Hi, Currently, if a guest vm allocate a memory page, and freed it later in the guest, the memory is not freed on the host side.
Balloon device have a new option since qemu 5.1 "free-page-reporting" (and need host kernel 5.7) https://events19.linuxfoundation.org/wp-content/uploads/2017/12/KVMForum2018.pdf https://lwn.net/Articles/759413/ This is working like the discard option for disk, memory is freed async by the host when vm is freeing it. I'm running it production since 1 month without any problem. With a lot of vms and spiky workload, the memory freed is really huge. Here an example of a host with 650GB+200GB ksm going down to 250GB memory https://mutulin1.odiso.net/ballon-size.png (around 400vms with 2GB max memory, previously always allocated) This patch enabled it by default force machine version >= 6.2. changelogv2: - enabled it only for machine version > 6.2 - add test Alexandre Derumier (2): enable balloon free-page-reporting add test for virtio-balloon free-page-reporting=on. (qemu 6.2) PVE/QemuServer.pm | 4 ++- test/cfg2cmd/q35-simple-7.0.conf.cmd | 2 +- .../simple-balloon-free-page-reporting.conf | 15 +++++++++ ...imple-balloon-free-page-reporting.conf.cmd | 33 +++++++++++++++++++ 4 files changed, 52 insertions(+), 2 deletions(-) create mode 100644 test/cfg2cmd/simple-balloon-free-page-reporting.conf create mode 100644 test/cfg2cmd/simple-balloon-free-page-reporting.conf.cmd -- 2.30.2 _______________________________________________ pve-devel mailing list pve-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel
