Function mi_region_try_alloc_os

3rd/mimalloc-2.0.9/src/region.c:172–218

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static bool mi_region_try_alloc_os(size_t blocks, bool commit, bool allow_large, mem_region_t** region, mi_bitmap_index_t* bit_idx, mi_os_tld_t* tld)
{
  // not out of regions yet?
  if (mi_atomic_load_relaxed(&regions_count) >= MI_REGION_MAX - 1) return false;

  // try to allocate a fresh region from the OS
  bool region_commit = (commit && mi_option_is_enabled(mi_option_eager_region_commit));
  bool region_large = (commit && allow_large);
  bool is_zero = false;
  bool is_pinned = false;
  size_t arena_memid = 0;
  void* const start = _mi_arena_alloc_aligned(MI_REGION_SIZE, MI_SEGMENT_ALIGN, 0, &region_commit, &region_large, &is_pinned, &is_zero, _mi_arena_id_none(),  & arena_memid, tld);
  if (start == NULL) return false;
  mi_assert_internal(!(region_large && !allow_large));
  mi_assert_internal(!region_large || region_commit);

  // claim a fresh slot
  const size_t idx = mi_atomic_increment_acq_rel(&regions_count);
  if (idx >= MI_REGION_MAX) {
    mi_atomic_decrement_acq_rel(&regions_count);
    _mi_arena_free(start, MI_REGION_SIZE, MI_SEGMENT_ALIGN, 0, arena_memid, region_commit, tld->stats);
    _mi_warning_message("maximum regions used: %zu GiB (perhaps recompile with a larger setting for MI_HEAP_REGION_MAX_SIZE)", _mi_divide_up(MI_HEAP_REGION_MAX_SIZE, MI_GiB));
    return false;
  }

  // allocated, initialize and claim the initial blocks
  mem_region_t* r = &regions[idx];
  r->arena_memid  = arena_memid;
  mi_atomic_store_release(&r->in_use, (size_t)0);
  mi_atomic_store_release(&r->dirty, (is_zero ? 0 : MI_BITMAP_FIELD_FULL));
  mi_atomic_store_release(&r->commit, (region_commit ? MI_BITMAP_FIELD_FULL : 0));
  mi_atomic_store_release(&r->reset, (size_t)0);
  *bit_idx = 0;
  _mi_bitmap_claim(&r->in_use, 1, blocks, *bit_idx, NULL);
  mi_atomic_store_ptr_release(void,&r->start, start);

  // and share it
  mi_region_info_t info;
  info.value = 0;                        // initialize the full union to zero
  info.x.valid = true;
  info.x.is_large = region_large;
  info.x.is_pinned = is_pinned;
  info.x.numa_node = (short)_mi_os_numa_node(tld);
  mi_atomic_store_release(&r->info, info.value); // now make it available to others
  *region = r;
  return true;
}

/* ----------------------------------------------------------------------------
  Try to claim blocks in suitable regions