[pve-devel] pve-manager : expose balloon to gui

[Alexandre DERUMIER]

>>Do you follow the discussion on the qemu-devel list?
Yes.

>> The virtio-balloon 
><driver only report free RAM, without information about buffers.
 Yes,I have see that.

 I need to do test, but if we use free ram counter, maybe buffer ram will be taked to go into free_ram if we reduce the memory with ballooning.

 ex:

 1)maxmem: 8GB - freeram:1G buffer:6G usedram:1G   balloon driver:0G

 ballon to 7G

 2)maxmem:8GB  - freeram:0G buffer:6G usedram:1G  balloon driver:1G
  then wait a little, guest kernel should take some buffered memory to go in free_mem.

2)maxmem:8GB  - freeram:1G buffer:5G usedram:1G  balloon driver:1G

So maybe using free_mem counter is enough ?
(We should of course check the swap to see if the kernel is not swapping to keep free mem)


But yes, having buffer stats could help a lot.



Note that citrix xenserver is using only the min_balloon size defined in vm config, it should be tunned to be enough big to not crash the guest if memory is reduced.
(in worst case you should have enough swap in guest to handle the memory reduce)


>>So maybe it is faster to work on the guest-agent infrastructure instead. I guess 
>>it is much easier to modify the user space tools than a kernel driver. 

Yes, I think we could implement qemu-ga for this. Easy for linux (get free command result), not sure for windows guest(lauching some scripts ?).
I don't have too much time to work on qemu-ga (multiplexing give me headache ;).
Can you work on this ? (my old patches works but need to be polished)


>>Note: fixing the kernel driver is quite easy, but I doubt we can force all distrib. to 
>>apply/backport those patches. 
Yes, I don't think distro will backport,I'll just be include in new kernel version. So it can take time.


>>They also talk about a kernel-based auto-ballooning feature! I requested more 
>>information about that. 
Never heart about this. But it can take time to be ready (years ?)


----- Mail original ----- 

De: "Dietmar Maurer" <dietmar at proxmox.com> 
À: "Alexandre DERUMIER" <aderumier at odiso.com> 
Cc: pve-devel at pve.proxmox.com 
Envoyé: Samedi 8 Décembre 2012 13:16:23 
Objet: RE: [pve-devel] pve-manager : expose balloon to gui 

> Subject: Re: [pve-devel] pve-manager : expose balloon to gui 
> 
> 
> >>They lock quite simple, so we can add them if they work fine. 
> Ok, thanks. I'll begin to work on it next week ! 

Do you follow the discussion on the qemu-devel list? The virtio-balloon 
driver only report free RAM, without information about buffers. 
So maybe it is faster to work on the guest-agent infrastructure instead. I guess 
it is much easier to modify the user space tools than a kernel driver. 

Note: fixing the kernel driver is quite easy, but I doubt we can force all distrib. to 
apply/backport those patches. 

They also talk about a kernel-based auto-ballooning feature! I requested more 
information about that.