[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>

files/build_templates/sonic_debian_extension.j2

@@ -513,8 +513,10 @@ 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
@@ -723,6 +725,9 @@ 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 file
+sudo cp $IMAGE_CONFIGS/rps/rps.py $FILESYSTEM_ROOT/usr/bin/rps.py
+
 # Copy SNMP configuration files
 sudo cp $IMAGE_CONFIGS/snmp/snmp.yml $FILESYSTEM_ROOT/etc/sonic/
 

files/image_config/rps/rps.py

@@ -0,0 +1,110 @@
+#!/usr/bin/env python3
+"""
+    Script to enable Receive Packet Steering (RPS).
+    This script reads the number of available CPUs in the system
+    and configures RPS on all front-panel ports using sysfs.
+"""
+import os
+import sys
+import syslog
+
+
+def write_syslog(message, *args):
+    """
+    Write a message to syslog.
+
+    Args:
+        message (str): Message string to be logged
+        args: Optional args
+
+    Returns:
+        None
+    """
+
+    if args:
+        message %= args
+    syslog.syslog(syslog.LOG_NOTICE, message)
+
+
+def get_num_cpus():
+    """
+    Get number of CPUs in the system.
+
+    Returns:
+        ncpus (int): Number of CPUs
+    """
+    ncpus = 0
+    cpu_count = os.cpu_count()
+    if cpu_count is not None:
+        ncpus = cpu_count
+
+    return ncpus
+
+
+def get_cpumask(ncpus):
+    """
+    Get a hex cpumask string.
+
+    Args:
+        ncpus (int): Number of CPUs
+
+    Returns:
+        cpu_mask (str): CPU mask as hex string
+    """
+    cpu_mask = '0'
+    if isinstance(ncpus, int) and ncpus >= 0:
+        cpu_mask = hex(pow(2, ncpus) - 1)[2:]
+
+    return cpu_mask
+
+
+def configure_rps():
+    """
+    Configure Receive Packet Steering (RPS)
+
+    Returns:
+        rv (int): zero for success and non-zero otherwise
+    """
+    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)
+    if cpumask == '0':
+        # Nothing to do
+        return rv
+
+    write_syslog("configure_rps: cpu mask {}".format(cpumask))
+
+    # Loop through Ethernet interfaces in /sys/class/net and set rps_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:
+                    file.write(cpumask)
+
+    return rv
+
+
+def main():
+    rv = -1
+    try:
+        rv = configure_rps()
+        write_syslog("configure_rps {}".format("failed" if rv else "successful"))
+    except Exception as e:
+        write_syslog("configure_rps exception: {}".format(str(e)))
+
+    sys.exit(rv)
+
+
+if __name__ == "__main__":
+    main()
+

files/image_config/udev/rules.d/99-rps.rules

@@ -0,0 +1 @@
+ACTION=="add", SUBSYSTEM=="net", KERNEL=="Ethernet*", RUN+="/usr/bin/rps.py"