On 27/08/14 19:21, Ken Teh wrote: > When I first worked with it, it ran the 1.3 kernel and it was really > fast. A 6µsec latency. It got progressively worse with 2x kernels. But > still much better than the 150µsec quoted earler.
Just to clarify. 150µsec max latency is the certification criteria from Red Hat. Many hardware vendors does it far better. Some require more tweaking than others. But once you've done that on appropriate hardware, you can often reach down to 10-25µs max latency, with a std.dev around 1-2µs. But it is highly hardware and configuration sensitive, and the lower latency you want the harder it gets. In addition, software tuning is also a crucial point. It's needed to ensure that the latency sensitive software runs with realtime scheduling and its priority isn't too low, as well as the kernel threads it depends on (like networking tx/rx threads) - But also not too high priorities, otherwise it may block important kernel threads doing their job. But doing this correctly, you can get really good results. -- kind regards, David Sommerseth