qemu: Support numad

numad is an user-level daemon that monitors NUMA topology and
processes resource consumption to facilitate good NUMA resource
alignment of applications/virtual machines to improve performance
and minimize cost of remote memory latencies. It provides a
pre-placement advisory interface, so significant processes can
be pre-bound to nodes with sufficient available resources.

More details: http://fedoraproject.org/wiki/Features/numad

"numad -w ncpus:memory_amount" is the advisory interface numad
provides currently.

This patch add the support by introducing a new XML attribute
for <vcpu>. e.g.

  <vcpu placement="auto">4</vcpu>
  <vcpu placement="static" cpuset="1-10^6">4</vcpu>

The returned advisory nodeset from numad will be printed
in domain's dumped XML. e.g.
  <vcpu placement="auto" cpuset="1-10^6">4</vcpu>

If placement is "auto", the number of vcpus and the current
memory amount specified in domain XML will be used for numad
command line (numad uses MB for memory amount):
  numad -w $num_of_vcpus:$current_memory_amount / 1024

The advisory nodeset returned from numad will be used to set
domain process CPU affinity then. (e.g. qemuProcessInitCpuAffinity).

If the user specifies both CPU affinity policy (e.g.
(<vcpu cpuset="1-10,^7,^8">4</vcpu>) and placement == "auto"
the specified CPU affinity will be overridden.

Only QEMU/KVM drivers support it now.

See docs update in patch for more details.

1 files changed, 14 insertions, 3 deletions

diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
index bf0675e65..624c6b2cd 100644
--- a/docs/formatdomain.html.in
+++ b/docs/formatdomain.html.in
@@ -318,7 +318,7 @@
 <pre>
 &lt;domain&gt;
   ...
-  &lt;vcpu cpuset="1-4,^3,6" current="1"&gt;2&lt;/vcpu&gt;
+  &lt;vcpu placement='static' cpuset="1-4,^3,6" current="1"&gt;2&lt;/vcpu&gt;
   ...
 &lt;/domain&gt;
 </pre>
@@ -336,7 +336,18 @@
         be excluded from a previous range.  <span class="since">Since
         0.8.5</span>, the optional attribute <code>current</code> can
         be used to specify whether fewer than the maximum number of
-        virtual CPUs should be enabled.
+        virtual CPUs should be enabled.  <span class="since">Since
+        0.9.11 (QEMU and KVM only), the optional attribute
+        <code>placement</code> can be used to indicate the CPU placement
+        mode for domain process, its value can be either "static" or
+        "auto", defaults to "static" if <code>cpuset</code> is specified,
+        "auto" indicates the domain process will be pinned to the advisory
+        nodeset from querying numad, and the value of attribute
+        <code>cpuset</code> will be overridden by the advisory nodeset
+        from numad if it's specified. If both <code>cpuset</code> and
+        <code>placement</code> are not specified, or if <code>placement</code>
+        is "static", but no <code>cpuset</code> is specified, the domain
+        process will be pinned to all the available physical CPUs.
       </dd>
     </dl>
 
@@ -544,7 +555,7 @@
         <span class='since'>Since 0.9.3</span>
       <dt><code>memory</code></dt>
       <dd>
-        The optional <code>memory</code> element specify how to allocate memory
+        The optional <code>memory</code> element specifies how to allocate memory
         for the domain process on a NUMA host. It contains two attributes,
         attribute <code>mode</code> is either 'interleave', 'strict',
         or 'preferred',