Messages in this thread | | | Subject | Re: How to avoid serial port buffer overruns? | From | Lee Revell <> | Date | Wed, 16 Aug 2006 14:44:28 -0400 |
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On Wed, 2006-08-16 at 12:45 +0200, Raphael Hertzog wrote: > (Please CC me when replying) > > Hello, > > While using Linux on low-end (semi-embedded) hardware (386 SX 40Mhz, 8Mb > RAM), I discovered that Linux on that machine would suffer from serial > port buffer overruns quite easily if I use a baudrate high enough (I start > loosing bytes at >19200 bauds and I would like to make it reliable up to > 115 kbauds). I check if overruns are happening with > /proc/tty/driver/serial ("oe" field). > > Back when I was using the 2.4 kernel, I reduced dramatically the frequency > of overruns by using the "low latency" and "preemptible kernel" patch [1]. But > it still happened sometimes at 115 kbauds if the system was a bit loaded > (with disk I/O for example). > > Now I switched to stock 2.6 and while the stock kernel improved in > responsiveness, it still isn't enough by default (even with > CONFIG_PREEMPT=y and CONFIG_HZ=1000). So I wanted to try the "rt" patch of > Ingo Molnar and Thomas Gleixner, but the patched kernel doesn't boot (see > bug report in a separate mail on this list).
Does the serial performance seem to have regressed from 2.4 to 2.6? I am chasing a similar issue with a serial MIDI card (supported by the bog standard 8250 serial driver) that drops notes under 2.6 but works with 2.4. I don't have details yet, but it sounds like a similar problem.
Lee
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