[RFC,2/3] x86/numa: Introduce numa_remove_memblks(node, start, end)

Commit Message

Alison Schofield May 10, 2023, 6:44 p.m. UTC

From: Alison Schofield <[e-mail]>

Add support for removing memblks from numa_meminfo that are
within a start/end range, and of a node.

numa_add_memblk() allows in kernel users to add a memblk to
a NUMA node. There is no method exposed to remove a memblk.

The use case here is to allow the ACPI driver to remove
redundant memblks when it knows they exist, rather than
implementing a cleanup that needlessly walks all memblks
during a cleanup phase.

numa_cleanup_meminfo() exists for merging memblks, however,
it only considers adjacent memblks, and, it actually moves the
memblks to numa_reserved_meminfo, before doing the cleanup.

Signed-off-by: Alison Schofield <[e-mail]>
---
 arch/x86/include/asm/numa.h |  1 +
 arch/x86/mm/numa.c          | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+)

Comments

Dan Williams May 11, 2023, 10:50 p.m. UTC | #1

alison.schofield@ wrote:
> From: Alison Schofield <[e-mail]>
> 
> Add support for removing memblks from numa_meminfo that are
> within a start/end range, and of a node.
> 
> numa_add_memblk() allows in kernel users to add a memblk to
> a NUMA node. There is no method exposed to remove a memblk.
> 
> The use case here is to allow the ACPI driver to remove
> redundant memblks when it knows they exist, rather than
> implementing a cleanup that needlessly walks all memblks
> during a cleanup phase.

Again this assumes a particular way to solve the memblk update problem,
it's not clear that a remove method is the way to go versus an update
method.

I.e. its not clear to me where the "redundant" memblks appear.


> numa_cleanup_meminfo() exists for merging memblks, however,
> it only considers adjacent memblks, and, it actually moves the
> memblks to numa_reserved_meminfo, before doing the cleanup.

So either the algorithm for solving the extend memblks when they overlap
CFMWS needs to be described here, or this patch needs to be squashed.

Patch

diff --git a/arch/x86/include/asm/numa.h b/arch/x86/include/asm/numa.h
index 5f2b811f1a5f..cb8b9a8cae32 100644
--- a/arch/x86/include/asm/numa.h
+++ b/arch/x86/include/asm/numa.h
@@ -35,6 +35,7 @@  extern nodemask_t numa_nodes_parsed __initdata;
 extern int __init numa_add_memblk(int nodeid, u64 start, u64 end);
 extern void __init numa_set_distance(int from, int to, int distance);
 extern int __init numa_find_node(u64 start, u64 end);
+extern void __init numa_remove_memblks(int node, u64 start, u64 end);
 
 static inline void set_apicid_to_node(int apicid, s16 node)
 {
diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
index 62990977f720..42d70f01ca0a 100644
--- a/arch/x86/mm/numa.c
+++ b/arch/x86/mm/numa.c
@@ -239,6 +239,28 @@  int __init numa_find_node(u64 start, u64 end)
 	return NUMA_NO_NODE;
 }
 
+/**
+ * numa_remove_memblks - Remove memblocks from a node
+ * @node: node
+ * @start: start addr of memblks to remove
+ * @end: end addr of memblks to remove
+ *
+ * Remove any memblks of node within start/end range
+ */
+void __init numa_remove_memblks(int node, u64 start, u64 end)
+{
+	struct numa_meminfo *mi = &numa_meminfo;
+
+	for (int i = 0; i < mi->nr_blks; i++) {
+		struct numa_memblk *bi = &mi->blk[i];
+
+		if (bi->nid != node)
+			continue;
+		if (start <= bi->start && end >= bi->end)
+			numa_remove_memblk_from(i--, &numa_meminfo);
+	}
+}
+
 /**
  * numa_cleanup_meminfo - Cleanup a numa_meminfo
  * @mi: numa_meminfo to clean up