Hi Grant, Have you tried to compile the kernel with low-latency + preemtion option which is supposed to allow userspace applications to react faster? I believe that the default is 'server' mode. I think 'Low-Latency Desktop' mode may give you better performance.
Here is what your linux config option will look like: Processor type and features Preemption Model ( ) No Forced Preemption (Server) ( ) Voluntary Kernel Preemption (Desktop) (x) Preemptible Kernel (Low-Latency Desktop) Let us know if your performance improves by trying any of these options, Dave Grant Edwards wrote: > I've been doing some performance tests comparing eCos and > uClinux on a NIOS2 platform. TCP throughput is comparable > (uClinux does a bit better with only 1 connection&thread, and > eCos does a bit better at 32 connections&threads). But, latency > on uClinux is much worse. The table below shows the time in > milliseconds required for a user-space thread on an otherwise > idle system to receive a small message (two bytes) via TCP and > echo it back (10 trials): > > eCos uClinux > ------- ------- > 1.864 8.151 > 2.079 4.509 > 1.972 7.699 > 1.871 7.189 > 1.728 5.152 > 1.842 6.803 > 1.733 7.041 > 1.847 3.758 > 1.850 7.703 > 1.842 1.785 > > min 1.728 1.785 > avg 1.863 5.979 > max 2.079 8.151 > range 0.351 6.366 > > The average latency is 3X worse in uClinux, the worst-case > latency is 4X worse, and the range is 20X worse. We'd like to > be able to use uClinux for it's better support of wireless and > wider availability of application code, but the large and > variable latency times are giving us pause. > > I tried using real-time scheduling of the user threads, but it > didn't help latency and it completely ruined TCP throughput for > cases where multiple threads were receiving data. > > Can anybody provide any hints on what I can do to improve the > latency under uClinux? > > I'm currently using 2.6.26-rc6. What kernel configuration > parameters should I be looking at? > > _______________________________________________ uClinux-dev mailing list uClinux-dev@uclinux.org http://mailman.uclinux.org/mailman/listinfo/uclinux-dev This message was resent by uclinux-dev@uclinux.org To unsubscribe see: http://mailman.uclinux.org/mailman/options/uclinux-dev