bcc-uobjnew man page

uobjnew, cobjnew, javaobjnew, rubyobjnew, tclobjnew — Summarize object allocations in high-level languages.

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]

Description

uobjnew traces object allocations in high-level languages (including "malloc") and prints summaries of the most frequently allocated types by number of objects or number of bytes.

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.

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

Requirements

CONFIG_BPF and bcc.

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, wait for Ctrl+C to exit.

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

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.

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. Nonetheless, even thousands of allocations per second will likely produce a reasonable overhead when  investigating a problem.

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.

OS

Linux

Stability

Unstable - in development.

Author

Sasha Goldshtein

See Also

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

Referenced By

The man pages bcc-cobjnew(8), bcc-javaobjnew(8), bcc-rubyobjnew(8) and bcc-tclobjnew(8) are aliases of bcc-uobjnew(8).

2018-10-09 USER COMMANDS