performance-measurement

Performance Measurement

Background

• Here is a list of load measurement for several hardware and software configuration. The drivers ran in Profibus DP Master mode.
• Information is taken from the /proc/stat file. Load is counted as summary of time the CPU spent in system mode, hardIRQ and softIRQ. I unloaded all the unnecessary drivers before testing so the load is only a little bit higher then the real load caused by the PBMaster Drivers.
• The interrupt throughput is a number of interrupts the PC/Linux is capable to handle.
• I'm not sure about the correctness of the measurement. Please let me know if you have better idea to measure the load.
• The results are outputs of a script I have created to do it automatically, because it's a very time consumption task to do manually. If you have any converter and want to participate, please run the script and send me the outputs or just copy and paste it to these wiki pages. The script can be found in src/scripts/load-measurement.pl (since version 0.2.0pre3).
• CPU load of the simple RS-232/RS-485 dongle is not listed here because it's very low (a few percent) for both supported speeds.

Conclusion

• From the measurement I would recommend to use the drivers with Linux kernel without the CONFIG_PREEMPT neither CONFIG_PREEMPT_RT option enabled. Without this option the load is very low and latency for the user applications is also very short. None the less the real-time patched kernel could serve better for some circumtances, for example when another hardware driver is also occupying a lot the CPU. In this case you can set the priority of the PBMaster drivers higher as well as priority of the user application using the drivers.
• Make sure the RS-485 differential bus tranceiver is capable to work correctly at the required communication speed. The capacity of transil, in the role of protection, may also influence function of the card. For applications requiring the highest communication speed 12Mbps you will need for example this ADM1485 transceiver.

OXmPCI954 integrated PCI cards

No.	Converter	PC Hardware	OS/Kernel	Driver version	Tested by	Results	Notes
1	Tedia PCI-1482U	AMD Athlon 2800+	Linux 2.6.24 vanilla	0.2.0pre3	TDK	Test PCI 1	Recommended configuration With bus transceiver ADM1485
2	Tedia PCI-1482U	Pentium III 600MHz	Linux 2.6.26-1-486 Debian	0.2.0pre3	TDK	Test PCI 2	Tested with the Live CD With bus transceiver ADM1485
3	Tedia PCI-1472	AMD Athlon 2800+	Linux 2.6.26 RT	0.2.0pre3	TDK	Test PCI 3	Real-time Patch (CONFIG_PREEMPT_RT=y) Max. usable speed is limited by the bus transceiver
4	Tedia PCI-1482U	Pentium 4, 3.00GHz	Linux 2.6.23-gentoo-r9	0.2.0pre3	TDK	Test PCI 4	Recommended configuration With bus transceiver ADM1485
5	Tedia PCI-1482U	AMD Athlon 2800+	Linux 2.6.17.9 vanilla	0.2.0pre3	TDK	Test PCI 5	Recommended configuration With bus transceiver ADM1485
6	Tedia PCI-1482U Tedia PCI-1472	AMD Athlon 2800+	Linux 2.6.24 vanilla	0.2.0pre4	TDK	Test PCI 6	Recommended configuration 2 cards
7	Tedia PCI-1482U Tedia PCI-1472	AMD Athlon 2800+	FreeBSD 7.0-RELEASE	0.3.0pre1	TDK	Test PCI 7	Recommended configuration 2 cards