-spec clear() -> ok.

Same as clear(node()).

-spec clear(Node) -> ok when Node :: node().

Clears the internal lock statistics from the runtime system. This does not clear the data on the server only on runtime system. All counters for static locks are zeroed, all dynamic locks currently alive are zeroed and all saved locks now destroyed are removed. It also resets the duration timer.

-spec collect() -> ok.

Same as collect(node()).

-spec collect(Node) -> ok when Node :: node().

Collects lock statistics from the runtime system. The function starts a server if it is not already started. It then populates the server with lock statistics. If the server held any lock statistics data before the collect then that data is lost.

-spec conflicts() -> ok.

Same as conflicts([]).

-spec conflicts(Options) -> ok when Options :: [option()].

Prints a list of internal locks and its statistics.

For option description, see lcnt:inspect/2.

-spec information() -> ok.

Prints lcnt server state and generic information about collected lock statistics.

-spec inspect(Lock) -> ok
           when
               Lock :: Name | {Name, Id | [Id]},
               Name :: atom() | pid() | port(),
               Id :: atom() | integer() | pid() | port().

Same as inspect(Lock, []).

-spec inspect(Lock, Options) -> ok
           when
               Lock :: Name | {Name, Id | [Id]},
               Name :: atom() | pid() | port(),
               Id :: atom() | integer() | pid() | port(),
               Options :: [option()].

Prints a list of internal lock counters for a specific lock.

Lock Name and Id for ports and processes are interchangeable with the use of lcnt:swap_pid_keys/0 and is the reason why pid/0 and port/0 options can be used in both Name and Id space. Both pids and ports are special identifiers with stripped creation and can be recreated with lcnt:pid/2,3 and lcnt:port/1,2.

Option description:

• {combine, boolean()} - Combine the statistics from different instances of a lock class.
  Default: true

• {locations, boolean()} - Print the statistics by source file and line numbers.
  Default: false

• {max_locks, MaxLocks} - Maximum number of locks printed or no limit with none.
  Default: 20

• {print, PrintOptions} - Printing options:

  • name - Named lock or named set of locks (classes). The same name used for initializing the lock in the VM.

  • id - Internal id for set of locks, not always unique. This could be table name for ets tables (db_tab), port id for ports, integer identifiers for allocators, etc.

  • type - Type of lock: rw_mutex, mutex, spinlock, rw_spinlock or proclock.

  • entry - In combination with {locations, true} this option prints the lock operations source file and line number entry-points along with statistics for each entry.

  • tries - Number of acquisitions of this lock.

  • colls - Number of collisions when a thread tried to acquire this lock. This is when a trylock is EBUSY, a write try on read held rw_lock, a try read on write held rw_lock, a thread tries to lock an already locked lock. (Internal states supervises this).

  • ratio - The ratio between the number of collisions and the number of tries (acquisitions) in percentage.

  • time - Accumulated waiting time for this lock. This could be greater than actual wall clock time, it is accumulated for all threads. Trylock conflicts does not accumulate time.

  • duration - Percentage of accumulated waiting time of wall clock time. This percentage can be higher than 100% since accumulated time is from all threads.

  Default: [name,id,tries,colls,ratio,time,duration]

• {reverse, boolean()} - Reverses the order of sorting.
  Default: false

• {sort, Sort} - Column sorting orders.
  Default: time

• {thresholds, Thresholds} - Filtering thresholds. Anything values above the threshold value are passed through.
  Default: [{tries, 0}, {colls, 0}, {time, 0}]

-spec load(Filename) -> ok when Filename :: file:filename().

Restores previously saved data to the server.

-spec locations() -> ok.

Same as locations([]).

-spec locations(Options) -> ok when Options :: [option()].

Prints a list of internal lock counters by source code locations.

For option description, see lcnt:inspect/2.

-spec save(Filename) -> ok when Filename :: file:filename().

Saves the collected data to file.

-spec start() -> {ok, Pid} | {error, {already_started, Pid}} when Pid :: pid().

Starts the lock profiler server. The server only act as a medium for the user and performs filtering and printing of data collected by lcnt:collect/1.

-spec stop() -> ok.

Stops the lock profiler server.

-spec swap_pid_keys() -> ok.

Swaps places on Name and Id space for ports and processes.