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{{AppliesToAxel}}
{{AppliesToAxelLite}}
{{AppliesToAXEL Lite AN}}
{{AppliesToSBCX}}
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{{WarningMessage|text=This application note was validated against specific versions of the kit only. It may not work with other versions. Supported versions are listed in the ''History'' section.}}
|Update for XELK 2.0.0 release
|-
|[httphttps://www.dave.eu/siteslinks/defaultp/files/files/an-xelk-001-amp-linux-freertos.pdf 0qKejH20HFSu3oWn 0.9.3]
|April 2015
|2.0.0
|2.1.0
|Minor improvements
|-
|1.0.2
|October 2018
|2.1.0
|Added some details about <code>latencystat</code> test application
|}
<pre class="board-terminal">
root@axel-lite:~# ./latencystat -b
Linux FreeRTOS AMP Demo.
total samples: 1592
-----------------------------------------------------------
</pre>
This application is extremely useful for characterizing how measuring interrupt latency and for verifying how it is affected depending on by relevant parameters such as the CPU load on the first core and other parameters (, memory bandwidth utilization, number the amount/rate of interrupts to be processed by the first core, operating frequency, etc.).
For instance, the previous data refer to the following configuration:
*[[FAQs_(Axel)#Q:_How_can_I_change_the_CPU_clock_frequency.3F|governor]]: <code>userspace</code>
*nominal operating frequency: 800 MHz (actual: 792 MHz)
*core #0 (running Linux) lightly loadedwith minimal I/O activity.
In general, it is strongly recommended to characterize the latency on the basis of a '''realistic testbed that is as close as possible to the actual use case'''. It is also worth remembering that, in case of latency does not satisfy the application's real-time requirements, it is possible to adjust the arbitration priorities of processor's interconnect subsystem to reduce it.