On Fri, Nov 10, 2017 at 11:42:56AM +0100, Daniel Bristot de Oliveira wrote: > > > On 11/10/2017 11:14 AM, Ananyev, Konstantin wrote: > > Agree with Adrian here - the patch doesn't fix the problem in any case, > > I would agree with you if it were possible to assume one can fully > isolate a CPU on Linux... but it is not... > > This: > https://lwn.net/Articles/659490/ > > is still an open issue, and the reason why it is an open issue is the > kernel threads that need to run on every CPU, mainly when using the > PREEMPT_RT, which turns almost everything on threads. > > > while introducing an unnecessary slowdown in testpmd iofwd mode. > > Please think up some other approach. > > The other approach is to increase the priority of all other threads that > run on the isolate CPU. But that is not a good idea at all, as the other > threads might preempt the busy-loop thread at the worst possible moment. > > Using the knowledge of the thread about when it is the best time to give > a chance for other threads to run would be a smarter decision. > I don't like having this in the main loop either, and to echo others I wouldn't have thought that testpmd was actually used as anything other than a testing app. Also, I would have thought that running it at realtime priority wouldn't be a good idea, because of exactly this problem.
On the specifics of the solution, would using sched_yield() rather than nanosleep not be more suitable, given that the reason for this sleep is just to give the CPU to other threads? /Bruce
