gethostlatency.bt(8)

📦
version 0.27.0 · 4 versions
, in alpine 3.24, arch rolling, centos-stream 10, centos-stream 9, nixos 26.05, nixpkgs unstable, ubuntu resolute, ubuntu stonking

✨ gethostlatency.bt(8) — bestie edition ✨

okay so this is a page from the System Manager's Manual and the star of the show is gethostlatency.bt — say hi 👋

🌸 NAME 🌸

gethostlatency.bt — shows you the latency for getaddrinfo / gethostbyname[2] calls. it runs on bpftrace / eBPF, no cap 💅

🎀 SYNOPSIS 🎀

gethostlatency.bt

that's it. that's the whole vibe. no flags, no drama, just run it 🦋

💖 DESCRIPTION 💖

so what this cutie does is trace and print every time gethostbyaddr(), getaddrinfo(), gethostbyname(), and gethostbyname2() get called — system wide — and then it tells you:

  • the responsible PID and command name 👑
  • the latency of the call (duration) in milliseconds ⏱️
  • and the host string 🏠

it's giving DNS detective energy fr fr 🔍

this tool is lowkey iconic for identifying DNS latency — like, it shows you which remote host name lookups were slow, and by how much. obsessed.

⚠️ heads up bestie: this tool currently uses dynamic tracing of user-level functions and registers, so it may need modifications to match your software and processor architecture. it's not one-size-fits-all, okay? 🙈
👑 and since this uses BPF, only the root user can use this tool. root access only, periodt.

🌈 REQUIREMENTS 🌈

  • CONFIG_BPF
  • bcc

that's the whole shopping list 🛍️

⭐ EXAMPLES ⭐

trace host lookups (getaddrinfo / gethostbyname[2]) system wide:

# gethostlatency.bt

and that's it, she's running 💫

🍓 FIELDS 🍓

  • TIME — time of the command, in HH:MM:SS format 🕐
  • PID — process ID of the client performing the call 🆔
  • COMM — process (command) name of the client performing the call 🏷️
  • LATms — latency of the call, in milliseconds ⏱️
  • HOST — host name string: the target of the lookup 🎯

🧚 OVERHEAD 🧚

the rate of lookups should be relatively low, so the overhead is not expected to be a problem. breathe, bestie, it's fine 😌✨

💜 SOURCE 💜

this is from bpftrace 🦋

https://github.com/bpftrace/bpftrace

also — go look in the bpftrace distribution for a companion _examples.txt file containing example usage, output, and commentary for this tool 📄✨

and for the lore: this is a bpftrace version of the bcc tool of the same name. the bcc tool provides command line options 👀

https://github.com/iovisor/bcc

🌸 OS 🌸

Linux 🐧 (of course)

💅 STABILITY 💅

Unstable — in development. she's still growing, give her grace 🙏

👑 AUTHOR 👑

Brendan Gregg — the icon, the legend, the moment ⭐

🫶 SEE ALSO 🫶

go read those too, iykyk 💖

and that's the whole page!! this was filed under USER COMMANDS, dated 2018-09-08, and it's the gethostlatency.bt(8) page in case you forgot where you were 💀 mwah, go trace some lookups bestie 🎀✨🦋

📦 where this page comes from