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. - 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? - Stability seems already quite good. At least I did not observe any crash yet :-). The PowerPC port of Xenomai is already in good shape. That's great! 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-latencies-ppc.tgz
Description: GNU Zip compressed data
