Re: PREEMPT_RT vs ADEOS: the numbers, part 1

[Ingo Molnar <mingo@elte.hu>]

* James R Bruce <bruce@andrew.cmu.edu> wrote:

> Ingo, if you could document the right options required for decent 
> performace somewhere it would be quite helpful (maybe in 
> Documentation/rt-preempt?).  My first test of Preempt-RT showed 
> unexpectedly high overhead for a fairly benign network load (120 UDP 
> packets/sec), but that was likely the result of leaving some debugging 
> options on.

agreed, this needs to be addressed.

in the latest patch (-48-17 or later) i have changed the debugging 
options to default to off. (this wont turn them off if your .config has 
them turned on already, but will turn them off for new testers' 
.configs)

I also added a prominent boot-time message that, if certain 
high-overhead debugging options are enabled, says:

*****************************************************************************
*                                                                           *
* WARNING, the following debugging options are turned on in your .config:   *
*                                                                           *
*        CONFIG_DEBUG_RT_LOCKING_MODE                                       *
*        CONFIG_RT_DEADLOCK_DETECT                                          *
*        CONFIG_DEBUG_PREEMPT                                               *
*        CONFIG_CRITICAL_PREEMPT_TIMING                                     *
*        CONFIG_CRITICAL_IRQSOFF_TIMING                                     *
*        CONFIG_LATENCY_TRACE                                               *
*        CONFIG_DEBUG_SLAB                                                  *
*                                                                           *
* they may increase runtime overhead and latencies considerably!            *
*                                                                           *
*****************************************************************************

wrt. documentation - i'm not a big doc writer, but i'm taking patches
:-)

	Ingo