Function dlmalloc_max_footprint 

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

malloc_max_footprint();

Returns the maximum number of bytes obtained from the system. This value will be greater than current footprint if deallocated space has been reclaimed by the system. The peak 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.`