Performance Tools

The following tools can help you locate the code sections that you should optimize. Always remember Amdahl's Law: if 1/Kth of the program is not affected by an improvement, the best speedup you can hope for is K.

time

The unix/linux/shell time command is very useful as a crude first pass in that only user time can be improved by normal means. Real (wall clock) and system (OS processor time spent on behalf of the user) times also are reported.

perf

Linux profiling with performance counters. Really OS-level, but can be used for individual programs.

gprof

The GNU standard tool for detailed performance analysis. Best for determining which functions to optimize within a large program. Two other little things I'll demo:

• The gprof2dot tool can make a nice graph of the gprof output...
• Well, actually, that tool doesn't make a graph at all, but it reformats the data as dot input to the GraphViz tools.

Intel VTune

Intel's performance tuning software that uses the hardware performance registers. Available for both Windows and Linux, but only an evaluation period is free.

AMD uProf

AMD's original answer to Intel's VTune was CodeAnalyst, but now there's "MICRO-Prof", free for Windows and Linux.

PAPI

PAPI (Performance Application Programming Interface) provides a free and consistent interface and tools for use of performance counter hardware, primarily for a Linux environment.

Valgrind

A very nice simulation tool that tracks program behaviour using instruction-level simulation of unmodified executables using a tagged-memory system to tell you about references to uninitialized data, malloc/free activity, etc.

We'll be adding to this list later (for GPU stuff)....