We noticed the same issue described in https://lists.samba.org/archive/samba-technical/2013-January/089967.html on a Samba 3.6 based system when debugging a performance issue.
The fix is already in master. Please backport this fix to 3.6 and 4.0.
Changing winbindd to use epoll currently has side-effect in that if epoll isn't available (on non-Linux platforms) we fall back to using select(). We should fall back to using poll() instead.
I have an additional patchset that addresses this but I want to get that into master before we do a 3.6.x back-port of the epoll patch change referred to here.
(In reply to comment #1)
> I have an additional patchset that addresses this but I want to get that into
> master before we do a 3.6.x back-port of the epoll patch change referred to
Can you share that patchset somewhere?
I'm *so* glad you asked, I hope that means you're going to review it :-). I am about to post it to master today. It's taken a while to get it bullet-proof (and I'm still running final tests), so sorry for the delay.