Re: [PATCH] Preemption Latency Measurement Tool

Robert Love
2001-09-20T21:11:08Z

On Thu, 2001-09-20 at 04:21, Andrea Arcangeli wrote:
> > You've forgotten a one liner.
> >
> > #include <linux/locks.h>
> > +#include <linux/compiler.h>
>
> woops, didn't trapped it because of gcc 3.0.2. thanks.
>
> > But this is not enough. Even with reniced artsd (-20).
> > Some shorter hiccups (0.5~1 sec).
>
> I'm not familiar with the output of the latency bench, but I actually
> read "4617" usec as the worst latency, that means 4msec, not 500/1000
> msec.

Right, the patch is returning the length preemption was unavailable
(which is when a lock is held) in us. So it is indded 4ms.

But, I think Dieter is saying he _sees_ 0.5~1s latencies (in the form of
audio skips). This is despite the 4ms locks being held.

--
Robert M. Love
rml at ufl.edu
rml at tech9.net