Re: [PATCH v4] Documentation, dt, numa: Add note to empty NUMA node
From: Gavin Shan
Date: Fri Jun 25 2021 - 04:37:03 EST
On 6/25/21 5:06 PM, Andrew Jones wrote:
On Fri, Jun 25, 2021 at 09:02:17AM +0200, Andrew Jones wrote:
On Fri, Jun 25, 2021 at 01:23:38PM +0800, Gavin Shan wrote:
The empty memory nodes, where no memory resides in, are allowed.
For these empty memory nodes, the 'len' of 'reg' property is zero.
The NUMA node IDs are still valid and parsed, but memory can be
added to them through hotplug afterwards. I finds difficulty to
get where it's properly documented.
So lets add note to empty memory nodes in the NUMA binding doc.
Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
---
Documentation/devicetree/bindings/numa.txt | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/Documentation/devicetree/bindings/numa.txt b/Documentation/devicetree/bindings/numa.txt
index 21b35053ca5a..0fc882e44270 100644
--- a/Documentation/devicetree/bindings/numa.txt
+++ b/Documentation/devicetree/bindings/numa.txt
@@ -109,6 +109,10 @@ Example:
Dual socket system consists of 2 boards connected through ccn bus and
each board having one socket/soc of 8 cpus, memory and pci bus.
+Note that empty memory nodes, which no memory resides in, are allowed.
+The NUMA node IDs in these empty memory nodes are still valid, but
+memory can be added into them through hotplug afterwards.
Please change the second sentence to:
The NUMA node IDs in these empty memory nodes are still valid and
memory may be added into them through hotplug afterwards.
But, this doesn't look like the right place for this paragraph. You're
adding the paragraph to the example section, but the example doesn't have
any empty memory nodes.
I think the paragraph should be added to section "2 - numa-node-id" and an
Or maybe even create a new section for it.
example empty memory node should be provided. Also, the commit message
talks about the length of 'reg' being zero, which is an important
distinction which should also be documented.
Drew, thanks for your comments. Yeah, it sounds sensible to create
a new section for it and an example would be more helpful. Please
check if below changes are fine to you. I probably need Randy's review
again.
I'm trying to avoid too many revisions for this sort of trivial patch,
even though I already had. However, it's time frame for v5.14 and I'm
pushing this to be merged during the cycle.
--- a/Documentation/devicetree/bindings/numa.txt
+++ b/Documentation/devicetree/bindings/numa.txt
@@ -103,7 +103,65 @@ Example:
};
==============================================================================
-4 - Example dts
+4 - Empty memory node
+==============================================================================
+
+Empty memory nodes, which no memory resides in, are allowed. The 'length'
+field of 'reg' property is zero, but 'base-address' is dummy and invalid
+for these empty memory nodes. However, the NUMA node IDs and distance maps
+for them are still valid, but memory may be added into them through hotplug
+afterwards.
+
+Example:
+
+ memory@0 {
+ device_type = "memory";
+ reg = <0x0 0x0 0x0 0x80000000>;
+ numa-node-id = <0>;
+ };
+
+ memory@0x80000000 {
+ device_type = "memory";
+ reg = <0x0 0x80000000 0x0 0x80000000>;
+ numa-node-id = <1>;
+ };
+
+ /* Empty memory node */
+ memory@0x100000000 {
+ device_type = "memory";
+ reg = <0x1 0x0 0x0 0x0>;
+ numa-node-id = <2>;
+ };
+
+ /* Empty memory node */
+ memory@0x180000000 {
+ device_type = "memory";
+ reg = <0x1 0x80000000 0x0 0x0>;
+ numa-node-id = <3>;
+ };
+
+ distance-map {
+ compatible = "numa-distance-map-v1";
+ distance-matrix = <0 0 10>,
+ <0 1 20>,
+ <0 2 40>,
+ <0 3 20>,
+ <1 0 20>,
+ <1 1 10>,
+ <1 2 20>,
+ <1 3 40>,
+ <2 0 40>,
+ <2 1 20>,
+ <2 2 10>,
+ <2 3 20>,
+ <3 0 20>,
+ <3 1 40>,
+ <3 2 20>,
+ <3 3 10>;
+ };
+
+==============================================================================
+5 - Example dts
==============================================================================
Dual socket system consists of 2 boards connected through ccn bus and
Thanks,
Gavin