opus_ramtest Stress Test Guide

This document provides a detailed guide for configuring and running the opus_ramtest stress test on the openvela system. This test evaluates the stability of the system's memory and scheduler under heavy load by concurrently decoding Opus audio data.

I. Overview

opus_ramtest is a stress test tool designed to assess system stability. It creates multiple concurrent child processes (threads), each independently performing high-intensity Opus audio decoding tasks. This applies pressure to two core aspects of the system:

Memory System: Concurrent decoding operations trigger a large volume of memory allocations and deallocations, effectively testing the robustness of the system's memory management. This helps identify issues such as memory leaks, fragmentation, or illegal memory access.
Task Scheduler: A large number of active processes frequently compete for CPU resources, posing a stringent challenge to the operating system's task scheduler. This can be used to evaluate the efficiency, real-time performance, and fairness of the scheduling algorithm.

This test is crucial for verifying the reliability of embedded systems under sustained high loads.

II. Preparation: System Configuration

Before running the test, you must enable and optimize the relevant components in your system build configuration.

1. Enable Core Features

In your defconfig file, ensure the following Kconfig options are enabled to integrate the Opus library and the test program:

CONFIG_LIB_OPUS=y
CONFIG_LIB_OPUS_DEMO=y
CONFIG_TESTING_OPUS_RAMTEST=y

CONFIG_LIB_OPUS=y: Enables the Opus audio codec library.
CONFIG_LIB_OPUS_DEMO=y: Enables the Opus demo code, which opus_ramtest depends on.
CONFIG_TESTING_OPUS_RAMTEST=y: Compiles and enables the opus_ramtest test command.

2. Optimize the Test Environment

To ensure the test can effectively apply pressure, make the following configurations:

Configure the Task Scheduler:
- Set CONFIG_RR_INTERVAL, the time slice for Round-Robin scheduling. Reducing this value increases the frequency of task switching, thereby increasing the scheduling pressure on the system. For example, setting it to 5 (milliseconds) provides good test results.
- CONFIG_RR_INTERVAL=5
Adjust the Main Process Stack Size:
- If a stack overflow occurs when the test process starts, you need to increase the main process's stack space.
- Modify the value of CONFIG_TESTING_OPUS_RAMTEST_STACKSIZE. The default value is 40960 bytes.

III. Executing the Test

1. Disable the Watchdog

Prolonged stress testing may slow down system responsiveness, potentially triggering a watchdog reset. Before testing, use the following command to disable the watchdog:

echo V > /dev/watchdog0

2. Run the Test Command

Start the test using the opus_ramtest command. The following is a recommended command:

# The -s parameter sets a 40960-byte stack for each child process
opus_ramtest -s 40960

IV. Command-Line Parameter Details

The opus_ramtest command supports several parameters to customize its behavior.

Parameter	Description	Default Value
`-s`	(Required) Sets the stack size (in bytes) for each created child process (thread). On embedded devices, `pthread` may use a small default stack, so you must use this parameter to allocate sufficient space to prevent overflow.	N/A
`-n`	Specifies the number of concurrent child processes for decoding tasks. Note: This value should not be set too high to avoid exhausting system resources.	`5`
`-r`	Sets the scheduling priority for the child processes.	N/A
`-f`	Specifies the path to an external Opus audio file for decoding. If this parameter is not provided, the test will use its built-in audio data array.	Built-in array

V. Important Notes

Built-in Data Source Size:
- The test tool includes a built-in static array of approximately 250 KB, which serves as the default audio data source. Ensure your target hardware has enough RAM to accommodate this array and the additional overhead from the test itself.

VI. References

Opus Official Website: Get the latest information, specifications, and resources for the Opus codec.
Opus IETF RFC 6716: The authoritative technical standard for the Opus codec, published by the Internet Engineering Task Force (IETF).