From ea3735f7441e9668d84c3e87cc90bdf89a23b8f5 Mon Sep 17 00:00:00 2001
From: Prabhat Aravind <paravind@microsoft.com>
Date: Tue, 10 Sep 2024 18:45:56 +0000
Subject: [PATCH] [image_config]: Enable Receive Packet Steering (RPS)

 * This patch enables Receive Packet Steering (RPS) which helps to distribute
   softirq processing for CPU bound packets to all available cores. This will
   help prevent kernel packet drops when there are bouts of intense CPU bound
   packets.

   Ref: https://lwn.net/Articles/362339/
        https://docs.kernel.org/networking/scaling.html

Signed-off-by: Prabhat Aravind <paravind@microsoft.com>
---
 .../build_templates/sonic_debian_extension.j2 |  9 ++-
 files/image_config/rps/rps.py                 | 58 +++++++++++++++++++
 files/image_config/udev/rules.d/99-rps.rules  |  1 +
 3 files changed, 67 insertions(+), 1 deletion(-)
 create mode 100755 files/image_config/rps/rps.py
 create mode 100644 files/image_config/udev/rules.d/99-rps.rules

diff --git a/files/build_templates/sonic_debian_extension.j2 b/files/build_templates/sonic_debian_extension.j2
index 1845f9b8c18e..523a3ebda628 100644
--- a/files/build_templates/sonic_debian_extension.j2
+++ b/files/build_templates/sonic_debian_extension.j2
@@ -505,8 +505,10 @@ sudo cp $IMAGE_CONFIGS/resolv-config/update-containers $FILESYSTEM_ROOT/etc/reso
 sudo cp $IMAGE_CONFIGS/interfaces/init_interfaces $FILESYSTEM_ROOT/etc/network/interfaces
 sudo mkdir -p $FILESYSTEM_ROOT/etc/network/interfaces.d
 
-# System'd network udev rules
+# Systemd network udev rules
 sudo cp $IMAGE_CONFIGS/systemd/network/* $FILESYSTEM_ROOT_ETC/systemd/network/
+sudo mkdir -p $FILESYSTEM_ROOT_ETC/udev/rules.d
+sudo cp $IMAGE_CONFIGS/udev/rules.d/* $FILESYSTEM_ROOT_ETC/udev/rules.d/
 
 # copy core file uploader files
 sudo cp $IMAGE_CONFIGS/corefile_uploader/core_uploader.service $FILESYSTEM_ROOT_USR_LIB_SYSTEMD_SYSTEM
@@ -715,6 +717,11 @@ sudo cp $IMAGE_CONFIGS/backend_acl/backend-acl.service $FILESYSTEM_ROOT_USR_LIB_
 sudo cp $IMAGE_CONFIGS/backend_acl/backend_acl.py $FILESYSTEM_ROOT/usr/bin/backend_acl.py
 echo "backend-acl.service" | sudo tee -a $GENERATED_SERVICE_FILE
 
+# Copy RPS script and service file
+sudo cp $IMAGE_CONFIGS/rps/rps.service $FILESYSTEM_ROOT_USR_LIB_SYSTEMD_SYSTEM/rps.service
+sudo cp $IMAGE_CONFIGS/rps/rps.py $FILESYSTEM_ROOT/usr/bin/rps.py
+echo "rps.service" | sudo tee -a $GENERATED_SERVICE_FILE
+
 # Copy SNMP configuration files
 sudo cp $IMAGE_CONFIGS/snmp/snmp.yml $FILESYSTEM_ROOT/etc/sonic/
 
diff --git a/files/image_config/rps/rps.py b/files/image_config/rps/rps.py
new file mode 100755
index 000000000000..70218f941cfc
--- /dev/null
+++ b/files/image_config/rps/rps.py
@@ -0,0 +1,58 @@
+#!/usr/bin/env python3
+
+import os
+import sys
+
+'''
+Script to enable Receive Packet Steering (RPS)
+'''
+def get_num_cpus():
+    ncpus = 0
+    cpu_count = os.cpu_count()
+    if cpu_count is not None:
+        ncpus = cpu_count
+
+    return ncpus
+
+
+def get_cpumask(ncpus):
+    return hex(pow(2, ncpus) - 1)[2:]
+
+
+def configure_rps():
+    rv = 0
+    NET_DIR_PATH = "/sys/class/net"
+
+    num_cpus = get_num_cpus()
+    if not num_cpus:
+        rv = -1
+        return rv
+
+    cpumask = get_cpumask(num_cpus)
+    for intf in os.listdir(NET_DIR_PATH):
+        if "Ethernet" in intf:
+            queues_path = os.path.join(NET_DIR_PATH, intf, "queues")
+            queues = os.listdir(queues_path)
+            num_rx_queues = len([q for q in queues if q.startswith("rx")])
+            for q in range(num_rx_queues):
+                rps_cpus_path = os.path.join(queues_path, "rx-{}", "rps_cpus").format(q)
+                with open(rps_cpus_path, 'w') as file:
+                    print ("Setting {} to cpu mask {}".format(rps_cpus_path, cpumask))
+                    file.write(cpumask)
+
+    return rv
+
+
+def main():
+    rv = 0
+    try:
+        rv = configure_rps()
+    except Exception as e:
+        print ("configure_rps exception occurred: {}".format(str(e)))
+
+    sys.exit(rv)
+
+
+if __name__ == "__main__":
+    main()
+
diff --git a/files/image_config/udev/rules.d/99-rps.rules b/files/image_config/udev/rules.d/99-rps.rules
new file mode 100644
index 000000000000..3764e29af2a5
--- /dev/null
+++ b/files/image_config/udev/rules.d/99-rps.rules
@@ -0,0 +1 @@
+ACTION=="add", SUBSYSTEM=="net", KERNEL=="Ethernet*", RUN+="/usr/bin/rps.py"