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# eprof

### MODULE

eprof

### MODULE SUMMARY

A Time Profiling Tool for Erlang

### DESCRIPTION

The module eprof provides a set of functions for time profiling of Erlang programs to find out how the execution time is used. The profiling is done using the Erlang trace BIFs. Tracing of local function calls for a specified set of processes is enabled when profiling is begun, and disabled when profiling is stopped.

When using Eprof, expect a significant slowdown in program execution, in most cases at least 100 percent.

### EXPORTS

start() -> {ok,Pid} | {error,Reason}

Types:

Pid = pid()
Reason = {already_started,Pid}

Starts the Eprof server which owns the Eprof internal database.

start_profiling(Rootset) -> profiling | error
profile(Rootset) -> profiling | error

Types:

Rootset = [atom() | pid()]

Starts profiling for the processes in Rootset (and any new processes spawned from them). Information about activity in any profiled process is stored in the Eprof database.

Rootset is a list of pids and registered names.

The function returns profiling if tracing could be enabled for all processes in Rootset, or error otherwise.

stop_profiling() -> profiling_stopped | profiling_already_stopped

Stops profiling started with start_profiling/1 or profile/1.

profile(Rootset,Fun) -> {ok,Value} | {error,Reason} | error
profile(Rootset,Module,Function,Args) -> {ok,Value} | {error,Reason} | error

Types:

Rootset = [atom() | pid()]
Fun = fun() -> term()
Module = Function = atom()
Args = [term()]
Value = Reason = term()

This function first spawns a process P which evaluates Fun() or apply(Module,Function,Args). Then, it starts profiling for P and the processes in Rootset (and any new processes spawned from them). Information about activity in any profiled process is stored in the Eprof database.

Rootset is a list of pids and registered names.

If tracing could be enabled for P and all processes in Rootset, the function returns {ok,Value} when Fun()/apply returns with the value Value, or {error,Reason} if Fun()/apply fails with exit reason Reason. Otherwise it returns error immediately.

The programmer must ensure that the function given as argument is truly synchronous and that no work continues after the function has returned a value.

analyse()

Call this function when profiling has been stopped to display the results per process, that is:

- how much time has been used by each process, and
- in which function calls this time has been spent.

Time is shown as percentage of total time, not as absolute time.

total_analyse()

Call this function when profiling has been stopped to display the results per function call, that is in which function calls the time has been spent.

Time is shown as percentage of total time, not as absolute time.

log(File) -> ok

Types:

File = atom() | string()

This function ensures that the results displayed by analyse/0 and total_analyse/0 are printed both to the file File and the screen.

stop() -> stopped

Stops the Eprof server.