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

Mike Rapoport
2023-02-12T09:55:07Z

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