ObjectSpace

Module

The objspace library extends the ObjectSpace module and adds several methods to get internal statistic information about object/memory management.

You need to require 'objspace' to use this extension module.

Generally, you *SHOULD NOT* use this library if you do not know about the MRI implementation. Mainly, this library is for (memory) profiler developers and MRI developers who need to know about MRI memory usage.

The ObjectSpace module contains a number of routines that interact with the garbage collection facility and allow you to traverse all living objects with an iterator.

ObjectSpace also provides support for object finalizers, procs that will be called when a specific object is about to be destroyed by garbage collection.

require 'objspace'

a = "A"
b = "B"

ObjectSpace.define_finalizer(a, proc {|id| puts "Finalizer one on #{id}" })
ObjectSpace.define_finalizer(b, proc {|id| puts "Finalizer two on #{id}" })

produces:

Finalizer two on 537763470
Finalizer one on 537763480
Class Methods

ObjectSpace._id2ref(object_id) → an_object
::

Converts an object id to a reference to the object. May not be called on an object id passed as a parameter to a finalizer.

s = "I am a string"                    #=> "I am a string"
r = ObjectSpace._id2ref(s.object_id)   #=> "I am a string"
r == s                                 #=> true

allocation_class_path(object) → string
::

Returns the class for the given object.

class A
  def foo
    ObjectSpace::trace_object_allocations do
      obj = Object.new
      p "#{ObjectSpace::allocation_class_path(obj)}"
    end
  end
end

A.new.foo #=> "Class"

See ::trace_object_allocations for more information and examples.

allocation_generation(object) → Fixnum
::

Returns garbage collector generation for the given object.

class B
  include ObjectSpace

  def foo
    trace_object_allocations do
      obj = Object.new
      p "Generation is #{allocation_generation(obj)}"
    end
  end
end

B.new.foo #=> "Generation is 3"

See ::trace_object_allocations for more information and examples.

allocation_method_id(object) → string
::

Returns the method identifier for the given object.

class A
  include ObjectSpace

  def foo
    trace_object_allocations do
      obj = Object.new
      p "#{allocation_class_path(obj)}##{allocation_method_id(obj)}"
    end
  end
end

A.new.foo #=> "Class#new"

See ::trace_object_allocations for more information and examples.

allocation_sourcefile(object) → string
::

Returns the source file origin from the given object.

See ::trace_object_allocations for more information and examples.

allocation_sourceline(object) → string
::

Returns the original line from source for from the given object.

See ::trace_object_allocations for more information and examples.

ObjectSpace.count_imemo_objects([result_hash]) → hash
::

Counts objects for each T_IMEMO type.

This method is only for MRI developers interested in performance and memory usage of Ruby programs.

It returns a hash as:

{:imemo_ifunc=>8,
 :imemo_svar=>7,
 :imemo_cref=>509,
 :imemo_memo=>1,
 :imemo_throw_data=>1}

If the optional argument, result_hash, is given, it is overwritten and returned. This is intended to avoid probe effect.

The contents of the returned hash is implementation specific and may change in the future.

In this version, keys are symbol objects.

This method is only expected to work with C Ruby.

ObjectSpace.count_nodes([result_hash]) → hash
::

Counts nodes for each node type.

This method is only for MRI developers interested in performance and memory usage of Ruby programs.

It returns a hash as:

{:NODE_METHOD=>2027, :NODE_FBODY=>1927, :NODE_CFUNC=>1798, ...}

If the optional argument, result_hash, is given, it is overwritten and returned. This is intended to avoid probe effect.

Note: The contents of the returned hash is implementation defined. It may be changed in future.

This method is only expected to work with C Ruby.

ObjectSpace.count_objects([result_hash]) → hash
::

Counts all objects grouped by type.

It returns a hash, such as:

{
  :TOTAL=>10000,
  :FREE=>3011,
  :T_OBJECT=>6,
  :T_CLASS=>404,
  # ...
}

The contents of the returned hash are implementation specific. It may be changed in future.

The keys starting with :T_ means live objects. For example, :T_ARRAY is the number of arrays. :FREE means object slots which is not used now. :TOTAL means sum of above.

If the optional argument result_hash is given, it is overwritten and returned. This is intended to avoid probe effect.

h = {}
ObjectSpace.count_objects(h)
puts h
# => { :TOTAL=>10000, :T_CLASS=>158280, :T_MODULE=>20672, :T_STRING=>527249 }

This method is only expected to work on C Ruby.

ObjectSpace.count_objects_size([result_hash]) → hash
::

Counts objects size (in bytes) for each type.

