linux-kernel - [PATCH] docs/mm: Physical Memory: add example of interleaving nodes

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Message-Id: <20230211102207.1267058-1-rppt@kernel.org>
Date:   Sat, 11 Feb 2023 12:22:07 +0200
From:   Mike Rapoport <rppt@...nel.org>
To:     Jonathan Corbet <corbet@....net>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Bagas Sanjaya <bagasdotme@...il.com>,
        David Hildenbrand <david@...hat.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Mel Gorman <mgorman@...e.de>, Michal Hocko <mhocko@...nel.org>,
        Mike Rapoport <rppt@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH] docs/mm: Physical Memory: add example of interleaving nodes

From: "Mike Rapoport (IBM)" <rppt@...nel.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

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

As per Michal's request add an example of interleaving nodes.
This is based on Jon's docs-next of Wednesday.

 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..eb9a7a6d3216 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 Gbytes to 16 Gbytes.
+
 .. _nodes:
 
 Nodes

base-commit: e076f253283c3e55a128fa9665c0e6cd8146948d
-- 
2.35.1