Good news: the October 2018 Update for Windows 10 features the highly anticipated fixes for Spectre and Meltdown. Bad news: these fixes can have a significant performance it, with some websites reporting a 20-30% hit. Thankfully, though, Microsoft is looking into optimizing these new features in the next Windows 10 update.
Yes, we have enabled retpoline by default in our 19H1 flights along with what we call "import optimization" to further reduce perf impact due to indirect calls in kernel-mode. Combined, these reduce the perf impact of Spectre v2 mitigations to noise-level for most scenarios. https://t.co/CPlYeryV9K
— Mehmet Iyigun (@mamyun) October 18, 2018
According to Mehmet Iyigun, Microsoft has enabled retpoline by default in its upcoming Windows 10 19H1 update that will go live in early 2019. As Iyigun noted, retpoline reduces performance impact due to indirect calls in kernel-mode, and the overall performance impact of the Spectre v2 mitigations will be reduced to noise-level for most scenarios.
So yeah, most Windows 10 users will notice a performance hit with the October 2018 Update due to these first fixes for Spectre and Meltdown. Let’s hope that Microsoft will release the 19H1 update to the public sooner than later!