Note that this information is incomplete. You need to deal with this information as only a HINT. Especially, total size of T_DATA may not right size.

It returns a hash as:

{:TOTAL=>1461154, :T_CLASS=>158280, :T_MODULE=>20672, :T_STRING=>527249, ...}

If the optional argument, result_hash, is given, it is overwritten and returned. This is intended to avoid probe effect.

The contents of the returned hash is implementation defined. It may be changed in future.

This method is only expected to work with C Ruby.

ObjectSpace.count_symbols([result_hash]) → hash
::

Counts symbols for each Symbol type.

This method is only for MRI developers interested in performance and memory usage of Ruby programs.

If the optional argument, result_hash, is given, it is overwritten and returned. This is intended to avoid probe effect.

Note: The contents of the returned hash is implementation defined. It may be changed in future.

This method is only expected to work with C Ruby.

On this version of MRI, they have 3 types of Symbols (and 1 total counts).

* mortal_dynamic_symbol: GC target symbols (collected by GC)
* immortal_dynamic_symbol: Immortal symbols promoted from dynamic symbols (do not collected by GC)
* immortal_static_symbol: Immortal symbols (do not collected by GC)
* immortal_symbol: total immortal symbols (immortal_dynamic_symbol+immortal_static_symbol)

ObjectSpace.count_tdata_objects([result_hash]) → hash
::

Counts objects for each T_DATA type.

This method is only for MRI developers interested in performance and memory usage of Ruby programs.

It returns a hash as:

{RubyVM::InstructionSequence=>504, :parser=>5, :barrier=>6,
 :mutex=>6, Proc=>60, RubyVM::Env=>57, Mutex=>1, Encoding=>99,
 ThreadGroup=>1, Binding=>1, Thread=>1, RubyVM=>1, :iseq=>1,
 Random=>1, ARGF.class=>1, Data=>1, :autoload=>3, Time=>2}
# T_DATA objects existing at startup on r32276.

If the optional argument, result_hash, is given, it is overwritten and returned. This is intended to avoid probe effect.

The contents of the returned hash is implementation specific and may change in the future.

In this version, keys are Class object or Symbol object.

If object is kind of normal (accessible) object, the key is Class object. If object is not a kind of normal (internal) object, the key is symbol name, registered by rb_data_type_struct.

This method is only expected to work with C Ruby.

ObjectSpace.define_finalizer(obj, aProc=proc())
::

Adds aProc as a finalizer, to be called after obj was destroyed. The object ID of the obj will be passed as an argument to aProc. If aProc is a lambda or method, make sure it can be called with a single argument.

ObjectSpace.dump(obj[, output: :string]) # => "{ ... }"

ObjectSpace.dump(obj, output: :file) # => #<File:/tmp/rubyobj20131125-88733-1xkfmpv.json>

ObjectSpace.dump(obj, output: :stdout) # => nil
::

Dump the contents of a ruby object as JSON.

This method is only expected to work with C Ruby. This is an experimental method and is subject to change. In particular, the function signature and output format are not guaranteed to be compatible in future versions of ruby.

ObjectSpace.dump_all([output: :file]) # => #<File:/tmp/rubyheap20131125-88469-laoj3v.json>

ObjectSpace.dump_all(output: :stdout) # => nil

ObjectSpace.dump_all(output: :string) # => "{...}\n{...}\n..."

ObjectSpace.dump_all(output:

File.open('heap.json','w')) # => #<File:heap.json>
::

Dump the contents of the ruby heap as JSON.

This method is only expected to work with C Ruby. This is an experimental method and is subject to change. In particular, the function signature and output format are not guaranteed to be compatible in future versions of ruby.

ObjectSpace.each_object([module]) {|obj| ... } → fixnum

ObjectSpace.each_object([module]) → an_enumerator
::

Calls the block once for each living, nonimmediate object in this Ruby process. If module is specified, calls the block for only those classes or modules that match (or are a subclass of) module. Returns the number of objects found. Immediate objects (Fixnums, Symbols true, false, and nil) are never returned. In the example below, each_object returns both the numbers we defined and several constants defined in the Math module.

If no block is given, an enumerator is returned instead.

a = 102.7
b = 95       # Won't be returned
c = 12345678987654321
count = ObjectSpace.each_object(Numeric) {|x| p x }
puts "Total count: #{count}"

produces:

12345678987654321
102.7
2.71828182845905
3.14159265358979
2.22044604925031e-16
1.7976931348623157e+308
2.2250738585072e-308
Total count: 7

GC.start → nil

GC.garbage_collect → nil

GC.start(full_mark: true, immediate_sweep: true) → nil

GC.garbage_collect(full_mark: true, immediate_sweep: true) → nil
::

Initiates garbage collection, unless manually disabled.

