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06f405c627
Let's imagine a guest that's configured with strict numatune:
<numatune>
<memory mode='strict' nodeset='0'/>
</numatune>
For guests with NUMA:
Depending on machine type used (see commit v6.4.0-rc1~75) we
generate either:
1) -object '{"qom-type":"memory-backend-ram","id":"ram-node0",\
"size":20971520,"host-nodes":[0],"policy":"preferred"}' \
-numa node,nodeid=0,cpus=0,memdev=ram-node0
or
2) -numa node,nodeid=0,cpus=0,mem=20480
Later, when QEMU boots up and cpuset CGroup controller is
available we further restrict QEMU there too. But there's a
behaviour difference hidden: while in case 1) QEMU is restricted
from beginning, in case 2) it is not and thus it may happen that
it will allocate memory from different NUMA node and even though
CGroup will try to migrate it, it may fail to do so (e.g. because
memory is locked). Therefore, one can argue that case 2) is
broken. NB, case 2) is exactly what mode 'restrictive' is for.
However, in case 1) we are unable to update QEMU with new
host-nodes, simply because it's lacking a command to do so.
For guests without NUMA:
It's very close to case 2) from above. We have commit
v7.10.0-rc1~163 that prevents us from outputting host-nodes when
generating memory-backend-* for system memory, but that simply
allows QEMU to allocate memory anywhere and then relies on
CGroups to move it to desired location.
Due to all of this, there is no reliable way to change nodeset
for mode 'strict'. Let's forbid it.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Pavel Hrdina <phrdina@redhat.com>
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==============================
Libvirt API for virtualization
==============================
Libvirt provides a portable, long term stable C API for managing the
virtualization technologies provided by many operating systems. It
includes support for QEMU, KVM, Xen, LXC, bhyve, Virtuozzo, VMware
vCenter and ESX, VMware Desktop, Hyper-V, VirtualBox and the POWER
Hypervisor.
For some of these hypervisors, it provides a stateful management
daemon which runs on the virtualization host allowing access to the
API both by non-privileged local users and remote users.
Layered packages provide bindings of the libvirt C API into other
languages including Python, Perl, PHP, Go, Java, OCaml, as well as
mappings into object systems such as GObject, CIM and SNMP.
Further information about the libvirt project can be found on the
website:
https://libvirt.org
License
=======
The libvirt C API is distributed under the terms of GNU Lesser General
Public License, version 2.1 (or later). Some parts of the code that are
not part of the C library may have the more restrictive GNU General
Public License, version 2.0 (or later). See the files ``COPYING.LESSER``
and ``COPYING`` for full license terms & conditions.
Installation
============
Instructions on building and installing libvirt can be found on the website:
https://libvirt.org/compiling.html
Contributing
============
The libvirt project welcomes contributions in many ways. For most components
the best way to contribute is to send patches to the primary development
mailing list. Further guidance on this can be found on the website:
https://libvirt.org/contribute.html
Contact
=======
The libvirt project has two primary mailing lists:
* libvirt-users@redhat.com (**for user discussions**)
* libvir-list@redhat.com (**for development only**)
Further details on contacting the project are available on the website:
https://libvirt.org/contact.html