ext4dist(8)

🎀 ext4dist(8) 🎀 (System Manager's Manual)

✨ NAME ✨

okay so ext4dist is the tool that summarizes ext4 operation latency 💅 It uses Linux eBPF/bcc to do it, and it's giving precise. 🔥

💖 SYNOPSIS 💖

ext4dist [-h] [-T] [-m] [-p PID] [interval] [count]

🦋 DESCRIPTION 🦋

bestie, this tool tracks how long common ext4 file operations take 🫶 That means reads, writes, opens, and syncs. It shows the results as a power-of-2 histogram, which is so clean to look at 😭 It stores that histogram in an in-kernel eBPF map, so it stays efficient. ✨

Since this works by tracing the ext4_file_operations interface functions, it will need updating to match any changes to these functions. not me forgetting to update it 🙈

Since this uses BPF, only the root user can use this tool. 👑

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🧚 REQUIREMENTS 🧚

You'll need CONFIG_BPF and bcc. no cap, these are the must-haves 💜

🌸 OPTIONS 🌸

• -h — prints the usage message 🍓
• -T — skips the timestamps on the interval output 🦋
• -m — shows the output in milliseconds instead of microseconds 🌈
• -p PID — only traces this PID. main character energy for one process 👑

🍓 EXAMPLES 🍓

Trace the ext4 operation time, then print a summary when you hit Ctrl-C 💅

# ext4dist

Trace PID 181 only 🎀

# ext4dist -p 181

Print 1 second summaries, 10 times ✨

# ext4dist 1 10

1 second summaries, printed in milliseconds 💖

# ext4dist -m 1

💜 FIELDS 💜

• msecs — the range of milliseconds for this bucket ⏱️
• usecs — the range of microseconds for this bucket ⏱️
• count — how many operations landed in this time range 🔥
• distribution — an ASCII picture of the distribution, based on the count column 📊

🙈 OVERHEAD 🙈

⚠️ ngl this one matters: the tool adds low-overhead instrumentation to these ext4 operations, including reads and writes from the file system cache. Those reads and writes can be super frequent (it depends on the workload, eg, 1M/sec), and at that point the overhead of this tool may become noticeable. Measure and quantify before use. 💀

🌈 SOURCE 🌈

This is from bcc, bestie 🫶

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 iconic 🧚

🦋 OS 🦋

Linux 🐧

🫧 STABILITY 🫧

Unstable - in development. so expect things to shift 🙈

👑 AUTHOR 👑

Brendan Gregg 💜

⭐ SEE ALSO ⭐

Check out ext4snoop(8) next, it's the perfect bestie for this one 💅

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Okay that's the whole tea! 🫶 This page came from the USER COMMANDS crew and was last updated on 2016-02-12. Love you, mwah! 💋✨