Perf (Linux)
perf is a performance analyzing tool in Linux, available from Linux kernel version 2.6.31 in 2009. Userspace controlling utility, named
perf, is accessed from the command line and provides a number of subcommands; it is capable of statistical profiling of the entire system.It supports hardware performance counters, tracepoints, software performance counters, and dynamic probes. In 2012, two IBM engineers recognized perf as one of the two most commonly used performance counter profiling tools on Linux.
Implementation
The interface between the perf utility and the kernel consists of only one syscall and is done via a file descriptor and a mapped memory region. Unlike LTTng or older versions of oprofile, no service daemons are needed, as most functionality is integrated into the kernel. The perf utility dumps raw data from the mapped buffer to disk when the buffer becomes filled up. According to R. Vitillo, profiling performed by perf involves a very low overhead., architectures that provide support for hardware counters include x86, PowerPC64, UltraSPARC, ARM, Alpha EV56 and SuperH. Usage of Last Branch Records, a branch tracing implementation available in Intel CPUs since Pentium 4, is available as a patch. Since version 3.14 of the Linux kernel mainline, released on 31 March 2014, perf also supports running average power limit for power consumption measurements, which is available as a feature of certain Intel CPUs.
Perf is natively supported in many popular Linux distributions, including Red Hat Enterprise Linux and Debian in the linux-tools-common package.
Subcommands
perf is used with several subcommands:stat: measure total event count for single program or for system for some timetop: top-like dynamic view of hottest functionsrecord: measure and save sampling data for single programreport: analyze file generated by perf record; can generate flat, or graph profile.annotate: annotate sources or assemblysched: tracing/measuring of scheduler actions and latencieslist: list available events