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[Qemu-devel] [PULL 18/29] numa: deprecate implict memory distribution between nodes

Eduardo Habkost posted 29 patches 6 years, 3 months ago

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[Qemu-devel] [PULL 18/29] numa: deprecate implict memory distribution between nodes

Posted by Eduardo Habkost 6 years, 3 months ago

From: Igor Mammedov <imammedo@redhat.com>

Implicit RAM distribution between nodes has exactly the same issues as:
  "numa: deprecate 'mem' parameter of '-numa node' option"
only with QEMU being the user that's 'adding' 'mem' parameter.

Deprecate it, to get it out of the way so that we could consolidate
guest RAM allocation using memory backends making it consistent and
possibly later on transition to using memory devices instead of
adhoc memory mapping for the initial RAM.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <1559205199-233510-4-git-send-email-imammedo@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
---
 numa.c               | 3 +++
 qemu-deprecated.texi | 8 ++++++++
 2 files changed, 11 insertions(+)

diff --git a/numa.c b/numa.c
index 7d449c7e95..c1f5e84fa5 100644
--- a/numa.c
+++ b/numa.c
@@ -410,6 +410,9 @@ void numa_complete_configuration(MachineState *ms)
         if (i == nb_numa_nodes) {
             assert(mc->numa_auto_assign_ram);
             mc->numa_auto_assign_ram(mc, numa_info, nb_numa_nodes, ram_size);
+            warn_report("Default splitting of RAM between nodes is deprecated,"
+                        " Use '-numa node,memdev' to explictly define RAM"
+                        " allocation per node");
         }
 
         numa_total = 0;
diff --git a/qemu-deprecated.texi b/qemu-deprecated.texi
index 44c9a95966..2fe9b72121 100644
--- a/qemu-deprecated.texi
+++ b/qemu-deprecated.texi
@@ -104,6 +104,14 @@ In future new machine versions will not accept the option but it will still
 work with old machine types. User can check QAPI schema to see if the legacy
 option is supported by looking at MachineInfo::numa-mem-supported property.
 
+@subsection -numa node (without memory specified) (since 4.1)
+
+Splitting RAM by default between NUMA nodes has the same issues as @option{mem}
+parameter described above with the difference that the role of the user plays
+QEMU using implicit generic or board specific splitting rule.
+Use @option{memdev} with @var{memory-backend-ram} backend or @option{mem} (if
+it's supported by used machine type) to define mapping explictly instead.
+
 @section QEMU Machine Protocol (QMP) commands
 
 @subsection block-dirty-bitmap-add "autoload" parameter (since 2.12.0)
-- 
2.18.0.rc1.1.g3f1ff2140