Function mem_prefetch_async 

pub unsafe fn mem_prefetch_async(
    dev_ptr: *const c_void,
    count: usize,
    target: PrefetchTarget,
    stream: &Stream,
) -> Result<()>

Prefetch count bytes of unified memory at dev_ptr to target, ordered on stream. dev_ptr must be a managed-memory allocation (from ManagedBuffer or cudaMallocManaged).

Safety

dev_ptr..dev_ptr+count must be a live managed allocation.