Re: PREEMPT_RT vs I-PIPE: the numbers, part 2

Paul E. McKenney
2005-06-22T18:51:56Z

On Wed, Jun 22, 2005 at 01:20:03PM -0400, Kristian Benoit wrote:
> On Wed, 2005-06-22 at 09:27 -0700, Paul E. McKenney wrote:
> > On Wed, Jun 22, 2005 at 11:31:39AM -0400, Karim Yaghmour wrote:
> >
> > If I understand your analysis correctly (hah!!!), your breakdown
> > of the maximum delay assumes that the maximum delays for the logger
> > and the target are correlated. What causes this correlation?
> > My (probably hopelessly naive) assumption would be that there would
> > be no such correlation. In absence of correlation, one might
> > approximate the maximum ipipe delay by subtracting the -average-
> > ipipe delay from the maximum preemption delay, for 55us - 7us = 48us.
> > Is this the case, or am I missing something here?
>
> Your analysis is correct, but with 600,000 samples, it is possible that
> we got 2 peeks (perhaps not maximum), one on the logger and one on the
> target. So in my point of view, the maximum value is probably somewhere
> between 55us / 2 and 55us - 7us. And probably closer to 55us / 2.

Possible, but it could also be a large peak and a small one.

Any way of getting the logger's latency separately? Or the target's?

Thanx, Paul