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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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