[openwrt/openwrt] netifd: improve packet steering on ipq40xx (and possibly others)

[LEDE Commits]

nbd pushed a commit to openwrt/openwrt.git, branch main:
https://git.openwrt.org/acce25b789d40f2d88a2326a7d9921bd1743fe54

commit acce25b789d40f2d88a2326a7d9921bd1743fe54
Author: Felix Fietkau <nbd at nbd.name>
AuthorDate: Thu Jan 16 12:35:47 2025 +0100

    netifd: improve packet steering on ipq40xx (and possibly others)
    
    Some platforms a single ethernet device for all ports with multiple rx rings
    and NAPI threading enabled. In this case, the steering script was limiting
    performance by keeping all NAPI threads assigned to the same CPU.
    Fix this by assigning each rx queue and the corresponding NAPI task separately.
    Additionally, if the number of rx queues is at least as big as the number of
    CPUs, skip weight based assignment and distribute the load across all CPUs
    directly.
    
    Fixes: https://github.com/openwrt/openwrt/issues/17611
    Signed-off-by: Felix Fietkau <nbd at nbd.name>
---
 .../files/usr/libexec/network/packet-steering.uc   | 51 ++++++++++++++++++++--
 1 file changed, 47 insertions(+), 4 deletions(-)

diff --git a/package/network/config/netifd/files/usr/libexec/network/packet-steering.uc b/package/network/config/netifd/files/usr/libexec/network/packet-steering.uc
index b2229e5d79..34df46d18e 100755
--- a/package/network/config/netifd/files/usr/libexec/network/packet-steering.uc
+++ b/package/network/config/netifd/files/usr/libexec/network/packet-steering.uc
@@ -65,8 +65,9 @@ function cpu_mask(cpu)
 	return sprintf("%x", mask);
 }
 
-function set_netdev_cpu(dev, cpu) {
-	let queues = glob(`/sys/class/net/${dev}/queues/rx-*/rps_cpus`);
+function set_netdev_cpu(dev, cpu, rx_queue) {
+	rx_queue ??= "rx-*";
+	let queues = glob(`/sys/class/net/${dev}/queues/${rx_queue}/rps_cpus`);
 	let val = cpu_mask(cpu);
 	if (disable)
 		val = 0;
@@ -76,7 +77,7 @@ function set_netdev_cpu(dev, cpu) {
 		if (!do_nothing)
 			writefile(queue, `${val}`);
 	}
-	queues = glob(`/sys/class/net/${dev}/queues/rx-*/rps_flow_cnt`);
+	queues = glob(`/sys/class/net/${dev}/queues/${rx_queue}/rps_flow_cnt`);
 	for (let queue in queues) {
 		if (debug || do_nothing)
 			warn(`echo ${local_flows} > ${queue}\n`);
@@ -160,6 +161,9 @@ for (let dev in netdevs) {
 			netdev: [],
 			phy: [],
 			tasks: [],
+			rx_tasks: [],
+			rx_queues: map(glob(`/sys/class/net/${dev}/queues/rx-*/rps_cpus`),
+			               (v) => basename(dirname(v))),
 		};
 	}
 
@@ -187,11 +191,51 @@ for (let path in glob("/proc/*/exe")) {
 			continue;
 
 		push(dev.tasks, pid);
+
+		let napi_match = match(name, /napi\/([^-]*)-(\d+)/);
+		if (napi_match && napi_match[2] > 0)
+			push(dev.rx_tasks, pid);
 		break;
 	}
 }
 
+function assign_dev_queues_cpu(dev) {
+	let num = length(dev.rx_queues);
+	if (num < length(dev.rx_tasks))
+		num = length(dev.rx_tasks);
+
+	for (let i = 0; i < num; i++) {
+		let cpu;
+
+		let task = dev.rx_tasks[i];
+		if (num >= length(cpus))
+			cpu = i % length(cpus);
+		else if (task)
+			cpu = get_next_cpu(napi_weight);
+		else
+			cpu = -1;
+		set_task_cpu(task, cpu);
+
+		let rxq = dev.rx_queues[i];
+		if (!rxq)
+			continue;
+
+		if (num >= length(cpus))
+			cpu = (i + 1) % length(cpus);
+		else if (all_cpus)
+			cpu = -1;
+		else
+			cpu = get_next_cpu(napi_weight, cpu);
+		for (let netdev in dev.netdev)
+			set_netdev_cpu(netdev, cpu, rxq);
+	}
+}
+
 function assign_dev_cpu(dev) {
+	if (length(dev.rx_queues) > 1 &&
+		length(dev.rx_tasks) > 1)
+		return assign_dev_queues_cpu(dev);
+
 	if (length(dev.tasks) > 0) {
 		let cpu = dev.napi_cpu = get_next_cpu(napi_weight);
 		for (let task in dev.tasks)
@@ -204,7 +248,6 @@ function assign_dev_cpu(dev) {
 			cpu = -1;
 		else
 			cpu = get_next_cpu(rx_weight, dev.napi_cpu);
-		dev.rx_cpu = cpu;
 		for (let netdev in dev.netdev)
 			set_netdev_cpu(netdev, cpu);
 	}