Intel thread director linux

Linux equivalent of Thread Director?

The 12th Generation Intel chips are rumoured to have «Efficient» and «Performance» cores. Apparently Microsoft’s Thread Director, in Windows 11, takes advantage of them. What will be the Linux equivalent? When can we expect it to be released? Read about Thread Director here: https://www.digitaltrends.com/computing/how-intel-thread-director-marries-alder-lake-windows-11/ There is no way that I’m going back to Windoze. But I do want to use the latest hardware.

1 Answer 1

1. Thread Director is a feature of Intel CPUs, not Microsoft Windows’
2. Thread Director support still has to be implemented in the OS and currently only Windows 11 supposedly has it: https://www.phoronix.com/scan.php?page=news_item&px=Linux-5.15-Scheduler
3. Even without this support, Linux will still work just fine with Alder Lake CPUs, albeit not as efficiently as it could.
4. Intel hasn’t yet announced when ADL CPUs get officially released, so it’s possible that Linux 5.16 will support Thread Director. This kernel version will likely be released in December 2021 or January 2022.

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Intel’s Thread Director Coming to Linux 5.18 to Fix Alder Lake Performance Issues

The upcoming Linux version 5.18 will improve the performance of Intel’s latest 12th Generation Core ‘Alder Lake’ processors, as it will come with the company’s new drivers that optimize usage of (P)erformance and (E)fficiency cores. These CPUs rank as many of the best CPUs for gaming and other tasks, but at present, they work best on Windows 11 PCs, which is typically unheard of when compared to performance in Linux.

Intel first published patches that enable HFI on Linux late last year, but the first version of Linux to integrate these new drivers will be 5.18, which is due in Spring 2022. The new version of Linux will assign background and less important workloads to energy-efficient cores, thus improving the performance of Intel’s newest CPUs, reports Phoronix. Unfortunately, the release date for Linux 5.18 is unknown.

Unlike Windows 11, Linux currently doesn’t have the appropriate support for Intel’s Thread Director technology that uses the Enhanced Hardware Feedback Interface (HFI). HFI allows the OS to properly allocate threads to the high-performance Golden Cove and energy-efficient Gracemont cores, which is why Intel’s hybrid Alder Lake CPUs perform better under Windows.

Without HFI support, the Linux kernel makes decisions on whether to use P or E cores using Intel’s ITMT/Turbo Boost Max 3.0 driver that relies on the information exposed by the firmware. That’s why in many cases it prefers the fastest cores with the highest frequency (i.e., Golden Cove cores) and does not use Gracemont cores even when possible, which leads to their underutilization.

By contrast, Intel’s Thread Director communicates actual numeric performance and numeric power efficiency values of each CPU core in a 0 – 255 range to the OS. If either the performance or energy efficiency capability of a CPU core is 0, the hardware dynamically adapts to the current instruction mix and recommends not assigning any tasks on this core for performance, energy efficiency, or thermal reasons.

Significant changes to scheduling in an operating system can have wide-ranging effects, and it can take time to work out all the kinks. Intel’s Thread Director can help provide feedback to the OS on where threads will run best, but there’s rarely a single ‘best’ answer and tuning can take time. We’ll be to see just how much benefit the new scheduler brings to Alder Lake chips in the next couple of months.

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Intel Thread Director Is Headed To Linux For A Major Boost In Alder Lake Performance

Hetereogeneous computing is nothing new, of course, but typically it has been one type of CPU core and one type of GPU, along with media processing blocks and other small functional units — at least on desktop and notebooks systems. Intel’s Alder Lake CPUs are the first x86-64 processors to embrace a hybrid paradigm with two separate CPU architectures on the same die.

These two separate CPU architectures have different strengths and capabilities. The Golden Cove «performance cores» (or P-cores) feature Intel’s latest high-performance desktop CPU architecture, and they are blisteringly fast. Meanwhile, the Gracemont «efficiency cores» (or E-cores) are so small that four of them, along with 2MB of shared L2 cache, can nearly fit in the same space as a single Golden Cove core. They’re slower than the Golden Cove cores, but also much more efficient, at least in theory.

The idea is that background tasks and light workloads can be run on the E-cores, saving power, while latency-sensitive and compute-intensive tasks can be run on the faster P-cores. The benefits of this may not have been exactly as clear as Intel would have liked on Windows, but they were even less visible on Linux. That’s because Linux isn’t aware of the unusual configuration of Alder Lake CPUs.

Well, that’s changing in Linux 5.18, slated for release this spring. Linux 5.18 is bringing support for the Intel Enhanced Hardware Feedback Interface, or EHFI. Kernel support for reading EHFI data will allow the operating system to more intelligently schedule tasks on the CPU’s logical cores, which will allow the P-cores and E-cores to be used as they were intended. This is essentially the crux of Intel’s «Thread Director,» which is an intelligent, low-latency hardware-assisted scheduler.

This news comes courtesy of Phoronix, which reports that Intel’s EHFI kernel code has been merged into the «linux-next» branch of linux-pm, the Linux power management subsystem. That apparently means it will be in the next kernel cycle, 5.18. The site goes on to say that Linux 5.18 stable should be available in late May or thereabouts.

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Intel releases patch for Alder Lake’s Thread Director Linux support to increase performance and energy efficiency

Intel launched several patches for the Linux series of operating systems to aid in increasing Alder Lake’s performance through the P and E cores, or Performance and Efficiency cores.

Linux OS to receive support for Intel’s Alder Lake Golden Cove and Gracemont performance and efficiency cores through upcoming patches

With the release of Intel’s 12th Gen Core Alder Lake series of CPUs, it was discovered that performance for the new CPUs was more efficient in Microsoft Windows 11 than in the Linux operating system. This is due to Linux not having adequate support for Intel’s Thread Director technology that allows for the operating system to access high-performing Golden Cove cores and the energy-efficient Gracemont cores properly. Intel’s Thread Director is created from the Enhanced Hardware Feedback Interface or HFI.

Intel Granite Rapids-D CPUs Gets Spotted For the First Time, Will Replace Ice Lake-D

Website Phoronix reports that the current firmware in Linux uses an algorithm to plan which of the Performance or Efficiency cores utilized by the ITMT/Turbo Boost Max 3.0 driver are accessed at the time. In turn, due to the nature of Linux choosing to lean more towards higher performance, such as what is found in Golden Cove’s clock speed, while at the same time lessening the utilization of the energy-efficient Gracemont cores.

Enter the Intel Hardware Feedback Interface—a table created by the HFI to help provide information for both the performance and energy efficiency of the computer’s processor. The HFI table, working together with the OS and the hardware, is constantly updated depending on any changes in the operating conditions or any actions from external factors at the time. An example of this process is the thermal limits reached by the operating system or changes made by the thermal design power.

Intel explains the new patch in further detail.

In short, Intel’s HFI calculates the power efficiency and performance capability of the processor, giving it a numerical value to the core (0 — 255), and communicates that information to the operating system. This real-time communication from the HFI allows for the hardware to adapt to the current capabilities of the system and communicate to the operating system to make recommendations on what to limit at the given time, such as minimizing any scheduled tasks that would affect the energy efficiency, performance levels, or temperature of the system.

Currently, the newest patch series is in the revision stages, and no word yet has been made whether the patches will be part of the upcoming Linux 5.17 update, or released at a further date sometime this year.

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