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pmcstat - performance measurement with performance monitoring hardware
pmcstat - performance measurement with performance monitoring hardware
pmcstat [-C] [-D pathname] [-E] [-M mapfilename] [-O logfilename] [-P event-spec] [-R logfilename] [-S event-spec] [-W] [-c cpu-spec] [-d] [-g] [-k kerneldir] [-n rate] [-o outputfile] [-p event-spec] [-q] [-r fsroot] [-s event-spec] [-t process-spec] [-v] [-w secs] [command [args]]
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 pro‐ cess-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 pro‐ cess’ current and future children.
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. -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. -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. -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 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 CPUs. The default is to allocate system mode PMCs on all 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. -g Produce flat execution profiles in a format compatible with gprof(1). A separate profile file is generated for each exe‐ cutable object encountered. 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. -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. -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 every secs seconds. The argument secs may be a fractional value. The default inter‐ val is 5 seconds. If command is specified, it is executed using execvp(3).
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 mozilla 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 mozilla To measure processor instructions retired for all processes named “emacs” use: pmcstat -t ’^emacs$’ -p instructions 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 perform system-wide sampling on all configured processors based on processor instructions retired use: pmcstat -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 flat profiles from a sample file use: pmcstat -R /tmp/sample.out -g
The pmcstat utility exits 0 on success, and >0 if an error occurs. gprof(1), nc(1), execvp(3), pmc(3), pmclog(3), hwpmc(4), pmccontrol(8), sysctl(8)
The pmcstat utility first appeared in FreeBSD 6.0. It is currently under development.
Joseph Koshy 〈jkoshy@FreeBSD.org〉
The pmcstat utility cannot yet analyse hwpmc(4) logs generated by non- native architectures.