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Module: GC

Relationships & Source Files
Namespace Children
Classes:
Profiler
Defined in: gc.rb,
gc.c

Overview

The GC module provides an interface to Ruby's mark-and-sweep garbage collection mechanism.

Some of the underlying methods are also available via the ::ObjectSpace module.

You may obtain information about the operation of the GC through Profiler.

Class Attribute Summary

Class Method Summary

Instance Method Summary

Class Attribute Details

.measure_total_time ⇒ Boolean (rw)

Returns the measure_total_time flag (default: true). Note that measurement can affect the application's performance.

[ GitHub ] 

  


# File 'gc.rb', line 376



def self.measure_total_time
  Primitive.cexpr! %{
    RBOOL(rb_gc_impl_get_measure_total_time(rb_gc_get_objspace()))
  }
end


  








  

    .measure_total_time=(true/false)   (rw)  



  

    
Enables measuring GC time.
You can get the result with GC.stat(:time).
Note that GC time measurement can cause some performance overhead.

  



  [ GitHub ]


  

  


# File 'gc.rb', line 364



def self.measure_total_time=(flag)
  Primitive.cstmt! %{
    rb_gc_impl_set_measure_total_time(rb_gc_get_objspace(), flag);
    return flag;
  }
end


  








  

    .stress  ⇒ Integer, ...  (rw)  



  

    
Returns the current status of GC stress mode.

  



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# File 'gc.rb', line 74



def self.stress
  Primitive.gc_stress_get
end


  








  

    .stress=(flag)  ⇒ flag  (rw)  



  

    
Updates the GC stress mode.


When stress mode is enabled, the GC is invoked at every GC opportunity:
all memory and object allocations.


Enabling stress mode will degrade performance; it is only for debugging.


The flag can be true, false, or an integer bitwise-ORed with the following flags:


0x01:: no major GC
0x02:: no immediate sweep
0x04:: full mark after malloc/calloc/realloc

  



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# File 'gc.rb', line 92



def self.stress=(flag)
  Primitive.gc_stress_set_m flag
end


  







Class Method Details



  

    

      .config  ⇒ Hash 
      .config(hash)  ⇒ Hash 
    

  



  

    
Sets or gets information about the current GC config.


Configuration parameters are GC implementation-specific and may change
without notice.


This method can be called without parameters to retrieve the current config
as a ::Hash with ::Symbol keys.


This method can also be called with a ::Hash argument to assign values to
valid config keys. Config keys missing from the passed ::Hash will be left
unmodified.


If a key/value pair is passed to this function that does not correspond to
a valid config key for the GC implementation being used, no config will be
updated, the key will be present in the returned ::Hash, and its value will
be nil. This is to facilitate easy migration between GC implementations.


In both call-seqs, the return value of config will be a ::Hash
containing the most recent full configuration, i.e., all keys and values
defined by the specific GC implementation being used. In the case of a
config update, the return value will include the new values being updated.


This method is only expected to work on CRuby.


GC Implementation independent values


The config hash can also contain keys that are global and
read-only. These keys are not specific to any one GC library implementation
and attempting to write to them will raise ::ArgumentError.


There is currently only one global, read-only key:


[implementation]
Returns a ::String containing the name of the currently loaded GC library,
if one has been loaded using RUBY_GC_LIBRARY, and "default" in all other
cases


GC Implementation specific values


GC libraries are expected to document their own configuration. Valid keys
for Ruby's default GC implementation are:


[rgengc_allow_full_mark]
Controls whether the GC is allowed to run a full mark (young & old objects).


When {true}, \GC interleaves major and minor collections. This is the default. \GC
will function as intended.

When {false}, the \GC will never trigger a full marking cycle unless
explicitly requested by user code. Instead, only a minor mark will run—
only young objects will be marked. When the heap space is exhausted, new
pages will be allocated immediately instead of running a full mark.

A flag will be set to notify that a full mark has been
requested. This flag is accessible using
<code>GC.latest_gc_info(:needs_major_by)</code>

The user can trigger a major collection at any time using
<code>GC.start(full_mark: true)</code>

When {false}, Young to Old object promotion is disabled. For performance
reasons, it is recommended to warm up an application using {Process.warmup}
before setting this parameter to {false}.

