Hi Simon, Not sure if this helps; are you polling the actuators using usb-serial io? I've had performance issues reading from the raspberry pi serial port. see: http://www.spinics.net/lists/linux-rt-users/msg16880.html On Tue, Sep 5, 2017 at 5:05 PM, Simon Thelen <urday@xxxxxxxxxxxxxxx> wrote: > Hello, > > We have some Dynamixel robitic actuators hooked up via USB to an Ubuntu > 14.04 system running the 4.4.79-rt92 kernel. When using a kernel built > without the realtime patches (CONFIG_PREEMPT not set) we can query the > bus at 1000Hz (2 devices at 500Hz each) whereas with the realtime kernel > (CONFIG_PREEMPT=y, CONFIG_PREEMPT_RT_FULL=y) we only get 62.5Hz per > device. The USB device requests Ivl=0ms in both cases and the issue > isn't related to load etc. The polling rate is always 62.5Hz (It takes > ~15ms for every read()). > > > Is this a known limitation of USB with the CONFIG_PREEMPT_RT patches and > is there any method to improve the polling rate? > > -- > Simon Thelen > -- > 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 -- 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
