The Linux kernel is the backbone of Linux operating systems (OS), and is the fundamental interface between a computer's hardware and its processes.
Recently version 6.2 of the Linux Kernel was released, which comes with a series of quite good features, in addition to adding hardware compatibility improvements and above all that it continues with the improvements of "Rust For Linux", without a doubt a temporary version that opens many windows to various improvements for Linux 6.3 (If you want to know more about the release of Kernel 6.2, you can check the details in this post).
For what will be the next version of the Linux Kernel, various features are being adjusted that are carried out through confirmations and of which one of the important features which has been added to Linux 6.3 is the new tool rtla hwnoise.
rtla hwnoise (realtime linux scan hardware noise) is a tool to detect and quantify hardware related noise. Retrieves the periodic summary of the running osnoise tracker with interrupts disabled.
By disabling interrupts and thread scheduling, only non-maskable hardware and interrupt related noise is allowed.
According to the description made by the maintainers of the tool, the latter talso allows noise tracer configurations and collecting the output of the plotter. In summary, rtla hwnoise offers functionality similar to osnoise (operating system noise) while showing only non-maskable interrupts (NMI) and hardware-related noise.
In principle, the hardware noise should be zero Linux. However, It turns out that this is not always the case. In the operation of the operating system, one can face two main sources of noise.
Noise from operating system operations and noise related to hardware. In the context of high performance computing (HPC), for example, operating system noise (osnoise) refers to the interference experienced by an application due to activities within the operating system. In the context of Linux, NMI, IRQ, SoftIRQ, and any other system thread can cause system noise. In which case,
On Linux, Although there may be others Four main execution contexts can interfere with a workload: non-maskable interrupts (NMIs), maskable interrupts (IRQs), softirqs (deferred IRQ activities), and threads. In addition to these system-related noises, hardware-related loads can also cause noise, for example via SMI.
It is in this last case that the rtla hwnoise tool was designed. To better understand how the hardware-related noise measurement and monitoring tool works, it is recommended to turn to the Linux osnoise tool, since it is derived from it.
On Linux, there are two types of tools for measuring operating system noise: one based on workload and one based on tracking. Workload-based tools typically run microbenchmarks with a known duration and measure the difference between the planned duration of the microbenchmark and the actual time it takes to process it. While they are good at defining the amount of operating system noise a workload might experience, workload-based tools cannot identify the root causes of operating system noise.
Trace-based methods take advantage of the Linux kernel's tracing capabilities to identify the cause of operating system noise. However, these trace-based methods do not take into account how noise is perceived by workloads. And that is why the osnoise tool was designed. It takes full advantage of workload-based and trace-based methods, showing the root causes of operating system noise and taking into account how noise is perceived by the workload.
Next to osnoise, we have the rtla osnoise tool, which is an interface to the osnoise plotter. the tracker osnoise runs a loop in the kernel measuring the available time. It does this with preference, softirq and IRQ enabled, allowing all sources of noise while running.
With rtla hwnoise, users and developers who care about every microsecond stolen by bogus instructions sent by hardware will be able to accurately measure those noises and make decisions accordingly, knowing that for real-time operations, every microsecond gained by the processor has value. .
Source: https://git.kernel.org