This method is defined with keyword arguments that default to true:

def GC.start(full_mark: true, immediate_sweep: true); end

Use full_mark: false to perform a minor GC. Use immediate_sweep: false to defer sweeping (use lazy sweep).

Note: These keyword arguments are implementation and version dependent. They are not guaranteed to be future-compatible, and may be ignored if the underlying implementation does not support them.

ObjectSpace.internal_class_of(obj) → Class or Module
::
MRI specific feature

Return internal class of obj.

obj can be an instance of InternalObjectWrapper.

Note that you should not use this method in your application.

ObjectSpace.internal_super_of(cls) → Class or Module
::
MRI specific feature

Return internal super class of cls (Class or Module).

obj can be an instance of InternalObjectWrapper.

Note that you should not use this method in your application.

ObjectSpace.memsize_of(obj) → Integer
::

Return consuming memory size of obj.

Note that the return size is incomplete. You need to deal with this information as only a HINT. Especially, the size of T_DATA may not be correct.

This method is only expected to work with C Ruby.

From Ruby 2.2, memsize_of(obj) returns a memory size includes sizeof(RVALUE).

ObjectSpace.memsize_of_all([klass]) → Integer
::

Return consuming memory size of all living objects.

If klass (should be Class object) is given, return the total memory size of instances of the given class.

Note that the returned size is incomplete. You need to deal with this information as only a HINT. Especially, the size of T_DATA may not be correct.

Note that this method does NOT return total malloc’ed memory size.

This method can be defined by the following Ruby code:

def memsize_of_all klass = false
  total = 0
  ObjectSpace.each_object{|e|
    total += ObjectSpace.memsize_of(e) if klass == false || e.kind_of?(klass)
  }
  total
end

This method is only expected to work with C Ruby.

ObjectSpace.reachable_objects_from(obj) → array or nil
::
MRI specific feature

Return all reachable objects from ‘obj’.

This method returns all reachable objects from ‘obj’.

If ‘obj’ has two or more references to the same object ‘x’, then returned array only includes one ‘x’ object.

If ‘obj’ is a non-markable (non-heap management) object such as true, false, nil, symbols and Fixnums (and Flonum) then it simply returns nil.

If ‘obj’ has references to an internal object, then it returns instances of ObjectSpace::InternalObjectWrapper class. This object contains a reference to an internal object and you can check the type of internal object with ‘type’ method.

If ‘obj’ is instance of ObjectSpace::InternalObjectWrapper class, then this method returns all reachable object from an internal object, which is pointed by ‘obj’.

With this method, you can find memory leaks.

This method is only expected to work except with C Ruby.

Example:

ObjectSpace.reachable_objects_from(['a', 'b', 'c'])
#=> [Array, 'a', 'b', 'c']

ObjectSpace.reachable_objects_from(['a', 'a', 'a'])
#=> [Array, 'a', 'a', 'a'] # all 'a' strings have different object id

ObjectSpace.reachable_objects_from([v = 'a', v, v])
#=> [Array, 'a']

ObjectSpace.reachable_objects_from(1)
#=> nil # 1 is not markable (heap managed) object

ObjectSpace.reachable_objects_from_root → hash
::
MRI specific feature

Return all reachable objects from root.

trace_object_allocations { block }
::

Starts tracing object allocations from the ObjectSpace extension module.

For example:

require 'objspace'

class C
  include ObjectSpace

  def foo
    trace_object_allocations do
      obj = Object.new
      p "#{allocation_sourcefile(obj)}:#{allocation_sourceline(obj)}"
    end
  end
end

C.new.foo #=> "objtrace.rb:8"

This example has included the ObjectSpace module to make it easier to read, but you can also use the ::trace_object_allocations notation (recommended).

Note that this feature introduces a huge performance decrease and huge memory consumption.

trace_object_allocations_clear
::

Clear recorded tracing information.

trace_object_allocations_debug_start
::
No documentation available

trace_object_allocations_start
::

Starts tracing object allocations.

trace_object_allocations_stop
::

Stop tracing object allocations.

Note that if ::trace_object_allocations_start is called n-times, then tracing will stop after calling ::trace_object_allocations_stop n-times.

ObjectSpace.undefine_finalizer(obj)
::

Removes all finalizers for obj.