Re: [PATCH] /dev/epoll update ...

[Jamie Lokier]

Eric W. Biederman wrote:
> > As Davide points out in his reply, /dev/epoll is an exact clone of
> > the O_SETSIG/O_SETOWN/O_ASYNC realtime signal way of getting readiness
> > change events, but using a memory-mapped buffer instead of signal delivery
> > (and obeying an interest mask).  Unlike /dev/poll, it only provides
> > information about *changes* in readiness.
> 
> Right.  But it does one additional thing that the rtsig method doesn't
> it collapses multiple readiness *changes* into a single readiness change.
> This allows the kernel to keep a fixed size buffer so you never need
> to fallback to poll as you need to with the rtsig approach.

That could be added to rtsigs, with the same result: no need to fallback
to poll.  You could even keep the memory for the queued signal / event
inside the file structure.

-- Jamie