PMCSTAT(8) BSD System Manager's Manual PMCSTAT(8)NAMEpmcstat — performance measurement with performance monitoring hardware
SYNOPSISpmcstat [-C] [-D pathname] [-E] [-F pathname] [-G pathname]
[-M mapfilename] [-N] [-O logfilename] [-P event-spec]
[-R logfilename] [-S event-spec] [-T] [-W] [-c cpu-spec] [-d]
[-f pluginopt] [-g] [-k kerneldir] [-m pathname] [-n rate]
[-o outputfile] [-p event-spec] [-q] [-r fsroot] [-s event-spec]
[-t process-spec] [-v] [-w secs] [-z graphdepth] [command [args]]
DESCRIPTION
The pmcstat utility measures system performance using the facilities pro‐
vided by hwpmc(4).
The pmcstat utility can measure both hardware events seen by the system
as a whole, and those seen when a specified set of processes are execut‐
ing on the system's CPUs. If a specific set of processes is being tar‐
geted (for example, if the -t process-spec option is specified, or if a
command line is specified using command), then measurement occurs till
command exits, or till all target processes specified by the -t
process-spec options exit, or till the pmcstat utility is interrupted by
the user. If a specific set of processes is not targeted for measure‐
ment, then pmcstat will perform system-wide measurements till interrupted
by the user.
A given invocation of pmcstat can mix allocations of system-mode and
process-mode PMCs, of both counting and sampling flavors. The values of
all counting PMCs are printed in human readable form at regular intervals
by pmcstat. The output of sampling PMCs may be configured to go to a log
file for subsequent offline analysis, or, at the expense of greater over‐
head, may be configured to be printed in text form on the fly.
Hardware events to measure are specified to pmcstat using event specifier
strings event-spec. The syntax of these event specifiers is machine
dependent and is documented in pmc(3).
A process-mode PMC may be configured to be inheritable by the target
process' current and future children.
OPTIONS
The following options are available:
-C Toggle between showing cumulative or incremental counts for sub‐
sequent counting mode PMCs specified on the command line. The
default is to show incremental counts.
-D pathname
Create files with per-program samples in the directory named by
pathname. The default is to create these files in the current
directory.
-E Toggle showing per-process counts at the time a tracked process
exits for subsequent process-mode PMCs specified on the command
line. This option is useful for mapping the performance charac‐
teristics of a complex pipeline of processes when used in con‐
junction with the -d option. The default is to not to enable
per-process tracking.
-F pathname
Print calltree (Kcachegrind) information to file pathname. If
argument pathname is a “-” this information is sent to the output
file specified by the -o option.
-G pathname
Print callchain information to file pathname. If argument
pathname is a “-” this information is sent to the output file
specified by the -o option.
-M mapfilename
Write the mapping between executable objects encountered in the
event log and the abbreviated pathnames used for gprof(1) pro‐
files to file mapfilename. If this option is not specified, map‐
ping information is not written. Argument mapfilename may be a
“-” in which case this mapping information is sent to the output
file configured by the -o option.
-N Toggle capturing callchain information for subsequent sampling
PMCs. The default is for sampling PMCs to capture callchain
information.
-O logfilename
Send logging output to file logfilename. If logfilename is of
the form hostname:port, where hostname does not start with a ‘.’
or a ‘/’, then pmcstat will open a network socket to host
hostname on port port.
If the -O option is not specified and one of the logging options
is requested, then pmcstat will print a textual form of the
logged events to the configured output file.
-P event-spec
Allocate a process mode sampling PMC measuring hardware events
specified in event-spec.
-R logfilename
Perform offline analysis using sampling data in file logfilename.
-S event-spec
Allocate a system mode sampling PMC measuring hardware events
specified in event-spec.
-T Use a top like mode for sampling PMCs. The following hotkeys can
be used: 'c+a' switch to accumulative mode, 'c+d' switch to delta
mode, 'm' merge PMCs, 'n' change view, 'p' show next PMC, ' '
pause, 'q' quit. calltree only: 'f' cost under threshold is seen
as a dot.
-W Toggle logging the incremental counts seen by the threads of a
tracked process each time they are scheduled on a CPU. This is
an experimental feature intended to help analyse the dynamic be‐
haviour of processes in the system. It may incur substantial
overhead if enabled. The default is for this feature to be dis‐
abled.
-c cpu-spec
Set the cpus for subsequent system mode PMCs specified on the
command line to cpu-spec. Argument cpu-spec is a comma separated
list of CPU numbers, or the literal ‘*’ denoting all unhalted
CPUs. The default is to allocate system mode PMCs on all
unhalted CPUs.
-d Toggle between process mode PMCs measuring events for the target
process' current and future children or only measuring events for
the target process. The default is to measure events for the
target process alone.
-f pluginopt
Pass option string to the active plugin.
threshold=<float> do not display cost under specified value
(Top).
skiplink=0|1 replace node with cost under threshold by a dot
(Top).
