Re: How to rte_epoll_wait for IPC?

[Stephen Hemminger <stephen@networkplumber.org>]

On Fri, 6 Oct 2023 18:28:10 +0200
Morten Brørup <mb@smartsharesystems.com> wrote:

> > From: Stephen Hemminger [mailto:stephen@networkplumber.org]
> > Sent: Friday, 6 October 2023 18.03
> > 
> > On Fri, 6 Oct 2023 12:03:46 +0200
> > Morten Brørup <mb@smartsharesystems.com> wrote:
> >   
> > > 2. The "processing" thread receives its packets from the rte_ring.  
> > This thread should sleep until packets are ready for it in the rte_ring.  
> > >
> > > The "ingress" thread knows when it puts packets into the rte_ring, so  
> > it can signal that event to the "processing" thread, to wake it up;
> > either as an interrupt/signal, or through a file descriptor. Is this
> > supported by rte_epoll (or other DPDK APIs), and how?
> > 
> > When having to do this in applications, I used a eventfd() as well as
> > the rte ring.
> > The ingress write's to eventfd and the other thread used epoll on the
> > fd.
> > 
> > Optimized this by having the ingress thread only signal via write if
> > ring was in empty state.
> > And the reader thread only needs to do (epoll/read) if ring became empty
> > during last cycle;
> > i.e num packets from rte_ring_burst() was 0.
> > 
> > Basically, when using epoll and other SW event models, you need to turn
> > all data sources
> > into file descriptors.  
> 
> This sounds exactly like what I am looking for.
> 
> Are there DPDK APIs for eventfd(), so I can use them with rte_epoll_wait?

Eventfd is just a system call.

You then add the resulting fd to epoll object with rte_epoll_ctl().