Bob Explores Real-Time Applications with AlmaLinux

Optimize AlmaLinux for real-time applications, where ultra-low latency and deterministic response times are critical.

By İbrahim Korucuoğlu ( @siberoloji) | Thursday, December 12, 2024

Categories:

Linux

Bob’s next adventure was to optimize AlmaLinux for real-time applications, where ultra-low latency and deterministic response times are critical. From configuring the real-time kernel to tuning the system, Bob aimed to create an environment suitable for industrial automation, telecommunications, and other time-sensitive workloads.

“Real-time computing is all about speed and precision—let’s make AlmaLinux the fastest it can be!” Bob said, ready to dive in.

Chapter Outline: “Bob Explores Real-Time Applications with AlmaLinux”

Introduction: What Are Real-Time Applications?
- Overview of real-time computing and use cases.
- Hard real-time vs. soft real-time.
Setting Up a Real-Time Kernel
- Installing and enabling the real-time kernel.
- Verifying real-time kernel features.
Tuning AlmaLinux for Real-Time Performance
- Configuring system parameters for low latency.
- Optimizing CPU isolation and scheduling.
Testing and Measuring Latency
- Using tools like cyclictest for latency analysis.
- Interpreting test results to identify bottlenecks.
Implementing Real-Time Applications
- Running a real-time application on the configured system.
- Managing resources to ensure predictable performance.
Monitoring and Maintaining Real-Time Systems
- Continuous monitoring with performance tools.
- Ensuring system stability and reliability.
Conclusion: Bob Reflects on Real-Time Optimization

Part 1: What Are Real-Time Applications?

Bob learned that real-time systems guarantee a specific response time to events, which is critical in applications like robotics, video streaming, and financial trading.

Hard vs. Soft Real-Time

Hard Real-Time: Failure to respond within the deadline is unacceptable (e.g., medical devices).
Soft Real-Time: Occasional missed deadlines are tolerable (e.g., live video streaming).

“AlmaLinux can handle both types of real-time tasks with the right tweaks!” Bob said.

Part 2: Setting Up a Real-Time Kernel

Step 1: Installing the Real-Time Kernel

Add the real-time repository:

sudo dnf install -y epel-release
sudo dnf install -y kernel-rt kernel-rt-core

Update the GRUB configuration to use the real-time kernel:
```
sudo grub2-mkconfig -o /boot/grub2/grub.cfg
```
Reboot into the real-time kernel:
```
sudo reboot
```

Step 2: Verifying Real-Time Kernel Features

Check the active kernel version:
```
uname -r
```
Verify real-time patches:
```
dmesg | grep -i "rt"
```

“The real-time kernel is installed and ready to go!” Bob said.

Part 3: Tuning AlmaLinux for Real-Time Performance

Step 1: Configuring CPU Isolation

Edit the GRUB configuration to isolate CPUs for real-time tasks:
```
sudo nano /etc/default/grub
```
Add the following to GRUB_CMDLINE_LINUX:
```
isolcpus=2,3 nohz_full=2,3 rcu_nocbs=2,3
```

Update GRUB and reboot:

sudo grub2-mkconfig -o /boot/grub2/grub.cfg
sudo reboot

Step 2: Adjusting Kernel Parameters

Optimize for low latency:

sudo sysctl -w kernel.sched_rt_runtime_us=-1

Persist the change:

echo "kernel.sched_rt_runtime_us=-1" | sudo tee -a /etc/sysctl.conf

Step 3: Using Priority Scheduling

Allow non-root users to use real-time priorities:

sudo nano /etc/security/limits.conf

Add:

* hard rtprio 99
* soft rtprio 99

“CPU isolation and priority scheduling ensure real-time tasks aren’t interrupted!” Bob said.

Part 4: Testing and Measuring Latency

Step 1: Installing `cyclictest`

Install cyclictest from the rt-tests package:
```
sudo dnf install -y rt-tests
```

Step 2: Running Latency Tests

Run cyclictest to measure latency:

sudo cyclictest --smp --threads=4 --priority=99 --interval=1000

Interpret the results:
- Max Latency: The longest time the system took to respond.
- Average Latency: The average response time.

“Low and stable latencies mean my system is ready for real-time workloads!” Bob noted.

Part 5: Implementing Real-Time Applications

Step 1: Writing a Real-Time Program

Bob wrote a simple real-time program in C:

#include <stdio.h>
#include <time.h>
#include <sched.h>

int main() {
    struct sched_param param;
    param.sched_priority = 99;
    if (sched_setscheduler(0, SCHED_FIFO, &param) == -1) {
        perror("sched_setscheduler failed");
        return 1;
    }
    while (1) {
        struct timespec ts;
        clock_gettime(CLOCK_REALTIME, &ts);
        printf("Real-time task running at %ld.%09ld ", ts.tv_sec, ts.tv_nsec);
    }
    return 0;
}

Compile and run the program:

gcc -o realtime realtime.c
sudo ./realtime

Step 2: Managing Resources

Use taskset to bind the program to specific CPUs:
```
sudo taskset -c 2 ./realtime
```

“Real-time applications run smoothly when system resources are managed effectively!” Bob said.

Part 6: Monitoring and Maintaining Real-Time Systems

Step 1: Monitoring System Performance

Use htop to monitor CPU usage:
```
htop
```
Monitor kernel events:
```
dmesg -T | tail
```

Step 2: Ensuring System Stability

Schedule regular health checks:

crontab -e