Re: [patch] voluntary-preempt-2.6.8.1-P0

Lee Revell
2004-08-16T02:45:04Z

On Sun, 2004-08-15 at 22:43, Ingo Molnar wrote:
> * Lee Revell <rlrevell@joe-job.com> wrote:
>
> > http://krustophenia.net/testresults.php?dataset=2.6.8.1-P0
>
> nice. (What is the difference between the left-hand and the right-hand
> graphs - why is the right-hand side one 'wider'?)
>

The right hand graph is logarithmically scaled on the y axis (set
logscale y in gnuplot). Some of the latencies are rare enough to not
show up at all on the linear scale, like the peak in the 400s.

> > The peaks on this graph should correspond directly to the length of
> > the non-preemptible critical section reported by Ingo's latency
> > tracer. I think the large peak around 580-600usecs is caused by the
> > extract_entropy issue (which can be hit by regular processes and
> > ksoftirqd), and the large peak around 80-100 by the XFree86 unmap_vmas
> > issue, as the times match and these are by far the most common
> > reported in latency_trace.
>
> just to check this theory, could you make __check_and_rekey() an empty
> function? This should still produce a working random driver, albeit at
> much reduced entropy. If these latencies have a relationship to the
> mlockall() issue then this change should have an effect.
>

Sure, will try this next.

Lee