Memory management control and statistics; finalised values.
module Stat : sig .. end
type t = {
minor_words : float;
Number of words allocated in the minor heap since the program was started. This number is accurate in byte-code programs, but only an approximation in programs compiled to native code.
promoted_words : float;
Number of words allocated in the minor heap that survived a minor collection and were moved to the major heap since the program was started.
major_words : float;
Number of words allocated in the major heap, including the promoted words, since the program was started.
minor_collections : int;
Number of minor collections since the program was started.
major_collections : int;
Number of major collection cycles completed since the program was started.
heap_words : int;
Total size of the major heap, in words.
heap_chunks : int;
Number of contiguous pieces of memory that make up the major heap.
live_words : int;
Number of words of live data in the major heap, including the header words.
live_blocks : int;
Number of live blocks in the major heap.
free_words : int;
Number of words in the free list.
free_blocks : int;
Number of blocks in the free list.
largest_free : int;
Size (in words) of the largest block in the free list.
fragments : int;
Number of wasted words due to fragmentation. These are 1-words free blocks placed between two live blocks. They are not available for allocation.
compactions : int;
Number of heap compactions since the program was started.
top_heap_words : int;
Maximum size reached by the major heap, in words.
stack_size : int;
Current size of the stack, in words.
}
val stack_size : t -> int
val top_heap_words : t -> int
val compactions : t -> int
val fragments : t -> int
val largest_free : t -> int
val free_blocks : t -> int
val free_words : t -> int
val live_blocks : t -> int
val live_words : t -> int
val heap_chunks : t -> int
val heap_words : t -> int
val major_collections : t -> int
val minor_collections : t -> int
val major_words : t -> float
val promoted_words : t -> float
val minor_words : t -> float
module Fields : sig .. end
val names : string list
val stack_size : (t, int) Fieldslib.Field.t
val top_heap_words : (t, int) Fieldslib.Field.t
val compactions : (t, int) Fieldslib.Field.t
val fragments : (t, int) Fieldslib.Field.t
val largest_free : (t, int) Fieldslib.Field.t
val free_blocks : (t, int) Fieldslib.Field.t
val free_words : (t, int) Fieldslib.Field.t
val live_blocks : (t, int) Fieldslib.Field.t
val live_words : (t, int) Fieldslib.Field.t
val heap_chunks : (t, int) Fieldslib.Field.t
val heap_words : (t, int) Fieldslib.Field.t
val major_collections : (t, int) Fieldslib.Field.t
val minor_collections : (t, int) Fieldslib.Field.t
val major_words : (t, float) Fieldslib.Field.t
val promoted_words : (t, float) Fieldslib.Field.t
val minor_words : (t, float) Fieldslib.Field.t
val fold : init:'acc__ ->
minor_words:('acc__ -> (t, float) Fieldslib.Field.t -> 'acc__) ->
promoted_words:('acc__ -> (t, float) Fieldslib.Field.t -> 'acc__) ->
major_words:('acc__ -> (t, float) Fieldslib.Field.t -> 'acc__) ->
minor_collections:('acc__ -> (t, int) Fieldslib.Field.t -> 'acc__) ->
major_collections:('acc__ -> (t, int) Fieldslib.Field.t -> 'acc__) ->
heap_words:('acc__ -> (t, int) Fieldslib.Field.t -> 'acc__) ->
heap_chunks:('acc__ -> (t, int) Fieldslib.Field.t -> 'acc__) ->
