module GC

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 GC::Profiler.

Constants

INTERNAL_CONSTANTS

internal constants

OPTS

GC build options

Public Class Methods

add_stress_to_class(class[, ...]) click to toggle source

Raises NoMemoryError when allocating an instance of the given classes.

static VALUE
rb_gcdebug_add_stress_to_class(int argc, VALUE *argv, VALUE self)
{
    rb_objspace_t *objspace = &rb_objspace;

    if (!stress_to_class) {
        stress_to_class = rb_ary_tmp_new(argc);
    }
    rb_ary_cat(stress_to_class, argv, argc);
    return self;
}
auto_compact → true or false click to toggle source

Returns whether or not automatic compaction has been enabled.

# File gc.rb, line 46
def self.auto_compact
  Primitive.gc_get_auto_compact
end
auto_compact = flag click to toggle source

Updates automatic compaction mode.

When enabled, the compactor will execute on every major collection.

Enabling compaction will degrade performance on major collections.

# File gc.rb, line 58
def self.auto_compact=(flag)
  Primitive.gc_set_auto_compact(flag)
end
compact click to toggle source

This function compacts objects together in Ruby’s heap. It eliminates unused space (or fragmentation) in the heap by moving objects in to that unused space. This function returns a hash which contains statistics about which objects were moved. See ‘GC.latest_gc_info` for details about compaction statistics.

This method is implementation specific and not expected to be implemented in any implementation besides MRI.

# File gc.rb, line 212
def self.compact
  Primitive.gc_compact
end
count → Integer click to toggle source

The number of times GC occurred.

It returns the number of times GC occurred since the process started.

# File gc.rb, line 120
def self.count
  Primitive.gc_count
end
disable → true or false click to toggle source

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

GC.disable   #=> false
GC.disable   #=> true
# File gc.rb, line 84
def self.disable
  Primitive.gc_disable
end
enable → true or false click to toggle source

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

GC.disable   #=> false
GC.enable    #=> true
GC.enable    #=> false
# File gc.rb, line 72
def self.enable
  Primitive.gc_enable
end
latest_compact_info -> {:considered=>{:T_CLASS=>11}, :moved=>{:T_CLASS→11}} click to toggle source
Returns information about object moved in the most recent GC compaction.

The returned hash has two keys :considered and :moved. The hash for :considered lists the number of objects that were considered for movement by the compactor, and the :moved hash lists the number of objects that were actually moved. Some objects can’t be moved (maybe they were pinned) so these numbers can be used to calculate compaction efficiency.

# File gc.rb, line 197
def self.latest_compact_info
  Primitive.gc_compact_stats
end
latest_gc_info -> {:gc_by→:newobj} click to toggle source
latest_gc_info(hash) → hash
latest_gc_info(:major_by) → :malloc
Returns information about the most recent garbage collection.

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

# File gc.rb, line 183
def self.latest_gc_info hash_or_key = nil
  Primitive.gc_latest_gc_info hash_or_key
end
malloc_allocated_size → Integer click to toggle source

Returns the size of memory allocated by malloc().

Only available if ruby was built with CALC_EXACT_MALLOC_SIZE.

static VALUE
gc_malloc_allocated_size(VALUE self)
{
    return UINT2NUM(rb_objspace.malloc_params.allocated_size);
}
malloc_allocations → Integer click to toggle source

Returns the number of malloc() allocations.

Only available if ruby was built with CALC_EXACT_MALLOC_SIZE.

static VALUE
gc_malloc_allocations(VALUE self)
{
    return UINT2NUM(rb_objspace.malloc_params.allocations);
}
remove_stress_to_class(class[, ...]) click to toggle source

No longer raises NoMemoryError when allocating an instance of the given classes.

static VALUE
rb_gcdebug_remove_stress_to_class(int argc, VALUE *argv, VALUE self)
{
    rb_objspace_t *objspace = &rb_objspace;
    int i;

    if (stress_to_class) {
        for (i = 0; i < argc; ++i) {
            rb_ary_delete_same(stress_to_class, argv[i]);
        }
        if (RARRAY_LEN(stress_to_class) == 0) {
            stress_to_class = 0;
        }
    }
    return Qnil;
}
start → nil click to toggle source
garbage_collect → nil
include GC; garbage_collect → nil
start(full_mark: true, immediate_sweep: true) → nil
garbage_collect(full_mark: true, immediate_sweep: true) → nil
include GC; garbage_collect(full_mark: true, immediate_sweep: true) → nil

Initiates garbage collection, even if 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.

