linux-kernel - Re: [PATCH 47/49] nodemask: add num_node_state

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Date:   Fri, 11 Feb 2022 12:41:42 +0200
From:   Mike Rapoport <rppt@...nel.org>
To:     Yury Norov <yury.norov@...il.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        David Laight <David.Laight@...lab.com>,
        Joe Perches <joe@...ches.com>, Dennis Zhou <dennis@...nel.org>,
        Emil Renner Berthing <kernel@...il.dk>,
        Nicholas Piggin <npiggin@...il.com>,
        Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        Alexey Klimov <aklimov@...hat.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 47/49] nodemask: add num_node_state_eq()

On Thu, Feb 10, 2022 at 02:49:31PM -0800, Yury Norov wrote:
> Page allocator uses num_node_state() to compare number of nodes with a
> given number. The underlying code calls bitmap_weight(), and we can do
> it more efficiently with num_node_state_eq because conditional nodes_weight
> may stop traversing the nodemask earlier, as soon as condition is (or is
> not) met.
> 
> Signed-off-by: Yury Norov <yury.norov@...il.com>

Acked-by: Mike Rapoport <rppt@...ux.ibm.com>

> ---
>  include/linux/nodemask.h | 5 +++++
>  mm/page_alloc.c          | 2 +-
>  2 files changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/nodemask.h b/include/linux/nodemask.h
> index 197598e075e9..c5014dbf3cce 100644
> --- a/include/linux/nodemask.h
> +++ b/include/linux/nodemask.h
> @@ -466,6 +466,11 @@ static inline int num_node_state(enum node_states state)
>  	return nodes_weight(node_states[state]);
>  }
>  
> +static inline int num_node_state_eq(enum node_states state, int num)
> +{
> +	return nodes_weight_eq(node_states[state], num);
> +}
> +
>  #define for_each_node_state(__node, __state) \
>  	for_each_node_mask((__node), node_states[__state])
>  
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index cface1d38093..897e64b66ca4 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8434,7 +8434,7 @@ void __init page_alloc_init(void)
>  	int ret;
>  
>  #ifdef CONFIG_NUMA
> -	if (num_node_state(N_MEMORY) == 1)
> +	if (num_node_state_eq(N_MEMORY, 1))
>  		hashdist = 0;
>  #endif
>  
> -- 
> 2.32.0
> 
> 

-- 
Sincerely yours,
Mike.