Re: [libvirt] [PATCH v6 1/4] numa: describe siblings distances within cells

From: Wim ten Have <wim.ten.have(a)oracle.com&gt; Add support for describing NUMA distances in a domain's <numa> <cell> XML description. Below is an example of a 4 node setup: <cpu> <numa> <cell id='0' cpus='0-3' memory='2097152' unit='KiB'> <distances> <sibling id='0' value='10'/> <sibling id='1' value='21'/> <sibling id='2' value='31'/> <sibling id='3' value='21'/> </distances> </cell> <cell id='1' cpus='4-7' memory='2097152' unit='KiB'> <distances> <sibling id='0' value='21'/> <sibling id='1' value='10'/> <sibling id='2' value='21'/> <sibling id='3' value='31'/> </distances> </cell> <cell id='2' cpus='8-11' memory='2097152' unit='KiB'> <distances> <sibling id='0' value='31'/> <sibling id='1' value='21'/> <sibling id='2' value='10'/> <sibling id='3' value='21'/> </distances> <cell id='3' cpus='12-15' memory='2097152' unit='KiB'> <distances> <sibling id='0' value='21'/> <sibling id='1' value='31'/> <sibling id='2' value='21'/> <sibling id='3' value='10'/> </distances> </cell> </numa> </cpu> A <cell> defines a NUMA node. <distances> describes the NUMA distance from the <cell> to the other NUMA nodes (the <sibling>s). For example, in above XML description, the distance between NUMA node0 <cell id='0' ...> and NUMA node2 <sibling id='2' ...> is 31. Valid distance value are '10 <= value <= 255'. A distance value of 10 represents the distance to the node itself. A distance value of 20 represents the default value for remote nodes but other values are possible depending on the physical topology of the system. When distances are not fully described, any missing sibling distance values will default to 10 for local nodes and 20 for remote nodes. If distance is given for A -> B, then we default B -> A to the same value instead of 20. Signed-off-by: Wim ten Have <wim.ten.have(a)oracle.com&gt; Reviewed-by: Daniel P. Berrange <berrange(a)redhat.com&gt; --- Changes on v1: - Add changes to docs/formatdomain.html.in describing schema update. Changes on v2: - Automatically apply distance symmetry maintaining cell <-> sibling. - Check for maximum '255' on numaDistanceValue. - Automatically complete empty distance ranges. - Check that sibling_id's are in range with cell identifiers. - Allow non-contiguous ranges, starting from any node id. - Respect parameters as ATTRIBUTE_NONNULL fix functions and callers. - Add and apply topology for LOCAL_DISTANCE=10 and REMOTE_DISTANCE=20. Changes on v3: - Add UNREACHABLE if one locality is unreachable from another. - Add code cleanup aligning function naming in a separated patch. - Add numa related driver code in a separated patch. - Remove <choice> from numaDistanceValue schema/basictypes.rng - Correct doc changes. Changes on v4: - Fix symmetry error under virDomainNumaDefNodeDistanceParseXML() Changes on v5: - Apply doc suggestions. - Apply virReportError() message suggestions. - Remove redundant sanity checks from virDomainNumaDefNodeDistanceParseXML(). --- docs/formatdomain.html.in | 63 ++++++++++++++- docs/schemas/basictypes.rng | 7 ++ docs/schemas/cputypes.rng | 18 +++++ src/conf/numa_conf.c | 191 +++++++++++++++++++++++++++++++++++++++++++- 4 files changed, 275 insertions(+), 4 deletions(-) diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in index 4f28dce35..df2f17f5d 100644 --- a/docs/formatdomain.html.in +++ b/docs/formatdomain.html.in @@ -1529,7 +1529,68 @@ </p> <p> - This guest NUMA specification is currently available only for QEMU/KVM. + This guest NUMA specification is currently available only for + QEMU/KVM and Xen. Whereas Xen driver also allows for a distinct + description of NUMA arranged <code>sibling</code> <code>cell</code> + <code>distances</code> <span class="since">Since 3.9.0</span>. + </p> + + <p> + Under NUMA hardware architecture, distinct resources such as memory + create a designated distance between <code>cell</code> and + <code>siblings</code> that now can be described with the help of + <code>distances</code>. A detailed description can be found within + the ACPI (Advanced Configuration and Power Interface Specification) + within the chapter explaining the system's SLIT (System Locality + Distance Information Table). + </p>