Hi Laurent, >> For a single device running with maxpacket of 3072 per microframe, the >> EHCI driver is indicating 57% utilization of the bus (the sysfs stats >> already takes into account the fact that only 80% of the bus is >> available for isoc traffic). > > 3072 bytes * 8000 microframes/s * 8 bit/byte / 80% / 480e6 = 51.2% Where did you arrive at that "480e6" constant? Is that from the USB Spec? I saw you refer to it in another email. > You also have to take the USB overhead into account, so the actual value will > be a bit larger than that. 57% seems plausible. It was my understanding that the whole reason for the 80% max utilization was to account for overhead. And is it really plausible that there is a 14% overhead? That sounds like quite a bit. If it had been off 2-3%, that might have seemed reasonable, but 14% seems like a bit much. I guess I'm just wondering how much of what you are saying is idle speculation based on your experience with Linux's USB implementation, and how much is actually based on the spec. Devin -- Devin J. Heitmueller - Kernel Labs http://www.kernellabs.com -- 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
