GC

Module

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

Class Methods

GC.add_stress_to_class(class[, ...])

gc.c View on GitHub

          
            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;
}

Raises NoMemoryError when allocating an instance of the given classes.

GC.count → Integer

gc.c View on GitHub

          
            static VALUE
gc_count(VALUE self)
{
    return SIZET2NUM(rb_gc_count());
}

The number of times GC occurred.

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

GC.disable → true or false

gc.c View on GitHub

          
            VALUE
rb_gc_disable(void)
{
    rb_objspace_t *objspace = &rb_objspace;
    int old = dont_gc;

    gc_rest(objspace);

    dont_gc = TRUE;
    return old ? Qtrue : Qfalse;
}

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

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

GC.enable → true or false

gc.c View on GitHub

          
            VALUE
rb_gc_enable(void)
{
    rb_objspace_t *objspace = &rb_objspace;
    int old = dont_gc;

    dont_gc = FALSE;
    return old ? Qtrue : Qfalse;
}

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

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

GC.latest_gc_info → {:gc_by=>:newobj}

GC.latest_gc_info(hash) → hash

GC.latest_gc_info(:major_by) → :malloc

gc.c View on GitHub

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

    if (rb_check_arity(argc, 0, 1) == 1) {
        arg = argv[0];
        if (!SYMBOL_P(arg) && !RB_TYPE_P(arg, T_HASH)) {
            rb_raise(rb_eTypeError, "non-hash or symbol given");
        }
    }
    else {
        arg = rb_hash_new();
    }

    return gc_info_decode(objspace, arg, 0);
}

Returns information about the most recent garbage collection.

GC.malloc_allocated_size → Integer

gc.c View on GitHub

          
            static VALUE
gc_malloc_allocated_size(VALUE self)
{
    return UINT2NUM(rb_objspace.malloc_params.allocated_size);
}

Returns the size of memory allocated by malloc().

Only available if ruby was built with CALC_EXACT_MALLOC_SIZE.

GC.malloc_allocations → Integer

gc.c View on GitHub

          
            static VALUE
gc_malloc_allocations(VALUE self)
{
    return UINT2NUM(rb_objspace.malloc_params.allocations);
}

Returns the number of malloc() allocations.

Only available if ruby was built with CALC_EXACT_MALLOC_SIZE.

GC.remove_stress_to_class(class[, ...])

gc.c View on GitHub

          
            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;
}

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

GC.start → nil

ObjectSpace.garbage_collect → nil

include GC; garbage_collect → nil

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

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

include GC; garbage_collect(full_mark: true, immediate_sweep: true) → nil

gc.c View on GitHub

          
            static VALUE
gc_start_internal(int argc, VALUE *argv, VALUE self)
{
    rb_objspace_t *objspace = &rb_objspace;
    int reason = GPR_FLAG_FULL_MARK | GPR_FLAG_IMMEDIATE_MARK |
                GPR_FLAG_IMMEDIATE_SWEEP | GPR_FLAG_METHOD;
    VALUE opt = Qnil;
    static ID keyword_ids[3];

    rb_scan_args(argc, argv, "0:", &opt);

    if (!NIL_P(opt)) {
        VALUE kwvals[3];

        if (!keyword_ids[0]) {
            keyword_ids[0] = rb_intern("full_mark");
            keyword_ids[1] = rb_intern("immediate_mark");
            keyword_ids[2] = rb_intern("immediate_sweep");
        }

        rb_get_kwargs(opt, keyword_ids, 0, 3, kwvals);

        if (kwvals[0] != Qundef && !RTEST(kwvals[0])) {
            reason &= ~GPR_FLAG_FULL_MARK;
        }
        if (kwvals[1] != Qundef && !RTEST(kwvals[1])) {
            reason &= ~GPR_FLAG_IMMEDIATE_MARK;
        }
        if (kwvals[2] != Qundef && !RTEST(kwvals[2])) {
            reason &= ~GPR_FLAG_IMMEDIATE_SWEEP;
        }
    }

    garbage_collect(objspace, reason);
    gc_finalize_deferred(objspace);

    return Qnil;
}

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.

GC.stat → Hash

GC.stat(hash) → hash

GC.stat(:key) → Numeric

gc.c View on GitHub

          
            static VALUE
gc_stat(int argc, VALUE *argv, VALUE self)
{
    VALUE arg = Qnil;

    if (rb_check_arity(argc, 0, 1) == 1) {
        arg = argv[0];
        if (SYMBOL_P(arg)) {
            size_t value = gc_stat_internal(arg);
            return SIZET2NUM(value);
        }
        else if (!RB_TYPE_P(arg, T_HASH)) {
            rb_raise(rb_eTypeError, "non-hash or symbol given");
        }
    }
    else {
        arg = rb_hash_new();
    }
    gc_stat_internal(arg);
    return arg;
}

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.

This method is only expected to work on C Ruby.

GC.stress → integer, true or false

gc.c View on GitHub

          
            static VALUE
gc_stress_get(VALUE self)
{
    rb_objspace_t *objspace = &rb_objspace;
    return ruby_gc_stress_mode;
}

Returns current status of GC stress mode.

