netdev - Re: [PATCH net-next V1 1/2] net: Utility function to get affinity

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Date:	Mon, 3 Mar 2014 14:14:46 +0530 (IST)
From:	Govindarajulu Varadarajan <gvaradar@...co.com>
To:	Amir Vadai <amirv@...lanox.com>
cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Yevgeny Petrilin <yevgenyp@...lanox.com>,
	Or Gerlitz <ogerlitz@...lanox.com>, prarit@...hat.com
Subject: Re: [PATCH net-next V1 1/2] net: Utility function to get affinity_hint
 by policy



On Sun, 2 Mar 2014, Amir Vadai wrote:

> This function sets the affinity_mask according to a numa aware policy.
> affinity_mask could be used as an affinity hint for the IRQ related to
> this rx queue.
> Current policy is to spread rx queues accross cores - local cores first.
> It could be extended in the future.
>
> CC: Prarit Bhargava <prarit@...hat.com>
> Signed-off-by: Amir Vadai <amirv@...lanox.com>
> ---
> include/linux/netdevice.h |  3 +++
> net/core/dev.c            | 55 +++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 58 insertions(+)
>
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 1a86948..db4fd12 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -2526,6 +2526,9 @@ static inline int netif_set_real_num_rx_queues(struct net_device *dev,
> }
> #endif
>
> +int netif_set_rx_queue_affinity_hint(int rxq, int numa_node,
> +				     cpumask_var_t affinity_mask);
> +
> static inline int netif_copy_real_num_queues(struct net_device *to_dev,
> 					     const struct net_device *from_dev)
> {
> diff --git a/net/core/dev.c b/net/core/dev.c
> index b1b0c8d..a454d15 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -2116,6 +2116,61 @@ int netif_set_real_num_rx_queues(struct net_device *dev, unsigned int rxq)
> EXPORT_SYMBOL(netif_set_real_num_rx_queues);
> #endif
>
> +/* netif_set_rx_queue_affinity_hint - set affinity hint of rx queue
> + * @rxq: index of rx queue
> + * @numa_node: prefered numa_node
> + * @affinity_mask: the relevant cpu bit is set according to the policy
> + *
> + * This function sets the affinity_mask according to a numa aware policy.
> + * affinity_mask coulbe used as an affinity hint for the IRQ related to this
> + * rx queue.
> + * The policy is to spread rx queues accross cores - local cores first.
> + *
> + * Returns 0 on success, or a negative error code.
> + */
> +int netif_set_rx_queue_affinity_hint(int rxq, int numa_node,
> +				     cpumask_var_t affinity_mask)
> +{
> +	const struct cpumask *p_numa_cores_mask;
> +	cpumask_var_t non_numa_cores_mask = NULL;
> +	int affinity_cpu;
> +	int ret = 0;
> +
> +	rxq = rxq % num_online_cpus();
> +
> +	p_numa_cores_mask = cpumask_of_node(numa_node);
> +	if (!p_numa_cores_mask)
> +		p_numa_cores_mask = cpu_online_mask;
> +
> +	for_each_cpu(affinity_cpu, p_numa_cores_mask) {
> +		if (--rxq < 0)
> +			goto out;
> +	}
> +
> +	if (!zalloc_cpumask_var(&non_numa_cores_mask, GFP_KERNEL)) {
> +		ret = -ENOMEM;
> +		goto err;
> +	}
> +
> +	cpumask_xor(non_numa_cores_mask, cpu_online_mask, p_numa_cores_mask);
> +
> +	for_each_cpu(affinity_cpu, non_numa_cores_mask) {
> +		if (--rxq < 0)
> +			goto out;
> +	}
> +
> +	goto err;

Hi Amir

Here ret should have a non-zero value right? Since we failed to find an
affinity hint.

thanks
govind

> +
> +out:
> +	cpumask_set_cpu(affinity_cpu, affinity_mask);
> +
> +err:
> +	free_cpumask_var(non_numa_cores_mask);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(netif_set_rx_queue_affinity_hint);
> +
> /**
>  * netif_get_num_default_rss_queues - default number of RSS queues
>  *
> -- 
> 1.8.3.4
>
> --
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