[PATCH v2] docs/mm: Physical Memory: add example of interleaving nodes

[Mike Rapoport <rppt@kernel.org>]

From: "Mike Rapoport (IBM)" <rppt@kernel.org>

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 <mhocko@kernel.org>
Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org>
---

v2:
* Wording update (Bagas)
* Add forgotten Suggested-by

v1: https://lore.kernel.org/all/20230211102207.1267058-1-rppt@kernel.org

 Documentation/mm/physical_memory.rst | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/Documentation/mm/physical_memory.rst b/Documentation/mm/physical_memory.rst
index 3f3c02aa6e6e..d14b785fd938 100644
--- 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   |
   +---------+----------+-----------+ +------------+-------------+
 
+
+Note, that memory banks may belong to interleaving nodes. In the example
+below an x86 machine has 16Gbytes or 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 such case node 0 will span from 0 to 12 Gbytes and node 1 will span from
+4 to 16 Gbytes.
+
 .. _nodes:
 
 Nodes

base-commit: e076f253283c3e55a128fa9665c0e6cd8146948d
-- 
2.35.1