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Daniel P. Berrangé
829142699e
It was reported that the performance of tunnelled migration and volume upload/download regressed in 6.9.0, when the virt-ssh-helper is used for remote SSH tunnelling instead of netcat. When seeing data available to read from stdin, or the socket, the current code will allocate at most 1k of extra space in the buffer it has. After writing data to the socket, or stdout, if more than 1k of extra space is in the buffer, it will reallocate to free up that space. This results in a huge number of mallocs when doing I/O, as well as a huge number of syscalls since at most 1k of data will be read/written at a time. Also if writing blocks for some reason, it will continue to read data with no memory bound which is bad. This changes the code to use a 1 MB fixed size buffer in each direction. If that buffer becomes full, it will update the watches to stop reading more data. It will never reallocate the buffer at runtime. This increases the performance by orders of magnitude. Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com> Tested-by: Christian Ehrhardt <christian.ehrhardt@canonical.com> Signed-off-by: Daniel P. Berrangé <berrange@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