openstack/nova
Code Issues Proposed changes

trivial: Rewrap guide at 79 characters

Browse Source 
Change-Id: Icdaaa341e1fff4ee63ede1e1a059d41960e96f48
This commit is contained in:
Stephen Finucane 2016-09-09 10:37:28 +01:00
parent 48a4fee10f
commit 3e92d21cd7
1 changed files with 100 additions and 121 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

221
doc/source/testing/libvirt-numa.rst
View File

@ -1,28 +1,25 @@
================================================
Testing NUMA related hardware setup with libvirt
================================================
This page describes how to test the libvirt driver's handling
of the NUMA placement, large page allocation and CPU pinning
features. It relies on setting up a virtual machine as the
test environment and requires support for nested virtualization
since plain QEMU is not sufficiently functional. The virtual
machine will itself be given NUMA topology, so it can then
act as a virtual "host" for testing purposes.
This page describes how to test the libvirt driver's handling of the NUMA
placement, large page allocation and CPU pinning features. It relies on setting
up a virtual machine as the test environment and requires support for nested
virtualization since plain QEMU is not sufficiently functional. The virtual
machine will itself be given NUMA topology, so it can then act as a virtual
"host" for testing purposes.
------------------------------------------
Provisioning a virtual machine for testing
------------------------------------------
The entire test process will take place inside a large virtual
machine running Fedora 21. The instructions should work for any
other Linux distribution which includes libvirt >= 1.2.9 and
QEMU >= 2.1.2
The entire test process will take place inside a large virtual machine running
Fedora 21. The instructions should work for any other Linux distribution which
includes libvirt >= 1.2.9 and QEMU >= 2.1.2
The tests will require support for nested KVM, which is not enabled
by default on hypervisor hosts. It must be explicitly turned on in
the host when loading the kvm-intel/kvm-amd kernel modules.
The tests will require support for nested KVM, which is not enabled by default
on hypervisor hosts. It must be explicitly turned on in the host when loading
the kvm-intel/kvm-amd kernel modules.
On Intel hosts verify it with
@ -52,9 +49,8 @@ While on AMD hosts verify it with
# cat /sys/module/kvm_amd/parameters/nested
1
The virt-install command below shows how to provision a
basic Fedora 21 x86_64 guest with 8 virtual CPUs, 8 GB
of RAM and 20 GB of disk space:
The virt-install command below shows how to provision a basic Fedora 21 x86_64
guest with 8 virtual CPUs, 8 GB of RAM and 20 GB of disk space:
.. code-block:: bash
@ -70,29 +66,28 @@ of RAM and 20 GB of disk space:
--cdrom /var/lib/libvirt/images/Fedora-Server-netinst-x86_64-21_Alpha.iso \
--os-variant fedora20
When the virt-viewer application displays the installer, follow
the defaults for the installation with a couple of exceptions
When the virt-viewer application displays the installer, follow the defaults
for the installation with a couple of exceptions
* The automatic disk partition setup can be optionally tweaked to
reduce the swap space allocated. No more than 500MB is required,
free'ing up an extra 1.5 GB for the root disk.
* The automatic disk partition setup can be optionally tweaked to reduce the
swap space allocated. No more than 500MB is required, free'ing up an extra
1.5 GB for the root disk.
* Select "Minimal install" when asked for the installation type
since a desktop environment is not required.
* Select "Minimal install" when asked for the installation type since a desktop
environment is not required.
* When creating a user account be sure to select the option
"Make this user administrator" so it gets 'sudo' rights
* When creating a user account be sure to select the option "Make this user
administrator" so it gets 'sudo' rights
Once the installation process has completed, the virtual machine
will reboot into the final operating system. It is now ready to
deploy an OpenStack development environment.
Once the installation process has completed, the virtual machine will reboot
into the final operating system. It is now ready to deploy an OpenStack
development environment.
---------------------------------
Setting up a devstack environment
---------------------------------
For later ease of use, copy your SSH public key into the virtual
machine
For later ease of use, copy your SSH public key into the virtual machine
.. code-block:: bash
@ -104,7 +99,7 @@ Now login to the virtual machine
# ssh <IP of VM>
We'll install devstack under $HOME/src/cloud/.
We'll install devstack under `$HOME/src/cloud/`.
.. code-block:: bash
@ -112,18 +107,17 @@ We'll install devstack under $HOME/src/cloud/.
# cd $HOME/src/cloud
# chmod go+rx $HOME
The Fedora minimal install does not contain git and only
has the crude & old-fashioned "vi" editor.
The Fedora minimal install does not contain git and only has the crude &
old-fashioned "vi" editor.
