x86, numa: Use near(er) online node instead of roundrobin for NUMA
CPU to node mapping is set via the following sequence:
1. numa_init_array(): Set up roundrobin from cpu to online node
2. init_cpu_to_node(): Set that according to apicid_to_node[]
according to srat only handle the node that
is online, and leave other cpu on node
without ram (aka not online) to still
roundrobin.
3. later call srat_detect_node for Intel/AMD, will use first_online
node or nearby node.
Problem is that setup_per_cpu_areas() is not called between 2 and 3,
the per_cpu for cpu on node with ram is on different node, and could
put that on node with two hops away.
So try to optimize this and add find_near_online_node() and call
init_cpu_to_node().
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <4B07A739.3030104@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 40e1835..c900b73 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -263,8 +263,12 @@
/* Don't do the funky fallback heuristics the AMD version employs
for now. */
node = apicid_to_node[apicid];
- if (node == NUMA_NO_NODE || !node_online(node))
+ if (node == NUMA_NO_NODE)
node = first_node(node_online_map);
+ else if (!node_online(node)) {
+ /* reuse the value from init_cpu_to_node() */
+ node = cpu_to_node(cpu);
+ }
numa_set_node(cpu, node);
printk(KERN_INFO "CPU %d/0x%x -> Node %d\n", cpu, apicid, node);
diff --git a/arch/x86/mm/numa_64.c b/arch/x86/mm/numa_64.c
index 3acd870..83bbc70 100644
--- a/arch/x86/mm/numa_64.c
+++ b/arch/x86/mm/numa_64.c
@@ -764,6 +764,25 @@
early_param("numa", numa_setup);
#ifdef CONFIG_NUMA
+
+static __init int find_near_online_node(int node)
+{
+ int n, val;
+ int min_val = INT_MAX;
+ int best_node = -1;
+
+ for_each_online_node(n) {
+ val = node_distance(node, n);
+
+ if (val < min_val) {
+ min_val = val;
+ best_node = n;
+ }
+ }
+
+ return best_node;
+}
+
/*
* Setup early cpu_to_node.
*
@@ -795,7 +814,7 @@
if (node == NUMA_NO_NODE)
continue;
if (!node_online(node))
- continue;
+ node = find_near_online_node(node);
numa_set_node(cpu, node);
}
}