8aaed287f5
For managed save we can choose between various compression
methods. I randomly tested the 'xz' program on a 8 GB guest
and was surprised to have to wait > 50 minutes for it to
finish compressing, with 'xz' burning 100% cpu for the
entire time. Despite the impressive compression, this is
completely useless in the real world as it is far too long
to wait to save the VM.
The 'xz' binary defaults to '-6' optimization level which
aims for high compression, with moderate memory usage,
at the expense of speed.
This change switches it to use the '-3' optimization level
which is documented as being the one that optimizes speed
at expense of compression. Even with this, it will still
outperform all the other options in terms of compression
level. It is a little less than x4 faster than '-6' which
means it starts to be a viable choice to use 'xz' for
people who really want best compression.
The test results on a 1 GB, fairly freshly booted VM are
as follows
format | save | restore size
=======+=======+=============
raw | 05s | 1s | 428 MB
lzop | 05s | 3s | 160 MB
gzip | 29s | 5s | 118 MB
bz2 | 54s | 22s | 114 MB
xz | 4m37s | 13s | 86 MB
xz -3 | 1m20s | 12s | 95 MB
Based on this we can say
* For moderate compression with no noticable loss in speed
=> use lzop
* For high compression with moderate loss in speed
=> use gzip
* For best compression with significant loss in speed
=> use xz
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.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
Libvirt uses the GNU Autotools build system, so in general can be built and installed with the usual commands, however, we mandate to have the build directory different than the source directory. For example, to build in a manner that is suitable for installing as root, use:
$ mkdir build && cd build
$ ../configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var
$ make
$ sudo make install
While to build & install as an unprivileged user
$ mkdir build && cd build
$ ../configure --prefix=$HOME/usr
$ make
$ make install
The libvirt code relies on a large number of 3rd party libraries. These will
be detected during execution of the configure script and a summary printed
which lists any missing (optional) dependencies.
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: