Back at its Architecture Day 2021 event, when Intel shared the core design details of its Alder Lake CPU architecture, the firm stated that Windows 11 was optimized in a way to best take advantage of the Alder Lake's Performance Hybrid architecture and the new Thread Director technology that helps Windows 11 task scheduling. Early testing confirmed this was indeed the case, and even first-gen hybrid products like Lakefield benefitted as well.
Since then, however, Linux too has taken up the mantle to optimize the hybrid architecture and in August earlier this year, the first major patch was sent in related to asymmetric packing. And it is not just on paper that Linux sounds to be doing a better job since benchmarks sort of confirm that Windows 11 has lost its performance lead over time as more and more optimizations land in the Linux kernel. Not only that, but several gaming performance-related issues had also been bringing down Windows 11 22H2. Microsoft claims it was able to fix these with the latest Windows update.
Moving on, a new set of patches has been submitted as RFC (request for comment) by Intel Linux engineer Ricardo Neri is the extension of a previous patchwork sent back in August. These ones too aim to improve the performance of hybrid CPUs like Alder Lake, Raptor Lake, and also upcoming 14th Gen Meteor Lake when running Linux. This time, IPC classes for balancing workloads are being added alongside optimizations to Intel's Thread Director, which should result in overall better task scheduling and performance improvement.
Neri has explained:
On hybrid processors, the microarchitectural properties of the different types of CPUs cause them to have different instruction-per-cycle (IPC) capabilities. IPC can be higher on some CPUs for advanced instructions
The load balancer can discover the use of advanced instructions and prefer CPUs with higher IPC for tasks running those instructions.
This patchset introduces the concept of classes of tasks, proposes the interfaces that hardware needs to implement and proposes changes to the load balancer to leverage this extra information in combination with asymmetric packing.
The V2 of the above patch, that was released yesterday, brings more additions and further optimizations to to IPCC classing and implements cleanups and reworks.
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