.. code-block:: bash
# sudo yum -y install git emacs
At this point a fairly standard devstack setup can be
done. The config below is just an example that is
convenient to use to place everything in $HOME instead
of /opt/stack. Change the IP addresses to something
appropriate for your environment of course
At this point a fairly standard devstack setup can be done. The config below is
just an example that is convenient to use to place everything in `$HOME`
instead of `/opt/stack`. Change the IP addresses to something appropriate for
your environment of course
.. code-block:: bash
@ -158,10 +152,9 @@ appropriate for your environment of course
# FORCE=yes ./stack.sh
Unfortunately while devstack starts various system services and
changes various system settings it doesn't make the changes
persistent. Fix that now to avoid later surprises after reboots
Unfortunately while devstack starts various system services and changes various
system settings it doesn't make the changes persistent. Fix that now to avoid
later surprises after reboots
.. code-block:: bash
@ -172,21 +165,20 @@ persistent. Fix that now to avoid later surprises after reboots
# sudo emacs /etc/sysconfig/selinux
SELINUX=permissive
----------------------------
Testing basis non-NUMA usage
----------------------------
First to confirm we've not done anything unusual to the traditional
operation of Nova libvirt guests boot a tiny instance
First to confirm we've not done anything unusual to the traditional operation
of Nova libvirt guests boot a tiny instance
.. code-block:: bash
# . openrc admin
# nova boot --image cirros-0.3.2-x86_64-uec --flavor m1.tiny cirros1
The host will be reporting NUMA topology, but there should only
be a single NUMA cell this point.
The host will be reporting NUMA topology, but there should only be a single
NUMA cell this point.
.. code-block:: bash
@ -233,9 +225,7 @@ be a single NUMA cell this point.
| }
+----------------------------------------------------------------------------+
Meanwhile, the guest instance should not have any NUMA configuration
recorded
Meanwhile, the guest instance should not have any NUMA configuration recorded
.. code-block:: bash
@ -246,16 +236,14 @@ recorded
| NULL |
+---------------+
-----------------------------------------------------
Reconfiguring the test instance to have NUMA topology
-----------------------------------------------------
Now that devstack is proved operational, it is time to configure some
NUMA topology for the test VM, so that it can be used to verify the
OpenStack NUMA support. To do the changes, the VM instance that is running
devstack must be shut down.
Now that devstack is proved operational, it is time to configure some NUMA
topology for the test VM, so that it can be used to verify the OpenStack NUMA
support. To do the changes, the VM instance that is running devstack must be
shut down.
.. code-block:: bash
@ -267,14 +255,13 @@ And now back on the physical host edit the guest config as root
# sudo virsh edit f21x86_64
The first thing is to change the <cpu> block to do passthrough of the
host CPU. In particular this exposes the "SVM" or "VMX" feature bits
to the guest so that "Nested KVM" can work. At the same time we want
to define the NUMA topology of the guest. To make things interesting
we're going to give the guest an asymmetric topology with 4 CPUS and
4 GBs of RAM in the first NUMA node and 2 CPUs and 2 GB of RAM in
the second and third NUMA nodes. So modify the guest XML to include
the following CPU XML
The first thing is to change the `<cpu>` block to do passthrough of the host
CPU. In particular this exposes the "SVM" or "VMX" feature bits to the guest so
that "Nested KVM" can work. At the same time we want to define the NUMA
topology of the guest. To make things interesting we're going to give the guest
an asymmetric topology with 4 CPUS and 4 GBs of RAM in the first NUMA node and
2 CPUs and 2 GB of RAM in the second and third NUMA nodes. So modify the guest
XML to include the following CPU XML
.. code-block:: bash
@ -296,11 +283,9 @@ The guest can now be started again, and ssh back into it
# ssh <IP of VM>
Before starting OpenStack services again, it is necessary to
reconfigure Nova to enable the NUMA scheduler filter. The libvirt
virtualization type must also be explicitly set to KVM, so that
guests can take advantage of nested KVM.
Before starting OpenStack services again, it is necessary to reconfigure Nova
to enable the NUMA scheduler filter. The libvirt virtualization type must also
be explicitly set to KVM, so that guests can take advantage of nested KVM.
.. code-block:: bash
@ -316,7 +301,6 @@ Set the following parameters:
[libvirt]
virt_type = kvm
With that done, OpenStack can be started again
.. code-block:: bash
@ -324,9 +308,8 @@ With that done, OpenStack can be started again
# cd $HOME/src/cloud/devstack
# ./rejoin-stack.sh
The first thing is to check that the compute node picked up the
new NUMA topology setup for the guest
The first thing is to check that the compute node picked up the new NUMA
topology setup for the guest
.. code-block:: bash
@ -433,29 +416,26 @@ new NUMA topology setup for the guest
| }
+----------------------------------------------------------------------------+
This indeed shows that there are now 3 NUMA nodes for the "host"
machine, the first with 4 GB of RAM and 4 CPUs, and others with
2 GB of RAM and 2 CPUs each.
This indeed shows that there are now 3 NUMA nodes for the "host" machine, the
first with 4 GB of RAM and 4 CPUs, and others with 2 GB of RAM and 2 CPUs each.
