a Windows Server 2008 as a build server. The build server is hosted in VMWare ESXi 5. (I have very little VMWare experience so my terminology might be wrong).

When we start a build, we more often than not experience extremely poor performance. The build server guest has been assigned 4 CPUs with no upper limit and no other guest systems are very busy.

What we have observed using vSphere Client is that after a while the CPU rate drops from about 4600 MHz to about 50 MHz. When the build stops, the CPU frequency goes back to normal semi-idle rate.

Another interesting observation is that while the build server is working at about 50 MHz it gets a burst of CPU every six minutes (see graph).

Yet another observation is that the system clock loses time proportional to the missing CPU cycles (about a factor 100 in the low-CPU periods).

EDIT Added chart with host specs.

Solution 1:

What are the server's specifications? RAM, physical CPUs?

One thing you can try quickly is to cut your build server down to ONE or TWO virtual CPUs and repeat your trial. This is the preference, as it's easier for the hypervisor to allocate CPU time for a single vCPU versus finding four free cores to provide resources for four vCPUs you've provisioned.