Method sys_alloc

libCacheSim/dataStructure/sparsepp/spp_dlalloc.h:2543–2666

Get memory from system using MMAP

// Get memory from system using MMAP
void* malloc_state::sys_alloc(size_t nb)
{
    char* tbase = cmfail;
    size_t tsize = 0;
    flag_t mmap_flag = 0;
    size_t asize; // allocation size

    mparams.ensure_initialization();

    // Directly map large chunks, but only if already initialized
    if (use_mmap() && nb >= mparams._mmap_threshold && _topsize != 0)
    {
        void* mem = mmap_alloc(nb);
        if (mem != 0)
            return mem;
    }

    asize = mparams.granularity_align(nb + sys_alloc_padding());
    if (asize <= nb)
        return 0; // wraparound
    if (_footprint_limit != 0)
    {
        size_t fp = _footprint + asize;
        if (fp <= _footprint || fp > _footprint_limit)
            return 0;
    }

    /*
      Try getting memory with a call to MMAP new space (disabled if not SPP_HAVE_MMAP).
      We need to request enough bytes from system to ensure
      we can malloc nb bytes upon success, so pad with enough space for
      top_foot, plus alignment-pad to make sure we don't lose bytes if
      not on boundary, and round this up to a granularity unit.
    */

    if (SPP_HAVE_MMAP && tbase == cmfail)
    {
        // Try MMAP
        char* mp = (char*)(SPP_CALL_MMAP(asize));
        if (mp != cmfail)
        {
            tbase = mp;
            tsize = asize;
            mmap_flag = USE_MMAP_BIT;
        }
    }

    if (tbase != cmfail)
    {

        if ((_footprint += tsize) > _max_footprint)
            _max_footprint = _footprint;

        if (!is_initialized())
        {
            // first-time initialization
            if (_least_addr == 0 || tbase < _least_addr)
                _least_addr = tbase;