live_words:('acc__ -> (t, int) Fieldslib.Field.t -> 'acc__) ->
live_blocks:('acc__ -> (t, int) Fieldslib.Field.t -> 'acc__) ->
free_words:('acc__ -> (t, int) Fieldslib.Field.t -> 'acc__) ->
free_blocks:('acc__ -> (t, int) Fieldslib.Field.t -> 'acc__) ->
largest_free:('acc__ -> (t, int) Fieldslib.Field.t -> 'acc__) ->
fragments:('acc__ -> (t, int) Fieldslib.Field.t -> 'acc__) ->
compactions:('acc__ -> (t, int) Fieldslib.Field.t -> 'acc__) ->
top_heap_words:('acc__ -> (t, int) Fieldslib.Field.t -> 'acc__) ->
stack_size:('acc__ -> (t, int) Fieldslib.Field.t -> 'acc__) -> 'acc__
val make_creator : minor_words:((t, float) Fieldslib.Field.t ->
             'compile_acc__ -> ('input__ -> float) * 'compile_acc__) ->
promoted_words:((t, float) Fieldslib.Field.t ->
                'compile_acc__ -> ('input__ -> float) * 'compile_acc__) ->
major_words:((t, float) Fieldslib.Field.t ->
             'compile_acc__ -> ('input__ -> float) * 'compile_acc__) ->
minor_collections:((t, int) Fieldslib.Field.t ->
                   'compile_acc__ -> ('input__ -> int) * 'compile_acc__) ->
major_collections:((t, int) Fieldslib.Field.t ->
                   'compile_acc__ -> ('input__ -> int) * 'compile_acc__) ->
heap_words:((t, int) Fieldslib.Field.t ->
            'compile_acc__ -> ('input__ -> int) * 'compile_acc__) ->
heap_chunks:((t, int) Fieldslib.Field.t ->
             'compile_acc__ -> ('input__ -> int) * 'compile_acc__) ->
live_words:((t, int) Fieldslib.Field.t ->
            'compile_acc__ -> ('input__ -> int) * 'compile_acc__) ->
live_blocks:((t, int) Fieldslib.Field.t ->
             'compile_acc__ -> ('input__ -> int) * 'compile_acc__) ->
free_words:((t, int) Fieldslib.Field.t ->
            'compile_acc__ -> ('input__ -> int) * 'compile_acc__) ->
free_blocks:((t, int) Fieldslib.Field.t ->
             'compile_acc__ -> ('input__ -> int) * 'compile_acc__) ->
largest_free:((t, int) Fieldslib.Field.t ->
              'compile_acc__ -> ('input__ -> int) * 'compile_acc__) ->
fragments:((t, int) Fieldslib.Field.t ->
           'compile_acc__ -> ('input__ -> int) * 'compile_acc__) ->
compactions:((t, int) Fieldslib.Field.t ->
             'compile_acc__ -> ('input__ -> int) * 'compile_acc__) ->
top_heap_words:((t, int) Fieldslib.Field.t ->
                'compile_acc__ -> ('input__ -> int) * 'compile_acc__) ->
stack_size:((t, int) Fieldslib.Field.t ->
            'compile_acc__ -> ('input__ -> int) * 'compile_acc__) ->
'compile_acc__ -> ('input__ -> t) * 'compile_acc__
val create : minor_words:float ->
promoted_words:float ->
major_words:float ->
minor_collections:int ->
major_collections:int ->
heap_words:int ->
heap_chunks:int ->
live_words:int ->
live_blocks:int ->
free_words:int ->
free_blocks:int ->
largest_free:int ->
fragments:int -> compactions:int -> top_heap_words:int -> stack_size:int -> t
val map : minor_words:((t, float) Fieldslib.Field.t -> float) ->
promoted_words:((t, float) Fieldslib.Field.t -> float) ->
major_words:((t, float) Fieldslib.Field.t -> float) ->
minor_collections:((t, int) Fieldslib.Field.t -> int) ->
major_collections:((t, int) Fieldslib.Field.t -> int) ->
heap_words:((t, int) Fieldslib.Field.t -> int) ->
heap_chunks:((t, int) Fieldslib.Field.t -> int) ->
live_words:((t, int) Fieldslib.Field.t -> int) ->
live_blocks:((t, int) Fieldslib.Field.t -> int) ->
free_words:((t, int) Fieldslib.Field.t -> int) ->
