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

[Wolfgang Grandegger <wg@domain.hid>]

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.

> 
>> Still a bit fat though.
>> 
>>> - Apart from the CPU power, big caches and a fast memory interface
>>>   improves latencies.
>>>
>>> - L2 cache improves latencies a lot (compare Ocotea with Yosemite).
>>>
>>> - I'm a bit puzzled about the results of the "cruncher" test. Could
>>>   someone explain the output, please?
>>>
>> 
>> This test is reminiscent of the HYADES project (ia64 port of 
>> RTAI/fusion), where we wanted to illustrate the level of execution 
>> determinism one could achieve using the interrupt shield technique on 
>> large ia64 SMP systems. To this end, we measured the jitter in execution 
>> time of a calibrated float-crunching loop, with and without interrupt 
>> load. This test is likely going to disappear at some point in time, 
>> because it's not that informative in Xeno's context.
>> 
>>> - Stability seems already quite good. At least I did not observe any
>>>   crash yet :-).
>>>
>> 
>> That's cool. I see no other way to properly improve performances than 
>> first having something which could be run on various platforms without 
>> them randomly jumping out of the window, or us relying on plain Voodoo 
>> stuff to explain why those setup would work or not.
>> 
>>> The PowerPC port of Xenomai is already in good shape. That's great!
>>>
>> 
>> Thanks. This is likely because I do feel better since I have been aware 
>> that there's life beyond x86. :o)
>> 
>>> Wolfgang.
>>>
>>>
>>>
>>>
>>>
>>> ------------------------------------------------------------------------
>>>
>>> Latency tests with Xenomai on various PowerPC boards
>>> ----------------------------------------------------
>>>
>>> Board   : Processor  CPU-Clk Bus-Clk I-Cache D-Cache Memory Remarks
>>>
>>> TQM860L : MPC 860     50 MHz  50 MHz    4 KB    4 kB  16 MB
>>> TQM866M : MPC 866    133 MHz  66 MHz   16 KB    8 kB 128 MB
>>>
>>> Walnut  : AMCC 405GP 200 MHz 100 MHz   16 KB    8 kB  32 MB
>>> Yosemite: AMCC 440EP 533 MHz 133 MHz   32 KB   32 KB 256 MB DDR-RAM, FPU
>>> Ocotea  : AMCC 440GX 533 MHz 152 MHz   32 KB   32 KB 256 MB DDR-RAM, 
>>> L2 256 KB
>>>
>>>
>>> Linux  : DENX linux-2.6.14-rc3-g4c234921
>>> iPipe  : 1.0-00
>>> Xenomai: SVN 2005-10-15
>>>
>>>
>>> CRUNCER without load:
>>>
>>>          | Ideal computation time
>>> TQM860L  |   368 us ???
>>> TQM866L  | 10008 us Walnut   | 10150 us
>>> Yosemite |  9911 us
>>> Ocotea   |  9479 us
>>>
>>> SWITCH without load:
>>>
>>>          |     lat min|     lat avg|     lat max|        lost
>>> TQM860L  |      103360|      107840|      209280|           0
>>> TQM866L  |       25745|       31880|       51369|           5
>>> Walnut   |       24620|       25965|       32280|           1
>>> Yosemite |        5626|        5655|       17403|           0
>>> Ocotea   |        5158|        5169|       10038|           0
>>>
>>>
>>> KLATENCY with load:
>>>
>>>          |-----lat min|-----lat avg|-----lat max|-overrun|---test-time
>>> TQM860L  |       50560|       98976|      199040|       0|    00:09:45
>>> TQM866L  |       13835|       28571|       74348|       0|    00:11:44
>>> Walnut   |       16195|       25062|       45755|       0|    00:10:09
>>> Yosemite |        3106|        9697|       36832|       0|    00:09:55
>>> Ocotea   |        3575|        7438|       24474|       0|    00:10:50
>>>
>>>
>>> LATENCY with load:
>>>
>>>          |-----lat min|-----lat avg|-----lat max|-overrun|---test-time
>>> TQM860L  |       60480|      120960|      224320|       0|    00:09:46
>>> TQM866L  |       15759|       34286|       78799|       0|    00:11:14
>>> Walnut   |       21070|       31650|       64500|       0|    00:09:58
>>> Yosemite |        3808|       12163|       47898|       0|    00:10:00
>>> Ocotea   |        3575|        7438|       24474|       0|    00:10:50
>>>
>>>
>>> KLATENCY comparison Xenomai 2.0 vs. RTAI/RTHAL 3.0r5 on TQM860L:
>>> ---------------------------------------------------------------
>>>
>>> KLATENCY with load:
>>>
>>>             |-----lat min|-----lat avg|-----lat max|-overrun|---test-time
>>> Xenomai 2.0 |       50560|       98976|      199040|       0|    00:09:45
>>> RTAI 3.0r5  |       23120|       31838|       70520|       ?|    00:12:26
>>>
>>>
>>>
>>> Note: load has been put onto the system by running in a telnet session
>>>       "ping -f <remote-host-ip>" and "while ls; do ls; done".
>>>
>>> Note: all test have been run with CONFIG_XENO_HW_TIMER_LATENCY="1" and
>>>       CONFIG_XENO_HW_SCHED_LATENCY="1" to get correct latancy values.
>>>       RTAI figures have been corrected manually.
>>>
>>>
>>>
>>>
>>> ------------------------------------------------------------------------
>>>
>>> _______________________________________________
>>> Xenomai-core mailing list
>>> Xenomai-core@domain.hid
>>> https://mail.gna.org/listinfo/xenomai-core
>> 
>> 
>> 
> 
>