Performance Tuning & Kernel Parameters (Sysctl)

Stop your Linux box from dropping packets during a heavy burst

🧩 The Challenge

Dealing with a web server that just gives up during a traffic spike is maddening. You check your CPU, you check your RAM, and everything looks fine, but the kernel is quietly dropping packets because the backlog is too small.

💡 The Fix

Increase the net.core.netdev_max_backlog so your network interface has a larger buffer before it starts throwing away incoming traffic when the CPU is busy.

sysctl -w net.core.netdev_max_backlog=5000
sysctl -p

⚙️ Why It Works

By raising this limit, you give the kernel more breathing room to queue up frames until the CPU can actually pull them off the wire. Without this tweak, a momentary interrupt storm will lead to silent packet loss that drives you crazy when debugging latency.

🚀 Pro-Tip: Check /proc/net/softnet_stat to see if you are actually dropping packets in the queue before you go cranking this value to the moon.

Linux Tips & Tricks | © ngelinux.com | 7/24/2026