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gc_ctrl.c

/***********************************************************************/
/*                                                                     */
/*                           Objective Caml                            */
/*                                                                     */
/*             Damien Doligez, projet Para, INRIA Rocquencourt         */
/*                                                                     */
/*  Copyright 1996 Institut National de Recherche en Informatique et   */
/*  en Automatique.  All rights reserved.  This file is distributed    */
/*  under the terms of the GNU Library General Public License, with    */
/*  the special exception on linking described in file ../LICENSE.     */
/*                                                                     */
/***********************************************************************/

/* $Id: gc_ctrl.c,v 1.47.4.2 2005/03/09 15:49:09 doligez Exp $ */

#include "alloc.h"
#include "compact.h"
#include "custom.h"
#include "finalise.h"
#include "gc.h"
#include "gc_ctrl.h"
#include "major_gc.h"
#include "minor_gc.h"
#include "misc.h"
#include "mlvalues.h"
#include "stacks.h"

#ifndef NATIVE_CODE
extern unsigned long caml_max_stack_size;    /* defined in stacks.c */
#endif

double caml_stat_minor_words = 0.0,
       caml_stat_promoted_words = 0.0,
       caml_stat_major_words = 0.0;

long caml_stat_minor_collections = 0,
     caml_stat_major_collections = 0,
     caml_stat_heap_size = 0,              /* bytes */
     caml_stat_top_heap_size = 0,          /* bytes */
     caml_stat_compactions = 0,
     caml_stat_heap_chunks = 0;

extern asize_t caml_major_heap_increment;  /* bytes; see major_gc.c */
extern unsigned long caml_percent_free;    /*        see major_gc.c */
extern unsigned long caml_percent_max;     /*        see compact.c */

#define Next(hp) ((hp) + Bhsize_hp (hp))

#ifdef DEBUG

/* Check that [v]'s header looks good.  [v] must be a block in the heap. */
static void check_head (value v)
{
  Assert (Is_block (v));
  Assert (Is_in_heap (v));

  Assert (Wosize_val (v) != 0);
  Assert (Color_hd (Hd_val (v)) != Caml_blue);
  Assert (Is_in_heap (v));
  if (Tag_val (v) == Infix_tag){
    int offset = Wsize_bsize (Infix_offset_val (v));
    value trueval = Val_op (&Field (v, -offset));
    Assert (Tag_val (trueval) == Closure_tag);
    Assert (Wosize_val (trueval) > offset);
    Assert (Is_in_heap (&Field (trueval, Wosize_val (trueval) - 1)));
  }else{
    Assert (Is_in_heap (&Field (v, Wosize_val (v) - 1)));
  }
  if (Tag_val (v) ==  Double_tag){
    Assert (Wosize_val (v) == Double_wosize);
  }else if (Tag_val (v) == Double_array_tag){
    Assert (Wosize_val (v) % Double_wosize == 0);
  }
}

static void check_block (char *hp)
{
  mlsize_t nfields = Wosize_hp (hp);
  mlsize_t i;
  value v = Val_hp (hp);
  value f;
  mlsize_t lastbyte;
  
  check_head (v);
  switch (Tag_hp (hp)){
  case Abstract_tag: break;
  case String_tag:
    /* not true when [caml_check_urgent_gc] is called by [caml_alloc]
       or caml_alloc_string:
       lastbyte = Bosize_val (v) - 1;
       i = Byte (v, lastbyte);
       Assert (i >= 0);
       Assert (i < sizeof (value));
       Assert (Byte (v, lastbyte - i) == 0);
    */
    break;
  case Double_tag:
    Assert (Wosize_val (v) == Double_wosize);
    break;
  case Double_array_tag:
    Assert (Wosize_val (v) % Double_wosize == 0);
    break;
  case Custom_tag:
    Assert (!Is_in_heap (Custom_ops_val (v)));
    break;
  
  case Infix_tag:
    Assert (0);
    break;

  default:
    Assert (Tag_hp (hp) < No_scan_tag);
    for (i = 0; i < Wosize_hp (hp); i++){
      f = Field (v, i);
      if (Is_block (f) && Is_in_heap (f)) check_head (f);
    }
  }
}

#endif /* DEBUG */

/* Check the heap structure (if compiled in debug mode) and
   gather statistics; return the stats if [returnstats] is true,
   otherwise return [Val_unit].
*/
static value heap_stats (int returnstats)
{
  CAMLparam0 ();
  long live_words = 0, live_blocks = 0,
       free_words = 0, free_blocks = 0, largest_free = 0,
       fragments = 0, heap_chunks = 0;
  char *chunk = caml_heap_start, *chunk_end;
  char *cur_hp, *prev_hp;
  header_t cur_hd;

