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spawn/1/2/3/4

结构:

spawn(Fun) -> pid()
spawn(Node, Fun) -> pid()
spawn(Module, Function, Args) -> pid()

说明:

spawn: 等同于没有opt的spawn_opt
spawn_link: 等同于opt带[link]的spawn_opt
spawn_monitor: 等同于opt带[monitor]的spawn_opt

实例:

spawn(fun() -> server("Hello") end).

spawn(io,format, ["hello world~n"]).

spawn_opt/2/3/4/5

结构:

spawn_opt(Fun, Options) -> pid() | {pid(), reference()}
spawn_opt(Node, Fun, Options) -> pid() | {pid(), reference()}
spawn_opt(Module, Function, Args, Options) ->
          pid() | {pid(), reference()}
spawn_opt(Node, Module, Function, Args, Options) ->
          pid() | {pid(), reference()}

类型
Node = node()
Fun = function()
Options = [spawn_opt_option()]
spawn_opt_option() =
    link |
    monitor |
    {priority, Level :: low | normal | high | max} |
    {fullsweep_after, Number :: integer() >= 0} |
    {min_heap_size, Size :: integer() >= 0} |
    {min_bin_vheap_size, VSize :: integer() >= 0} |
    {max_heap_size, Size :: integer() >= 0 |
          #{size => integer() >= 0, kill => boolean(), error_logger => boolean()}} |
    {message_queue_data, MQD :: off_heap | on_heap}

说明:

等同于有Options的spawn/3

Options选项说明:

link: 等同于spawn_link/3
monitor: 等同于monitor/2
{priority, Level}: 等同于运行process_flag(priority,Level)
{fullsweep_after, Number}: 用于调优, @todo
{min_heap_size, Size}: 用于调优, 设定最小heap,当大于系统默认值时,垃圾回收次数变少,提高性能
{min_bin_vheap_size, VSize}: 用于调优,minimum binary virtual heap size
{max_heap_size, Size}: 默认值是可通过参数+hmax修改.说见:process_flag(max_heap_size,Size).
{message_queue_data, MQD}: 参数+hmqd修改,process_flag(message_queue_data,MQD)

monitor/1

结构:

monitor(Type, Item) -> MonitorRef
类型:
Type: process | port | time_offset
Item: monitor_process_identifier()  |
          monitor_port_identifier() |
          clock_service
MonitorRef = reference()
registered_process_identifier() =
    registered_name() | {registered_name(), node()}
monitor_process_identifier() =
    pid() | registered_process_identifier()
monitor_port_identifier() = port() | registered_name()

说明:

发送一个类型为Type的monitor请求给Item指定的「实体」,
if这个monitored的「实体」不存在或变化,会给监控者发送如下message
{Tag, MonitorRef, Type, Object, Info}

Type为process | port只会触发一次，之后就会被移除，触发时发送消息格式:
{'DOWN', MonitorRef, Type, Object, Info}

Object:

pid() or port()           % when monitoring a local process or port

RegisteredName
{RegisteredName, Node}    % when monitoring process or port by name

Info:

进程exit的原因
noproc: 进程、port不存在
noconnection: 没连接到要监控进程对应的node

Type为time_offset:

@todo
{'CHANGE', MonitorRef, Type, Item, NewTimeOffset}

system_info/2

backtrace_depth:

erlang:system_flag(backtrace_depth, Depth) -> OldDepth
类型:
Depth = OldDepth = integer() >= 0

scheduler_wall_time:

system_flag(scheduler_wall_time, Boolean) ->
                    OldBoolean
类型:
Boolean = OldBoolean = boolean()
说明:
Turns on or off scheduler wall time measurements.
查看:erlang:statistics(scheduler_wall_time).

statistics/1

scheduler_wall_time:

statistics(scheduler_wall_time) ->
            [{SchedulerId, ActiveTime, TotalTime}] | undefined
类型:
SchedulerId = integer() >= 1
ActiveTime = TotalTime = integer() >= 0

io:

statistics(Item :: io) -> {{input, Input}, {output, Output}}
类型:
Input = Output = integer() >= 0
返回值:
Input:通过ports接收的total number of bytes
Output:通过ports发出的的total number of bytes

garbage_collection:

statistics(Item :: garbage_collection) ->
              {Number_of_GCs, Words_Reclaimed, 0}
类型:
  Number_of_GCs = Words_Reclaimed = integer() >= 0
说明:
  返回garbage collection的信息
  注:对某此实现,此信息可能无效
实例:
  > statistics(garbage_collection).
  {85,23961,0}

run_queue:

statistics(run_queue) -> integer() >= 0
实例:
  erlang:statistics(run_queue).
说明:
the number of processes and ports that are ready to run on all available normal run-queues.
Dirty run queues are not part of the result.
The information is gathered atomically. That is, the result is a consistent snapshot of the state, but this operation is much more expensive compared to statistics(total_run_queue_lengths), especially when a large amount of schedulers is used.

total_run_queue_lengths:

statistics(total_run_queue_lengths) ->
            TotalRunQueueLengths
实例:
  erlang:statistics(total_run_queue_lengths).
类型:
TotalRunQueueLengths = integer() >= 0
The same as calling lists:sum(statistics(run_queue_lengths)), but more efficient.

total_run_queue_lengths_all:

The same as calling lists:sum(statistics(run_queue_lengths_all)), but more efficient.

wall_clock:

statistics(wall_clock) ->
  {Total_Wallclock_Time, Wallclock_Time_Since_Last_Call}

Returns information about wall clock.
wall_clock can be used in the same manner as runtime,
except that real time is measured as opposed to runtime or CPU time.

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