On Tue, Jun 7, 2016 at 1:38 PM, Zhen Lei <thunder.leizhen@xxxxxxxxxx> 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.
i am wondering, if access to both nodes is same, then why you need numa.
the example you are quoting is against the basic principle of "numa"
what is device0 here? cpu?
>
> 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@xxxxxxxxxx>
> ---
> 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 05c1bf1..5904a62 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -581,6 +581,10 @@ 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 d099306..9e15297 100644
> --- a/arch/arm64/kernel/smp.c
> +++ b/arch/arm64/kernel/smp.c
> @@ -620,6 +620,7 @@ static void __init of_parse_and_init_cpus(void)
> }
>
> bootcpu_valid = true;
> + early_map_cpu_to_node(0, of_node_to_nid(dn));
>
> /*
> * cpu_logical_map has already been
> diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
> index df5c842..d73b0a0 100644
> --- a/arch/arm64/mm/numa.c
> +++ b/arch/arm64/mm/numa.c
> @@ -128,6 +128,14 @@ 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);
> }
>
> #ifdef CONFIG_HAVE_SETUP_PER_CPU_AREA
> @@ -215,6 +223,35 @@ 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
> */
> @@ -228,7 +265,9 @@ 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);
> nd = __va(nd_pa);
>
> /* report and initialize */
> @@ -238,7 +277,7 @@ static void __init setup_node_data(int nid, u64 start_pfn, u64 end_pfn)
> if (tnid != nid)
> pr_info(" NODE_DATA(%d) on node %d\n", nid, tnid);
>
> - node_data[nid] = nd;
> + NODE_DATA(nid) = nd;
> memset(NODE_DATA(nid), 0, sizeof(pg_data_t));
> NODE_DATA(nid)->node_id = nid;
> NODE_DATA(nid)->node_start_pfn = start_pfn;
> --
> 2.5.0
>
>
Ganapat
>
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