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  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".

       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 negligible 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)