Hi Christophe,

> On 13 Feb 2018, at 21:50, Christophe Fontaine <christophe.fonta...@enea.com> 
> wrote:
> Hi Andrew !
> Happy to see someone else tried to play with the rpi ;)

I wanna try VPP in my home network, but don’t have a lot of b/w (just 2x50mbps 
with two ISPs), I am very strict about the power consumption for the “always 
on” gadgets, that’s the motivation to try to squeeze it on something small and 
see what happens :-)

> I'm guilty for the initial work 1 year ago, but as you saw, I did not tried 
> to keep up with the development.

Your work was of big help to get started, thanks a lot ! :-) though I could not 
dig enough into the archive to see whether “arm32” platform was specific to RPi 
or it was something more generic, so I went with a new platform file.

> For the rpi timercode, it was mainly to have something standard, based on the 
> aarch32 arch, but one thing worth mentioning is that I used a rpi2 (which is 
> not a aarch64 running in aarch32 mode.)
> But this does not exclude a specific mess-up from my side ;)

Oh, if you still have the h/w, would be curious to compare whether you also can 
observe this discrepancy in time... on my RPi3 with the kernel module, the 
“make run” would sporadically hang/crash, and since that was the timer, I just 
made a cycle taking the clib_cpu_time_now(), doing sleep(1), taking another 
time, and printing the difference... maybe the behavior somehow has changed 


> Christophe
> -----Original Message-----
> From: vpp-dev@lists.fd.io [mailto:vpp-dev@lists.fd.io] On Behalf Of Andrew 
> Yourtchenko
> Sent: Tuesday, February 13, 2018 6:29 PM
> To: vpp-dev@lists.fd.io
> Subject: [vpp-dev] Experiments in compiling and running VPP on Raspberry Pi 
> (32-bit)
> Hi all,
> This past weekend (which coincided with the start of my vacation) I have 
> decided to spend a day to see if I can get VPP to compile and run on 
> Raspberry Pi.
> After a few cuts with a blunt pen knife, I got it working - it compiles 
> entirely on RPi 3 itself and I can get it to the "make run", create tap 
> interfaces, and ping the linux side. Other than also testing VAT (it works. I 
> could create a couple of ACLs/assign them to interfaces) I did not yet test 
> anything more sophisticated, so - no warranties whatsoever ! :-)
> I had a "real" HDD mounted as a checkout root - not sure how well it would 
> work using the flash, but probably should not be a problem. The only other 
> thing worth mentioning - I learned RPi has a "thermometer" onscreen display 
> sign, during the compile :-) The temperature of the CPU has reached 84C (aka 
> "don't touch!"), that was *with* the heatsink. So, ensure you have a good 
> heat sink !
> I've captured the current state of my experiments here:
> https://gerrit.fd.io/r/#/c/10487/
> I boot the RPi with the additional "isolcpus=2,3" on the kernel command line. 
> I didn't test yet without that change. For the rest - it's a vanilla Raspbian 
> Lite image.
> One note: reading the archives / wiki
> (https://wiki.fd.io/view/VPP/Alternative_builds),
> I saw the mention of the kernel module. When I ran the code with it, I saw 
> very flaky behavior, and frequent lockups/crashes.
> My debugging concluded that probably having the rdtsc deltas over a one 
> second interval vary more than 10x over the consecutive periods of time is 
> what makes the timer code very unhappy. Not sure if this is specific to the 
> hardware I have or to the way it works in RPi in general.
> Anyway, I found a way to create a very crude but more stable replacement - 
> RPi appears to have a 64-bit 1Mhz free-running timer/counter. Multiply that 
> value by 1200... With that there were no more mysterious 
> instabilities/crashes. As a bonus - no need to load the kernel module, so the 
> process is simpler. Probably the performance implications of that for running 
> on Pi will be nontrivial, but it is surely better than crashing.
> Next 2.5 weeks I won't hack on this further (sightseeing/skiing will take 
> precedence - vacation!), so figured I'll use this time to hear what you all 
> think :-)
> --a


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