netdev - Re: [PATCH 1/4] net: mellanox: drop mlx5_cpumask_default

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Date: Mon, 25 Sep 2023 15:45:23 -0700
From: Jacob Keller <jacob.e.keller@...el.com>
To: Yury Norov <yury.norov@...il.com>, <linux-kernel@...r.kernel.org>,
	<netdev@...r.kernel.org>, <linux-rdma@...r.kernel.org>
CC: Tariq Toukan <ttoukan.linux@...il.com>, Valentin Schneider
	<vschneid@...hat.com>, Maher Sanalla <msanalla@...dia.com>, Ingo Molnar
	<mingo@...nel.org>, Mel Gorman <mgorman@...e.de>, Saeed Mahameed
	<saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>, "David S. Miller"
	<davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
	<kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Peter Zijlstra
	<peterz@...radead.org>, Juri Lelli <juri.lelli@...hat.com>, Vincent Guittot
	<vincent.guittot@...aro.org>, Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Daniel
 Bristot de Oliveira <bristot@...hat.com>, Pawel Chmielewski
	<pawel.chmielewski@...el.com>, Yury Norov <ynorov@...dia.com>
Subject: Re: [PATCH 1/4] net: mellanox: drop mlx5_cpumask_default_spread()



On 9/24/2023 7:05 PM, Yury Norov wrote:
> The function duplicates existing cpumask_local_spread(), and it's O(N),
> while cpumask_local_spread() implementation is based on bsearch, and
> thus is O(log n), so drop mlx5_cpumask_default_spread() and use generic
> cpumask_local_spread().
> 
> Signed-off-by: Yury Norov <yury.norov@...il.com>
> Signed-off-by: Yury Norov <ynorov@...dia.com>
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/eq.c | 28 ++------------------
>  1 file changed, 2 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/eq.c b/drivers/net/ethernet/mellanox/mlx5/core/eq.c
> index ea0405e0a43f..bd9f857cc52d 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/eq.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/eq.c
> @@ -828,30 +828,6 @@ static void comp_irq_release_pci(struct mlx5_core_dev *dev, u16 vecidx)
>  	mlx5_irq_release_vector(irq);
>  }
>  

Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>

> -static int mlx5_cpumask_default_spread(int numa_node, int index)
> -{
> -	const struct cpumask *prev = cpu_none_mask;
> -	const struct cpumask *mask;
> -	int found_cpu = 0;
> -	int i = 0;
> -	int cpu;
> -
> -	rcu_read_lock();
> -	for_each_numa_hop_mask(mask, numa_node) {
> -		for_each_cpu_andnot(cpu, mask, prev) {
> -			if (i++ == index) {
> -				found_cpu = cpu;
> -				goto spread_done;
> -			}
> -		}
> -		prev = mask;
> -	}
> -
> -spread_done:
> -	rcu_read_unlock();
> -	return found_cpu;
> -}
> -
>  static struct cpu_rmap *mlx5_eq_table_get_pci_rmap(struct mlx5_core_dev *dev)
>  {
>  #ifdef CONFIG_RFS_ACCEL
> @@ -873,7 +849,7 @@ static int comp_irq_request_pci(struct mlx5_core_dev *dev, u16 vecidx)
>  	int cpu;
>  
>  	rmap = mlx5_eq_table_get_pci_rmap(dev);
> -	cpu = mlx5_cpumask_default_spread(dev->priv.numa_node, vecidx);
> +	cpu = cpumask_local_spread(vecidx, dev->priv.numa_node);
>  	irq = mlx5_irq_request_vector(dev, cpu, vecidx, &rmap);
>  	if (IS_ERR(irq))
>  		return PTR_ERR(irq);
> @@ -1125,7 +1101,7 @@ int mlx5_comp_vector_get_cpu(struct mlx5_core_dev *dev, int vector)
>  	if (mask)
>  		cpu = cpumask_first(mask);
>  	else
> -		cpu = mlx5_cpumask_default_spread(dev->priv.numa_node, vector);
> +		cpu = cpumask_local_spread(vector, dev->priv.numa_node);
>  
>  	return cpu;
>  }