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I think the fact that RamFilter can't deal with huge pages is a bug , duo
to this limit, we have to set a balance  between normal memory and huge
pages to use RamFilter and NUMATopologyFilter. what do you think Jay?


On Wed, Sep 6, 2017 at 9:22 PM, Jay Pipes <jaypipes at gmail.com> wrote:

> On 09/06/2017 01:21 AM, Weichih Lu wrote:
>
>> 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.
>>
>
> You need to reserve fewer 1GB huge pages than 50 if you want to launch a
> 16GB instance on a host with 64GB of RAM. Try reserving 32 1GB huge pages.
>
> Best,
> -jay
>
> 2017-09-06 1:47 GMT+08:00 Jay Pipes <jaypipes at gmail.com <mailto:
>> 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/
>>     <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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-- 
Tang Yaguang
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