Stop your eBPF kprobes from firing blindly when you only need local context

Technical Briefing | 7/31/2026

You probably started playing with eBPF using bpftrace or a quick BCC script to see which process is hammering a specific syscall. It works great in staging. But once you move that to a high-traffic production host, your terminal fills with so much output you can’t even hit Ctrl-C fast enough to stop the self-inflicted DDoS. The problem isn’t the syscall; it’s the lack of filtering.

Why your scripts are actually overhead-heavy monsters

Most eBPF scripts trigger on every single occurrence of an event across the entire system. If you are tracing openat calls, you are capturing every configuration file read, library load, and log rotation happening simultaneously. The kernel spends more time context-switching to your probe handler than actually running your application. You need to push that filtering logic down into the kernel, not handle it in user-space logic.

bpftrace -e 'tracepoint:syscalls:sys_enter_openat /comm == "my_app"/ { printf("%s is opening %s\n", comm, str(args->filename)); }'

• Use process predicates like /comm == name/ to drop events at the source
• Check pids or tids to isolate threads within your specific worker pool
• Avoid printf inside high-frequency loops as the string formatting kills performance
• Aggregate data into maps instead of printing events in real-time

Making it production safe

If you are worried about the overhead of the filter itself, look at what the bytecode is actually doing. Using a PID check is significantly cheaper than checking a process name string repeatedly. I once saw a custom agent crash an entire cluster because it was doing a string compare on every network packet header. Keep your probe predicates simple and narrow, otherwise you’ll find yourself chasing performance issues caused by your own debugger.

Next time you feel the need to trace everything, force yourself to write a single filter condition before you even run the script. It’s a good habit that keeps your logs clean and your CPU cycles reserved for the code that actually pays the bills.