4 Replies Latest reply on Jul 23, 2010 1:43 AM by Nikhil Patwa

    VM CPU kernel times too high

    Nikhil Patwa Expert

       

      Hello,

       

       

      My ESXi 4.0 VMs are showing too high kernel times, is there a way I can reduce the kernel times. Kernel times directly affects I/O, does it mean too high kernel times means lot of I/O is utilized. The VM is mostly used for MS Office applications by some 15-20 remote users.

       

       

      I would like to know ways on reducing the VM kernel times

       

       

      Regards

       

       

      Nikhil

       

       

        • 1. Re: VM CPU kernel times too high
          Linjo Champion
          User Moderators

           

          Is there any problems with the VM:s or a general question?

          What hardware is this running and what storage-protocols are used?

           

           

          Best regards,

          Linjo

           

           

           

          If you find this information useful, please award points for "correct" or "helpful".

           

           

          • 2. Re: VM CPU kernel times too high
            Nikhil Patwa Expert

            Hi,

            My ESXi Host server is Dell PowerEdge T710 with 2 RAID 5 Datastores (8 x 146GB, 15K RPM disks & 8 x 300GB, 10K RPM disks)

             

            The VM specifications are:

            CPU = 4

            RAM = 4GB

            hosted in the 15K RAID 5 datastore.

             

            Sometimes the servers becomes slow and while monitoring came to know the kernel times are very high. So far we have not faced any problems but am just curious to know what causes the kernel times to be so high and are there any ways to reduce it. Suprisingly the VM memory usage is very low.

             

            Regards

            Nikhil

            • 3. Re: VM CPU kernel times too high
              Linjo Champion
              User Moderators

               

              Depending on how many cores you have and how many virrtual machines it could be the problem with too many vCPU:s (4)

              Since every time the virtual machine needs to do something the hypervisor needs to find 4 empty slots to run the machine on.

               

               

              More vCPU:s does not mean more performance, quite frequently the other way around.

               

               

              Try to reduce the vCPU:s from 4 to 2 or even 1 (depending on the workload) and monitor the CPU Kernel times.

               

               

              Best regards,

              Linjo

               

               

               

              If you find this information useful, please award points for "correct" or "helpful".

               

               

              • 4. Re: VM CPU kernel times too high
                Nikhil Patwa Expert

                 

                Have reduced vCPUs in some VMs but still the kernel times are too high, I could not figure out what causes the Kernel times to be so high.

                 

                 

                The kernel times are not the same for all the VMs. I have seen kernel times in a VM accessed by many users in our office to be not so high and another VM that is accessed by only few users (2-3) to have high kernel times. Both the Vs have the same specifications interms of vCPU, memory

                 

                 

                Need to figure out how to control kernel times, improve performance of virtual machines

                 

                 

                Nikhil