On Mon, 19 Aug 2013, Ming Lei wrote: > Because usb_hcd_submit_urb is in the hotest path of usb core, > so use percpu counter to count URB instead of using atomic variable > because atomic operations are much slower than percpu operations. This seems like a ridiculous amount of additional overhead for a simple counter. The kernel doesn't even use this value for anything; it's only purpose is to allow userspace to see how many URBs have been transferred for a device. (I don't know what programs use this information. Powertop maybe?) Do you have any reason to believe this will really improve performance at all? 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