#ifdef DEBUG
  caml_gc_message (-1, "### O'Caml runtime: heap check ###\n", 0);
#endif

  while (chunk != NULL){
    ++ heap_chunks;
    chunk_end = chunk + Chunk_size (chunk);
    prev_hp = NULL;
    cur_hp = chunk;
    while (cur_hp < chunk_end){
      cur_hd = Hd_hp (cur_hp);
                                           Assert (Next (cur_hp) <= chunk_end);
      switch (Color_hd (cur_hd)){
      case Caml_white:
        if (Wosize_hd (cur_hd) == 0){
          ++ fragments;
          Assert (prev_hp == NULL
                  || Color_hp (prev_hp) != Caml_blue
                  || cur_hp == caml_gc_sweep_hp);
        }else{
          if (caml_gc_phase == Phase_sweep && cur_hp >= caml_gc_sweep_hp){
            ++ free_blocks;
            free_words += Whsize_hd (cur_hd);
            if (Whsize_hd (cur_hd) > largest_free){
              largest_free = Whsize_hd (cur_hd);
            }
          }else{
            ++ live_blocks;
            live_words += Whsize_hd (cur_hd);
#ifdef DEBUG
            check_block (cur_hp);
#endif
          }
        }
        break;
      case Caml_gray: case Caml_black:
        Assert (Wosize_hd (cur_hd) > 0);
        ++ live_blocks;
        live_words += Whsize_hd (cur_hd);
#ifdef DEBUG
        check_block (cur_hp);
#endif
        break;
      case Caml_blue:
        Assert (Wosize_hd (cur_hd) > 0);
        ++ free_blocks;
        free_words += Whsize_hd (cur_hd);
        if (Whsize_hd (cur_hd) > largest_free){
          largest_free = Whsize_hd (cur_hd);
        }
        /* not true any more with big heap chunks
        Assert (prev_hp == NULL
                || (Color_hp (prev_hp) != Caml_blue && Wosize_hp (prev_hp) > 0)
                || cur_hp == caml_gc_sweep_hp);
        Assert (Next (cur_hp) == chunk_end
                || (Color_hp (Next (cur_hp)) != Caml_blue
                    && Wosize_hp (Next (cur_hp)) > 0)
                || (Whsize_hd (cur_hd) + Wosize_hp (Next (cur_hp)) > Max_wosize)
                || Next (cur_hp) == caml_gc_sweep_hp);
        */
        break;
      }
      prev_hp = cur_hp;
      cur_hp = Next (cur_hp);
    }                                          Assert (cur_hp == chunk_end);
    chunk = Chunk_next (chunk);
  }

  Assert (heap_chunks == caml_stat_heap_chunks);
  Assert (live_words + free_words + fragments
          == Wsize_bsize (caml_stat_heap_size));

  if (returnstats){
    CAMLlocal1 (res);

    /* get a copy of these before allocating anything... */
    double minwords = caml_stat_minor_words
                      + (double) Wsize_bsize (caml_young_end - caml_young_ptr);
    double prowords = caml_stat_promoted_words;
    double majwords = caml_stat_major_words + (double) caml_allocated_words;
    long mincoll = caml_stat_minor_collections;
    long majcoll = caml_stat_major_collections;
    long heap_words = Wsize_bsize (caml_stat_heap_size);
    long cpct = caml_stat_compactions;
    long top_heap_words = Wsize_bsize (caml_stat_top_heap_size);

    res = caml_alloc_tuple (15);
    Store_field (res, 0, caml_copy_double (minwords));
    Store_field (res, 1, caml_copy_double (prowords));
    Store_field (res, 2, caml_copy_double (majwords));
    Store_field (res, 3, Val_long (mincoll));
    Store_field (res, 4, Val_long (majcoll));
    Store_field (res, 5, Val_long (heap_words));
    Store_field (res, 6, Val_long (heap_chunks));
    Store_field (res, 7, Val_long (live_words));
    Store_field (res, 8, Val_long (live_blocks));
    Store_field (res, 9, Val_long (free_words));
    Store_field (res, 10, Val_long (free_blocks));
    Store_field (res, 11, Val_long (largest_free));
    Store_field (res, 12, Val_long (fragments));
    Store_field (res, 13, Val_long (cpct));
    Store_field (res, 14, Val_long (top_heap_words));
    CAMLreturn (res);
  }else{
    CAMLreturn (Val_unit);
  }
}

