IRQ latency and context switching on mvme5500 (was Re: RTEMS mvme5500 bsp)

[Kate Feng]

>  Interested, yes, but I really have no time right now
> to have a closer look at it -- can you summarize the results?

Based on the test  result, it shows that  RTEMS-mvme5500 is
more deterministic  and  steadier than vxWorks-mvme5500
for the highest priority task.  For  both  the idle  and loaded system,
RTEMS-mvme5500 "GUARANTEED"  twice or three times
faster response time in a steadier state.     The "worst case" is a
critical factor  in consideration of the real-time  system.


Regards,
Kate

Kate Feng wrote:

>
>
> I finally got around to  optimize the IRQ handling and
> prioritization.  Many thanks to Till Straumann of SLAC
> for  providing  some  suggestions. I modified (for  MVME5500)
> the  latency benchmark  software which Till  posted
> on http://www.slac.stanford.edu/~strauman/rtoslat/
>
> The test was performed on the MVME5500 board.  2,000,000
> timer interrupts were generated at a  rate of  4KHZ.  The
> maximum and average  letencies for both the  idle and loaded
> system were measured.   The loaded system was subject to heavy
> network and console activities.  Please note that the worst case
> (e.g. maximum) is  critical  for a real-time system.
>
> The result is  listed below.  Based on the new algorithm, the result
> for a VME interrupt in RTEMS should be very close to what is listed
> as long as it's set at the highest priority  in irq_init.c.   Please
> let
> me
> know otherwise.  Any suggestions or  comments before I submitted
> the patch ?    Also, the updated software fixed the  bug of
> the irq->on() API, which was reported back in Feb..   -- Kate
>
> ______________________________________________________
> MVME5500    Interrupt   Latency    |   Context Switching
> _________________________________________________________
>                            max      (average)   |     max    (average)
>
> _________________________________________________________
> Idle System:                                      |
>
> RTEMS          5.04       (3.45)           |    6.80     (0.96)
>
> vxWorks       12.13       (1.58)          |   18.68     (0.91)
>
> _________________________________________________________
> Loaded System:
>
> RTEMS          8.17       (3.74)          |   24.88     (1.69)
>
> vxWorks       22.49       (2.04)         |   40.76     (4.1)
> _________________________________________________________
>
> ** All units are in usec.