On Fri, Jun 14, 2013 at 10:56 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Fri, 14 Jun 2013, Ming Lei wrote: > >> On Fri, Jun 14, 2013 at 3:41 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: >> > >> > The main reason for moving away from the current scheme is to reduce >> > latency for other interrupt handlers. Ming gave two examples of slow >> > USB code that runs in hardirq context now; with his change they would >> > run in softirq context and therefore wouldn't delay other interrupts so >> > much. (Interrupt latency is hard to measure, however.) >> >> With the two trace points of irq_handler_entry and irq_handler_exit, the >> interrupt latency(or the time taken by hard irq handler) isn't hard to measure. >> One simple script can figure out the average/maximum latency for one irq >> handler, like I did in 4/4. > > But that doesn't measure the time between when the IRQ request is > issued and when irq_handler_entry runs. That might be hard to measure, also I am wondering if the time can be measured only by software, but these patches only focus on the time between HCD irq entry and irq exit. Thanks, -- Ming Lei -- 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
