docs/mm: Physical Memory: add example of interleaving nodes

Add an example of memory layout with interleaving nodes where even memory banks belong to node 0 and odd memory banks belong to node 1 Suggested-by: Michal Hocko <[email protected]> Signed-off-by: Mike Rapoport (IBM) <[email protected]> Reviewed-by: David Hildenbrand <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Jonathan Corbet <[email protected]>
sirdarckcat · Mar 14, 2023 · 10d1813 · 10d1813
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commit 10d1813
Showing 1 changed file with 19 additions and 0 deletions.
diff --git a/Documentation/mm/physical_memory.rst b/Documentation/mm/physical_memory.rst
@@ -114,6 +114,25 @@ RAM equally split between two nodes, there will be ``ZONE_DMA32``,
   |  DMA32  |  NORMAL  |  MOVABLE  | |   NORMAL   |   MOVABLE   |
   +---------+----------+-----------+ +------------+-------------+
 
+
+Memory banks may belong to interleaving nodes. In the example below an x86
+machine has 16 Gbytes of RAM in 4 memory banks, even banks belong to node 0
+and odd banks belong to node 1::
+
+
+  0              4G              8G             12G            16G
+  +-------------+ +-------------+ +-------------+ +-------------+
+  |    node 0   | |    node 1   | |    node 0   | |    node 1   |
+  +-------------+ +-------------+ +-------------+ +-------------+
+
+  0   16M      4G
+  +-----+-------+ +-------------+ +-------------+ +-------------+
+  | DMA | DMA32 | |    NORMAL   | |    NORMAL   | |    NORMAL   |
+  +-----+-------+ +-------------+ +-------------+ +-------------+
+
+In this case node 0 will span from 0 to 12 Gbytes and node 1 will span from
+4 to 16 Gbytes.
+
 .. _nodes:
 
 Nodes