Tag Archives: benchmarking

Introducing profile, super simple profiling for Go programs

This package has been superseded. Please read this blog post for more details.

Introduction

The Go runtime has built in support for several types of profiling that can be used to inspect the performance of your programs. A common way to leverage this support is via the testing package, but if you want to profile a full application it is sometimes complicated to configure the various profiling mechanisms correctly.

I wrote profile to scratch my own itch and create a simple way to profile an existing Go program without having to restructure it as a benchmark.

Installation

profile is go getable so installation is a simple as

go get github.com/davecheney/profile

Usage

Enabling profiling in your application is as simple as one line at the top of your main function

import "github.com/davecheney/profile"

func main() {
        defer profile.Start(profile.CPUProfile).Stop()
        ...
}

Options

What to profile is controlled by the *profile.Config value passed to profile.Start. A nil *profile.Config is the same as choosing all the defaults. By default no profiles are enabled.

In this more complicated example a *profile.Config is constructed by hand which enables memory profiling, but disables the shutdown hook.

import "github.com/davecheney/profile"

func main() {
        cfg := profile.Config {
                MemProfile: true,
                NoShutdownHook: true, // do not hook SIGINT
        }
        // p.Stop() must be called before the program exits to  
        // ensure profiling information is written to disk.
        p := profile.Start(&cfg)
        ...
}

Several convenience variables are provided for cpu, memory, and block (contention) profiling.

For more complex options, consult the documentation on the profile.Config type. Enabling more than one profile may cause your results to be less reliable as profiling itself is not without overhead.

Example

To show profile in action, I modified cmd/godoc following the instructions in the first example.

% godoc -http=:8080
2013/07/07 15:29:11 profile: cpu profiling enabled, /tmp/profile002803/cpu.pprof

In another window I visited http://localhost:8080 a few times to have some profiling data to record, then stopped godoc.

^C2013/07/07 15:29:33 profile: caught interrupt, stopping profiles
% go tool pprof $(which godoc) /tmp/profile002803/cpu.pprof
Welcome to pprof!  For help, type 'help'.
(pprof) top10
Total: 15 samples
       2  13.3%  13.3%        2  13.3% go/scanner.(*Scanner).next
       2  13.3%  26.7%        2  13.3% path.Clean
       1   6.7%  33.3%        3  20.0% go/scanner.(*Scanner).Scan
       1   6.7%  40.0%        1   6.7% main.hasPathPrefix
       1   6.7%  46.7%        3  20.0% main.mountedFS.translate
       1   6.7%  53.3%        1   6.7% path.Dir
       1   6.7%  60.0%        1   6.7% path/filepath.(*lazybuf).append
       1   6.7%  66.7%        1   6.7% runtime.findfunc
       1   6.7%  73.3%        2  13.3% runtime.makeslice
       1   6.7%  80.0%        2  13.3% runtime.mallocgc

Note In the example above we’re passing the godoc binary and the profile produced by running that binary to go tool pprof. When profiling your own code, you must pass your binary, and its profile to go tool pprof otherwise the profile will not make sense.

Licence

profile is available under a BSD licence.