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https://bugzilla.redhat.com/show_bug.cgi?id=1198645 Once upon a time, there was a little domain. And the domain was pinned onto a NUMA node and hasn't fully allocated its memory: <memory unit='KiB'>2355200</memory> <currentMemory unit='KiB'>1048576</currentMemory> <numatune> <memory mode='strict' nodeset='0'/> </numatune> Oh little me, said the domain, what will I do with so little memory. If I only had a few megabytes more. But the old admin noticed the whimpering, barely audible to untrained human ear. And good admin he was, he gave the domain yet more memory. But the old NUMA topology witch forbade to allocate more memory on the node zero. So he decided to allocate it on a different node: virsh # numatune little_domain --nodeset 0-1 virsh # setmem little_domain 2355200 The little domain was happy. For a while. Until bad, sharp teeth shaped creature came. Every process in the system was afraid of him. The OOM Killer they called him. Oh no, he's after the little domain. There's no escape. Do you kids know why? Because when the little domain was born, her father, Libvirt, called numa_set_membind(). So even if the admin allowed her to allocate memory from other nodes in the cgroups, the membind() forbid it. So what's the lesson? Libvirt should rely on cgroups, whenever possible and use numa_set_membind() as the last ditch effort. Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
libvirt library code README
===========================
The directory provides the bulk of the libvirt codebase. Everything
except for the libvirtd daemon and client tools. The build uses a
large number of libtool convenience libraries - one for each child
directory, and then links them together for the final libvirt.so,
although some bits get linked directly to libvirtd daemon instead.
The files directly in this directory are supporting the public API
entry points & data structures.
There are two core shared modules to be aware of:
* util/ - a collection of shared APIs that can be used by any
code. This directory is always in the include path
for all things built
* conf/ - APIs for parsing / manipulating all the official XML
files used by the public API. This directory is only
in the include path for driver implementation modules
* vmx/ - VMware VMX config handling (used by esx/ and vmware/)
Then there are the hypervisor implementations:
* bhyve - bhyve - The BSD Hypervisor
* esx/ - VMware ESX and GSX support using vSphere API over SOAP
* hyperv/ - Microsoft Hyper-V support using WinRM
* lxc/ - Linux Native Containers
* openvz/ - OpenVZ containers using cli tools
* phyp/ - IBM Power Hypervisor using CLI tools over SSH
* qemu/ - QEMU / KVM using qemu CLI/monitor
* remote/ - Generic libvirt native RPC client
* test/ - A "mock" driver for testing
* uml/ - User Mode Linux
* vbox/ - Virtual Box using native API
* vmware/ - VMware Workstation and Player using the vmrun tool
* xen/ - Xen using hypercalls, XenD SEXPR & XenStore
* xenapi/ - Xen using libxenserver
Finally some secondary drivers that are shared for several HVs.
Currently these are used by LXC, OpenVZ, QEMU, UML and Xen drivers.
The ESX, Hyper-V, Power Hypervisor, Remote, Test & VirtualBox drivers all
implement the secondary drivers directly
* cpu/ - CPU feature management
* interface/ - Host network interface management
* network/ - Virtual NAT networking
* nwfilter/ - Network traffic filtering rules
* node_device/ - Host device enumeration
* secret/ - Secret management
* security/ - Mandatory access control drivers
* storage/ - Storage management drivers
Since both the hypervisor and secondary drivers can be built as
dlopen()able modules, it is *FORBIDDEN* to have build dependencies
between these directories. Drivers are only allowed to depend on
the public API, and the internal APIs in the util/ and conf/
directories