OProfile is a system-wide Linux profiler, capable of running at low overhead. It consists of a kernel driver and a daemon for collecting raw sample data, along with a suite of tools for parsing that data into meaningful information. OProfile is generally used by developers to determine which sections of code consume the most amount of CPU time, and why.

During a profile run, OProfile uses the processor's performance monitoring hardware. Valgrind rewrites the binary of an application, and in turn instruments it. OProfile, on the other hand,simply profiles a running application as-is. It sets up the performance monitoring hardware to take a sample every x number of events (e.g. cache misses or branch instructions). Each sample also contains information on where it occurred in the program.

OProfile's profiling methods consume less resources than Valgrind. However, OProfile requires root privileges. OProfile is useful for finding "hot-spots" in code, and looking for their causes (e.g. poor cache performance, branch mispredictions).

Using OProfile involves starting the OProfile daemon (oprofiled), running the program to be profiled, collecting the system profile data, and parsing it into a more understandable format. OProfile provides several tools for every step of this process.