vfsstat.bt(8)

💖 vfsstat.bt(8) ✨ System Manager's Manual ✨

🌸 NAME 🌸

okay so the name is vfsstat.bt, and it's a tool that counts key VFS calls 🔥 It uses bpftrace/eBPF, so yes, we're in the big leagues rn 💅

🎀 SYNOPSIS 🎀

vfsstat.bt

🦋 DESCRIPTION 🦋

bestie, this one traces some common VFS calls and prints per-second summaries 📊 It's super useful for general workload characterization, and for spotting patterns in how operations get used over time. main character data energy 😭

okay real talk, it works by tracing some kernel vfs functions with dynamic tracing 🔍 That also means it'll need updating whenever those functions change, so keep that in mind 🙈 If you want to customize which functions get traced, just edit the script 🛠️ And if you want something that's easier to customize for tracing multiple functions, go check out vfscount, it's giving flexibility ✨

one more thing: since this uses BPF, only the root user can run this tool 🔐 no cap, the vibe check is strict here 💀

🧚 REQUIREMENTS 🧚

you'll need CONFIG_BPF and bpftrace ✨ Make sure both are there before you try anything 💜

🍓 EXAMPLES 🍓

here's the one example, and it's so simple 🥹 Count some VFS calls and get per-second summaries until you hit Ctrl-C:

# vfsstat.bt

💅 FIELDS 💅

• HH:MM:SS — every output summary gets prefixed with the time it was printed, in "HH:MM:SS" format ⏰
• 1st — the kernel function name, shown inside @[] 🧩
• 2nd — the number of calls while tracing 🔢

🫶 OVERHEAD 🫶

okay so this one traces various kernel vfs functions and keeps in-kernel counts, which then get asynchronously copied over to user-space 🌈 The VFS op rate can be seriously high (>1M/sec) 😳 but honestly this is a pretty efficient way to trace these events, so the overhead should be small for normal workloads ✨ Still, measure it in a test environment first, bestie 🙏

🌈 SOURCE 🌈

this one comes from bpftrace 🧡

https://github.com/bpftrace/bpftrace

also, go look in the bpftrace distribution for a companion _examples.txt file. It has example usage, output, and commentary for this tool, and it's giving very helpful energy 📚

this is the bpftrace version of the bcc tool with the same name ✨ The bcc tool might offer more options and customizations, so check it out too 💫

https://github.com/iovisor/bcc

💻 OS 💻

Linux 🐧

🙈 STABILITY 🙈

okay the honest tea is that this is Unstable - in development 🚧 Use it with care, babe 🥺

👑 AUTHOR 👑

written by Brendan Gregg 🫡 the legend himself 🔥

🧸 SEE ALSO 🧸

• vfscount.bt(8) — go check this one out for more customizable tracing 🦋

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ok that's the whole tea ☕ this was vfsstat.bt(8) from USER COMMANDS, dated 2018-09-06 💖 Stay iconic, bestie 💅✨