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