  





  


  [ GitHub ]


  

  


# File 'gc.rb', line 318



def self.config hash = nil
  return Primitive.gc_config_get unless hash

  if(Primitive.cexpr!("RBOOL(RB_TYPE_P(hash, T_HASH))"))
    if hash.include?(:implementation)
      raise ArgumentError, 'Attempting to set read-only key "Implementation"'
    end

    Primitive.gc_config_set hash
  else
    raise ArgumentError
  end
end


  








  

    .count  ⇒ Integer   



  

    
Returns the number of times GC has occurred since the process started.

  



  [ GitHub ]


  

  


# File 'gc.rb', line 100



def self.count
  Primitive.gc_count
end


  








  

    .disable  ⇒ Boolean   



  

    
Disables garbage collection, returning true if garbage
collection was already disabled.


GC.disable   #=> false
GC.disable   #=> true

  



  [ GitHub ]


  

  


# File 'gc.rb', line 66



def self.disable
  Primitive.gc_disable
end


  








  

    .enable  ⇒ Boolean   



  

    
Enables garbage collection, returning true if garbage
collection was previously disabled.


GC.disable   #=> false
GC.enable    #=> true
GC.enable    #=> false

  



  [ GitHub ]


  

  


# File 'gc.rb', line 54



def self.enable
  Primitive.gc_enable
end


  








  

    

      .latest_gc_info  ⇒ Hash 
      .latest_gc_info(hash)  ⇒ Hash 
      .latest_gc_info(key)  ⇒ value 
    

  



  

    
Returns information about the most recent garbage collection.


If the argument hash is given and is a ::Hash object,
it is overwritten and returned.
This is intended to avoid the probe effect.


If the argument key is given and is a ::Symbol object,
it returns the value associated with the key.
This is equivalent to GC.latest_gc_info.

  





  


  [ GitHub ]


  

  


# File 'gc.rb', line 346



def self.latest_gc_info hash_or_key = nil
  if hash_or_key == nil
    hash_or_key = {}
  elsif Primitive.cexpr!("RBOOL(!SYMBOL_P(hash_or_key) && !RB_TYPE_P(hash_or_key, T_HASH))")
    raise TypeError, "non-hash or symbol given"
  end

  Primitive.cstmt! %{
    return rb_gc_latest_gc_info(hash_or_key);
  }
end


  








  

    .start(full_mark: true, immediate_mark: true, immediate_sweep: true)  
  



  

    
Initiates garbage collection, even if manually disabled.


The full_mark keyword argument determines whether or not to perform a
major garbage collection cycle. When set to true, a major garbage
collection cycle is run, meaning all objects are marked. When set to
false, a minor garbage collection cycle is run, meaning only young
objects are marked.


The immediate_mark keyword argument determines whether or not to perform
incremental marking. When set to true, marking is completed during the
call to this method. When set to false, marking is performed in steps
that are interleaved with future Ruby code execution, so marking might not
be completed during this method call. Note that if full_mark is false,
then marking will always be immediate, regardless of the value of
immediate_mark.


The immediate_sweep keyword argument determines whether or not to defer
sweeping (using lazy sweep). When set to false, sweeping is performed in
steps that are interleaved with future Ruby code execution, so sweeping might
not be completed during this method call. When set to true, sweeping is
completed during the call to this method.


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.

  



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# File 'gc.rb', line 35



def self.start full_mark: true, immediate_mark: true, immediate_sweep: true
  Primitive.gc_start_internal full_mark, immediate_mark, immediate_sweep, false
end


  








  

    

      .stat  ⇒ Hash 
      .stat(hash)  ⇒ Hash 
      .stat(:key)  ⇒ Numeric 
    

  



  

    
Returns a ::Hash containing information about the GC.


The contents of the hash are implementation-specific and may change in
the future without notice.


The hash includes internal statistics about GC such as:


