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download PDF document: pmcstat.8.pdf

PMCSTAT(8) FreeBSD System Manager's Manual PMCSTAT(8)
NAME pmcstat - performance measurement with performance monitoring hardware
SYNOPSIS pmcstat [-A] [-C] [-D pathname] [-E] [-F pathname] [-G pathname] [-I] [-L] [-M mapfilename] [-N] [-O logfilename] [-P event-spec] [-R logfilename] [-S event-spec] [-T] [-U] [-W] [-a pathname] [-c cpu-spec] [-d] [-e] [-f pluginopt] [-g] [-i lwp] [-l secs] [-m pathname] [-n rate] [-o outputfile] [-p event-spec] [-q] [-r fsroot] [-s event-spec] [-t process-spec] [-u event-spec] [-v] [-w secs] [-z graphdepth] [command [args]]
DESCRIPTION The pmcstat utility measures system performance using the facilities provided 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 executing on the system's CPUs. If a specific set of processes is being targeted (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 measurement, 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 format of pmcstat's human-readable textual output is not stable, and could change in the future. The output of sampling PMCs may be configured to go to a log file for subsequent offline analysis, or, at the expense of greater overhead, 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:
-A Skip symbol lookup and display address instead.
-C Toggle between showing cumulative or incremental counts for subsequent 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.
-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.
-I Show the offset of the instruction pointer into the symbol.
-L List all event names.
-M mapfilename Write the mapping between executable objects encountered in the event log and the abbreviated pathnames used for gprof(1) profiles to file mapfilename. If this option is not specified, mapping 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(1)-like mode for sampling PMCs. The following hotkeys can be used:
A Toggle symbol resolution Ctrl+a Switch to accumulative mode Ctrl+d Switch to delta mode f Represent the "f" cost under threshold as a dot (calltree only) I Toggle showing offsets into symbols m Merge PMCs n Change view p Show next PMC
-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 behaviour of processes in the system. It may incur substantial overhead if enabled. The default is for this feature to be disabled.
-a pathname Perform a symbol and file:line lookup for each address in each callgraph and save the output to pathname. Unlike -m that only resolves the first symbol in the graph, this resolves every node in the callgraph, or prints out addresses if no lookup information is available. This option requires the -R option to read in samples that were previously collected and saved with the -O option.
-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 available CPUs. The default is to allocate system mode PMCs on all available 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. (it has to be passed in the command line prior to -p, -s, -P, or -S).
-e Specify that the gprof profile files will use a wide history counter. These files are produced in a format compatible with gprof(1). However, other tools that cannot fully parse a BSD- style gmon header might be unable to correctly parse these files.
-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 separate profile file is generated for each executable object encountered. Profile files are placed in sub-directories named by their PMC event name.
-i lwp Filter on thread ID lwp, which you can get from ps(1) -o lwp.
-l secs Set system-wide performance measurement duration for secs seconds. The argument secs may be a fractional value.
-m pathname Print the sampled PCs with the name, the start and ending addresses of the function within they live. The pathname argument is mandatory and indicates where the information will be stored. If argument pathname is a "-" this information is sent to the output file specified by the -o option. This option
-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 integer denoting a specific process id, or a regular expression for selecting processes based on their command names.
-u event-spec Provide short description of event.
-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 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 ALSO gprof(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.
AUTHORS