Em Sun, Apr 13, 2008 at 11:00:08AM -0700, mgross escreveu: > On Sat, Apr 12, 2008 at 07:34:28PM -0400, Mauricio A. Araya L�pez wrote: > > On Sat, Apr 12, 2008 at 01:08:37PM -0700, mgross wrote: > > > On Fri, Apr 04, 2008 at 03:57:53AM -0400, Mauricio A. Araya L�pez wrote: > > > > Hi all, > > > > > > > > I've been searching on the web (and in the rt-wiki) for the current > > > > status of the real-time support for devices. For instance > > > > the serial port, CAN Bus, etc. > > > > > > [...] > > > > > FWIW I was able to get +/- 30usec jitter from a serial port experiment > > > where I programmed a PIC to push 5 bytes over the serial line every > > > 20ms. > > My results are similar. A 30 usec jitter it seems to be the limit, > > but indeed the jitter is less, because the latency is near the > > 10 usec. But, that is "on average", because I've run several > > test during long time periods, and my worst jitter is like 5 msec!, > > which is too much. Maybe it is a hardware problem, but I am using > > no swap, no usb and no DMA, and I dont know which other thing > > i should disable to not have this huge random jitter. > > (Obviosly I am locking the memory to have no paging) > > How long did you need to run it to hit a 5msec jitter? > > My tests where only for a few min while I test compiled the kernel a > few times to see if that would effect things. And have you guys tried with a ftrace/latency trace enabled kernel? It would be really interesting to know what happens in this 5ms :-) - Arnaldo -- 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
