uobjnew(8)

💖 uobjnew(8) 💖

okay so bestie, welcome to the System Manager's Manual corner 💅 this page is all about uobjnew and its whole friend group: cobjnew, javaobjnew, rubyobjnew, and tclobjnew. Their job? Summarizing object allocations in high-level languages. iconic behavior, honestly.

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✨ NAME ✨

uobjnew, cobjnew, javaobjnew, rubyobjnew, tclobjnew — summarize object allocations in high-level languages. no cap, that's the whole vibe 🫶

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🎀 SYNOPSIS 🎀

cobjnew [-h] [-C TOP_COUNT] [-S TOP_SIZE] [-v] pid [interval]
javaobjnew [-h] [-C TOP_COUNT] [-S TOP_SIZE] [-v] pid [interval]
rubyobjnew [-h] [-C TOP_COUNT] [-S TOP_SIZE] [-v] pid [interval]
tclobjnew [-h] [-C TOP_COUNT] [-S TOP_SIZE] [-v] pid [interval]
uobjnew [-h] [-C TOP_COUNT] [-S TOP_SIZE] [-v] [-l {c,java,ruby,tcl}]
pid [interval]

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🌸 DESCRIPTION 🌸

okay so here's the tea: uobjnew traces object allocations in high-level languages — including "malloc" — and prints summaries of the most frequently allocated types, sorted by number of objects or by number of bytes. it's giving “allocation receipts” 💅

This tool relies on USDT probes embedded in many high-level languages, such as C, Java, Ruby, and Tcl. It requires a runtime instrumented with these probes, which in some cases requires building from source with a USDT-specific flag, such as --enable-dtrace or --with-dtrace. For Java, the Java process must be started with the -XX:+ExtendedDTraceProbes flag. yes bestie, that flag matters 😭

Since this uses BPF, only the root user can use this tool. root-only, no exceptions, periodt 👑

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🦋 REQUIREMENTS 🦋

vibe check: you need CONFIG_BPF and bcc. that's the entry fee ✨

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💜 OPTIONS 💜

• -C TOP_COUNT — print the top object types sorted by number of instances.
• -S TOP_SIZE — print the top object types sorted by size.
• -v — print the resulting BPF program, for debugging purposes.
• {c,java,ruby,tcl} — the language to trace.
• pid — the process id to trace.
• interval — wait this many seconds and then print the summary and exit. by default, it waits for Ctrl+C to exit.

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🌈 EXAMPLES 🌈

Trace object allocations in a Ruby process:

# uobjnew ruby 148

Trace object allocations from "malloc" and print the top 10 by total size:

# uobjnew -S 10 c 1788

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🍓 FIELDS 🍓

• TYPE — the object type being allocated. For C (malloc), this is the block size.
• ALLOCS — the number of objects allocated.
• BYTES — the number of bytes allocated.

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🔥 OVERHEAD 🔥

Object allocation events are quite frequent, and therefore the overhead from running this tool can be considerable. use with caution and make sure to test before using in a production environment, bestie — fr fr, do not just raw-dog this in prod 🙈

Nonetheless, even thousands of allocations per second will likely produce a reasonable overhead when investigating a problem. so yeah, it can still be useful, just be mindful 💀

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👑 SOURCE 👑

This is from bcc.

https://github.com/iovisor/bcc

Also look in the bcc distribution for a companion _example.txt file containing example usage, output, and commentary for this tool. it's giving bonus lore 🎀

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⭐ OS ⭐

Linux

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💅 STABILITY 💅

Unstable — in development. she's still cooking, bestie 🫶

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🌸 AUTHOR 🌸

Sasha Goldshtein

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🧚 SEE ALSO 🧚

ustat(8), ugc(8), memleak(8)

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okay bye bestie 💖 this page is filed under USER COMMANDS, dated 2018-10-09, and it's the uobjnew(8) page — slay and stay safe ✨