How do you profile your code?

Question

I hope not everyone is using Rational Purify.

So what do you do when you want to measure:

• time taken by a function
• peak memory usage

Answer 1

For complex applications I am a great fan of Intel's Vtune. It is a slightly different mindset to a traditional profiler that instruments the code. It works by sampling the processor to see where instruction pointer is 1,000 times a second. It has the huge advantage of not requiring any changes to your binaries, which as often as not would change the timing of what you are trying to measure.

Unfortunately it is no good for .net or java since there isn't a way for the Vtune to map instruction pointer to symbol like there is with traditional code.

It also allows you to measure all sorts of other processor/hardware centric metrics, like clocks per instruction, cache hits/misses, TLB hits/misses, etc which let you identify why certain sections of code may be taking longer to run than you would expect just by inspecting the code.