Golang runtime pprof

Golang runtime pprof

golang runtime pprof

The Go program presented in that paper runs quite slowly, making it an excellent opportunity to demonstrate how to use Go's profiling tools to take a slow program and make it faster. By using Go's profiling tools to identify and correct specific bottlenecks, we can make the Go loop finding program run an order of magnitude faster and use 6x less memory.

We will not be using Java or Scala, because we are not skilled at writing efficient programs in either of those languages, so the comparison would be unfair. The programs are run on a computer with a 3. The machine is running with CPU frequency scaling disabled via.

We'll time the program using Linux's time utility with a format that shows user time, system time, real time, and maximum memory usage:. The Go program runs in These measurements are difficult to reconcile with the ones in the paper, but the point of this post is to explore how to use go tool pprofnot to reproduce the results from the paper. To start tuning the Go program, we have to enable profiling.

If the code used the Go testing package 's benchmarking support, we could use gotest's standard -cpuprofile and -memprofile flags. The new code defines a flag named cpuprofilecalls the Go flag library to parse the command line flags, and then, if the cpuprofile flag has been set on the command line, starts CPU profiling redirected to that file. 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.

After adding that code, we can run the program with the new -cpuprofile flag and then run go tool pprof to interpret the profile. The most important command is topNwhich shows the top N samples in the profile:.

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 goroutine's stack. The profile has samples, so it was running for a bit over 25 seconds.

In the go tool pprof output, there is a row for each function that appeared in a sample. The first two columns show the number of samples in which the function was running as opposed to waiting for a called function to returnas a raw count and as a percentage of total samples.

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The runtime. The top10 output is sorted by this sample count. The third column shows the running total during the listing: the first three rows account for The fourth and fifth columns show the number of samples in which the function appeared either running or waiting for a called function to return.

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The main. FindLoops function was running in In fact the total for main. FindLoops and main. DFS function was more than frames deeper than main. The stack trace samples contain more interesting data about function call relationships than the text listings can show.

The web command writes a graph of the profile data in SVG format and opens it in a web browser. There is also a gv command that writes PostScript and opens it in Ghostview. For either command, you need graphviz installed.

A small fragment of the full graph looks like:. 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.

An edge from box X to box Y indicates that X calls Y; the number along the edge is the number of times that call appears in a sample. If a call appears multiple times in a single sample, such as during recursive function calls, each appearance counts toward the edge weight. That explains the on the self-edge from main. DFS to itself. Just at a glance, we can see that the program spends much of its time in hash operations, which correspond to use of Go's map values.

We can tell web to use only samples that include a specific function, such as runtime. If we squint, we can see that the calls to runtime.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together.

Skip to content. Permalink Dismiss Join GitHub today GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Sign up. Branch: master. Find file Copy path. Cannot retrieve contributors at this time. Raw Blame History. All rights reserved. StartCPUProfile f ; err! WriteHeapProfile f ; err!

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Lock if profiles. Lock defer p.

golang runtime pprof

Unlock if p. Add panics if the profile already contains a stack for value. Unlock delete p. WritercountNamecycleName stringscaler func int64float64 int64float64records []runtime.

Countfloat64 r. Stack b. Reset fmt. Stack index [ k ] b. HasPrefix name"runtime. PCnameframe. PC - frame.

Entryframe. Fileframe. WriteTo w, 0.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together.

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Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Already on GitHub? Sign in to your account. When the same program is run in BashOnWindows this produces a cpu. If someone wants to try again with WSL2, this may work now that there's a full Linux kernel inside. Disclaimer: I don't know much about pprof, just happened to have a WSL2 instance and wanted to help.

If I'm doing something wrong or if there are more tests for me to run, I'm happy to help. Does the kernel need any specific support to enable profiling?

I can confirm that WSL2 does not support this at the moment, but they accept suggestions for additional build flags. I've got profiling working with a custom kernel.

golang runtime pprof

I got this hint through the notice on the pprof documentation which links to where the option is referenced. For anyone who is curios how to get this working on WSL WSL2 notice a missing apt within the dependency installation. I'm unable to reproduce your error messages, I built it on two machines and everything worked fine.

Profiling and Optimizing Go

I got the response from one of the maintainers that they would like to add the kernel flag. But I'm very sure this takes a few weeks to settle in the latest preview. So until it's in the official kernel the only option is to build a custom kernel. Notice that for building you need a recent ubuntu distribution like The release notes from insider build state:. Update kernel version to 4. I've tested and can confirm that the default kernel on build and later produces the right pprof profile which has samples in it.

