Go应用程序的pprof CPU配置文件未显示任何示例

Question

I'm profiling a Go application with pprof.

The application is using about 4-10% CPU and leaving it running for a short while produces a profile of around 6-11kb. This suggests to me that it should be able to sample some activity.

When I view the result, however, I see the following:

$ go tool pprof --text bigproc
1.77s of 1.77s total (  100%)
      flat  flat%   sum%        cum   cum%
     1.77s   100%   100%      1.77s   100%
$

The interesting information appears to be missing. What could be wrong?

This is on linux, with go version 1.6.1 and pprof version 2.2.1 of google-perftools (if that matters).

Answer 1

You are mis-using the go tool pprof, because you shall specify the executable file associated with the generated profile.

Compare this

$ go tool pprof --text cpuprofile.prof
680ms of 680ms total (  100%)
      flat  flat%   sum%        cum   cum%
     680ms   100%   100%      680ms   100% 

with this (note main, that is the executable that produced the cpuprofile.prof)

$ go tool pprof --text main cpuprofile.prof
680ms of 680ms total (  100%)
      flat  flat%   sum%        cum   cum%
     350ms 51.47% 51.47%      610ms 89.71%  main.renderMandelbrotUnified
     130ms 19.12% 70.59%      130ms 19.12%  math.Log
      40ms  5.88% 76.47%       60ms  8.82%  image.(*RGBA).Set
[cut]

It's not a matter of wrong sampling: consider that around 100 samples are taken every second of execution, so even of 1.7s you should get some samples anyway (from here):

When CPU profiling is enabled, the Go program stops about 100 times per second and records a sample consisting of the program counters on the currently executing goroutine's stack