> I don't think any regular driver thread priority could interfere with > the dual kernel operating in primary/real-time mode, that is actually a > selling point of the pipelined IRQ architecture which decouples the > regular kernel logic from the real-time core.
That's a good point. I'm looking at my old code with a fresh set of eyes, and I think I found a possible cause. In debugging months prior I had apparently switched from using ioctl_rt to ioctl_nrt, but never reverted back. The latency numbers were apparently fine until I saw an influence of heavy network usage. On Thu, Apr 27, 2017 at 9:32 AM, Philippe Gerum <[email protected]> wrote: > On 04/27/2017 06:27 PM, Philippe Gerum wrote: >> On 04/27/2017 06:09 PM, Adam Vaughan wrote: >>> Hi Gerber, >>> >>> I haven't tried Xenomai on the RPi in a few years (I've been working >>> on BeagleBone Xenomai lately), but I have experimented with Xenomai >>> 2.6 patches on the RPi 1 in the configuration you describe. >>> >>> There's more detail in section 7.5 in my dissertation [1], but I >>> strongly suggest checking that the USB driver isn't affecting your >>> overall system latency numbers under load. Under heavy USB Ethernet >>> usage with the FIQ turned off I measured system stalls of up to 15 >>> milliseconds under Xenomai with an oscilloscope. >>> >>> The only fix I had for this was to use PREEMPT_RT to lower the USB >>> driver thread priority. At the time, I couldn't get PREEMPT_RT >>> patches to cleanly apply to the available Xenomai kernel patches, so I >>> ended up just using PREEMPT_RT exclusively. This patch situation is >>> likely different these days. >> >> I don't think any regular driver thread priority could interfere with >> the dual kernel operating in primary/real-time mode, that is actually a >> selling point of the pipelined IRQ architecture which decouples the >> regular kernel logic from the real-time core. >> >> Using the I-pipe tracer combined with the -f option from the latency >> test may give some hints about the issue. >> > > Btw, there is a validated port of kernel 4.1 to the RPI Zero available > from git://git.xenomai.org/ipipe.git, vendors/beaglebone/ipipe-4.1. > > -- > Philippe. _______________________________________________ Xenomai mailing list [email protected] https://xenomai.org/mailman/listinfo/xenomai
