Scalable and improved profiling of software programs

An approach to profiling software programs that uses a small pinned buffer and a large unpinned histogram buffer is presented. When a process that is being profiled receives a time slice, the process' program counter is written to the small pinned buffer by a kernel routine. The small pinned buffer is configured to be large enough to store several program counters. When the small pinned buffer is full, or almost full, an internal profiling signal is sent by the kernel routine. When the process is resumed, any outstanding signals are processed before resuming the process. The profiling signal is handled by reading the program counters from the small pinned buffer, calculating a slot in the histogram buffer that corresponds to each of the program counters, incrementing the value in the corresponding histogram slots, and clearing the small pinned buffer so that it can be reused.