free_blocks:((t, int) Fieldslib.Field.t -> int) ->
largest_free:((t, int) Fieldslib.Field.t -> int) ->
fragments:((t, int) Fieldslib.Field.t -> int) ->
compactions:((t, int) Fieldslib.Field.t -> int) ->
top_heap_words:((t, int) Fieldslib.Field.t -> int) ->
stack_size:((t, int) Fieldslib.Field.t -> int) -> t
val iter : minor_words:((t, float) Fieldslib.Field.t -> unit) ->
promoted_words:((t, float) Fieldslib.Field.t -> unit) ->
major_words:((t, float) Fieldslib.Field.t -> unit) ->
minor_collections:((t, int) Fieldslib.Field.t -> unit) ->
major_collections:((t, int) Fieldslib.Field.t -> unit) ->
heap_words:((t, int) Fieldslib.Field.t -> unit) ->
heap_chunks:((t, int) Fieldslib.Field.t -> unit) ->
live_words:((t, int) Fieldslib.Field.t -> unit) ->
live_blocks:((t, int) Fieldslib.Field.t -> unit) ->
free_words:((t, int) Fieldslib.Field.t -> unit) ->
free_blocks:((t, int) Fieldslib.Field.t -> unit) ->
largest_free:((t, int) Fieldslib.Field.t -> unit) ->
fragments:((t, int) Fieldslib.Field.t -> unit) ->
compactions:((t, int) Fieldslib.Field.t -> unit) ->
top_heap_words:((t, int) Fieldslib.Field.t -> unit) ->
stack_size:((t, int) Fieldslib.Field.t -> unit) -> unit
val for_all : minor_words:((t, float) Fieldslib.Field.t -> bool) ->
promoted_words:((t, float) Fieldslib.Field.t -> bool) ->
major_words:((t, float) Fieldslib.Field.t -> bool) ->
minor_collections:((t, int) Fieldslib.Field.t -> bool) ->
major_collections:((t, int) Fieldslib.Field.t -> bool) ->
heap_words:((t, int) Fieldslib.Field.t -> bool) ->
heap_chunks:((t, int) Fieldslib.Field.t -> bool) ->
live_words:((t, int) Fieldslib.Field.t -> bool) ->
live_blocks:((t, int) Fieldslib.Field.t -> bool) ->
free_words:((t, int) Fieldslib.Field.t -> bool) ->
free_blocks:((t, int) Fieldslib.Field.t -> bool) ->
largest_free:((t, int) Fieldslib.Field.t -> bool) ->
fragments:((t, int) Fieldslib.Field.t -> bool) ->
compactions:((t, int) Fieldslib.Field.t -> bool) ->
top_heap_words:((t, int) Fieldslib.Field.t -> bool) ->
stack_size:((t, int) Fieldslib.Field.t -> bool) -> bool
val exists : minor_words:((t, float) Fieldslib.Field.t -> bool) ->
promoted_words:((t, float) Fieldslib.Field.t -> bool) ->
major_words:((t, float) Fieldslib.Field.t -> bool) ->
minor_collections:((t, int) Fieldslib.Field.t -> bool) ->
major_collections:((t, int) Fieldslib.Field.t -> bool) ->
heap_words:((t, int) Fieldslib.Field.t -> bool) ->
heap_chunks:((t, int) Fieldslib.Field.t -> bool) ->
live_words:((t, int) Fieldslib.Field.t -> bool) ->
live_blocks:((t, int) Fieldslib.Field.t -> bool) ->
free_words:((t, int) Fieldslib.Field.t -> bool) ->
free_blocks:((t, int) Fieldslib.Field.t -> bool) ->
largest_free:((t, int) Fieldslib.Field.t -> bool) ->
fragments:((t, int) Fieldslib.Field.t -> bool) ->
compactions:((t, int) Fieldslib.Field.t -> bool) ->
top_heap_words:((t, int) Fieldslib.Field.t -> bool) ->
stack_size:((t, int) Fieldslib.Field.t -> bool) -> bool
val to_list : minor_words:((t, float) Fieldslib.Field.t -> 'elem__) ->
promoted_words:((t, float) Fieldslib.Field.t -> 'elem__) ->
major_words:((t, float) Fieldslib.Field.t -> 'elem__) ->
minor_collections:((t, int) Fieldslib.Field.t -> 'elem__) ->
major_collections:((t, int) Fieldslib.Field.t -> 'elem__) ->
heap_words:((t, int) Fieldslib.Field.t -> 'elem__) ->
heap_chunks:((t, int) Fieldslib.Field.t -> 'elem__) ->
live_words:((t, int) Fieldslib.Field.t -> 'elem__) ->
