On Tue, 11 Sep 2012, Wolfgang Wallner wrote: > Hello all, > > I have a few questions about the logging entry "sched: RT throttling activated" which I observe, and hope this is the correct place to ask :) > I will start by describing how i come to see this logging entry: > > I use an industrial PC with an 2.6.33 RT PREEMP kernel to run a real time application (based on the openPOWERLINK stack [1]), which consists of a kernel part and a user space part. > My application uses the openPOWERLINK stack to exchange data with other real time nodes in the network (a good overview how this is done is given on wikipedia [2]). > > When I let my application run overnight, I always see that it stops working after some hours, and the output of dmesg shows the following: > > [ 622.722690] EdrvInitOne waiting for link up... > [ 624.439269] EdrvInitOne finished with 0 > [ 624.439334] EdrvInit local MAC = 00 60 65 06 B2 25 > [ 624.454662] EplApiProcessImageAlloc: Alloc(640, 1100, 2, 2) > [ 624.454672] EplApiProcessImageAlloc: Alloc(eeea2000, 640, eef36800, 1100) > [ 624.477242] ifconfig epl 192.168.100.240 returned 0 > [ 635.058012] epl: no IPv6 routers present > [60382.945209] sched: RT throttling activated > [60382.945209] EplTimerHighResk: Continuous timer (handle 0x10000001) had to skip 836 interval(s)! > > > The first 7 entries are the normal logging output from the powerlink stack as it starts up. I just copied them into the mail for completeness. > The last line is debugging output of the powerlink stack as it complains that its timer was not handled for some time. > > The line with "sched: RT throttling activated" is the one I'm interested in. > I don't know what it means, and searching for this term did not turn up much. What kind of a search? A grep of "RT\ throttling" would have found it. > > My questions are now: > > * What does this logging entry mean? > Could you please point me to some information about RT throttling so that I can understand what's it about? in the kernel, look at Documentation/scheduler/sched-rt-group.txt > > * How to debug this issue? > At the moment I don't know what is cause and what is effect. > I'm not sure if I have a misconfiguration somewhere on my linux system and this influences my application or vice versa. > > Any tips on how to find out what's going on are greatly appreciated :) > It is considered a feature that allows non-RT tasks to make some progress, so that poorly written user space programs can't totally freeze your system - which would often be blamed on the rt kernel. You can shut this off for a harder kind of real-time - in which case, if your system is freezing, turning it back on could help to show whether the kernel is really freezing, or if it is a result of a problem with the user-space program. John -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
