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

Robert Love
2003-05-09T16:31:53Z

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.

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.

Robert Love