live_blocks:((t, int) Fieldslib.Field.t -> 'elem__) ->
free_words:((t, int) Fieldslib.Field.t -> 'elem__) ->
free_blocks:((t, int) Fieldslib.Field.t -> 'elem__) ->
largest_free:((t, int) Fieldslib.Field.t -> 'elem__) ->
fragments:((t, int) Fieldslib.Field.t -> 'elem__) ->
compactions:((t, int) Fieldslib.Field.t -> 'elem__) ->
top_heap_words:((t, int) Fieldslib.Field.t -> 'elem__) ->
stack_size:((t, int) Fieldslib.Field.t -> 'elem__) -> 'elem__ list
val map_poly : ([< `Read | `Set_and_create ], t, 'x0) Fieldslib.Field.user -> 'x0 list
module Direct : sig .. end
val iter : t ->
minor_words:((t, float) Fieldslib.Field.t -> t -> float -> unit) ->
promoted_words:((t, float) Fieldslib.Field.t -> t -> float -> unit) ->
major_words:((t, float) Fieldslib.Field.t -> t -> float -> unit) ->
minor_collections:((t, int) Fieldslib.Field.t -> t -> int -> unit) ->
major_collections:((t, int) Fieldslib.Field.t -> t -> int -> unit) ->
heap_words:((t, int) Fieldslib.Field.t -> t -> int -> unit) ->
heap_chunks:((t, int) Fieldslib.Field.t -> t -> int -> unit) ->
live_words:((t, int) Fieldslib.Field.t -> t -> int -> unit) ->
live_blocks:((t, int) Fieldslib.Field.t -> t -> int -> unit) ->
free_words:((t, int) Fieldslib.Field.t -> t -> int -> unit) ->
free_blocks:((t, int) Fieldslib.Field.t -> t -> int -> unit) ->
largest_free:((t, int) Fieldslib.Field.t -> t -> int -> unit) ->
fragments:((t, int) Fieldslib.Field.t -> t -> int -> unit) ->
compactions:((t, int) Fieldslib.Field.t -> t -> int -> unit) ->
top_heap_words:((t, int) Fieldslib.Field.t -> t -> int -> unit) ->
stack_size:((t, int) Fieldslib.Field.t -> t -> int -> unit) -> unit
val fold : t ->
init:'acc__ ->
minor_words:('acc__ -> (t, float) Fieldslib.Field.t -> t -> float -> 'acc__) ->
promoted_words:('acc__ ->
                (t, float) Fieldslib.Field.t -> t -> float -> 'acc__) ->
major_words:('acc__ -> (t, float) Fieldslib.Field.t -> t -> float -> 'acc__) ->
minor_collections:('acc__ -> (t, int) Fieldslib.Field.t -> t -> int -> 'acc__) ->
major_collections:('acc__ -> (t, int) Fieldslib.Field.t -> t -> int -> 'acc__) ->
heap_words:('acc__ -> (t, int) Fieldslib.Field.t -> t -> int -> 'acc__) ->
heap_chunks:('acc__ -> (t, int) Fieldslib.Field.t -> t -> int -> 'acc__) ->
live_words:('acc__ -> (t, int) Fieldslib.Field.t -> t -> int -> 'acc__) ->
live_blocks:('acc__ -> (t, int) Fieldslib.Field.t -> t -> int -> 'acc__) ->
free_words:('acc__ -> (t, int) Fieldslib.Field.t -> t -> int -> 'acc__) ->
free_blocks:('acc__ -> (t, int) Fieldslib.Field.t -> t -> int -> 'acc__) ->
largest_free:('acc__ -> (t, int) Fieldslib.Field.t -> t -> int -> 'acc__) ->
fragments:('acc__ -> (t, int) Fieldslib.Field.t -> t -> int -> 'acc__) ->
compactions:('acc__ -> (t, int) Fieldslib.Field.t -> t -> int -> 'acc__) ->
top_heap_words:('acc__ -> (t, int) Fieldslib.Field.t -> t -> int -> 'acc__) ->
stack_size:('acc__ -> (t, int) Fieldslib.Field.t -> t -> int -> 'acc__) ->
'acc__
val t_of_sexp : Sexplib.Sexp.t -> t
val sexp_of_t : t -> Sexplib.Sexp.t
val bin_t : t Bin_prot.Type_class.t
val bin_read_t : t Bin_prot.Read.reader
val __bin_read_t__ : (int -> t) Bin_prot.Read.reader
val bin_reader_t : t Bin_prot.Type_class.reader
val bin_size_t : t Bin_prot.Size.sizer
val bin_write_t : t Bin_prot.Write.writer
val bin_writer_t : t Bin_prot.Type_class.writer
type stat = Stat.t
The memory management counters are returned in a stat record.

