linux-kernel - [PATCH 2/2] make node distance writeable

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Date:	Wed, 18 Jul 2007 11:31:27 +0200
From:	"Joachim Deguara" <joachim.deguara@....com>
To:	"lkml List" <linux-kernel@...r.kernel.org>
cc:	gregkh@...e.de, "Andreas Kleen" <ak@...e.de>, lenb@...nel.org,
	"Christoph Lameter" <clameter@....com>
Subject: [PATCH 2/2] make node distance writeable

This adds the ability to write the node distance for NUMA systems.  This is 
generally handled by the SLIT but unfortunately the large majority of systems 
do not have a SLIT as Windows does not use them. Until now if no SLIT was 
found all remote nodes had a distance of 20 which is ok for 2P systems but 
wrong for 4P and larger.

Signed-off-by: Joachim Deguara <joachim.deguara@....com>


--
Index: kernel/drivers/base/node.c
===================================================================
--- kernel.orig/drivers/base/node.c
+++ kernel/drivers/base/node.c
@@ -129,7 +129,30 @@ static ssize_t node_read_distance(struct
 	len += sprintf(buf + len, "\n");
 	return len;
 }
-static SYSDEV_ATTR(distance, S_IRUGO, node_read_distance, NULL);
+
+//takes a space seperated string as the distances of online nodes
+static ssize_t node_write_distance(struct sys_device * dev, const char * buf,
+					size_t size){
+	int i, ret;
+	u8 dist;
+
+	for_each_online_node(i){
+		if (i){
+			buf = strchr(buf, ' ');
+			buf++;
+		}
+		ret = sscanf(buf, "%hu", &dist);
+		if (!ret)
+			return -EINVAL;
+		if (dist < 10)
+			dist = 10;
+		set_node_distance(dev->id, i, dist);
+	}
+	return size;
+}
+
+static SYSDEV_ATTR(distance, S_IRUGO | S_IWUSR, node_read_distance,
+		node_write_distance);
 
 
 /*
Index: kernel/arch/x86_64/mm/srat.c
===================================================================
--- kernel.orig/arch/x86_64/mm/srat.c
+++ kernel/arch/x86_64/mm/srat.c
@@ -471,6 +471,18 @@ int __node_distance(int a, int b)
 
 EXPORT_SYMBOL(__node_distance);
 
+void __set_node_distance(int a, int b, u8 dist)
+{
+	int index;
+
+	if (!acpi_slit)
+		return;
+	index = acpi_slit->locality_count * node_to_pxm(a);
+	acpi_slit->entry[index + node_to_pxm(b)] = dist;
+}
+
+EXPORT_SYMBOL(__set_node_distance);
+
 int memory_add_physaddr_to_nid(u64 start)
 {
 	int i, ret = 0;
Index: kernel/include/asm-x86_64/topology.h
===================================================================
--- kernel.orig/include/asm-x86_64/topology.h
+++ kernel/include/asm-x86_64/topology.h
@@ -14,7 +14,9 @@ extern cpumask_t     node_to_cpumask[];
 
 #ifdef CONFIG_ACPI_NUMA
 extern int __node_distance(int, int);
+extern void __set_node_distance(int, int, u8);
 #define node_distance(a,b) __node_distance(a,b)
+#define set_node_distance(a,b,dist) __set_node_distance(a,b,dist)
 /* #else fallback version */
 #endif
 


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