cprof - mal runtime performance impact.
Please see following description for synopsis
cprof(3) Erlang Module Definition cprof(3)
NAME
cprof - A simple Call Count Profiling Tool using breakpoints for mini-
mal runtime performance impact.
DESCRIPTION
The cprof module is used to profile a program to find out how many
times different functions are called. Breakpoints similar to local call
trace, but containing a counter, are used to minimise runtime perfor-
mance impact.
Since breakpoints are used there is no need for special compilation of
any module to be profiled. For now these breakpoints can only be set on
BEAM code so BIFs cannot be call count traced.
The size of the call counters is the host machine word size. One bit is
used when pausing the counter, so the maximum counter value for a
32-bit host is 2147483647.
The profiling result is delivered as a term containing a sorted list of
entries, one per module. Each module entry contains a sorted list of
functions. The sorting order in both cases is of decreasing call count.
Call count tracing is very lightweight compared to other forms of trac-
ing since no trace message has to be generated. Some measurements indi-
cates performance degradation in the vicinity of 10 percent.
EXPORTS
analyse() ->
{AllCallCount :: integer() >= 0,
ModAnalysisList :: mod_analysis_list()}
analyse(Limit) ->
{AllCallCount :: integer() >= 0,
ModAnalysisList :: mod_analysis_list()}
analyse(Mod) -> ModAnalysis :: mod_analysis()
analyse(Mod, Limit) -> ModAnalysis :: mod_analysis()
Types:
Mod = module()
Limit = integer() >= 0
mod_analysis_list() = [mod_analysis()]
mod_analysis() =
{Mod :: module(),
ModCallCount :: integer() >= 0,
FuncAnalysisList :: func_analysis_list()}
func_analysis_list() =
[{mfa(), FuncCallCount :: integer() >= 0}]
Collects and analyses the call counters presently in the node
for either module Mod, or for all modules (except cprof itself),
and returns:
FuncAnalysisList:
A list of tuples, one for each function in a module, in
decreasing FuncCallCount order.
ModCallCount:
The sum of FuncCallCount values for all functions in module
Mod.
AllCallCount:
The sum of ModCallCount values for all modules concerned in
ModAnalysisList.
ModAnalysisList:
A list of tuples, one for each module except cprof, in
decreasing ModCallCount order.
If call counters are still running while analyse/0..2 is execut-
ing, you might get an inconsistent result. This happens if the
process executing analyse/0..2 gets scheduled out so some other
process can increment the counters that are being analysed,
Calling pause() before analysing takes care of the problem.
If the Mod argument is given, the result contains a ModAnalysis
tuple for module Mod only, otherwise the result contains one
ModAnalysis tuple for all modules returned from
code:all_loaded() except cprof itself.
All functions with a FuncCallCount lower than Limit are excluded
from FuncAnalysisList. They are still included in ModCallCount,
though. The default value for Limit is 1.
pause() -> integer() >= 0
Pause call count tracing for all functions in all modules and
stop it for all functions in modules to be loaded. This is the
same as (pause({'_','_','_'})+stop({on_load})).
See also pause/1..3 below.
pause(FuncSpec) -> integer() >= 0
pause(Mod, Func) -> integer() >= 0
pause(Mod, Func, Arity) -> integer() >= 0
Types:
Mod = module()
Func = atom()
Arity = arity()
Pause call counters for matching functions in matching modules.
The FS argument can be used to specify the first argument to
erlang:trace_pattern/3.
The call counters for all matching functions that has got call
count breakpoints are paused at their current count.
Return the number of matching functions that can have call count
breakpoints, the same as start/0..3 with the same arguments
would have returned.
restart() -> integer() >= 0
restart(FuncSpec) -> integer() >= 0
restart(Mod, Func) -> integer() >= 0
restart(Mod, Func, Arity) -> integer() >= 0
Types:
Mod = module()
Func = atom()
Arity = arity()
Restart call counters for the matching functions in matching
modules that are call count traced. The FS argument can be used
to specify the first argument to erlang:trace_pattern/3.
The call counters for all matching functions that has got call
count breakpoints are set to zero and running.
Return the number of matching functions that can have call count
breakpoints, the same as start/0..3 with the same arguments
would have returned.
start() -> integer() >= 0
Start call count tracing for all functions in all modules, and
also for all functions in modules to be loaded. This is the same
as (start({'_','_','_'})+start({on_load})).
See also start/1..3 below.
start(FuncSpec) -> integer() >= 0
start(Mod, Func) -> integer() >= 0
start(Mod, Func, Arity) -> integer() >= 0
Types:
Mod = module()
Func = atom()
Arity = arity()
Start call count tracing for matching functions in matching mod-
ules. The FS argument can be used to specify the first argument
to erlang:trace_pattern/3, for example on_load.
Set call count breakpoints on the matching functions that has no
call count breakpoints. Call counters are set to zero and run-
ning for all matching functions.
Return the number of matching functions that has got call count
breakpoints.
stop() -> integer() >= 0
Stop call count tracing for all functions in all modules, and
also for all functions in modules to be loaded. This is the same
as (stop({'_','_','_'})+stop({on_load})).
See also stop/1..3 below.
stop(FuncSpec) -> integer() >= 0
stop(Mod, Func) -> integer() >= 0
stop(Mod, Func, Arity) -> integer() >= 0
Types:
Mod = module()
Func = atom()
Arity = arity()
Stop call count tracing for matching functions in matching mod-
ules. The FS argument can be used to specify the first argument
to erlang:trace_pattern/3, for example on_load.
Remove call count breakpoints from the matching functions that
has call count breakpoints.
Return the number of matching functions that can have call count
breakpoints, the same as start/0..3 with the same arguments
would have returned.
SEE ALSO
eprof(3), fprof(3), erlang(3), User's Guide
Ericsson AB tools 3.5.2 cprof(3)