Re: [Xenomai-help] [Fwd: Performance decrease]

[Philippe Gerum <rpm@xenomai.org>]

On Wed, 2006-08-30 at 14:36 +0200, Philippe Gerum wrote:
> -------- Forwarded Message --------
> > From: Daniel Schnell <danielsch@domain.hid>
> > To: xenomai-help <xenomai@xenomai.org>
> > Subject: Performance decrease
> > Date: Wed, 30 Aug 2006 11:58:25 -0000
> > 
> > Hi,
> > 
> >  
> > 
> > I have made some CPU throughput tests with/without "Nucleus options->pervasive real-time support in user-space" 
>  enabled/disabled. And the performance dicrease in using that option is for my processor (MPC5200, 400 MHz) about 10%.

There is an impact induced by activating the user-space support, since
all system calls are filtered through Xenomai; some work is currently
undergoing to reduce this overhead, so that only system calls issued by
Xenomai shadows would be intercepted. This said, out of curiosity, how
do you measure those 10% on your board?

>  On the other side I cannot compile RTDM support in without it; the error message when linking vmlinux
> at the end of the Kernel compile stage is:
> > 
> >  
> > 
> > drvlib.c:(.text+0x19f8): undefined reference to `__va_to_kva'
> > 

I guess that rtdm_mmap_buffer() should be made dependent on
CONFIG_XENO_OPT_PERVASIVE too.

> >  
> > 
> > 
> > 
> > For what is the real-time support in user space option good for ?
> >

This allows running Xenomai applications in user-space, instead of
implementing them as kernel modules.

>  
> > If it is necessary for RTDM support, shouldn't it be automatically switched on when choosing the RTDM option ?
> > 
> >  
> > 
> > 
> > 
> > 
> > 
> > I am using ELDK-4.0 + latest 2.4.25-developer kernel from Denx + latest subversion xenomai + adeos patch 1.1-04
> > 
> >  
> > 
> > Thanks in advance,
> > 
> >  
> > 
> > 
> > 
> > Ciao,
> > 
> >  
> > 
> > Daniel.
> > 
-- 
Philippe.