runqlen(8)

🎀 runqlen(8) 🎀

System Manager's Manual 💅

✨ NAME ✨

runqlen — scheduler run queue length as a histogram 📊

💜 SYNOPSIS 💜

runqlen [-h] [-T] [-O] [-C] [interval] [count]

🌸 DESCRIPTION 🌸

okay so this program summarizes scheduler queue length as a histogram 📊, and it can also show run queue occupancy too 🔥. it works by sampling the run queue length on all CPUs at 99 Hertz ⏱️, so it's literally sampling constantly like a paparazzi 📸

this tool is perfect for spotting imbalances 👀, like when processes are bound to CPUs and causing queueing, or when interrupt mappings are causing the same mess 🙈

⚠️ since this uses BPF, only the root user can use this tool. no sneaking in as a regular user, bestie 🚫

🧚 REQUIREMENTS 🧚

you'll need CONFIG_BPF and bcc ✨

🎀 OPTIONS 🎀

• -h — prints the usage message 📝
• -T — adds timestamps to the output ⏰
• -O — reports run queue occupancy 🦋
• -C — reports for each CPU separately 🖥️
• interval — the output interval, in seconds ⏳
• count — how many outputs you want 🔢

🍓 EXAMPLES 🍓

summarize run queue length as a histogram:

# runqlen

print 1 second summaries, 10 times:

# runqlen 1 10

print output every second, with timestamps, and show each CPU separately:

# runqlen -CT 1

print run queue occupancy every second:

# runqlen -O 1

print run queue occupancy, with timestamps, for each CPU:

# runqlen -COT 1

🦋 FIELDS 🦋

• runqlen — the scheduler run queue length: the number of threads (tasks) waiting to run, (excluding including the currently running task) 🧵
• count — the number of samples at this queue length 🔢
• distribution — an ASCII bar chart visualizing the distribution (count column) 📊

🌈 OVERHEAD 🌈

this uses sampling at 99 Hertz (on all CPUs) plus in-kernel summaries, so the overhead should be basically negligible 🫶. it does not trace scheduler events the way runqlat does, and tracing is where the much higher overhead cost comes from 💀

🧁 SOURCE 🧁

this is from bcc 💖

https://github.com/iovisor/bcc

also check out the bcc distribution for a companion _examples.txt file with example usage, output, and commentary for this tool 📚

🖥️ OS 🖥️

Linux 🐧

🚧 STABILITY 🚧

🚧 Unstable — still in development, so expect some drama 🙈

👑 AUTHOR 👑

Brendan Gregg, the legend himself 🔥

🔗 SEE ALSO 🔗

runqlat(8), runqslower(8), pidstat(1) 💜

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that's the tea, bestie ☕✨ runqlen(8) from the USER COMMANDS section, last updated 2016-12-12 🧚💖