On Fri, 1 Nov 2013, Cliff Brake wrote: > On Thu, Oct 31, 2013 at 2:25 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > >> > What host controller driver are you using? > >> > >> Its the USB EHCI host in the TI DM3730, so it uses the > >> drivers/usb/host/ehci-omap.c driver. > > > > You can find out exactly what part of the kernel is responsible for > > interrupt delays by using the "irqsoff" tracer. See > > Documentation/trace/ftrace.txt for details about how to use it. > > I captured a trace here: http://bec-systems.com/usb-trace.txt > > Still working to decode it -- any suggestions are welcome. As far as I can tell, the big blockage occurs when the machine has to analyze an input report from which it extracts 767 fields and ends up calling hid_process_event about 2300 times. Since each call takes around 60-80 microseconds, you end up with a very large latency. Why on earth are you using such enormous HID reports? > Enabling irqsoff significantly slows down the system. That's okay, since it's meant only for testing. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
