What does it really mean when a guest CPU is pegged?

[admin]

Hey All,

This question has been nagging at me for awhile.

From what I understand, each thread within the guest OS is multi-threaded and distributed by ESXi amonst the different cores available in the host.  So not every thread in a guest is on the same CPU core on the host.  Adding additional vCPU's to a guest increases the scheduling priority of the threads coming from that guest.

So my question, is a guest vCPU throttled in any way? (not couting reservations and resource pools).  Sometimes I will see a guest VM with a pegged vCPU (100%), but none of the physical CPU's on the host are pegged.  It looks as though the host is throttling the guest a bit, even though none of the physical host CPU cores are pegged.

Thanks,

Drew

[shishir08]

ASFAIK there is no such thing like throttling of guest vCPU in anyway.Yes the more the number of vCPU assigned to the VM the more scheduling overhead and all such things comes into picture.CPU load is generated by the guest and its applications as well ESX  Server as it provides a virtual interface to the hardware.  While the  work performed by the host does result in some increase in load, the  great majority of processing is due to the applications in the VM.  A  solid understanding of the workload profile regardless of the virtual  environment can assist CPU analysis.A better sign of over-utilization on a host is ready time (%RDY).  When  any world's ready time starts to climb, that world is spending the  reported percentage of its time waiting for some CPU to become available  for work.  Ready time above 10% is worth investigation and may be a  sign of an over-utilized host.

[UmeshAhuja]

Hi,

CPU are the processors of the Machine whereas Cores are the thread of the CPU.

Your CPU might be having high number/equal number of Physical Processors with single core, So in that case Your VM will show 100% of utilization because the VM wait in the quie till the VMkernel get free the number of CPU what you have assign to VM.

Try giving less number of CPU and high number of Core for better performance