Overview

OProfile is an open source project that includes a statistical profiler for Linux systems, capable of profiling all running code at low overhead. In version 0.9.9, an event counting tool, ocount, was added to the project. OProfile is released under the GNU GPL. It has proven stable over a large number of differing configurations; it is being used on machines ranging from laptops to 16-way NUMA-Q boxes. As always, there is no warranty.

For versions 0.9.7 and earlier, the profiler consisted of a kernel driver and a daemon for collecting sample data. In version 0.9.8, with the introduction of operf, the legacy kernel driver/daemon method of collecting sample data was deprecated in favor of profiling with the Linux Kernel Performance Events Subsystem (kernel version 2.6.31 or higher). As of version 1.0.0, the legacy profiler has been removed.

OProfile leverages the hardware performance counters of the CPU to enable profiling of a wide variety of interesting statistics, which can also be used for basic time-spent profiling. All code is profiled: hardware and software interrupt handlers, kernel modules, the kernel, shared libraries, and applications. Several post-profiling tools for turning profile data into human readable information are available.

Features

Unobtrusive

No special recompilations, wrapper libraries or the like are necessary. Even debug symbols (-g option to gcc) are not necessary unless you want to produce annotated source.
Kernel patches are usually unnecessary, except in cases where the running kernel may not yet support some newer processor models.

System-wide profiling

All code running on the system is profiled, enabling analysis of system performance. Note: Root authority is required to do system-wide profiling.

Single process profiling

Application developers will find the single process profiling feature very convenient since it does not require root authority, and profile data is collected only for the specified process (or command). This method has the added benefit of "following" fork/execs and collecting profile information on those child processes as well.

Event counting

OProfile can be used to count native hardware events occurring in either a given application, a set of processes or threads, a subset of active system processors, or the entire system.

Performance counter support

Enables collection of various low-level data, and assocation with particular sections of code.

Call-graph support

With an x86 or ARM 2.6 kernel, OProfile can provide gprof-style call-graph profiling data.

Low overhead

OProfile has a typical overhead of 1-8%, dependent on sampling frequency and workload.

Post-profile analysis

Profile data can be produced on the function-level or instruction-level detail. Source trees annotated with profile information can be created. A hit list of applications and functions that take the most time across the whole system can be produced.

System support

OProfile works across a range of CPUs, include the Intel range, AMD's Athlon and AMD64 processors range, the Alpha, ARM, IBM PowerPC, and more. OProfile will work against almost any 2.2, 2.4 and 2.6 kernels, and works on both UP and SMP systems from desktops to the scariest NUMAQ boxes. Note: As of version 0.9.8, only 2.6 kernels are supported.

Example reports

You can see what sort of output OProfile can produce with the example reports.

History

The early versions of OProfile were developed as part credit for an M.Sc. in Computer Science. The basic principles of the design were inspired by Compaq's DCPI profiler.