Re: [PATCH RFC 0/6] epoll: Introduce new syscall "epoll_mod_wait"

On Tue, Jan 20 2015, Fam Zheng [off-list ref] wrote:

DESCRIPTION

       The epoll_mod_wait() system call can be seen as an enhanced combination
       of several epoll_ctl(2) calls, which are followed by an epoll_pwait(2)
       call. It is superior in two cases:
       
       1) When epoll_ctl(2) are followed by epoll_wait(2), using epoll_mod_wait
       will save context switches between user mode and kernel mode;
       
       2) When you need higher precision than microsecond for wait timeout.

You probably want to say millisecond.

           struct epoll_mod_cmd {

[...]

           };

           struct epoll_wait_spec {

[...]

           } EPOLL_PACKED;

Either both or none of these should mention that EPOLL_PACKED is in fact
part of the actual definition. The changelog for 3/6 sorta mentions
that it's not really needed for epoll_mod_cmd. Why is it necessary for
either struct?

RETURN VALUE

       When successful, epoll_mod_wait() returns the number of file
       descriptors ready for the requested I/O, or zero if no file descriptor
       became ready during the requested timeout milliseconds.

And here, it doesn't make sense to mention a unit, since the new timeout
is given using struct timespec (this was the whole point, right?).

Rasmus