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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.
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f108944ae0
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Osier Yang f108944ae0 doc: Sort out the relationship between <vcpu>, <vcpupin>, and <emulatorpin> 
These 3 elements conflicts with each other in either the doc
or the underlying codes.

Current problems:

Problem 1:

The doc shouldn't simply say "These settings are superseded
by CPU tuning. " for element <vcpu>. As except the tuning, <vcpu>
allows to specify the current, maxmum vcpu number. Apart from that,
<vcpu> also allows to specify the placement as "auto", which binds
the domain process to the advisory nodeset from numad.

Problem 2:

Doc for <vcpu> says its "cpuset" specify the physical CPUs
that the vcpus can be pinned. But it's not the truth, as
actually it only pin domain process to the specified physical
CPUs. So either it's a document bug, or code bug.

Problem 3:

Doc for <vcpupin> says it supersed "cpuset" of <vcpu>, it's
not quite correct, as each <vcpupin> specify the pinning policy
only for one vcpu. How about the ones which doesn't have
<vcpupin> specified? it says the vcpu will be pinned to all
available physical CPUs, but what's the meaning of attribute
"cpuset" of <vcpu> then?

Problem 4:

Doc for <emulatorpin> says it pin the emulator threads (domain
process in other context, perhaps another follow up patch to
cleanup the inconsistency is needed) to the physical CPUs
specified its attribute "cpuset". Which conflicts with
<vcpu>'s "cpuset". And actually in the underlying codes,
it set the affinity for domain process twice if both
"cpuset" for <vcpu> and <emulatorpin> are specified,
and <emulatorpin>'s pinning will override <vcpu>'s.

Problem 5:

When "placement" of <vcpu> is "auto" (I.e. uses numad to
get the advisory nodeset to which the domain process is
pinned to), it will also be overridden by <emulatorpin>,

This patch is trying to sort out the conflicts or bugs by:

1) Don't say <vcpu> is superseded by <cputune>

2) Keep the semanteme for "cpuset" of <vcpu> (I.e. Still says it
   specify the physical CPUs the virtual CPUs). But modifying it
   to mention it also set the pinning policy for domain process,
   and the CPU placement of domain process specified by "cpuset"
   of <vcpu> will be ingored if <emulatorpin> specified, and
   similary, the CPU placement of vcpu thread will be ignored
   if it has <vcpupin> specified, for vcpu which doesn't have
   <vcpupin> specified, it inherits "cpuset" of <vcpu>.

3) Don't say <vcpu> is supersed by <vcpupin>. If neither <vcpupin>
   nor "cpuset" of <vcpu> is specified, the vcpu will be pinned
   to all available pCPUs.

4) If neither <emulatorpin> nor "cpuset" of <vcpu> is specified,
   the domain process (emulator threads in the context) will be
   pinned to all available pCPUs.

5) If "placement" of <vcpu> is "auto", <emulatorpin> is not allowed.

6) hotplugged vcpus will also inherit "cpuset" of <vcpu>

Codes changes according to above document changes:

1) Inherit def->cpumask for each vcpu which doesn't have <vcpupin>
   specified, during parsing.

2) ping the vcpu which doesn't have <vcpupin> specified to def->cpumask
   either by cgroup for sched_setaffinity(2), which is actually done
   by 1).

3) Error out if "placement" == "auto", and <emulatorpin> is specified.
   Otherwise, <emulatorpin> is honored, and "cpuset" of <cpuset> is
   ignored.

4) Setup cgroup for each hotplugged vcpu, and setup the pinning policy
   by either cgroup or sched_setaffinity(2).

5) Remove cgroup and <vcpupin> for each hot unplugged vcpu.

