Hi All, I''m finding this results a bit surprising , could some please explain whether this is the expected behavior. I''m running a single threaded application ( calculating pi for many decimal points ). Each VM has 1 vcpu with 128MB of ram. The physical box has quad-core processor ( HT disabled ). When I increase the number of VMs the time it takes to calculate the result taking longer ( Performance goes down ). I could clearly see that each VM will just use 1 CPU when it is running the tests. Why there is a such a huge jump in time although there are enough physical cores available ( at least upto 3 Vms) ? Please let me know if any more information is necessary. VM1 – 31.85 Number of VMs. VM1 – 35.98 VM2 – 36.11 Number of Vms VM1 - 43.57 VM2 - 42.55 VM3 -42.48 Number of VMs VM1 - 51.093 VM2 - 49.953 VM3 - 50.141 VM3 - 49.844 XEN version dpkg -l | grep -i xen ii libc6-xen 2.11.2-6 Embedded GNU C Library: Shared libraries [Xen version] ii libxenstore3.0 4.0.1-1 Xenstore communications library for Xen ii linux-image-2.6.32-5-xen-686 2.6.32-23 Linux 2.6.32 for modern PCs, Xen dom0 support ii xen-hypervisor-4.0-amd64 4.0.1-1 The Xen Hypervisor on AMD64 ii xen-tools 4.2-1 Tools to manage Xen virtual servers ii xen-utils-4.0 4.0.1-1 XEN administrative tools ii xen-utils-common 4.0.0-1 XEN administrative tools - common files ii xenstore-utils 4.0.1-1 Xenstore utilities for Xen All guest machines ''uname -a'' Linux vm1 2.6.32-5-xen-686 #1 SMP Thu Aug 12 18:09:47 UTC 2010 i686 GNU/Linux xm dmesg| grep -i credit (XEN) Using scheduler: SMP Credit Scheduler (credit) xm sched-credit Name ID Weight Cap Domain-0 0 256 0 vm1 57 256 100 vm2 58 256 100 Dom0 is pinned to CPU0. Name ID VCPU CPU State Time(s) CPU Affinity Domain-0 0 0 0 r-- 6907.9 0 Domain-0 0 1 - --p 74.9 any cpu Domain-0 0 2 - --p 92.4 any cpu Domain-0 0 3 - --p 62.2 any cpu vm1 57 0 2 -b- 6614.7 any cpu vm2 58 0 1 -b- 5797.1 any cpu -- Dkar _______________________________________________ Xen-users mailing list Xen-users@lists.xensource.com http://lists.xensource.com/xen-users