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Memory monitor xp12/25/2023 ![]() ![]() If you do enable ballooning, the KVM process will not release the memory back to the host but the guest may report a reduced memory availability which can be manually recovered using the KVM monitor using the balloon command. Note that if you are passing through a physical PCI(e) device or a Virtual Function I/O (VFIO) Mediated device (MDEV) such as a vGPU, then ballooning will not work since these devices are mapped to fixed memory addresses in the host and in the guest. If set too aggressively, some applications in the guest may run out of memory as a result and your guest's OOM killer may activate, killing important processes. Note that the Guest cannot ask for the memory back until the host has 'deflated' this balloon. The VM (Windows or Linux) knows best which memory regions it can give up without impacting performance of the VM. The VM decides which processes or cache pages to swap out to free up memory for the balloon. ![]() The Proxmox VE host can loan ballooned memory to a busy VM. It reduces the impact your guest can have on memory usage of your host by giving up unused memory back to the host. Memory ballooning (KVM only) allows you to have your guest dynamically change it’s memory usage by evicting unused memory during run time. If you don't care about memory optimization but care about save CPU overhead produced by KSM, in Proxmox >= 4.x you can disable it with: The file /etc/nf allows for some customization of its behaviour. Watch cat /sys/kernel/mm/ksm/pages_sharing Howto verify that KSM is working (how many pages are being shared between your KVM guests): You will notice higher CPU activities on the host (ksm daemon) and the used memory on the host will be lowered significantly (see start page showing the overall memory usage). Just install several KVM virtual machines with the same OS (using at least 80% of your physical memory on the host) and wait a few minutes. It was integrated in PVE since version 1.5, and is implemented with the package "ksm-control-daemon" (check your version with the cli command "pveversion -v"). One of the great benefits of using Linux as the hypervisor means KSM is not limited to KVM and virtual machines, but can also reduce memory pressure with normal Linux applications. With KSM we're able to improve virtual machine density by as much as 300% without impacting performance. KSM (Kernel Samepage Merging) is running in the Linux kernel and scans the memory of all the virtual machines running on a single host, looking for duplication and consolidating. KSM and Auto-Ballooning enables sophisticated and economic configurations for physical RAM utilization. Optimized and effective memory management is a key factor in virtualization environments. 3.2.6 Enable Auto-Ballooning on Windows 2003 / Windows Xp.3.2.5 Enable Auto-Ballooning on Windows 2008r2.3.2.4 Enable Auto-Ballooning on Windows Server 2012 / Windows 8.1 or newer. ![]()
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