[PVE-User] Hotplug Memory boots VM with 1GB

Tue Sep 6 17:02:24 CEST 2016

Hello,

I had the same problem today while migrating from proxmox 3..

Fortunatly i found this is fixed in recent Redhat kernel ! (2015-07-22 kernel-2.6.32-517.el6)
So i just upgraded the kernel on all my vms and everything works fine. \o/

Here's the bugzilla : https://bugzilla.redhat.com/show_bug.cgi?id=1150510

Cheers,
Alexandre.

Le 15/04/2015 à 17:40, Brian Hart a écrit :
Alexandre --

Thanks for the response.  Yes, ACPI hotplug does work and is built into the kernel in CentO 6.  ACPI hotplug has actually been supported since CentOS 5 as well.  I am able to hotplug disks, network, CPU and Memory once the system is fully booted and ACPI does identify the event.  It just seems that its a timing issue when proxmox tries to hotplug the memory I think that Linux/ACPI isn't ready for it that early (at least for CentOS 6).  Hope this helps - let me know if I can gather any other information for you.  We really weren't looking to move to CentOS 7 for a while since CentOS 6 isn't EOL until 2020 and there is some reluctance in our group around some of the changes in RHEL/Cent 7.

Thanks,
Brian

On Wed, Apr 15, 2015 at 1:27 AM, Alexandre DERUMIER <aderumier at odiso.com<mailto:aderumier at odiso.com>> wrote:
>>Yes, I do have the udev rules in place and when I increase the memory in the web gui from say 4GB to 4.5GB it will add all of the memory that it was missing from boot plus the additional 500. When I look in >>/sys/devices/system/memory it only lists the memory modules that were from when the system was on. I can also see in dmesg output "Hotplug Mem Device" from during boot but its almost like the kernel isn't getting notified >>during boot and which also keeps udev from ever seeing it and setting it to online. CentOS 6 should have no problem with hotplugging memory but it doesn't seem to take it with the way Proxmox handles it at boot.

So,it's seem than acpi hotplug is not working.
Can you hotplug virtio disk for example ?

Also, I'm not sure that centos6 2.6.32 kernel have support for memory hotplug (maybe redhat has backported from 3.10 kernel, but I can't confirm)

----- Mail original -----
De: "Brian Hart" <brianhart at ou.edu<mailto:brianhart at ou.edu>>
À: "aderumier" <aderumier at odiso.com<mailto:aderumier at odiso.com>>
Cc: "proxmoxve" <pve-user at pve.proxmox.com<mailto:pve-user at pve.proxmox.com>>
Envoyé: Lundi 13 Avril 2015 04:36:43
Objet: Re: [PVE-User] Hotplug Memory boots VM with 1GB

Hi - Thanks for the response!
Yes, I do have the udev rules in place and when I increase the memory in the web gui from say 4GB to 4.5GB it will add all of the memory that it was missing from boot plus the additional 500. When I look in /sys/devices/system/memory it only lists the memory modules that were from when the system was on. I can also see in dmesg output "Hotplug Mem Device" from during boot but its almost like the kernel isn't getting notified during boot and which also keeps udev from ever seeing it and setting it to online. CentOS 6 should have no problem with hotplugging memory but it doesn't seem to take it with the way Proxmox handles it at boot.

Thanks!

Brian

On Sun, Apr 12, 2015 at 11:18 AM, Alexandre DERUMIER < aderumier at odiso.com<mailto:aderumier at odiso.com> > wrote:

Hi,

do you have the udev rules

/lib/udev/rules.d/80-hotplug-cpu-mem.rules (not sure about centos path)

SUBSYSTEM=="memory", ACTION=="add", TEST=="state", ATTR{state}=="offline", ATTR{state}="online"

This is udev which enable the memory module after acpi hotplug.

----- Mail original -----
De: "Brian Hart" < brianhart at ou.edu<mailto:brianhart at ou.edu> >
À: "proxmoxve" < pve-user at pve.proxmox.com<mailto:pve-user at pve.proxmox.com> >
Envoyé: Vendredi 10 Avril 2015 18:28:15
Objet: Re: [PVE-User] Hotplug Memory boots VM with 1GB

Hello All,
I had some more time to play with memory hotplugging and was trying to make this work again. I noticed in the wiki it says it requires a kernel greater than 3.10. I was trying to get this to work with CentOS 6 systems as that is primarily what we are running and it is not on a 3.x kernel yet. However, Cent 6 does support hotplugging memory and CPU. I think the issue though is the memory is hotplugged at an an odd time that the VM isn't ready for it with CentOS 6. Once the system boots I still see 987MB of starting memory and if I increase the amount of memory through the proxmox GUI the VM immediately detects all of the memory it was supposed to have plus the additional memory I just added. I have also found that I can manually tell it to probe for memory by doing an "echo 0x100000000 > /sys/devices/system/memory/probe" and it will find one piece (you have to do this repeatedly for every module if it doesn't auto-detect the hotplug).

Anybody have an idea of how to tell CentOS 6 to detect the hotplugged memory after boot? Also, I'm curious why the additional memory has to be hotplugged? When using VMware it doesn't do it in this way so how come KVM/QEMU does?

Thanks,

Brian

On Sun, Mar 8, 2015 at 8:16 PM, Brian Hart < brianhart at ou.edu<mailto:brianhart at ou.edu> > wrote:

Ah, you're absolutely right. It is in the wiki. I had skipped to the bottom part of the wiki that said "Memory Hotplug' and overlooked the part that referenced Linux guests specifically. It looks like it is probably udev rules I'm missing. I will look at adding that in and try again.
Thank you for the follow up!

Brian

On Sun, Mar 8, 2015 at 12:16 PM, Alexandre DERUMIER < aderumier at odiso.com<mailto:aderumier at odiso.com> > wrote:

BQ_BEGIN
I have updated the wiki last month about memory && cpu hotplug

https://pve.proxmox.com/wiki/Hotplug_%28qemu_disk,nic,cpu,memory%29

----- Mail original -----
De: "Brian Hart" < brianhart at ou.edu<mailto:brianhart at ou.edu> >
À: "proxmoxve" < pve-user at pve.proxmox.com<mailto:pve-user at pve.proxmox.com> >
Envoyé: Samedi 7 Mars 2015 06:36:32
Objet: [PVE-User] Hotplug Memory boots VM with 1GB

Hello -
I'm not sure if I'm running into a bug or if I'm missing something. I have done several tests playing with different settings for a VM and have found that consistently whenever I set Hotplug to allow memory it limits the guest VM to 1GB of memory even if I have more assigned to it at startup. Has anybody else seen this? Is there something special about the hotplug that this is expected that I'm not aware of?

Thanks,
Brian Hart

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