No -- in Lwan, files that will be sent with sendfile() are kept open for a while; when they're first open, the same thread that opened (and this might block) will call readahead(). Files are sent in 512kB bursts. It might use mmap()+madvise(), but only for small files (<16KB)... but, yeah, there's not a lot of control here. I'm not that worried, though; this is but a toy. :)

Registered I/O (RIO) or I/O Completion Ports (IOCP) in Windows seems to be better in this regard, but I don't have a lot of experience in that platform. Trent Nelson, from the PyParallel project, has a few talks about it; it's quite neat.