The total amount of memory allocated by the program since it was started is (in words) minor_words + major_words - promoted_words. Multiply by the word size (4 on a 32-bit machine, 8 on a 64-bit machine) to get the number of bytes.

module Control : sig .. end
type t = {
mutable minor_heap_size : int;
The size (in words) of the minor heap. Changing this parameter will trigger a minor collection. Default: 1M.
mutable major_heap_increment : int;
The minimum number of words to add to the major heap when increasing it. Default: 1M.
mutable space_overhead : int;
The major GC speed is computed from this parameter. This is the memory that will be "wasted" because the GC does not immediatly collect unreachable blocks. It is expressed as a percentage of the memory used for live data. The GC will work more (use more CPU time and collect blocks more eagerly) if space_overhead is smaller. Default: 100.
mutable verbose : int;
This value controls the GC messages on standard error output. It is a sum of some of the following flags, to print messages on the corresponding events:
  • 0x001 Start of major GC cycle.
  • 0x002 Minor collection and major GC slice.
  • 0x004 Growing and shrinking of the heap.
  • 0x008 Resizing of stacks and memory manager tables.
  • 0x010 Heap compaction.
  • 0x020 Change of GC parameters.
  • 0x040 Computation of major GC slice size.
  • 0x080 Calling of finalisation functions.
  • 0x100 Bytecode executable search at start-up.
  • 0x200 Computation of compaction triggering condition. Default: 0.
mutable max_overhead : int;
Heap compaction is triggered when the estimated amount of "wasted" memory is more than max_overhead percent of the amount of live data. If max_overhead is set to 0, heap compaction is triggered at the end of each major GC cycle (this setting is intended for testing purposes only). If max_overhead >= 1000000, compaction is never triggered. Default: 500.
mutable stack_limit : int;
The maximum size of the stack (in words). This is only relevant to the byte-code runtime, as the native code runtime uses the operating system's stack. Default: 256k.
mutable allocation_policy : int;
The policy used for allocating in the heap. Possible values are 0 and 1. 0 is the next-fit policy, which is quite fast but can result in fragmentation. 1 is the first-fit policy, which can be slower in some cases but can be better for programs with fragmentation problems. Default: 0.
}
val allocation_policy : t -> int
val set_allocation_policy : t -> int -> unit
val stack_limit : t -> int
val set_stack_limit : t -> int -> unit
val max_overhead : t -> int
val set_max_overhead : t -> int -> unit
val verbose : t -> int
val set_verbose : t -> int -> unit
val space_overhead : t -> int
val set_space_overhead : t -> int -> unit
val major_heap_increment : t -> int
val set_major_heap_increment : t -> int -> unit
val minor_heap_size : t -> int
val set_minor_heap_size : t -> int -> unit
module Fields : sig .. end
val names : string list
val allocation_policy : (t, int) Fieldslib.Field.t
val stack_limit : (t, int) Fieldslib.Field.t
val max_overhead : (t, int) Fieldslib.Field.t
val verbose : (t, int) Fieldslib.Field.t
val space_overhead : (t, int) Fieldslib.Field.t
val major_heap_increment : (t, int) Fieldslib.Field.t
val minor_heap_size : (t, int) Fieldslib.Field.t
val fold : init:'acc__ ->
minor_heap_size:('acc__ -> (t, int) Fieldslib.Field.t -> 'acc__) ->
major_heap_increment:('acc__ -> (t, int) Fieldslib.Field.t -> 'acc__) ->
