Perf (Linux)
perf (sometimes called perf_events or perf tools, originally Performance Counters for Linux, PCL) 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 (both kernel and userland code).