I don't know if this resolves this issue or it should be left open cause wsl2 is in insiders only and wsl1 still has the issue.

Skip to content. Dismiss Join GitHub today GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together.

Sign up.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Already on GitHub? Sign in to your account. In a post to the mailing list someone said that Brad mentioned it briefly in a talkbut he only mentions go test -blockprofileand I'm not running tests.

Getting creative, I just thought I would dive in and try to use it:. Finally, I searched github for "pprof lookup block". This appears to show some examples of its use and reveals the function runtime. However, this function is also quite confusingly documented. SetBlockProfileRate controls the fraction of goroutine blocking events that are reported in the blocking profile. The profiler aims to sample an average of one blocking event per rate nanoseconds spent blocked. Is rate really a fraction, between 0 and 1?

If so, since it is an intit would seem my options are to either pass it 0 or 1, but the suggestion that it is a fraction seems contradictory. Is it necessary to call this function to start the profiler? Some facts which are still not clear to me, even after reading code found elsewhere:. I did eventually find Debugging performance issues in Go programswhich answers some of these questions. But unfortunately it was not easy to find for some reason. SetBlockProfileRate has two special values: 0 to disable, and 1 to catch every single event.

You can also set it to e. Nanoseconds to record one sample per second that a goroutine is blocked at a particular location.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. I have built a web server and did an ab apache benchmark test. Now I want to know the computing time of each part. Following is the results:. How can I generate this xxx. And the author used go tool pprof xxx xxx.

Anyway, the target is getting the computing time, but how? Do I have to generate this xxx. Aside from "mybin" and "myserver" you also need to substitute your port number in and remove the trailing colons after the port number. You'll then get a pprof archive created which you can explore interactively through pprof, or you can use an external tool - personally I prefer the built-in capabilities. Learn more. Golang: How to get computing time using pprof within a web server Ask Question.

Asked 4 years, 1 month ago. Active 4 years, 1 month ago. Viewed 1k times. Following is the results: pprof top10 Update Create "x. StartCPUProfile f defer pprof. StopCPUProfile but it still does not work. Many thanks.

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Wyatt Wyatt 2 2 silver badges 8 8 bronze badges.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Have a question about this project?

Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Already on GitHub? Sign in to your account. The proposal previously also gzipped the proto]. Writer error and support in the runtime, for generating profiles in serialized profile protocol buffers, rather than in the legacy pprof format. The profile proto is more extensible than the legacy pprof format and is pprof's preferred profile format.

The extensibility will be useful to support generating profiles with labels. The profile proto format is already understood by pprof itself and pprof already includes an encoder for producing serialized profile protos without requiring a dependency on the proto package or library.

I agree the runtime should generate profile. I would further propose to deprecate the legacy pprof formats. For pprof to retrieve profiles in profile.

I definitely agree that the runtime should generate profiles in the protocol buffer format. However, I don't think you need to add a new API: just replace the legacy format with the protobuf format. My understanding is that that was the idea from the start with the protobuf format.

I believe rsc even prototyped part of the runtime support just to make sure we weren't backing ourselves into a corner. I'm interested in the switch to the new format too and could participate in it, I don't want to duplicate efforts, so, could you tell, is any job done? DarKol13 I haven't started any work yet. Feel free to contribute.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Have a question about this project?

Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Already on GitHub? Sign in to your account. This issue was closed by revision de4. Labels changed: added release-noneremoved go1. Comment 14 by justin specialbusservice. Comment 16 by justin specialbusservice. Until this is fixed, can we make runtime. Certainly people running non-buggy kernels don't need to see forced output on standard error every time they profile a program.

If we had good way to tell whether the kernel patch has been applied, we could print a warning in that case. But I don't have a good way to do that.

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I have thought about changing the kernel version string but the only thing I am confident about changing is the date, and there's not much room there to signal that the fix is applied. See rsc. Pray for me while I run it! I have a report from an OS X I have also inspected the machine code for the relevant kernel function, and they did make changes roughly along the lines of what the patch has always done. So I believe it was intentionally fixed. I am hopeful that the fix will last into the final public release of OS X And then maybe years from now we can look back and laugh at how ridiculous it was that we had to apply a binary patch to our kernels to profile our programs.

On Fri, 28 Aug Russ Cox notifications github. Obsoleting in favor of Skip to content. Dismiss Join GitHub today GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Sign up. New issue.


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