-----------------------------------------------------
Testing instance boot with no NUMA topology requested
-----------------------------------------------------
For the sake of backwards compatibility, if the NUMA filter is
enabled, but the flavor/image does not have any NUMA settings
requested, it should be assumed that the guest will have a
single NUMA node. The guest should be locked to a single host
NUMA node too. Boot a guest with the m1.tiny flavor to test
this condition
For the sake of backwards compatibility, if the NUMA filter is enabled, but the
flavor/image does not have any NUMA settings requested, it should be assumed
that the guest will have a single NUMA node. The guest should be locked to a
single host NUMA node too. Boot a guest with the `m1.tiny` flavor to test this
condition
.. code-block:: bash
# . openrc admin admin
# nova boot --image cirros-0.3.2-x86_64-uec --flavor m1.tiny cirros1
Now look at the libvirt guest XML. It should show that the vCPUs are
locked to pCPUs within a particular node.
Now look at the libvirt guest XML. It should show that the vCPUs are locked to
pCPUs within a particular node.
.. code-block:: bash
@ -466,18 +446,18 @@ locked to pCPUs within a particular node.
<vcpu placement='static' cpuset='6-7'>1</vcpu>
...
This example shows that the guest has been locked to the 3rd NUMA
node (which contains pCPUs 6 and 7). Note that there is no explicit
NUMA topology listed in the guest XML.
This example shows that the guest has been locked to the 3rd NUMA node (which
contains pCPUs 6 and 7). Note that there is no explicit NUMA topology listed in
the guest XML.
------------------------------------------------
Testing instance boot with 1 NUMA cell requested
------------------------------------------------
Moving forward a little, explicitly tell Nova that the NUMA topology
for the guest should have a single NUMA node. This should operate
in an identical manner to the default behavior where no NUMA policy
is set. To define the topology we will create a new flavor
Moving forward a little, explicitly tell Nova that the NUMA topology for the
guest should have a single NUMA node. This should operate in an identical
manner to the default behavior where no NUMA policy is set. To define the
topology we will create a new flavor
.. code-block:: bash
@ -520,19 +500,19 @@ Looking at the resulting guest XML from libvirt
The XML shows:
* Each guest CPU has been pinned to the physical CPUs
associated with a particular NUMA node
* The emulator threads have been pinned to the union
of all physical CPUs in the host NUMA node that
the guest is placed on
* The guest has been given a virtual NUMA topology
with a single node holding all RAM and CPUs
* The guest NUMA node has been strictly pinned to
a host NUMA node.
* Each guest CPU has been pinned to the physical CPUs associated with a
particular NUMA node
As a further sanity test, check what Nova recorded for the
instance in the database. This should match the <numatune>
information
* The emulator threads have been pinned to the union of all physical CPUs in
the host NUMA node that the guest is placed on
* The guest has been given a virtual NUMA topology with a single node holding
all RAM and CPUs
* The guest NUMA node has been strictly pinned to a host NUMA node.
As a further sanity test, check what Nova recorded for the instance in the
database. This should match the <numatune> information
.. code-block:: bash
@ -570,9 +550,8 @@ information
Testing instance boot with 2 NUMA cells requested
-------------------------------------------------
Now getting more advanced we tell Nova that the guest will have two
NUMA nodes. To define the topology we will change the previously
defined flavor
Now getting more advanced we tell Nova that the guest will have two NUMA nodes.
To define the topology we will change the previously defined flavor
.. code-block:: bash
@ -616,19 +595,19 @@ Looking at the resulting guest XML from libvirt
The XML shows:
* Each guest CPU has been pinned to the physical CPUs
associated with particular NUMA nodes
* The emulator threads have been pinned to the union
of all physical CPUs in the host NUMA nodes that
the guest is placed on
* The guest has been given a virtual NUMA topology
with two nodes, each holding half the RAM and CPUs
* The guest NUMA nodes have been strictly pinned to
different host NUMA node.
* Each guest CPU has been pinned to the physical CPUs associated with
particular NUMA nodes
As a further sanity test, check what Nova recorded for the
instance in the database. This should match the <numatune>
information
* The emulator threads have been pinned to the union of all physical CPUs in
the host NUMA nodes that the guest is placed on
* The guest has been given a virtual NUMA topology with two nodes, each holding
half the RAM and CPUs
* The guest NUMA nodes have been strictly pinned to different host NUMA node
As a further sanity test, check what Nova recorded for the instance in the
database. This should match the <numatune> information
.. code-block:: bash