| Author: | Andreas Rumpf |
|---|---|
| Version: | 1.6.0 |
Nim comes with a platform independent profiler - the Embedded Stack Trace Profiler (ESTP). The profiler is embedded into your executable. To activate the profiler you need to do:
You can in fact look at nimprof's source code to see how to implement your own profiler.
The setting --profiler:on defines the conditional symbol profiler. You can use when compileOption("profiler") to make the switch seamless. If profiler is off, your program runs normally. Otherwise your program is profiled.
when compileOption("profiler"): import nimprof
After your program has finished the profiler will create a file profile_results.txt containing the profiling results.
Since the profiler works by examining stack traces, it's essential that the option --stackTrace:on is active! Unfortunately this means that a profiling build is much slower than a release build.
You can also use ESTP as a memory profiler to see which stack traces allocate the most memory and thus create the most GC pressure. It may also help to find memory leaks. To activate the memory profiler you need to do:
Define the symbol ignoreAllocationSize so that only the number of allocations is counted and the sizes of the memory allocations do not matter.
The results file lists stack traces ordered by significance.
The following example file has been generated by profiling the Nim compiler itself: It shows that in total 5.4% of the runtime has been spent in crcFromRope or its children.
In general the stack traces show you immediately where the problem is because the trace acts like an explanation; in traditional profilers you can only find expensive leaf functions easily but the reason why they are invoked often remains mysterious.
total executions of each stack trace: Entry: 0/3391 Calls: 84/4160 = 2.0% [sum: 84; 84/4160 = 2.0%] newCrcFromRopeAux crcFromRope writeRopeIfNotEqual shouldRecompile writeModule myClose closePasses processModule CompileModule CompileProject CommandCompileToC MainCommand HandleCmdLine nim Entry: 1/3391 Calls: 46/4160 = 1.1% [sum: 130; 130/4160 = 3.1%] updateCrc32 newCrcFromRopeAux crcFromRope writeRopeIfNotEqual shouldRecompile writeModule myClose closePasses processModule CompileModule CompileProject CommandCompileToC MainCommand HandleCmdLine nim Entry: 2/3391 Calls: 41/4160 = 0.99% [sum: 171; 171/4160 = 4.1%] updateCrc32 updateCrc32 newCrcFromRopeAux crcFromRope writeRopeIfNotEqual shouldRecompile writeModule myClose closePasses processModule CompileModule CompileProject CommandCompileToC MainCommand HandleCmdLine nim Entry: 3/3391 Calls: 41/4160 = 0.99% [sum: 212; 212/4160 = 5.1%] crcFromFile writeRopeIfNotEqual shouldRecompile writeModule myClose closePasses processModule CompileModule CompileProject CommandCompileToC MainCommand HandleCmdLine nim Entry: 4/3391 Calls: 41/4160 = 0.99% [sum: 253; 253/4160 = 6.1%] updateCrc32 crcFromFile writeRopeIfNotEqual shouldRecompile writeModule myClose closePasses processModule CompileModule CompileProject CommandCompileToC MainCommand HandleCmdLine nim Entry: 5/3391 Calls: 32/4160 = 0.77% [sum: 285; 285/4160 = 6.9%] pop newCrcFromRopeAux crcFromRope writeRopeIfNotEqual shouldRecompile writeModule myClose closePasses processModule CompileModule CompileProject CommandCompileToC MainCommand HandleCmdLine nim Entry: 6/3391 Calls: 17/4160 = 0.41% [sum: 302; 302/4160 = 7.3%] doOperation forAllChildrenAux pop newCrcFromRopeAux crcFromRope writeRopeIfNotEqual shouldRecompile writeModule myClose closePasses processModule CompileModule CompileProject CommandCompileToC MainCommand HandleCmdLine ... nim Entry: 7/3391 Calls: 14/4160 = 0.34% [sum: 316; 316/4160 = 7.6%] Contains isAccessible interiorAllocatedPtr gcMark markStackAndRegisters collectCTBody collectCT rawNewObj newObj newNode copyTree matchesAux matches resolveOverloads semOverloadedCall semOverloadedCallAnalyseEffects ... CommandCompileToC MainCommand HandleCmdLine