mutexprofile
############

仍然用2.3中的代码，只需要改两个地方，将 runtime.SetBlockProfileRate(1 * 1000 * 1000) 改为::

    // 当 rate = 0 时，关闭 mutex prof (默认值)
    // 当 rate = 1 时，表示记录所有的 mutex event
    // 当 rate > 1 时，记录 1/rate 的 mutex event(随机)
    runtime.SetMutexProfileFraction(1)

再将writeProfTo("block", "block.bprof")改为writeProfTo("mutex", "mutex.mprof")编译运行，并打开 pprof 工具::

    $ go tool pprof bin/Temp mutex.mprof
    (pprof) top
    Showing nodes accounting for 2.55ms, 100% of 2.55ms total
      flat  flat%   sum%        cum   cum%
    2.55ms   100%   100%     2.55ms   100%  sync.(*Mutex).Unlock /go/1.9.1/libexec/src/sync/mutex.go
         0     0%   100%     2.55ms   100%  main.main /go/src/ngs/test/tmp/tmp.go
         0     0%   100%     2.55ms   100%  runtime.goexit /go/1.9.1/libexec/src/runtime/asm_amd64.s
         0     0%   100%     2.55ms   100%  runtime.main /go/1.9.1/libexec/src/runtime/proc.go

查看 svg 图:

.. image:: https://img.zhaoweiguo.com/knowledge/images/languages/golangs/pprof_mutexprofile1.png