[pve-devel] qemu memory hotplug limited to 64 dimm

[Alexandre DERUMIER]

I found some kernel patch to bump it to 509 (seem that another kvm fixed was needed)

http://www.spinics.net/lists/kvm/msg117654.html

But I think it was never commited to the kernel.

I'll try follow the discuss.

----- Mail original -----
De: "aderumier" <aderumier at odiso.com>
À: "dietmar" <dietmar at proxmox.com>
Cc: "pve-devel" <pve-devel at pve.proxmox.com>
Envoyé: Lundi 12 Décembre 2016 19:29:54
Objet: Re: [pve-devel] qemu memory hotplug limited to 64 dimm

>>Can't we simply increase that max_mem_regions default value? 

I'm trying to see why they have limited it to 64. 

maybe a qemu bug with previous qemu version? don't known. 

I have some big spare servers to test with 370G ram, i'll try to do test with them. 


----- Mail original ----- 
De: "dietmar" <dietmar at proxmox.com> 
À: "aderumier" <aderumier at odiso.com>, "pve-devel" <pve-devel at pve.proxmox.com> 
Envoyé: Lundi 12 Décembre 2016 17:09:41 
Objet: Re: [pve-devel] qemu memory hotplug limited to 64 dimm 

Can't we simply increase that max_mem_regions default value? 


> On December 12, 2016 at 4:54 PM Alexandre DERUMIER <aderumier at odiso.com> 
> wrote: 
> 
> 
> vhost 64 limit has been introduced here, because of qemu crash with bigger 
> value 
> 
> https://patchwork.kernel.org/patch/6709021/ 
> 
> ----- Mail original ----- 
> De: "aderumier" <aderumier at odiso.com> 
> À: "pve-devel" <pve-devel at pve.proxmox.com> 
> Envoyé: Lundi 12 Décembre 2016 16:51:11 
> Objet: [pve-devel] qemu memory hotplug limited to 64 dimm 
> 
> Hi, 
> 
> a proxmox user has reported problem to hotplug memory with high values (48G) 
> 
> https://forum.proxmox.com/threads/apt-get-upgrade-to-update-proxmox-server.30992/ 
> 
> 
> 
> Seem that qemu check about a vhost value 
> 
> https://lists.nongnu.org/archive/html/qemu-devel/2015-07/msg05998.html 
> 
> cat /sys/module/vhost/parameters/max_mem_regions > 64 (verified on my 
> servers). 
> 
> 
> I think this limit was not present when we have implemented hotplug. 
> 
> Not sure was we can do, but I think our method don't scale anymore :( 
> 
> Maybe should we introduce a new fixed "dimm size" option, to allow hotplug of 
> more memory ? 
> 
> 
> 
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