linux-kernel - Re: [PATCH v2 1/1] mm: only dispaly online cpus of the numa node

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Message-ID: <20171002103806.GB3823@arm.com>
Date:   Mon, 2 Oct 2017 11:38:07 +0100
From:   Will Deacon <will.deacon@....com>
To:     Zhen Lei <thunder.leizhen@...wei.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-api <linux-api@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Michal Hocko <mhocko@...e.com>, linux-mm <linux-mm@...ck.org>,
        Tianhong Ding <dingtianhong@...wei.com>,
        Hanjun Guo <guohanjun@...wei.com>,
        Libin <huawei.libin@...wei.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        akpm@...ux-foundation.org
Subject: Re: [PATCH v2 1/1] mm: only dispaly online cpus of the numa node

[+akpm]

Hi Thunder,

On Fri, Sep 29, 2017 at 05:53:25PM +0800, Zhen Lei wrote:
> When I executed numactl -H(which read /sys/devices/system/node/nodeX/cpumap
> and display cpumask_of_node for each node), but I got different result on
> X86 and arm64. For each numa node, the former only displayed online CPUs,
> and the latter displayed all possible CPUs. Unfortunately, both Linux
> documentation and numactl manual have not described it clear.
> 
> I sent a mail to ask for help, and Michal Hocko <mhocko@...nel.org> replied
> that he preferred to print online cpus because it doesn't really make much
> sense to bind anything on offline nodes.
> 
> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
> Acked-by: Michal Hocko <mhocko@...e.com>
> ---
>  drivers/base/node.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)

Which tree is this intended to go through? I'm happy to take it via arm64,
but I don't want to tread on anybody's toes in linux-next and it looks like
there are already queued changes to this file via Andrew's tree.

Will

> diff --git a/drivers/base/node.c b/drivers/base/node.c
> index 3855902..aae2402 100644
> --- a/drivers/base/node.c
> +++ b/drivers/base/node.c
> @@ -27,13 +27,21 @@ static struct bus_type node_subsys = {
>  
>  static ssize_t node_read_cpumap(struct device *dev, bool list, char *buf)
>  {
> +	ssize_t n;
> +	cpumask_var_t mask;
>  	struct node *node_dev = to_node(dev);
> -	const struct cpumask *mask = cpumask_of_node(node_dev->dev.id);
>  
>  	/* 2008/04/07: buf currently PAGE_SIZE, need 9 chars per 32 bits. */
>  	BUILD_BUG_ON((NR_CPUS/32 * 9) > (PAGE_SIZE-1));
>  
> -	return cpumap_print_to_pagebuf(list, buf, mask);
> +	if (!alloc_cpumask_var(&mask, GFP_KERNEL))
> +		return 0;
> +
> +	cpumask_and(mask, cpumask_of_node(node_dev->dev.id), cpu_online_mask);
> +	n = cpumap_print_to_pagebuf(list, buf, mask);
> +	free_cpumask_var(mask);
> +
> +	return n;
>  }
>  
>  static inline ssize_t node_read_cpumask(struct device *dev,
> -- 
> 2.5.0
> 
>