space_overhead:('acc__ -> (t, int) Fieldslib.Field.t -> 'acc__) ->
verbose:('acc__ -> (t, int) Fieldslib.Field.t -> 'acc__) ->
max_overhead:('acc__ -> (t, int) Fieldslib.Field.t -> 'acc__) ->
stack_limit:('acc__ -> (t, int) Fieldslib.Field.t -> 'acc__) ->
allocation_policy:('acc__ -> (t, int) Fieldslib.Field.t -> 'acc__) -> 'acc__
val make_creator : minor_heap_size:((t, int) Fieldslib.Field.t ->
                 'compile_acc__ -> ('input__ -> int) * 'compile_acc__) ->
major_heap_increment:((t, int) Fieldslib.Field.t ->
                      'compile_acc__ -> ('input__ -> int) * 'compile_acc__) ->
space_overhead:((t, int) Fieldslib.Field.t ->
                'compile_acc__ -> ('input__ -> int) * 'compile_acc__) ->
verbose:((t, int) Fieldslib.Field.t ->
         'compile_acc__ -> ('input__ -> int) * 'compile_acc__) ->
max_overhead:((t, int) Fieldslib.Field.t ->
              'compile_acc__ -> ('input__ -> int) * 'compile_acc__) ->
stack_limit:((t, int) Fieldslib.Field.t ->
             'compile_acc__ -> ('input__ -> int) * 'compile_acc__) ->
allocation_policy:((t, int) Fieldslib.Field.t ->
                   'compile_acc__ -> ('input__ -> int) * 'compile_acc__) ->
'compile_acc__ -> ('input__ -> t) * 'compile_acc__
val create : minor_heap_size:int ->
major_heap_increment:int ->
space_overhead:int ->
verbose:int ->
max_overhead:int -> stack_limit:int -> allocation_policy:int -> t
val map : minor_heap_size:((t, int) Fieldslib.Field.t -> int) ->
major_heap_increment:((t, int) Fieldslib.Field.t -> int) ->
space_overhead:((t, int) Fieldslib.Field.t -> int) ->
verbose:((t, int) Fieldslib.Field.t -> int) ->
max_overhead:((t, int) Fieldslib.Field.t -> int) ->
stack_limit:((t, int) Fieldslib.Field.t -> int) ->
allocation_policy:((t, int) Fieldslib.Field.t -> int) -> t
val iter : minor_heap_size:((t, int) Fieldslib.Field.t -> unit) ->
major_heap_increment:((t, int) Fieldslib.Field.t -> unit) ->
space_overhead:((t, int) Fieldslib.Field.t -> unit) ->
verbose:((t, int) Fieldslib.Field.t -> unit) ->
max_overhead:((t, int) Fieldslib.Field.t -> unit) ->
stack_limit:((t, int) Fieldslib.Field.t -> unit) ->
allocation_policy:((t, int) Fieldslib.Field.t -> unit) -> unit
val for_all : minor_heap_size:((t, int) Fieldslib.Field.t -> bool) ->
major_heap_increment:((t, int) Fieldslib.Field.t -> bool) ->
space_overhead:((t, int) Fieldslib.Field.t -> bool) ->
verbose:((t, int) Fieldslib.Field.t -> bool) ->
max_overhead:((t, int) Fieldslib.Field.t -> bool) ->
stack_limit:((t, int) Fieldslib.Field.t -> bool) ->
allocation_policy:((t, int) Fieldslib.Field.t -> bool) -> bool
val exists : minor_heap_size:((t, int) Fieldslib.Field.t -> bool) ->
major_heap_increment:((t, int) Fieldslib.Field.t -> bool) ->
space_overhead:((t, int) Fieldslib.Field.t -> bool) ->
verbose:((t, int) Fieldslib.Field.t -> bool) ->
max_overhead:((t, int) Fieldslib.Field.t -> bool) ->
stack_limit:((t, int) Fieldslib.Field.t -> bool) ->
allocation_policy:((t, int) Fieldslib.Field.t -> bool) -> bool
val to_list : minor_heap_size:((t, int) Fieldslib.Field.t -> 'elem__) ->
major_heap_increment:((t, int) Fieldslib.Field.t -> 'elem__) ->
space_overhead:((t, int) Fieldslib.Field.t -> 'elem__) ->
verbose:((t, int) Fieldslib.Field.t -> 'elem__) ->
max_overhead:((t, int) Fieldslib.Field.t -> 'elem__) ->
stack_limit:((t, int) Fieldslib.Field.t -> 'elem__) ->
allocation_policy:((t, int) Fieldslib.Field.t -> 'elem__) -> 'elem__ list
val map_poly : ([< `Read | `Set_and_create ], t, 'x0) Fieldslib.Field.user -> 'x0 list
module Direct : sig .. end
