I've been trying to track down where all the CPU time goes while processing USB interrupts for HID devices. At the moment, out of everything on the cubox, moving the mouse or even pressing a key on the keyboard just once is far more expensive than processing an interrupt for the network interface or handling the SDHCI port. Handing HID actions weigh in at around 300-400us per USB interrupt. Around two-thirds of the time for a USB HID device interrupt is spent in the HID layer, currently tracked down to: for (a = 0; a < report->maxfield; a++) hid_input_field(hid, report->field[a], cdata, interrupt); in hid_report_raw_event(). However, looking at hid_input_report() and its use of down_trylock(), I'm wondering why we're trying to run this chunk of code in IRQ context anyway? Why not a tasklet or workqueue? Any suggestions on why processing a key press or mouse movement is soo expensive? -- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: -- 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
