Microsoft Finally Enables Retpolines For Windows 10 Version 1809, Windows Server 2019

Written by Michael Larabel in Microsoft on 1 March 2019 at 05:37 PM EST. 5 Comments
While Linux has supported Retpolines "return trampolines" for over one year as part of its Spectre mitigations, Microsoft is finally rolling out a similar implementation as a stable Windows 10 v1809 update today and for Windows Server 2019.

Microsoft has been working on a Retpolines implementation for Windows to help recover some of the performance losses encountered by their original Spectre Variant Two implementation. That Retpoline implementation has been found within recent Windows Insider Preview Builds while finally today as an update to Windows 10, Version 1809 and for Windows Server 2019 they've rolled it out with today's updates.

Microsoft blogged back in December when outlining their Retpolines work, "When all relevant kernel-mode binaries are compiled with retpoline, we’ve measured ~25% speedup in Office app launch times and up to 1.5-2x improved throughput in the Diskspd (storage) and NTttcp (networking) benchmarks on Broadwell CPUs in our lab."

That aforelinked blog post is quite interesting for those Windows users and if curious about the technical Retpolines implementation.

Details on today's Windows updates with Retpolines via KB4482887.

Just mentioning this here for readers who may be keeping Windows installations around. And, of course, to share that this piqued my interest enough that I'll be doing some fresh Windows vs. Linux Spectre/Meltdown mitigation tests... If any premium members have any interesting test requests as part of that, let me know ASAP. It will certainly be interesting to see how the mitigated costs compare now between Windows and Linux thanks to Microsoft finally rolling out Retpolines outside of their Insider Preview realm.
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Michael Larabel is the principal author of and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 20,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and automated benchmarking software. He can be followed via Twitter, LinkedIn, or contacted via

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