NIC Optimization for Low Latency

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To make your NIC optimization settings permanent across reboots, you can create a systemd service that applies the necessary ethtool and tc qdisc configurations at startup.

Steps:

  1. Create the Script with ethtool and tc Commands
  2. Create a systemd Service File
  3. Enable and Validate the Service

Step 1: Create the Script

First, create a script that includes ethtool and tc settings for low latency.

sudo nano /usr/local/bin/nic-optimization.sh

Add the following commands to the script:

#!/bin/bash

# Disable Interrupt Coalescing
ethtool -C eth0 rx-usecs 0 rx-frames 0
ethtool -C eth0 tx-usecs 0 tx-frames 0

# Disable TCP Offloading
ethtool -K eth0 tso off gso off gro off

# Reduce NIC Ring Buffers
ethtool -G eth0 rx 256
ethtool -G eth0 tx 256

# Disable Flow Control
ethtool -A eth0 rx off tx off

# Set TC (Traffic Control) qdisc to pfifo_fast
tc qdisc replace dev eth0 root pfifo_fast

Make the script executable:

sudo chmod +x /usr/local/bin/nic-optimization.sh

Step 2: Create a systemd Service File

Now, create a systemd service to run the script at startup.

sudo nano /etc/systemd/system/nic-optimization.service

Add the following content:

[Unit]
Description=NIC Optimization for Low Latency
After=network.target

[Service]
Type=oneshot
ExecStart=/usr/local/bin/nic-optimization.sh
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target

Explanation:

  • Type=oneshot: This means the service will run and then exit. It’s not a long-running service.
  • RemainAfterExit=yes: Keeps the service in an active state after it finishes running.
  • ExecStart: Specifies the script that will be executed (/usr/local/bin/nic-optimization.sh).

Step 3: Enable and Start the Service

Now, enable the service to run at boot, start it, and verify that it works.

Check the status to verify it ran successfully:

sudo systemctl status nic-optimization.service

Start the service immediately:

sudo systemctl start nic-optimization.service

Enable the service so it runs at every boot:

sudo systemctl enable nic-optimization.service

Reload systemd to recognize the new service:

sudo systemctl daemon-reload

You should see output similar to:

● nic-optimization.service - NIC Optimization for Low Latency
     Loaded: loaded (/etc/systemd/system/nic-optimization.service; enabled; vendor preset: enabled)
     Active: active (exited) since Mon 2024-10-21 10:00:00 UTC; 2s ago
    Process: 1234 ExecStart=/usr/local/bin/nic-optimization.sh (code=exited, status=0/SUCCESS)
   Main PID: 1234 (code=exited, status=0/SUCCESS)

This confirms that the service ran successfully, applying your NIC optimizations.

Step 4: Validation

To ensure that your settings were applied correctly, you can manually validate the optimizations after the service runs.

Validate ethtool Settings:

Check Flow Control:

ethtool -a eth0

Ensure that RX and TX flow control are set to off.

Check NIC Ring Buffers:

ethtool -g eth0

You should see the RX and TX ring buffers set to 256.

Check TCP Offloading:

ethtool -k eth0

Ensure that tso, gso, and gro are set to off.

Check Interrupt Coalescing:

ethtool -c eth0

You should see values for rx-usecs and tx-usecs as 0, and rx-frames and tx-frames as 0.

Validate tc qdisc:

Check the Active qdisc:

tc qdisc show dev eth0

You should see:

qdisc pfifo_fast 0: root refcnt 2 bands 3 priomap  1 2 2 2 1 2 2 2 1 2 2 2 1 2 2 2

This confirms that the pfifo_fast queuing discipline is active.

Summary of Commands:

  1. Validate the settings:

Check traffic control qdisc:

tc qdisc show dev eth0

Check ethtool settings:

ethtool -c eth0
ethtool -k eth0
ethtool -g eth0
ethtool -a eth0

Check the service status:

sudo systemctl status nic-optimization.service

Enable and start the service:

sudo systemctl enable nic-optimization.service
sudo systemctl start nic-optimization.service

Reload systemd:

sudo systemctl daemon-reload

Create the service file:

sudo nano /etc/systemd/system/nic-optimization.service

Make the script executable:

sudo chmod +x /usr/local/bin/nic-optimization.sh

Create the script:

sudo nano /usr/local/bin/nic-optimization.sh

By following these steps, your NIC optimizations will be applied automatically on boot, ensuring low latency and low jitter persistently. Let me know if you need further assistance!