From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 17 Feb 2017 12:47:22 +0100 From: "Mariusz Janiak" Message-ID: <58a6e2ca5ab7e5.39693661@wp.pl> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-2" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Subject: [Xenomai] Odp: Re: RtNet and Interrupts List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Norbert Lange Cc: Xenomai Dnia Pi=B1tek, 17 Lutego 2017 12:19 Norbert Lange nap= isa=B3(a)=20 > 2017-02-17 11:45 GMT+01:00 Mariusz Janiak : > > Dnia Pi=B1tek, 17 Lutego 2017 11:18 Norbert Lange = napisa=B3(a) > >> Hello, > >> > >> I wonder if the Rtnet Stack is driven at packet level, ie. if after > >> every one received packet( or even buffer) an IRQ is received. > >> I worked on a Project where a similar Problem with Ethernet > >> communication had to be solved, and I just queued up enough receive > >> buffers and just picked up anything that arrived at the start of a > >> timeslot. > >> > >> On 100Mbit and a 1ms timeslot, I calculated a max. of 150 received > >> pakets. Not that realtime communication can get anywhere close to > >> that, but you have to deal with worst cases and guarantee that your > >> system aint missing the cpu time spend in IRQs for other things - even > >> if you just decide to drop all those packets, the IRQ overhead would > >> be there. > >> > >> So is Rtnet using "polling" at timeslots, or irqs? > > > > Hi, > > > > As far as I know, RTnet is interrupt driven stack, it means that after = reception of each packet the interrupt is generated and handled by the NIC = driver. This is one of the reasons why porting of the RT driver to new NIC= s is so problematic, especially now when new drivers support NAPI. >=20 > Seems to be a bad Idea, I guess most RT communication is continuous, > means there is not a question whether packets arrived but only how > much of them.If I worked with irqs in the project above, the weak ARM > CPU wouldn`t be able to do anything else. Maybe author of the RTnet stack can give better answer, but in my opinion, = in the case of the hard RT communication, we have to know in advance what i= s the maximum packet delivery time. The RTnet guarantee fixed time packet d= elivery. There is always a trad off between bandwidth and latency, you can'= t have both.=20 > No efforts in using something similar to "New API"? (who comes up with > such names...) I remember a discussion about NAPI in context of RTnet stack, but I don't = know if any attempts have been made.=20 > > > >> Kind Regards, > >> Norbert > >> > >> PS. > >> Complete unrelated, but are there any big companies using Xenomai / > >> Rtnet that can be named? > > > > I know that Universities use it a lot in the field of robotics (eg. SOE= M + OROCOS). There is a port of the RTnet stack for microcontrolers if you = are interested (RTnet Embedded) > > > > https://bitbucket.org/mariuszjaniak/rtnet-embedded >=20 > Actually I am, sounds like you know about "RTnet Embedded" =3D). >=20 > The reason I ask is that I want to push this at the company I work, > unfortunately higher ups typically are most impressed if some rich > companies are using it (and claims that it is the most popular thing > ever). Unfortunately I can't help.=20 > > > > Best regards, > > Mariusz >=20 > Thanks, Norbert