[erlang-questions] profile question

Kaiduan Xie <>
Wed Jan 28 05:00:10 CET 2009


Hi, all,

I have a question on how to find the hot spot of large base Erlang system.
For example, after running cprof.start(), cprof.pause(), cprof.analyze(), I
got the following results (only the first item is listed below),

{1847012003,
 [{io_lib_format,722457356,
                 [{{io_lib_format,pcount,2},109483111},
                  {{io_lib_format,collect,2},109483111},
                  {{io_lib_format,build,3},109483111},
                  {{io_lib_format,iolist_to_chars,1},83312743},
                  {{io_lib_format,indentation,2},60014886},
                  {{io_lib_format,field_value,2},26618934},
                  {{io_lib_format,field_value,3},17824836},
                  {{io_lib_format,precision,2},17706522},
                  {{io_lib_format,pad_char,2},17706522},
                  {{io_lib_format,field_width,3},17706522},
                  {{io_lib_format,field_width,2},17706522},
                  {{io_lib_format,decr_pc,2},17706522},
                  {{io_lib_format,control,7},17706522},
                  {{io_lib_format,collect_cseq,2},17706522},
                  {{io_lib_format,collect_cc,2},17706522},
                  {{io_lib_format,print,7},14402937},
                  {{io_lib_format,chars,2},8912422},
                  {{io_lib_format,term,5},8912417},
                  {{io_lib_format,min|...},8912416},
                  {{io_lib_format|...},8912416},
                  {{...}|...},
                  {...}|...]},

So here comes the question, how can we find which part calls
(io_lib_format,pcount,2) most? I tried to use fprof(), but it seems that you
need to know the arguments of the function first.

What is the best practice to address this problem? Or did I do something
wrong?

Thanks,

kaiduan
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