Re: preempt-rt, NUMA and strange latency traces

[Lee Revell <rlrevell@joe-job.com>]

On Thu, 2006-02-09 at 12:24 +0100, Sébastien Dugué wrote:
> On Thu, 2006-02-09 at 01:04 -0500, Lee Revell wrote:
> > On Wed, 2006-02-08 at 11:45 +0100, Sébastien Dugué wrote:
> > > The more I think about it, the more I tend to believe it's hardware 
> > > related. It seems as if the CPU just hangs for ~27 ms before
> > > resuming processing. 
> > 
> > That would be an exceptionally long latency - you would probably notice
> > it if the mouse froze, VOIP dropped out, ping stops, etc for 30ms.
> > 
> 
>   It's a test machine and I use it remotely with console redirected so
> no mouse, no RT applications aside from my silly nanosleep() loop. But 
> I do notice that that test sometimes takes more time (ie when I get 
> those weird latencies). 

Argh.  You would think the vendors would consider a 30ms delay
unacceptable.  This is big enough to show up on an MRTG graph of ping
times ferchrissake.

I guess the assumption is that most hardware will never be used for even
soft RT work...

Lee