operf(1)
NAME
operf - Performance profiler tool for Linux
SYNOPSIS
operf [ options ] [ --system-wide | --pid <pid> | [ command [ args ] ] ]
DESCRIPTION
Operf is the profiler tool provided with OProfile. Operf uses the Linux Performance Events Subsystem and, thus, does not require the obsolete oprofile kernel driver. By default, operf uses <current_dir>/oprofile_data as the session-dir and stores profiling data there. You can change this by way of the --session-dir option. The usual post-profiling analysis tools such as opreport(1) and opannotate(1) can be used to generate profile reports. Unless a session-dir is specified, the post-processing analysis tools will search for samples in <current_dir>/oprofile_data first. If that directory does not exist, the post-processing tools use the standard session-dir of /var/lib/oprofile. Statistics, such as total samples received and lost samples, are written to the operf.log file that can be found in the <session_dir>/samples directory.
RUN MODES
One (and only one) of the following run modes must be specified:
command[args]
The command or application to be profiled. args are the input
arguments that the command or application requires.
--pid / -p PID
This option enables operf to profile a running application. PID
should be the process ID of the process you wish to profile.
When finished profiling (e.g., when the profiled process ends),
press Ctrl-c to stop operf. If you run operf --pid as a
background job (i.e., with the &), you must stop it in a
controlled manner in order for it to process the profile data it
has collected. Use kill -SIGINT <operf-PID> for this purpose.
Limitation: When using this option to profile a multi-threaded
application that also forks new processes, be aware that samples
for processes that are forked before profiling is started may
not be recorded (depending on timing of thread creation and when
operf is started).
--system-wide / -s
This option is for performing a system-wide profile. You must
have root authority to run operf in this mode. When finished
profiling, Ctrl-c to stop operf. If you run operf --system-wide
as a background job (i.e., with the &), you must stop it in a
controlled manner in order for it to process the profile data it
has collected. Use kill -SIGINT <operf-PID> for this purpose.
It is recommended that when running operf with this option, the
user's current working directory should be /root or a
subdirectory of /root to avoid storing sample data files in
locations accessible by regular users.
OTHER OPTIONS
--vmlinux / -k vmlinux_path
A vmlinux file that matches the running kernel that has symbol
and/or debuginfo. Kernel samples will be attributed to this
binary, allowing post-processing tools (like opreport) to
attribute samples to the appropriate kernel symbols.
The kernel symbol information may be obtained from
/proc/kallsyms if the user does not specify a vmlinux file. The
symbol addresses are given in /proc/kallsyms if permitted by the
setting of /proc/sys/kernel/kptr_restrict.
If the --vmlinux option is not used and kernel symbols cannot be
obtained from /proc/kallsyms, then all kernel samples are
attributed to "no-vmlinux", which is simply a bucket to hold the
samples and not an actual file.
--events / -e event1[,event2[,...]]
This option is for passing a comma-separated list of event
specifications for profiling. Each event spec is of the form:
name:count[:unitmask[:kernel[:user]]]
The count value is used to control the sampling rate for
profiling; it is the number of events to occur between samples.
The rate is lowered by specifying a higher count value --- i.e., a
higher number of events to occur between samples.
You can specify unitmask values using either a numerical value
(hex values must begin with "0x") or a symbolic name (if the
name=<um_name> field is shown in the ophelp output). For some
named unit masks, the hex value is not unique; thus, OProfile
tools enforce specifying such unit masks value by name. If no
unit mask is specified, the default unit mask value for the
event is used.
The kernel and user parts of the event specification are binary
values ('1' or '0') indicating whether or not to collect samples
for kernel space and user space.
Note: In order to specify the kernel/user bits, you must also
specify a unitmask value, even if the processor type (or the
specified event) does not use unit masks --- in which case, use
the value '0' to signify a null unit mask; for example:
-e INST_RETIRED_ANY_P:100000:0:1:0
^ ^ ^ ^
| | | |--- '0': do not record user
space samples
| | |-- '1': record kernel space
samples
| |-- '0': the null unit mask
|--count value
Event names for some IBM PowerPC systems include a _GRP<n>
(group number) suffix. You can pass either the full event name
or the base event name (i.e., without the suffix) to operf. If
the base event name is passed, operf will automatically choose
an appropriate group number suffix for the event; thus, OProfile
post-processing tools will always show real event names that
include the group number suffix. When no event specification is
given, the default event for the running processor type will be
used for profiling. Use ophelp to list the available events for
your processor type.
--callgraph / -g
This option enables the callgraph to be saved during profiling.
NOTE: The full callchain is recorded, so there is no depth
limit.
--separate-thread / -t
This option categorizes samples by thread group ID (tgid) and
thread ID (tid). The '--separate-thread' option is useful for
seeing per-thread samples in multi-threaded applications. When
used in conjunction with the '--system-wide' option, the
'--separate-thread' option is also useful for seeing per-process
(i.e., per-thread group) samples for the case where multiple
processes are executing the same program during a profiling run.
--separate-cpu / -c
This option categorizes samples by cpu.
--session-dir / -d path
This option specifies the session path to hold the sample data.
If not specified, the data is saved in the oprofile_data
directory on the current path.
--lazy-conversion / -l
Use this option to reduce the overhead of operf during
profiling. Normally, profile data received from the kernel is
converted to OProfile format during profiling time. This is
typically not an issue when profiling a single application. But
when using the --system-wide option, this on-the-fly conversion
process can cause noticeable overhead, particularly on busy
multi-processor systems. The --lazy-conversion option directs
operf to wait until profiling is completed to do the conversion
of profile data.
Note: This option is not recommended to be used in conjunction
with the --pid option for profiling multi-threaded processes.
Depending on the order of thread creation (or forking of new
processes), you may not get any samples for the new
threads/processes.
--append / -a
By default, operf moves old profile data from
<session_dir>/samples/current to <session_dir>/samples/previous.
If a 'previous' profile already existed, it will be replaced.
If the --append option is passed, old profile data is left in
place and new profile data will be added to it, and the
'previous' profile (if one existed) will remain untouched. To
access the 'previous' profile, simply add a session
specification to the normal invocation of oprofile post-
processing tools. For example:
opreport session:previous
--verbose / -V level
A comma-separated list of debugging control values, used to
increase the verbosity of the output. Valid values are: debug,
record, convert, misc, sfile, arcs, or the special value, 'all'.
--version / -v
Show operf version.
--help / -h
Display brief usage message.
--usage / -u
Display brief usage message.
EXAMPLE
$ operf make
VERSION
This man page is current for oprofile-1.1.0.
SEE ALSO
opreport(1), opannotate(1).
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