ucalls(8) System Manager's Manual ucalls(8)
NAME
ucalls, javacalls, perlcalls, phpcalls, pythoncalls, rubycalls,
tclcalls - Summarize method calls from high-level languages and Linux
syscalls.
SYNOPSIS
javacalls [-h] [-T TOP] [-L] [-S] [-v] [-m] pid [interval]
perlcalls [-h] [-T TOP] [-L] [-S] [-v] [-m] pid [interval]
phpcalls [-h] [-T TOP] [-L] [-S] [-v] [-m] pid [interval]
pythoncalls [-h] [-T TOP] [-L] [-S] [-v] [-m] pid [interval]
rubycalls [-h] [-T TOP] [-L] [-S] [-v] [-m] pid [interval]
tclcalls [-h] [-T TOP] [-L] [-S] [-v] [-m] pid [interval]
ucalls [-l {java,perl,php,python,ruby}] [-h] [-T TOP] [-L] [-S] [-v]
[-m] pid [interval]
DESCRIPTION
This tool summarizes method calls from high-level languages such as
Java, Perl, PHP, Python, Ruby, and Tcl. It can also trace Linux system
calls. Whenever a method is invoked, ucalls records the call count and
optionally the method's execution time (latency) and displays a sum-
mary.
This uses in-kernel eBPF maps to store per process summaries for effi-
ciency.
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, method probes are not enabled by default,
and can be turned on by running the Java process with the "-XX:+Ex-
tendedDTraceProbes" flag. 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.
REQUIREMENTS
CONFIG_BPF and bcc.
OPTIONS
-l {java,perl,php,python,ruby,tcl}
The language to trace. If not provided, only syscalls are traced
(when the -S option is used).
-T TOP Print only the top methods by frequency or latency.
-L Collect method invocation latency (duration).
-S Collect Linux syscalls frequency and timing.
-v Print the resulting BPF program, for debugging purposes.
-m Print times in milliseconds (the default is microseconds).
pid The process id to trace.
interval
Print summary after this number of seconds and then exit. By de-
fault, wait for Ctrl+C to terminate.
EXAMPLES
Trace the top 10 Ruby method calls:
# ucalls -T 10 -l ruby 1344
Trace Python method calls and Linux syscalls including latency in mil-
liseconds:
# ucalls -l python -mL 2020
Trace only syscalls and print a summary after 10 seconds:
# ucalls -S 788 10
OVERHEAD
Tracing individual method calls will produce a considerable overhead in
all high-level languages. For languages with just-in-time compilation,
such as Java, the overhead can be more considerable than for inter-
preted languages. On the other hand, syscall tracing will typically be
tolerable for most processes, unless they have a very unusual rate of
system calls.
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
ustat(8), argdist(8)
USER COMMANDS 2018-10-09 ucalls(8)
Generated by dwww version 1.16 on Tue Dec 16 16:46:26 CET 2025.