On Linux, IOV_MAX is 1024 – but for stupid, historical reasons, it's 16 on us. (This breaks tmux, which relies on a sendmsg() with more than 16 vectors.) While we don't necessarily need to change IOV_MAX, we do need to support applications that have an IOV_MAX of 1024.
Former user commented on 2014-10-04T05:03:16.000-0400:
illumos-joyent commit e2400fb (branch master, by Bryan Cantrill)
OS-3404#icft=OS-3404 lx brand must support sendmsg() with IOV_MAX of 1024