Re: [Xenomai-core] Xenomai latency tests on various PowerPC boards

[Wolfgang Grandegger <wg@domain.hid>]

On 10/18/2005 08:14 PM Philippe Gerum wrote:
> Wolfgang Grandegger wrote:
>> On 10/18/2005 01:44 PM Philippe Gerum wrote:
>> 
>>>Philippe Gerum wrote:
>>>
>>>>Wolfgang Grandegger wrote:
>>>>
>>>>
>>>>>Hallo,
>>>>>
>>>>>attached you will find the results of Xemonai latency measurements on
>>>>>various embedded PowerPC boards using MPC 8xx and AMCC 4xx processors,
>>>>>from low to high end covering a worst case latency range from 25 to 225
>>>>>us. It also includes a comparison with RTAI 3.0r5 on the slowest CPU.
>>>>>Here are some remarks and comments:
>>>>>
>>>>>- On low-end processor code size matters a lot and it's difficult to
>>>>>  beat RTAI/RTHAL.
>>>>>
>>>>
>>>>Beat no, get closer, yes, probably. The good news is that looking at the 
>>>>figures, we do have a margin of improvement! :o>
>>>>
>>>>Btw, the nucleus can be configured so that the user-space threading 
>>>>engine is compiled out (i.e. CONFIG_XENO_OPT_PERVASIVE from the nucleus 
>>>>menu), which would be the corresponding profile to compare with klatency 
>>>>(i.e. sched_up). Disabling this option reduces the code size for the 
>>>>nucleus from:
>>>>
>>>>   text       data        bss        dec        hex    filename
>>>>  66740        792       6540      74072      12158    
>>>>nucleus/xeno_nucleus.ko
>>>>
>>>>to:
>>>>
>>>>  text       data        bss        dec        hex    filename
>>>>  52596        576       3956      57128       df28    
>>>>nucleus/xeno_nucleus.ko
>>>>
>>>
>>>Disabling the periodic timer support which is unused for the klatency test 
>>>brings this down to:
>>>
>>>    text	   data	    bss	    dec	    hex	filename
>>>   51040	    544	   3956	  55540	   d8f4	nucleus/xeno_nucleus.ko
>> 
>> 
>> OK, here are the new figures with (*)
>> 
>>  CONFIG_XENO_OPT_PERVASIVE is not set
>>  CONFIG_XENO_HW_PERIODIC_TIMER is not set:
>> 
>>            |-----lat min|-----lat avg|-----lat max|-overrun|---test-time
>> RTAI 3.0r5 |       23120|       31838|       70520|       ?|    00:12:26
>> Xenomai    |       50560|       98976|      199040|       0|    00:09:45
>> Xenomai (*)|       44160|       96215|      200640|       0|    00:09:53
>> 
>> The min latency decreases as expected.
>> 
> 
> I just discovered that -00 did not include some recent changes I had in my tree, 
> aimed at prevent high latencies during fork pressure. I've committed -01 which 
> does include them. When time allows, I'd be interested to know if this has some 
> impact on the Ocotea figures. TIA,

bash-2.05b# cat /proc/ipipe/version
1.0-01

SWITCH without load:

== Sampling period: 100 us
RTH|     lat min|     lat avg|     lat max|        lost
RTD|        5158|        5169|       10038|           0   iPipe 1.0-00
RTD|        5145|        5154|       10166|           0   iPipe 1.0-01

KLATENCY with load:

RTH|-----lat min|-----lat avg|-----lat max|-overrun|----lat best|---lat
worst
RTS|        2953|        5974|       19147|       0|    00:12:05 1.0-00
RTS|        3035|        8705|       20705|       0|    00:09:54 1.0-01

LATENCY with load:

== Sampling period: 100 us
RTH|-----lat min|-----lat avg|-----lat max|-overrun|----lat best|---lat
worst
RTS|        3575|        7438|       24474|       0|    00:10:50 1.0-00
RTS|        3553|       10125|       23970|       0|    00:09:41 1.0-01

It has no significant impact, I think.

Wolfgang.