GC.stress = flag → flag

gc.c View on GitHub

          
            static VALUE
gc_stress_set_m(VALUE self, VALUE flag)
{
    rb_objspace_t *objspace = &rb_objspace;
    gc_stress_set(objspace, flag);
    return flag;
}

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

GC.verify_internal_consistency → nil

gc.c View on GitHub

          
            static VALUE
gc_verify_internal_consistency(VALUE dummy)
{
    rb_objspace_t *objspace = &rb_objspace;
    struct verify_internal_consistency_struct data = {0};
    struct each_obj_args eo_args;

    data.objspace = objspace;
    gc_report(5, objspace, "gc_verify_internal_consistency: start\n");

    /* check relations */

    eo_args.callback = verify_internal_consistency_i;
    eo_args.data = (void *)&data;
    objspace_each_objects((VALUE)&eo_args);

    if (data.err_count != 0) {
#if RGENGC_CHECK_MODE >= 5
        objspace->rgengc.error_count = data.err_count;
        gc_marks_check(objspace, NULL, NULL);
        allrefs_dump(objspace);
#endif
        rb_bug("gc_verify_internal_consistency: found internal inconsistency.");
    }

    /* check heap_page status */
    gc_verify_heap_pages(objspace);

    /* check counters */

    if (!is_lazy_sweeping(heap_eden) && !finalizing) {
        if (objspace_live_slots(objspace) != data.live_object_count) {
            fprintf(stderr, "heap_pages_final_slots: %d, objspace->profile.total_freed_objects: %d\n",
                    (int)heap_pages_final_slots, (int)objspace->profile.total_freed_objects);
            rb_bug("inconsistent live slot number: expect %"PRIuSIZE", but %"PRIuSIZE".", objspace_live_slots(objspace), data.live_object_count);
        }
    }

#if USE_RGENGC
    if (!is_marking(objspace)) {
        if (objspace->rgengc.old_objects != data.old_object_count) {
            rb_bug("inconsistent old slot number: expect %"PRIuSIZE", but %"PRIuSIZE".", objspace->rgengc.old_objects, data.old_object_count);
        }
        if (objspace->rgengc.uncollectible_wb_unprotected_objects != data.remembered_shady_count) {
            rb_bug("inconsistent old slot number: expect %"PRIuSIZE", but %"PRIuSIZE".", objspace->rgengc.uncollectible_wb_unprotected_objects, data.remembered_shady_count);
        }
    }
#endif

    if (!finalizing) {
        size_t list_count = 0;

        {
            VALUE z = heap_pages_deferred_final;
            while (z) {
                list_count++;
                z = RZOMBIE(z)->next;
            }
        }

        if (heap_pages_final_slots != data.zombie_object_count ||
            heap_pages_final_slots != list_count) {

            rb_bug("inconsistent finalizing object count:\n"
                   "  expect %"PRIuSIZE"\n"
                   "  but    %"PRIuSIZE" zombies\n"
                   "  heap_pages_deferred_final list has %"PRIuSIZE" items.",
                   heap_pages_final_slots,
                   data.zombie_object_count,
                   list_count);
        }
    }

    gc_report(5, objspace, "gc_verify_internal_consistency: OK\n");

    return Qnil;
}

Verify internal consistency.

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

verify_transient_heap_internal_consistency

gc.c View on GitHub

          
            static VALUE
gc_verify_transient_heap_internal_consistency(VALUE dmy)
{
    rb_transient_heap_verify();
    return Qnil;
}

No documentation available

Instance Methods

GC.start → nil

ObjectSpace.garbage_collect → nil

include GC; garbage_collect → nil

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

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

include GC; garbage_collect(full_mark: true, immediate_sweep: true) → nil

gc.c View on GitHub

          
            static VALUE
gc_start_internal(int argc, VALUE *argv, VALUE self)
{
    rb_objspace_t *objspace = &rb_objspace;
    int reason = GPR_FLAG_FULL_MARK | GPR_FLAG_IMMEDIATE_MARK |
                GPR_FLAG_IMMEDIATE_SWEEP | GPR_FLAG_METHOD;
    VALUE opt = Qnil;
    static ID keyword_ids[3];

    rb_scan_args(argc, argv, "0:", &opt);

    if (!NIL_P(opt)) {
        VALUE kwvals[3];

        if (!keyword_ids[0]) {
            keyword_ids[0] = rb_intern("full_mark");
            keyword_ids[1] = rb_intern("immediate_mark");
            keyword_ids[2] = rb_intern("immediate_sweep");
        }

        rb_get_kwargs(opt, keyword_ids, 0, 3, kwvals);

        if (kwvals[0] != Qundef && !RTEST(kwvals[0])) {
            reason &= ~GPR_FLAG_FULL_MARK;
        }
        if (kwvals[1] != Qundef && !RTEST(kwvals[1])) {
            reason &= ~GPR_FLAG_IMMEDIATE_MARK;
        }
        if (kwvals[2] != Qundef && !RTEST(kwvals[2])) {
            reason &= ~GPR_FLAG_IMMEDIATE_SWEEP;
        }
    }

    garbage_collect(objspace, reason);
    gc_finalize_deferred(objspace);

    return Qnil;
}

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.