vfsstat(8)

🎀 vfsstat(8) 🎀

okay so bestie, vfsstat is the tool that is literally obsessed with VFS calls 💅 it's a manual-page-level flex, so pay attention 🫶

✨ NAME ✨

vfsstat is your go-to for statistics on some common VFS calls 📊 and it runs on Linux eBPF/bcc 🧚

✨ SYNOPSIS ✨

vfsstat [interval [count]]

✨ DESCRIPTION ✨

okay so this one traces some common VFS calls and prints per-second summaries 📈 it's giving workload characterization vibes, and it's super useful for spotting patterns in how operations get used over time 👑

this works by tracing some kernel vfs functions with dynamic tracing 🔍 but heads up, it will need updating whenever those functions change 😭 if you want to customize which functions get traced, just edit the script. also check out vfscount, which is way easier to customize if you wanna trace multiple functions 🦋

🙈 Since this uses BPF, only the root user can use this tool. no cap, you need to be root or it won't work.

✨ REQUIREMENTS ✨

you'll need CONFIG_BPF and bcc 💜

✨ EXAMPLES ✨

Print summaries each second:

# vfsstat

Print output every five seconds, three times:

# vfsstat 5 3

✨ FIELDS ✨

• READ/s — the number of vfs_read() calls, as a per-second average 📖
• WRITE/s — the number of vfs_write() calls, as a per-second average ✍️
• CREATE/s — the number of vfs_create() calls, as a per-second average 🌸
• OPEN/s — the number of vfs_open() calls, as a per-second average 🚪
• FSYNC/s — the number of vfs_fsync() calls, as a per-second average 💾

✨ OVERHEAD ✨

this traces various kernel vfs functions and keeps counts in the kernel, which then get asynchronously copied to user-space 🧠 the rate of VFS operations can be super high (>1M/sec!!), but this is a relatively efficient way to trace these events, so the overhead should be small for normal workloads 🌈 still, measure in a test environment first, bestie 🫶

✨ SOURCE ✨

this one is from bcc 🍓

https://github.com/iovisor/bcc

also look in the bcc distribution for a companion _examples.txt file. it has example usage, output, and commentary for this tool, and it's honestly a treat 🎁

✨ OS ✨

Linux 🐧

✨ STABILITY ✨

Unstable - in development. so it's still cooking 🍳

✨ AUTHOR ✨

written by Brendan Gregg 👑

✨ SEE ALSO ✨

• vfscount(8) 🦋

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okay that's the whole tea ☕ this page is from the USER COMMANDS section, last updated 2015-08-18, and it's from bcc 🫶 go trace some VFS calls and slay the day, bestie 💖✨