Mix v1.6.1 mix profile.cprof View Source
Profiles the given file or expression using Erlang’s
cprof can be useful when you want to discover the bottlenecks related
to function calls.
Before running the code, it invokes the
app.start task which compiles
and loads your project. Then the target expression is profiled, together
with all matching function calls, by setting breakpoints containing
counters. These can only be set on BEAM code so BIFs cannot be call
To profile the code, you can use syntax similar to the
mix run task:
mix profile.cprof -e Hello.world mix profile.cprof -e "[1, 2, 3] |> Enum.reverse |> Enum.map(&Integer.to_string/1)" mix profile.cprof my_script.exs arg1 arg2 arg3
--matching- only profile calls matching the given
--limit- filters out any results with a call count less than the limit
--module- filters out any results not pertaining to the given module
-c- loads the given configuration file
-e- evaluate the given code
-r- requires pattern before running the command
-p- makes all requires parallel
--no-compile- does not compile even if files require compilation
--no-deps-check- does not check dependencies
--no-archives-check- does not check archives
--no-halt- does not halt the system after running the command
--no-start- does not start applications after compilation
--no-elixir-version-check- does not check the Elixir version from mix.exs
CNT Total 15 Enum 6 <-- Enum."-map/2-lists^map/1-0-"/2 4 Enum.reverse/1 1 Enum.map/2 1 :elixir_compiler 4 <-- anonymous fn/1 in :elixir_compiler.__FILE__/1 3 anonymous fn/0 in :elixir_compiler.__FILE__/1 1 String.Chars.Integer 3 <-- String.Chars.Integer.to_string/1 3 :erlang 2 <-- :erlang.trace_pattern/3 2 Profile done over 20229 matching functions
The default output contains data gathered from all matching functions. The left
column structures each module and its total call count trace is presented on the right.
Each module has its count discriminated by function below. The
<-- symbol is meant to
help visualize where a new module call count begins.
The first row (Total) is the sum of all function calls. In the last row the number of matching functions that were considered for profiling is presented.
--matching option is specified, call count tracing will be started only for
the functions matching the given pattern:
String.Chars.Integer 3 <-- String.Chars.Integer.to_string/1 3 Profile done over 1 matching functions
The pattern can be a module name, such as
String to count all calls to that module,
a call without arity, such as
String.split, to count all calls to that function
regardless of arity, or a call with arity, such as
String.split/2, to count all
calls to that exact module, function and arity.
You should be aware the profiler is stopped as soon as the code has finished running. This may need special attention, when: running asynchronous code as function calls which were called before the profiler stopped will not be counted; running synchronous code as long running computations and a profiler without a proper MFA trace pattern or filter may lead to a result set which is difficult to comprehend.
Other caveats are the impossibility to call count trace BIFs, since breakpoints can
only be set on BEAM code; functions calls performed by
:cprof are not traced; the
maximum size of a call counter is equal to the host machine’s word size
(for example, 2147483647 in a 32-bit host).