biostacks.bt(8)

✨ biostacks.bt(8) — NAME ✨

biostacks 💅 — shows disk I/O latency alongside the initialization stacks that kicked it off. Uses bpftrace/eBPF. 🔥

🎀 SYNOPSIS 🎀

biostacks

💖 DESCRIPTION 💖

okay so bestie, this tool shows disk I/O latency histograms for each block I/O initialization path 📊 and this is lowkey the best part, because it can help reveal why latencies are different 😭 some get created by log flushing, others by application reads, etc. main character energy 👑

this works by attaching to block_io_start and block_rq_issue tracepoints 🧚

and since this uses BPF, ONLY the root user can use this tool 💀 not me being locked out 🙈

🌸 REQUIREMENTS 🌸

you need CONFIG_BPF and bpftrace, periodt ✨

🍓 EXAMPLES 🍓

Trace disk I/O latency with initialization stacks:

# biostacks.bt

🦋 FIELDS 🦋

• 0th — this is the initialization kernel stack trace (shown as @[...]) that gets printed before each I/O histogram 🧵
• 1st, 2nd — the range of I/O latency, in microseconds (shown in [...) set notation) 📏
• 3rd — a column showing the count of I/O in that range 🔢
• 4th — an ASCII histogram representing the count column 📈

🫶 OVERHEAD 🫶

the rate of biostacks should be low (bounded by device IOPS), so the overhead of this tool is expected to be negligible 🥰 no cap

🌈 SOURCE 🌈

this tool originated from the book "BPF Performance Tools", published by Addison Wesley (2019) 📚

http://www.brendangregg.com/bpf-performance-tools-book.html

go see the book for more documentation on this tool, iykyk 💜

this version lives in the bpftrace repository:

https://github.com/bpftrace/bpftrace

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

🧚 OS 🧚

Linux 🐧

🙈 STABILITY 🙈

Unstable - in development. ⚠️ it's still cooking, so be gentle 🍳

👑 AUTHOR 👑

Brendan Gregg, the icon 🫡

💅 SEE ALSO 💅

• biosnoop.bt(8) — the sibling tool you should check out next 🦋

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biostacks.bt from USER COMMANDS, dated 2019-07-12 🎀 slay the disk, bestie, I'll see you next time 💖✨