I'm happy to report that after adapting hal_parport to use inb/outb I/O instead 
of ppdev-ioctl, there are no more realtime delays with a soft stepgen/parport 
based configuration (atom DW5252, kernel 3.2.21-xenomai+).

I would think this can now tried on real machines:

http://git.mah.priv.at/gitweb/emc2-dev.git/shortlog/refs/heads/rtos-integration-preview1


- Michael

ps: it is interesting to see that soft stepgen takes a lot more CPU than the 
whole motion, kins and trajectory processing chain - I would have guessed the 
other way around (so much for intuition versus measurement ;):


root@atom:~# cat /proc/xenomai/stat 
CPU  PID    MSW        CSW        PF    STAT       %CPU  NAME
  0  0      0          8922182    0     00500080   96.4  ROOT/0
  1  0      0          200972431  0     00500080   81.4  ROOT/1
  1  22635  0          4895605    0     00300184   17.3  base-thread    
<-------- isolated CPU doing soft stepgen
  0  22636  0          244779     0     00300184    3.3  servo-thread   <----- 
motion/kins/trajectory 
  0  0      0          10740483   0     00000000    0.3  IRQ2312: [timer]


The only config change I did relative to stock configs/stepper/stepper_mm.ini 
was explicit CPU assignment, see man threads and man motion for details:

diff mah_stepper.hal core_stepper.hal 
7c7
< loadrt [EMCMOT]EMCMOT base_period_nsec=[EMCMOT]BASE_PERIOD base_cpu=1 
servo_period_nsec=[EMCMOT]SERVO_PERIOD servo_cpu=0 num_joints=[TRAJ]AXES
---
> loadrt [EMCMOT]EMCMOT base_period_nsec=[EMCMOT]BASE_PERIOD 
> servo_period_nsec=[EMCMOT]SERVO_PERIOD num_joints=[TRAJ]AXES



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