Infoportal
Unterschiede
Hier werden die Unterschiede zwischen zwei Versionen angezeigt.
| Beide Seiten der vorigen RevisionVorhergehende ÜberarbeitungNächste Überarbeitung | Vorhergehende ÜberarbeitungLetzte ÜberarbeitungBeide Seiten der Revision | ||
| software:linux:realtime:benchmark:start [2019-02-08 16:02] – mgehrig2 | software:linux:realtime:benchmark:start [2023-04-11 11:16] – Urs Graf | ||
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| Zeile 9: | Zeile 9: | ||
| Standard tool to measure the maximum jitter of a system. | Standard tool to measure the maximum jitter of a system. | ||
| - | **[[software: | + | **[[..: |
| Zeile 17: | Zeile 17: | ||
| * CPU | * CPU | ||
| - | * Mobile x86 CPU (with suffix like U, Y and M i.e i7-4600U) seems to performe | + | * Mobile x86 CPU (with suffix like U, Y and M i.e i7-4600U) seems to perform |
| * ARM processer seem to have about 60us max jitter and a high medium jitter | * ARM processer seem to have about 60us max jitter and a high medium jitter | ||
| * Kernel version | * Kernel version | ||
| Zeile 23: | Zeile 23: | ||
| * BIOS settings | * BIOS settings | ||
| * Some drivers, like WiFi driver, may negatively influence latency | * Some drivers, like WiFi driver, may negatively influence latency | ||
| + | |||
| + | ==== Don't ==== | ||
| + | * Don't start the application 'Grub customizer' | ||
| + | |||
| + | |||
| + | ==== Does ==== | ||
| + | * You should remove as many of the unknowns as possible. This means that only the necessary drivers should be loaded. | ||
| + | * If possible, use only a text based system. See ' | ||
| + | * Run only software that is absolutely necessary on the real-time master. | ||
| + | * Deactivate automatic updates. | ||
| + | * A stable system can only be guaranteed if it has been sufficiently tested. Each system is different and must be tested. | ||
| + | |||
| ===== Methodical procedure ===== | ===== Methodical procedure ===== | ||
| ==== Overview ==== | ==== Overview ==== | ||
| At first, test the most basic system possible. | At first, test the most basic system possible. | ||
| - | With this test, you can get a baseline of the best possible real-time | + | With this test, you can get a baseline of the best possible real-time |
| - | Every feature added will make the system more complex and add more stuff which can increase jitter. | + | Every feature added will make the system more complex and add more stuff, which can increase jitter. |
| + | |||
| + | With this approach you can get a feeling which performance is possible and which part of the system is responsible for a high jitter. | ||
| + | |||
| + | |||
| + | - Test hardware, BIOS settings and kernel version | ||
| + | - Test full distro in text mode | ||
| + | - Test full distro in graphical mode | ||
| + | - Test full distro under load | ||
| + | |||
| + | ==== 1.) Test hardware, BIOS settings and kernel version ==== | ||
| + | - Build a [[software: | ||
| + | - Install the [[software: | ||
| + | - Reboot with the new kernel in [[software: | ||
| + | - Check the real-time performance with [[software: | ||
| + | |||
| + | **Tipp**: You may want to use [[https:// | ||
| + | This application provides multiple virtual terminal sessions if you want to run multiple programs in parallel.. | ||
| + | |||
| + | === Tuning === | ||
| + | If you the measured latencies are to high, you can tweak your system. | ||
| + | The options which are simple but effective are listed first. | ||
| + | |||
| + | * Tune some [[software: | ||
| + | * Use a different kernel version. (4.4.169-rt177 seems to be better than 4.19.15-rt12) | ||
| + | * Tune some kernel settings TODO | ||
| + | * If the jitter is still too high, you may have to choose a different CPU | ||
| + | |||
| + | |||
| + | ==== 2.) Test full distro in text mode ==== | ||
| + | Boot your system in [[software: | ||
| + | |||
| + | If the real-time performance is not significantly reduced, then the third step can be continued. | ||
| + | Run a 24h test so that exceptional events can also be detected. | ||
| + | |||
| + | If the real-time performance is significantly worse, then a WLAN driver or something similar can be the cause. | ||
| + | To further isolate the problem, the WLAN driver, or another suspected driver, can be deactivated ('' | ||
| + | A new test should result in an improvement of the maximum jitter. | ||
| + | |||
| + | === Other possible causes === | ||
| + | * WLAN driver | ||
| + | * Ethernet driver | ||
| + | * Bluetooth driver | ||
| + | * Various peripheral devices | ||
| + | |||
| + | |||
| + | ==== 3.) Test full distro in graphical mode ==== | ||
| + | It is recommended that a real-time system be used only in text mode. | ||
| + | With a graphical user interface, the system is generally more unstable. | ||
| + | |||
| + | If, however, the system is to be used with a graphical user interface, a 24h test [[software: | ||
| + | |||
| + | |||
| + | ==== 4.) Test full distro under load ==== | ||
| + | === High CPU load === | ||
| + | High CPU load from non-RT processes does not affect the performance of RT processes very much. | ||
| + | However, if the processor is not sufficiently cooled (e.g. in a mobile system), the processor can overheat. | ||
| + | In such a case, the processor clock is clocked down by the system, which can severely impair real-time performance. | ||
| - | With this aproach you can get a feeling which performance is possible and which part of the system is responsible for a high jitter. | + | Check the temperature |
| + | If the processor does overheat: | ||
| + | * Disable hyper.threading in BIOS | ||
| + | * Deactivate Turboboost in BIOS | ||
| + | * Ensure better cooling | ||
| + | **Note ***: Depending on the processor, // | ||
| + | Observe the // | ||
| + | === Normal Load === | ||
| + | In the last test allplitkation are to be started, which are to run also later in the employment. | ||
| + | For the // | ||
| + | This test should last at least 24 hours. | ||