runqlen.bt(8)

💅 NAME 💅

runqlen.bt is the tool for seeing CPU scheduler run queue length as a histogram, and it runs on bpftrace/eBPF 🔥 ✨

🎀 SYNOPSIS 🎀

runqlen.bt

🌸 DESCRIPTION 🌸

okay so this program summarizes scheduler queue length as a histogram, and it can also show you run queue occupancy 📊 It works by sampling the run queue length on all CPUs at 99 Hertz 💖

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

bestie, since this uses BPF, only the root user can use this tool. no cap 🔒

🦋 REQUIREMENTS 🦋

you'll need CONFIG_BPF and bpftrace ✨

💜 EXAMPLES 💜

Trace CPU run queue length system wide, and print a histogram when you hit Ctrl-C 🍓

# runqlen.bt

🧚 FIELDS 🧚

• 1st, 2nd — the run queue length shows up in the first field, right after the [ 🫶
• 3rd — a column with the count of samples for that length 🔢
• 4th — an ASCII histogram that draws out the count column 📈

🌈 OVERHEAD 🌈

this samples scheduler structs at 99 Hertz across all CPUs. compared to other stuff, that's a low rate of events, so the overhead of this tool is expected to be near zero 💅✨

🔥 SOURCE 🔥

this one comes straight from bpftrace 💖

https://github.com/bpftrace/bpftrace

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

this is the bpftrace version of the bcc tool with the same name ✨ the bcc tool may give you more options and customizations, so go peek at it too 👀

https://github.com/iovisor/bcc

🌷 OS 🌷

Linux 🐧

🫧 STABILITY 🫧

Unstable, since it's still in development 🙈 expect things to shift around a bit 💀

👑 AUTHOR 👑

Brendan Gregg 🫶

🦢 SEE ALSO 🦢

runqlat.bt(8), mpstat(1), pidstat(1), uptime(1) 💜

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ok that's the whole tea, bestie 🌈 this is the bpftrace-style runqlen.bt(8) page from the USER COMMANDS section, dated 2018-10-07. ily, go trace some run queues 🫶💖✨