• Ell's avatar
    buffer: add gegl-scratch allocator · b99032d7
    Ell authored
    gegl-scratch is a fast memory allocator, suitable for small (up to
    a few megabytes), short-lived (usually, but not necessarily, bound
    to the current stack-frame) allocations.  Unlike alloca(), gimp-
    scratch doesn't use the stack, and is therefore safer, may outlive
    the current stackframe, and will also serve bigger requests, by
    falling-back to malloc().
    The allocator itself is very simple:  We keep a per-thread stack of
    cached memory blocks (allocated using the normal allocator).  When
    serving an allocation request, we simply pop the top block off the
    stack, and return it.  If the block is too small, we replace it
    with a big-enough block; if the stack is empty, we allocate a new
    block.  When the block is freed, we push it back to the top of the
    stack.  The idea is that the stacks will ultimately stabalize to
    contain blocks that can serve all the encountered allocation
    patterns, without needing to reisze any of the blocks; as a
    consequence, the amount of scratch memory allocated at any given
    time should really be kept to a minimum.
    Note that blocks may be allocated on one thread, and freed on
    another thread, without leaking memory, however, this is not an
    intended usage pattern, and may lead to suboptimal performance.
    This code was migrated from GIMP.