bcc-uflow man page

uflow, javaflow, perlflow, phpflow, pythonflow, rubyflow, tclflow — Print a flow graph of method calls in high-level languages.


javaflow [-h] [-M METHOD] [-C CLAZZ] [-v] pid
perlflow [-h] [-M METHOD] [-C CLAZZ] [-v] pid
phpflow [-h] [-M METHOD] [-C CLAZZ] [-v] pid
pythonflow [-h] [-M METHOD] [-C CLAZZ] [-v] pid
rubyflow [-h] [-M METHOD] [-C CLAZZ] [-v] pid
tclflow [-h] [-M METHOD] [-C CLAZZ] [-v] pid
uflow [-h] [-M METHOD] [-C CLAZZ] [-v] [-l {java,perl,php,python,ruby,tcl}] pid


uflow traces method calls and prints them in a flow graph that can facilitate debugging and diagnostics by following the program's execution (method flow).

This tool relies on USDT probes embedded in many high-level languages, such as Java, Perl, PHP, Python, 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 processes, the startup flag "-XX:+ExtendedDTraceProbes" is required. For PHP processes, the environment variable USE_ZEND_DTRACE must be set to 1.

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


CONFIG_BPF and bcc.



Print only method calls where the method name begins with this string.


Print only method calls where the class name begins with this string. The class name interpretation strongly depends on the language. For example, in Java use "package/subpackage/ClassName" to refer to classes.


Print the resulting BPF program, for debugging purposes.


The language to trace.


The process id to trace.


Follow method flow in a Ruby process:

# uflow ruby 148

Follow method flow in a Java process where the class name is java.lang.Thread:

# uflow -C java/lang/Thread java 1802



The CPU number on which the method was invoked. This is useful to easily see where the output skips to a different CPU.


The process id.


The thread id.


The duration of the method call.


The method name.


This tool has extremely high overhead because it prints every method call. For some scenarios, you might see lost samples in the output as the tool is unable to keep up with the rate of data coming from the kernel. Filtering by class  or method prefix can help reduce the amount of data printed, but there is still a very high overhead in the collection mechanism. Do not use for performance- sensitive production scenarios, and always test first.


This is from bcc.


Also look in the bcc distribution for a companion _example.txt file containing example usage, output, and commentary for this tool.




Unstable - in development.


Sasha Goldshtein

See Also

trace(8), ustat(8)

Referenced By

The man pages bcc-javaflow(8), bcc-perlflow(8), bcc-phpflow(8), bcc-pythonflow(8), bcc-rubyflow(8) and bcc-tclflow(8) are aliases of bcc-uflow(8).

2018-10-09 USER COMMANDS