[pve-devel] [PATCH qemu-server 0/1] enable balloon free-page-reporting

[Alexandre Derumier <aderumier@odiso.com>]

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.


This patch enabled it by default,

This don't break live migration  from old qemu process with non-enable free page hinting -->  new qemu process with enabled free page hinting,
but this break migration in the reverse way.


So I can enabled it by default for next qemu machine version or add an extra option to enable it.
I don't known if we could extend the "baloon" option ? or add an extra option like "balloonoptions: ..." ?

What do you think about it ?


Alexandre Derumier (1):
  enable balloon free-page-reporting

 PVE/QemuServer.pm | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

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2.30.2