#ifdef DEBUG
void caml_heap_check (void)
{
  heap_stats (0);
}
#endif

CAMLprim value caml_gc_stat(value v)
{
  Assert (v == Val_unit);
  return heap_stats (1);
}

CAMLprim value caml_gc_quick_stat(value v)
{
  CAMLparam0 ();
  CAMLlocal1 (res);

  /* get a copy of these before allocating anything... */
  double minwords = caml_stat_minor_words
                    + (double) Wsize_bsize (caml_young_end - caml_young_ptr);
  double prowords = caml_stat_promoted_words;
  double majwords = caml_stat_major_words + (double) caml_allocated_words;
  long mincoll = caml_stat_minor_collections;
  long majcoll = caml_stat_major_collections;
  long heap_words = caml_stat_heap_size / sizeof (value);
  long top_heap_words = caml_stat_top_heap_size / sizeof (value);
  long cpct = caml_stat_compactions;
  long heap_chunks = caml_stat_heap_chunks;

  res = caml_alloc_tuple (15);
  Store_field (res, 0, caml_copy_double (minwords));
  Store_field (res, 1, caml_copy_double (prowords));
  Store_field (res, 2, caml_copy_double (majwords));
  Store_field (res, 3, Val_long (mincoll));
  Store_field (res, 4, Val_long (majcoll));
  Store_field (res, 5, Val_long (heap_words));
  Store_field (res, 6, Val_long (heap_chunks));
  Store_field (res, 7, Val_long (0));
  Store_field (res, 8, Val_long (0));
  Store_field (res, 9, Val_long (0));
  Store_field (res, 10, Val_long (0));
  Store_field (res, 11, Val_long (0));
  Store_field (res, 12, Val_long (0));
  Store_field (res, 13, Val_long (cpct));
  Store_field (res, 14, Val_long (top_heap_words));
  CAMLreturn (res);
}

CAMLprim value caml_gc_counters(value v)
{
  CAMLparam0 ();   /* v is ignored */
  CAMLlocal1 (res);

  /* get a copy of these before allocating anything... */
  double minwords = caml_stat_minor_words
                    + (double) Wsize_bsize (caml_young_end - caml_young_ptr);
  double prowords = caml_stat_promoted_words;
  double majwords = caml_stat_major_words + (double) caml_allocated_words;

  res = caml_alloc_tuple (3);
  Store_field (res, 0, caml_copy_double (minwords));
  Store_field (res, 1, caml_copy_double (prowords));
  Store_field (res, 2, caml_copy_double (majwords));
  CAMLreturn (res);
}

CAMLprim value caml_gc_get(value v)
{
  CAMLparam0 ();   /* v is ignored */
  CAMLlocal1 (res);

  res = caml_alloc_tuple (6);
  Store_field (res, 0, Val_long (Wsize_bsize (caml_minor_heap_size)));  /* s */
  Store_field (res, 1,Val_long(Wsize_bsize(caml_major_heap_increment)));/* i */
  Store_field (res, 2, Val_long (caml_percent_free));                   /* o */
  Store_field (res, 3, Val_long (caml_verb_gc));                        /* v */
  Store_field (res, 4, Val_long (caml_percent_max));                    /* O */
#ifndef NATIVE_CODE
  Store_field (res, 5, Val_long (caml_max_stack_size));                 /* l */
#else
  Store_field (res, 5, Val_long (0));
#endif
  CAMLreturn (res);
}

#define Max(x,y) ((x) < (y) ? (y) : (x))

static unsigned long norm_pfree (long unsigned int p)
{
  return Max (p, 1);
}

static unsigned long norm_pmax (long unsigned int p)
{
  return p;
}

static long norm_heapincr (long unsigned int i)
{
#define Psv (Wsize_bsize (Page_size))
  i = ((i + Psv - 1) / Psv) * Psv;
  if (i < Heap_chunk_min) i = Heap_chunk_min;
  return i;
}

static long norm_minsize (long int s)
{
  if (s < Minor_heap_min) s = Minor_heap_min;
  if (s > Minor_heap_max) s = Minor_heap_max;
  return s;
}

CAMLprim value caml_gc_set(value v)
{
  unsigned long newpf, newpm;
  asize_t newheapincr;
  asize_t newminsize;

  caml_verb_gc = Long_val (Field (v, 3));

