Co-Stop (%CSTP) is the percentage of time that a SMP virtual machine was ready to run, but incurred delay due to co-vCPU scheduling contention. To remedy Co-Stop on a VM, decrease the number of vCPUs on that VM. If there are multiple VMs with high %CSTP on a host, it is likely a sign of CPU contention and resource starvation due too many vSMP VMs on that host. Migrate some of those VMs off to other hosts to re-balance the load in the cluster and also, decrease the number of vCPUs allocated to those VMs to see if the %CSTP goes to zero.
VM CPU Co-stop (%CSTP) Alert in Virtualization Manager
VM CPU Co-Stop Alert Viewer in Virtualization Manager