Serial port latency is heavily dependant on the HZ rate for data bits and input side stuff and you can set the low latency flag to improve upon that. Beyond that if you are using the modem control ioctls then it depends a lot on the hardware. USB has some implicit queuing on the bus but generic uarts have very little on the whole.
You should be able to get much better results by using mlockall(MCL_FUTURE) on the actual test process and setting the priority into the real time range, in combination with turning on low latency on the motherboard ports. The current -mm kernels also support arbitary baud rate (well 45 or 50 rather than 45.5), although this hasn't yet been enabled for all platforms or pushed into the base kernel for i386 yet. It will be soon however and then glibc can be tweaked to use it by default. Alan - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
