Re: [PATCH net-next V1 1/2] net: Utility function to get affinity_hint by policy

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 <redacted>
Signed-off-by: Amir Vadai <redacted>
---
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;