If you are on 4.3 -> disable transparent hugepages both Hypervisor and VM.
If you are using 4.4 -> disable transparent hugepages and also cobfigure regular huge pages.

Best Regards,
Strahil Nikolov

On Wed, Sep 29, 2021 at 5:34, Tommy Sway
<sz_cuitao@163.com> wrote:
From the Oracle OLVM support:

Configuring the Hugepages for guest VMs should be suffice, however, it needs the KVM hosts too configured with the Hugepages.
Since, if it not you may end with issues while staring the guest VMs.

I really don't know what to do now.





-----Original Message-----
From: users-bounces@ovirt.org <users-bounces@ovirt.org> On Behalf Of Strahil Nikolov via Users
Sent: Tuesday, September 28, 2021 3:39 PM
To: 'users' <users@ovirt.org>; Tommy Sway <sz_cuitao@163.com>
Subject: [ovirt-users]Re: 回复: Re: About the vm memory limit

I think that if you run VMs with Databases, you must disable transparent huge pages on Hypervisour level and on VM level. Yet, if you wish you can use regular huge pages on VM level.

Best Regards,
Strahil Nikolov






В вторник, 28 септември 2021 г., 09:21:09 ч. Гринуич+3, Tommy Sway <sz_cuitao@163.com> написа:






What problem will appear if I use the default transparent huge page enabled mode for physical hosts, but configure traditional huge page memory on the virtual machine for database SGA ?
Or is it better to disable transparent huge page on physical machines and still use traditional huge page memory on virtual machines?

Which one is prefer ?


From: users-bounces@ovirt.org <users-bounces@ovirt.org> On Behalf Of Strahil Nikolov via Users
Sent: Tuesday, September 28, 2021 12:05 AM
To: ‪‪‪tommy <sz_cuitao@163.com>; 'users' <users@ovirt.org>
Subject: [ovirt-users]Re: 回复: Re: About the vm memory limit

https://docs.oracle.com/en/database/oracle/oracle-database/19/ladbi/disabling-transparent-hugepages.html

https://access.redhat.com/solutions/1320153 (requires RH dev subscription or other type of subscription) -> In short add 'transparent_hugepage=never' to the kernel params

SLES11/12/15 -> https://www.suse.com/c/sles-1112-os-tuning-optimisation-guide-part-1/


Best Regards,
Strahil Nikolov





> On Mon, Sep 27, 2021 at 16:33, ‪‪‪tommy <sz_cuitao@163.com> wrote:
> thank you!

> and how to get the config info of Transparent huge pages and how to
> disable it?



>
>
> 发自我的华为手机
>
>
> -------- 原始邮件 --------
> 发件人: Strahil Nikolov <hunter86_bg@yahoo.com>
> 日期: 2021年9月27日周一 21:13
> 收件人: 'users' <users@ovirt.org>, Tommy Sway <sz_cuitao@163.com>
> 主 题: Re: [ovirt-users] Re: About the vm memory limit
>> 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 NikolovВ 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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