Re: [LAU] Analysing (debugging) USB port performance

On 23/09/2019 13.14, Lorenzo Sutton wrote: There are ways to improve things a bit, but only so much can be done in software, because part of that is, indeed, hard-wired in notebooks. Such a computer may have more than one USB bus hardware, and the external ports are only part of the things connected to those buses. Webcam, touchpad, smartcard reader and other devices can be connected internally via USB. There may also be internal HUBs adding extra layer. Some of the external USB ports share bus (and its IRQ) or internal port with some of those devices and possibly other external ports. For real-time audio the best choice would be a dedicated USB port on a separate bus, not shared with anything else, but thing might be not available. And when a bus, or internal port is shared with a different device, the kind of the device also matters. Some play nicer with audio devices, some are worse. I guess one can define all the rules how to choose the optimal port, but simple trial and error is much more practical. irqbalance, rtirq, some kernel boot options and maybe other tools may be used to optimize USB IRQ handling. This might be quite complex and still will be limited by the hardware configuration. Jacek