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 40e1835b35e881d3479baec9d0bfa7f7ba48da9a..c900b73f92246d77cac96de3f9bd77685cf5d167 100644 (file)
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -263,8 +263,12 @@ static void __cpuinit srat_detect_node(struct cpuinfo_x86 *c)
        /* 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 3acd870d316a84533c219638638ed8ed77d428f1..83bbc70d11bb7a03754b88b432781fa142dffe9e 100644 (file)
--- a/arch/x86/mm/numa_64.c
+++ b/arch/x86/mm/numa_64.c
@@ -764,6 +764,25 @@ static __init int numa_setup(char *opt)
 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 @@ void __init init_cpu_to_node(void)
                if (node == NUMA_NO_NODE)
                        continue;
                if (!node_online(node))
-                       continue;
+                       node = find_near_online_node(node);
                numa_set_node(cpu, node);
        }
 }