> How can the requirement be for both must-handle-in-minimum-time data > (low_latency) and the-userspace-reader-isn't-reading-fast-enough- > so-its-ok-to-halt-transmission ? Because low latency is about *turn around* time. There are plenty of protocols that can flow control, do flow control and want low latency because they are not windowed. It's not mutually exclusive by any means. > But first I'd like some hard data on whether or not a low latency > mode is even necessary (at least for user-space). The easy way to simulate the annoying as crap worst cases from dumbass firmware downloaders and the like is to set up a link between two PCs and time 2000+ repetitions of send 64 bytes wait for a Y send 64 bytes wait for a Y .... and the matching far end being a box running an existing kernel or a PIC or something doing the responses. Historically we used to lose about 20mS per cycle which over 2000 got to be a bit of a PITA. Low latency goes back to the days of flip buffers, bottom halves an a 100Hz clock. There are certainly better ways to do it now if its needed. Alan -- To unsubscribe from this list: send the line "unsubscribe linux-serial" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
