rayrapetyan / rps-rfs-configuration

A script for configuring the Receive Packet Steering (RPS) and Receive Flow Steering (RFS) on linux

rps-rfs-configuration

A script for configuring the Receive Packet Steering (RPS) and Receive Flow Steering (RFS) on linux

This script helps in configuring RPS and RFS on a linux machine and works as follows.

1. First it finds the number of CPU cores available on system
2. Finds the number of tx/rx queues available on specified interface
3. Finds the CPU core which is assigned to process the interrupts and handle packets for a tx/rx queue using /proc/interrupts output.
4. Configures the CPU mask for RPS based on CPU core set for a particular queue.

For example, lets say rx-0 queue was assigned CPU core 0 and there are 8 cores available on system.

if smp_affinity for rx-0 queue - CPU core '0' specified as mask '00000001' (from /proc/interrupt output) then, RPS for rx-0 is configured as '11111110' - Which means interrupt is still handled by CPU core '0' but processing of packets is now distributed among CPU cores 1-7. This reduces load on CPU core '0' and promotes high PPS (packets per second)

Without RPS configuration, the CPU core '0' handles the soft_irq - interrupt generated when a packet is received on interface and also processes the packet - sending the packet to TCP/IP stack. On configuring RPS - this packet processing is offloaded to other cores.

5. RFS configuration is applied on top of RPS configuration

Applying these configurations on AWS EC2 instances might help in acheiving more PPS as we are limited by number of queues available on an EC2 instance (8 queues)

Reference Links - RPS/RFS

1. https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/performance_tuning_guide/network-rps
2. https://balodeamit.blogspot.com/2013/10/receive-side-scaling-and-receive-packet.html
3. https://www.kernel.org/doc/Documentation/networking/scaling.txt
4. https://medium.com/@Pinterest_Engineering/building-pinterest-in-the-cloud-6c7280dcc196
5. https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/performance_tuning_guide/network-rfs

Sample Usage

# python rps.py eth0 --configure-rfs
Number of CPU(s) available.. : 16
Number of queues in interface 'eth0'.. : 8
Mapping the corresponding TX queue to same CPU(s) as RX queue
Setting RPS CPU mask for /sys/class/net/eth0/queues/rx-1/rps_cpus as fbff
Setting RPS CPU mask for /sys/class/net/eth0/queues/tx-1/xps_cpus as fbff
Setting RPS CPU mask for /sys/class/net/eth0/queues/rx-0/rps_cpus as f7ff
Setting RPS CPU mask for /sys/class/net/eth0/queues/tx-0/xps_cpus as f7ff
Setting RPS CPU mask for /sys/class/net/eth0/queues/rx-3/rps_cpus as ff7f
Setting RPS CPU mask for /sys/class/net/eth0/queues/tx-3/xps_cpus as ff7f
Setting RPS CPU mask for /sys/class/net/eth0/queues/rx-2/rps_cpus as fdff
Setting RPS CPU mask for /sys/class/net/eth0/queues/tx-2/xps_cpus as fdff
Setting RPS CPU mask for /sys/class/net/eth0/queues/rx-5/rps_cpus as ffdf
Setting RPS CPU mask for /sys/class/net/eth0/queues/tx-5/xps_cpus as ffdf
Setting RPS CPU mask for /sys/class/net/eth0/queues/rx-4/rps_cpus as feff
Setting RPS CPU mask for /sys/class/net/eth0/queues/tx-4/xps_cpus as feff
Setting RPS CPU mask for /sys/class/net/eth0/queues/rx-7/rps_cpus as bfff
Setting RPS CPU mask for /sys/class/net/eth0/queues/tx-7/xps_cpus as bfff
Setting RPS CPU mask for /sys/class/net/eth0/queues/rx-6/rps_cpus as fff7
Setting RPS CPU mask for /sys/class/net/eth0/queues/tx-6/xps_cpus as fff7
Setting /proc/sys/net/core/rps_sock_flow_entries with value 32768
Configuring /sys/class/net/eth0/queues/rx-7/rps_flow_cnt with value 2048
Configuring /sys/class/net/eth0/queues/rx-5/rps_flow_cnt with value 2048
Configuring /sys/class/net/eth0/queues/rx-3/rps_flow_cnt with value 2048
Configuring /sys/class/net/eth0/queues/rx-1/rps_flow_cnt with value 2048
Configuring /sys/class/net/eth0/queues/rx-6/rps_flow_cnt with value 2048
Configuring /sys/class/net/eth0/queues/rx-4/rps_flow_cnt with value 2048
Configuring /sys/class/net/eth0/queues/rx-2/rps_flow_cnt with value 2048
Configuring /sys/class/net/eth0/queues/rx-0/rps_flow_cnt with value 2048
#

Note You might want to update the regex in rps.py script which is used to match the interface queue in /proc/interrupt output. This is used to grab the queue number and associated CPU core handling the interrupt