create a runtime CPU profile but to restrict the profile to a specific part of the program. runtime/pprof - pausing CPU profiling
To create a runtime CPU profile for a specific part of a Go program, you can use the `runtime/pprof` package. Here's how you can do it: 1. **Import the Package**: Add `import "runtime/pprof"` to your Go file. 2. **Start Profiling**: Use `pprof.StartCPUProfile(file)` to start profiling, where `file` is an `os.File` object to write the profile data. 3. **Restrict Profiling**: Place `pprof.StartCPUProfile()` before the code section you want to profile and `pprof.StopCPUProfile()` immediately after that section. 4. **Stop Profiling**: Ensure you call `defer pprof.StopCPUProfile()` to stop profiling and flush data when the function exits[2][3][4]. Citations: [1] Gperftools CPU Profiler https://gperftools.github.io/gperftools/cpuprofile.html [2] Unlocking Performance Insights: CPU Profiling in Go https://www.codingexplorations.com/blog/unlocking-performance-insights-cpu-profiling-in-go [3] Profiling Go Programs https://go.dev/blog/pprof [4] runtime/pprof - Go Packages https://pkg.go.dev/runtime/pprof [5] Runtime profiling - HPC Wiki https://hpc-wiki.info/hpc/Runtime_profiling [6] CPU Profiler — go-profiler-notes documentation - Datadog has moved https://datadoghq.dev/go-profiler-notes/profiling/cpu-profiler.html [7] Profiling Go programs with pprof - Julia Evans https://jvns.ca/blog/2017/09/24/profiling-go-with-pprof/ [8] CPU profiling in the Performance Profiler - Visual Studio (Windows) https://learn.microsoft.com/en-us/visualstudio/profiling/cpu-usage?WT.mc_id=studentamb_228125&view=vs-2022 On Tue, Nov 12, 2024, 6:07 PM Jason E. Aten <j.e.a...@gmail.com> wrote: > Idea 0: Can you just click on the graphviz boxes in the pprof http page > for your section and then just show the source for only those? > Might give you a quick idea of which are the hottest spots only > among those func of interest. > > Idea 1: Can you write a test or benchmark that just exercises the > important section? > > I suspect you could then run the profiler on your benchmark/test. > If not, it might be worth refactoring your code to allow this. > Otherwise you could write an alternative "main" as a harness that just > calls > the important section. > > Idea 2: referring to the StartCPUProfile docs: > > On Unix-like systems, StartCPUProfile does not work by default for Go > code built > > with -buildmode=c-archive or -buildmode=c-shared. StartCPUProfile relies > on the > > SIGPROF signal, but that signal will be delivered to the main program's > SIGPROF > > signal handler (if any) not to the one used by Go. To make it work, call > os/signal.Notify > > for syscall.SIGPROF, but note that doing so may break any profiling > being done by the main program. > > This makes it sounds like the SIGPROF signal is used to do the sampling. So > you might be able to manipulate it (e.g. ignore it when not in your code). > Seems like > a hack, but might be worth experimenting with. > > Idea 3: post processing. You could probably take apart the profile log > after it is > recorded and discard the samples that are irrelevant. > > Idea 4: simple manual timing. Insert time.Now() and time.Since() calls at > strategic points, and measure the improvement as you tweak your code. > > On Tuesday, November 12, 2024 at 11:16:56 AM UTC Stephen Illingworth wrote: > >> Hello, >> >> I want to create a runtime CPU profile but to restrict the profile to a >> specific part of the program. I currently have a way of taking a CPU >> profile for the entire program so have experience with the runtime/pprof >> package but this is a new requirement for me. >> >> The 'section' to be profiled represents a significant amount of code and >> I'm looking to see if any particular part of that section can be improved. >> The problem I have is that the program outside of that section is >> significantly larger (ie. larger CPU load) and dominates the profile data. >> >> The section to be profiled is entered and exited 60 times per second (at >> a minimum). >> >> In effect, I want to pause the CPU profile when execution exits the >> section and to resume when the profile enters it again. Stopping and >> restarting the profile is too slow. >> >> But maybe there's a completely different way to do this. Does anyone have >> experience with this type of thing? >> >> Regards >> Stephen >> > -- > You received this message because you are subscribed to the Google Groups > "golang-nuts" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to golang-nuts+unsubscr...@googlegroups.com. > To view this discussion visit > https://groups.google.com/d/msgid/golang-nuts/c6c0833e-a1d0-4132-87cf-c03b7f6a0ab6n%40googlegroups.com > <https://groups.google.com/d/msgid/golang-nuts/c6c0833e-a1d0-4132-87cf-c03b7f6a0ab6n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion visit https://groups.google.com/d/msgid/golang-nuts/CAKhpSosxOKFB9aNyAdUdv5_y0w5upsn9QmmGuGFffoqGcT_8nQ%40mail.gmail.com.
