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 requires a runtime instru-
mented 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 (con-
tains) 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 thou-
sands of collection events, specifying this filter will not re-
duce 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 con-
siderable 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)
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