Function dlmalloc_footprint 

pub unsafe extern "C" fn dlmalloc_footprint() -> usize

malloc_footprint();

Returns the number of bytes obtained from the system. The total number of bytes allocated by malloc, realloc etc., is less than this value. Unlike mallinfo, this function returns only a precomputed result, so can be called frequently to monitor memory consumption. Even if locks are otherwise defined, this function does not use them, so results might not be up to date.