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By default, pfifo_fast queueing discipline (qdisc) is set on newly created interfaces (including TAPs). This qdisc has three queues and packets that want to be sent through given NIC are placed into one of the queues based on TOS field. Queues are then emptied based on their priority allowing interactive sessions stay interactive whilst something else is downloading a large file. Obviously, this means that kernel has to be involved and some locking has to happen (when placing packets into queues). If virtualization is taken into account then the above algorithm happens twice - once in the guest and the second time in the host. This is arguably not optimal as it burns host CPU cycles needlessly. Guest already made it choice and sent packets in the order it wants. To resolve this, Linux kernel offers 'noqueue' qdisc which can be applied on virtual interfaces and in fact for 'lo' it is by default: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue Set it for other TAP devices we create for domains too. With this change I was able to squeeze 1Mbps more from a macvtap attached to a guest and to my 1Gbps LAN (as measured by iperf3). Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1329644 Signed-off-by: Michal Privoznik <mprivozn@redhat.com> Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
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:
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: