Re: [PATCH v7 11/14] arm64/numa: support HAVE_MEMORYLESS_NODES

[Will Deacon <will.deacon@arm.com>]

On Wed, Aug 24, 2016 at 03:44:50PM +0800, Zhen Lei wrote:
> Some numa nodes may have no memory. For example:
> 1. cpu0 on node0
> 2. cpu1 on node1
> 3. device0 access the momory from node0 and node1 take the same time.
> 
> So, we can not simply classify device0 to node0 or node1, but we can
> define a node2 which distances to node0 and node1 are the same.
> 
> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
> ---
>  arch/arm64/Kconfig      |  4 ++++
>  arch/arm64/kernel/smp.c |  1 +
>  arch/arm64/mm/numa.c    | 43 +++++++++++++++++++++++++++++++++++++++++--
>  3 files changed, 46 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 2815af6..3a2b6ed 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -611,6 +611,10 @@ config NEED_PER_CPU_EMBED_FIRST_CHUNK
>  	def_bool y
>  	depends on NUMA
> 
> +config HAVE_MEMORYLESS_NODES
> +	def_bool y
> +	depends on NUMA
> +
>  source kernel/Kconfig.preempt
>  source kernel/Kconfig.hz
> 
> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> index d93d433..4879085 100644
> --- a/arch/arm64/kernel/smp.c
> +++ b/arch/arm64/kernel/smp.c
> @@ -619,6 +619,7 @@ static void __init of_parse_and_init_cpus(void)
>  			}
> 
>  			bootcpu_valid = true;
> +			early_map_cpu_to_node(0, of_node_to_nid(dn));

This seems unrelated?

>  			/*
>  			 * cpu_logical_map has already been
> diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
> index 6853db7..114180f 100644
> --- a/arch/arm64/mm/numa.c
> +++ b/arch/arm64/mm/numa.c
> @@ -129,6 +129,14 @@ void __init early_map_cpu_to_node(unsigned int cpu, int nid)
>  		nid = 0;
> 
>  	cpu_to_node_map[cpu] = nid;
> +
> +	/*
> +	 * We should set the numa node of cpu0 as soon as possible, because it
> +	 * has already been set up online before. cpu_to_node(0) will soon be
> +	 * called.
> +	 */
> +	if (!cpu)
> +		set_cpu_numa_node(cpu, nid);

Likewise.

>  }
> 
>  #ifdef CONFIG_HAVE_SETUP_PER_CPU_AREA
> @@ -211,6 +219,35 @@ int __init numa_add_memblk(int nid, u64 start, u64 end)
>  	return ret;
>  }
> 
> +static u64 __init alloc_node_data_from_nearest_node(int nid, const size_t size)
> +{
> +	int i, best_nid, distance;
> +	u64 pa;
> +	DECLARE_BITMAP(nodes_map, MAX_NUMNODES);
> +
> +	bitmap_zero(nodes_map, MAX_NUMNODES);
> +	bitmap_set(nodes_map, nid, 1);
> +
> +find_nearest_node:
> +	best_nid = NUMA_NO_NODE;
> +	distance = INT_MAX;
> +
> +	for_each_clear_bit(i, nodes_map, MAX_NUMNODES)
> +		if (numa_distance[nid][i] < distance) {
> +			best_nid = i;
> +			distance = numa_distance[nid][i];
> +		}
> +
> +	pa = memblock_alloc_nid(size, SMP_CACHE_BYTES, best_nid);
> +	if (!pa) {
> +		BUG_ON(best_nid == NUMA_NO_NODE);
> +		bitmap_set(nodes_map, best_nid, 1);
> +		goto find_nearest_node;
> +	}
> +
> +	return pa;
> +}
> +
>  /**
>   * Initialize NODE_DATA for a node on the local memory
>   */
> @@ -224,7 +261,9 @@ static void __init setup_node_data(int nid, u64 start_pfn, u64 end_pfn)
>  	pr_info("Initmem setup node %d [mem %#010Lx-%#010Lx]\n",
>  		nid, start_pfn << PAGE_SHIFT, (end_pfn << PAGE_SHIFT) - 1);
> 
> -	nd_pa = memblock_alloc_try_nid(nd_size, SMP_CACHE_BYTES, nid);
> +	nd_pa = memblock_alloc_nid(nd_size, SMP_CACHE_BYTES, nid);
> +	if (!nd_pa)
> +		nd_pa = alloc_node_data_from_nearest_node(nid, nd_size);

Why not add memblock_alloc_near_nid to the core code, and make it do
what you need there?

Will