Infoportal
Unterschiede
Hier werden die Unterschiede zwischen zwei Versionen angezeigt.
| Beide Seiten der vorigen RevisionVorhergehende ÜberarbeitungNächste Überarbeitung | Vorhergehende Überarbeitung | ||
| software:linux:realtime:benchmark:start [2019-02-11 16:09] – mgehrig2 | software:linux:realtime:benchmark:start [2023-04-11 11:17] (aktuell) – gelöscht Urs Graf | ||
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| - | ====== Benchmark ======= | ||
| - | ===== Introduction ===== | ||
| - | There are many different tools available to measure the realtime performance of a system. | ||
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| - | The cyclictest is the simplest and most usefull benchmark. | ||
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| - | ===== Tools ===== | ||
| - | ==== Cyclictest ==== | ||
| - | Standard tool to measure the maximum jitter of a system. | ||
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| - | **[[software: | ||
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| - | ===== Influences on real-time behaviour ===== | ||
| - | The following things can influence the real-time behaviour: | ||
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| - | * CPU | ||
| - | * Mobile x86 CPU (with suffix like U, Y and M i.e i7-4600U) seems to perform much worse than non-mobile processors. Mobile processer add about 100us-200us jitter. | ||
| - | * ARM processer seem to have about 60us max jitter and a high medium jitter | ||
| - | * Kernel version | ||
| - | * 4.4.169-rt177 seems to be better than 4.19.15-rt12 | ||
| - | * BIOS settings | ||
| - | * Some drivers, like WiFi driver, may negatively influence latency | ||
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| - | ===== Methodical procedure ===== | ||
| - | ==== Overview ==== | ||
| - | At first, test the most basic system possible. | ||
| - | With this test, you can get a baseline of the best possible real-time performance of the hardware. | ||
| - | Every feature added will make the system more complex and add more stuff, which can increase jitter. | ||
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| - | With this approach you can get a feeling which performance is possible and which part of the system is responsible for a high jitter. | ||
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| - | - Test hardware, BIOS settings and kernel version | ||
| - | - Test full distro in text mode | ||
| - | - Test full distro in graphical mode | ||
| - | - Test full distro under load | ||
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| - | ==== 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: | ||
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| - | **Tipp**: You may want to use [[https:// | ||
| - | This application provides multiple virtual terminal sessions when you want to run multiple programs in parallel.. | ||
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| - | === Tuning === | ||
| - | If you the measured latencies are to high, you can tweak your system. | ||
| - | The options which are simple but effective are listed first. | ||
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| - | * Tune some [[software: | ||
| - | * Tune some kernel settings TODO | ||
| - | * Use a different kernel version. (4.4.169-rt177 seems to be better than 4.19.15-rt12) | ||
| - | * If the jitter is still too high, you may have to choose a different CPU | ||
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| - | ==== 2.) Test full distro in text mode ==== | ||
| - | Boot your system in [[software: | ||
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| - | 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. | ||
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| - | 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. | ||
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| - | === Other possible causes === | ||
| - | * WLAN driver | ||
| - | * Ethernet Triber | ||
| - | * Bluetooth driver | ||
| - | * Various peripheral devices | ||
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| - | ==== 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. | ||
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| - | If, however, the system is to be used with a graphical user interface, a 24h test [[software: | ||
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| - | ==== 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. | ||
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| - | Check the temperature of the CPU under high load with [[https:// | ||
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| - | If the processor does overheat: | ||
| - | * Disable hyperthreading in BIOS | ||
| - | * Deactivate Turboboost in BIOS | ||
| - | * Ensure better cooling | ||
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| - | **Note ***: Depending on the processor, // | ||
| - | Observe the // | ||
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| - | === 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. | ||
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