Golang: How to get computing time using pprof within a web server

Question

I have built a web server and did an ab(apache benchmark) test. Now I want to know the computing time of each part.

I used the go tool pprof url:port/xxx and get the profile of this program, but it does not tell me the computing time(only has memory). Following is the results:

(pprof) top10
1827.59MB of 1978.12MB total (92.39%)
Dropped 175 nodes (cum <= 9.89MB)
Showing top 10 nodes out of 48 (cum >= 43.50MB)
  flat  flat%   sum%        cum   cum%
  769.54MB 38.90% 38.90%   769.54MB 38.90%  reflect.unsafe_New
  459.08MB 23.21% 62.11%   459.08MB 23.21%  services/semanticnew.TopicProbCounter.Update
  189.17MB  9.56% 71.67%  1081.21MB 54.66% github.com/golang/protobuf/proto.(*Buffer).dec_slice_struct
  122MB  6.17% 77.84%      122MB  6.17%  github.com/golang/protobuf/proto.(*Buffer).dec_int32
  107.56MB  5.44% 83.28%   107.56MB  5.44% github.com/garyburd/redigo/redis.(*conn).readReply
  68.13MB  3.44% 86.72%   527.21MB 26.65%  services/semanticnew.caculApPoiScore

  40.51MB  2.05% 88.77%    40.51MB  2.05%  runtime.malg
  28.59MB  1.45% 90.22%    28.59MB  1.45%  net/http.newBufioWriterSize
  22.50MB  1.14% 91.35%       23MB  1.16%  redismanage.(*Manager).getRequest
  20.50MB  1.04% 92.39%    43.50MB  2.20%  redismanage.(*Manager).GetRequest

In my web program, I have added the following code:

f, _ := os.Create("x.cpuprofile")
pprof.StartCPUProfile(f)
defer pprof.StopCPUProfile()

but it still does not work.

I have checked http://blog.golang.org/profiling-go-programs , but the xxx.prof file confused me. How can I generate this xxx.prof file? And the author used go tool pprof xxx xxx.prof , does it mean that xxx is the binary file which generated by xxx.go ?

Anyway, the target is getting the computing time, but how? Do I have to generate this xxx.prof file to achieve this goal?

Many thanks

Answer 1

I've had success using Dmitry's advice from here: https://software.intel.com/en-us/blogs/2014/05/10/debugging-performance-issues-in-go-programs

You merely need to import net/http/pprof, and collect profiles with:

$ go tool pprof --text mybin http://myserver:6060:/debug/pprof/profile

The net/http/pprof is imported solely for its side effects, so you can use

import (
   ...
   _ "net/http/pprof"
)

Aside from "mybin" and "myserver" you also need to substitute your port number in and remove the trailing colons after the port number. Eg for my pet project, the command is

go tool pprof http://127.0.0.1:8000/debug/pprof/profile

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.

Note that https://github.com/golang/go/issues/13841 and https://github.com/golang/go/issues/6047 are existing problems with the combination of pprof and some kernels.