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Right now, when a VCPU wakes-up, we check whether it should preempt what is running on the PCPU, and whether or not the waking VCPU can be migrated (by tickling some idlers). However, this can result in suboptimal or even wrong behaviour, as explained here: http://lists.xen.org/archives/html/xen-devel/2012-10/msg01732.html This change, instead, when deciding which PCPU(s) to tickle, upon VCPU wake-up, considers both what it is likely to happen on the PCPU where the wakeup occurs,and whether or not there are idlers where the woken-up VCPU can run. In fact, if there are, we can avoid interrupting the running VCPU. Only in case there aren't any of these PCPUs, preemption and migration are the way to go. This has been tested (on top of the previous change) by running the following benchmarks inside 2, 6 and 10 VMs, concurrently, on a shared host, each with 2 VCPUs and 960 MB of memory (host had 16 ways and 12 GB RAM). 1) All VMs had 'cpus="all"' in their config file. $ sysbench --test=cpu ... (time, lower is better) | VMs | w/o this change | w/ this change | | 2 | 50.078467 +/- 1.6676162 | 49.673667 +/- 0.0094321 | | 6 | 63.259472 +/- 0.1137586 | 61.680011 +/- 1.0208723 | | 10 | 91.246797 +/- 0.1154008 | 90.396720 +/- 1.5900423 | $ sysbench --test=memory ... (throughput, higher is better) | VMs | w/o this change | w/ this change | | 2 | 485.56333 +/- 6.0527356 | 487.83167 +/- 0.7602850 | | 6 | 401.36278 +/- 1.9745916 | 409.96778 +/- 3.6761092 | | 10 | 294.43933 +/- 0.8064945 | 302.49033 +/- 0.2343978 | $ specjbb2005 ... (throughput, higher is better) | VMs | w/o this change | w/ this change | | 2 | 43150.63 +/- 1359.5616 | 43275.427 +/- 606.28185 | | 6 | 29274.29 +/- 1024.4042 | 29716.189 +/- 1290.1878 | | 10 | 19061.28 +/- 512.88561 | 19192.599 +/- 605.66058 | 2) All VMs had their VCPUs statically pinned to the host's PCPUs. $ sysbench --test=cpu ... (time, lower is better) | VMs | w/o this change | w/ this change | | 2 | 47.8211 +/- 0.0215504 | 47.826900 +/- 0.0077872 | | 6 | 62.689122 +/- 0.0877173 | 62.764539 +/- 0.3882493 | | 10 | 90.321097 +/- 1.4803867 | 89.974570 +/- 1.1437566 | $ sysbench --test=memory ... (throughput, higher is better) | VMs | w/o this change | w/ this change | | 2 | 550.97667 +/- 2.3512355 | 550.87000 +/- 0.8140792 | | 6 | 443.15000 +/- 5.7471797 | 454.01056 +/- 8.4373466 | | 10 | 313.89233 +/- 1.3237493 | 321.81167 +/- 0.3528418 | $ specjbb2005 ... (throughput, higher is better) | 2 | 49591.057 +/- 952.93384 | 49594.195 +/- 799.57976 | | 6 | 33538.247 +/- 1089.2115 | 33671.758 +/- 1077.6806 | | 10 | 21927.870 +/- 831.88742 | 21891.131 +/- 563.37929 | Numbers show how the change has either no or very limited impact (specjbb2005 case) or, when it does have some impact, that is a real improvement in performances (sysbench-memory case). Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com> Acked-by: George Dunlap <george.dunlap@citrix.com> Committed-by: Keir Fraser <keir@xen.org>
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http://www.xen.org/
What is Xen?
============
Xen is a Virtual Machine Monitor (VMM) originally developed by the
Systems Research Group of the University of Cambridge Computer
Laboratory, as part of the UK-EPSRC funded XenoServers project. Xen
is freely-distributable Open Source software, released under the GNU
GPL. Since its initial public release, Xen has grown a large
development community, spearheaded by xen.org (http://www.xen.org).
The 4.2 release offers excellent performance, hardware support and
enterprise-grade features such as x86_32-PAE, x86_64, SMP guests and
live relocation of VMs. Ports to Linux, NetBSD, FreeBSD and Solaris
are available from the community.
This file contains some quick-start instructions to install Xen on
your system. For more information see http:/www.xen.org/ and
http://wiki.xen.org/
Quick-Start Guide
=================
First, there are a number of prerequisites for building a Xen source
release. Make sure you have all the following installed, either by
visiting the project webpage or installing a pre-built package
provided by your OS distributor:
* GCC v4.1 or later
* GNU Make
* GNU Binutils
* Development install of zlib (e.g., zlib-dev)
* Development install of Python v2.3 or later (e.g., python-dev)
* Development install of curses (e.g., libncurses-dev)
* Development install of openssl (e.g., openssl-dev)
* Development install of x11 (e.g. xorg-x11-dev)
* Development install of uuid (e.g. uuid-dev)
* Development install of yajl (e.g. libyajl-dev)
* Development install of libaio (e.g. libaio-dev) version 0.3.107 or
greater. Set CONFIG_SYSTEM_LIBAIO in .config if this is not available.
* Development install of GLib v2.0 (e.g. libglib2.0-dev)
* Development install of Pixman (e.g. libpixman-1-dev)
* pkg-config
* bridge-utils package (/sbin/brctl)
* iproute package (/sbin/ip)
* udev
* GNU bison and GNU flex
* GNU gettext
* 16-bit x86 assembler, loader and compiler (dev86 rpm or bin86 & bcc debs)
* ACPI ASL compiler (iasl)
* markdown
In addition to the above there are a number of optional build
prerequisites. Omitting these will cause the related features to be
disabled at compile time:
* Development install of Ocaml (e.g. ocaml-nox and
ocaml-findlib). Required to build ocaml components which
includes the alternative ocaml xenstored.
Second, you need to acquire a suitable kernel for use in domain 0. If
possible you should use a kernel provided by your OS distributor. If
no suitable kernel is available from your OS distributor then refer to
http://wiki.xen.org/wiki/XenDom0Kernels for suggestions for
suitable kernels to use.
If you are looking to compile a Dom0 kernel from source, please refer to
http://wiki.xen.org/wiki/XenParavirtOps.
[NB. Unless noted otherwise, all the following steps should be
performed with root privileges.]
1. Download and untar the source tarball file. This will be a
file named xen-unstable-src.tgz, or xen-$version-src.tgz.
You can also pull the current version from the mercurial
repository at http://xenbits.xen.org/
# tar xzf xen-unstable-src.tgz
Assuming you are using the unstable tree, this will
untar into xen-unstable. The rest of the instructions
use the unstable tree as an example, substitute the
version for unstable.
2. cd to xen-unstable (or whatever you sensibly rename it to).
3. For the very first build, or if you want to destroy build trees,
perform the following steps:
# ./configure
# make world
# make install
If you want, you can run ./configure --help to see the list of
options available options when building and installing Xen.
This will create and install onto the local machine. It will build
the xen binary (xen.gz), the tools and the documentation.
You can override the destination for make install by setting DESTDIR
to some value.
4. To rebuild an existing tree without modifying the config:
# make dist
This will build and install xen, tools, and docs into the local dist/
directory.
You can override the destination for make install by setting DISTDIR
to some value.
make install and make dist differ in that make install does the
right things for your local machine (installing the appropriate
version of udev scripts, for example), but make dist includes all
versions of those scripts, so that you can copy the dist directory
to another machine and install from that distribution.
Python Runtime Libraries
========================
Xend (the Xen daemon) has the following runtime dependencies:
* Python 2.3 or later.
In some distros, the XML-aspects to the standard library
(xml.dom.minidom etc) are broken out into a separate python-xml package.
This is also required.
In more recent versions of Debian and Ubuntu the XML-aspects are included
in the base python package however (python-xml has been removed
from Debian in squeeze and from Ubuntu in intrepid).
URL: http://www.python.org/
Debian: python
* For optional SSL support, pyOpenSSL:
URL: http://pyopenssl.sourceforge.net/
Debian: python-pyopenssl
* For optional PAM support, PyPAM:
URL: http://www.pangalactic.org/PyPAM/
Debian: python-pam
* For optional XenAPI support in XM, lxml:
URL: http://lxml.de/
Debian: python-lxml
YUM: python-lxml
Intel(R) Trusted Execution Technology Support
=============================================
Intel's technology for safer computing, Intel(R) Trusted Execution Technology
(Intel(R) TXT), defines platform-level enhancements that provide the building
blocks for creating trusted platforms. For more information, see
http://www.intel.com/technology/security/.
Intel(R) TXT support is provided by the Trusted Boot (tboot) module in
conjunction with minimal logic in the Xen hypervisor.
Tboot is an open source, pre- kernel/VMM module that uses Intel(R) TXT to
perform a measured and verified launch of an OS kernel/VMM.
The Trusted Boot module is available from
http://sourceforge.net/projects/tboot. This project hosts the code in a
mercurial repo at http://tboot.sourceforge.net/hg/tboot.hg and contains
tarballs of the source. Instructions in the tboot README describe how
to modify grub.conf to use tboot to launch Xen.
There are optional targets as part of Xen's top-level makefile that will
download and build tboot: install-tboot, build-tboot, dist-tboot, clean-tboot.
These will download the latest tar file from the SourceForge site using wget,
then build/install/dist according to Xen's settings.
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