[Openstack] [OpenStack] Can Mitaka RamFilter support free hugepages?
Sahid Orentino Ferdjaoui
sferdjao at redhat.com
Thu Sep 7 20:27:09 UTC 2017
On Wed, Sep 06, 2017 at 11:57:25PM -0400, Jay Pipes wrote:
> Sahid, Stephen, what are your thoughts on this?
>
> On 09/06/2017 10:17 PM, Yaguang Tang wrote:
> > 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?
Huge Pages has been built on top of the NUMA Topology
implementation. You have to consider isolate all hosts which are going
to handle NUMA instances to a specific host aggregate.
We don't want RAMFilter to handle any NUMA related feature (in Nova
world: hugepages, pinning, realtime...) but we don't want it blocking
scheduling and that should not be the case.
I'm surprised to see this bug I think libvirt is reporting the total
amount of physical RAM available on the host and that is not depending
of the size of the pages.
So If that is true libvirt is reporting only the amount of small pages
memory available we will probably have to fix that point instead of
the RAMFilter.
That because we don't want to add "hack" on all filters to just pass
when instances provide NUMA Topology constraints and we can't
configure the scheduler to use specific filters per aggregate.
s.
> >
> >
> > On Wed, Sep 6, 2017 at 9:22 PM, Jay Pipes <jaypipes at gmail.com
> > <mailto: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> <mailto: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/>
> > <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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