Transparent huge pages are enabled by default, so you need to stop them.
I would use huge pages on both host and VM, but theoretically it shouldn't be a problem running a VM with enabled HugePages without configuring on Host.
Best Regards,
Strahil Nikolov
В събота, 25 септември 2021 г., 15:25:10 ч. Гринуич+3, Tommy Sway <sz_cuitao@163.com> написа:
transparent huge pages are not used on vm and physical host.
But, can I enable hugepage memory on virtual machines but not on a physical machine?
For database running on vm, and it needs to config hugepage.
From: Strahil Nikolov <hunter86_bg@yahoo.com> Sent: Saturday, September 25, 2021 5:32 PMTo: Tommy Sway <sz_cuitao@163.com>Subject: Re: [ovirt-users] About the vm memory limit
It depends on the numa configuration of the host.
If you have 256G per CPU, it's best to stay into that range.
Also, consider disabling transparent huge pages on the host & VM.
Since 4.4 Regular Huge Pages (do not confuse them with THP) can be used on the Hypervisors, while on 4.3 there were some issues but I can't provode any details.
Best Regards,
Strahil Nikolov
> On Fri, Sep 24, 2021 at 6:40, Tommy Sway
> <sz_cuitao@163.com> wrote:
> I would like to ask if there is any limit on the memory size of virtual machines, or performance curve or something like that?
> As long as there is memory on the physical machine, the more virtual machines the better?
>
> In our usage scenario, there are many virtual machines with databases, and their memory varies greatly.
> For some virtual machines, 4G memory is enough, while for some virtual machines, 64GB memory is needed.
>
> I want to know what is the best use of memory for a virtual machine, since the virtual machine is just a QEMU emulation process on a physical machine, and I worry that it is not using as much memory as a physical machine. Understand this so that we can develop guidelines for optimal memory usage scenarios for virtual machines.
>
> Thank you!
>
>
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