[count]
The total number of garbage collections run since application start
(count includes both minor and major garbage collections)
[time]
The total time spent in garbage collections (in milliseconds)
[heap_allocated_pages]
The total number of :heap_eden_pages + :heap_tomb_pages
[heap_sorted_length]
The number of pages that can fit into the buffer that holds references to
all pages
[heap_allocatable_pages]
The total number of pages the application could allocate without additional GC
[heap_available_slots]
The total number of slots in all :heap_allocated_pages
[heap_live_slots]
The total number of slots which contain live objects
[heap_free_slots]
The total number of slots which do not contain live objects
[heap_final_slots]
The total number of slots with pending finalizers to be run
[heap_marked_slots]
The total number of objects marked in the last GC
[heap_eden_pages]
The total number of pages which contain at least one live slot
[heap_tomb_pages]
The total number of pages which do not contain any live slots
[total_allocated_pages]
The cumulative number of pages allocated since application start
[total_freed_pages]
The cumulative number of pages freed since application start
[total_allocated_objects]
The cumulative number of objects allocated since application start
[total_freed_objects]
The cumulative number of objects freed since application start
[malloc_increase_bytes]
Amount of memory allocated on the heap for objects. Decreased by any GC
[malloc_increase_bytes_limit]
When :malloc_increase_bytes crosses this limit, GC is triggered
[minor_gc_count]
The total number of minor garbage collections run since process start
[major_gc_count]
The total number of major garbage collections run since process start
[compact_count]
The total number of compactions run since process start
[read_barrier_faults]
The total number of times the read barrier was triggered during
compaction
[total_moved_objects]
The total number of objects compaction has moved
[remembered_wb_unprotected_objects]
The total number of objects without write barriers
[remembered_wb_unprotected_objects_limit]
When :remembered_wb_unprotected_objects crosses this limit,
major GC is triggered
[old_objects]
Number of live, old objects which have survived at least 3 garbage collections
[old_objects_limit]
When :old_objects crosses this limit, major GC is triggered
[oldmalloc_increase_bytes]
Amount of memory allocated on the heap for objects. Decreased by major GC
[oldmalloc_increase_bytes_limit]
When :oldmalloc_increase_bytes crosses this limit, major GC is triggered


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


This method is only expected to work on CRuby.

  





  


  [ GitHub ]


  

  


# File 'gc.rb', line 184



def self.stat hash_or_key = nil
  Primitive.gc_stat hash_or_key
end


  








  

    

      .stat_heap  ⇒ Hash 
      .stat_heap(nil, hash)  ⇒ Hash 
      .stat_heap(heap_name)  ⇒ Hash 
      .stat_heap(heap_name, hash)  ⇒ Hash 
      .stat_heap(heap_name, :key)  ⇒ Numeric 
    

  



  

    
Returns information for heaps in the GC.


If the first optional argument, heap_name, is passed in and not nil, it
returns a ::Hash containing information about the particular heap.
Otherwise, it will return a ::Hash with heap names as keys and
a ::Hash containing information about the heap as values.


If the second optional argument, hash_or_key, is given as a ::Hash, it will
be overwritten and returned. This is intended to avoid the probe effect.


If both optional arguments are passed in and the second optional argument is
a symbol, it will return a ::Numeric value for the particular heap.


On CRuby, heap_name is of the type ::Integer but may be of type ::String
on other implementations.


The contents of the hash are implementation-specific and may change in
the future without notice.


If the optional argument, hash, is given, it is overwritten and returned.


This method is only expected to work on CRuby.


The hash includes the following keys about the internal information in
the GC:


[slot_size]
The slot size of the heap in bytes.
[heap_allocatable_pages]
The number of pages that can be allocated without triggering a new
garbage collection cycle.
[heap_eden_pages]
The number of pages in the eden heap.
[heap_eden_slots]
The total number of slots in all of the pages in the eden heap.
[heap_tomb_pages]
The number of pages in the tomb heap. The tomb heap only contains pages
that do not have any live objects.
[heap_tomb_slots]
The total number of slots in all of the pages in the tomb heap.
[total_allocated_pages]
The total number of pages that have been allocated in the heap.
[total_freed_pages]
The total number of pages that have been freed and released back to the
system in the heap.
[force_major_gc_count]
The number of times this heap has forced major garbage collection cycles
to start due to running out of free slots.
[force_incremental_marking_finish_count]
The number of times this heap has forced incremental marking to complete
due to running out of pooled slots.

  





  


  [ GitHub ]


  

  


# File 'gc.rb', line 247



def self.stat_heap heap_name = nil, hash_or_key = nil
  Primitive.gc_stat_heap heap_name, hash_or_key
end


  








  

    .total_time  ⇒ Integer   



  

    
Returns the measured GC total time in nanoseconds.

  



  [ GitHub ]


  

  


# File 'gc.rb', line 386



def self.total_time
  Primitive.cexpr! %{
    ULL2NUM(rb_gc_impl_get_total_time(rb_gc_get_objspace()))
  }
end


  







Instance Method Details



  

    #garbage_collect(full_mark: true, immediate_mark: true, immediate_sweep: true)  
  



  

    
Alias of .start

  



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# File 'gc.rb', line 40



def garbage_collect full_mark: true, immediate_mark: true, immediate_sweep: true
  Primitive.gc_start_internal full_mark, immediate_mark, immediate_sweep, false
end