#ifndef NATIVE_CODE
  caml_change_max_stack_size (Long_val (Field (v, 5)));
#endif

  newpf = norm_pfree (Long_val (Field (v, 2)));
  if (newpf != caml_percent_free){
    caml_percent_free = newpf;
    caml_gc_message (0x20, "New space overhead: %d%%\n", caml_percent_free);
  }

  newpm = norm_pmax (Long_val (Field (v, 4)));
  if (newpm != caml_percent_max){
    caml_percent_max = newpm;
    caml_gc_message (0x20, "New max overhead: %d%%\n", caml_percent_max);
  }

  newheapincr = Bsize_wsize (norm_heapincr (Long_val (Field (v, 1))));
  if (newheapincr != caml_major_heap_increment){
    caml_major_heap_increment = newheapincr;
    caml_gc_message (0x20, "New heap increment size: %luk bytes\n",
                     caml_major_heap_increment/1024);
  }

    /* Minor heap size comes last because it will trigger a minor collection
       (thus invalidating [v]) and it can raise [Out_of_memory]. */
  newminsize = norm_minsize (Bsize_wsize (Long_val (Field (v, 0))));
  if (newminsize != caml_minor_heap_size){
    caml_gc_message (0x20, "New minor heap size: %luk bytes\n",
                     newminsize/1024);
    caml_set_minor_heap_size (newminsize);
  }
  return Val_unit;
}

CAMLprim value caml_gc_minor(value v)
{                                                    Assert (v == Val_unit);
  caml_minor_collection ();
  return Val_unit;
}

static void test_and_compact (void)
{
  float fp;

  fp = 100.0 * caml_fl_cur_size
       / (Wsize_bsize (caml_stat_heap_size) - caml_fl_cur_size);
  if (fp > 1000000.0) fp = 1000000.0;
  caml_gc_message (0x200, "Estimated overhead (lower bound) = %lu%%\n",
                   (unsigned long) fp);
  if (fp >= caml_percent_max && caml_stat_heap_chunks > 1){
    caml_gc_message (0x200, "Automatic compaction triggered.\n", 0);
    caml_compact_heap ();
  }
}

CAMLprim value caml_gc_major(value v)
{                                                    Assert (v == Val_unit);
  caml_gc_message (0x1, "Major GC cycle requested\n", 0);
  caml_empty_minor_heap ();
  caml_finish_major_cycle ();
  test_and_compact ();
  caml_final_do_calls ();
  return Val_unit;
}

CAMLprim value caml_gc_full_major(value v)
{                                                    Assert (v == Val_unit);
  caml_gc_message (0x1, "Full major GC cycle requested\n", 0);
  caml_empty_minor_heap ();
  caml_finish_major_cycle ();
  caml_final_do_calls ();
  caml_empty_minor_heap ();
  caml_finish_major_cycle ();
  test_and_compact ();
  caml_final_do_calls ();
  return Val_unit;
}

CAMLprim value caml_gc_major_slice (value v)
{
  Assert (Is_long (v));
  caml_empty_minor_heap ();
  return Val_long (caml_major_collection_slice (Long_val (v)));
}

CAMLprim value caml_gc_compaction(value v)
{                                                    Assert (v == Val_unit);
  caml_empty_minor_heap ();
  caml_finish_major_cycle ();
  caml_finish_major_cycle ();
  caml_compact_heap ();
  caml_final_do_calls ();
  return Val_unit;
}

void caml_init_gc (unsigned long minor_size, unsigned long major_size,
                   unsigned long major_incr, unsigned long percent_fr,
                   unsigned long percent_m)
{
  unsigned long major_heap_size = Bsize_wsize (norm_heapincr (major_size));

#ifdef DEBUG
  caml_gc_message (-1, "### O'Caml runtime: debug mode ###\n", 0);
#endif

  caml_set_minor_heap_size (Bsize_wsize (norm_minsize (minor_size)));
  caml_major_heap_increment = Bsize_wsize (norm_heapincr (major_incr));
  caml_percent_free = norm_pfree (percent_fr);
  caml_percent_max = norm_pmax (percent_m);
  caml_init_major_heap (major_heap_size);
  caml_gc_message (0x20, "Initial minor heap size: %luk bytes\n",
                   caml_minor_heap_size / 1024);
  caml_gc_message (0x20, "Initial major heap size: %luk bytes\n",
                   major_heap_size / 1024);
  caml_gc_message (0x20, "Initial space overhead: %lu%%\n", caml_percent_free);
  caml_gc_message (0x20, "Initial max overhead: %lu%%\n", caml_percent_max);
  caml_gc_message (0x20, "Initial heap increment: %luk bytes\n",
                   caml_major_heap_increment / 1024);
}

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