.TH ustat 8  "2016-11-07" "USER COMMANDS"
.SH NAME
ustat \- Activity stats from high-level languages.
.SH SYNOPSIS
.B ustat [-l {java,python,ruby,node,php}] [-C] [-S {cload,excp,gc,method,objnew,thread}] [-r MAXROWS] [-d] [interval [count]]
.SH DESCRIPTION
This is "top" for high-level language events, such as garbage collections,
exceptions, thread creations, object allocations, method calls, and more. The
events are aggregated for each process and printed in a top-like table, which
can be sorted by various fields.

This uses in-kernel eBPF maps to store per process summaries for efficiency.

This tool relies on USDT probes embedded in many high-level languages, such as
Node, Java, Python, Ruby, and PHP. 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, some probes are
not enabled by default, and can be turned on by running the Java process with
the "-XX:+ExtendedDTraceProbes" flag. For PHP processes, the environment
variable USE_ZEND_DTRACE must be set to 1.

Newly-created processes will only be traced at the next interval. If you run
this tool with a short interval (say, 1-5 seconds), this should be virtually
unnoticeable. For longer intervals, you might miss processes that were started
and terminated during the interval window.

Since this uses BPF, only the root user can use this tool.
.SH REQUIREMENTS
CONFIG_BPF and bcc.
.SH OPTIONS
.TP
\-l {java,python,ruby,node,php}
The language to trace. By default, all languages are traced.
.TP
\-C
Do not clear the screen between updates.
.TP
\-S {cload,excp,gc,method,objnew,thread}
Sort the output by the specified field.
.TP
\-r MAXROWS
Do not print more than this number of rows.
.TP
\-d
Print the resulting BPF program, for debugging purposes.
.TP
interval
Interval between updates, seconds.
.TP
count
Number of interval summaries.
.SH EXAMPLES
.TP
Summarize activity in high-level languages, 1 second refresh:
#
.B ustat
.TP
Don't clear the screen, and top 8 rows only:
#
.B ustat -Cr 8
.TP
5 second summaries, 10 times only:
#
.B ustat 5 10
.SH FIELDS
.TP
loadavg
The contents of /proc/loadavg
.TP
PID
Process ID.
.TP
CMDLINE
Process command line (often the second and following arguments will give you a
hint as to which application is being run.
.TP
METHOD/s
Count of method invocations during interval.
.TP
GC/s
Count of garbage collections during interval.
.TP
OBJNEW/s
Count of objects allocated during interval.
.TP
CLOAD/s
Count of classes loaded during interval.
.TP
EXC/s
Count of exceptions thrown during interval.
.TP
THR/s
Count of threads created during interval.
.SH OVERHEAD
When using this tool with high-frequency events, such as method calls, a very
significant slow-down can be expected. However, many of the high-level 
languages covered by this tool already have a fairly high per-method invocation
cost, especially when running in interpreted mode. For the lower-frequency 
events, such as garbage collections or thread creations, the overhead should 
not be significant. Specifically, when probing Java processes and not using the
"-XX:+ExtendedDTraceProbes" flag, the most expensive probes are not emitted,
and the overhead should be acceptable.
.SH SOURCE
This is from bcc.
.IP
https://github.com/iovisor/bcc
.PP
Also look in the bcc distribution for a companion _example.txt file containing
example usage, output, and commentary for this tool.
.SH OS
Linux
.SH STABILITY
Unstable - in development.
.SH AUTHOR
Sasha Goldshtein
.SH SEE ALSO
trace(8), argdist(8), tplist(8)