val iter : t ->
minor_heap_size:((t, int) Fieldslib.Field.t -> t -> int -> unit) ->
major_heap_increment:((t, int) Fieldslib.Field.t -> t -> int -> unit) ->
space_overhead:((t, int) Fieldslib.Field.t -> t -> int -> unit) ->
verbose:((t, int) Fieldslib.Field.t -> t -> int -> unit) ->
max_overhead:((t, int) Fieldslib.Field.t -> t -> int -> unit) ->
stack_limit:((t, int) Fieldslib.Field.t -> t -> int -> unit) ->
allocation_policy:((t, int) Fieldslib.Field.t -> t -> int -> unit) -> unit
val fold : t ->
init:'acc__ ->
minor_heap_size:('acc__ -> (t, int) Fieldslib.Field.t -> t -> int -> 'acc__) ->
major_heap_increment:('acc__ ->
                      (t, int) Fieldslib.Field.t -> t -> int -> 'acc__) ->
space_overhead:('acc__ -> (t, int) Fieldslib.Field.t -> t -> int -> 'acc__) ->
verbose:('acc__ -> (t, int) Fieldslib.Field.t -> t -> int -> 'acc__) ->
max_overhead:('acc__ -> (t, int) Fieldslib.Field.t -> t -> int -> 'acc__) ->
stack_limit:('acc__ -> (t, int) Fieldslib.Field.t -> t -> int -> 'acc__) ->
allocation_policy:('acc__ -> (t, int) Fieldslib.Field.t -> t -> int -> 'acc__) ->
'acc__
val t_of_sexp : Sexplib.Sexp.t -> t
val sexp_of_t : t -> Sexplib.Sexp.t
val bin_t : t Bin_prot.Type_class.t
val bin_read_t : t Bin_prot.Read.reader
val __bin_read_t__ : (int -> t) Bin_prot.Read.reader
val bin_reader_t : t Bin_prot.Type_class.reader
val bin_size_t : t Bin_prot.Size.sizer
val bin_write_t : t Bin_prot.Write.writer
val bin_writer_t : t Bin_prot.Type_class.writer
type control = Control.t
The GC parameters are given as a control record. Note that these parameters can also be initialised by setting the OCAMLRUNPARAM environment variable. See the documentation of ocamlrun.
val stat : unit -> stat
Return the current values of the memory management counters in a stat record. This function examines every heap block to get the statistics.
val quick_stat : unit -> stat
Same as stat except that live_words, live_blocks, free_words, free_blocks, largest_free, and fragments are set to 0. This function is much faster than stat because it does not need to go through the heap.
val counters : unit -> float * float * float
Return (minor_words, promoted_words, major_words). This function is as fast at quick_stat.
val minor_words : unit -> int
The following functions return the same as (Gc.quick_stat ()).Stat.f, avoiding any allocation (of the stat record or a float). On 32-bit machines the int may overflow.
val major_words : unit -> int
val promoted_words : unit -> int
val minor_collections : unit -> int
val major_collections : unit -> int
val heap_words : unit -> int
val heap_chunks : unit -> int
val compactions : unit -> int
val top_heap_words : unit -> int
val get : unit -> control
Return the current values of the GC parameters in a control record.
val set : control -> unit
set r changes the GC parameters according to the control record r. The normal usage is: Gc.set { (Gc.get()) with Gc.Control.verbose = 0x00d }
val minor : unit -> unit
Trigger a minor collection.
val major_slice : int -> int
Do a minor collection and a slice of major collection. The argument is the size of the slice, 0 to use the automatically-computed slice size. In all cases, the result is the computed slice size.
val major : unit -> unit
Do a minor collection and finish the current major collection cycle.
val full_major : unit -> unit
Do a minor collection, finish the current major collection cycle, and perform a complete new cycle. This will collect all currently unreachable blocks.
