On Tue, 9 Sep 2014 12:03:27 -0700 Nishanth Aravamudan <nacc@xxxxxxxxxxxxxxxxxx> wrote:
> From: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
>
> 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_to_mem_node(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.
>
> ...
>
> --- a/include/linux/topology.h
> +++ b/include/linux/topology.h
> @@ -119,11 +119,20 @@ static inline int numa_node_id(void)
> * Use the accessor functions set_numa_mem(), numa_mem_id() and cpu_to_mem().
This comment could be updated.
> */
> DECLARE_PER_CPU(int, _numa_mem_);
> +extern 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 node_to_mem_node
> +static inline int node_to_mem_node(int node)
> +{
> + return _node_numa_mem_[node];
> }
A wee bit of documentation wouldn't hurt.
How does node_to_mem_node(numa_node_id()) differ from numa_mem_id()?
If I'm reading things correctly, they should both always return the
same thing. If so, do we need both?
Will node_to_mem_node() ever actually be called with a node !=
numa_node_id()?
> #endif
>
> @@ -146,6 +155,7 @@ 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
>
> @@ -159,6 +169,13 @@ static inline int numa_mem_id(void)
> }
> #endif
>
> +#ifndef node_to_mem_node
> +static inline int node_to_mem_node(int node)
> +{
> + return node;
> +}
> +#endif
> +
> #ifndef cpu_to_mem
> static inline int cpu_to_mem(int cpu)
> {
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 18cee0d4c8a2..0883c42936d4 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -85,6 +85,7 @@ EXPORT_PER_CPU_SYMBOL(numa_node);
> */
> DEFINE_PER_CPU(int, _numa_mem_); /* Kernel "local memory" node */
> EXPORT_PER_CPU_SYMBOL(_numa_mem_);
> +int _node_numa_mem_[MAX_NUMNODES];
How does this get updated as CPUs, memory and nodes are hot-added and
removed?
> #endif
>
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