That alone doesnt not do almost anything. If you read my later post, you would see that, that is not the main thing.
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Now to a different subject. I have been reading a bit more about Interrupts and the Line based IRQ interrupts being the legacy ones, there seem to be a way to disable it while also not having MSI enabled.
https://community.intel.com/t5/FPGA-Wik ... a-p/736044
https://docs.xilinx.com/r/en-US/pg054-7 ... t-Requests
I started looking it up what could happen if that were to happen. I found no answer, and I end up looking it up using chatgpt, and it gave me an answer.
Here is the trimmed response from the AI
Disabling Legacy Interrupts can potentially bring benefits in certain specialized situations, but it's important to understand that these benefits come with trade-offs and should be carefully considered based on your specific use case. Here are some scenarios where disabling Legacy Interrupts might provide benefits:
1. **Performance Optimization**: In some cases, disabling Legacy Interrupts can lead to marginal performance improvements, especially in high-performance computing (HPC) or real-time systems. This is because Legacy Interrupts can introduce some overhead due to their older design.
2. **Reduced Latency**: Disabling Legacy Interrupts may reduce interrupt latency, which can be critical in real-time applications where low-latency responses are essential. However, modern interrupt handling mechanisms like the Advanced Programmable Interrupt Controller (APIC) are generally more efficient in handling interrupts with low latency.
It's important to emphasize that these potential benefits are relatively narrow in scope and may not apply to typical desktop or server systems running modern operating systems. Disabling Legacy Interrupts can lead to compatibility issues with older hardware and software, which can outweigh any potential performance gains. Additionally, many modern systems and operating systems are designed to handle interrupts efficiently, and Legacy Interrupts are rarely a significant bottleneck.
Before disabling Legacy Interrupts, you should thoroughly understand the implications for your specific hardware and software environment and have a clear reason for doing so. In most cases, it's advisable to leave Legacy Interrupts enabled unless you have a compelling and well-documented reason to disable them.
I asked if that would mean processing in realtime.
Disabling legacy interrupts will not inherently result in processing in real-time. Real-time processing involves ensuring that a system or application responds to events and tasks within a guaranteed and deterministic time frame, meeting specific deadlines. Disabling legacy interrupts alone does not automatically grant real-time capabilities to a system; it's just one factor among many that might affect system responsiveness.
Legacy interrupts refer to older interrupt mechanisms used in x86-based systems, and disabling them might reduce interrupt latency to some extent. However, achieving real-time performance requires a more comprehensive approach:
1. **Real-Time Operating System (RTOS)**: Real-time processing often relies on a specialized Real-Time Operating System (RTOS) that is designed to provide predictable and deterministic response times to tasks and events. RTOSes are optimized for real-time applications and can manage hardware and software resources accordingly.
2. **Priority Scheduling**: Real-time systems use priority-based scheduling to ensure that higher-priority tasks preempt lower-priority ones, allowing critical tasks to be processed promptly.
5. **Interrupt Management**: While disabling legacy interrupts might reduce interrupt latency, real-time systems often rely on a well-managed interrupt system that efficiently handles interrupts for critical tasks. This may involve configuring and optimizing interrupt handlers for real-time responsiveness.
In summary, while disabling legacy interrupts might be one aspect of optimizing a system for lower interrupt latency, achieving true real-time processing involves a holistic approach that encompasses the entire system design, including the use of an RTOS, priority scheduling, deterministic code, and careful hardware and software considerations.
It's a direction to further minimize latency. If people are interested in looking it up further. It would also probably mean making memory changes as to disable it, at least I dont know any other way that would be possible currently.
As for the instant processing answer.
Disabling both MSI (Message Signaled Interrupts) and INTx (legacy interrupt) mechanisms can simplify the interrupt delivery process, but it doesn't guarantee "instant" interrupt processing. There will still be some inherent latency associated with handling interrupts, even with both mechanisms disabled.
Interrupt processing typically involves several steps, such as saving the CPU's current state, jumping to the interrupt handler code, executing the handler, and eventually restoring the saved state. These steps introduce some delay, and disabling MSI and INTx interrupts only removes some of the complexities and potential sources of delay in the delivery mechanism.
The actual processing time for an interrupt also depends on factors such as the efficiency of the interrupt handler code, the priority of the interrupt, and the system's overall load. High-priority interrupts, for example, may be processed more quickly than lower-priority ones.
While you can optimize and streamline the interrupt handling process by disabling MSI and INTx, it won't result in "instant" interrupt processing, as some level of latency is inherent to the way CPUs and operating systems handle interrupts. The goal is to minimize this latency as much as possible, but achieving true instant processing in the context of interrupts may not be feasible due to the underlying hardware and software constraints.
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AI shared a possible way to deactivate INTx (legacy interrupt) and I actually tried with the ethernet device, it just vanish when I did, but since it's a memory change, after a restart, it came back normally.
I dont recommend trying this but I will share here the command and tool.
setpci -s 01:00.0 4.w=0x0000
https://eternallybored.org/misc/pciutils/
01:00.0 is the device address that you have to change from the device you want to make the change on.
In the same zip, there are two executables, one you would use to check the address of the device (lspci.exe), and the other to set (setpci.exe).
