142 lines
6.8 KiB
OCaml
142 lines
6.8 KiB
OCaml
(***********************************************************************)
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(* *)
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(* Objective Caml *)
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(* *)
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(* Damien Doligez, projet Para, INRIA Rocquencourt *)
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(* *)
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(* Copyright 1996 Institut National de Recherche en Informatique et *)
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(* en Automatique. All rights reserved. This file is distributed *)
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(* under the terms of the GNU Library General Public License. *)
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(* *)
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(***********************************************************************)
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(* $Id$ *)
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(* Module [Gc]: memory management control and statistics *)
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type stat = {
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minor_words : int;
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promoted_words : int;
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major_words : int;
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minor_collections : int;
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major_collections : int;
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heap_words : int;
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heap_chunks : int;
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live_words : int;
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live_blocks : int;
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free_words : int;
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free_blocks : int;
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largest_free : int;
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fragments : int;
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compactions : int
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}
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(* The memory management counters are returned in a [stat] record.
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The fields of this record are:
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- [minor_words] Number of words allocated in the minor heap since
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the program was started.
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- [promoted_words] Number of words allocated in the minor heap that
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survived a minor collection and were moved to the major heap
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since the program was started.
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- [major_words] Number of words allocated in the major heap, including
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the promoted words, since the program was started.
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- [minor_collections] Number of minor collections since the program
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was started.
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- [major_collections] Number of major collection cycles, not counting
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the current cycle, since the program was started.
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- [heap_words] Total size of the major heap, in words.
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- [heap_chunks] Number of times the major heap size was increased
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since the program was started (including the initial allocation
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of the heap).
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- [live_words] Number of words of live data in the major heap, including
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the header words.
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- [live_blocks] Number of live blocks in the major heap.
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- [free_words] Number of words in the free list.
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- [free_blocks] Number of blocks in the free list.
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- [largest_free] Size (in words) of the largest block in the free list.
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- [fragments] Number of wasted words due to fragmentation. These are
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1-words free blocks placed between two live blocks. They
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cannot be inserted in the free list, thus they are not available
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for allocation.
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- [compactions] Number of heap compactions since the program was started.
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The total amount of memory allocated by the program since it was started
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is (in words) [minor_words + major_words - promoted_words]. Multiply by
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the word size (4 on a 32-bit machine, 8 on a 64-bit machine) to get
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the number of bytes.
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*)
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type control = {
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mutable minor_heap_size : int;
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mutable major_heap_increment : int;
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mutable space_overhead : int;
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mutable verbose : int;
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mutable max_overhead : int;
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mutable stack_limit : int
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}
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(* The GC parameters are given as a [control] record. The fields are:
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- [minor_heap_size] The size (in words) of the minor heap. Changing
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this parameter will trigger a minor collection. Default: 32k.
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- [major_heap_increment] The minimum number of words to add to the
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major heap when increasing it. Default: 62k.
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- [space_overhead] The major GC speed is computed from this parameter.
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This is the memory that will be "wasted" because the GC does not
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immediatly collect unreachable blocks. It is expressed as a
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percentage of the memory used for live data.
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The GC will work more (use more CPU time and collect
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blocks more eagerly) if [space_overhead] is smaller.
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The computation of the GC speed assumes that the amount
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of live data is constant. Default: 42.
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- [max_overhead] Heap compaction is triggered when the estimated amount
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of free memory is more than [max_overhead] percent of the amount
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of live data. If [max_overhead] is set to 0, heap
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compaction is triggered at the end of each major GC cycle
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(this setting is intended for testing purposes only).
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If [max_overhead >= 1000000], compaction is never triggered.
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Default: 1000000.
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- [verbose] This value controls the GC messages on standard error output.
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It is a sum of some of the following flags, to print messages
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on the corresponding events:
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- [1 ] Start of major GC cycle.
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- [2 ] Minor collection and major GC slice.
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- [4 ] Growing and shrinking of the heap.
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- [8 ] Resizing of stacks and memory manager tables.
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- [16] Heap compaction.
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- [32] Change of GC parameters.
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- [64] Computation of major GC slice size.
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Default: 0.
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- [stack_limit] The maximum size of the stack (in words). This is only
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relevant to the byte-code runtime, as the native code runtime
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uses the operating system's stack. Default: 256k.
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*)
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external stat : unit -> stat = "gc_stat"
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(* Return the current values of the memory management counters in a
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[stat] record. *)
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external counters : unit -> (int * int * int) = "gc_counters"
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(* Return [(minor_words, promoted_words, major_words)]. Much faster
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than [stat]. *)
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external get : unit -> control = "gc_get"
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(* Return the current values of the GC parameters in a [control] record. *)
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external set : control -> unit = "gc_set"
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(* [set r] changes the GC parameters according to the [control] record [r].
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The normal usage is: [ Gc.set { (Gc.get()) with Gc.verbose = 13 } ]. *)
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external minor : unit -> unit = "gc_minor"
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(* Trigger a minor collection. *)
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external major : unit -> unit = "gc_major"
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(* Finish the current major collection cycle. *)
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external full_major : unit -> unit = "gc_full_major"
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(* Finish the current major collection cycle and perform a complete
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new cycle. This will collect all currently unreachable blocks. *)
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external compact : unit -> unit = "gc_compaction";;
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(* Perform a full major collection and compact the heap. Note that heap
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compaction is a lengthy operation. *)
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val print_stat : out_channel -> unit
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(* Print the current values of the memory management counters (in
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human-readable form) into the channel argument. *)
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val allocated_bytes : unit -> int
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(* Return the total number of bytes allocated since the program was
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started. *)
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