[RFC PATCH 2/3] topology: support node_numa_mem() for determining the fallback node

[Joonsoo Kim]

2014-02-06 David Rientjes <rientjes at google.com>:
> On Thu, 6 Feb 2014, Joonsoo Kim wrote:
>
>> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim at lge.com>
>>
>
> I may be misunderstanding this patch and there's no help because there's
> no changelog.

Sorry about that.
I made this patch just for testing. :)
Thanks for looking this.

>> diff --git a/include/linux/topology.h b/include/linux/topology.h
>> index 12ae6ce..a6d5438 100644
>> --- a/include/linux/topology.h
>> +++ b/include/linux/topology.h
>> @@ -233,11 +233,20 @@ static inline int numa_node_id(void)
>>   * Use the accessor functions set_numa_mem(), numa_mem_id() and cpu_to_mem().
>>   */
>>  DECLARE_PER_CPU(int, _numa_mem_);
>> +int _node_numa_mem_[MAX_NUMNODES];
>>
>>  #ifndef set_numa_mem
>>  static inline void set_numa_mem(int node)
>>  {
>>       this_cpu_write(_numa_mem_, node);
>> +     _node_numa_mem_[numa_node_id()] = node;
>> +}
>> +#endif
>> +
>> +#ifndef get_numa_mem
>> +static inline int get_numa_mem(int node)
>> +{
>> +     return _node_numa_mem_[node];
>>  }
>>  #endif
>>
>> @@ -260,6 +269,7 @@ static inline int cpu_to_mem(int cpu)
>>  static inline void set_cpu_numa_mem(int cpu, int node)
>>  {
>>       per_cpu(_numa_mem_, cpu) = node;
>> +     _node_numa_mem_[numa_node_id()] = node;
>
> The intention seems to be that _node_numa_mem_[X] for a node X will return
> a node Y with memory that has the nearest distance?  In other words,
> caching the value returned by local_memory_node(X)?

Yes, you are right.

> That doesn't seem to be what it's doing since numa_node_id() is the node
> of the cpu that current is running on so this ends up getting initialized
> to whatever local_memory_node(cpu_to_node(cpu)) is for the last bit set in
> cpu_possible_mask.

Yes, I made a mistake.
Thanks for pointer.
I fix it and attach v2.
Now I'm out of office, so I'm not sure this second version is correct :(

Thanks.

----------8<--------------
>From bf691e7eb07f966e3aed251eaeb18f229ee32d1f Mon Sep 17 00:00:00 2001
From: Joonsoo Kim <iamjoonsoo.kim at lge.com>
Date: Thu, 6 Feb 2014 17:07:05 +0900
Subject: [RFC PATCH 2/3 v2] topology: support node_numa_mem() for
determining the
 fallback node

We need to determine the fallback node in slub allocator if the allocation
target node is memoryless node. Without it, the SLUB wrongly select
the node which has no memory and can't use a partial slab, because of node
mismatch. Introduced function, node_numa_mem(X), will return
a node Y with memory that has the nearest distance. If X is memoryless
node, it will return nearest distance node, but, if
X is normal node, it will return itself.

We will use this function in following patch to determine the fallback
node.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim at lge.com>

diff --git a/include/linux/topology.h b/include/linux/topology.h
index 12ae6ce..66b19b8 100644
--- a/include/linux/topology.h
+++ b/include/linux/topology.h
@@ -233,11 +233,20 @@ static inline int numa_node_id(void)
  * Use the accessor functions set_numa_mem(), numa_mem_id() and cpu_to_mem().
  */
 DECLARE_PER_CPU(int, _numa_mem_);
+int _node_numa_mem_[MAX_NUMNODES];

 #ifndef set_numa_mem
 static inline void set_numa_mem(int node)
 {
  this_cpu_write(_numa_mem_, node);
+ _node_numa_mem_[numa_node_id()] = node;
+}
+#endif
+
+#ifndef get_numa_mem
+static inline int get_numa_mem(int node)
+{
+ return _node_numa_mem_[node];
 }
 #endif

@@ -260,6 +269,7 @@ static inline int cpu_to_mem(int cpu)
 static inline void set_cpu_numa_mem(int cpu, int node)
 {
  per_cpu(_numa_mem_, cpu) = node;
+ _node_numa_mem_[cpu_to_node(cpu)] = node;
 }
 #endif

@@ -273,6 +283,13 @@ static inline int numa_mem_id(void)
 }
 #endif

+#ifndef get_numa_mem
+static inline int get_numa_mem(int node)
+{
+ return node;
+}
+#endif
+
 #ifndef cpu_to_mem
 static inline int cpu_to_mem(int cpu)
 {
-- 
1.7.9.5