AFAIK, preempt-rt on the 3.8 kernel is either brand new or still a work in process. The running kernels I'm aware of use a patched version of 3.2, but I haven't been following along real close.
In my tests with preempt-rt (many months ago), I was getting pretty lousy worst-case latency numbers, so I switched to using Xenomai. Note that the latest Xenomai from git (soon to be officially released) supports the 3.8.13 kernel as used on the BeagleBone, and has a pre/post patch set to make it easy to build the kernel. I've even got kernel build scripts if you don't like doing everything from scratch: https://github.com/cdsteinkuehler/linux-dev/tree/3.8.13-bone27-xenomai Since I looked at preempt-rt, the OSADL folks have brought up a test system with an AM3359 (not a BeagleBone, but the same SoC), and they are seeing much better latency numbers than I was. Again, this is still a 3.2 kernel, not a 3.8. I'm not sure if the better numbers are due to a different kernel config or improved drivers. Preempt-rt relies on the Linux kernel code and drivers being written for high-performance SMP processing and generally playing nice, while xenomai just preempts the entire Linux kernel (including any mis-behaving drivers) so it works well with ...um... "sub-optimal" vendor-supplied drivers, which are all too common in the ARM space. :) Let us all know if you get a 3.8 kernel with preempt-rt running on a 'Bone (white or black). On 9/30/2013 8:44 PM, wittend wrote: > I am interested in tightening up the performance of the BBB as well. I > would like to hear about either your experience with this or that of anyone > else who has tried it. > > Dave > > On Monday, September 30, 2013 2:32:07 PM UTC-5, jeshu wrote: >> >> Hello List, >> >> Previously I have implemented my applications with Real time kernel in my >> Beaglebone White using Robert Nelson's kernel. Now I am going to change the >> platform/board to BBB, I am unable to find any RT patched kernel. Can >> anybody post me the links where I can find the PT patched 3.8. kernel ? >> >> Thanks, >> Jeshwanth >> Bangalore >> > -- Charles Steinkuehler [email protected]
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