Merge pull request #4590 from gmarek/client3

docs/devel/profiling.md

@@ -23,8 +23,12 @@ Even when running profiler I found not really straightforward to use 'go tool pp
 ```
   ssh kubernetes_master -L<local_port>:localhost:8080
 ```
-or analogous one for you Cloud provider. Afterwards you can e.g. run 
+or analogous one for you Cloud provider. Afterwards you can e.g. run
 ```
 go tool pprof http://localhost:<local_port>/debug/pprof/profile
 ```
 to get 30 sec. CPU profile.
+
+## Contention profiling
+
+To enable contetion profiling you need to add line ```rt.SetBlockProfileRate(1)``` in addition to ```m.mux.HandleFunc(...)``` added before (```rt``` stands for ```runtime``` in ```master.go```). This enables 'debug/pprof/block' subpage, which can be used as an input to ```go tool pprof```.