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Daniel P. Berrangé 829142699e remote: make ssh-helper massively faster
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>
2020-11-26 10:14:18 +00:00
.ctags.d maint: Add support for .ctags.d 2019-05-31 17:54:28 +02:00
.github github: skip lockdown of old issues/prs 2020-04-07 17:50:54 +01:00
build-aux syntax-check: Don't forbid curly braces around single line condition body 2020-09-15 15:20:23 +02:00
ci gitlab-ci: add coverity job 2020-11-19 14:38:13 +01:00
docs docs: Document SELinux caveats when migrating over UNIX sockets 2020-11-25 00:10:52 +01:00
examples libvirt: support memory failure event 2020-10-23 09:41:52 +02:00
include virDomainAuthorizedSSHKeysSet: Use uint for @nkeys 2020-11-23 13:35:16 +01:00
po po: Refresh potfile for v6.10.0 2020-11-25 08:47:39 +01:00
scripts docs: xsl: Unify stylability of main container element 2020-11-16 14:04:04 +01:00
src remote: make ssh-helper massively faster 2020-11-26 10:14:18 +00:00
tests util: call iptables directly rather than via firewalld 2020-11-24 14:22:06 -05:00
tools virsh: Added attach-disk support for network disk 2020-11-23 14:44:39 +01:00
.color_coded.in gnulib: delete all gnulib integration 2020-02-07 15:03:54 +00:00
.ctags ctags: Generate tags for headers, i.e. function prototypes 2018-09-18 14:21:33 +02:00
.dir-locals.el build: avoid tabs that failed syntax-check 2012-09-06 09:43:46 -06:00
.editorconfig Add .editorconfig 2019-09-06 12:47:46 +02:00
.gitignore Ignore clangd-related files and folders 2020-08-03 10:57:47 +02:00
.gitlab-ci.yml gitlab-ci: add coverity job 2020-11-19 14:38:13 +01:00
.gitmodules gnulib: delete all gnulib integration 2020-02-07 15:03:54 +00:00
.gitpublish gitpublish: add a subject prefix 2020-01-16 13:04:11 +00:00
.mailmap mailmap: consolidate my email addresses 2020-10-06 12:05:09 +02:00
.ycm_extra_conf.py.in gnulib: delete all gnulib integration 2020-02-07 15:03:54 +00:00
AUTHORS.rst.in AUTHORS: Remove Emacs file variables 2020-09-02 13:20:17 +02:00
config.h Fix capitalization "CLang" -> "Clang" 2020-11-12 15:01:42 +01:00
configmake.h.in meson: generate configmake.h 2020-08-03 09:26:48 +02:00
CONTRIBUTING.rst meson: adjust our documentation to mention meson instead of autoconf 2020-08-03 09:27:09 +02:00
COPYING maint: follow recommended practice for using LGPL 2013-05-20 14:15:21 -06:00
COPYING.LESSER maint: Remove control characters from LGPL license file 2015-09-25 09:16:24 +02:00
gitdm.config gitdm: add 'ibm' file 2019-10-18 17:32:52 +02:00
libvirt-admin.pc.in Add libvirt-admin library 2015-06-16 13:46:20 +02:00
libvirt-lxc.pc.in Add pkg-config files for libvirt-qemu & libvirt-lxc 2014-06-23 16:17:27 +01:00
libvirt-qemu.pc.in Add pkg-config files for libvirt-qemu & libvirt-lxc 2014-06-23 16:17:27 +01:00
libvirt.pc.in Add pkg-config files for libvirt-qemu & libvirt-lxc 2014-06-23 16:17:27 +01:00
libvirt.spec.in spec: Drop UUID handling for default network 2020-11-20 11:44:07 +01:00
meson_options.txt meson: add tests build option to enable/disable unit tests 2020-10-09 13:44:54 +02:00
meson.build src: rework static analysis detection 2020-11-19 14:38:13 +01:00
mingw-libvirt.spec.in spec: Install all schemas 2020-10-08 09:58:44 +02:00
NEWS.rst NEWS: restore backtick balance 2020-11-18 16:47:57 +01:00
README.rst README: drop Travis CI badge 2020-08-03 15:08:28 +02:00
run.in Prefer https: everywhere where possible 2020-09-01 21:58:46 +02:00

.. image:: https://gitlab.com/libvirt/libvirt/badges/master/pipeline.svg
     :target: https://gitlab.com/libvirt/libvirt/pipelines
     :alt: GitLab CI Build Status
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     :alt: Translation status

==============================
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