Re: [PATCH v4 11/14] arm64/numa: support HAVE_MEMORYLESS_NODES

[Ganapatrao Kulkarni <gpkulkarni@gmail.com>]

On Tue, Jun 7, 2016 at 1:38 PM, Zhen Lei <thunder.leizhen@huawei.com> 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@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 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
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel