14 Replies Latest reply on Nov 22, 2006 4:33 AM by MIAMIDAVE

    CITRIX GUEST O/S HIGH CPU

    MIAMIDAVE Enthusiast

      I have Dell 2850 2.8 dual core attached to netapp storevaults500 using iscsi software initiator.  I only have 1 guest os Citrix) 4gb ram and 4 processors assigned.  Everything is working fine but want to tweak performance a little more.  I am getting high cpu spiking on some legacy applications.  Would anyone reccomend turning off hyperthreading?  I amy only add 1 or 2 small guests if needed for the future.

        • 1. Re: CITRIX GUEST O/S HIGH CPU
          MR-T Champion

          Are you saying your guest has 4GB of RAM and 4 vcpu's assigned?

           

          This is something I'd reduce to a single vcpu if possible.

          • 2. Re: CITRIX GUEST O/S HIGH CPU
            MIAMIDAVE Enthusiast

            I want to get the most cpu out of the guest.  How would I get more with 1?

            • 3. Re: CITRIX GUEST O/S HIGH CPU
              MR-T Champion

              Are the applications making use of all these cpus? Are they multi-threaded?

               

              I don't want to flog a dead horse, but if you search these forums you'll see lots of posts on how virtual machines with multiple cpus require physical cpus free to co-schedule.

               

              Example - When you run a virtual machine with a single vcpu on a 4-way server, it has a choice of 4 processors to execute on and will take the first physical CPU which is idle.

               

              When you have a dual vcpu virtual machine, the same rule applies but this time it needs to have 2 physical cpu's idle before it can execute any instructions.

               

              Now, imagine you've got 4 vcpus waiting for all 4 physical processors to become idle before being able to execute. This is why you need to avoid this scenario. Even if you're only running a single vm on a server they'll be certain internal tasks which require CPU time and you're machine will back off whilst these are executed.

               

              I was speaking to a guy from Citrix lastweek at VMworld and they (Citrix) will be releasing a whitepaper in the next few weeks to explain some best practices and test results.

               

              You'll find most people recommend single or dual vcpu's at a push.

              • 4. Re: CITRIX GUEST O/S HIGH CPU
                MIAMIDAVE Enthusiast

                Great.  I will look for the paper.  In the mean time I should probably knock the cpus down to 1 or 2.

                • 5. Re: CITRIX GUEST O/S HIGH CPU
                  MR-T Champion

                  Good plan.

                   

                  If you reduce to 2 you should see some improvement.

                   

                  The only thing you've got to watch now is the multi-processor HAL will be running on the vm.

                   

                  If you reduce your machine to a single vcpu, you should also look at moving the HAL back to uni-processor.

                   

                  Failure to do this won't cause any real harm, but there's a slight overhead.

                  • 6. Re: CITRIX GUEST O/S HIGH CPU
                    MIAMIDAVE Enthusiast

                    Reduced to 2 and now running even slower.  I have been reading other posts saying that 1 would be best.  Dont know where to go from here.

                    • 7. Re: CITRIX GUEST O/S HIGH CPU
                      TomHowarth Guru
                      vExpertUser Moderators

                      What applications are you providing via Citrix?

                       

                      what is the guest OS NT4, Win2000, Win2k3?

                       

                      what version of Citrix are your running?

                       

                      is this the only server in your ctirx farm?

                       

                      How many users are accessing the application?

                       

                      Are they being presented with a published desktop or Published applications?

                       

                      Message was edited by:

                              tom howarth

                       

                      Message was edited by:

                              tom howarth

                      • 8. Re: CITRIX GUEST O/S HIGH CPU
                        MIAMIDAVE Enthusiast

                        Applications are a mix of accounting applications.  Quickbooks, profx.  The guest is 2003 enterprise w 6gb of ram.  I am publishing the desktop in Access essentials.  I can see a noticeable difference when switching between 2 and 4 cpus.  I will have a max of 25 user.  I had a consulting company do the Citrix implementation.  It is the only server in the farm.

                        • 9. Re: CITRIX GUEST O/S HIGH CPU
                          TomHowarth Guru
                          User ModeratorsvExpert

                          first things first,  Accounting applications are notorius CPU hogs,  so I can understand the reason for a large amount of CPU,  however it is causing you issues in a virtual environment due to processor queueing.  this is why you have seen a proformance increase with the dropping of CPU.

                           

                          I personally would have gone for a solution of 4 single CPU Citrix servers, as this would have spread the load of your users and  would most probably gain a better user load as well, 

                           

                          as you are using the enterprise version of Windows 2003 there is no extra cost for licensing as you can utilse upto 4 virtual machines per physical license.  also CTX is licenced per user not per server so grow your farm.  I would be questioning the skills of the consulting company, they may think they know Citrix but they definatly don't understand ESX.  PM me your plans and I'll look them over.

                          1 person found this helpful
                          • 10. Re: CITRIX GUEST O/S HIGH CPU
                            MIAMIDAVE Enthusiast

                            Do you think I should reinstall the O/S and give 1 processor.  Then clone the guest to add additional servers to the original farm.  I dont want to have to reinstall from scratch but I will if I have to.  I would love to get my guest from multi smp to uni without blowing it up.

                            • 11. Re: CITRIX GUEST O/S HIGH CPU
                              TomHowarth Guru
                              vExpertUser Moderators
                              1 person found this helpful
                              • 12. Re: CITRIX GUEST O/S HIGH CPU
                                MIAMIDAVE Enthusiast

                                I can still do the HAL downgrade even if the HAL was never UNI?

                                • 13. Re: CITRIX GUEST O/S HIGH CPU
                                  TomHowarth Guru
                                  vExpertUser Moderators

                                  thats the beauty if Virtualisation,  then sysprep the server and copy the vmk files and you are off.

                                  • 14. Re: CITRIX GUEST O/S HIGH CPU
                                    MIAMIDAVE Enthusiast

                                    Thanks to Mike L's post I was able to convert the HAL back to UNI using the devcon tool and a script.