Manual: ugc

ugc(8)						   System Manager's Manual					      ugc(8)

NAME
       ugc, javagc, nodegc, pythongc, rubygc - Trace garbage collection events in high-level languages.

SYNOPSIS
       javagc [-h] [-v] [-m] [-M MINIMUM] [-F FILTER] pid
       nodegc [-h] [-v] [-m] [-M MINIMUM] [-F FILTER] pid
       pythongc [-h] [-v] [-m] [-M MINIMUM] [-F FILTER] pid
       rubygc [-h] [-v] [-m] [-M MINIMUM] [-F FILTER] pid
       ugc [-h] [-v] [-m] [-M MINIMUM] [-F FILTER] [-l {java,node,python,ruby}] pid

DESCRIPTION
       This traces garbage collection events as they occur, including their duration and any additional information (such as
       generation collected or type of GC) provided by the respective language's runtime.

       This  tool  relies on USDT probes embedded in many high-level languages, such as Java, Node, Python, and Ruby. It re‐
       quires a runtime instrumented with these probes, which in some cases requires building from source with	a  USDT-spe‐
       cific flag, such as "--enable-dtrace" or "--with-dtrace".

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

REQUIREMENTS
       CONFIG_BPF and bcc.

OPTIONS
       -v     Print the resulting BPF program, for debugging purposes.

       -m     Print times in milliseconds. The default is microseconds.

       -M MINIMUM
	      Display  only collections that are longer than this threshold. The value is given in milliseconds. The default
	      is to display all collections.

       -F FILTER
	      Display only collections whose textual description matches (contains) this string. The default is	 to  display
	      all  collections. Note that the filtering here is performed in user-space, and not as part of the BPF program.
	      This means that if you have thousands of collection events, specifying this filter will not reduce the  amount
	      of data that has to be transferred from the BPF program to the user-space script.

       {java,node,python,ruby}
	      The language to trace.

       pid    The process id to trace.

EXAMPLES
       Trace garbage collections in a specific Node process:
	      # ugc node 148

       Trace garbage collections in a specific Java process, and print GC times in
	      milliseconds: # ugc -m java 6004

       Trace garbage collections in a specific Java process, and display them only if
	      they  are longer than 10ms and have the string "Tenured" in their detailed description: # ugc -M 10 -F Tenured
	      java 6004

FIELDS
       START  The start time of the GC, in seconds from the beginning of the trace.

       TIME   The duration of the garbage collection event.

       DESCRIPTION
	      The runtime-provided description of this garbage collection event.

OVERHEAD
       Garbage collection events, even if frequent, should not produce a considerable overhead when traced because they	 are
       still not very common. Even hundreds of GCs per second (which is a very high rate) will still produce a fairly negli‐
       gible overhead.

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
       trace(8), ustat(8), uobjnew(8)

USER COMMANDS						 2018-10-09						      ugc(8)