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NAME | SYNOPSIS | DESCRIPTION | RUN MODES | OTHER OPTIONS | EXAMPLE | VERSION | SEE ALSO | COLOPHON |
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ocount(1) General Commands Manual ocount(1)
ocount - Event counting tool for Linux
ocount [ options ] [ --system-wide | --process-list <pids> |
--thread-list <tids> | --cpu-list <cpus> | [ command [ args ] ] ]
ocount is an OProfile tool that can be used to count native
hardware events occurring in either a given application, a set of
processes or threads, a subset of active system processors, or the
entire system. The data collected during a counting session is
displayed to stdout by default or, optionally, to a file.
When counting multiple events, the kernel may not be able to count
all events simultaneously and, thus, may need to multiplex the
counting of the events. If this happens, the "Percent time
enabled" column in the ocount output will be less than 100, but
counts are scaled up to a 100% estimated value.
One (and only one) of the following run modes must be specified.
If you run ocount using a run mode other than command [args] ,
press Ctrl-c to stop ocount when finished counting (e.g., when the
monitored process ends). If you background ocount (i.e., with
'&') while using one these run modes, you must stop it in a
controlled manner so that the data collection process can be shut
down cleanly and final results can be displayed. Use kill -SIGINT
<ocount-PID> for this purpose.
command [args]
The command is the application for which to count events.
args are the input arguments required by the application.
The command and its arguments must be positioned at the end
of the command line, after all ocount options.
--process-list / -p pids
Use this option to count events for one or more already-
running applications, specified via a comma-separated list
( pids ). Event counts will be collected for all children
of the passed process(es) as well. You must have privileges
for the user ID under which the specified process(es) are
running; e.g., for a non-root user, the user ID of the
process(es) is the same as that used for running ocount. A
lack of privileges will result in the following failure
message:
perf_event_open failed with Permission denied
--thread-list / -r tids
Use this option to count events for one or more already-
running threads, specified via a comma-separated list (
tids ). Event counts will not be collected for any children
of the passed thread(s). See the description of --process-
list concerning required privileges.
--system-wide / -s
This option is for counting events for all processes
running on your system. You must have root authority to
run ocount in this mode.
--cpu-list / -C cpus
This option is for counting events on a subset of
processors on your system. You must have root authority to
run ocount in this mode. This is a comma-separated list,
where each element in the list may be either a single
processor number or a range of processor numbers; for
example: '-C 2,3,4-11,15'.
--events / -e event1[,event2[,...]]
This option is for passing a comma-separated list of event
specifications for counting. Each event spec is of the
form:
name[:unitmask[:kernel[:user]]]
Note: Do not include a count value in the event spec, as
that parameter is only needed when profiling.
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
count events in kernel space and user space.
Note: In order to specify the kernel/user bits, you must
also specify a unitmask value, even if the running
processor type 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:0:1:0
^ ^ ^
| | |--- '0': do not count user
space events
| |-- '1': count kernel space
events
|-- '0': the null unit mask
Event names for certain processor types include a _GRP<n>
suffix. For such cases, the --events option may be
specified with or without the _GRP<n> suffix.
When no event specification is given, the default event for
the running processor type will be used for counting. Use
ophelp to list the available events for your processor
type.
--separate-thread / -t
This option can be used in conjunction with either the
--process-list or --thread-list option to display event
counts on a per-thread (per-process) basis. Without this
option, all counts are aggregated.
NOTE: If new threads are started by the process(es) being
monitored after counting begins, the counts for those
threads are aggregated with their parent's counts.
--separate-cpu / -c
This option can be used in conjunction with either the
--system-wide or --cpu-list option to display event counts
on a per-cpu basis. Without this option, all counts are
aggregated.
--time-interval / -i interval_length[:num_intervals]
Note: The interval_length is given in milliseconds.
However, the current implementation only supports 100 ms
granularity, so the given interval_length will be rounded
to the nearest 100 ms. Results collected for each time
interval are printed immediately instead of the default of
one dump of cumulative event counts at the end of the run.
Counters are reset to zero at the start of each interval.
If num_intervals is specified, ocount exits after the
specified number of intervals occur.
--brief-format / -b
Use this option to print results in the following brief
format:
[cpu or
thread,]<event_name>[:umask[:K:U]],<count>,<percent_time_enabled>
[ <u32> ,]< string >[< u32>[<bb>]],< u64 >,<
double >
The umask, Kernel and User modes are only printed if the
values were specified as part of the event. The 'K' and
'U' fields are binary fields separated by colons, where the
value for each binary field may be either '0' or '1'.
If --timer-interval is specified, a separate line formatted
as
timestamp,<num_seconds_since_epoch>[.n]
is printed ahead of each dump of event counts. If the time
interval specified is less than one second, the timestamp
will have 1/10 second precision.
--output-file / -f outfile_name
Results are written to outfile_name instead of
interactively to the terminal.
--verbose / -V
Use this option to increase the verbosity of the output.
--version / -v
Show ocount version.
--help / -h
Display brief usage message.
--usage / -u
Display brief usage message.
$ ocount make
This man page is current for oprofile-1.5.0git.
operf(1).
This page is part of the oprofile (a system-wide profiler for
Linux) project. Information about the project can be found at
⟨http://oprofile.sourceforge.net/news/⟩. If you have a bug report
for this manual page, see ⟨http://oprofile.sourceforge.net/bugs/⟩.
This page was obtained from the project's upstream Git repository
⟨git://git.code.sf.net/p/oprofile/oprofile⟩ on 2025-08-11. (At
that time, the date of the most recent commit that was found in
the repository was 2024-12-10.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
oprofile 1.5.0git Mon 11 August 2025 ocount(1)
Pages that refer to this page: oprofile(1)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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