val compact : unit -> unit
Perform a full major collection and compact the heap. Note that heap compaction is a lengthy operation.
val print_stat : out_channel -> unit
Print the current values of the memory management counters (in human-readable form) into the channel argument.
val allocated_bytes : unit -> float
Return the total number of bytes allocated since the program was started. It is returned as a float to avoid overflow problems with int on 32-bit machines.
val keep_alive : 'a -> unit
type alarm
An alarm is a piece of data that calls a user function at the end of each major GC cycle. The following functions are provided to create and delete alarms.
val create_alarm : (unit -> unit) -> alarm
create_alarm f will arrange for f to be called at the end of each major GC cycle, starting with the current cycle or the next one. A value of type alarm is returned that you can use to call delete_alarm.
val delete_alarm : alarm -> unit
delete_alarm a will stop the calls to the function associated to a. Calling delete_alarm a again has no effect.
val tune : ?logger:(string -> unit) ->
?minor_heap_size:int ->
?major_heap_increment:int ->
?space_overhead:int ->
?verbose:int ->
?max_overhead:int ->
?stack_limit:int -> ?allocation_policy:int -> unit -> unit
Adjust the specified GC parameters.
module Expert : sig .. end
The Expert module contains functions that novice users should not use, due to their complexity.

In particular, finalizers are difficult to use correctly, because they can run at any time, even in the middle of other code, and because unhandled exceptions in a finalizer can be raised at any point in other code. This introduces all the semantic complexities of multithreading, which is usually a bad idea. It is much easier to use async finalizers, see Async_core.Async_gc.add_finalizer, which do not involve multithreading, and runs user code as ordinary async jobs.

If you do use Core finalizers, you should strive to make the finalization function perform a simple idempotent action, like setting a ref. The same rules as for signal handlers apply to finalizers.

val add_finalizer : 'a Heap_block.t -> ('a Heap_block.t -> unit) -> unit
add_finalizer b f ensures that f runs after b becomes unreachable. The OCaml runtime only supports finalizers on heap blocks, hence add_finalizer requires b : _ Heap_block.t. The runtime essentially maintains a set of finalizer pairs:
        'a Heap_block.t * ('a Heap_block.t -> unit)

Each call to add_finalizer adds a new pair to the set. It is allowed for many pairs to have the same heap block, the same function, or both. Each pair is a distinct element of the set.

After a garbage collection determines that a heap block b is unreachable, it removes from the set of finalizers all finalizer pairs (b, f) whose block is b, and then and runs f b for all such pairs. Thus, a finalizer registered with add_finalizer will run at most once.

The GC will call the finalisation functions in the order of deallocation. When several values become unreachable at the same time (i.e. during the same GC cycle), the finalisation functions will be called in the reverse order of the corresponding calls to add_finalizer. If add_finalizer is called in the same order as the values are allocated, that means each value is finalised before the values it depends upon. Of course, this becomes false if additional dependencies are introduced by assignments.

In a finalizer pair (b, f), it is a mistake for the closure of f to reference (directly or indirectly) b -- f should only access b via its argument. Referring to b in any other way will cause b to be kept alive forever, since f itself is a root of garbage collection, and can itself only be collected after the pair (b, f) is removed from the set of finalizers.

The f function can use all features of OCaml, including assignments that make the value reachable again. It can also loop forever (in this case, the other finalisation functions will be called during the execution of f). It can call add_finalizer on v or other values to register other functions or even itself. It can raise an exception; in this case the exception will interrupt whatever the program was doing when the function was called. This is very hard to think about, so one should take care to make f not raise.

add_finalizer_exn b f is like add_finalizer, but will raise if b is not a heap block.

val add_finalizer_exn : 'a -> ('a -> unit) -> unit
val finalize_release : unit -> unit
The runtime essentially maintains a bool ref:
        val finalizer_is_running : bool ref

The runtime uses this bool ref to ensure that only one finalizer is running at a time, by setting it to true when a finalizer starts and setting it to false when a finalizer finishes. The runtime will not start running a finalizer if !finalizer_is_running = true. Calling finalize_release essentially does finalizer_is_running := false, which allows another finalizer to start whether or not the current finalizer finishes.