Open Stack

Thanks for your response.

Is this mean if I want to create an instance with flavor: 16G memory
(hw:mem_page_size=large),
I need to preserve memory more than 16GB ?
This instance consume hugepages resource.

2017-09-06 1:47 GMT+08:00 Jay Pipes <jaypipes at gmail.com>:

> Please remember to add a topic [nova] marker to your subject line. Answer
> below.
>
> On 09/05/2017 04:45 AM, Weichih Lu wrote:
>
>> Dear all,
>>
>> I have a compute node with 64GB ram. And I set 50 hugepages wiht 1GB
>> hugepage size. I used command "free", it shows free memory is about 12GB.
>> And free hugepages is 50.
>>
>
> Correct. By assigning hugepages, you use the memory allocated to the
> hugepages.
>
> Then I launch an instance with 16GB memory, set flavor tag :
>> hw:mem_page_size=large. It show Error: No valid host was found. There are
>> not enough hosts available.
>>
>
> Right, because you have only 12G of RAM available after
> creating/allocating 50G out of your 64G.
>
> Huge pages are entirely separate from the normal memory that a flavor
> consumes. The 16GB memory in your flavor is RAM consumed on the host. The
> huge pages are individual things that are consumed by the NUMA topology
> that your instance will take. RAM != huge pages. Totally different things.
>
>  And I check nova-scheduler log. My
>
>> compute is removed by RamFilter. I can launch an instance with 8GB memory
>> successfully, or I can launch an instance with 16GB memory sucessfully by
>> remove RamFilter.
>>
>
> That's because RamFilter doesn't deal with huge pages. Because huge pages
> are a different resource than memory. The page itself is the resource.
>
> The NUMATopologyFilter is the scheduler filter that evaluates the huge
> page resources on a compute host and determines if the there are enough
> *pages* available for the instance. Note that I say *pages* because the
> unit of resource consumption for huge pages is not MB of RAM. It's a single
> memory page.
>
> Please read this excellent article by Steve Gordon for information on what
> NUMA and huge pages are and how to use them in Nova:
>
> http://redhatstackblog.redhat.com/2015/09/15/driving-in-the-
> fast-lane-huge-page-support-in-openstack-compute/
>
> Best,
> -jay
>
> Does RamFilter only check free memory but not free hugepages?
>> How can I solve this problem?
>>
>> I use openstack mitaka version.
>>
>> thanks
>>
>> WeiChih, Lu.
>>
>> Best Regards.
>>
>>
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