Re: how to measure scheduler latency on powerpc? realfeel doesn't work due to /dev/rtc issues

William Lee Irwin III
2003-05-09T16:42:20Z

On Fri, 2003-05-09 at 03:01, William Lee Irwin III wrote:
>> Why not just keep track of it in the scheduler? The statistic is well-
>> defined in terms of things measurable at context switch and wakeup.

On Fri, May 09, 2003 at 12:47:05PM -0400, Robert Love wrote:
> This would measure context switch latency. Or something.
> By definition, scheduling latency is the time from an interrupt which
> wakes the task up until the task is actually running.
> Historically, it has been measured by things like realfeel or amlat or
> whatever which generate interrupts and wake a waiting task up. You then
> measure the latency between the interrupt and when the task actually
> runs in user-space.
> So Chris can then go run this test under varying loads and see how bad
> the latency gets. I understand his question, but (sorry Chris) I have
> no idea of the solution on PPC.

Not at all. Just stamp at wakeup and difference when it runs.

-- wli