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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In this case, a simple solution is to introduce a cache so that each call to FindLoops reuses the previous call’s storage when possible. StartCPUProfile f defer gk. Index responds with the pprof-formatted profile named by the request. 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. 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:.

A Profile is a collection of stack traces showing the call sequences that led to instances of a particular event, such as allocation.

Profiling Go programs with pprof

I think the Samples are the most important part of the profile. Click a node to visit that function’s source code.

The top10 output is sorted by this sample count. From there you can visit its callers by clicking its declaring func token.

ForLabels invokes f with each ppprof set on the context. If we squint, we can see that the calls to runtime. The output of this is a bit long, you can view it all here: StopCPUProfile only returns after all the writes for the profile have completed.

What are locations 1 and 2? FindLoops pprof top5 -cum. Now memory allocation and the consequent garbage collection runtime.


Terms of Service Privacy Policy. For now, we are making the minimal possible changes in order to understand what is important for the performance of our program; this change is simple and mirrors the code in the Java implementation. Setting up a pprof webserver: I can also do the same thing outside interactive mode with go tool pprof -top http: A sample is a stack trace, and this stack trace has 2 locations: So the stack traces in the heap profile might be for code that is not running anymore — like maybe a function allocated a bunch of memory, returned, and a different function that should be freeing that memory is misbehaving.

Request func Trace w http. All of these kinds of profiles goroutine, heap ggo, etc are just collections of stacktraces, maybe with some metadata attached.

Profiling Go programs with pprof – Julia Evans

Similarly, the loop graph storage can be reused on each iteration instead of reallocated. There is also a gv pptof that writes PostScript and opens it in Ghostview. 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.

A large fraction of time is spent in recursive calls to DFS lineas would be expected from a recursive traversal. 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.

Functions may be omitted if they were determined to be unreachable in the particular programs or tests that were analyzed. For that particular lookup, a map is not the most efficient choice.

So I decided to gk a program that allocates a bunch of memory to profile with pprof. A label overwrites a prior label with the same key. Writer, debug int error Bugs. The final version of the Go program will use a separate LoopFinder instance to ;prof this memory, restoring the possibility of concurrent use.

String “memprofile”, “”, “write memory profile to this file” Package pprof serves via its HTTP server runtime profiling data in ppdof format expected by the pprof visualization tool. In addition to writing that function, changing the Go program to use slices instead of maps requires changing just a few lines of code.


For example, the following command runs benchmarks in the current directory and writes the CPU and memory profiles to cpu. In the call graph viewer below, each node is a function belonging to this package and its children are the functions it calls—perhaps dynamically.

pprof – The Go Programming Language

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:. A Profile is a collection of ppdof traces showing the call sequences that led to instances of a particular event, such as allocation. Context, f func key, value string bool func Label ctx context.

The debug parameter enables additional output. This basically tells us that main. SetBlockProfileRate in your program: Remove removes the execution stack associated with value from the profile. There may be non-exported or anonymous functions among them if they are called dynamically from another package.

For more information about pprof, see https: The related command disasm shows a disassembly of the function instead of a source listing; when there are enough pprpf this can help you see which instructions are expensive.

Ppdof 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. Add adds the current execution stack to the profile, associated with value. StartCPUProfile f ; err! These predefined profiles maintain themselves and panic on an explicit Add or Remove method call.