linux-kernel - Re: [PATCH 2/2] x86/mm/numa: remove the numa_nodemask_from

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Date:   Fri, 17 Feb 2017 22:18:57 +0800
From:   Wei Yang <richard.weiyang@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Tejun Heo <tj@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Wei Yang <richard.weiyang@...il.com>
Subject: Re: [PATCH 2/2] x86/mm/numa: remove the numa_nodemask_from_meminfo()

Hi,

Willing to hear from all of you :-)

On Mon, Feb 6, 2017 at 11:35 PM, Wei Yang <richard.weiyang@...il.com> wrote:
> numa_nodemask_from_meminfo() is called to set bit according to
> numa_meminfo. While the only two places for this call is used to set proper
> bit to a copy of numa_nodes_parsed from numa_meminfo. With current code
> path, those numa node information in numa_meminfo is a subset of
> numa_nodes_parsed. So it is not necessary to set the bits again.
>
> The following is a code path analysis to prove the numa node information in
> numa_meminfo is a subset of numa_nodes_parsed.
>
>     x86_numa_init()
>         numa_init()
>             Case 1
>             acpi_numa_init()
>                 acpi_parse_memory_affinity()
>                     numa_add_memblk()
>                     node_set(numa_nodes_parsed)
>                 acpi_parse_slit()
>                     numa_nodemask_from_meminfo()
>
>             Case 2
>             amd_numa_init()
>                 numa_add_memblk()
>                 node_set(numa_nodes_parsed)
>
>             Case 3
>             dummy_numa_init()
>                 node_set(numa_nodes_parsed)
>                 numa_add_memblk()
>
>             numa_register_memblks()
>                 numa_nodemask_from_meminfo()
>
> From the code path analysis, we can see each time a memblk is added, the
> proper bit is set in numa_nodes_parsed, which means it is not necessary to
> set it again in numa_nodemask_from_meminfo() for a copy of
> numa_nodes_parsed.
>
> This patch removes numa_nodemask_from_meminfo().
>
> Signed-off-by: Wei Yang <richard.weiyang@...il.com>
> ---
>  arch/x86/mm/numa.c | 21 +--------------------
>  1 file changed, 1 insertion(+), 20 deletions(-)
>
> diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
> index 3e9110b34147..4c9070507a59 100644
> --- a/arch/x86/mm/numa.c
> +++ b/arch/x86/mm/numa.c
> @@ -314,20 +314,6 @@ int __init numa_cleanup_meminfo(struct numa_meminfo *mi)
>         return 0;
>  }
>
> -/*
> - * Set nodes, which have memory in @mi, in *@...emask.
> - */
> -static void __init numa_nodemask_from_meminfo(nodemask_t *nodemask,
> -                                             const struct numa_meminfo *mi)
> -{
> -       int i;
> -
> -       for (i = 0; i < ARRAY_SIZE(mi->blk); i++)
> -               if (mi->blk[i].start != mi->blk[i].end &&
> -                   mi->blk[i].nid != NUMA_NO_NODE)
> -                       node_set(mi->blk[i].nid, *nodemask);
> -}
> -
>  /**
>   * numa_reset_distance - Reset NUMA distance table
>   *
> @@ -347,16 +333,12 @@ void __init numa_reset_distance(void)
>
>  static int __init numa_alloc_distance(void)
>  {
> -       nodemask_t nodes_parsed;
>         size_t size;
>         int i, j, cnt = 0;
>         u64 phys;
>
>         /* size the new table and allocate it */
> -       nodes_parsed = numa_nodes_parsed;
> -       numa_nodemask_from_meminfo(&nodes_parsed, &numa_meminfo);
> -
> -       for_each_node_mask(i, nodes_parsed)
> +       for_each_node_mask(i, numa_nodes_parsed)
>                 cnt = i;
>         cnt++;
>         size = cnt * cnt * sizeof(numa_distance[0]);
> @@ -535,7 +517,6 @@ static int __init numa_register_memblks(struct numa_meminfo *mi)
>
>         /* Account for nodes with cpus and no memory */
>         node_possible_map = numa_nodes_parsed;
> -       numa_nodemask_from_meminfo(&node_possible_map, mi);
>         if (WARN_ON(nodes_empty(node_possible_map)))
>                 return -EINVAL;
>
> --
> 2.11.0
>