Patches are following (6 in total except this patch)
2012-10-15 12:13:34 +08:00
.gnulib@2a9edc6f2b build: update gnulib for FreeBSD build 2012-10-03 11:50:02 -06:00
build-aux maint: fix up copyright notice inconsistencies 2012-09-20 16:30:55 -06:00
daemon Tweak comments in the policykit rules file 2012-10-14 15:21:18 -04:00
docs doc: Sort out the relationship between <vcpu>, <vcpupin>, and <emulatorpin> 2012-10-15 12:13:34 +08:00
examples Various typos and misspellings 2012-10-12 00:03:43 +02:00
gnulib build: fix fresh checkout on RHEL5 2012-04-19 17:11:43 -06:00
include Various typos and misspellings 2012-10-12 00:03:43 +02:00
m4 build: avoid -Wno-format on new-enough gcc 2012-10-02 09:48:23 -06:00
po locking: Implement lock failure action in sanlock driver 2012-10-11 14:41:42 +02:00
python Properly parse (unsigned) long long 2012-10-13 02:54:11 +02:00
src selinux: Use raw contexts 2012-10-12 17:54:09 +02:00
tests selinux: Use raw contexts 2012-10-12 17:54:09 +02:00
tools virsh: remove reference to migration in blockcopy 2012-10-11 21:12:45 -06:00
.dir-locals.el build: avoid tabs that failed syntax-check 2012-09-06 09:43:46 -06:00
.gitignore Only keep one polkit rules file 2012-10-14 15:21:18 -04:00
.gitmodules make .gnulib a submodule 2009-07-08 16:17:51 +02:00
.mailmap network: fix dnsmasq/radvd binding to IPv6 on recent kernels 2012-09-27 11:17:52 -06:00
AUTHORS Fix typo in HAVE_DBUS automake conditional 2012-10-08 10:33:48 -06:00
autobuild.sh Switch automated builds to use Mingw64 toolchain instead of Mingw32 2012-06-25 10:41:10 +01:00
autogen.sh build: avoid infinite autogen loop 2012-10-01 09:47:38 -06:00
bootstrap maint: regenerate bootstrap 2012-07-27 09:34:04 -06:00
bootstrap.conf maint: fix up copyright notice inconsistencies 2012-09-20 16:30:55 -06:00
cfg.mk build: avoid infinite autogen loop 2012-10-01 09:47:38 -06:00
ChangeLog-old virterror.c: Fix several spelling mistakes 2012-02-03 11:32:51 -07:00
configure.ac selinux: Use raw contexts 2012-10-12 17:54:09 +02:00
COPYING.LIB remove all trailing blank lines 2009-07-16 15:06:42 +02:00
HACKING Various typos and misspellings 2012-10-12 00:03:43 +02:00
libvirt.pc.in build: silence warning from autoconf 2012-05-30 09:22:02 -06:00
libvirt.spec.in spec: Add support for libssh2 transport 2012-10-12 23:36:11 +02:00
Makefile.am Add a ./run script for running programs from the local directory. 2012-09-18 10:59:16 +01:00
Makefile.nonreentrant Ban use of all inet_* functions 2010-10-22 11:59:23 +01:00
mingw-libvirt.spec.in parallels: add driver skeleton 2012-08-01 11:44:26 +08:00
README Correct typos in the documentation (Atsushi SAKAI) 2008-01-24 10:15:13 +00:00
README-hacking maint: relax git minimum version 2010-02-24 14:29:27 -05:00
run.in syntax-check: fix run.in 2012-09-18 13:59:53 +02:00
TODO Update todo list file to point at bugzilla/website 2010-10-13 16:45:26 +01:00

README 

         LibVirt : simple API for virtualization

  Libvirt is a C toolkit to interact with the virtualization capabilities
of recent versions of Linux (and other OSes). It is free software
available under the GNU Lesser General Public License. Virtualization of
the Linux Operating System means the ability to run multiple instances of
Operating Systems concurrently on a single hardware system where the basic
resources are driven by a Linux instance. The library aim at providing
long term stable C API initially for the Xen paravirtualization but
should be able to integrate other virtualization mechanisms if needed.

Daniel Veillard <veillard@redhat.com>