blockprofile
############

pprof_blockprofile.go内容:

.. literalinclude:: /files/golangs/pprof_blockprofile.go

运行程序并 pprof::

    ▶ go build -o blockprofile pprof_blockprofile.go
    ▶ go tool pprof blockprofile block.bprof
    (pprof) top
    Showing nodes accounting for 3.37ms, 100% of 3.37ms total
      flat  flat%   sum%        cum   cum%
    2.04ms 60.52% 60.52%     2.04ms 60.52%  sync.(*Mutex).Lock /go/1.9.1/libexec/src/sync/mutex.go
    1.33ms 39.48%   100%     1.33ms 39.48%  sync.(*WaitGroup).Wait /go/1.9.1/libexec/src/sync/waitgroup.go
         0     0%   100%     1.33ms 39.48%  main.main /go/src/ngs/test/tmp/tmp.go
         0     0%   100%     2.04ms 60.52%  main.worker /go/src/ngs/test/tmp/tmp.go
         0     0%   100%     3.37ms   100%  runtime.goexit /go/1.9.1/libexec/src/runtime/asm_amd64.s
         0     0%   100%     1.33ms 39.48%  runtime.main /go/1.9.1/libexec/src/runtime/proc.go

可以看到程序在 mutex.Lock 上阻塞了2.04ms(worker goroutine)， 在 WaitGroup.Wait 上等待了1.33ms(main goroutine)，从更上层来看，在 main 函数中一共阻塞了2.04ms，worker函数中阻塞了1.33ms(cum 列)，通过 web命令生成 svg 图片在浏览器查看:

.. image:: https://img.zhaoweiguo.com/knowledge/images/languages/golangs/pprof_blockprofile1.png