lcnt

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

OTP R13B04

Types

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.

stop() -> ok

OTP R13B04

Stops the lock profiler server.

collect() -> ok

OTP R13B04

Same as collect(node()).

collect(Node) -> ok

OTP R13B04

Types

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.

clear() -> ok

OTP R13B04

Same as clear(node()).

clear(Node) -> ok

OTP R13B04

Types

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.

conflicts() -> ok

OTP R13B04

Same as conflicts([]).

conflicts([Option]) -> ok

OTP R13B04

Types

Prints a list of internal locks and its statistics.

For option description, see lcnt:inspect/2.

locations() -> ok

OTP R13B04

Same as locations([]).

locations([Option]) -> ok

OTP R13B04

Types

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

For option description, see lcnt:inspect/2.

inspect(Lock) -> ok

OTP R13B04

Same as inspect(Lock, []).

inspect(Lock, [Option]) -> ok

OTP R13B04

Types

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() and port() 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, bool()}

Combine the statistics from different instances of a lock class.
Default: true

{locations, bool()}

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, bool()}

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}]

information() -> ok

OTP R13B04

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

swap_pid_keys() -> ok

OTP R13B04

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

load(Filename) -> ok

OTP R13B04

Types

Restores previously saved data to the server.

save(Filename) -> ok

OTP R13B04

Types

Saves the collected data to file.

apply(Fun) -> term()

OTP R13B04

Types

Same as apply(Fun, []).

apply(Fun, Args) -> term()

OTP R13B04

Types

Same as apply(Module, Function, Args).

apply(Module, Function, Args) -> term()

OTP R13B04

Types

Clears the lock counters and then setups the instrumentation to save all destroyed locks. After setup the function is called, passing the elements in Args as arguments. When the function returns the statistics are immediately collected to the server. After the collection the instrumentation is returned to its previous behavior. The result of the applied function is returned.

pid(Id, Serial) -> pid()

OTP R13B04

Same as pid(node(), Id, Serial).

pid(Node, Id, Serial) -> pid()

OTP R13B04

Types

Creates a process id with creation 0.

port(Id) -> port()

OTP R13B04

Same as port(node(), Id).

port(Node, Id) -> port()

OTP R13B04

Types

Creates a port id with creation 0.

rt_collect() -> [lock_counter_data()]

OTP R13B04

Same as rt_collect(node()).

rt_collect(Node) -> [lock_counter_data()]

OTP R13B04

Types

Returns a list of raw lock counter data.

rt_clear() -> ok

OTP R13B04

Same as rt_clear(node()).

rt_clear(Node) -> ok

OTP R13B04

Types

Clear the internal counters. Same as lcnt:clear(Node).

rt_mask() -> [category_atom()]

OTP 20.1

Same as rt_mask(node()).

rt_mask(Node) -> [category_atom()]

OTP 20.1

Types

Refer to rt_mask/2 for a list of valid categories. All categories are enabled by default.

rt_mask(Categories) -> ok | {error, copy_save_enabled}

OTP 20.1

Types

Same as rt_mask(node(), Categories).

rt_mask(Node, Categories) -> ok | {error, copy_save_enabled}

OTP 20.1

Types

Sets the lock category mask to the given categories.

This will fail if the copy_save option is enabled; see lcnt:rt_opt/2.

Valid categories are:

• allocator
• db (ETS tables)
• debug
• distribution
• generic
• io
• process
• scheduler

This list is subject to change at any time, as is the category any given lock may belong to.

rt_opt({Type, bool()}) -> bool()

OTP R13B04

Same as rt_opt(node(), {Type, Opt}).

rt_opt(Node, {Type, bool()}) -> bool()

OTP R13B04

Types

Option description:

{copy_save, bool()}

Retains the statistics of destroyed locks.
Default: false

Warning

This option will use a lot of memory when enabled, which must be reclaimed with lcnt:rt_clear. Note that it makes no distinction between locks that were destroyed and locks for which counting was disabled, so enabling this option will disable changes to the lock category mask.

{process_locks, bool()}

Profile process locks, equal to adding process to the lock category mask; see lcnt:rt_mask/2
Default: true