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[Qemu-devel] [PATCH v3 6/6] numa: deprecate implict memory distribution

From: Igor Mammedov
Subject: [Qemu-devel] [PATCH v3 6/6] numa: deprecate implict memory distribution between nodes
Date: Fri, 17 May 2019 09:45:19 +0200

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 of initial RAM.
   - update deprecation doc, s/4.0/4.1/
   - mention that legacy 'mem' option could also be used to
     provide explicit memory distribution for old machine types

Signed-off-by: Igor Mammedov <address@hidden>
 numa.c               | 3 +++
 qemu-deprecated.texi | 8 ++++++++
 2 files changed, 11 insertions(+)

diff --git a/numa.c b/numa.c
index 2205773..6d45a1f 100644
--- a/numa.c
+++ b/numa.c
@@ -409,6 +409,9 @@ void numa_complete_configuration(MachineState *ms)
         if (i == nb_numa_nodes) {
             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 995a96c..546f722 100644
--- a/qemu-deprecated.texi
+++ b/qemu-deprecated.texi
@@ -88,6 +88,14 @@ In future new machine versions will not accept the option 
but it will keep
 working with old machine types. User can inspect read-only machine property
 'numa-mem-supported' to check if specific machine type (not) supports the 
address@hidden -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)

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