[pve-devel] [PATCH V2 qemu-server 0/2] enable balloon free-page-reporting
Alexandre Derumier
aderumier at odiso.com
Sun Mar 6 13:46:45 CET 2022
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
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