# File gc.rb, line 33
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 click to toggle source
stat(hash) → hash
stat(:key) → Numeric

Returns a Hash containing information about the GC.

The hash includes information about internal statistics about GC such as:

{
    :count=>0,
    :heap_allocated_pages=>24,
    :heap_sorted_length=>24,
    :heap_allocatable_pages=>0,
    :heap_available_slots=>9783,
    :heap_live_slots=>7713,
    :heap_free_slots=>2070,
    :heap_final_slots=>0,
    :heap_marked_slots=>0,
    :heap_eden_pages=>24,
    :heap_tomb_pages=>0,
    :total_allocated_pages=>24,
    :total_freed_pages=>0,
    :total_allocated_objects=>7796,
    :total_freed_objects=>83,
    :malloc_increase_bytes=>2389312,
    :malloc_increase_bytes_limit=>16777216,
    :minor_gc_count=>0,
    :major_gc_count=>0,
    :remembered_wb_unprotected_objects=>0,
    :remembered_wb_unprotected_objects_limit=>0,
    :old_objects=>0,
    :old_objects_limit=>0,
    :oldmalloc_increase_bytes=>2389760,
    :oldmalloc_increase_bytes_limit=>16777216
}

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

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

This method is only expected to work on C Ruby.

# File gc.rb, line 169
def self.stat hash_or_key = nil
  Primitive.gc_stat hash_or_key
end
stress → integer, true or false click to toggle source

Returns current status of GC stress mode.

# File gc.rb, line 92
def self.stress
  Primitive.gc_stress_get
end
stress = flag → flag click to toggle source

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.

flag can be true, false, or an integer bit-ORed following flags.

0x01:: no major GC
0x02:: no immediate sweep
0x04:: full mark after malloc/calloc/realloc
# File gc.rb, line 110
def self.stress=(flag)
  Primitive.gc_stress_set_m flag
end
verify_compaction_references(toward: nil, double_heap: false) → hash click to toggle source

Verify compaction reference consistency.

This method is implementation specific. During compaction, objects that were moved are replaced with T_MOVED objects. No object should have a reference to a T_MOVED object after compaction.

This function doubles the heap to ensure room to move all objects, compacts the heap to make sure everything moves, updates all references, then performs a full GC. If any object contains a reference to a T_MOVED object, that object should be pushed on the mark stack, and will make a SEGV.

# File gc.rb, line 230
def self.verify_compaction_references(toward: nil, double_heap: false)
  Primitive.gc_verify_compaction_references(double_heap, toward == :empty)
end
verify_internal_consistency → nil click to toggle source

Verify internal consistency.

This method is implementation specific. Now this method checks generational consistency if RGenGC is supported.

static VALUE
gc_verify_internal_consistency_m(VALUE dummy)
{
    gc_verify_internal_consistency(&rb_objspace);
    return Qnil;
}
verify_transient_heap_internal_consistency() click to toggle source
static VALUE
gc_verify_transient_heap_internal_consistency(VALUE dmy)
{
    rb_transient_heap_verify();
    return Qnil;
}

Public Instance Methods

garbage_collect(full_mark: true, immediate_mark: true, immediate_sweep: true) click to toggle source
# File gc.rb, line 37
def garbage_collect full_mark: true, immediate_mark: true, immediate_sweep: true
  Primitive.gc_start_internal full_mark, immediate_mark, immediate_sweep, false
end