linux-kernel - Re: [PATCH v7 12/14] arm64/numa: remove the limitation that cpu0 must bind to node0

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Date:   Fri, 26 Aug 2016 16:49:42 +0100
From:   Will Deacon <will.deacon@....com>
To:     Zhen Lei <thunder.leizhen@...wei.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        devicetree <devicetree@...r.kernel.org>,
        Zefan Li <lizefan@...wei.com>, Xinwei Hu <huxinwei@...wei.com>,
        Tianhong Ding <dingtianhong@...wei.com>,
        Hanjun Guo <guohanjun@...wei.com>
Subject: Re: [PATCH v7 12/14] arm64/numa: remove the limitation that cpu0
 must bind to node0

On Wed, Aug 24, 2016 at 03:44:51PM +0800, Zhen Lei wrote:
> 1. Currently only cpu0 set on cpu_possible_mask and percpu areas have not
>    been initialized.
> 2. No reason to limit cpu0 must belongs to node0.

Whilst I suspect you're using enumerated lists in order to try to make
things clearer, I'm having a really hard time understanding the commit
messages you have in this series. It's actually much better if you
structure them as concise paragraphs explaining:

  - What is the problem that you're fixing?

  - How does that problem manifest?

  - How does the patch fix it?

As far as I can see, this patch just removes a bunch of code with no
explanation as to why it's not required or any problems caused by
keeping it around.

Will

> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
> ---
>  arch/arm64/mm/numa.c | 12 ++----------
>  1 file changed, 2 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
> index 114180f..07a1978 100644
> --- a/arch/arm64/mm/numa.c
> +++ b/arch/arm64/mm/numa.c
> @@ -94,7 +94,6 @@ void numa_clear_node(unsigned int cpu)
>   */
>  static void __init setup_node_to_cpumask_map(void)
>  {
> -	unsigned int cpu;
>  	int node;
> 
>  	/* setup nr_node_ids if not done yet */
> @@ -107,9 +106,6 @@ static void __init setup_node_to_cpumask_map(void)
>  		cpumask_clear(node_to_cpumask_map[node]);
>  	}
> 
> -	for_each_possible_cpu(cpu)
> -		set_cpu_numa_node(cpu, NUMA_NO_NODE);
> -
>  	/* cpumask_of_node() will now work */
>  	pr_debug("Node to cpumask map for %d nodes\n", nr_node_ids);
>  }
> @@ -119,13 +115,13 @@ static void __init setup_node_to_cpumask_map(void)
>   */
>  void numa_store_cpu_info(unsigned int cpu)
>  {
> -	map_cpu_to_node(cpu, numa_off ? 0 : cpu_to_node_map[cpu]);
> +	map_cpu_to_node(cpu, cpu_to_node_map[cpu]);
>  }
> 
>  void __init early_map_cpu_to_node(unsigned int cpu, int nid)
>  {
>  	/* fallback to node 0 */
> -	if (nid < 0 || nid >= MAX_NUMNODES)
> +	if (nid < 0 || nid >= MAX_NUMNODES || numa_off)
>  		nid = 0;
> 
>  	cpu_to_node_map[cpu] = nid;
> @@ -375,10 +371,6 @@ static int __init numa_init(int (*init_func)(void))
> 
>  	setup_node_to_cpumask_map();
> 
> -	/* init boot processor */
> -	cpu_to_node_map[0] = 0;
> -	map_cpu_to_node(0, 0);
> -
>  	return 0;
>  }
> 
> --
> 2.5.0
> 
>