Windows 11 VMs on Linux to perform faster on Intel's 12th, 13th, 14th, 15th Gen CPUs

Back in October of last year, Microsoft, perhaps a bit surprisingly, published a guide urging Windows users to try out Linux via WSL.

If you are on the other end of the spectrum, already on Linux, and would like to try Windows via VM, and you happen to be running an Intel processor, 12th Gen or newer, there is good news for you. That's because Intel has been working to integrate Thread Director optimizations such that Windows guests on Linux hosts can perform better. These optimizations (spotted by Phoronix) can net up to a 14+% performance bump. The patch was tested on the 13th Gen Core i9-13900K.

The patch notes also says that additional support from Intel HWP (Hardware P-States / Performance States) and CPPC (Collaborative Processor Performance Control) is also necessary

... the purpose of this patch set is to enable the ITD-based scheduling logic in Guest so that Guest can better schedule Guest tasks on Intel hybrid platforms.

 

Currently, ITD is necessary for Windows VMs. Based on ITD virtualization support, the Windows 11 Guest could have significant performance improvement (for example, on i9-13900K, up to 14%+ improvement on 3DMARK).

 

Our ITD virtualization is not bound to VMs' hybrid topology or vCPUs' CPU affinity. However, in our practice, the ITD scheduling optimization for win11 VMs works best when combined with hybrid topology and CPU affinity (this is related to the specific implementation of Win11 scheduling).

 

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To enable ITD related scheduling optimization in Win11 VM, some other thermal related support is also needed (HWP, CPPC), but we could emulate it with dummy value in the VMM

In case you may not be aware, Intel Thread Director (ITD) is the technology that helps Windows schedule tasks optimally across appropriate P-cores and E-cores on its Performance Hybrid architecture CPUs, ie, 12th Gen and newer.

Outside of VMs, it is noteworthy that Thread Director optimizations have already been a part of the Linux kernel for some time now.

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