-g Produce profiles in a format compatible with gprof(1). A sepa‐
rate profile file is generated for each executable object encoun‐
tered. Profile files are placed in sub-directories named by
their PMC event name.
-k kerneldir
Set the pathname of the kernel directory to argument kerneldir.
This directory specifies where pmcstat should look for the kernel
and its modules. The default is /boot/kernel.
-m pathname
Print the sampled PCs with the name, the start and ending
addresses of the function within they live. The pathname argu‐
ment is mandatory and indicates where informations will be
stored. If argument pathname is a “-” this information is sent
to the output file specified by the -o option.
-n rate
Set the default sampling rate for subsequent sampling mode PMCs
specified on the command line. The default is to configure PMCs
to sample the CPU's instruction pointer every 65536 events.
-o outputfile
Send counter readings and textual representations of logged data
to file outputfile. The default is to send output to stderr when
collecting live data and to stdout when processing a pre-existing
logfile.
-p event-spec
Allocate a process mode counting PMC measuring hardware events
specified in event-spec.
-q Decrease verbosity.
-r fsroot
Set the top of the filesystem hierarchy under which executables
are located to argument fsroot. The default is /.
-s event-spec
Allocate a system mode counting PMC measuring hardware events
specified in event-spec.
-t process-spec
Attach process mode PMCs to the processes named by argument
process-spec. Argument process-spec may be a non-negative inte‐
ger denoting a specific process id, or a regular expression for
selecting processes based on their command names.
-v Increase verbosity.
-w secs
Print the values of all counting mode PMCs or sampling mode PMCs
for top mode every secs seconds. The argument secs may be a
fractional value. The default interval is 5 seconds.
-z graphdepth
When printing system-wide callgraphs, limit callgraphs to the
depth specified by argument graphdepth.
If command is specified, it is executed using execvp(3).
EXAMPLES
To perform system-wide statistical sampling on an AMD Athlon CPU with
samples taken every 32768 instruction retirals and data being sampled to
file sample.stat, use:
pmcstat-O sample.stat -n 32768 -S k7-retired-instructions
To execute firefox and measure the number of data cache misses suffered
by it and its children every 12 seconds on an AMD Athlon, use:
pmcstat-d -w 12 -p k7-dc-misses firefox
To measure instructions retired for all processes named “emacs” use:
pmcstat-t '^emacs$' -p instructions
To measure instructions retired for processes named “emacs” for a period
of 10 seconds use:
pmcstat-t '^emacs$' -p instructions sleep 10
To count instruction tlb-misses on CPUs 0 and 2 on a Intel Pentium
Pro/Pentium III SMP system use:
pmcstat-c 0,2 -s p6-itlb-miss
To collect profiling information for a specific process with pid 1234
based on instruction cache misses seen by it use:
pmcstat-P ic-misses -t 1234 -O /tmp/sample.out
To perform system-wide sampling on all configured processors based on
processor instructions retired use:
pmcstat-S instructions -O /tmp/sample.out
If callgraph capture is not desired use:
pmcstat-N -S instructions -O /tmp/sample.out
To send the generated event log to a remote machine use:
pmcstat-S instructions -O remotehost:port
On the remote machine, the sample log can be collected using nc(1):
nc -l remotehost port > /tmp/sample.out
To generate gprof(1) compatible profiles from a sample file use:
pmcstat-R /tmp/sample.out -g
To print a system-wide profile with callgraphs to file foo.graph use:
pmcstat-R /tmp/sample.out -G foo.graph
DIAGNOSTICS
If option -v is specified, pmcstat may issue the following diagnostic
messages:
#callchain/dubious-frames The number of callchain records that had an
“impossible” value for a return address.
#exec handling errors The number of exec(2) events in the log file that
named executables that could not be analyzed.
#exec/elf The number of exec(2) events that named ELF executables.
#exec/unknown The number of exec(2) events that named executables with
unrecognized formats.
#samples/total The total number of samples in the log file.
#samples/unclaimed The number of samples that could not be correlated to
a known executable object (i.e., to an executable, shared library, the
kernel or the runtime loader).
#samples/unknown-object The number of samples that were associated with
an executable with an unrecognized object format.
The pmcstat utility exits 0 on success, and >0 if an error occurs.
COMPATIBILITY
Due to the limitations of the gmon.out file format, gprof(1) compatible
profiles generated by the -g option do not contain information about
calls that cross executable boundaries. The generated gmon.out files are
also only meaningful for native executables.
SEE ALSOgprof(1), nc(1), execvp(3), pmc(3), pmclog(3), hwpmc(4), pmccontrol(8),
sysctl(8)HISTORY
The pmcstat utility first appeared in FreeBSD 6.0. It is currently under
development.
AUTHORS
Joseph Koshy ⟨jkoshy@FreeBSD.org⟩
BUGS
The pmcstat utility cannot yet analyse hwpmc(4) logs generated by non-
native architectures.
BSD September 19, 2008 BSD
