[Starlingx-discuss] Question - Using 1Gb mem pages

[Michel Thebeau]

On 2018-10-19 1:45 p.m., Perez, Ricardo O wrote:
> Hello,
>
> I'm trying to execute a test, which his goal is to made use of huge pages (2M / 1G) launching a VM.
>
> I have already verified the configuration of the controllers GRUB options and we have defined the variable hugepagesz=1G, however, inside the same parameters list, there is a "default_hugepagesz=2M". The default hugepagesz, has been modified to 1G, and the compute has been restarted with no issues.


Hi Ricardo,

You wrote, "controllers GRUB options" then "the compute has been 
restarted with no issues".  Is there a GRUB option one can configure on 
the controller that is for the computes?  I don't remember seeing one.  
If you're actually changing /etc/default/grub, I doubt that's supported. 
I did not find a procedure for changing default_hugepagesz  on 
controllers or computes grub configuration.

It's supposed to be an option, for example through in horizon interface 
or 'system host-memory-modify'... but you didn't quote either of those.


>
> The flavor has been modified, with the following option: " hw:mem_page_size=104875"  (1G) page.


Is "104875" a typo?  It looks a lot like 1024 * 1024 = 1048576, but not 
quite.


M


>
> However when I launch a VM using the modified flavor it creates the VM, but if I check the field values of the VM using " openstack server show <vm_name>". I'm getting the following value for pgsize:
> wrs-res:topology                    | node:0,   512MB, pgsize:2M, vcpus:0, pol:sha |
>
> So, seems like it's still taking the 2M pagesize instead of the 1G.
>
> What I have already tried is to:
>
> *        Change also the image metadata: hw:mem_page_size=large and also 104875. Result, VM launched successfully, but pgsize value still 2M.

There's the interesting "104875" again.


> *        Leave the GRUB default values, and use modified flavor to hw:mem_page_size=104875, launch the VM with ERROR status.

104875

> *        Leave the GRUB default values, and use modified flavor to hw:mem_page_size=2048, launch the VM with success, , pgsize value is 2M, which is expected, ok.
>
> *        Leave the GRUB default values, and use modified flavor to hw:mem_page_size=small launch the VM with success, , pgsize value is 4k, which is  expected, ok.
>
> *        Leave the GRUB default values, and use modified flavor to hw:mem_page_size=any launch the VM with success, , pgsize value is 2M, which is  expected, ok.
>
> Could be this an issue trying to use 1G mem pages or do I'm missing some other configuration parameter?
>
> Thanks in advance for your help
>
>
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