The developer docs: ; The output of go tool pprof –help (I pasted the output on my. Step #5: run go tool pprof. Pass your binary location, and the location of the cpu. pprof file as returned when running your program. You can. To build and install it, use the go get tool. go get -u Remember to set GOPATH to the directory where you want pprof to be installed.

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Functions may be omitted if they were determined to be unreachable in the particular programs or tests that were analyzed. Add 1 go leakyFunction wg wg. So I decided to write a program that allocates a bunch of memory to profile with pprof.

Since we already know that the time is going into map lookups implemented by the hash runtime functions, we care most about the second column. This puts us into an interactive mode where we run top.

Profiling Go Programs – The Go Blog

One way is to add memory profiling to the program. What are locations 1 and 2? The CPU profile is not available as a Profile. See the diff between havlak1 and havlak2.

I was originally confused about ppro works — the profiles have already be collected! Instead of using a map, we can use a simple slice to list the elements. Each box in the graph corresponds to a single function, and the boxes are sized according to the number of samples in which the function was running.

Just as they would be in a compiler, the basic block structures have unique sequence numbers assigned to them. Excluding the recursion, it looks like the time is going into the accesses to the prof map on lines, and Just at a glance, we can see that the program spends much of its time in hash operations, which correspond to use of Toool map values.


Init currentNode, current 1 37 String “memprofile”, “”, “write memory profile to this file” Add adds the current execution stack to the profile, associated with value. Changing number from a map to a slice requires editing seven lines in the program and cut its run time by nearly a factor of two:.

For example Go 1. For more information about pprof, see https: The profiler requires a final call to StopCPUProfile to flush any pending writes to the file before the program exits; we use defer to make sure this happens as main returns.

Profiling Go programs with pprof

Context, key string string, bool func SetGoroutineLabels ctx context. StartCPUProfile f ; err! Request func Symbol w http. From there you can visit its callers by clicking its declaring func token.

You can read the source for the memory profiler here: It’s hard to tell what’s going on in that graph, because there are many nodes with small sample numbers obscuring the big ones.

There are many commands available from the pprof command line. SetMutexProfileFraction in your program: We can follow the thick arrows easily now, to see that FindLoops is triggering most of the garbage collection.

Profiling Go programs with pprof – Julia Evans

Now that we have a rough idea of the big picture, it’s time to zoom in on a particular function. Terms of Service Privacy Policy. Profiling lasts for duration specified in seconds GET parameter, or for 30 seconds if not specified. The programs are run on a computer with a 3.


When CPU profiling is enabled, the Go program stops about times per second and records a sample consisting of the program counters on the currently executing ppgof stack. The related command disasm shows a disassembly of the function instead of a source listing; when there are enough samples this can help you see which instructions are expensive. There may be non-exported or anonymous functions among them if they are called dynamically from another package.

Tracing lasts for duration specified in gk GET parameter, or for 1 second if not specified. Package pprof serves via its HTTP server runtime profiling data in the format expected by the pprof visualization tool.

Context, labels LabelSet, f func context. Use “help” for information on all pprof commands. WriteHeapProfile is shorthand for Lookup “heap”.

The profile has samples, so it was running for a bit over 25 seconds. Profiles can then be visualized with the pprof tool: Do calls f with a copy of the parent context with the given labels added to the parent’s label map. It is preserved for backwards compatibility.

All of these kinds of profiles goroutine, heap allocations, etc are just collections of stacktraces, maybe with some metadata attached. Benchmarks are only as good as the programs they measure. Caller’s skip and controls where the stack trace begins.