[RFC PATCH 0/4] USB: HCD/EHCI: giveback of URB in tasklet context

Ming Lei ming.lei at canonical.com
Thu Jun 13 23:24:58 EDT 2013


On Fri, Jun 14, 2013 at 3:41 AM, Alan Stern <stern at rowland.harvard.edu> 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.


Thanks,
--
Ming Lei



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